Constructing stable interface layer for boosting high-voltage cycling performance of single-crystal Ni-rich cathodes

Abstract

Increasing demand for electric vehicles (EVs) worldwide and the requirements for environmental protection have greatly promoted the development of low-Co, Ni-rich layered cathodes due to their high energy density, reasonable cost, and less environmental pollution. Nevertheless, serious performance degradation and safety concerns resulting from structural/interfacial instability under high operating voltages (≥4.3 V) have greatly hindered its commercialization. Herein, we propose a feasible surface modification strategy by introducing a multifunctional Li2SiO3 (LSO) coating layer onto the surface of Co less single-crystalline LiNi0·63Co0·07Mn0·3O2 (NCM) to solve the above challenges. The uniform Li2SiO3 coating layer has a unique three-dimensional (3D) ion diffusion channel, which greatly promotes the transmission of Li+ and alleviates interfacial stress accumulation. Equally important, the electrochemically inert Li2SiO3 coating layer has a stable structure framework with strong Si–O bonds, which inhibit anisotropic particle volume expansion and the occurrence of side reactions during long-term cycling. As a consequence, LSO modified NCM exhibits greatly improved electrochemical properties even at harsh testing conditions and achieves capacity retention of 79.1% after 200 cycles at 25 °C within 2.95–4.5 V in half cells. Furthermore, it provides an outstanding capacity retention of 94.7% after 300 cycles at 25 °C within 2.95–4.4 V when tested in pouch full cells.