A high-energy-density aqueous dual-ion anode-free Zn battery under cryogenic conditions

Abstract

Achieving high energy density under cryogenic conditions is essential for aqueous Zn batteries to work in extreme environments. Anode-free configuration can improve energy densities of Zn batteries close to their theoretical limit. However, the intrinsic low energy density and complex preparation of the current Zn-rich cathodes severely limit the prospect of aqueous anode-free Zn batteries (AFZBs). Herein, AFZBs with dual-ion chemistry (DAFZBs) are designed to conquer this limitation via replacing Zn-rich cathode by commercially available electrode materials. It works with reversible insertion/extraction of Li⁺ or Na⁺ at cathode and reversible Zn plating/striping at anode. Due to the higher reversible specific capacity and the higher potential derived from the larger Gibbs free energy (ΔG_cathode) of the Li⁺ or Na⁺ intercalation into the cathode host than that of Zn²⁺, the energy densities of the DAFZBs are boosted. Specifically, the LiMn₂O₄ (LMO)||Cu and Na₃V₂(PO4)₃ (NVP)||Cu batteries achieved high discharge voltage of 1.8 and 1.4 V, along with high energy densities of 123.4 and 168.1 Wh kg_{cathode+anode}⁻¹ at 25 °C, respectively. Even at extremely low temperature of −30 °C, the LMO||Cu battery exhibits record-high energy densities of 172.1 Wh kg_{cathode+anode}⁻¹. This work breaks through the energy density limit of traditional AFZBs at cryogenic conditions by employing dual-ion chemistry.