Construction of three-dimensional conductive network layer by graphene and vanadium oxide composite for high performance long life low temperature aqueous zinc ion batteries

Layered vanadium-based materials are considered to be the most promising cathode materials for aqueous zinc ion batteries (AZIBs) due to their abundant valence changes and high theoretical capacity. However, low intrinsic conductivity, poor low temperature performance and generally poor cycle life hinder their further application. This study proposes a 3D conductive network by compositing vanadium-based materials with graphene to improve the conductivity for rapid electron transfer. Meanwhile, the interleaving of vanadium-based materials with the conductive network of graphene constructs a buffer layer, which can effectively mitigate the structural collapse caused by Zn 2+ insertion/extraction during the charge and discharge processes, and significantly increase the long cycle life of the battery. The H 2 V 3 O 8 /rGO conductive network buffer layer is directly synthesized by a one-step hydrothermal method. The H 2 V 3 O 8 /rGO-100//Zn batteries show a specific capacity of up to 528.3 mAh/g at 0.1 A/g. Even at a high working current density of 20 A/g, the specific capacity is still 137.2 mAh/g, and it can remain 88.8 % after 12,000 cycles. Moreover, at the low temperature of −20 °C, the H 2 V 3 O 8 /rGO-100//Zn still maintain a high specific capacity of 346.6 mAh/g at 0.1 A/g, and its specific capacity can remain 86.2 % after 20,000 cycles at 10 A/g. Even at −30 °C, it can stably work for 3,000 cycles at 1 A/g with almost no capacity degradation, showing good low temperature adaptability. Therefore, the present work provides a novelty strategy of designing cathode materials for ZIBs with excellent performance.