Design,Synthesis And Application Of Composites Based On The Carbonaceous Nanofibers

Due to their significant advantages in energy density and environmental sustain-ability, Li-ion batteries (LIBs) have quickly dominated the market of consumer elec-tronics since 1990s. With their applications extending into large-scale stationary storage fields including transportation and grid, traditional LIBs electrode materials are limited by the intrinsically low theoretical capacities of both electrodes and could not catch the increasing demand on energy density. Developing highly efficient rechargeable batter-ies is crucial to alleviate the current energy and environmental problems.The dissertation will focus on the design, synthesis and performance of LIBs of the composite materials based on the carbonaceous nanofibers (CNFs). Kinds of mate-rials could be decorated on the CNFs via different synthesize methods. The cooperation of the two active components in the composites leads to a favorable synergistic effect, bringing a better LIBs performances than those delivered by any of the single compo-nent. The results can be summarized as follows:1. Developed a simple strategy to synthesize well-defined CNFs@MoS2 coaxial nanofibres. In use as anode materials for LIBs, the cooperation of the two active compo-nents in CNFs@MoS2 leads to a synergistic effect, triggering a new electrochemistry on the Li storage of MoS2, by which electrochemically active and stable MoS3 reversibly forms in the charge process, leading to an increased capacity upon cycling. The syn-ergistic effect also helps to build a hierarchically conductive network, contributing to much improved electrode kinetics and cycling stability. The CNFs@MoS2 nanofibres exhibit excellent Li storage properties in terms of specific capacity (1489 mAh/g upon initial discharge), cycling performance (1264 mAh/g after 50 cycles) and rate perfor-mances (860 mAh/g at 5 A/g), making it a promising anode material for high energy LIBs. Moreover, in the light of the notable capacity advantages of non-intercalation materials in high-energy batteries, our pioneering work in finding the synergistic effect of CNFs@MoS2 is expected to have far-reaching significance over previous works on intercalation materials. The science behind the strategy is simple yet inspiring, and be-cause of its versatility, could also bring insights to those working on the Li-S battery, benefiting the industry and contributing to a better economic sustainability.2. Successfully fabricated TiC NPs-CNFs hybrid electrode by hydrolysis and an-nealing process for improving the performance of Li-S batteries. Due to the highly conductivity of the composites, the kinetics of polysulfides were largely enhanced. The strong interaction between TiC nanoparticles and polysulfides suppress the shuttle ef-fect and improve the utilization of sulfur species. Thus, the S/TiC-CNFs cathode ex- hibits excellent cycling and rate performance, making it a promising electrode material for Li-S batteries. The hybrid electrode design strategy is simple yet efficient and could also bring insights to future works on the Li-S and Li-air batteries.3. We developed a new technique for preparing nitrogen doped carbonaceous nanofibers decorated by molybdenum disulfide nanosheets by a simple one step tem-plate hydrothermal process. The MoS2 in the composites are mostly single layer, which is confirmed by the XRD and TEM results. When used as anode material in the sodium ion batteries (SIBs), the composite delivered enhanced cycling and rate performance. In addition, the composite could also be used as catalysts for the hydrogen evolution reaction due to the single layer MoS2 which is reported to be highly active in the HER.