Potassium phosphate monobasic induced decoration from the surface into the bulk lattice for Ni-rich cathode materials with enhanced cell performance

Abstract

The interfacial instability and intrinsic structural degradation of cathodes, which cause performance loss and even a safety hazard, are a critical challenge in Ni-rich cathodes during long-term cycling. Herein, potassium phosphate monobasic modified LiNi_0.8Co_0.1Mn_0.1O₂, whereby a Li₃PO₄ coating layer coupled with trace-levels of co-doped K⁺ and PO₄³⁻ are synchronously constructed, was successfully synthesized via a one-step calcination process at high temperature. Impressively, the optimized 2@KP-NCM delivered superior electrochemical performance, particularly at high rate and elevated temperature. High capacity retention rates of 90.6% at a 5C-rate at room temperature after 200 cycles and 92% at a 1C-rate at 55 °C after 100 cycles in the voltage range of 3.0–4.4 V were reached, and these are clearly higher than those of the pristine cathode (only 73.4% and 51%, respectively). Such a great improvement on the cycling stability is mainly attributed to the pillaring effect of doped-ions on stabilizing the layered structure and suppressing the deleterious irreversible phase-transition as well as the interfacial protective layer effectively protecting the active core cathode from the chemical attack of side products.