High-power and high-energy zinc ion cathodes through embedded CNTs current collectors in vanadium oxide

Abstract

Aqueous rechargeable zinc-ion batteries (ZIBs) represent a promising technology for increased adoption in various applications, especially for stationary energy storage purposes. Despite notable advancements in enhancing the capacity of electrode materials for ZIBs, the development of cathodes exhibiting high capacity at the electrode level, with application-relevant mass loadings and prolonged stability, remains challenging. Herein, we introduce composite electrodes consisting of vanadium oxide with an embedded conducting network of carbon nanotubes, reaching 96 wt.% of active material in the full electrode by eliminating binders and metallic foil. Embedding the CNT network results in flexible electrodes with a uniform distribution of active material, electrical conductivity of 3.5 × 10³ S/m (e.g., 0.25 S/m out-of-plane) and high toughness. The resulting composite electrodes demonstrated a high capacity of 350 mAh/g at the electrode level, coupled with prolonged cycling performance both at low (e.g., 98 % retention over 240 at 0.1 A/g) and high current densities (e.g., 87 % over 1500 cycles at 5 A/g). The embedded conducting network within the electrode produces excellent high-rate properties up to 10 A/g (e.g., ∼170 mAh/g) due to the uniform distribution of active material and high internal electrical conductivity. Embedded CNT electrodes translate into a specific energy density of ∼ 290 Wh/kg at the electrode level, which is a 425 % increase compared to conventional ZIB cells with titanium or stainless-steel current collectors.