Researchers at the Illinois Institute of Technology and Argonne National Laboratory have developed a new approach for Li-air batteries based on a four-electron reaction process to produce lithium oxide (Li₂O) formation and decomposition, enabling the battery to deliver a much higher energy density compared to current Li-ion technology.

Developing a battery with an energy density comparable to that of gasoline is a long-sought goal in battery research and development. A lithium-air battery based on lithium oxide (Li₂O) formation has such a theoretical potential. Lithium-air batteries offer great promise due to their high energy density and low cost. So far, lithium-air battery demonstrations have been limited to only one- or two-electron reaction processes, resulting in the formation of lithium superoxide (LiO₂) or lithium peroxide (Li2O2), respectively.

The successful implementation of the four-electron reaction in the lithium-air battery relies on the utilization of a solid-state electrolyte combined with a catalyst, trimolybdenum phosphide (Mo₃P).

Schematic shows a lithium-air battery cell consisting of a lithium metal anode, air-based cathode, and solid ceramic polymer electrolyte (CPE). Upon discharge and charge, lithium ions (Li+) go from anode to cathode, then back.

The composite electrolyte embedded with Li₁₀GeP₂S₁₂ nanoparticles exhibits high ionic conductivity and stability and high cycle stability. Low-dose cryogenic transmission electron microscopy carried out at the Center for Nanoscale Materials, a Department of Energy Office of Science user facility, confirms the reaction mechanism, which favors four-electron reaction chemistry by reversible formation and decomposition of Li₂O as the main product.

The research found that the battery is rechargeable for at least 1,000 cycles at room temperature, which represents significant progress toward practical applications of lithium-air batteries.