Aqueous batteries are promising as cheap, safe and green energy storage technologies. In the family of aqueous batteries, Zinc-based alkaline batteries are attractive candidates due to their low cost and high capacity compared with lead-acid and nickel-metal hydride batteries.^1-3 However, the long-term durability of Zinc-based alkaline batteries is hampered by the Zn dendrite formation, which easily causes the internal short of batteries. In order to address this obstacle, a carbon film is developed to serve as flexible current collector for the plating/stripping of Zn. By virtue of this carbon film current collector, Zn can be reversibly plated/stripped at 1 mA cm^-2 at 1 mAh cm^-2 for 100 cycles with the coulombic efficiency over 97% without the formation of Zn dendrite.

Figure1a shows the cycling performance and coulombic efficiency of Zn plating and stripping on carbon film at a current density of 1mA cm^-2 with an areal capacity of 1mAh cm^-2. During each cycle, Zn is deposited on the carbon film at 1 mA cm^-2 for 1 h and then stripped at 1 mA cm^-2 until the potential reaching 0.5 V (vs. Zn²⁺/Zn). The coulombic efficiency is defined as the ratio of Zn removed from carbon film to that deposited during the same cycle. As can be seen, Zn can be stable deposited on and stripped from the carbon film within 100 cycles without short circuit. The initial coulombic efficiency of is 92.6% but it quickly roses up to 97.3% in the 3^rd cycle and is stabled over 97% within 100 cycles. Moreover, from the plating and stripping profiles of Zn in Figure 1b, the potential hysteresis (defined as the difference of stripping/plating average potential in the same cycle) between the plating and stripping is less than 200 mV, indicating a fast electrochemical reaction kinetics. This result demonstrates that this low cost, fast kinetics and high efficiency carbon film shows potential as current collector for aqueous zinc-based batteries.

Acknowledges: The authors greatly acknowledge the financial support from National Natural Science Foundation of China (No. 51622703), and the National Thousand Talents Program of China.

References

1. F. Parker, C. N. Chervin, I. R. Pala, et al., Science, 2017, 356, 415.
2. Pan, Y. Shao, P. Yan, et al., Nature Energy, 2016, 1, 16039.
3. Kundu, B. D. Adams, V. Duffort, et al., Nature Energy, 2016, 1, 16119.