UV-Initiated Soft-Tough Multifunctional Gel Polymer Electrolyte Achieves Stable-Cycling Li-Metal Battery

A semi-interpenetrating gel polymer electrolyte (S-GPE) membrane is successfully designed through combining high-molecular polyacrylonitrile (PAN), polyethylene glycol (PEG) oligomers, ethoxylated trimethylolpropane triacrylate (ETPTA) monomers, and silica (SiO₂) nanoparticles as a whole through an ultraviolet (UV) initiating process. The highly polymerized PAN ensures the thermal stability and toughness, while the oligomer of PEG acts as a soft component and facilitates an improved contact between different interfaces. SiO₂ nanoparticles are added with the aim to restrain the crystallinity and improve ionic conductivity. Here, the obtained S-GPE achieves a high ionic conductivity of 8.9 × 10^-4 S cm^-1 at room temperature and effective dendrites inhibition. Hence, the S-GPE shows an eminent stability that enables the Li|S-GPE|Li cell to stably cycle at 6 mA cm^-2 under 3 mA h cm^-2 for over 1000 h without a polarization voltage increase. The Li|S-GPE|LiFePO₄ battery shows a 131.4 mA h g^-1 initial discharge capacity at the first cycle and keeps 93.23% capacity retention after 500 cycles at 0.5 C under room temperature, which is far beyond liquid electrolyte with a conventional PE/PP separator. Prospectively, this work enlightens a promising and optional way in electrolyte design for long-life energy storage devices.