Self-Reduced Ag Particles Implanted in PEO Electrolyte Grain Boundaries to Endow Multifunctional Electrochemical Regulation

The low ionic conductivity and high-voltage instability of poly(ethylene oxide) (PEO)-based electrolytes limit their extensive usage in solid-state lithium batteries. Herein, the "win-win-win" design concept has been revealed by incorporating Ag⁺ additives into PEO to simultaneously address these limitations. Specifically, most of the Ag⁺ is reduced to nanoscale Ag⁰ at PEO grain boundaries, boosting the electronic conductivity of PEO by 200 times and effectively tuning the charge transfer impedance at high-voltage cathode interfaces. On the other hand, the formation of a lithophilic Li-Ag alloy layer homogenizes lithium deposition/stripping, allowing the Li||Li cell to undergo stable cycling for 250 cycles at 2 mA cm^-2. Additionally, the residual Ag⁺ also acts as a competitor to coordinate with PEO chains, increasing the ionic conductivity of Li⁺ by approximately 41% to reach 1.69 × 10^-4 S cm^-1 at 60 °C. Benefiting from the synergistic benefits, the capacity retention of LiNi_0.8Co_0.1Mn_0.1O₂||Li cell is improved from 29.2% to 63.5% after 300 cycles at 1 C, and the corresponding pouch cell exhibits outstanding performance over 130 cycles at 0.2 C. These results highlight the effectiveness of silver salt additives in achieving high-performance and durable PEO-based batteries.