Electrolyte engineering and interphase chemistry toward high-performance nickel-rich cathodes: Progress and perspectives

Nickel (Ni)-rich layered oxides have drawn great attention as cathode for lithium batteries due to their high capacity, high working voltage and competitive cost. Unfortunately, the operation of Ni-rich cathodes suffers from the notorious structural degradation and interfacial side reactions with electrolytes and thus incurs premature failure, especially at high charge cut-off voltages (≥4.4 V). For this, various structural and interphase regulation strategies (such as coating modification, element doping, and electrolyte engineering) are developed to enhance the cycling survivability of Ni-rich cathodes. Among them, electrolyte engineering by changing solvation structure and introducing additives has been considered an efficient method for constructing robust cathode-electrolyte interphases (CEI), inhibiting the formation of harmful species (such as HF and H 2 O) or restraining the dissolution of transition metal ions. However, there is still an absence of systematic guidelines for selecting and designing competitive electrolyte systems for Ni-rich layered cathodes. In this review, we comprehensively summarize the recent research progress on electrolyte engineering for Ni-rich layered cathodes according to their working mechanisms. Moreover, we propose future perspectives of improving the electrolyte performance, which will provide new insights for designing novel electrolytes toward high-performance Ni-rich layered cathodes.