Preparation And Properties Study Of SiO-based Materials As Anode For Lithium Ion Batteries

Lithium ion batteries are widely used in portable electronic devices and energy storage systems because of their low self-discharge rate,long cycling life and environmental friendliness.As an important constituent part of lithium ion batteries,it performance derectly affects energy density of batteries.At present,the dominating anode materials with excellent cycling performance are carbon materials,however,their capacity and rate performance are poor and is difficult to satisfy the requirement of the development.Silicon monoxide?SiO?has the broad development prospect as a negative electrode material and attracts much attentions own to its high capacity,rich natural resources and malleable.However,the large volume expansion of SiO and the repeated charging and discharging process can easily make the active materials to crack until to peel off from the collector.Besides,the low intrinsic conductivity can lead the poor dynamic performance so that the widely application of it is limited.In this study,micron grade SiO is used as the raw material,which are combined with monoclinic titanium dioxide?TiO₂?B??,LiF and piezoelectric material BaTiO₃ to compare the performance by different preparation methods,so as to obtain the anode materials that can be applied in actual production.The details are as follows:?1?p-SiO/TiO₂?B?composites were prepared by hydrothermal and calcining methods.Comparing with p-SiO,the p-SiO/TiO₂?B?composite had excellent electrochemical properties,and its first coulomb efficiency was 78%,which was higher than p-SiO?68%?.After 100 cycles,the capacity of p-SiO/TiO₂?B?was 730 mAh g^-1,much higher than that of p-SiO.The SEM showed that the surface of p-SiO was covered by TiO₂?B?,which could not only effectively inhibit the massive volume expansion of p-SiO,but also avoided the directly contact between p-SiO and electrolyte.It was found that the diffusion coefficient of lithium ions and the impedance of p-SiO electrode were greatly improved by TiO₂?B?.?2?SiO@C/graphite-LiF?SCG-LiF?composites were successfully prepared by CVD method,and the electrochemical influence of LiF to the composite of SCG-LiF was investigated.Specially,the capacity retention of SCG-7.5%LiF was 91%after 100cycles at 0.1 A g^-1,the coulomb efficiency was as high as 99.33%,and the its first coulomb efficiency was 83.5%.Moreover,SCG-7.5%LiF also shown good rate performance:even at the large current of 3.2 A g^-1,the reversible capacity of SCG-7.5%LiF was 190 mAh g^-1.The composite of SCG-LiF had good electrochemical properties because of the dense carbon layer on the surface of SiO improved its electrical conductivity,the graphite particles inhibited the volume expansion and agglomeration of SiO.In addition,the LiF made the SEI film more stable and greatly reduced the repeated generation and rupture of the SEI film.?3?The composites of SiO@C//BaTiO₃/CNTs?SCB/CNTs?were successfully prepared by using the piezoelectric material BaTiO₃ nanoparticles in silicon carbon negative electrode.Among of them,the composite of SCB/CNTs-712 shown excellent electrochemical properties,it first charge/discharge specific capacity was 771/954 mAh g^-1 and the first coulomb efficiency was 80.8%,also,its reversible capacity retention rate was 92.3%after 200 cycles.It was found that the BaTiO₃ nanoparticles can promote the migration of lithium ions in the silicon carbon negative electrode with dense structure.In a certain range,the higher the content of BaTiO₃,the faster the migration rate of lithium ions.In conclusion,the first coulomb efficiency,cycle performance and rate ability of modified silicon-based materials were greatly improved.