Long-chain fluorocarbon-driven hybrid solid polymer electrolyte for lithium metal batteries

Abstract

The exploration of solid-state lithium metal batteries (SLMBs) with high-performance hybrid polymer electrolytes is in demand for the development of novel energy-storage systems with enhanced safety and high theoretical energy densities. In this study, for the first time, we report the synthesis of P(dodecafluoroheptyl methacrylate-co-methyl methacrylate) (P(DFMA-co-MMA)) as a polymer matrix to provide adsorption sites for Li⁺. Moreover, succinonitrile was introduced to suppress polymer crystallization, and the long fluorocarbon chains connected in series provided long-range channels for Li⁺ transmission. The resultant long-chain-fluorocarbon-driven hybrid solid polymer electrolyte (LFSPE) membranes could afford an exceptional ion conductivity of 6.78 × 10⁻⁴ S cm⁻¹ at 25 °C, with a wide electrochemical stable window (0–4.713 V vs. Li/Li⁺) and high lithium-ion transference number (0.47). The poly(diallyl dimethyl ammonium)-bis(trifluoromethanesulfonyl)imide (PDDA-TFSI) interlayer was exploited to inhibit the side reactions on the Li metal surface and promote homogeneous Li plating. Thus, steady Li plating/stripping in LFSPE could be achieved under an areal capacity of 0.2 mA h cm⁻² for 2000 h. The LiFePO₄ (LFP), LiCoO₂ (LCO) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cells using the modified SLMB design scheme exhibited excellent rate capacity (specific capacity of 138.8, 109.6 and 145.8 mA h g⁻¹ at 1C, respectively) and long-term cycling stability (98.8% capacity retention after 500 cycles for LFP; 81.4% and 71.9% capacity retention after 300 cycles for LCO and NCM811, respectively). This work offers a novel and effective SLMB system with high safety based on a hybrid solid polymer electrolyte.