Template-Assisted Photopolymerized Single- and Dual-Ion Conducting Solid Polymer Electrolytes for Lithium Metal Batteries

Lithium metal batteries hold significant potential for achieving higher energy densities. However, safety concerns about using liquid electrolytes have hindered their path to widespread commercialization. Solid polymer electrolytes (SPE) offer enhanced safety and improved energy performance. Here, we developed and synthesized a solid polymer electrolyte by photopolymerization using urethane dimethacrylate as a cross-linking agent and poly(ethylene glycol) methacrylate combined with polyglyme, supported on a thin electrospun polyacrylonitrile (PAN) membrane. The nature and properties of electrolytes were investigated in dual-ion conducting (DICE) and single-ion conducting (SICE) lithium salt configurations. The dual-ion system exhibited a high ionic conductivity of 1.2 × 10 –4 S/cm and a lithium-ion transference number of 0.35. In contrast, the single-ion conducting system demonstrated an ionic conductivity of 1.8 × 10 –5 S/cm at room temperature and a superior transference number of 0.75. Our results show that in symmetric cells (Li 0 |SPE|Li 0 ), SICE achieved a critical current density that was higher than that of DICE due to effective polarization suppression. We also find that the full cells paired with LiFePO 4 (LFP) cathodes using DICE performed poorly compared to SICE. Li 0 |SICE|LFP delivered a stable capacity of approximately 90 mAh/g after 150 cycles at a 0.5C rate at room temperature. Overall, this work presents a systematic study of dual-ion and single-ion conducting electrolytes with the same polymer system. Our findings identify key attributes to the performance and demonstrate the effectiveness of the proposed electrolyte systems in improving lithium metal batteries.