Structural and Electrochemical Study of Hierarchical LiNi_1/3Co_1/3Mn_1/3O₂ Cathode Material for Lithium-Ion Batteries

In this study, a facile nanoetching-template route is developed to synthesize porous nanomicrohierarchical LiNi_1/3Co_1/3Mn_1/3O₂ microspheres with diameters below 1.5 μm, using porous CoMnO₃ binary oxide microspheres as the template. The unique morphology of CoMnO₃ template originates from the contraction effect during the oxidative decomposition of Ca_0.2Mn_0.4Co_0.4CO₃ precursors and is further improved by selectively removing calcium carbonate with a nanoetching process after calcination. The as-synthesized LiNi_1/3Co_1/3Mn_1/3O₂ microsphere, composed of numerous primary particles and pores with size of dozens of nanometers, illustrates a well-assembled porous nanomicrohierarchical structure. When used as the cathode material for lithium-ion batteries, the as-synthesized microspheres exhibit remarkably enhanced electrochemical performances with higher capacity, excellent cycling stability, and better rate capability, compared with the bulk counterpart. Specifically, hierarchical LiNi_1/3Co_1/3Mn_1/3O₂ achieves a high discharge capacity of 159.6 mA h g^-1 at 0.2 C with 98.7% capacity retention after 75 cycles and 133.2 mA h g^-1 at 1 C with 90% capacity retention after 100 cycles. A high discharge capacity of 135.5 mA h g^-1 even at a high current of 750 mA g^-1 (5 C) is also achieved. The nanoetching-template method can provide a general approach to improve cycling stability and rate capability of high capacity cathode materials for lithium-ion batteries.