High-Performance Li-Ion Batteries Using Nickel-Rich Lithium Nickel Cobalt Aluminium Oxide-Nanocarbon Core-Shell Cathode: In Operando X-ray Diffraction.

Nickel-rich layered, mixed lithium transition-metal oxides have been pursued as a propitious cathode material for the future-generation lithium-ion batteries due to their high energy density and low cost. Nevertheless, acute side reactions between Ni4+ and carbonate electrolyte lead to poor cycling as well as rate performance, which limits their large-scale applications. Here, core-shell like LiNi0.8Co0.15Al0.05O2 (NCA)-carbon composite synthesized by a solvent-free mechanofusion method is reported to solve this issue. Such a core-shell structure exhibits a splendid rate as well as stable cycling when compared to the physically blended NCA. In operando X-ray diffraction studies show that both materials experience anisotropic structural change, i.e., stacking c-axis undergoes a gradual expansion followed by an abrupt shrinkage; meanwhile, the a-axis contracts during the charging process and vice versa. Interestingly, the core-shell material displays a significantly high reversible capacity of 91% in the formation cycle at 0.1C and a retention of 84% at 0.5C after 250 cycles, whereas pristine NCA retains 71%. The robust mechanical force assisted dry coating obtained by the mechanofusion method shows improved electrochemical performance and demonstrates its practical feasibility.