An integrated ultrathin, tip-electrostatic-shielding and inorganic interphase-promoting polymeric electrolyte design for high-performance all-solid-state lithium metal batteries

Abstract

Solid-state lithium metal batteries (SSLMBs) are highly promising for future energy storage systems due to their exceptionally high lithium metal anode capacity and the enhanced safety provided by solid-state electrolytes. However, tip effect-promoted uneven electric field distribution and unstable organic interphases are commonly observed in current polymeric SSLMB systems, which lead to dendritic Li metal deposition and fast capacity decay in the anode. Meanwhile, fabricating ultrathin solid polymer electrolytes remains challenging. Here, we develop an integrated 6-μm-thin polymeric solid-state electrolyte by incorporating a CsNO₃ additive and a commercially available thin porous separator host into a polyethylene oxide solid electrolyte. XPS (X-ray photoelectron spectroscopy) results show that the NO₃⁻ anion contributes to the formation of an inorganic Li₂O, Li₃N, and LiF-dominant, organic-rare interphase, while simulation results illustrate that the tip electrostatic shielding effect from the Cs⁺ cation successfully suppresses dendritic Li growth. As a result of this integrated solid electrolyte design, the Li metal plating/stripping Coulombic efficiency (CE) is significantly improved from 90.1 % to 97.4 %, with Li deposition morphology modified from dendrites to large grain particles. Moreover, the cycling stability of solid-state Li||LFP full cells is improved from 70 % retention after 69 cycles to 70.6 % retention after 400 cycles. This novel integrated solid electrolyte design offers an alternative approach to overcoming the instability of lithium anodes, which is a key challenge in the development of practical and high-performance SSLMB technology.