An MBene-based Colloidal Electrolyte for High Depth-of-Discharge and Energy-Density 2 Ah-Scale Zn Metal Batteries

Sluggish diffusion rate and exceptionally uneven distribution of Zn2+ at the electrode/electrolyte interface under high depth of discharge (DOD) severely limits the advancement of high-energy-density Zn metal batteries (ZMBs). Herein, a hydrated eutectic colloidal electrolyte based on two-dimensional transition metal boride, Mo4/3B2T2 MBene (where T represents -OH and -F), is developed. The good Zn²⁺ affinity of terminal groups of MBene promotes ion diffusion, thus achieves a high Zn²⁺ transference number of 0.91, which significantly enhances and balances the ion concentration at the Zn anode surface, improving the Zn deposition dynamics. As a result, Zn anode with ultrathin thickness of 10 μm demonstrates 900 h of cyclability under ultrahigh DOD of 90%. Additionally, the enlarged Zn||Zn pouch cell with a scale of 10×10 cm2 shows a stable cyclic performance for 500 h at 60% DOD, meanwhile the constructed 2 Ah four-electron Zn||I2 pouch battery delivers an energy density of 158.5 Wh L−1 under the same condition. This work provides a new guideline for the development of high-DOD metal anodes and high-energy-density metal batteries.