Highly Graphitic Carbon Coating on Li_1.25Nb_0.25V_0.5O₂ Derived from a Precursor with a Perylene Core for High-Power Battery Applications

A Li-excess cation-disordered rocksalt (DRS) positive electrode material with Nb/V ions, Li_1.25Nb_0.25V_0.5O₂ (LNVO), delivers a high reversible specific capacity of >250 mA h g^–1 on the basis of two-electron redox of V³⁺/V⁵⁺. However, the inferior rate performance originating from a character of the disordered structure prevents its use for practical applications. Here, a facile and efficient top-down approach to synthesize nanosized LNVO carbon composited materials has been developed through a combination of ball-milling and subsequent heat-treating steps. The markedly improved rate capability is achieved by highly graphitic carbon coating with superior conductivity derived from a precursor with a perylene core. The growth of particle sizes of LNVO is effectively suppressed by uniform mixing of the precursor by optimized milling conditions. The optimized nanosized sample with shorter Li ion migration paths shows excellent rate capability for the rocksalt oxide. Moreover, superior capacity retention for continuous 100 cycles is also achieved. Furthermore, by lowering the Li ion migration barrier at elevated temperatures, a larger reversible specific capacity of 300 mA h g^–1, which nearly corresponds to its theoretical specific capacity, is obtained, coupled with further improved rate capability because of facile conduction for Li ions in oxides and electrolyte. This finding opens the possibility to develop high-performance electrode materials with a cation-DRS structure for practical battery applications.