Lignin Derived Ultrathin All‐Solid Polymer Electrolytes with 3D Single‐Ion Nanofiber Ionic Bridge Framework for High Performance Lithium Batteries

The lignin derived ultrathin all-solid composite polymer electrolyte (CPE) with a thickness of only 13.2 µm, which possess 3D nanofiber ionic bridge networks composed of single-ion lignin-based lithium salt (L-Li) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as the framework, and poly(ethylene oxide)/lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI) as the filler, is obtained through electrospinning/spraying and hot-pressing. t. The Li-symmetric cell assembled with the CPE can stably cycle more than 6000 h under 0.5 mA cm^-2 with little Li dendrites growth. Moreover, the assembled Li||CPE||LiFePO₄ cells can stably cycle over 700 cycles at 0.2 C with a super high initial discharge capacity of 158.5 mAh g^-1 at room temperature, and a favorable capacity of 123 mAh g^-1 at -20 °C for 250 cycles. The excellent electrochemical performance is mainly attributed to the reason that the nanofiber ionic bridge network can afford uniformly dispersed single-ion L-Li through electrospinning, which synergizes with the LiTFSI well dispersed in PEO to form abundant and efficient 3D Li⁺ transfer channels. The ultrathin CPE induces uniform deposition of Li⁺ at the interface, and effectively inhibit the lithium dendrites. This work provides a promising strategy to achieve ultrathin biobased electrolytes for solid-state lithium ion batteries.