Photo-Assisted Charge–Discharge Behavior of NMC622 Cathode

Abstract

In this study, a nitrogen (N)-doped graphene film was synthesized on copper foil via chemical vapor deposition (CVD) and employed as a photocatalytic electrode for the photo-assisted charging and discharging of lithium-ion batteries (LIBs). By integrating the photocatalyst as a separate electrode and allowing the cathode to function solely in its conventional role, this configuration mitigated the long-term degradation of light-harvesting efficiency commonly observed in semiconductor-based cathodes and eliminated the constraint of using only semiconductor materials in LIBs. The photo-charging response of the LIB under 1 Sun illumination yielded a photo-conversion efficiency (η%) of 0.152% for the N-doped graphene. Photo-assisted operation enhanced the discharge capacity by at least 15%, improved capacity retention to 90%, and maintained a Coulombic efficiency of 100% over 100 cycles in NMC622 half-cells. The photo-generated electrons effectively accelerated interfacial charge transfer kinetics, thereby facilitating redox reactions at the electrode–electrolyte interface during cycling. Overall, this photo-assisted strategy not only improves LIB performance but also offers a promising route for integrating solar energy conversion directly into energy storage technologies.