A three-in-one strategy enables improved kinetics in an LLZTO solid electrolyte for Li-CO2 batteries with high energy efficiency†

Solid-state Li-CO₂ batteries possess unique merits, including high environmental friendliness, extremely high energy density, and wide operational temperature range. In this work, we used the garnet-type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) as the solid electrolyte for Li-CO₂ batteries. By a simple solid-state reaction under vacuum, LLZTO was tightly composited with organic materials. Detailed analysis confirms that a three-in-one effect was achieved, resulting in additional Li⁺ migration pathways, improved mechanical properties of the electrolyte, and more active sites for Li₂CO₃ decomposition. This contributes to accelerated Li⁺ transport and fast CO₂ reaction kinetics. A solid-state Li-CO₂ cell was assembled using a Ru@C cathode and an integrated layer of LLZTO@PVDF interfaced with an artificial molten salt. An exceptionally low charging overpotential (below 3.0 V) was achieved, maintaining a charge potential retention rate of over 99%. This work introduces LLZTO as a promising electrolyte for solid-state Li-CO₂ batteries, shedding light on the advancement of next-generation Li-CO₂ battery technologies.