Dramatic enhancement in lithium-ion battery capacity through synergistic effects of electronic transitions in light-assisted organic coordination cathode material Co(bpy)(dhbq)2

Abstract

Integration of photoactive and lithium storing units into a single cathode endows it with notable capacity in the presence of suitable light. However, the interfacial effect between the two materials causes significant loss of photogenerated electrons during their transfer which is one of the biggest obstacles in the development of current photo-assisted rechargeable batteries. In this paper, a bifunctional cobalt-coordinated organic cathode is fabricated by combining 2,2′-bpy and DHBQ via Co by adopting the spin evaporation technique. It optimizes the pristine interfaces of photoactive and lithium storage units into a photoactive unit-metal interface and a metal-lithium storage unit interface through application of Co. In the presence of light, Co causes a strong metal-ligand charge transfer. Meanwhile, ligand-ligand charge transfer also takes place between the multi-ligands. The synergistic effect of these two phenomena offers a discharge capacity of 387 mAh g ^-1 which is significantly higher than that of 316 mAh g ^-1 recorded in the absence of light. The demonstrated design of bifunctional metal-ligand cathode by incorporation of photoactive ligands into lithium storage ligands through applications of metal centers can open the pathways for establishing a new type of photo-assisted lithium-ion batteries with higher efficiency and lower cost.