Constructing a high-loading cathode via the synergistic effect of carbon nanotubes and ammonium vanadate for high-rate and long-cycle aqueous zinc-ion batteries

Abstract

Overcoming the sluggish Zn²⁺ transport kinetics and engineering high-mass-loading of active material on cathodes are urgent for practical high-performance aqueous zinc ion batteries (AZIBs). Because of their high theoretical capacity, diverse crystal structures and multivalent states, vanadium-based materials are extensively studied for the cathodes of AZIBs. Nevertheless, poor inherent conductivity and structure susceptible to collapse lead to limited cycling stability and low-rate performance. Therefore, in this study, the composite of ammonium vanadate and carbon nanotubes (NH₄V₄O₁₀/(NH₄)₂V₄O₉/CNTs (NVOH_10 %CNT)) is synthesized by a simple hydrothermal method. The CNTs can form conductive networks to the increase conductivity for fast electron transport. At the same time, CNTs can also mitigate the structural collapse of NVOH. Therefore, the NVOH_10 %CNT//Zn cell displays a high specific capacity of 446.2 mAh g⁻¹ at 0.3 A g⁻¹ and 286.1 mAh g⁻¹ even at a high operating current density of 20 A g⁻¹. In addition, the capacity retention is 88.52 % after 5000 cycles at 20 A g⁻¹. Even after 10000 cycles, the specific capacity remains 211.6 mAh g⁻¹. Furthermore, a button cell with a high mass loading of 9.3 mg cm⁻² exhibits a specific capacity of 425.7 mAh g⁻¹ at 0.5 A g⁻¹. In addition, the NVOH_10 %CNT//Zn pouch battery exhibits high area capacity (8.56 mAh cm⁻²). This work demonstrates a new and effective approach to design ammonium vanadate composite materials for cathodes of AZIBs.