The Application Of Electrospinning For Lithium Battery Anode Materials

Lithium-ion batteries are the systems of choice, offering high energy density,flexible and lightweight design, and longer lifespan than comparable batterytechnologies. It is being driven by an ever-increasing demand for actual needs.Today, to pursuit high performance and high capacity anode materials has become oneof the objectives of lithium-ion battery. The high theoretical capacity and lowdischarge potential of silicon have triggered significant research efforts on Si-basedanodes. Si anodes show large volume changes during Li insertion and extraction,leading to electrode failure, which leads to low power capability and rapid loss ofcapacity. In this dissertation, material designs and electrode structure wereinvestigated to from the electrochemical performance of silicon anode. As following:1） A self-supporting silicon-containing hole carbon nanofiber membrane(H-Si-CNFs) was obtained by electrospinning a polyacrylonitrile (PAN)/DMFsolution containing silicon nanoparticles (SiNPs), followed by pre-oxidation,carbonization and HF-treating processing. The H-Si-CNFs are directly used as anodematerials for making lithium ion batteries. The results show that the10%silicon-containing H-Si-CNFs electrode has an excellent cycle performance at100mA/g charging/discharging, the initial reversible capacity of607mAh/g and acapacity retention rate of92%after40cycles.2) Used the layer-by-layer electrospinning, we has been a like-diaphragm filmwith continuous, multi-layered,meshy carbon nanofibers. With silicon nanoparticlescarbon nanofibers has been in the middle of the film. The challenge of silicon volumechange could effectively be overcome by the like-diaphragm structure, during thecharge and discharge. Obtained a good result. The800℃Si-CNFs-DCNFscomposite material has good capacity performance, and cycle performance. The800℃Si-CNFs-DCNFs composite material has good capacity performance, andcycle performance. The composite material exhibits large initial reversible capacityup to815.4mAh/g and the excellent coulombic efficiency(79%) with50mA/gcurrent density. The highest specific capacity retention of690.8mAh/g after30cycles.3) We discussed the time and temperature settings of pre-oxidation andcarbonization process on electrode performance of PAN-based fibers as anodematerial for lithium-ion battery. It turned out that, the proper gradient pre-oxidation temperature and time play an important role on bring in oxygen-containingfunctional groups and stabling the molecular structure on fiber. The moderateoxygen-containing functional groups on fibers could effectively improve the capacityof the fiber electrode. Carbonization temperature has played a very important roleon maintaining the morphology of fibers surface. Low temperature carbonizationcan keep the "wrinkle" and pore structure of the original fibers, make theinsertion/extration of Li more easier. The pre-oxidation gradient150℃(3h)â†'230℃(3h)â†'carbonized600℃(1.5h) was the best condition obtained byoptimizing the experimental conditions,to get higher capacity and cycle stability.The composite material exhibits large initial reversible capacity up to876.3mAh/gand the excellent coulombic efficiency(65.5%) with1C rate. The highest specificcapacity retention of63.2%after100cycles.4) Modified the optimal electrode with carbonization again, acid treatment anddop MWCNTs, to find the best treatment method. Among them,The secondarycarbide fiber electrode exhibits large initial reversible capacity up to805.8mAh/gwith1C rate, the high specific capacity retention of744.5mAh/g(92.4%) after100charge-discharge tests.