Protecting lithium metal anode in all‐solid‐state batteries with a composite electrolyte

The volume of the metallic lithium anode in all-solid-state Li metal batteries increases significantly due to the lithium dendrite formation during the battery cycling, and the rough surface of lithium metal also reduces Li-ion transport in Li/electrolyte interface. In this work, we developed a solid polymer composite by adding the low-cost Si3N4 particles to protect the lithium anode in all-solid-state batteries. The Fourier transform infrared spectroscopy (FTIR) data show that the surface of 10 wt % Si3N4 particles interacts with the polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt; the interaction restricts the anion mobility and improves the ionic conductivity (1 × 10−4 S·cm−1) and lithium-ion transference number (0.28) of the composite electrolyte. The lithium metal anode is well protected by the composite electrolyte in all-solid-state cells, including symmetric and Li/LiFePO4 cells. The lithium dendrite growth suppression by this composite electrolyte indicates the possible application of these low-cost composite electrolytes for lithium metal protection.