ACS Publications. Most Trusted. Most Cited. Most Read
Unveiling the Future of Li-Ion Batteries: Real-Time Insights into the Synthesis of Advanced Layered Cathode Materials
My Activity

Figure 1Loading Img
  • Open Access
Perspective

Unveiling the Future of Li-Ion Batteries: Real-Time Insights into the Synthesis of Advanced Layered Cathode Materials
Click to copy article linkArticle link copied!

Open PDF

ACS Energy Letters

Cite this: ACS Energy Lett. 2024, 9, 9, 4255–4264
Click to copy citationCitation copied!
https://doi.org/10.1021/acsenergylett.4c01540
Published August 2, 2024

Copyright © 2024 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY-NC-ND 4.0 .

Abstract

Click to copy section linkSection link copied!

Prompted by the increasing demand for high-energy Li-ion batteries (LIBs) in electric vehicles (EVs), the development of advanced layered cathode materials has attracted significant attention in recent decades. Advances in in situ and in operando characterization techniques have not only led to the successful commercialization of these materials but have also opened up new horizons in terms of the development of cathodes exhibiting enhanced energy and cycle stability. This Perspective highlights recent advances in in situ monitoring techniques during the synthesis of layered cathode materials. While previous reports have focused on the reaction mechanisms during charging/discharging, this Perspective aims to reveal the complex relationships between phase transitions and microstructural evolution during synthesis and their impacts on electrochemical performance. Furthermore, we address strategies that aid understanding of the solid-state synthesis mechanisms of layered cathode materials and offer an insightful guide for the synthesis of defect-free layered oxide cathode materials.

This publication is licensed under

CC-BY-NC-ND 4.0 .
  • cc licence
  • by licence
  • nc licence
  • nd licence
Copyright © 2024 The Authors. Published by American Chemical Society

Special Issue

Published as part of ACS Energy Letters virtual special issue “Celebrating 10 Years of the Collaborative Innovation Center of Chemistry for Energy Materials (iChEM)”.

Lithium-ion batteries (LIBs) with layered oxide cathodes have seen widespread success in electric vehicles (EVs) and large-scale energy storage systems (ESSs) owing to their high energy and cycle stability. The rising demand for higher-energy LIBs has driven the development of advanced, cost-effective cathode materials with high energy density. This development is crucial for improving LIB performance, influencing costs, energy density, cycle stability, and safety. Since the commercialization of LiCoO2 in the 1990s, there has been a consistent push to develop nickel (Ni)-based and manganese (Mn)-based oxide derivatives to increase the energy density of LIB cells at lower costs. (1,2) Currently, LIBs have nearly reached an energy density of 300 Wh kg–1, enabling EVs to achieve driving ranges of 400 to 600 km. (3) This milestone is primarily due to continuous improvements in electrode materials, particularly in boosting the energy density and cost-efficiency of cathode materials. However, major challenges remain in the further commercial development of layered cathode materials, particularly concerning cell lifetime and safety.
Early efforts to fully utilize Li in the layered structure, thus achieving a large reversible capacity (>200 mAh g–1), involved doping LiCoO2 (LCO) with Ni, Mn, and aluminum (Al). This led to the development of compounds such as LiNixCoyMn1-x-yO2 (NCM) and LiNixCoyAl1-x-yO2 (NCA), in which cobalt (Co) was replaced with other transition metals (TMs). (4) Although the theoretical capacity of LCO is 275 mAh g–1, its practical capacity is limited to ∼150 mAh g–1 due to a structural transition to an inactive phase after extracting more than 0.54 Li from the layered structure. Recent studies have introduced doped or coated forms of LCO with a reversible capacity of over 200 mAh g–1, but the use of expensive cobalt remains a significant hurdle. (5) Current research on Co-free, next-generation layered cathode materials has focused on two main types: Ni-rich layered materials and Mn-based overlithiated layered oxides (OLOs). The electrochemical reaction mechanisms differ, with only Ni metal redox used in the former and both TM and oxygen redox employed in the latter. Similar methods have been employed to enhance electrochemical performance, including doping with heterocations such as Ta, W, Mo, Zr, Ti, and Nb to stabilize the crystal structure of the layered phases. (6) This significantly enhances cycle stability but at the expense of reversible capacity. Particle surface coatings are also commonly used to protect unstable surfaces, reducing metal dissolution and gas evolution during charge/discharge cycles. (7) More recently, improvements in the cycle stability of layered cathode materials have been achieved through the development of core–shell structures and the creation of TM concentration gradients at the secondary-particle scale. (8) These techniques have led to more stable electrochemical performances, substantially extending the use of layered cathode materials in EV and ESS applications.
Technical advances in in situ characterization tools employing X-ray, electron, neutron, and optical analysis techniques have significantly advanced the development of cathode materials with high energy density, cycle stability, and safety. (9,10) The unusually large capacity from OLO was explained using in situ and in operando synchrotron X-ray analyses, including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), resonance inelastic X-ray scattering (RIXS), and pair distribution function (PDF), which illuminated the role of oxygen redox chemistry. (11) Additionally, the multiscale degradation mechanisms of layered oxide cathodes during repeated charge and discharge have been characterized via in situ synchrotron X-ray/neutron diffraction and electron microscopy analyses, providing insights that pave the way toward stabilizing the crystal and surface structures. (10) Lattice oxygen release, followed by phase transitions from layered to spinel and rock-salt structures at high temperatures, has been characterized through in situ high-temperature X-ray and neutron diffraction techniques, revealing the thermal stability of charged cathode materials. (12) Although advances in in situ and in operando techniques have yielded critical insights that aid the development of better cathode materials, most previous reports have focused on the reaction mechanisms during charging and discharging and the thermal stability of charged cathodes. Few studies have addressed in situ characterization during the synthesis of layered cathode materials, which is crucial for developing better materials.
This Perspective focuses on recent advancements in in situ monitoring techniques during the synthesis of advanced layered cathode materials for LIBs and envisions future advancements. First, we introduce various analytical efforts that unveil the intricate correlations between phase transitions, microstructural evolution during synthesis, and electrochemical performances. Next, we identify key analysis parameters from each characterization technique that aid in designing better cathode materials for LIBs. Additionally, we propose a novel synthetic strategy: creating advanced cathode materials by regulating the formation of atomic- and nanoscale defects. We hope this Perspective enriches the understanding of the solid-state synthesis of layered oxide cathode materials and serves as a useful guide for synthesizing defect-free layered oxide cathode materials.

Atomic-Scale Characterization of Layered Cathode Materials Using Diffraction Techniques

Click to copy section linkSection link copied!

Tracking crystal structural changes within layered cathode materials synthesized using various approaches has been conducted through extensive ex situ diffraction analyses, combined with Rietveld refinements of powder diffraction patterns. (13) The diffraction technique, a long-established method for identifying crystal structures, commonly utilizes XRD with X-rays sourced from both laboratory diffractometers and synchrotrons. Synchrotron X-ray beams, characterized by high intensity and wide energy tunability, enable time-resolved in situ investigations that are crucial due to the nonequilibrium and complex nature of synthesis processes. (9,10) Diffraction data can be readily obtained in just a few minutes, offering comprehensive insights into phase transitions, atomic ordering, bond lengths, crystallite sizes, and microstrains throughout the synthesis process. Recent advances in laboratory X-ray diffractometers now enable the acquisition of structural information during synthesis. (13,14) However, these instruments frequently encounter data distortions due to reflection geometry, which can lead to peak shifts and a loss of peak intensity at low angles, often resulting from sample contraction or expansion at high temperatures. Moreover, these systems require longer data acquisition times, necessitating the careful design of experimental procedures.
Tremendous efforts have been made to examine the impact of key parameters on the synthesis of layered cathode materials by varying precursor types, stoichiometry, temperature, atmosphere, procedures (such as heating and cooling rates, and aging time), and dopants. (15,16) In situ high-temperature XRD (HT-XRD) studies of layered cathode materials during calcination or sintering have primarily focused on characterizing solid-state reaction mechanisms, encompassing heating, aging, and cooling. (17,18) The overall synthesis process can be divided into four stages based on temperature: Stage I is from room temperature (RT) to 500 °C, Stage II is above 500 °C, Stage III is aging at the reaction temperature, and Stage IV is cooling (Scheme 1). In Stage I, the Li and TM precursors decompose and react with each other, forming partially lithiated intermediate phases. During this stage, dynamic phase transformations occur, and the phase fractions (by weight) from the precursor mixtures to the intermediate phases provide insights into the reaction pathways for designing high-performance layered cathode materials. Figure 1a shows the change in phase fractions of a precursor mixture of LiOH·H2O and Ni0.6Co0.2Mn0.2(OH)2 during heating, derived from Rietveld refinement of in situ synchrotron HT-XRD patterns. (19) Dehydration of LiOH·H2O was observed around 100 °C, and a lithiated intermediate phase with a disordered rock-salt structure began to form above 200 °C. The phase fraction of this lithiated phase continued to increase during heating up to 500 °C, with compensation from the Li and TM precursors. However, significant Li/TM intermixing was noted, indicating that the rock-salt structure was still maintained.

