Phase Transition Mediated Solvation Structure Regulation in Quasi-Solid-State Composite Electrolyte for High-Voltage Sodium Batteries.

Quasi-solid-state composite electrolytes (QSSEs) represent a promising approach to fabricating high-energy rechargeable batteries, but their practical implementation is hindered by structural instability and interfacial incompatibility. In this study, a QSSE was prepared with the aid of a molecular reinforcer, thioctic acid, which induces a polymer conformational change to a high-dielectric phase for improved ion transport and strengthens the structural durability, even with rich porosity, due to the strong and dynamic complexing bonds. As a result, the ionic conductivity and electrochemical stability of the QSSE are significantly enhanced to 5.0 × 10- 4 S cm-1 and 5.1 V. Moreover, the greatly reduced activation energy (0.11 eV) and the electrolyte-derived inorganic-rich interphases facilitate ion migration across the electrolyte-electrode interfaces and enable simultaneous stabilization of both cathode and anode with thin and stable protection layers. Accordingly, Na|Na3V2(PO4)3F3 cells assembled with the designed QSSE exhibit excellent rate capability and cycling stability at a high cut-off voltage of 4.4 V (vs. Na+/Na), delivering a capacity of 94.1 mA h g- 1 with 93.4% retention after 600 cycles at 1 C. This work offers a viable strategy for developing high-energy-density batteries.