A reversible solar photothermal Li-CO2 battery enabled by engineering 3D plasmonic Cr-N-Ru catalysts assembled on carbon-free Si NP cathode

Lithium-carbon dioxide (Li-CO 2 ) batteries using high ion-conductive inorganic molten salt electrolytes, as a kind of promising carbon–neutral technology, have attracted much attention due to the high safety and high energy density. However, sluggish CO 2 reduction reaction (CO 2 RR) and evolution reaction (CO 2 ER) kinetics at cathodes make these batteries losing most of their capacity and power. Here, by engineering the carbon-free three-dimensional (3D) Cr-N-Ru catalysts on silicon nanopillars (Si NP) cathodes, we report a reversible solar photothermal (SPT) molten salt Li-CO 2 battery where solar energy can be efficiently harvested (over 90 % absorption rate from 300 nm to 2500 nm), concentrated and converted to heat. Theoretical simulations support that the 3D Cr-N-Ru catalysts exhibit lower energy barrier and more effectively catalyze the CO 2 RR and CO 2 ER process compared to individual Ru or CrN catalyst. The SPT Li-CO 2 battery shows a reversible cycle lifespan of 83 cycles with lower charge potential (3.2 V) and higher energy efficiency of 72 %, corresponding to ∼ 0.9 V potential gap, than the one using conventional Ru catalysts assembled on Si NP cathode. This battery technology paves the way for developing the next-generation safe and high-energy–density energy storage batteries with carbon–neutral effect.