A high-throughput ion siphon neutralizing space charge layer towards high-rate ultrastable zinc anode chemistry

Space charge layer (SCL) usually aggravates Zn dendrite growth and side reactions, greatly shortening lifespan of Zn anode in aqueous electrolytes, especially under high-rate operation. Traditional interfacial functional layers, despite efficacy in inhibiting dendrites and side reactions, usually cause extra electrochemical polarization due to the failure to neutralize the SCL. Herein, we initiate an electron sponge-based solid electrolyte interphase (SEI) with redox activity to solve this issue. During Zn plating/stripping, this SEI functions as a high-throughput “ion siphon” between bulk electrolyte and anode/electrolyte interface, remarkably neutralizing the negative effect of SCL. In situ Raman spectroscopy, distribution of relaxation times (DRT), and phase-field simulations strongly corroborate the “ion siphon” functionality, which is realized by adding only 2 mM K₆V₁₀O₂₈·9 H₂O (KVO) into ZnSO₄ electrolytes. Consequently, symmetrical Zn cells with redox SEIs displays evidently lowered polarization at high rates and long-term cyclability (over 1200 h at 10 mA cm⁻²/1 mA h cm⁻²). Zn-ion hybrid capacitor (ZIHC) assembled with activated carbon (cathode) delivers 2-fold higher capacity than that in ZnSO₄ electrolytes at 10 A g⁻¹, with a 92.4 % retention after 80000 cycles. This work unlocks redox SEI as high-throughput “ion siphon” to neutralize SCL, which could apply to other aqueous metal-based energy-storage systems.