Construction of lithium sulfide layer on lithium metal by a facile strategy for improving the cyclic stability of lithium metal batteries

The poor lithium ion conductivity of solid electrolyte interface (SEI) layer limits the improvement of cycling performance of lithium metal batteries. Here, we pre-designed a Li 2 S/Li 2 S 2 inorganic layer to participate into the formation of SEI through a simple one-step melting sulfur strategy. Its high ionic conductivity promotes the rapid and uniform transmission of lithium ion, and effectively inhibits the side reaction and the growth of lithium dendrites. Benefiting from these advantages, Li/Li symmetrical batteries using artificial SEI with Li 2 S/Li 2 S 2 show small polarization voltages (25–40 mV), and can run for nearly 1500 h, which is 2 times than that of bare lithium. Moreover, the application of Li/LiFePO 4 battery can be extended to 235 cycles with a high capacity retention of 90% under high load of 21.6 mg cm −2 and lean electrolyte of 2 µL mg −1 .