Tuning structural and electronic properties of recycled vanadium oxides via doping trace impurity for sustainable energy storage

•A novel strategy of utilization of impurity in waste-derived V2O5 was provided.•Recycled vanadium oxides show high surface areas, and low work function values.•The Cr-doped V2O5 delivers high capacities and excellent long cycle stability. To meet the urgent requirement of sustainable energy storage technologies, it is essential to incorporate efficient waste management into designing energy storage materials. Herein, we report an environmentally responsible pathway to utilize the recycled V2O5 from V-Cr slag leaching solution. Because of the fact that trace Cr are existed in the recycled V2O5 from initial leaching solution. Therefore, the Cr-doped V2O5 with different content of Cr was successfully synthesized and the effect of Cr on the structure and electronic characteristics of V2O5 was systematically investigated. The date arising from spectral analyses informs us that the trace Cr doping can result in an expansion of the V2O5 lattice, and lead to the decreasing of the work function values, so aiding in enhancing the electrochemical performance. Owing to the trace Cr doped into V2O5 lattice, the recycled V2O5 shows a high specific capacity of 405.5 mAh g−1 and excellent cycling stability over 2000 cycles. A detailed electrochemical reaction mechanism of Cr-doped V2O5 cathode is investigated through a series of in-depth analyses. Different from conventional recycled strategy, we use the impurity element Cr, which is very difficult to separate from V, and realize the enhancement of the electrochemical performance of the recycled V2O5. Moreover, the practicability of recycled V2O5 is exemplified by fabricating a flexible, quasi-solid-state zinc batteries, and the cell operates well upon deformation. This work provides a new strategy for recycling wasted materials into high value materials for sustainable battery systems.