Tuning electronic properties of NiCo2S4 nanofibers through phosphorous doping for optimized oxygen reduction and evolution reactions in Li-O2 batteries

Development of rechargeable Li-O2 batteries is remarkable in the field of electrical energy conversion and storage facilities, which could deliver a much higher theoretical energy density than commercial Li-ion batteries counterparts. Their research progress is constrained by the kinetic barriers of electrocatalytic reactions, which impede further advancements. This present work employed hydrothermal and phosphidation methods to fabricate P-doped NiCo2S4 nanofibers, which are used as cathode catalysts for Li-O2 batteries. It is demonstrated that incorporating P heteroatoms could be beneficial for facilitating charge diffusion on NiCo2S4 catalysts, significantly boosting the reaction kinetics. This was accomplished by modulating the affinity for intermediates and regulating the reversible formation and decomposition of thin film Li2O2 during the discharge and charge processes. As predicted, P-doped NiCo2S4 cathodes exhibit excellent electrochemical performance for Li-O2 electrocatalysis. This study deepens the understanding of the correlations between electronic configurations of heteroatom-doped sulfides and their electrocatalytic capabilities in Li-O2 batteries.