Preparation And Characterization Of Alumina Ceramic Composite Separator For Lithium Ion Battery

At present, Li-ion battery has become the mainstream device of energy storage on the market. And as "the third electrode", separator is an important component of lithium ion battery. Currently polyolefin membrane is treated as the main Li-ion battery separator because of its chemical stability, well mechanical properties and suitable for large continuous production. However, as the shortage of thermostability and electrolyte affinity, polyolefin membrane also restricts the safe and efficient utilization of Li-ion battery. In this paper, according to the shortage of polyolefin membrane, preparing nano-alumina and apply it to cover the organic separator, and study the thermal stability and electrolyte wettability. Besides, The separator assembly into the cell,in order to investigate the electrochemical properties. This topic main research content is as follows:Firstly manufacture nano-alumina by traditional tank reactor, and inspect the impact of aluminum salt types, surfactant types, precipitant types, aluminum salt dropping speed, calcination conditions, precipitant concentration, molar ratio of precipitant to aluminum salt and bathing temperature on the alumina particle, appearance and crystal form. Characterize the alumina crystal form and particle appearance through XRD, SEM, TEM or other methods. Choose aluminum nitrate and ammonium carbonate to be aluminum salt and precipitant respectively. The nano-alumina with special continuity structure is then prepared under the conditions that molar ratio of precipitant to aluminum salt is 2.5:1, bathing temperature at 0℃, calcination temperature at 1200 ℃ and keep it for 2 hours. Its average particle size is 150 nm, but it still exists some particle agglomeration.Under the condition of the optimization, further prepare nano-alumina by rotating packed bed, and inspect the impact of feed rate, feed concentration, reaction temperature and molar ratio of precipitant to aluminum salt on the alumina appearance and crystal form. The 150 nm nano-alumina with special continuity structure is then prepared under the conditions that feed rate of precipitant and aluminum salt at 30 ml·min-1 and 80 ml·min-1, molar ratio of precipitant to aluminum salt is 2.5:1 and reaction temperature at 0℃. Compared with traditional tank reactor, the needed time for reaction is sharply reduced to about one tenth. Moreover, the nano-alumina prepared from it has more uniform particle distribution, and without particle agglomeration.Lastly apply the prepared nano-alumina with special continuity structure to cover the polypropylene basement membrane, and then prepare alumina composite separator. Through the test, it finds remarkable improvement in both electrolyte wettability and thermostability. Electrolyte can spread quickly on the alumina composite membrane, whose shrinkage ratio just at 10% after heating in 160℃ for 30 minutes. Take it to assemble battery, the test shows a maximum li-ion conductivity of 0.422 mS·cm-1. Compared with basement membrane, the prepared alumina composite membrane also gains rise in battery capacity and circulation property. The former reaches a maximum of 157.7 mAh·g-1, and the later keep at 95.4% after 30 times of cycles.