Preparation And Properties Of Si/Ag/C Nanocomposite As Anode Materials For Lithium Ion Batteries

Silicon has been regarded as the most promising anode material for lithium ion batteries for its highest specific capacity,low platform,abundant resources and safety.However,the volume change and poor electrical conductivity of silicon greatly hindered its practical application.So far,strategies to overcome the drawbacks of silicon based anode material include nanocrystallization,composition with other material and reasonable structural design.Nanocrystallization silicon,such as nanoparticles nanowires and nanotubes,can reduce the degree of absolute volume changing and releasing the stress of the silicon.Composit silicon with buffer material,such as carbon,metal,can release the expansion of volume and enhance the ability of electrical conductivity of silicon.Building multi-level structure is beneficial to absorb the volume expansion of silicon and suppress the formation of SEI films.Because of the superior electron conductivity and excellent mechanical property,silver was regarded as an excellent candidate to composite with silicon.However,the heavy use of silver will inevitably cause the raise of the cost.In addition,silver possess very limited lithium insertion performance during the charge and discharge process.The heavy use of silver may decrease the whole capacity of the silicon based anode material.In this paper,we solve these problems from the following several aspects.Firstly,introduce carbon matrix in to Si/Ag nanocomposite are beneficial to decrease the cost and mitigate the volume change of the silicon simultaneously.Secondly,decrease the size of the Ag is conducive to enhance the electroconductivity of the carbon matrix.Thirdly,prepare silver nanoparticles with special structure is beneficial to form three-dimensional cross-linked conductive network.The main research results in this paper are listed as follows:i)Si/Ag nanocomposite was obtained by ultrasonic dispersion method.From theelectrochemical performance test,it was observed the lithiation performance of the silicon was greatly enhanced with the addition of the silver.However,with the increase of the silver amount,the whole specific capacity of the silicon based anode was sacrificed to some extent.ii)Ag/C nanocomposite was obtained by solidification and calcination of the epoxy resin-Ag NO3 mixture.It was observed that the existence of the ultra-small Ag nanoparticles in the carbon matrix greatly enhanced the electrocehmical performance of the carbon based anode.iii)Si/Ag/C nanocomposite was obtained by solidification and calcination of the epoxy resin-Si-Ag NO3 mixture.It was observed that the existence of the ultra-small Ag nanoparticles in the carbon matrix greatly enhanced the rate performance of the Si/C anode.iv)Si/Ag/C nanocomposite with the existence of silver nanorods was obtained by the addition of morphology control agent.It was observed with the existence of silver nanorods,excellent rate performance was obtained.Which may result from the crosslinked conductive network formed by the silver nanorods.