dc.description.abstract | In this study, we targeted silicon oxide(SiOx)materials as anodes for lithium-ion batteries. SiOx has a high specific capacity to store lithium, abundant natural resources and safety. However, the low initial coulombic efficiency and large volume expansion during cycling lead to the loss of active lithium and a decrease in the coulombic efficiency(CE)of silicon-based materials. Therefore, our goal is to compensate for the irreversible loss of lithium ions during the first charge-discharge cycle. To increase the initial coulombic efficiency(ICE)and charge-discharge capacities, we designed a chemical immersion method for pre-lithiation anodes. We used different aromatic compounds, such as naphthalene(NP), 1-methylnaphthalene(MeNP), 2-Phenylphenol(BPOH), 2-Naphthol(NPOH), with lithium metal in 2-Methyltetrahydrofuran(Me-THF)or tetrahydrofuran(THF)solvent to form pre-lithiation solutions.
In order to achieve higher initial coulombic efficiency, we chose the 1-methyl naphthalene(MeNP)compound to enhance the pre-lithiation effect by using the electron-donating functional group, the methyl on naphthalene, to decrease the redox potential. With the MeNP/Me-THF pre-lithiation solution, we found that after immersing for 20 minutes, the ICE increased to 147.2%, and the open circuit voltage(OCV)decreased to 0.29 V. Although it exhibited fast pre-lithiation, the reversible capacity was reduced. Therefore, we added aromatic compounds containing functional groups with relatively low redox potential and high electron affinity containing O groups, to increase the attraction to Li+ and slow down the breaking of Si-O bonds when anions and Li+ entered the SiOx electrode. We compared the effects of adding 2-phenylphenol(BPOH)or 2-naphthol(NPOH)compounds and found that the higher LUMO molecule had the best effect. Using 1-methyl naphthalene with 10% of 2-phenylphenol reacted for 20 minutes, the ICE increased to 136.5%, and the reversible capacity increased at various charge-discharge rates. The anode, immersed in a solution containing 1-methyl naphthalene and 10% 2-phenylphenol, exhibits a reversible capacity of 86 mAh/g at a high-speed charge-discharge rate of 5000 mA/g. | en_US |