Boosting the capacity and life span of Zn-supply cathode in “rocking-chair” aqueous Zn-ion batteries by vanadium–manganese coupling strategy

Abstract

Owing to the scarcity of eminent Zn-supply cathodes, traditional aqueous Zn-ion batteries still pin the hope on Zn-metal anode to supply charge carriers, which induces the formidable issues of dendrite growth and side reactions. Herein, we deploy a zinc vanadium–manganese composite cathode material, Zn2.5Mn0.5V3O8, in which the V–Mn coupling in the spinel matrix supplies the Zn2+ ions and eliminates the common usage of Zn metal anode. In the half-cell test, this cathode delivers a specific capacity of 355 mA·h/g at 200 mA/g and capacity retention of 75.7% after 4500 cycles at 5 A/g. The energy storage mechanism can be summarized as a two-step phase transformation in the first charge process, and the co-intercalation of Zn2+/H+ into host accomplished with a conversion reaction in the subsequent cycles. A Zn-metal free “rocking-chair” aqueous Zn-ion battery is fabricated by using Zn2.5Mn0.5V3O8 as the cathode and anthraquinone as the anode. This full cell exhibits stable cycling performance up to 1000 cycles (80.8% at 200 mA/g and 96.4% at 2.0 A/g). This “rocking-chair” strategy provides a new route to expediate the development of aqueous zinc batteries.