Highly zincophilic-hydrophobic polyzwitterionic hydrogel electrolyte with strong electronegative sulfobetaine-carboxyl motifs for ultrastable zinc-ion batteries

Abstract

Polyzwitterionic hydrogel electrolytes with good anionic affinity and a well-aligned Zn²⁺ deposition effect are regarded as potential alternatives for propelling zinc-ion batteries (ZIBs). However, their hydrophilic molecular chains show relatively low zincophility and easily transfer H₂O molecules to the Zn surface, resulting in interfacial Zn corrosion and dendrites. Here we design highly zincophilic-hydrophobic polyzwitterionic hydrogel electrolyte (SC-PAM) via the crosslinking of zwitterionic sulfobetaine and carboxyl-rich carboxylated chitosan for ultrastable ZIBs. The zincophilic –SO₃⁻ motifs of zwitterionic sulfobetaine in SC-PAM afford highly Zn²⁺-selective migration channels and homogenize Zn²⁺ flux with a high transference number of 0.90. Meanwhile, strong electronegative carboxyl groups (CO) in carboxylated chitosan strongly anchor H₂O molecules via rich H-bonding interactions to establish a hydrophobic interfacial layer, which shields direct contact between H₂O solvent and the Zn anode to avoid Zn corrosion. As a consequence, the Zn‖SC-PAM‖Cu cell exhibits a high average coulombic efficiency of 99.7% during 7600 cycles, while the Zn‖SC-PAM‖Zn cell shows ultrastable cycling exceeding 7500 hours. Significantly, SC-PAM can be further leveraged to design a state-of-the-art Zn‖SC-PAM‖V₂O₅ full battery with high capacity (372 mAh g⁻¹), large-current tolerance (15 A g⁻¹), and ultralong cycle life (5000 cycles). This work extends the structural engineering landscape of zincophilic-hydrophobic polyzwitterionic hydrogel electrolytes for advanced ZIBs.