Semi closed coordination structure polymer electrolyte combined in situ interface engineering for lithium batteries

Low ionic conductivity and lithium ion transference number (t_Li+) of solid polymer electrolytes (SPEs) preclude their practical implementation. Adjusting the coordination mode of the lithium ions and the polymer functional groups for improving the performance of SPEs is a great challenge. Herein, a combination of the density functional theory calculations and the molecular dynamics simulations is used to study the coordination structure of the lithium ion and its diffusion property in SPEs, demonstrating that a semi closed O–Li⁺ coordination mode in the poly ether/carbonate electrolyte with shorter ether chains leads to free lithium migration. Based on the theoretical calculations, the synthesized SPE realizes an excellent conductivity of 2.97 × 10⁻⁴ S cm⁻¹ at 30 °C and a high t_Li+ of 0.78, accompanying with good electrochemical stability. In-situ polymerization is introduced to fabricate the solid-state battery, ameliorating the interface of the electrode and SPE. A solid-state LiFePO₄/Li battery demonstrates superior rate capacity and cycling durability (95% capacity retention over 100 cycles) at elevated temperature. In addition, the performance of the battery with high voltage cathode is also evaluated at ambient temperature, maintaining respectable rate capability and cycling ability. The semi closed SPE with loose coordination is a competitive stratagem for improving the performance of solid-state batteries in the future.