The Study Of New-Generation Energy Storage Devices Based On Three-Dimensional Composite Electrodes

Flexibility, portability, and miniaturization, have been considered as main development trend for future electronic devices, which demonstrates that new-generation high-performance energy storage devices as power sources are needed to drive above electronic ones. However, existing energy storage devices have many defects including bulky, inflexible, excessive price, low power/energy density, poor miniaturization and integration, etc, which hinder development of new-generation electronic devices. Considering above issues, this paper mainly illustrates creative researches on new-generation energy storage devices based on three-dimensional (3D) composite electrodes, including as follow:(1) Flexible lithium-ion batteries based on ZnCo2O4nanowire arrays/carbon cloth3D composite electrodes:Novel ZnCo2O4nanowire arrays/carbon cloth composites were fabricated by using hydro thermal method, and the crystal structure and morphology of these samples were characterized. These materials were further assembled into coin-type and flexible Li-ion batteries. Their many battery properties were then measured. These results indicates that these composite anodes demonstrated high specific capacity (1200～1340mAh g-1) for160charge/discharge cycles and good rate capability. That capacity of as-prepared ZnCo2O4materials is far higher than that of current graphite anodes (372mAh g-1). Also, the discharge capacities of the device remains almost constant even during120cycles of bending. To demonstrate its practical applications, the as-fabricated flexible battery was successfully used to control a commercial green LED and a LCD mobile display, even hand-held game player. Also, these devices can be driven even when the flexible battery was bent or folded.(2) Flexible lithium-ion batteries based on ZnCo2O4urchin-like nanomaterials/carbon fibers3D composite electrodes:Based on above work (1), by adjusting parameters, ZnCo2O4urchin-like nanomaterials/carbon fibers composites were synthesized by using hydrothermal method. After battery assembly, these measured results show that the specific capacity of these3D composite anodes still be as high as1180mAh g-1after100charge/discharge cycles, revealing these ZnCo2O4-based electrodes with high specific capacity and outstanding cycling stability. Importantly, their reversible specific capacity of 750mAh g-1was obtained at as high as18A g-1over100cycles, which reflects that this value still retained83.3%of the theoretical capacity for ZnCo2O4materials. High-power performance of our ZnCoO4/carbon fibers composite anodes is better than that of other reported previously ZnCo2O4electrodes. The results demonstrate that many merits of novel3D structures for ZnCo2O4/carbon fibers composite electrodes really contribute to the enhancement of battery performance. Flexible batteries formed with ZnCo2O4/carbon fibers electrodes also showed good electrochemical performance and high stability under different bending states. Further, these flexible batteries were integrated smoothly to clothing and travelling bag, which will facilitate future requirements of portable and wearable electronic devices.(3) Flexible lithium-ion batteries based on Si nanowires/carbon cloth3D composite electrodes:Si nanowires with high purity were synthesized by using CVD approach. These silicon materials were then sprayed onto highly flexible carbon cloth to fabricate the Si nanowires/carbon cloth3D composite electrodes. Further, the crystal structure and morphology of these samples were characterized. And these samples were assembled into coin-type and flexible batteries to measure their electrochemical properties. These3D composite anodes showed high reversible specific capacity (2950mAh g-1), excellent cycling stability (as long as200cycles), and enhanced rate capability. Also, flexible Li-ion batteries formed with Si/carbon textiles composite anodes demonstrated quite high stability in various external conditions including curvature, temperature, and humidity. Thus, these as-prepared Si-based3D composite anodes possess better comprehensive performance, which could provide a possibility to replace commercial graphite anodes with these high-performance Si/C composites electrodes.(4) Wire-supercapacitors based on Mn2O3cube arrays/carbon wires and ZnCo2O4nanowire arrays/carbon wire3D composite electrodes:Mn2O3cube arrays/carbon wires electrodes were obtained by using hydrothermal method, and the crystal structure and morphology of these samples were characterized. These3D electrodes were creatively arranged to form various models of wire-supercapacitors (straight, bent, and coiled). After5000charge/discharge cycles, capacitance retention ratios of three wire-supercapacitors indicated as high as91%,93%, and94%, respectively. The measured results show that the capacitance of the coiled wire-supercapacitors is about100%and83%higher than that of the straight and bent wire-supercapacitors. The coiled wire-supercapacitors can be attributed to the enhanced synergetic effects of the coiled wire-electrode configuration. In addition, this work demonstrated further researches on the effects of electrode distance and length on the device performance. The computational simulations for wire-shaped energy-storage devices were performed for the first time, the calculated results were well consistent with above experimental conclusions. This work reveals that well-optimized performance of wire-supercapacitors can be achieved by designing their micro-electrodes models, which facilitates the realization of minimized size and maximum functionality. Also, ZnCo2O4nanowire arrays/carbon wires3D composites electrodes were prepared by using hydrothermal method, by planar-integrated assembly of these electrodes, a new class of flexible wire-supercapacitors are designed and fabricated.(5) Promising Mg-ion batteries based on WSe2nanowires/W foil3D composite electrodes:WSe2nanowires/W foil3D composite cathodes were synthesized by using CVD method, then the crystal structure and morphology of these samples were characterized and Mg-ion battery properties of these3D composite cathodes were measured. The results indicated that novel WSe2/W foil composite cathodes delivered high specific capacity (203mAh g-1) that is fully comparable to the specific capacity of Li-ion battery cathodes. Mg-ion batteries formed with WSe2/W foil3D composite cathodes kept excellent stability for160charge/discharge cycles. At higher current density of800mA g-1, specific capacity of these electrodes still be reach142mAh g-1(as high as83.5%of capacity retention ratio). Obviously, these3D composite electrodes possess efficient Mg2+intercalation/insertion activity, excellent cycling life, enhanced specific capacity, and excellent rate capability. Considering experimental results and calculated simulations, unique advantages of WSe2with graphene-like layered structure and3D composite electrodes could be evaluated. This work demonstrates a feasibility of novel WSe2/W foil3D composites as suitable Mg-ion battery cathodes, which will promote further development of alternative battery technology.