Synthesis And Lithiation Mechanism Of Silicon/SiCO Thin Films Anode For Lithium-ion Battery

Lithium-ion batteries are widely used in small mobile electronic devices,medical devices and new energy vehicles,however,the commercial graphite anode materials can not meet the requirements of high capacity density.Silicon is one of the most promising anode materials for lithium-ion batteries because of its extremely high theoretical capacity,while its huge volume expansion during the charge and discharge process limits its further application.Silicon oxycarbide?Si CO?ceramics are composed with amorphous carbon?free carbon?network,silicon-centered tetrahedra and silica,this unique nano-structure results in high specific capacity,excellent cycling performance and high structural stability.In this work,Si/Si CO thin films anode is prepared by magnetron sputtering with different parameters,the carbon content and thickness of Si CO layer is changed and the corresponding electrochemical properties of the system is studied.The samples with high carbon Si CO layers deliver high reversible capacities of 2000 and 1750 m Ahg^-1 after 100cycles,it is attributed to the free carbon network of Si CO layer.By first-principles simulations,the calculated energy barrier for diffusion of lithium along Si/Si CO interface is significantly larger than those of the diffusion in Si,indicating that Li tend to diffuse into silicon but not along the Si/Si CO interface.Meanwhile,the calculations results also demonstrate the presence of Si-C/O tetrahedrons for enhanced reversible capacity of lithium,and the shorter Li-O and Si-Li bonds are related to the irreversible capacity of the system.An algorithm is proposed to evaluate the reversible capacities of the Si/Si CO heterostructure,the predicted reversible capacity is comparable to that of the sample in our experiment.The results and methods proposed in this work are valuable for developing novel thin films electrode materials.