Boosting the Capacity and Life-Span of Zn-Supplied Cathode in 'Rocking-Chair' Aqueous Zn-Ion Batteries by Vanadium-Manganese Coupling Strategy

Abstract

Owing to the scarcity of eminent Zn-supplied cathodes, traditional aqueous Zn-ion batteries (AZIBs) still pins the hope on unstable Zn-metal anode to supply charge carriers, thus suffering from the dendrite growth and side reactions. Herein, by vanadium-manganese coupling in the spinel matrix, Zn2.5Mn0.5V3O8, a Zn2+ supplied cathode material with outstanding performance, has been prepared to completely get rid of the dependence on Zn-metal anode. Concretely, it delivers a high specific capacity of 355 mA•h g-1 at 200 mA g-1 and comforting retention of 75.7% after 4500 cycles at 5 A g-1. The energy storage mechanism can be summarized as two-step phase transformation in the first charge process, and the intercalation of Zn2+/H+ into host structure accomplished with a conversion reaction in the subsequent cycles. After discarding the Zn-metal anode, a “rocking-chair” AZIB of Zn2.5Mn0.5V3O8 // anthraquinone has been established, in which Zn2.5Mn0.5V3O8 exhibits the superb specific capacities (190.9 mA•h g-1 at 200 mA g-1) and stable cycling performance (80.8% after 1000 cycles at 200 mA g-1 and 96.4% after 1000 cycles at 2.0 A g-1). This work may accelerate the development of both traditional and “rocking-chair” aqueous batteries.

Keywords: rocking-chair, aqueous Zn-ion battery, vanadium-manganese coupling, Zn-supplied cathode, cycle stability