Defect regulation of Co2+ substituting V3+ in Na3V2(PO4)3 for superior sodium storage performance: Experimental and theoretical study

Na3V2(PO4)3 (NVP), possessing stabilized framework and high voltage platform, has attracted extensive attentions in the field of energy storage. However, the low conductivity restricts its further development. Herein, a novel strategy of defect regulation by Co2+ substitution is proposed. Co2+ doping not only generates beneficial hole carries resulting from the p-type doping to accelerate the electronic conductivity, but also favors to expand the interplanar spacing in the internal bulk of NVP system to enhance the ionic transportation. Moreover, theoretical calculation indicates the beneficial Co2+ substitution modifies the electronic structure of NVP to reduce the band gap, as well as decline the energy barrier. Distinctively, the Co0.07-NVP/C composite delivers a high value of 114.4 mA h g−1 at 0.1 C, almost close to its theoretical value (117.6 mA h g−1). It submits a reversible capacity of 104.6 mA h g−1 at 1 C and keeps 100.1 mA h g−1 after 200 cycles with a retention value of 95.70%. Even at 10 C, it also can reveal a capacity of 101.6 mA h g−1 and remains 81.8 mA h g−1 after 1000 cycles.