Improving the Electrochemical Performance of a Lithium-Rich Layered Cathode with an in Situ Transformed Layered@Spinel@Spinel Heterostructure

Lithium-rich layered oxides have attracted much attention due to their high discharge capacity (>250 mA h·g-1). However, lithium-rich layered cathodes suffer from poor rate capabilities and voltage decay, which seriously limit their practical application. Herein, a unique layered@spinel@spinel double-spinel shell heterostructure is designed and successfully synthesized via coprecipitation and high-temperature solid-phase methods. In particular, lithium-rich layered oxides show good rate capabilities and high capacity retention when the molar amount of cobalt acetate and manganese acetate is 5%. After 100 cycles at 0.2 C, a discharge capacity of 232 mA h g-1 and a capacity retention of 92.7% can be obtained. The superior electrochemical performance of the in situ-transformed Li-rich layered cathode can be attributed to the unique three-dimensional diffusion channels for Li ions of the surface spinel phase. Besides, the in situ-transformed LiCoMnO4 shell can also improve the structural stability of the Li-rich layered oxides by reducing the side reactions and protecting the material from being corroded by the electrolyte. This study provides a strategy for surface modification, which can effectively improve the electrochemical performance of Li-rich layered cathode materials with high performance.