Polymer-Laden Composite Lignin-Based Electrolyte Membrane for High-Performance Lithium Batteries

Lignin is an eco-friendly, low-cost, and abundant natural biopolymer. However, few studies have explored the potential application of lignin as electrolyte matrix for lithium-ion batteries or obtained excellent cell performance using lignin-based electrolyte. In this paper, lignin and poly(N-vinylimidazole)-co-poly(poly(ethylene glycol) methyl ether methacrylate) are mixed thoroughly in water, then a free-standing lignin-based film is obtained by casting and drying. The resulting film shows obviously higher mechanical strength (over 10 times) than that of the pure lignin film due to the construction of internal physical cross-linking network. Through activation of the prepared film by organic electrolyte, the membrane exhibits superior electrochemical performances (such as outstanding lithium-ion transfer number (0.63) and the ability to inhibit the growth of lithium dendrites). As a result, the LiFePO4/lignin-based electrolyte/Li cell presents excellent long cycle performance (∼150 mAh g–1 at 1 C more than 450 cycles) and rate capacity (110 mAh g–1 at 10 C) at room temperature (RT), which is better than that of the cells using a commercial separator. Moreover, the LiCoO2/lignin-based electrolyte/Li cell also shows superior cell performance at RT. Thus, the lignin-based electrolyte with the outstanding comprehensive property has the potential to replace separator and to be widely applied in high-performance and high-safety LIBs.