Scheme 1

Scheme 1. Conventional Synthesis Protocol of Layered Cathode Materials and the Corresponding Structural Changes at Each Stage

Figure 1

Figure 1. (a) The weight fraction of the precursor mixture for the synthesis of LiNi0.6Co0.2Mn0.2O2 obtained from Rietveld refinement of in situ HT-XRD data. Reproduced with permission from ref (19) Copyright 2021 John Wiley and Sons. (b) The c/a ratio in the intermediate structures of Lix (Co0.2Ni0.8)1–xO2 and LixNi2–xO2. Reproduced with permission from ref (20) Copyright 2020 American Chemical Society. (c) Ni–O and Li–O bond length changes during synthesis for LiNi0.8Co0.2O2 under O2 flow. Reproduced with permission from ref (27) Copyright 2017 John Wiley and Sons. (d) In situ PDF patterns during the synthesis of LiNi0.77Mn0.13Co0.1O2. Reproduced with permission from ref (28) Copyright 2018 American Chemical Society. (e) Li SOFs as a function of temperature upon heating of LiNixMn1–xO2 (x = 0, 0.9, 0.75). Reproduced with permission from ref (21) Copyright 2023 IUCR Journals. (f) Domain sizes derived from Rietveld refinement of in situ HT-XRD patterns during the synthesis of NCM811. Reproduced with permission from ref (24) Copyright 2022 John Wiley and Sons.

The kinetic pathways for the synthesis of layered cathode materials vary considerably depending on metal composition (such as Ni, Mn, Co, and Al), (20−22) precursor types (like hydroxides and carbonates), (14,23) and synthetic procedures (such as heating rate, preaging steps, and cooling), (13,14,24) resulting in different intermediate phases during the early heating stage. Preferential oxidation of Co and Mn over Ni during this stage facilitates the formation of a spinel (Fd3̅m) phase in the synthesis of low-Ni layered cathode materials, specifically LiNixMnyCo1-x-yO2 (where x < 0.6) and OLO, while a rock-salt (Fm3̅m) phase forms when x ≥ 0.6. Additionally, using Li and TM carbonate precursors increases the reaction temperature required to form the layered structure due to their higher melting points compared to hydroxide forms. (1,20) Therefore, hydroxide precursors are typically preferred for synthesizing Ni-rich layered cathode materials with Ni contents of x ≥ 0.8. Several studies support this claim, indicating that using Li and TM carbonate precursors can lead to reaction heterogeneity during heating due to the formation of Li2CO3, resulting in poorer electrochemical performance. (25) In contrast, using hydroxide precursors with a carefully regulated synthetic procedure and preaging steps can significantly affect the lithiation of intermediate phases, leading to superior electrochemical performance. (13,14) The electrochemical performance of layered cathode materials is strongly influenced by their reaction pathway during synthesis, making it crucial to characterize the phase fraction during the early stages of synthesis using diffraction analysis.

Real-time diffraction analysis during solid-state synthesis provides detailed structural information, such as lattice parameters, bond lengths (TM–O and Li–O), and site occupancies, which can guide the synthesis of advanced layered cathode materials.

Real-time diffraction analysis during solid-state synthesis provides detailed structural information, such as lattice parameters, bond lengths (TM–O and Li–O), and site occupancies, which can guide the synthesis of advanced layered cathode materials. Once the lithiated intermediate phase forms in Stage I, further lithiation and Li-TM ordering occur as the temperature increases, inducing significant changes in lattice parameters and TM–O bond lengths. During Stage I, both lattice parameters and TM–O bond lengths contract due to the oxidation of transition metals and lithiation into the crystalline lattice. However, in Stage II, lattice parameters generally increase, attributed to Li-TM ordering and thermal expansion of the crystalline lattice. The degree of Li-TM ordering can be evaluated using the c/a ratio, which is typically greater than 4.899 for the R3̅m layered structure, as shown in Figure 1b. (20) Analyzing the temperature dependence of the c/a ratio helps determine the optimal temperature for synthesizing layered cathode materials. Additionally, tracking the c/a ratio during high-temperature aging guides the design of the healing process for synthesizing single-crystalline layered materials with enhanced electrochemical performance. (26) Monitoring Li–O and TM–O bond lengths (or Li and TM slab distances) during heating, derived from Rietveld refinement of diffraction patterns, also guides the optimal synthesis temperature. Figure 1c shows the TM–O bond length changes during the synthesis of LiNi0.8Co0.2O2, indicating that a layered structure with highly oxidized Ni is achieved at 800 °C. (27) Above 800 °C, TM–O bond lengths tend to increase, mainly due to increased Li–Ni intermixing and the formation of rock-salt phases, which compromise electrochemical performance. Temperature-resolved X-ray PDF patterns obtained from total scattering data during the synthesis of Ni-rich layered cathode materials also allow monitoring of changes in TM–O bond lengths. (28) Zhang et al. examined the peak position and intensity of TM–O and TM–TM bonds, as presented in Figure 1d, revealing a lithiation and Li-TM ordering mechanism during the heating stage. However, the local structure of TM–O and TM–TM is very complex, and the scattering factors of Ni, Mn, and Co to X-rays are similar, so the oxidation states of Ni, Co, and Mn cannot be distinguished by PDF.
Lithiation into the crystalline lattice and Li-TM disordering have been evaluated by examining the change in the I(003)/I(104) ratio in XRD patterns during the heating process, a widely used indicator for the degree of Li–Ni disorder. (28−31) This ratio typically increases during heating due to the cationic ordering between Li and TM, allowing the determination of the onset temperature or major temperature range for this ordering. This information guides the determination of synthesis temperature and the design of synthesis procedures. Furthermore, tracking this ratio during aging and cooling has helped determine appropriate aging times and cooling rates. Many approaches have been used to quantify Li and Li-TM disorder in the crystal structure using in situ HT XRD. (31−33) However, the exact amount of Li in the crystal structure cannot be determined through X-ray diffraction due to the low scattering of Li, while the TM occupancies in the Li site (3a) and TM site (3b) can be determined. A recent study by Goonetilleke et al. successfully quantified the site occupancy fraction (SOF) of Li in the 3a and 3b sites using in situ HT-neutron diffraction analysis, as illustrated in Figure 1e. (21) They demonstrated that the onset temperature for lithiation and subsequent Li/TM ordering increases as the Mn content increases in layered materials, requiring high temperatures for the synthesis of high-performance Mn-containing layered materials. Additionally, they quantified Li loss during high-temperature aging, necessitating excess Li for synthesizing these materials. Since neutrons directly interact with atomic nuclei, the coherent scattering length and volume do not depend on the atomic number, enabling the investigation of Li SOF in the crystal structure. Furthermore, quantitative discussions on neighboring elements in the periodic table such as Mn, Co, and Ni are comparably easier with neutron diffraction than with XRD. However, the small number of neutron facilities worldwide, limited beamtime, and low neutron flux compared to that of synchrotron X-rays are significant hurdles for real-time measurement during the synthesis of layered cathode materials.
Peak width analysis from in situ HT diffraction patterns has been widely employed for evaluating crystallite size and microstrain during the synthesis stage. The most common indicator for evaluating the crystallinity of layered cathode materials is the full-width at half-maximum (fwhm) of the (003) peak of the R3̅m structure, where a decrease in the fwhm indicates increasing crystallite size and decreasing microstrain. (19,22) By monitoring the change in fwhm during heating and aging, the primary particle growth of the layered structure can be observed, which is critical for regulating lithiation during heating and the average crystallite size of layered cathode materials. (24,29,32) Figure 1f shows the change in domain size of each phase from precursors to layered phases during the synthesis of LiNi0.8Co0.1Mn0.1O2 (NCM811), revealing that the growth of the layered phase starts from 600 °C. (24) Wolfman et al. claimed that pretreatment of the precursor at 500 °C slowed the ripening of the rock salt primary particles, enhancing Li incorporation and converting the sample to the layered structure. In the analysis of domain size in this study, an anisotropic size model was applied to analyze the plate-like M(OH)2 particles. (34)
In addition to the analysis of crystallite size from peak broadening, microstrain also affects peak broadening, especially at higher 2θ angles. Size-induced broadening and strain-induced broadening are independent of each other, and the broadening can be interpreted as the sum of both factors. When analyzing broadening, the instrumental broadening should be precalibrated using standard reference materials such as LaB6. Gim et al. conducted in situ HT XRD analysis during the synthesis of LCO, revealing that LCO synthesized at 850 °C with the lowest microstrain exhibited enhanced capacity and cycle performance. (35) Crystallite size and microstrain can be obtained from in situ HT diffraction pattern analysis; however, reliable data on crystallite size is limited up to ∼200 nm. Consequently, microstructure and morphology analysis are mostly carried out using electron microscopy techniques, which will be discussed in the following section.

Microstructural and Morphological Characterization Using Electron Microscopy and Small-Angle Scattering Techniques

Click to copy section linkSection link copied!

