Additive-free nitrile-based gel polymer electrolytes with enhanced interfacial compatibility for Lithium metal batteries

Gel polymer electrolytes (GPEs) combine polymer matrix with plasticizer to enhance safety and ionic conductivity . However, the use of nitrile-based plasticizers in lithium metal batteries (LMBs) is constrained by their poor interfacial stability with lithium metal. Here, we propose a novel nitrile plasticizer , cyclopentane-1,1-dicarbonitrile (CPDCN), which employs a triangular coordination mechanism with Li + through its dual cyano groups . This configuration minimizes free cyano group accumulation at the lithium metal anode (LMA) interface, effectively suppressing parasitic reactions. Furthermore, the fully substituted α-position structure of CPDCN eliminates the reaction of α‑hydrogen (α-H) with lithium metal. The resulting GPE (denoted as PCNE), fabricated from poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) and CPDCN, demonstrates exceptional compatibility with LMA, enabling stable lithium plating/stripping for over 550 h in Li|PCNE_50|Li symmetric cells without additives. The LiFePO 4 |PCNE_50|Li cell delivers an initial discharge capacity of 156.4 mAh g −1 at 0.2C and retains 80% capacity after 750 cycles. Meanwhile, high-voltage LMBs using LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathode achieve 95.9% capacity retention after 200 cycles at 0.1C. This work presents a practical molecular structural design for nitrile-based electrolytes with improved lithium metal compatibility.