Local electrostatic field achieved by charge redistribution for stable solid-state lithium metal batteries.

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based solid-state lithium batteries (SSLBs) possess excellent safety and high energy density, but they suffer from sluggish Li+ transport and unstable interphase. A fluorinated covalent organic framework (F-COF) is fabricated and integrated into PVDF-HFP-based solid polymer electrolytes to tackle these issues. The strongly electron-withdrawing fluorine groups can realize the charge redistribution, thereby modulating the local electrostatic environment. This modulation promotes lithium salt dissociation, effectively enabling synergistic dual-ion regulation and suppressing concentration polarization. Meanwhile, F-COF induces the transition of PVDF-HFP from the α-phase to the polar β-phase to reduce polymer crystallinity and build fast ion-transport channels. Furthermore, F-COF injects electrons into TFSI- through anion-π interactions, thereby facilitating the breakage of C-F bonds to obtain a stable LiF-rich SEI film. Consequently, a high ionic conductivity of 1.34 × 10-3 S cm-1 is obtained for the F-COF@PVDF-HFP electrolyte. Li|F-COF@PVDF-HFP|Li cells demonstrate ultra-stable cycling for over 4400 h. LFP|F-COF@PVDF-HFP|Li delivers stable cycling performance for more than 400 cycles, while the LCO|F-COF@PVDF-HFP|Li maintains stable cycling beyond 300 cycles. This study develops a molecular design strategy to regulate the local electrostatic environment for SSLBs.