In situ electron microscopy during the synthesis of layered cathode materials enables real-time visualization of dynamic processes, including the evolution of microstructural features and defect formation at nanoto-atomic scales. In situ diffraction analysis yields average crystallographic information on the bulk structure but does not provide detailed insights into the initiation and propagation of spatially inhomogeneous reactions at the precursor interfaces during synthesis. This limitation significantly hampers our understanding of how defects form and the synthetic pathways of layered cathode materials. In situ transmission electron microscopy (TEM) and scanning electron microscopy (SEM) afford crucial insights into the morphological changes, crystal growth, and defect distributions at the microstructural level during synthesis. These observations are essential for optimizing the electrochemical properties of layered cathode materials and enhancing their industrial applicability and long-term stability. Therefore, employing in situ TEM and SEM during layered cathode synthesis is crucial for advancing our understanding of these complex materials and their formation mechanisms.
Studies using in situ SEM and TEM during synthesis primarily focus on analyzing phase and morphological changes related to precursor types, atmosphere, and variations in the calcination or sintering processes. These studies complement the insights gained from in situ XRD, which has traditionally concentrated on characterizing solid-state reaction mechanisms involving heating, aging, and cooling. Tang et al. investigated the morphological evolution of NCM811 cathode materials during sintering from 300 to 1080 °C using in situ SEM with a unique heater. (36) A homogeneous mixture of a spherical Ni0.8Co0.1Mn0.1(OH)2 precursor and Li source (LiOH) was subjected to a high-temperature solid-state synthetic process within the SEM, allowing for real-time monitoring of morphological transformations. NCM811 synthesis proceeds via several stages: dehydration of raw materials, oxidation, and chemical combination, each significantly reducing particle size. As the temperature increases, the particle morphology shifts from flaky to brick-shaped (Figure 2a). Particularly at temperatures approaching 1000 °C, the formation of Ni nanoparticles marks a transition toward a rock-salt-like structure. Thus, careful control of the sintering temperature is essential to preserve the desired transformation from flake to brick-shaped morphology, minimizing particle size reduction and preventing a structural shift to a rock-salt structure. This is crucial for producing NCM cathode materials with optimal electrochemical performance.

Figure 2

Figure 2. (a) In situ HT SEM images at 300, 750, 940, and 1000 °C during the synthesis of NCM811. Reproduced with permission from ref (36) Copyright 2022 Elsevier. (b) In situ TEM images and negative intensity changes in the core–shell regions during the synthesis of LiNi0.6Co0.2Mn0.2O2. Reproduced with permission from ref (14) Copyright 2022 Springer Nature. (c) Wide-angle X-ray scattering data of Ni1/3Mn1/3Co1/3(OH)2 coprecipitated in a pH 10.6 solution. (d) The effective radius, R, of Ni1/3Mn1/3Co1/3(OH)2 coprecipitated in pH 10.6 solution (Sample A) and pH 11.4 solution (Sample B). Reproduced with permission from ref (38) Copyright 2018 The Electrochemical Society. (e) In situ SANS patterns during the synthesis of LiNi0.92Co0.03Mn0.05O2 without and with preaging at 250 °C for 6 h. Reproduced with permission from ref (13) Copyright 2024 John Wiley and Sons.

Park et al. performed real-time reaction monitoring using in situ environmental heating TEM, simulating the real-world synthetic conditions of Ni-rich layered oxides. (14) Both nanoreactor heating and the oxygen environment were controlled. Upon heating to 300 °C, significant particle changes were observed in sequential TEM images, as presented in Figure 2b. At around 240 °C, boundary development within secondary particles commenced, evolving into core–shell particles by 300 °C. The shell became denser due to a relative mass gain commencing at 240 °C, while the core experienced mass loss, likely due to dehydration, suggesting that the local particle density decreased. The similarity in the onset temperatures for synthetic lithiation and self-dehydration suggests that lithium access to particle cores was kinetically hindered, triggering core self-decomposition and further densification. These observations from in situ TEM indicate that core–shell formation reflects kinetic competition between various reactions influenced by local lithium accessibility. This study provides valuable insights: defect engineering aids material synthesis by strategically controlling the proportions of intermediate phases, accelerating the development of high-energy, Ni-rich layered electrodes for LIBs, and enhancing both performance and long-term stability.
Characterization of microstructural and morphological changes via in situ electron microscopy greatly aids optimization of the synthetic parameters for layered cathode materials. However, the field of view of real-time analysis is limited to a local area of a single secondary particle, and the observed changes in particle morphology and structure during synthesis are qualitative. Small-angle scattering techniques, which analyze the scattered X-ray or neutron beams at small angles (typically 0.1 to 10 degrees), afford global information on density fluctuations at the nano- to microscales, including the sizes, shapes, and distributions of nanoparticles or pores. (37) Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) with different beam sources can be employed for quantifying the nanoscale defects in layered cathode materials, based on the characteristics of each beam source. For example, X-rays interact with the electron cloud surrounding atoms, making SAXS more sensitive to heavier elements with more electrons. In contrast, neutrons interact with atomic nuclei through nuclear forces, which is advantageous for analyzing materials composed of light elements such as H, Li, and O, and provides high contrast for metal ions with similar atomic numbers and isotopes. Feng et al. used in situ ultrasmall-angle X-ray scattering (USAXS) to investigate the growth mechanism of TM(OH)2 precursors at pH values of 10.6 and 11.4 during coprecipitation syntheses (Figure 2c and 2d). (38) In the early stage of coprecipitation, a slower growth rate of primary particles with small effective radii was observed at pH 11.4 compared to 10.6, attributable to the growth of many nuclei at the higher pH. The thin-disk-like TM(OH)2 size attained 500 nm over 3 h of reaction time.
A recent study by Song et al. used in situ HT SANS to investigate pore formation and growth during the synthesis of Ni-rich layered cathode materials. (13) Neutrons can penetrate deeper into materials without damaging the sample compared to X-rays, which makes SANS more suitable for studying bulk properties and samples in HT environments. They quantified the specific pore volume (cm3 g–1) and the mean pore radius (Å) and found that the decomposition of TM(OH)2 was directly attributable to the formation of micropores that served as seeds for the growth of meso- or macro-pores via coalescence. Furthermore, a new synthetic strategy featuring preaging at a low temperature of 250 °C yielded highly lithiated intermediates with uniform pore distributions and enhanced cycle performance. Figure 2e shows contour plots of the in situ HT SANS patterns of the precursor mixture during heating. Micropores formed at 250 °C and merged at higher temperatures. However, preaging at 250 °C delayed micropore coalescence, inhibiting the merging into mesopores. The final products thus contained few meso- or macro-pores, enhancing cycle stability. Real-time investigations of particle and pore growth via small-angle scattering yield valuable quantitative information, but the spatial distributions of the secondary particles remain unclear. Therefore, combining electron microscopy and small-angle scattering analysis is optimal.

Compositional and Oxidation State Changes during Synthesis

Click to copy section linkSection link copied!

During synthesis, the need for in situ compositional and oxidation state analyses becomes evident when considering the complexities of calcination. During calcination, hydroxide precursor particles decompose, releasing gaseous water, while simultaneously, adsorption and diffusion of Li/O occur. The solid-state reactions and phase transformations within these particles are significantly influenced by the reaction temperature, which governs both mass transport and reaction thermodynamics. The complex interactions between mass transport and various chemical reactions at each temperature make it challenging to fully understand the reaction mechanisms. In situ analyses, such as XAS, transmission X-ray microscopy (TXM), and Raman spectroscopy, provide crucial insights by precisely identifying the distribution of chemical compositions and changes in oxidation states within the particles. This detailed understanding is imperative for optimizing synthesis conditions and ultimately enhancing the performance and stability of the final products.
In the synthesis of high-Ni layered oxides, the oxidation processes of transition metals, specifically Ni, Mn, and Co, play pivotal roles in defining the structures and properties of the final materials, particularly through the impact on cationic ordering within NiO6 octahedra. (17,18,28) The initial stage I (<250 °C) involves the preferential oxidation of Co and Mn, leading to partial Li insertion while maintaining the layered structure (See Figures 3a-c). This stage is crucial for establishing a framework that supports subsequent transformations. However, Ni oxidizes more slowly at lower temperatures, resulting in O loss and symmetry breaking within NiO6 octahedra, which contributes to Li/Ni mixing. In Stage III (>500 °C), Ni undergoes further oxidation, essential for achieving a more ordered structure. This higher-temperature oxidation facilitates the reconstruction of symmetry within NiO6 octahedra, transitioning from NiO6–x to fully coordinated NiO6, thereby inducing cationic ordering. This transformation is critical for enhancing the material’s structural integrity and electrochemical performance. Combined in situ XANES analysis indicates significant local changes within NiO6 octahedra driven by the differential oxidation rates of Co, Mn, and Ni. The reaction pathway is markedly influenced by these oxidation processes, with early stage Li/Ni mixing followed by increased ordering at higher temperatures.

