A Replacement Reaction Enabled Interdigitated Metal/Solid Electrolyte Architecture for Battery Cycling at 20 mA cm^–2 and 20 mAh cm^–2

Metal anodes represent as a prime choice for the coming generation rechargeable batteries with high energy density. However, daunting challenges including electrode volume variation and inevitable side reactions preclude them from becoming a viable technology. Here, a facile replacement reaction was employed to fabricate a three-dimensional (3D) interdigitated metal/solid electrolyte composite electrode, which not only provides a stable host structure for buffering the volume change within the composite but also prevents side reactions by avoiding the direct contact between active metal and liquid electrolyte. As a proof-of-concept demonstration, a 3D interdigitated zinc (Zn) metal/solid electrolyte architecture was fabricated via a galvanic replacement reaction between Zn metal foil and indium (In) chloride solution followed by electrochemical activation, featuring the interdigitation between metallic Zn and amorphous indium hydroxide sulfate (IHS) with high Zn²⁺ conductivity (56.9 ± 1.8 mS cm^–1), large Zn²⁺ transference number (0.55), and high electronic resistivity [(2.08 ± 0.01) × 10³ Ω cm]. The as-designed Zn/IHS electrode sustained stable electrochemical Zn plating/stripping over 700 cycles with a record-low overpotential of 8 mV at 1 mA cm^–2 and 0.5 mAh cm^–2. More impressively, it displayed cycle-stable performance with low overpotential of 10 mV under ultrahigh current density and areal capacity (20 mA cm^–2, 20 mAh cm^–2), which outperformed all the reported Zn metal electrodes in mild aqueous electrolyte. The fabrication of interdigitated metal/solid electrolyte was generalized to other metal pairs, including Zn/Sn and Zn/Co, which provide inspiration for next-generation Zn metal batteries with high energy density and reversibility.