Simultaneously fabricating homogeneous nanostructured ionic and electronic pathways for layered lithium-rich oxides

Abstract

Layered Li-rich oxides (LLROs) have been considered as promising cathodes for next-generation Li-ion batteries due to their low cost and high reversible capacity. However, drawbacks such as voltage decay and poor cycle & rate performance hinder their commercialization. These problems are mainly related to the interface reaction and herein we fabricate nanostructured ionic and electronic bicontinuous pathways for Li1.2Mn0.6Ni0.2O2 simultaneously by modifying the cyclized-polyacrylonitrile (c-PAN) on the surface. This unique design constructs spinel structure on the surface of layered materials as the 3D pathway for Li-ions and conductive framework for electrons to transfer from the current collector through the acetylene black to the surface of every single particle as well, therefore providing both ionic and electronic pathways. Electrochemical tests shows that the cycle & rate performances of the material are significantly improved. After 80 cycles at 0.1C (1C = 250 mA g−1), the capacity retention reaches 97.7%. The results identify that the conductive modification is conducive to maintain the capacity from the spinel phase and control the amorphization of the material, thereby helping to get remarkable cycle performance. We also propose the mechanism of spinel phase formation. This bicontinuous pathways design opens up significant opportunities for the novel design of lithium-rich oxides.