Figure 3

Figure 3. (a) Schematic of the oxidation of Ni, Co, and Mn during the synthesis of LiNi0.77Mn0.13Co0.1O2. (b) In situ Ni K-edge XANES spectra during heating. (c) Normalized Ni2+, Co2+, and Mn2+ contents during heating derived from in situ XANES data. Reproduced with permission from ref (28) Copyright 2018 American Chemical Society. (d) Colored oxidation maps of Ni, Co, and Mn in intermediate particles produced under various calcination conditions. Reproduced with permission from ref (25) Copyright 2023 John Wiley and Sons.

A recent study employed advanced synchrotron-based X-ray techniques, specifically TXM and XANES, to investigate the local chemical, structural, and electronic state transformations occurring within Ni-rich layered oxide particles during calcination. (25) TXM effectively visualizes the oxidation state dynamics within individual cathode particles throughout the calcination process (Figure 3d). At temperatures below 300 °C (stage I), surface Ni, Co, and Mn were fully oxidized to their 3+, 3+, and 4+ states, respectively. TXM imaging revealed sharp boundaries between Mn4+ (green) and Mn2+ (red) due to Jahn–Teller distortion and the easy disproportionation of Mn3+. As the temperature increased to 400 °C, TXM images showed that the Ni3+- and Mn4+-containing shell became more uniform and slightly thicker, indicating further aerobic decomposition within the particles. Despite these changes, the core–shell geometries suggested that ambient oxygen had not fully penetrated the core, highlighting the presence of rate-limiting solid-state oxygen diffusion at this temperature. By 600 °C (stage II), accelerated incorporation and transport of ambient oxygen led to a homogeneous distribution of Co3+ and Mn4+ within the particle. At 870 °C (stage III), both oxygen distribution and TM oxidation states were uniform, facilitating fast oxygen transport throughout the particle. The oxidation state of Ni progressively increased from Ni2.3+ at 600 °C to Ni2.60+ at 870 °C, and ultimately to Ni2.67+ after full calcination following 10.5 h of annealing. This resulted in the formation of fully oxidized Li1Ni2.67+Co3+Mn4+O2 particles. In summary, precisely mapping the chemical composition distribution within particles sheds light on specific synthetic mechanisms, enabling more controlled and effective fabrication. This detailed understanding is crucial for optimizing material properties to meet specific performance criteria, thereby enhancing the functionality and reliability of the final materials in practical applications.

Prospects and Outlook

Click to copy section linkSection link copied!

In situ analysis during material synthesis is essential for developing advanced layered cathode materials. It offers real-time insights into dynamic structural evolution and reaction pathways, crucial for optimizing the electrochemical performance of these materials. Real-time data reveal how various synthetic parameters affect the formation and stability of desired phases, allowing for optimized calcination conditions to minimize defects and enhance material stability. For instance, observing moments of cationic disordering can refine calcination processes, reducing defects and improving cathode material performance. Additionally, in situ analysis can uncover previously unnoticed intermediate phases and reaction pathways, providing new insights into material formation mechanisms. Examining real-time lithium intercalation and deintercalation further informs the design of pore-defect-regulated cathode materials, leading to enhanced electrochemical stability and capacity retention. These insights facilitate the optimization of precursor materials, sintering temperatures, and atmospheres, resulting in more efficient synthesis processes.

These insights facilitate the optimization of precursor materials, sintering temperatures, and atmospheres, resulting in more efficient synthesis processes.

Future research should focus on developing advanced in situ characterization techniques and combining these methods to gain deeper insights into synthesis processes. Current existing real-time characterization techniques are summarized in Table 1. In situ synchrotron HT-XRD and XAS have been widely employed due to their accessibility and well-developed sample environments. The high intensity and resolution of synchrotron-based XRD analysis allow investigation of time-resolved atomic structural changes, such as phase fraction, Li–Ni intermixing, bond lengths, and crystallite size during the synthesis process. However, the quantification of Li SOF in the crystalline lattice is limited with X-ray due to the low scattering of Li, making combined studies with neutron diffraction essential. Currently, only a limited number of studies have employed neutron diffraction for real-time measurements during synthesis processes. Combining techniques such as in situ synchrotron XRD, XANES, TEM, and TXM can provide comprehensive information on phase transitions in bulk, atomic arrangements at the particle surface, and electronic and local structure changes. Global changes in crystal structure and oxidation state during synthesis can be defined through XRD and XANES analyses, while local structural evolution and oxidation states can be confirmed through TEM and TXM analyses. Many in situ HT experiments have been conducted using synchrotron X-ray analysis due to the ease of establishing sample environments. However, simulating synthesis environments with oxygen and lithium supply in electron beam measurement settings remains challenging, representing one of the obstacles to be overcome in electron microscopy. Additionally, combining small-angle scattering and TEM studies can offer insights into average microstructural and morphological changes, along with detailed local structural information at the particle level.
Table 1. Real-Time Observation Techniques and Key Analytical Parameters at Atomic, Nano, and Micro Scales for Each Synthesis Stage
 Stage I (RT–500 °C)Stage II (500–800 °C)Stage III (Aging 4–15 h)Stage IV (Cooling)
Atomic Structure (XRD, neutron diffraction, PDF)· Phase fraction (wt.%)· c/a & I(003)/I(104) ratio· c/a & I(003)/I(104) ratio· Phase fraction (wt.%) of Li2Co3 or LiOH
· Li–Ni intermixing (I(003)/I(104))· TM–O, Li–O bond lengths· Li and TM Occ. in 3a, 3b sites· c/a & I(003)/I(104) ratio
· TM–O, Li–O bond lengths· Li and TM Occ. in 3a, 3b sites· Crystallite size & Microstrain· Li and TM Occ. in 3a, 3b sites
· Li occ. in LixTM2-xO2· Crystallite size and microstrain · Microstrain
Microstructure & morphology (SEM, TEM, SAXS, SANS)· Micropore formation (pore size and volume)· Crystallite growth (size)· Crystallite growth (size) 
· Morphology change (needle-, plate-, brick-like)· Mesopore formation and growth (size and volume)· Macropore formation and growth (size and volume)· Surface reconstruction (Li–Ni reordering)
· Local crystal change (core–shell)· Li–Ni ordering at particle surface· Li–Ni ordering at particle surface 
Oxidation state and composition (XAS, TXM)· Mn, Co, and Ni oxidation (Global/local TM oxidation state)· Ni oxidation (Global/local TM oxidation state)· Ni oxidation (Global/local TM oxidation state)· Ni reduction
· Local lithiation in LixTM2-xO2  · Residual Li compounds

Incorporating machine learning and data-driven techniques into experimental design and analysis will significantly enhance research efficiency.

Incorporating machine learning and data-driven techniques into experimental design and analysis will significantly enhance research efficiency. These tools can help identify optimal synthesis parameters and modification strategies more rapidly than traditional trial-and-error methods, accelerating the development of high-performance cathode materials. Machine learning models trained on data from in situ analysis can predict outcomes of synthesis processes, providing a powerful tool for materials discovery and optimization. Furthermore, automated synthesis platforms equipped with in situ characterization tools are expected to perform high-throughput experiments, rapidly screening various synthesis parameters and conditions. (39) This approach can significantly accelerate the discovery of optimal synthesis protocols and materials. The data generated from these high-throughput experiments can feed into machine learning algorithms to predict and optimize synthesis conditions more efficiently. The continuous advancement and application of in situ analysis hold the key to unlocking new potentials in energy storage, paving the way for more efficient, durable, and high-performing LIBs.

Author Information

Click to copy section linkSection link copied!

  • Corresponding Authors
    • Hyungsub Kim - Neutron Science Division, Korea Atomic Energy Research Institute (KAERI), 111 Daedeok-daero 989 Beon-Gil, Yuseong-Gu, Daejeon 34057, Republic of Korea Email: [email protected]
    • Sang Mun Jeong - Department of Chemical Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Republic of KoreaOrcidhttps://orcid.org/0000-0002-3694-3110 Email: [email protected]
  • Author
    • Dongju Lee - Department of Advanced Materials Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Republic of KoreaChungbuk National University Hospital, 776, 1Sunhwan-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of KoreaOrcidhttps://orcid.org/0000-0002-5072-7457
  • Notes
    The authors declare no competing financial interest.

Biographies

Click to copy section linkSection link copied!

Dongju Lee is an Associate Professor in the Department of Advanced Materials Engineering at Chungbuk National University. He received his Ph.D. from KAIST in 2014. His research focuses on energy-related materials and devices, including the synthesis of low-dimensional materials.

Hyungsub Kim is a Senior Researcher in the Neutron Science Division at KAERI. He obtained his Ph.D. from Seoul National University in 2016 and currently works as an instrumental scientist for neutron powder diffraction. His research focuses on synthesizing advanced layered cathode materials using in situ characterization techniques.

Sang Mun Jeong is a Professor in the Department of Chemical Engineering at Chungbuk National University. He received his Ph.D. degree (1999) from KAIST. He currently leads the Regional Leading Research Center (RLRC), which is dedicated to developing next-generation battery materials. His research primarily focuses on energy-related materials and devices.

Acknowledgments

Click to copy section linkSection link copied!

