Carbon nanohorns/nanotubes: An effective binary conductive additive in the cathode of high energy-density zinc-ion rechargeable batteries

Abstract

Manganese oxide (MnO2) is proven to be an efficient cathode material in zinc-ion batteries (ZIBs). However, its poor electronic conductivity strongly limits the performance of Zn–MnO2 batteries. In order to improve performance beyond typical graphitic carbon additives, a binary conductive additive, a combination of carbon nanohorns (CNHs) and carbon nanotubes (CNTs), is added into the MnO2 electrode to establish high-speed electron-channels in the CNTs/CNHs network with an efficient “line-to-surface-to-point” microstructure. In this electrode, the high aspect-ratio CNTs create a conducting highway for the collected charges, while the CNHs provide extra surface area for electron transfer. Moreover, the specific surface area of the electrode increases due to the introduction of CNHs, which increases the Zn2+ diffusion coefficient. As a result, the corresponding battery reaches a high specific capacity (343 mAh g−1 at 0.3 A g−1), excellent rate performance (191.3 mAh g−1 at 3 A g−1) and long-life cycle. Moreover, it achieves an admirable specific energy density of 466 W h kg−1, together with a peak power density of 9.4 kW kg−1 (normalized to the weight of MnO2), the performance of which is among the best reported ZIBs. This work reveals new pathways to improve the performance of MnO2 cathodes for ZIBs.