| Lithium-ion batteries have been widely used in portable electronic equipments,electric vehicles and energy storage areas,but subject to conventional positive and negative active materials' specific capacity,the current commercial lithium-ion battery is difficult to meet the needs of higher energy density.According to the planning requirements of China's automobile power battery development route,the energy density of the power battery module had reached 150Wh/kg(170~190Wh/kg)by 2015,and the energy density of the power battery module will reach 250Wh/kg(monomer above 300Wh/kg)by 2020.However,the existing materials system has been unable to meet the needs of future development,so,it is necessary to develop high energy density of electrode materials.The theoretical specific capacity of silicon is as high as 4200mAh/g,which is more than ten times higher than the traditional graphite anode(the theoretical specific capacity of graphite is 372mAh/g).Its application can greatly improve the energy density of lithium ion battery.Therefore,silicon is expected to be the next generation of lithium ion battery's high capacity anode material.However,the silicon negative particles in the charge and discharge process,the volume change rate of more than 300%,resulting in active material structure of the powder,from the collector and loss of activity,and unstable solid electrolyte interface film(Solid Electrolyte Interface,referred to as SEI film)produced,and the low efficiency of silicon-based anode material,poor cycle performance,affects its use in lithium ion battery.In this paper,we summarize the structure and composition of lithium ion batteries and the progress of the anode materials.By comparing the structure and electrochemistry of four different types of silicon-based anode materials with micro-silicon,silicon-carbon composite,ferrosilicon alloy and silicon-oxygen alloy(SiOx),SiOx can effectively inhibits the volume expansion of the silicon particles,and it has better cycle performance(half-cell 0.2C cycle after 20 times the capacity retention rate>70%),higher capacity(first capacity more than 1600mAh/g),so it is more promising commercial applications of materials.In order to optimize the surface structure of Si/SiOx to improve the first-time efficiency,we use an amorphous carbon-coated approach,the first-time efficiency increased by 10%,the cycle capacity retention rate increased by 11%.In order to further improve the conductivity of Si/SiOx/C materials,the microstructures of Si/SiOx/C composites were investigated by studying the conductive network structure of Super P,CNTs,Graphene three conductive agents and Super P&CNTs,Super P&CNTs&Graphene.Super P&CNTs,Super P&CNTs&Graphene have the characteristics of three-dimensional conductive network structure,so their Si/SiOx/C electrodes' resistivity is lower.Excellent performance,best cycle performance(half battery 0.5C cycle after 20 times the capacity retention rate>55%).In order to improve the bonding property between Si/SiOx/C,conductive agent and current collector,we studied the effects of conventional SBR/CMC conventional binder system and PAALi new binder on the properties of Si/SiOx/C pole piece.In the Si/SiOx/C/graphite composite polymer lithium ion battery(in the model 418281),the new PAALi binder can improve the peel strength of the pole piece,reduce the internal resistance of the battery,improve the battery magnification,cycle,high and low temperature performance.Through the optimization of silicon-based anode materials,the use of conductive agents and adhesives to optimize the final development of the energy density is up to 737Wh/L,after 300 times the capacity retention rate of 80%,which can meet the basic application of lithium-ion battery Requirements,promoting the application of silicon-based anode materials in high-energy-density lithium-ion batteries. |
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