This work was supported by the National Research Foundation of Korea (NRF) and the Commercialization Promotion Agency for R&D Outcomes (COMPA) funded by the Ministry of Science and ICT (Grant No.: RS-2023-00217581, RS-2023-00304768).

References

Click to copy section linkSection link copied!

This article references 39 other publications.

  1. 1
    Li, W.; Erickson, E. M.; Manthiram, A. High-nickel layered oxide cathodes for lithium-based automotive batteries. Nat. Energy 2020, 5, 2634,  DOI: 10.1038/s41560-019-0513-0
  2. 2
    Hong, J.; Gwon, H.; Jung, S.-K.; Ku, K.; Kang, K. Review─Lithium-Excess Layered Cathodes for Lithium Rechargeable Batteries. J. Electrochem. Soc. 2015, 162, A2447,  DOI: 10.1149/2.0071514jes
  3. 3
    Wang, C.-Y.; Liu, T.; Yang, X.-G.; Ge, S.; Stanley, N. V.; Rountree, E. S.; Leng, Y.; McCarthy, B. D. Fast charging of energy-dense lithium-ion batteries. Nature 2022, 611, 485490,  DOI: 10.1038/s41586-022-05281-0
  4. 4
    Sun, Y.-K. High-Capacity Layered Cathodes for Next-Generation Electric Vehicles. ACS Energy Lett. 2019, 4, 10421044,  DOI: 10.1021/acsenergylett.9b00652
  5. 5
    Wu, Z.; Zeng, G.; Yin, J.; Chiang, C.-L.; Zhang, Q.; Zhang, B.; Chen, J.; Yan, Y.; Tang, Y.; Zhang, H.; Zhou, S.; Wang, Q.; Kuai, X.; Lin, Y.-G.; Gu, L.; Qiao, Y.; Sun, S.-G. Unveiling the Evolution of LiCoO2 beyond 4.6 V. ACS Energy Lett. 2023, 8, 48064817,  DOI: 10.1021/acsenergylett.3c01954
  6. 6
    Sun, H. H.; Kim, U.-H.; Park, J.-H.; Park, S.-W.; Seo, D.-H.; Heller, A.; Mullins, C. B.; Yoon, C. S.; Sun, Y.-K. Transition metal-doped Ni-rich layered cathode materials for durable Li-ion batteries. Nat. Commun. 2021, 12, 6552,  DOI: 10.1038/s41467-021-26815-6
  7. 7
    Kalluri, S.; Yoon, M.; Jo, M.; Liu, H. K.; Dou, S. X.; Cho, J.; Guo, Z. Feasibility of Cathode Surface Coating Technology for High-Energy Lithium-ion and Beyond-Lithium-ion Batteries. Adv. Mater. 2017, 29, 1605807  DOI: 10.1002/adma.201605807
  8. 8
    Sun, H. H.; Ryu, H.-H.; Kim, U.-H.; Weeks, J. A.; Heller, A.; Sun, Y.-K.; Mullins, C. B. Beyond Doping and Coating: Prospective Strategies for Stable High-Capacity Layered Ni-Rich Cathodes. ACS Energy Lett. 2020, 5, 11361146,  DOI: 10.1021/acsenergylett.0c00191
  9. 9
    Liu, D.; Shadike, Z.; Lin, R.; Qian, K.; Li, H.; Li, K.; Wang, S.; Yu, Q.; Liu, M.; Ganapathy, S.; Qin, X.; Yang, Q.-H.; Wagemaker, M.; Kang, F.; Yang, X.-Q.; Li, B. Review of Recent Development of In Situ/Operando Characterization Techniques for Lithium Battery Research. Adv. Mater. 2019, 31, 1806620  DOI: 10.1002/adma.201806620
  10. 10
    Boebinger, M. G.; Lewis, J. A.; Sandoval, S. E.; McDowell, M. T. Understanding Transformations in Battery Materials Using In Situ and Operando Experiments: Progress and Outlook. ACS Energy Lett. 2020, 5, 335345,  DOI: 10.1021/acsenergylett.9b02514
  11. 11
    Hong, J.; Gent, W. E.; Xiao, P.; Lim, K.; Seo, D.-H.; Wu, J.; Csernica, P. M.; Takacs, C. J.; Nordlund, D.; Sun, C.-J.; Stone, K. H.; Passarello, D.; Yang, W.; Prendergast, D.; Ceder, G.; Toney, M. F.; Chueh, W. C. Metal–oxygen decoordination stabilizes anion redox in Li-rich oxides. Nat. Mater. 2019, 18, 256265,  DOI: 10.1038/s41563-018-0276-1
  12. 12
    Jung, S.-K.; Kim, H.; Song, S. H.; Lee, S.; Kim, J.; Kang, K. Unveiling the Role of Transition-Metal Ions in the Thermal Degradation of Layered Ni–Co–Mn Cathodes for Lithium Rechargeable Batteries. Adv. Funct. Mater. 2022, 32, 2108790  DOI: 10.1002/adfm.202108790
  13. 13
    Song, S. H.; Kim, H. S.; Kim, K. S.; Hong, S.; Jeon, H.; Lim, J.; Jung, Y. H.; Ahn, H.; Jang, J. D.; Kim, M.-H.; Seo, J. H.; Kwon, J.-H.; Kim, D.; Lee, Y. J.; Han, Y.-S.; Park, K.-Y.; Kim, C.; Yu, S.-H.; Park, H.; Jin, H. M.; Kim, H. Toward a Nanoscale-Defect-Free Ni-Rich Layered Oxide Cathode Through Regulated Pore Evolution for Long-Lifespan Li Rechargeable Batteries. Adv. Funct. Mater. 2024, 34, 2306654  DOI: 10.1002/adfm.202306654
  14. 14
    Park, H.; Park, H.; Song, K.; Song, S. H.; Kang, S.; Ko, K.-H.; Eum, D.; Jeon, Y.; Kim, J.; Seong, W. M.; Kim, H.; Park, J.; Kang, K. In situ multiscale probing of the synthesis of a Ni-rich layered oxide cathode reveals reaction heterogeneity driven by competing kinetic pathways. Nat. Chem. 2022, 14, 614622,  DOI: 10.1038/s41557-022-00915-2
  15. 15
    Wu, Y.; Wu, H.; Deng, J.; Han, Z.; Xiao, X.; Wang, L.; Chen, Z.; Deng, Y.; He, X. Insight of Synthesis of Single Crystal Ni-Rich LiNi1–xyCoxMnyO2 Cathodes. Adv. Energy Mater. 2024, 14, 2303758  DOI: 10.1002/aenm.202303758
  16. 16
    Li, H.; Wang, L.; Song, Y.; Zhang, Z.; Du, A.; Tang, Y.; Wang, J.; He, X. Why the Synthesis Affects Performance of Layered Transition Metal Oxide Cathode Materials for Li-Ion Batteries. Adv. Mater. 2024, 36, 2312292  DOI: 10.1002/adma.202312292
  17. 17
    Wang, F.; Barai, P.; Kahvecioglu, O.; Pupek, K. Z.; Bai, J.; Srinivasan, V. Process design for calcination of nickel-based cathode materials by in situ characterization and multiscale modeling. J. Mater. Res. 2022, 37, 31973215,  DOI: 10.1557/s43578-022-00678-z
  18. 18
    Wang, F.; Bai, J. Synthesis and Processing by Design of High-Nickel Cathode Materials. Batteries Supercaps 2022, 5, e202100174  DOI: 10.1002/batt.202100174
  19. 19
    Wang, S.; Hua, W.; Missyul, A.; Darma, M. S. D.; Tayal, A.; Indris, S.; Ehrenberg, H.; Liu, L.; Knapp, M. Kinetic Control of Long-Range Cationic Ordering in the Synthesis of Layered Ni-Rich Oxides. Adv. Funct. Mater. 2021, 31, 2009949  DOI: 10.1002/adfm.202009949
  20. 20
    Bai, J.; Sun, W.; Zhao, J.; Wang, D.; Xiao, P.; Ko, J. Y. P.; Huq, A.; Ceder, G.; Wang, F. Kinetic Pathways Templated by Low-Temperature Intermediates during Solid-State Synthesis of Layered Oxides. Chem. Mater. 2020, 32, 99069913,  DOI: 10.1021/acs.chemmater.0c02568
  21. 21
    Goonetilleke, D.; Suard, E.; Bergner, B.; Janek, J.; Brezesinski, T.; Bianchini, M. In situ neutron diffraction to investigate the solid-state synthesis of Ni-rich cathode materials. J. Appl. Crystallogr. 2023, 56, 10661075,  DOI: 10.1107/S1600576723004909
  22. 22
    Ying, B.; Fitzpatrick, J. R.; Teng, Z.; Chen, T.; Lo, T. W. B.; Siozios, V.; Murray, C. A.; Brand, H. E. A.; Day, S.; Tang, C. C.; Weatherup, R. S.; Merz, M.; Nagel, P.; Schuppler, S.; Winter, M.; Kleiner, K. Monitoring the Formation of Nickel-Poor and Nickel-Rich Oxide Cathode Materials for Lithium-Ion Batteries with Synchrotron Radiation. Chem. Mater. 2023, 35, 15141526,  DOI: 10.1021/acs.chemmater.2c02639
  23. 23
    Wu, C.; Ban, J.; Chen, T.; Wang, J.; He, Y.; Wu, Z.-g. Evolution Path of Precursor-Induced High-Temperature Lithiation Reaction during the Synthesis of Lithium-Rich Cathode Materials. ACS Omega 2024, 9, 1519115201,  DOI: 10.1021/acsomega.3c09567
  24. 24
    Wolfman, M.; Wang, X.; Garcia, J. C.; Barai, P.; Stubbs, J. E.; Eng, P. J.; Kahvecioglu, O.; Kinnibrugh, T. L.; Madsen, K. E.; Iddir, H.; Srinivasan, V.; Fister, T. T. The Importance of Surface Oxygen for Lithiation and Morphology Evolution during Calcination of High-Nickel NMC Cathodes. Adv. Energy Mater. 2022, 12, 2102951  DOI: 10.1002/aenm.202102951
  25. 25
    Jo, S.; Han, J.; Seo, S.; Kwon, O.-S.; Choi, S.; Zhang, J.; Hyun, H.; Oh, J.; Kim, J.; Chung, J.; Kim, H.; Wang, J.; Bae, J.; Moon, J.; Park, Y.-C.; Hong, M.-H.; Kim, M.; Liu, Y.; Sohn, I.; Jung, K.; Lim, J. Solid-State Reaction Heterogeneity During Calcination of Lithium-Ion Battery Cathode. Adv. Mater. 2023, 35, 2207076  DOI: 10.1002/adma.202207076
  26. 26
    Kim, K. S.; Jeon, M. K.; Song, S. H.; Hong, S.; Kim, H. S.; Kim, S.-W.; Kim, J.; Oh, P.; Hwang, J.; Song, J.; Ma, J.; Woo, J.-J.; Yu, S.-H.; Kim, H. Upcycling spent cathodes into single-crystalline Ni-rich cathode materials through selective lithium extraction. J. Mater. Chem. A 2023, 11, 2122221230,  DOI: 10.1039/D3TA03900E
  27. 27
    Zhao, J.; Zhang, W.; Huq, A.; Misture, S. T.; Zhang, B.; Guo, S.; Wu, L.; Zhu, Y.; Chen, Z.; Amine, K.; Pan, F.; Bai, J.; Wang, F. In Situ Probing and Synthetic Control of Cationic Ordering in Ni-Rich Layered Oxide Cathodes. Adv. Energy Mater. 2017, 7, 1601266  DOI: 10.1002/aenm.201601266
  28. 28
    Zhang, M.-J.; Teng, G.; Chen-Wiegart, Y.-c. K.; Duan, Y.; Ko, J. Y. P.; Zheng, J.; Thieme, J.; Dooryhee, E.; Chen, Z.; Bai, J.; Amine, K.; Pan, F.; Wang, F. Cationic Ordering Coupled to Reconstruction of Basic Building Units during Synthesis of High-Ni Layered Oxides. J. Am. Chem. Soc. 2018, 140, 1248412492,  DOI: 10.1021/jacs.8b06150
  29. 29
    Wang, D.; Kou, R.; Ren, Y.; Sun, C.-J.; Zhao, H.; Zhang, M.-J.; Li, Y.; Huq, A.; Ko, J. Y. P.; Pan, F.; Sun, Y.-K.; Yang, Y.; Amine, K.; Bai, J.; Chen, Z.; Wang, F. Synthetic Control of Kinetic Reaction Pathway and Cationic Ordering in High-Ni Layered Oxide Cathodes. Adv. Mater. 2017, 29, 1606715  DOI: 10.1002/adma.201606715
  30. 30
    Wang, D.; Xin, C.; Zhang, M.; Bai, J.; Zheng, J.; Kou, R.; Peter Ko, J. Y.; Huq, A.; Zhong, G.; Sun, C.-J.; Yang, Y.; Chen, Z.; Xiao, Y.; Amine, K.; Pan, F.; Wang, F. Intrinsic Role of Cationic Substitution in Tuning Li/Ni Mixing in High-Ni Layered Oxides. Chem. Mater. 2019, 31, 27312740,  DOI: 10.1021/acs.chemmater.8b04673
  31. 31
    Duan, Y.; Yang, L.; Zhang, M.-J.; Chen, Z.; Bai, J.; Amine, K.; Pan, F.; Wang, F. Insights into Li/Ni ordering and surface reconstruction during synthesis of Ni-rich layered oxides. J. Mater. Chem. A 2019, 7, 513519,  DOI: 10.1039/C8TA10553G
  32. 32
    Bianchini, M.; Fauth, F.; Hartmann, P.; Brezesinski, T.; Janek, J. An in situ structural study on the synthesis and decomposition of LiNiO2. J. Mater. Chem. A 2020, 8, 18081820,  DOI: 10.1039/C9TA12073D
  33. 33
    Zhang, M.-J.; Hu, X.; Li, M.; Duan, Y.; Yang, L.; Yin, C.; Ge, M.; Xiao, X.; Lee, W.-K.; Ko, J. Y. P.; Amine, K.; Chen, Z.; Zhu, Y.; Dooryhee, E.; Bai, J.; Pan, F.; Wang, F. Cooling Induced Surface Reconstruction during Synthesis of High-Ni Layered Oxides. Adv. Energy Mater. 2019, 9, 1901915  DOI: 10.1002/aenm.201901915
  34. 34
    Casas-Cabanas, M.; Palacín, M. R.; Rodríguez-Carvajal, J. Microstructural analysis of nickel hydroxide: Anisotropic size versus stacking faults. Powder Diffr. 2005, 20, 334344,  DOI: 10.1154/1.2137340
  35. 35
    Gim, J.; Zhang, Y.; Gao, H.; Xu, G.-L.; Guo, F.; Ren, Y.; Amine, K.; Chen, Z. Probing solid-state reaction through microstrain: A case study on synthesis of LiCoO2. J. Power Sources 2020, 469, 228422  DOI: 10.1016/j.jpowsour.2020.228422
  36. 36
    Tang, L.; Cheng, X.; Wu, R.; Cao, T.; Lu, J.; Zhang, Y.; Zhang, Z. Monitoring the morphology evolution of LiNi0.8Mn0.1Co0.1O2 during high-temperature solid state synthesis via in situ SEM. J. Energy Chem. 2022, 66, 915,  DOI: 10.1016/j.jechem.2021.07.021
  37. 37
    Fratzl, P. Small-angle scattering in materials science - a short review of applications in alloys, ceramics and composite materials. J. Appl. Crystallogr. 2003, 36, 397404,  DOI: 10.1107/S0021889803000335
  38. 38
    Feng, Z.; Barai, P.; Gim, J.; Yuan, K.; Wu, Y. A.; Xie, Y.; Liu, Y.; Srinivasan, V. In Situ Monitoring of the Growth of Nickel, Manganese, and Cobalt Hydroxide Precursors during Co-Precipitation Synthesis of Li-Ion Cathode Materials. J. Electrochem. Soc. 2018, 165, A3077,  DOI: 10.1149/2.0511813jes
  39. 39
    Lu, J.-M.; Pan, J.-Z.; Mo, Y.-M.; Fang, Q. Automated Intelligent Platforms for High-Throughput Chemical Synthesis. Artif. Intell. Chem. 2024, 2, 100057  DOI: 10.1016/j.aichem.2024.100057

