In-situ reconstruction of spinel interface on Li-rich layered cathode with improved electrochemical performances

摘要

The produced inactive interface during the cycle and poor rate performance are the inevitable obstacles for the practicability of lithium-rich layered cathode. Here, we report that in-situ surface pretreatment technique with hydrazine hydrate can reconstruct epitaxial spinel possessing the rapid lithium ions diffusion path, which primarily includes the leaching of Li+/Ni2+ and redistribution of the metal ions. We confirm the generation of epitaxial spinel heterostructure on the layered matrix by kinds of characterization methods such as transmission electron microscopy and Raman spectroscopy. As a result, the epitaxial spinel substantially promotes the lithium ion diffusion coefficient from 1.98 x 10-11 cm2 s-1 to 3.76 x 10-11 cm2 s-1. Even under a discharge current 5 C, the reversible capacity still reaches up to 171.1 mAh g-1. After 200 cycles at 1 C, the modified cathode delivers a capacity retention of 84.2% with the discharge capacity of 197.8 mAh g-1. The presence of the epitaxial spinel layer exerts a positive effect on the stability of the cathode structure and suppression of side reactions at the interface via exploring the morphology and composition of the cycled cathodes. The in-situ surface reconstruction technology to generate spinel is appealing for promise prospect application of lithium-rich layered cathodes in the future.