Microstructure And Performance Of Si-Sn Anode Materials For Lithium Ion Batteries Fabricated By Laser Sintering

The environmental and efficient lithium ion batteries have been widely used in all aspects of life.Because of its low specific capacity,the commercialization of carbon materials gradually cannot meetthe needs of energy forrapidly developmental society.Therefore,the lithium ion batteries with high capacity,high charge-discharge rate and stable cyclic performance are the focus of present research.In many potential high capacity anode materials,Li is embedded in Si that can form Li₁₅Si₄ alloy at room temperature.And the alloy'stheoretical capacity is 3579mAhg^-1.it'salmost ten times than carbon anode materials.So silicon has become one of the most promising commercial anode materials.But when Li is imbedded in Si,its huge volume effect make the anode structure easy to collapse and crush.Its huge volume effect destroythe original conductive network.That makes the anode capacity downs quickly and cycle stability becomes worse.In order to solve the problemof stability for Si anode,in this paper,laser sintering is used to prepare the compound and the nano-compound Si-Sn anode materials to relieve the volume effect of charging-discharging silicon.Si-Sn anodes forlithium ion batterieswere prepared bylaser sintering.Using X-Ray diffraction?Scanning electron microscopeand electrochemical workstation to systematically analyze the effect of laser scanning speeds on microstructure and electrochemical properties.The results show:Even at different laser scanning speeds,the structure of all anodeswas composed of granular Sn distributed on Si substrate.But when the laser scanning speeds were gradually increased,the number of Sn particles on anodes surface was gradually increased,the number of micro-cracks was gradually decreased,and the structural integrity of the anodes was become more better.As laser sinter at laser scanning speeds of 60mm/s,the anode for battery had the best electrochemical properties.When the electric current density was 100mAg^-1,its initial reversible capacity and initial coulombic efficiency were increased nearly 130mAhg^-1and 12.3%,respectively.And its electrochemical impedance was also significantly reduced.In order to further improve the electrochemical properties of Si-Sn anodefor lithium ion batteries,using Si with a particle size of about 20nm to replace micro scale Si.Under the above optimization parameters,Nano-Si-Sn anode for lithium ion battery was prepared by laser sintering.Changing the particle size of Si powder did not lead the corresponding change in thephase of the anode.It was still composed of Si and Sn phases.Because of the high surface energy of nanoparticles,the anode had the phenomenon of nano-Si agglomeration in the local region.The Nano-Si-Sn anode for lithium ion battery had good structural integrity.Itsinitial coulombic efficiency was 65.02%at the current density of 100mAg^-1.And its coulombic efficiency maintained over 95%after 10 times discharge-charge cycle.Its reversible capacity remained over 300mAhg^-1 after 100 times discharge-charge cycle.The electrochemical properties of Nano-Si-Sn anode hadsignificantly improved compared with micro scale Si-Sn anodefor lithium ion battery.