Cited By

Click to copy section linkSection link copied!

This article has not yet been cited by other publications.

ACS Energy Letters

Cite this: ACS Energy Lett. 2024, 9, 9, 4255–4264
Click to copy citationCitation copied!
https://doi.org/10.1021/acsenergylett.4c01540
Published August 2, 2024

Copyright © 2024 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY-NC-ND 4.0 .

Article Views

1806

Altmetric

-

Citations

-
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    Scheme 1

    Scheme 1. Conventional Synthesis Protocol of Layered Cathode Materials and the Corresponding Structural Changes at Each Stage

    Figure 1

    Figure 1. (a) The weight fraction of the precursor mixture for the synthesis of LiNi0.6Co0.2Mn0.2O2 obtained from Rietveld refinement of in situ HT-XRD data. Reproduced with permission from ref (19) Copyright 2021 John Wiley and Sons. (b) The c/a ratio in the intermediate structures of Lix (Co0.2Ni0.8)1–xO2 and LixNi2–xO2. Reproduced with permission from ref (20) Copyright 2020 American Chemical Society. (c) Ni–O and Li–O bond length changes during synthesis for LiNi0.8Co0.2O2 under O2 flow. Reproduced with permission from ref (27) Copyright 2017 John Wiley and Sons. (d) In situ PDF patterns during the synthesis of LiNi0.77Mn0.13Co0.1O2. Reproduced with permission from ref (28) Copyright 2018 American Chemical Society. (e) Li SOFs as a function of temperature upon heating of LiNixMn1–xO2 (x = 0, 0.9, 0.75). Reproduced with permission from ref (21) Copyright 2023 IUCR Journals. (f) Domain sizes derived from Rietveld refinement of in situ HT-XRD patterns during the synthesis of NCM811. Reproduced with permission from ref (24) Copyright 2022 John Wiley and Sons.

