The use of an oxidized carbon nanotube film to control Zn deposition and eliminate dendrite formation in a Zn ion battery

Aqueous zinc ion batteries are regarded as one of the most promising candidates for large-scale energy storage due to their high safety, cost-effectiveness, and environmental friendliness. However, uncontrolled zinc dendrite growth and side reactions of the zinc anode decrease the stability of Zn batteries. We report the synthesis of an air-oxidized carbon nanotube (O-CNT) film by chemical vapor deposition followed by heat treatment in air which is used as a protective layer on the Zn foil to suppress zinc dendrite growth. The increase in the hydrophilicity of the O-CNT film caused by air oxidation facilitates zinc deposition between the film and the anode instead of deposition on the film surface. The porous structure of the O-CNT film homogenizes the Zn 2+ ion flux and the electric field on the surface of the Zn foil, leading to the uniform deposition of Zn. As a result, a O-CNT@Zn symmetric cell has a much better cycling stability with a life of more than 3000 h at 1 mA cm −2 with a capacity of 1 mAh cm −2 , and values of more than 2000 h and 1 mAh cm −2 at 5 mA cm −2 . In addition, a O-CNT@Zn || Mn 2+ inserted hydrated vanadium pentoxide (MnVOH) full cell has a better rate performance than a Zn || MnVOH cell, achieving a high discharge capacity of 194 mAh g −1 at a high current density of 8 A g −1 . In a long-term cycling test, the O-CNT@Zn || MnVOH full cell has a capacity retention of 58.8% after 2000 cycles at a current density of 5 A·g −1 .