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 Na 3 V 2 (PO 4 ) 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 NaClO 4 –0.17 M Zn(CH 3 COO) 2 -2 wt % VC electrolyte, was proposed. Based on such an electrolyte, the carbon-coated single crystalline Na 3 V 2 (PO 4 ) 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.