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

Abstract 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.