Simultaneously Boosting Stability and High-Temperature Performance of Ni-Rich Cathode Materials by a Negative-Thermal-Expansion Fast Ion Conductor

Abstract

Nickel-rich layered oxide cathodes have attracted extensive attention for high-energy batteries due to their high capacity, but face challenges such as structural instability, mechanical degradation, interfacial side reactions, and thermal runaway. To address these issues, a multiple-benefit strategy is proposed to modify LiNi0.92Co0.03Mn0.05O2 (NCM92) using Li1.1La0.1Zr1.9(PO4)3 (LLZP) featuring both high ionic conductivity and negative thermal expansion through a facile way. The NCM92 modified with 3 wt % LLZP (denoted as LLZP3) exhibits the best electrochemical performance. Compared to pristine NCM92, the Li+ diffusion coefficient and the discharge specific capacity at 10 C are, respectively, increased by 94.2 and 19.9%, while the capacity retention ratios are, respectively, enhanced by 26.0 and 23.4 percentage points after 200 cycles at 25 °C and 60 °C. Meanwhile, the strain after cycling at 60 °C and the released heat when first charged to 4.3 V are reduced by 55.6% and 62.4%, respectively. According to multifarious characterizations, LLZP can significantly improve the Li+ diffusion kinetics of NCM92, alleviate released heat and volume expansion, and suppress microcrack formation and side reactions during charge/discharge cycling. Noticeably, LLZP exhibits anisotropic volumetric contraction via in situ absorbing heat to enhance thermal safety and interfacial stability. It provides a universal and practical approach for developing high-performance energy materials.