Functional lithiophilic polymer modified separator for dendrite-free and pulverization-free lithium metal batteries

Abstract

Severe performance drop and fire risk due to the uneven lithium (Li) dendrite formation and growth during charge/discharge process has been considered as the major obstacle to the practical application of Li metal batteries. So inhibiting dendrite growth and producing a stable and robust solid electrolyte interface (SEI) layer are essential to enable the use of Li metal anodes. In this work, a functional lithiophilic polymer composed of chitosan (CTS), polyethylene oxide (PEO), and poly(triethylene glycol dimethacrylate) (PTEGDMA), was homogeneously deposited on a commercial Celgard separator by combining electrospraying and polymer photopolymerization techniques. The lithiophilic environment offered by the CTS-PEO-PTEGDMA layer enables uniform Li deposition and facilitates the formation of a robust homogeneous SEI layer, thus prevent the formation and growth of Li dendrites. As a result, both Li/Li symmetric cells and LiFePO4/Li full cells deliver significantly enhanced electrochemical performance and cycle life. Even after 1000 cycles, the specific capacity of the modified full cell could be maintained at 65.8 mAh g−1, twice which of the unmodified cell (32.8 mAh g−1). The long-term cycling stability in Li/Li symmetric cells, dendrite-free anodes in SEM images and XPS analysis suggest that the pulverization of the Li anode was effectively suppressed by the lithiophilic polymer layer.