Constructing high-performance solid-state electrolyte interface and anchoring residual solvents for long-cycle lithium-metal batteries

PVDF-based polymer electrolytes are particularly interesting due to their high ionic conductivity. However, the residual solvent N , N -dimethylformamide (DMF) in the electrolyte tends to decompose on the surface of lithium metal anodes, leading to numerous organic small molecules that deteriorate the solid electrolyte interface (SEI) and limit their application in lithium metal batteries. In this work, a composite solid electrolyte (CSE) is fabricated by chitosan (CHI@Mg), which adsorbs Mg 2+ , as a filler into a PVDF-HFP electrolyte. It has been found that the abundance of -OH, O , and -NH₂ groups in chitosan can facilitate the dissociation of LiTFSI. Additionally, -OH and -NH₂ groups can also anchor residual DMF in the electrolyte to weaken the solvation coordination between Li + and DMF, this effectively inhibits the decomposition of DMF on lithium metal, resulting in improved interfacial stability. Moreover, the Mg 2+ absorbed by chitosan can be conveyed to the lithium anode, participate in the formation of the SEI layer and construct MgF₂-SEI, which facilitate uniform lithium deposition and restrict lithium dendrite growth. Due to the CHI@Mg anchored DMF and construction of the MgF 2 -SEI, the Li||LiFePO₄ battery demonstrates an impressive capacity retention rate of 86.6 % after 1000 cycles at a 2C rate. Additionally, the Li||LiNi 0.7 Co₀.₁Mn₀.₂O₂ cells maintain a capacity retention of 89.2 % after 100 cycles at a cutoff voltage of 4.4 V. This work provides a valuable exploration for improving the interfacial stability between PVDF-HFP-based electrolytes and lithium-metal anodes and promoting the development of solid-state lithium metal batteries.