Electrochemical Behavior of Rechargeable Al–Ni Battery Systems in Concentrated [EMIm]Cl-AlCl₃ Electrolyte

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In this work, the electrochemical behavior of the Al–Ni battery system in electrolyte composed of aluminum chloride (AlCl₃) and 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) with a molar ratio of 1.3 is investigated. The results reveal that the reversible capacity, which is based on the de/alloying process of Al on a Ni cathode, can be triggered only once the Ni electrode has been chlorinated. The value of reversible capacity is related to the chlorination degree of the nickel electrode. However, because the produced nickel chloride is soluble in the [EMIm]Cl-based electrolyte, the dissolved Ni²⁺ can migrate to the Al anode side and spontaneously react with the Al electrode, causing the battery to fail drastically. To safeguard the Al anode, an interlayer composed of Al powder is inserted between the separators to react with the dissolved Ni ions. The upgraded Al–Ni battery system can provide significantly improved performance, with cycling stability increasing from 84 to over 580 cycles in an 8 min controlled galvanostatic charge procedure.