Lignin Derived Ultra‐Thin All‐Solid Polymer Electrolytes with Three dimensional Single‐ion Nanofiber Ionic Bridge Framework for High Performance Lithium Batteries

Solid-state lithium batteries are promising candidates for the next generation high security and high performance batteries. Here, the lignin derived ultra-thin all-solid composite polymer electrolytes (CPEs) with a thickness of only 13.2 μm, which possessed three dimensional nanofiber ionic bridge networks composed of single-ion lignin based lithium (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, was obtained through electrospinning/spraying and hot-pressing process. The obtained CPE presented high ionic conductivity of 1.3×10-4 S cm-1, excellent oxidative stability of 4.7 V, and satisfactory tensile strength of up to 9.30 MPa. The Li||Li symmetric cell assembled with the CPE can stably cycle more than 6500 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, and Li||CPE|| NCM can also stably cycle more than 70 cycles with a favorable discharge capacity of 132.4 mAh g-1 at 0.2 C and 30 °C. The excellent electrochemical performance was mainly attributed to the reason that the nanofiber ionic bridge network can afford uniformly dispersed single-ion L-Li through electrospinning, which synergized with the LiTFSI well dispersed in PEO to form abundant and efficient three dimensional Li+ transfer channels. Furthermore, the ultra-thin CPE can be compactly attached to the lithium anode, and provided a shorter ion transmission distance between the electrodes, inducing uniform deposition of Li+ at the interface, and inhibiting the lithium dendrites. This work provided a promising strategy to achieve ultra-thin biobased electrolytes with high tensile strength and electrochemical performance for solid-state LIBs. This article is protected by copyright. All rights reserved.