Zwitterionic-Modified PAN Nanofibrous Membranes for Stable Lithium–Metal Batteries

Abstract

Lithium–metal batteries (LMBs) are the energy storage system of the next generation due to their high theoretical capacity and the lowest electrochemical potential of metallic lithium. Nevertheless, their practical use is limited by uncontrollable growth of the dendrites and extreme instability of the interfaces that can easily short-circuit and be unsafe. This report presents a polyacrylonitrile (PAN)/zwitterionic copolymer (ZP) nanofibrous separator that was prepared by using the electrospinning process. The zwitterionic copolymer that was prepared by Butler through cyclopolymerization of methionine sulfide and phosphonate monomers improves the affinity of the electrolyte, ionic conductivity, and control of Li+ transport with polar groups. Electrospun PAN/ZP blend membranes are highly porous (87%), electrolyte-absorbent (545%), thermally stable, and still mechanically strong. The blend separator offers symmetric Li||Li cells that cycle with low overpotential and have a lifetime exceeding 200 h. Li cross-sections and ex situ SEM of Li surfaces confirm the inhibition of dendritic growth. After 300 cycles at 0.5 C, the LiFePO4 full cells are highly reversible. This is an account of a straightforward scalable process for creating efficient separators in secure, long-lasting LMBs.