Designing Solvated Double-Layer Polymer Electrolytes with Molecular Interactions Mediated Stable Interfaces for Sodium Ion Batteries.

Unstable cathode-electrolyte and/or anode-electrolyte interface in polymer-based sodium-ion batteries (SIBs) will deteriorate their cycle performance. Herein, a unique solvated double-layer quasi-solid polymer electrolyte (SDL-QSPE) with high Na + ion conductivity is designed to simultaneously improve stability on both cathode and anode sides. Different functional fillers are solvated with plasticizers to improve Na + conductivity and thermal stability. The SDL-QSPE is laminated by cathode- and anode-facing polymer electrolyte to meet the independent interfacial requirements of the two electrodes. The interfacial evolution is elucidated by theoretical calculations and 3D X-ray microtomography analysis. The Na 0.67 Mn 2/3 Ni 1/3 O 2 |SDL-QSPE|Na batteries exhibit 80.4 mAh g -1 after 400 cycles at 1 C with the Coulombic efficiency close to 100 %, which significantly outperforms those batteries using the monolayer-structured QSPE.