Effects Of C/Se Composite Coating On The Electrochemical Properties Of Si-based Lithium Ion Batteries

Lithium ion batteries（LIBs）have become the most important secondary battery in21^st century because its advantages of high energy density,high operating voltage,excellent safety performance and so on.In order to meet the high–speed development of modern functional devices.Researching LIBs with higher properties is urgent needed.LIBs anode is one of the most important component in the whole LIBs system.Commercial graphite can’t meet the demand of large energy storage because of its specific capacity(372 mAh g^-1)is relatively low.Silicon（Si）has been widely studied as the most potential LIBs anode,because of its advantages of high specific capacity(3579 mAh g^-1),moderate lithiation voltage plateau（（27）0.5 V vs.Li/Li⁺）and so on.Due to the problem of the huge volume change in lithiation/delithiation processes,low electric conductivity and so on,the commercial application of Si has been limited.In order to resolve these problems,series of strategies have been proposed such as design nanostructure and compose with other materials.In this paper,we have designed a core-shell nanostructural Si@SiO₂@C/Se LIBs anode by using C/Se composite to improve the cycling performance and rate capacity of Si-based anode.Using SiO₂ and C layer to improve the cycling stability of electrode,and through load Se to improve the ionic conductivity of the whole electrode.The main contents and results of this study are mainly as follows.1.Coating resorcinol/formaldehyde（RF）resin polymer on the surface of Si nanoparticles with native oxidation layer through a sol-gel self-assembly polymerization process.The RF resin polymer shell is used as carbon precursor,and then microporous Si@SiO₂@C has been obtained.The loading of Se is realized via a simple melting-diffusion process.Finally,a series of phase characterization of Si@SiO2@C/Se was performed.2.The cycling performance and rate capacity of Si@SiO₂@C/Se have been tested,the result shows Si@SiO₂@C/Se anode has excellent cycling performance and rate capacity.The as prepared Si@SiO₂@C/Se anode exhibits a high specific capacity of1560 mAh g^-1 after 150 cycles at the current density of 0.5 A g^-1 and a favorable rate capacity of 612 mAh g^-1 at 8 A g^-1.The effect of the ionic conductivity of whole electrode by Se has been analyzed by cyclic voltammetry and alternating current impedance.