The Research Of Preparing Separators For Lithium-ion Battery By Ceramic-coating Nonwoven

With the advantages of high energy density and excellent cycling performance,lithium-ion batteries(LIBs)are commonly used to portable consumer electronics in addition to being increasingly developed for application in hybrid electric vehicels(HEVs).However,the safety of LIBs has largely prevented their market acceptance,especially in transportation applications.As a part of the battery,the separator plays a critical role to ensure the battery safety.This research was based on the present development of the separator,two kinds of ceramic-coating nonwoven separator for LIBs were developed.A porous nonwoven membrane was chosen as the coating substrate,alumina were used as inorganic powder,polyvinylidene fluoride(PVdF)and Carboxymethyl Cellulose(CMC)were used as organic-soluble binder and water-soluble binder respectively.The physical and electrochemical properties of the organic phase ceramic-coating nonwoven separators were analyzed.The results show that the CS-3 separator,compared to the nonwoven,developed a hydrophilic porous structure,the pore size was around 0.15?m,and the electrolyte uptake rate increased from 172%to 487%;In comparison with the Celgard 2300 separator,the CS-3 separator exhibited excellent thermal stability with almost no thermal shrinkage at 150 ?,and enhanced electrolyte wettability.Additionally,the battery assembled with CS-3 separator exhibited the highest specific capacity of 512 mA·g-1 and good cycling performance after 100 charge-discharge cycles at a current density of 100 mA·g-1.The CS-3 separator also exhibited higher ionic conductivity(0.99 mS ·cm-1),superior discharging C-rate capability and electrochemical impedance spectroscopy(EIS).These results suggest that the CS-3 separator can effectively improve the safety of the LIBs,and further improve the electrochemical properties of the LIBs.Notable feature of the water phase ceramic-coating nonwoven separators(especially the MS-2 separator)was close-packed alumina particles,which afforded a well-developed porous structure and reduced the pore size of the separator.The porosity of the MS-2 separator increased from 68.79%(the base nonwoven)to 75.83%,it exhibited excellent hydrophilic to the electrolyte with the electrolyte uptake rate of 200%.In addition,the MS-2 separator showed excellent thermal stability for the existence of the Al2O3 particles.In addition,the battery assembled with the MS-2 separator exhibited superior electrochemical performance with ionic conductivity(0.99 mS·cm-1),cycling(617.30 mA·g-1 after 100 cycles),discharging C-rate capability and electrochemical impedance spectroscopy(EIS)comparing to the battery assembled with Celgard 2300 separator.This indicates that the MS-2 separator is demonstrated to be a promising candidate as the next-generation separator for high-safety LIBs.