Cone-shaped Core-shell Structured Arrays And Porous Structure As Electrode Materials For Lithium Ion Batteries

The rapid development of science and technology has brought convenience to our life,at the same time,it is more and more urgent to seek cleaner and more efficient energy to take place of fossil fuels since the increasing demand for energy.Lithium-ion batteries?LIBs?are widely used in portable devices,powered vehicles,and microelectronic devices because of high energy density,high energy efficiency,lightweight,and environmentally friendly performance.The anode material is one of the key component of LIBs.Among the existing anode materials,silicon has attracted great attentions due to its highest theoretical capacity(⁴200mAh g^-1),environmental friendliness,rich crust content and low cost.However,the silicon-based anode materials face chanllenges such as large volume expansion and low conductivity,leading to the capacity fading and large irreversible capacity,even the loss of contact with current collector.In order to solve these two problems,the main contents of this paper include:1)The Ni cone-shaped array was obtained through simple electrodeposition experiments on the copper substrate,and the amorphous silicon thin film was sputtered on the surface of the synthesized Ni cone-shaped array by RF-sputtering.Finally,the Ni@Si core-shell array structure was obtained.The core-shell structures can alleviate the volume expansion and enhance the eletrical conductivity.A a result,the Ni@Si core shell array structure shows the good electrochemical performance.After 500 cycles,the discharge capacity remains at 938.7mAh g^-1,with a capacity retention of 78.9%.2)The porous Si was prepared through simple hydrothermal corrosion of nanosilicate with urea.The porous structure was determined by the adjusted reacting temperatures and time.Then,a uniform layer of carbon was coated on the surface of porous Si by CVD method,and finally porous Si@C composite material was obtained.The porous structure can alleviate the volume expansion and enhance the electrical conductivity of silicon during the charge/discharge process.As a result,porous Si@C composite can show the good cycling performance.The first charge and discharge capacities of the porous si@c composite electrode were 1634.8 mAh g^-1 and 1838.5mAh g^-1,respectively.After 10 cycles,the discharge capacity remained at 1591.7 mAh g-1,with a capacity retention of 86%.For comparsion,the nano Si can only obtain⁵1.4%of capacity retention.