Solar energy has a fluctuating nature, which causes a need for energy storage. Usually, light is harvested by solar cells and the electricity that is generated by these cells is then stored in a battery. This extra step causes energy losses. Photo-active battery electrodes that can be recharged directly by light allow the construction of batteries that avoid these losses and reduce the weight, size, and cost of the overall system. While there are examples of photorechargeable lithium-ion batteries (photo-LIBs), they have issues such as low conversion efficiencies and limited lifetimes.
Michael De Volder, University of Cambridge, UK, and colleagues had previously developed photorechargeable zinc-ion batteries with vanadium pentoxide (V2O5)-based photocathodes that achieved photoconversion efficiencies of ca. 1.2 % . The team has used these cathodes to create in photo-LIBs that achieve conversion efficiencies of ca. 2.6 % with a 455 nm light source. The photoactive cathodes consist of V2O5 nanofibers, poly(3-hexylthiophene-2,5-diyl) (P3HT), and reduced graphene oxide (rGO) and were assembled by mixing these components with polyvinylidene fluoride (PVDF) and drop-casting them onto carbon-felt current collectors.
The team modified standard coin cells by drilling a hole in one side and installing a small glass window to allow light in. The photocathodes were placed under this window, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was used as an electrolyte. The resulting photo-LIBs can be charged using light and achieve higher photoconversion efficiencies than previous photo-LIBs or photorechargeable zinc-ion batteries. They also provide a higher average output voltage (2.88 V) compared with photorechargeable zinc-ion batteries (0.77 V).
- Light Rechargeable Lithium-Ion Batteries Using V2O5 Cathodes,
Buddha Deka Boruah, Bo Wen, Michael De Volder,
Nano Lett. 2021.
-  Photo-rechargeable zinc-ion batteries,
Buddha Deka Boruah, Angus Mathieson, Bo Wen, Sascha Feldmann, Wesley M. Dose, Michael De Volder,
Energy Environ. Sci. 2020.