Copper Activation Enabling Reversible Aqueous Cu−ZnS Battery Chemistry

Abstract

AbstractThe aqueous metal‐sulfide batteries (AMSBs) have attracted research interest due to their high capacity, environmentally friendly qualities, and the accessibility of raw materials. However, the design strategies for metal‐sulfide cathode have rarely been reported. Here, the copper‐activated sphalerite in which Zn2+ is substituted by Cu2+ through ion exchange has been introduced for the first time as cathode for aqueous Cu/ZnS batteries. After sphalerite transformed to CuS, a two‐step conversion of CuS→Cu7S4→Cu2S storage mechanism has been proposed. At 0.7 A g−1 current density, the capacity can reach 532.4 mAh g−1 after 100 cycles. When cycled once at a current density of 35 mA g−1, the initial reversible capacity can reach 461 mAh g−1 under 1 A g−1. Furthermore, the assembled Zn//ZnS hybrid ion cell delivers an energy of up to 460 Wh kg−1, which is better than for many AMSBs.