Creating electrostatic shielding effects through dual-salt strategy to regulate coordination environment of Li⁺ and realize high-performance all-solid-state lithium metal batteries

Abstract

All-solid-state lithium metal batteries with polymer-ceramic solid electrolytes (PCSE) have garnered significant attention due to their high design flexibility. However, their low ionic conductivity and interfacial issues often impede commercialization. This study uses a Polyethylene Oxide-Li_1.5Al_0.5Ge_1.5(PO₄)₃ electrolyte model and introduces K⁺ to create a dual-salt composite polymer solid electrolyte. By establishing an electrostatic shielding effect and adjusting the Li⁺ coordination environment, the electrolyte's performance is enhanced. Theoretical and experimental results indicate that K⁺ does not participate in electrochemical reactions but instead accumulates in specific regions, promoting uniform Li⁺ deposition. Additionally, competitive coordination interactions (K⁺-TFSI⁻-Li⁺) facilitate in-situ decomposition of TFSI⁻ and PF₆⁻, forming a LiF–Li₃N–Li₂O rich SEI with low impedance. Results show that the symmetric cell achieves stable plating/stripping for 1000 h at a current density of 0.2 mA/cm² without short-circuiting, and it is compatible with both LiFePO₄ (LFP) and high-voltage LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811) cathodes. This study constructs a dual-salt composite polymer solid electrolyte, revealing the interactions between molecules and ions within the electrolyte and laying a foundation for the further development of all-solid-state batteries.