Strengthened High-Concentration\nQuasi-Solid Electrolytes\nfor Lithium Metal with Ultralong Stable Cyclability

The\nlithium metal batteries coupled with nickel-rich\nLiNi<sub><i>x</i></sub>Co<sub><i>y</i></sub>Mn<sub>1–<i>x</i>–<i>y</i></sub>O<sub>2</sub> (<i>x</i> > 0.7) cathodes hold promise for surpassing\nthe current\nenergy density limit of lithium-ion batteries. However, conventional\nelectrolytes containing free active solvents are highly susceptible\nto decomposition, particularly at the interfaces of lithium anode\nand high-voltage cathode. Herein, we have developed a composite quasi-solid\nelectrolyte (CQSE) utilizing sulfated Al<sub>2</sub>O<sub>3</sub> (S-Al<sub>2</sub>O<sub>3</sub>)-bridged cellulose triacetate (CTA) to stabilize\nthe interfaces between the electrolyte and electrodes. S-Al<sub>2</sub>O<sub>3</sub> competitively dissociates Li<sup>+</sup> through coordination\ninteractions with anions, facilitating the formation of a distinctive\nsolvation structure characterized by prevalent ion pairs and aggregates.\nIn addition, coordination of S-Al<sub>2</sub>O<sub>3</sub> with CTA\nforms S-Al<sub>2</sub>O<sub>3</sub>-bridged CTA molecular chain networks,\nenhancing the mechanical strength of the CQSE and immobilizing free\nliquid molecules. Consequently, the CQSE demonstrates an enhanced\ntensile strength of up to 7.4 MPa and a high ionic conductivity of\n1.8 × 10<sup>–3</sup> S cm<sup>–1</sup> at room\ntemperature. Furthermore, the CQSE not only suppresses electrode–electrolyte\nside reactions but also enables the formation of an inorganic-rich\nsolid/cathode electrolyte interphase. As a result, the Li|CQSE|LiNi<sub>0.83</sub>Co<sub>0.11</sub>Mn<sub>0.06</sub>O<sub>2</sub> (NCM83)\nbatteries retain 84% capacity after 1000 cycles at 1 C, with the pouch\ncells demonstrating 80% capacity retention after 250 cycles at 0.5\nC.