Multi-scale stabilization of high-voltage LiCoO₂ enabled by nanoscale solid electrolyte coating

LiCoO₂ (LCO) possess a high theoretical specific capacity of 274 mAh g⁻¹, and currently LCO charged to 4.48 ​V with a capacity of ~190–195 mAh g⁻¹ is penetrating the commercial markets. Scalable strategies to further enhance the performance of LCO are highly attractive. Here, we develop a scalable ball-milling and sintering method to tackle this long-standing challenge by modifying LCO surface with only 1.5–3.5% ceramic solid electrolyte nanoparticles, specifically Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) as an example. Consequently, the atomic-to-meso multiscale structural stabilities have been significantly improved, even with a high cut-off voltage of 4.5 ​V vs. Li/Li⁺, leading to excellent electrochemical stabilities. The nano-LAGP modified Li|LCO cell exhibits high discharge capacity of 196 mAh g⁻¹ at 0.1 ​C, capacity retention of 88% over 400 cycles, and remarkably enhanced rate capability (163 mAh g⁻¹ at 6 ​C). These results show significant improvement compared to the Li|LCO cells. The as-prepared graphite|LAGP-LCO full cells also show steady cycling with 80.4% capacity retention after 200 cycles with a voltage cut-off of 4.45 ​V. This work provides a simple and scalable approach to achieve stable cycling of LCO at high voltage with high energy density.