The beneficial effects of black phosphorous modification of the anode current collector in Li-metal free Li2S-based batteries

Li–S batteries assembled without a lithium metal anode can significantly increase the battery specific energy and obviate the safety issue of excess Li metal in the battery. In this study we found that a black phosphorous (BP) modified cooper foil current collector could provide a beneficial anode solid-electrolyte-interface (SEI) to enable the charging and discharging of Li-metal free Li2S-based batteries at higher C rates. The BP modification is effective in several aspects: the lithiophilicity of BP reduces the energy barrier in Li metal deposition and stripping during battery charge and discharge. The reactions between BP and lithium polysulfides also form Li7PS6 in the anode SEI layer. Since Li7PS6 has a high ionic conductivity for Li + diffusion, the Li plating/stripping efficiency is improved. The synergy of the lithiophilicity of BP and a Li7PS6-rich anode interphase layer was demonstrated in Li-metal free Li2S batteries, where the capacity retention over 100 cycles is 64.8% at the 0.2 C rate. The findings here show that current collector modifications should attend to multiple functionalities in order to be effective for the Li-metal free Li2S batteries.