Tailoring the hydrophobicity and zincophilicity of poly(ionic liquid) solid–electrolyte interphases for ultra-stable aqueous zinc batteries

Abstract

Despite the enormous potential of zinc metal as an anode material for cost-competitive and safer power sources, the practical application of aqueous zinc batteries (AZIBs) has been plagued by uncontrollable detrimental side reactions and dendrite growth. To tackle these challenges, we propose a novel design strategy that focuses on balancing the hydrophobicity and zincophilicity of poly(ionic liquid) (PIL) solid–electrolyte interphases (SEIs). PILs with the same cation ([VBIm]⁺) but different anions (BF₄⁻, TFO⁻, TFSI⁻) were polymerized on Zn electrodes to form artificial SEI layers with adjustable hydrophobicity. The hydrophobicity of the PIL SEIs leads to the formation of a uniform surface, which is beneficial for eliminating dendrites and inhibiting side reactions. As a result, the Zn‖[PVBIm][TFSI]@Ti cell exhibits a significantly improved coulombic efficiency of 99.61%. Nevertheless, it is important to note that the enhanced hydrophobicity, which contributes to benefits such as better coulombic efficiency, also introduces an inevitable risk of compromised zinc kinetics. To address this trade-off, a zwitterionic PIL, [PVIPS][Zn(TFSI)₂], with a zincophilicity group (–SO₃⁻) was proposed. This approach substantially improves the reversibility and long-term stability of Zn anodes, as evidenced by the outstanding capacity retention of the [PVIPS][Zn(TFSI)₂]@Zn‖PANI full cell (81.32% after 2000 cycles) and 13 times longer life of symmetrical cells (over 1950 h at 1.0 mA cm⁻²/1.0 mA h cm⁻²) compared to bare Zn symmetrical cells.