Electronic interconnected CoV2O6 to induce boosted reaction kinetics for highly stable sodium-ion half/full batteries

Abstract

It is one of the most common methods to improve the performance of sodium-ion batteries (SIBs) by improving the anodes. Vanadium metal oxides, including cobalt vanadate, are potential substitute as new anode material for SIBs due to their high theoretical capacity, variable crystal structure, synergistic effect and interfacial effect between multiple metals. However, although the specific capacity of such anode material is high, the irreversible capacity is often caused by the phase transition process in the charging and discharging process, which leads to a large amount of capacity attenuation. In addition, poor conductivity also limits the rate performance. In this work, bimetallic CoV2O6 (CVO) nanoparticles were modified by using two-dimensional (2D) reduced graphene oxide (rGO) with facile hydrothermal and heat treatment method. Via this construction, the CVO-rGO owns the advantage of porous electronic interconnected network structure, favoring the Na ions/electrons transportation, and suppressing the phase transition during Na+ (de)insertion. Benefiting from the built structure of CVO-rGO, it exhibits excellent performance in SIBs half and full cells. Specifically, CVO-rGO delivers stable 980 mAh g−1 at 0.1 A g−1 after 500 cycles and 98% capacity retention after 1000 cycles at 1 A g−1. Moreover, as anode in SIBs pouch cell, 84.7 mAh g−1 at 2 A g−1 after 1000 cycles (specific capacity retention: 90.3%) can be achieved. Such superior sodium storage of CVO-rGO is confirmed by reaction kinetics analysis and ex-situ XPS/Raman characterization. This work provides a reference for cobalt vanadium oxide to be used as anode material for high performance SIBs.