High Energy, Long Cycle, and Superior Low Temperature Performance Aqueous Na–Zn Hybrid Batteries Enabled by a Low-Cost and Protective Interphase Film-Forming Electrolyte

A hybrid aqueous Na-Zn ion battery derived from the Na₃V₂(PO₄)₃ cathode is one of the most promising systems among aqueous batteries because it exhibits higher energy density than a pure Zn ion battery due to different ion intercalation mechanisms related to various electrolytes. However, it is more difficult to improve the electrochemical performance of the hybrid aqueous Na-Zn ion battery versus Zn ion battery. In addition, searching for suitable protective interphase film-forming electrolyte additives in order to increase cycling stability and developing a new electrolyte recipe to improve the low temperature performance are significant and still big challenges for the hybrid aqueous Na-Zn battery. Herein, the introduction of protective interphase film-forming additives (VC), an economical 10 M NaClO₄-0.17 M Zn(CH₃COO)₂-2 wt % VC electrolyte, was proposed. Based on such an electrolyte, the carbon-coated single crystalline Na₃V₂(PO₄)₃ nanofiber//Zn aqueous Na-Zn hybrid battery involving high energy, long cycle, and outstanding low temperature performance was successfully obtained. For example, it delivered a remarkable output voltage of 1.48 V and excellent cycle stability (retained 84% after 1000 cycles). The capacities were 94.4 mA h/g at 0.2 A/g at -10 °C and 90.0 mA h/g at 0.2 A/g at -20 °C, respectively.