Revealing the specific role of sulfide and nano-alumina in composite solid-state electrolytes for performance-reinforced ether-nitrile copolymers

Composite solid-state electrolytes represent a critical pathway that balances the interface compatibility and lithium-ion conductivity in all-solid-state batteries. The quest for stable and highly ion-conductive combinations between polymers and fillers is vital, but blind attempts are often made due to a lack of understanding of the mechanisms involved in the interaction between polymers and fillers. Herein, we employ in-situ polymerization to prepare a polymer based on an ether-nitrile copolymer with high cathode stability as the foundation and discuss the performance enhancement mechanisms of argyrodite and nano-alumina. With 1% content of sulfide interacting with the polymer at the two-phase interface, the local enhancement of lithium-ion migration capability can be achieved, avoiding the reduction in capacity due to the low ion conductivity of the passivation layer during cycling. The capacity retention after 50 cycles at 0.5 C increases from 83.5% to 94.4%. Nano-alumina, through anchoring the anions and interface inhibition functions, eventually poses an initial discharge capacity of 136.8 mA h g−1 at 0.5 C and extends the cycling time to 1000 h without short-circuiting in lithium metal batteries. Through the combined action of dual fillers on the composite solid-state electrolyte, promising insights are provided for future material design.