Rational construction of self-standing fiber-shaped aqueous rechargeable batteries

• Main Author: Yang, Jiao
• Other Authors: Wei Lei
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/146498
• Institution: Nanyang Technological University

With the large consumption of non-renewable resources and the increasingly serious global environmental problems, the development of clean, efficient and abundant new energy has attracted great attention from all over the world. Among many new energy storage devices, aqueous batteries take advantage of high safety, low cost, and excellent ion conductivity, showing promising prospects for application in wearable energy storage. In addition, with the ever-growing consumer usage of portable and wearable electronics, small, flexible and lightweight, fiber-shaped batteries are regarded as promising energy supply devices. Aqueous nickel-based rechargeable batteries with the abundant constituent elements, low cost, and ultra-flat discharge plateau have attracted widespread attention. However, the problem of low energy density and short cycle life requires more attempts to improve the performance of the electrodes. Therefore, this thesis designs and prepares the flexible self-supporting electrodes through direct hydrothermal growth, sulfur doping and gas-solid phosphating methods to increase the volume/area capacity of the electrodes and construct the high-performance wearable aqueous batteries. The main research content is divided into the following parts: A facile and cost-effective method strategy is reported to fabricate three-dimensionally well-aligned zinc-nickel-cobalt oxide@Ni(OH)2 nanowire arrays on the carbon nanotube fibers as a promising heterostructure anode for fiber-shaped Ni-Zn batteries. Taking advantage of the accessible surface area, rich reaction sites and short electron/ion diffusion path of zinc-nickel-cobalt oxide@Ni(OH)2 nanowire arrays, a high capacity of 2.07 mAh/cm2 (516.7 mAh/g) and an impressive energy density of 3.71 mWh/cm2 (916.6 Wh/kg) were achieved for our as-assembled fiber-shaped Ni-Zn batteries, outperforming most previously reported aqueous Zn-based batteries. Successfully fabricating the sulfur-doped Fe2O3 nanowire arrays grown on carbon nanotube fibers as an innovative anode material. The novel developed S-Fe2O3 electrode is further demonstrated to deliver very high capacity equal to 0.81 mAh/cm2 at 4 mA/cm2. This value is almost 6 times higher than of the pristine Fe2O3-based electrode. When a cathode containing zinc-nickel-cobalt oxide@Ni(OH)2 NWAs heterostructures as cathode material was used, 0.45 mAh/cm2 capacity and 67.32 mWh/cm3 energy density were obtained for the fiber-shaped NiCo-Fe batteries containing polyvinyl alcohol-potassium hydroxide gel electrolyte. A novel flexible Ni-Fe battery using all metal phosphides as electrodes on highly conductive fibers is successfully designed and fabricated with improved electrochemical performance. Hierarchical NiCoP nanosheet arrays and FeP nanowire arrays were fabricated firstly using hydrothermal synthesis then pursuant gas phosphating process. With the assistance of PVA-KOH gel electrolyte, the fiber-shaped aqueous rechargeable battery presented negligible capacity loss after bending 3000 times. Meanwhile, the assembled battery had a significant capacity of 0.294 mAh/cm2 under the current density of 2 mA/cm2 and a high energy density of 235.6 µWh/cm2.