Photo-Assisted Li-Se Solid-State Batteries

Conversion cathodes offer significantly higher energy densities over conventional intercalation cathodes. Selenium is a promising material for conversion cathodes due to its higher electronic conductivity, lower reactivity, and comparable volumetric capacity compared to sulfur. In addition, selenium is photoactive, an aspect generally overlooked in Li-Se batteries.<br/>We fabricate thin-film solid-state batteries with selenium as a cathode, lithium phosphorus oxynitride (LiPON) as a solid electrolyte, and a lithium metal anode with capacities greater than 400 mAh g^-1 at 0.1 C. Illuminating the device with visible light increases both ionic and electronic conductivity, improving fast-charging capability. Furthermore, we show that the columbic efficiency is increased to over 100 % due to the additional photo-generated charges within the selenium cathode. Photoactive cathodes therefore offer an emerging opportunity to improve both the electronic and ionic conductivities using light without the need to use other conductive additives.