A hybrid electrolyte comprising a high content of H2O for a lithium metal cell is reported. At high LiFSI salt concentration, the N-methyl-N-propyl-piperidinium bis(fluorosulfonyl) imide (PMpipFSI) electrolyte can tolerate up to 1 M H2O addition without sacrificing its redox stability on both lithium nickel manganese cobalt oxide (NMC) cathode and lithium metal anode. Molecular dynamics simulations revealed the underpinned mechanism that, at high salt concentrations, H2O molecules are embedded in the Li+, PMpip+, and FSI- bulk as a structural material with a strong solvation with Li+ and are orderly distributed at the surface of both electrodes. This electrolyte eliminates the critical moisture controls required for the state-of-the-art (SOA) carbonate/LiPF6 electrolyte, electrode, separator and cell assembly, thus significantly reducing the cost of the mass production of the batteries.
Keywords: Li metal battery; environmentally benign; high voltage stability; hybrid electrolyte; molecular dynamics simulation.