Aqueous Zn-ion batteries (ZIBs) are very attractive owing to their high safety and low cost. Among various cathode materials, organic materials-based electrodes incorporating various redox functional groups have gained significant attention in the field of ZIBs due to their benefits of a tunable structural design, facility, eco-friendly, and possibility of multivalent energy storage. Herein, we demonstrate the nanostructured organic active materials deposited onto the CNT networks (HyPT@ CNT) for flexible ZIBs. This HyPT nanorods were obtained reassemblying the herringbone structured 3,4,9,10-tetracarboxylic dianhydride through a hydrothermal process in the presence of acid. These HyPT@CNT hybrids were electronically conductive and redox active, as well as could be fabricated into a flexible electrode achieving flexibility from mechanical integrity of robust networked structure. The as-fabricated flexible ZIBs delivered the high capacity of 100 Ah g− 1 at a current density of 0.1 A g− 1 and long-term cycling performance exceeding 5000 cycles. Consequently, these electrochemical performances are associated with the redox reactivity of carbonyl groups as verified by spectroscopic and electrochemical characterizations and the hybridization of HyPT nanorods with CNT networks.

Zinc-ion Batteries (ZIBs) are currently considered to be effective energy storage devices for wearable electronics because of their low cost and high safety. Indeed, ZIBs show high power density and safety compared with conventional lithium ion batteries (LIBs) and exhibit high energy density in comparison with supercapacitors (SCs). However, in spite of their advantages, further current collector development is needed to enhance the electrochemical performance of ZIBs. To design the optimized current collector for high performance ZIBs, a high quality graphene film is suggested here, with improved electrical conductivity by controlling the defects in the graphene film. The graphene film showed improved electrical conductivity and good electron transfer between the current collector and active material, which led to a high specific capacity of 346.3 mAh g-1 at a current density of 100 mA g-1, a high-rate performance with 116.3 mAh g-1 at a current density of 2,000 mA g-1, and good cycling stability (68.0 % after 100 cycles at a current density of 1,000 mA g-1). The improved electrochemical performance is firmly because of the defects-controlled graphene film, leading to improved electrical conductivity and thus more efficient electron transfer between the current collector and active material.

Zinc-ion Batteris (ZIBs) are recently being considered as energy storage devices due to their high specific capacity and high safety, and the abundance of zinc sources. Especially, ZIBs can overcome the drawbacks of conventional lithium ion batteris (LIBs), such as cost and safety issues. However, in spite of their advantages, the cathode materials under development are required to improve performance of ZIBs, because the capacity and cycling stability of ZIBs are mainly influenced by the cathode materials. To design optimized cathode materials for high performance ZIBs, a novel manganese oxide (MnO2) coated graphite sheet is suggested herein with improved zinc-ion diffusion capability thanks to the uniformly decorated MnO2 on the graphite sheet surface. Especially, to optimize MnO2 on the graphite sheet surface, amounts of percursors are regulated. The optimized MnO2 coated graphite sheet shows a superior zinc-ion diffusion ability and good electrochemical performance, including high specific capacity of 330.8 mAh g−1 at current density of 0.1 A g−1, high-rate performance with 109.4 mAh g−1 at a current density of 2.0 A g−1, and remarkable cycling stability (82.2 % after 200 cycles at a current density of 1.0 A g−1). The excellent electrochemical performance is due to the uniformly decorated MnO2 on the graphite sheet surface, which leads to excellent zinc-ion diffusion ability. Thus, our study can provide a promising strategy for high performance next-generation ZIBs in the near future.