    Figure 2

    Figure 2. (a) In situ HT SEM images at 300, 750, 940, and 1000 °C during the synthesis of NCM811. Reproduced with permission from ref (36) Copyright 2022 Elsevier. (b) In situ TEM images and negative intensity changes in the core–shell regions during the synthesis of LiNi0.6Co0.2Mn0.2O2. Reproduced with permission from ref (14) Copyright 2022 Springer Nature. (c) Wide-angle X-ray scattering data of Ni1/3Mn1/3Co1/3(OH)2 coprecipitated in a pH 10.6 solution. (d) The effective radius, R, of Ni1/3Mn1/3Co1/3(OH)2 coprecipitated in pH 10.6 solution (Sample A) and pH 11.4 solution (Sample B). Reproduced with permission from ref (38) Copyright 2018 The Electrochemical Society. (e) In situ SANS patterns during the synthesis of LiNi0.92Co0.03Mn0.05O2 without and with preaging at 250 °C for 6 h. Reproduced with permission from ref (13) Copyright 2024 John Wiley and Sons.

    Figure 3

    Figure 3. (a) Schematic of the oxidation of Ni, Co, and Mn during the synthesis of LiNi0.77Mn0.13Co0.1O2. (b) In situ Ni K-edge XANES spectra during heating. (c) Normalized Ni2+, Co2+, and Mn2+ contents during heating derived from in situ XANES data. Reproduced with permission from ref (28) Copyright 2018 American Chemical Society. (d) Colored oxidation maps of Ni, Co, and Mn in intermediate particles produced under various calcination conditions. Reproduced with permission from ref (25) Copyright 2023 John Wiley and Sons.

  • References


    This article references 39 other publications.

