Electrode and Electrolyte Co‐Energy‐Storage Electrochemistry Enables High‐Energy Zn‐S Decoupled Batteries

Abstract In the search for next‐generation green energy storage solutions, Cu‐S electrochemistry has recently gained attraction from the battery community owing to its affordability and exceptionally high specific capacity of 3350 mAh g s −1 . However, the inferior conductivity and substantial volume expansion of the S cathode hinder its cycling stability, while the low output voltage limits its energy density. Herein, a hollow carbon sphere (HCS) is synthesized as a 3D conductive host to achieve a stable S@HCS cathode, which enables an outstanding cycling performance of 2500 cycles (over 9 months). To address the latter, a Zn//S@HCS alkaline‐acid decoupled cell is configured to increase the output voltage from 0.18 to 1.6 V. Moreover, an electrode and electrolyte co‐energy storage mechanism is proposed to offset the reduction in energy density resulting from the extra electrolyte required in Zn//S decoupled cells. When combined, the Zn//S@HCS alkaline‐acid decoupled cell delivers a record energy density of 334 Wh kg −1 based on the mass of the S cathode and CuSO 4 electrolyte. This work tackles the key challenges of Cu‐S electrochemistry and brings new insights into the rational design of decoupled batteries.