Kinetics behavior of single-crystal nickel-rich cathode materials at different cut-off voltages

Since single-crystal nickel-rich cathode material has better electrochemical stability and thermostability than polycrystalline type, considered an attractive replacement, single-crystal has concentrated lots attention in past few years. Herein, a typical single-crystal nickel-rich material Li [NixCoyMn1−x−y]O2 (with 83% Ni content) has been investigated, and the electrochemical property was analyzed at different degrees of structure distortion by modified cut-off voltages. The result reveals that higher cut-off voltage does provide a greater driving force for ion transport, but it also forces more Ni2+ to migrate into the lithium layer, and exacerbates the degree of transition from the ordered to amorphous, which directly damaged the Li+ reversible insertion/extraction ability. For the test sample under high cut-off voltage after 50 cycles, a larger dead region (microcracks) for ion diffusion can be observed and lower lithium diffusion coefficient can be obtained in electrochemical test results. This study explored the connection between ion transport and structural distortion, providing some reference ideas for the further development of electrode materials.