    1. 1
      Li, W.; Erickson, E. M.; Manthiram, A. High-nickel layered oxide cathodes for lithium-based automotive batteries. Nat. Energy 2020, 5, 2634,  DOI: 10.1038/s41560-019-0513-0
    2. 2
      Hong, J.; Gwon, H.; Jung, S.-K.; Ku, K.; Kang, K. Review─Lithium-Excess Layered Cathodes for Lithium Rechargeable Batteries. J. Electrochem. Soc. 2015, 162, A2447,  DOI: 10.1149/2.0071514jes
    3. 3
      Wang, C.-Y.; Liu, T.; Yang, X.-G.; Ge, S.; Stanley, N. V.; Rountree, E. S.; Leng, Y.; McCarthy, B. D. Fast charging of energy-dense lithium-ion batteries. Nature 2022, 611, 485490,  DOI: 10.1038/s41586-022-05281-0
    4. 4
      Sun, Y.-K. High-Capacity Layered Cathodes for Next-Generation Electric Vehicles. ACS Energy Lett. 2019, 4, 10421044,  DOI: 10.1021/acsenergylett.9b00652
    5. 5
      Wu, Z.; Zeng, G.; Yin, J.; Chiang, C.-L.; Zhang, Q.; Zhang, B.; Chen, J.; Yan, Y.; Tang, Y.; Zhang, H.; Zhou, S.; Wang, Q.; Kuai, X.; Lin, Y.-G.; Gu, L.; Qiao, Y.; Sun, S.-G. Unveiling the Evolution of LiCoO2 beyond 4.6 V. ACS Energy Lett. 2023, 8, 48064817,  DOI: 10.1021/acsenergylett.3c01954
    6. 6
      Sun, H. H.; Kim, U.-H.; Park, J.-H.; Park, S.-W.; Seo, D.-H.; Heller, A.; Mullins, C. B.; Yoon, C. S.; Sun, Y.-K. Transition metal-doped Ni-rich layered cathode materials for durable Li-ion batteries. Nat. Commun. 2021, 12, 6552,  DOI: 10.1038/s41467-021-26815-6
    7. 7
      Kalluri, S.; Yoon, M.; Jo, M.; Liu, H. K.; Dou, S. X.; Cho, J.; Guo, Z. Feasibility of Cathode Surface Coating Technology for High-Energy Lithium-ion and Beyond-Lithium-ion Batteries. Adv. Mater. 2017, 29, 1605807  DOI: 10.1002/adma.201605807
    8. 8
      Sun, H. H.; Ryu, H.-H.; Kim, U.-H.; Weeks, J. A.; Heller, A.; Sun, Y.-K.; Mullins, C. B. Beyond Doping and Coating: Prospective Strategies for Stable High-Capacity Layered Ni-Rich Cathodes. ACS Energy Lett. 2020, 5, 11361146,  DOI: 10.1021/acsenergylett.0c00191
    9. 9
      Liu, D.; Shadike, Z.; Lin, R.; Qian, K.; Li, H.; Li, K.; Wang, S.; Yu, Q.; Liu, M.; Ganapathy, S.; Qin, X.; Yang, Q.-H.; Wagemaker, M.; Kang, F.; Yang, X.-Q.; Li, B. Review of Recent Development of In Situ/Operando Characterization Techniques for Lithium Battery Research. Adv. Mater. 2019, 31, 1806620  DOI: 10.1002/adma.201806620
    10. 10
      Boebinger, M. G.; Lewis, J. A.; Sandoval, S. E.; McDowell, M. T. Understanding Transformations in Battery Materials Using In Situ and Operando Experiments: Progress and Outlook. ACS Energy Lett. 2020, 5, 335345,  DOI: 10.1021/acsenergylett.9b02514
    11. 11
      Hong, J.; Gent, W. E.; Xiao, P.; Lim, K.; Seo, D.-H.; Wu, J.; Csernica, P. M.; Takacs, C. J.; Nordlund, D.; Sun, C.-J.; Stone, K. H.; Passarello, D.; Yang, W.; Prendergast, D.; Ceder, G.; Toney, M. F.; Chueh, W. C. Metal–oxygen decoordination stabilizes anion redox in Li-rich oxides. Nat. Mater. 2019, 18, 256265,  DOI: 10.1038/s41563-018-0276-1
    12. 12
      Jung, S.-K.; Kim, H.; Song, S. H.; Lee, S.; Kim, J.; Kang, K. Unveiling the Role of Transition-Metal Ions in the Thermal Degradation of Layered Ni–Co–Mn Cathodes for Lithium Rechargeable Batteries. Adv. Funct. Mater. 2022, 32, 2108790  DOI: 10.1002/adfm.202108790
    13. 13
      Song, S. H.; Kim, H. S.; Kim, K. S.; Hong, S.; Jeon, H.; Lim, J.; Jung, Y. H.; Ahn, H.; Jang, J. D.; Kim, M.-H.; Seo, J. H.; Kwon, J.-H.; Kim, D.; Lee, Y. J.; Han, Y.-S.; Park, K.-Y.; Kim, C.; Yu, S.-H.; Park, H.; Jin, H. M.; Kim, H. Toward a Nanoscale-Defect-Free Ni-Rich Layered Oxide Cathode Through Regulated Pore Evolution for Long-Lifespan Li Rechargeable Batteries. Adv. Funct. Mater. 2024, 34, 2306654  DOI: 10.1002/adfm.202306654
    14. 14
      Park, H.; Park, H.; Song, K.; Song, S. H.; Kang, S.; Ko, K.-H.; Eum, D.; Jeon, Y.; Kim, J.; Seong, W. M.; Kim, H.; Park, J.; Kang, K. In situ multiscale probing of the synthesis of a Ni-rich layered oxide cathode reveals reaction heterogeneity driven by competing kinetic pathways. Nat. Chem. 2022, 14, 614622,  DOI: 10.1038/s41557-022-00915-2
    15. 15
      Wu, Y.; Wu, H.; Deng, J.; Han, Z.; Xiao, X.; Wang, L.; Chen, Z.; Deng, Y.; He, X. Insight of Synthesis of Single Crystal Ni-Rich LiNi1–xyCoxMnyO2 Cathodes. Adv. Energy Mater. 2024, 14, 2303758  DOI: 10.1002/aenm.202303758
    16. 16
      Li, H.; Wang, L.; Song, Y.; Zhang, Z.; Du, A.; Tang, Y.; Wang, J.; He, X. Why the Synthesis Affects Performance of Layered Transition Metal Oxide Cathode Materials for Li-Ion Batteries. Adv. Mater. 2024, 36, 2312292  DOI: 10.1002/adma.202312292
    17. 17
      Wang, F.; Barai, P.; Kahvecioglu, O.; Pupek, K. Z.; Bai, J.; Srinivasan, V. Process design for calcination of nickel-based cathode materials by in situ characterization and multiscale modeling. J. Mater. Res. 2022, 37, 31973215,  DOI: 10.1557/s43578-022-00678-z
    18. 18
      Wang, F.; Bai, J. Synthesis and Processing by Design of High-Nickel Cathode Materials. Batteries Supercaps 2022, 5, e202100174  DOI: 10.1002/batt.202100174
    19. 19
      Wang, S.; Hua, W.; Missyul, A.; Darma, M. S. D.; Tayal, A.; Indris, S.; Ehrenberg, H.; Liu, L.; Knapp, M. Kinetic Control of Long-Range Cationic Ordering in the Synthesis of Layered Ni-Rich Oxides. Adv. Funct. Mater. 2021, 31, 2009949  DOI: 10.1002/adfm.202009949
    20. 20
      Bai, J.; Sun, W.; Zhao, J.; Wang, D.; Xiao, P.; Ko, J. Y. P.; Huq, A.; Ceder, G.; Wang, F. Kinetic Pathways Templated by Low-Temperature Intermediates during Solid-State Synthesis of Layered Oxides. Chem. Mater. 2020, 32, 99069913,  DOI: 10.1021/acs.chemmater.0c02568
    21. 21
      Goonetilleke, D.; Suard, E.; Bergner, B.; Janek, J.; Brezesinski, T.; Bianchini, M. In situ neutron diffraction to investigate the solid-state synthesis of Ni-rich cathode materials. J. Appl. Crystallogr. 2023, 56, 10661075,  DOI: 10.1107/S1600576723004909
    22. 22
      Ying, B.; Fitzpatrick, J. R.; Teng, Z.; Chen, T.; Lo, T. W. B.; Siozios, V.; Murray, C. A.; Brand, H. E. A.; Day, S.; Tang, C. C.; Weatherup, R. S.; Merz, M.; Nagel, P.; Schuppler, S.; Winter, M.; Kleiner, K. Monitoring the Formation of Nickel-Poor and Nickel-Rich Oxide Cathode Materials for Lithium-Ion Batteries with Synchrotron Radiation. Chem. Mater. 2023, 35, 15141526,  DOI: 10.1021/acs.chemmater.2c02639
    23. 23
      Wu, C.; Ban, J.; Chen, T.; Wang, J.; He, Y.; Wu, Z.-g. Evolution Path of Precursor-Induced High-Temperature Lithiation Reaction during the Synthesis of Lithium-Rich Cathode Materials. ACS Omega 2024, 9, 1519115201,  DOI: 10.1021/acsomega.3c09567
    24. 24
      Wolfman, M.; Wang, X.; Garcia, J. C.; Barai, P.; Stubbs, J. E.; Eng, P. J.; Kahvecioglu, O.; Kinnibrugh, T. L.; Madsen, K. E.; Iddir, H.; Srinivasan, V.; Fister, T. T. The Importance of Surface Oxygen for Lithiation and Morphology Evolution during Calcination of High-Nickel NMC Cathodes. Adv. Energy Mater. 2022, 12, 2102951  DOI: 10.1002/aenm.202102951
    25. 25
      Jo, S.; Han, J.; Seo, S.; Kwon, O.-S.; Choi, S.; Zhang, J.; Hyun, H.; Oh, J.; Kim, J.; Chung, J.; Kim, H.; Wang, J.; Bae, J.; Moon, J.; Park, Y.-C.; Hong, M.-H.; Kim, M.; Liu, Y.; Sohn, I.; Jung, K.; Lim, J. Solid-State Reaction Heterogeneity During Calcination of Lithium-Ion Battery Cathode. Adv. Mater. 2023, 35, 2207076  DOI: 10.1002/adma.202207076
    26. 26
      Kim, K. S.; Jeon, M. K.; Song, S. H.; Hong, S.; Kim, H. S.; Kim, S.-W.; Kim, J.; Oh, P.; Hwang, J.; Song, J.; Ma, J.; Woo, J.-J.; Yu, S.-H.; Kim, H. Upcycling spent cathodes into single-crystalline Ni-rich cathode materials through selective lithium extraction. J. Mater. Chem. A 2023, 11, 2122221230,  DOI: 10.1039/D3TA03900E
    27. 27
      Zhao, J.; Zhang, W.; Huq, A.; Misture, S. T.; Zhang, B.; Guo, S.; Wu, L.; Zhu, Y.; Chen, Z.; Amine, K.; Pan, F.; Bai, J.; Wang, F. In Situ Probing and Synthetic Control of Cationic Ordering in Ni-Rich Layered Oxide Cathodes. Adv. Energy Mater. 2017, 7, 1601266  DOI: 10.1002/aenm.201601266
    28. 28
      Zhang, M.-J.; Teng, G.; Chen-Wiegart, Y.-c. K.; Duan, Y.; Ko, J. Y. P.; Zheng, J.; Thieme, J.; Dooryhee, E.; Chen, Z.; Bai, J.; Amine, K.; Pan, F.; Wang, F. Cationic Ordering Coupled to Reconstruction of Basic Building Units during Synthesis of High-Ni Layered Oxides. J. Am. Chem. Soc. 2018, 140, 1248412492,  DOI: 10.1021/jacs.8b06150
    29. 29
      Wang, D.; Kou, R.; Ren, Y.; Sun, C.-J.; Zhao, H.; Zhang, M.-J.; Li, Y.; Huq, A.; Ko, J. Y. P.; Pan, F.; Sun, Y.-K.; Yang, Y.; Amine, K.; Bai, J.; Chen, Z.; Wang, F. Synthetic Control of Kinetic Reaction Pathway and Cationic Ordering in High-Ni Layered Oxide Cathodes. Adv. Mater. 2017, 29, 1606715  DOI: 10.1002/adma.201606715
    30. 30
      Wang, D.; Xin, C.; Zhang, M.; Bai, J.; Zheng, J.; Kou, R.; Peter Ko, J. Y.; Huq, A.; Zhong, G.; Sun, C.-J.; Yang, Y.; Chen, Z.; Xiao, Y.; Amine, K.; Pan, F.; Wang, F. Intrinsic Role of Cationic Substitution in Tuning Li/Ni Mixing in High-Ni Layered Oxides. Chem. Mater. 2019, 31, 27312740,  DOI: 10.1021/acs.chemmater.8b04673
    31. 31
      Duan, Y.; Yang, L.; Zhang, M.-J.; Chen, Z.; Bai, J.; Amine, K.; Pan, F.; Wang, F. Insights into Li/Ni ordering and surface reconstruction during synthesis of Ni-rich layered oxides. J. Mater. Chem. A 2019, 7, 513519,  DOI: 10.1039/C8TA10553G
    32. 32
      Bianchini, M.; Fauth, F.; Hartmann, P.; Brezesinski, T.; Janek, J. An in situ structural study on the synthesis and decomposition of LiNiO2. J. Mater. Chem. A 2020, 8, 18081820,  DOI: 10.1039/C9TA12073D
    33. 33
      Zhang, M.-J.; Hu, X.; Li, M.; Duan, Y.; Yang, L.; Yin, C.; Ge, M.; Xiao, X.; Lee, W.-K.; Ko, J. Y. P.; Amine, K.; Chen, Z.; Zhu, Y.; Dooryhee, E.; Bai, J.; Pan, F.; Wang, F. Cooling Induced Surface Reconstruction during Synthesis of High-Ni Layered Oxides. Adv. Energy Mater. 2019, 9, 1901915  DOI: 10.1002/aenm.201901915
    34. 34
      Casas-Cabanas, M.; Palacín, M. R.; Rodríguez-Carvajal, J. Microstructural analysis of nickel hydroxide: Anisotropic size versus stacking faults. Powder Diffr. 2005, 20, 334344,  DOI: 10.1154/1.2137340
    35. 35
      Gim, J.; Zhang, Y.; Gao, H.; Xu, G.-L.; Guo, F.; Ren, Y.; Amine, K.; Chen, Z. Probing solid-state reaction through microstrain: A case study on synthesis of LiCoO2. J. Power Sources 2020, 469, 228422  DOI: 10.1016/j.jpowsour.2020.228422
    36. 36
      Tang, L.; Cheng, X.; Wu, R.; Cao, T.; Lu, J.; Zhang, Y.; Zhang, Z. Monitoring the morphology evolution of LiNi0.8Mn0.1Co0.1O2 during high-temperature solid state synthesis via in situ SEM. J. Energy Chem. 2022, 66, 915,  DOI: 10.1016/j.jechem.2021.07.021
    37. 37
      Fratzl, P. Small-angle scattering in materials science - a short review of applications in alloys, ceramics and composite materials. J. Appl. Crystallogr. 2003, 36, 397404,  DOI: 10.1107/S0021889803000335
    38. 38
      Feng, Z.; Barai, P.; Gim, J.; Yuan, K.; Wu, Y. A.; Xie, Y.; Liu, Y.; Srinivasan, V. In Situ Monitoring of the Growth of Nickel, Manganese, and Cobalt Hydroxide Precursors during Co-Precipitation Synthesis of Li-Ion Cathode Materials. J. Electrochem. Soc. 2018, 165, A3077,  DOI: 10.1149/2.0511813jes
    39. 39
      Lu, J.-M.; Pan, J.-Z.; Mo, Y.-M.; Fang, Q. Automated Intelligent Platforms for High-Throughput Chemical Synthesis. Artif. Intell. Chem. 2024, 2, 100057  DOI: 10.1016/j.aichem.2024.100057