Thermochemical Cyclization Constructs Bridged Dual-Coating of Ni-Rich Layered Oxide Cathodes for High-Energy Li-Ion Batteries.

Enhancing microstructural and electrochemical stabilities of Ni-rich layered oxides is critical for improving the safety and cycle-life of high-energy Li-ion batteries. Here we propose a thermochemical cyclization strategy where heating polyacrylonitrile with LiNiCoMnO can simultaneously construct a cyclized polyacrylonitrile outer layer and a rock-salt bridge-like inner layer, forming a compact dual-coating of LiNiCoMnO. Systematic studies demonstrate that the mild cyclization reaction between polyacrylonitrile and LiNiCoMnO induces a desirable "layered to rock-salt" structural transformation to create a nano-intermedium that acts as the bridge for binding cyclized polyacrylonitrile to layered LiNiCoMnO. Because of the improvement of the structural and electrochemical stability and electrical properties, this cathode design remarkably enhances the cycling performance and rate capability of LiNiCoMnO, showing a high reversible capacity of 183 mAh g and a high capacity retention of 83% after 300 cycles at 1 C rate. Notably, this facile and scalable surface engineering makes Ni-rich cathodes potentially viable for commercialization in high-energy Li-ion batteries.