Preparation Of Lithium Ion Battery Separator By Coaxial Electrostatic Co-spraying Technology

Electro-spinning and electro-spraying are important techniques for preparing materials.Among them,electro-spinning is used for fiber preparation;electro-spraying is used for particle and coating preparation.Coaxial electro-spinning technology,which is included in electro-spinning technology,is used to prepare fiber of core-shell structure.For the first time,a novel method named coaxial electro-spraying/electro-spinning is introduced to prepare 3D composite membrane of ultrafine fibers and ultrafine particles.In this paper,the coaxial electro-spraying/electro-spinning equipment was assembled firstly,which contains outer nozzle and inner nozzle.The Si02 was selected and modified by three modification methods to study the spraying process:polymer blending modification,?-methacryloxypropyltrimethoxysilane(KH570)graft modification and small molecule modifier.The optimum spraying parameters were studied respectively.The experimental results show that the optimum concentration of polyvinylidene fluoride(PVDF)blended Si02 is 4%,and the average particle size is 2.01 ?m under the receiving distance of 10cm and 23kV;the optimum concentration of SiO2 grafted by KH570 is 10%.The 0.3%KH570/SiO2 spray solution has an average particle size of 83.93 nm at a receiving distance of 10 cm and a voltage of 23 kV.The optimum concentration of sodium dodecylbenzene sulfonate(SDBS)is 300 mg/L.The acceptance distance was 10 cm,and the average particle size of the spray at a voltage of 23 kV was 77.23 nm.Secondly,PVDF,PS and PA6 were selected as spinning raw materials,and combined with three spraying methods into five kinds of system:in system A PVDF/SiO2 in DMF was used to prepare the particles from outer nozzle of the equipment,and PVDF dissolved in a mixture of DMF and acetone is used to prepare the fiber from the inner nozzle of the equipment;in system B,a graft-modified SiO2 by KH570 in a mixture of ethanol and DMF was used to prepare particles and PVDF dissolved in a mixture of DMF and acetone is used to prepare the fiber;in system C,SDBS/SiO2 in a mixture of ethanol and deionized water was used to prepare particles and PVDF dissolved in a mixture of DMF and acetone is used to prepare the fiber;in system D,a graft-modified SiO2 by KH570 in a mixture of acetone and DMF was used to prepare particles and PS dissolved in DMF is used to prepare the fiber;in system E,a graft-modified SiO2 by KH570 in a mixture of trichloromethane and DMF was used to prepare particles and PA6 dissolved in formic acid is used to prepare the fiber from the inner nozzle of the equipment.The composites containing particles and fibers were successfully prepared simultaneously via the titled equipment in all system.The average fiber diameter in system A is 0.428?m,and the average particle diameter is 2.01?m;the average fiber diameter in system B is 0.46?m,and the average particle diameter is 80.81nm;the average fiber diameter in the system C is 0.343?m,and the average particle diameter is 88.56nm;the average fiber diameter in system D is 0.347?m,and the average particle diameter is 79.48nm;the average fiber diameter in system E is 0.246?m,and the average particle diameter is 108.96nm.Then the modified composite was put on the ultra-high molecular weight polyethylene(UHWMPE)in situ to prepare a novel Li-ion battery separator.The analytical results showed that the porosity of the separator prepared by the system A was increased from 37.85%to 85.96%,and the data of system B reached 63.64%,and the data of system C reached 81.33%,and the data of system D reached 69.72%,and the data of system E reached 69.69%.And PVDF&KH570/SiO2 composite separator has the highest first discharge specific capacity of 152mAh/g.