Designing Effective Electronic Barriers at Grain Boundaries in Garnet for Improved Cycling Performance in Solid-State Lithium Batteries

Solid-state lithium batteries (SSLBs) have emerged as a promising successor to conventional lithium batteries owing to their outstanding safety and elevated energy storage capabilities. Among various solid electrolytes used in SSLBs, Li₇La₃Zr₂O₁₂ (LLZO) is renowned for its superior performance. However, its high electronic conductivity, especially at grain boundaries, promotes lithium dendrite formation, compromising battery performance. To address this issue, we engineered continuous grain boundaries with electron–blocking properties in LLZO to inhibit lithium dendrite growth. Due to the limited incorporation of Cl into the LLZO lattice, excess LiCl accumulates at grain boundaries, effectively restricting electron migration. This approach avoids excessive doping of secondary-phase elements into the LLZO lattice, which could degrade the grain properties. After modification, symmetric lithium batteries with LiCl–LLZO exhibit an increased critical current density from 0.4 to 0.8 mA·cm^–2 (time-constant mode) and operate stably for over 2000 h at 0.3 mA·cm^–2. The batteries using LiFePO₄ as the cathode achieve 89.7% capacity retention (133.5 mAh·g^–1) after 200 cycles at room temperature and 0.2 C. These findings confirm that this strategy successfully hinders lithium dendrite growth and enhances battery performance.