Preparation And Properties Of Biopolysaccharide Fiber-based Lithium Ion Battery Separators

Lithium ion batteries due to their advantages of high energy density,high working voltage,etc were widely used.As one of the important component of the lithium ion battery,the separator also plays an important role in improving the security performance of the battery and reducing the cost.In our work,the high security and large capacity lithium ion separator were prepared by the bio-polysaccharide fibers（calcium alginate fiber and cellulose fiber）.（1）The bio-polysaccharide fibers based composite lithium ion battery separator was prepared through papermaking technique,according to gurley value and electrolyte uptake,the composite separator has a good infiltration effect with electrolyte.According to limit oxygen index（LOI）test,differential thermal analysis（DTA）and characterization of the contraction of morphology under different temperatures,the separator at higher temperatures won’t appear thermal contraction.It’s a breakthrough progress in enhancing the security of the separator.The ionic conductivity of composite separator was 1.22×10-3 S/cm,is higher than the Celgard 2500（PP）（0.17×10-3 S/cm）,and the resistance of the composite seperator is relatively low,electrochemical window test found that the composite seperator electrochemical window was about 4.5 V.The discharge capacity of the LiFePO3 battery、the rate performance which used of the composite separator is higher than that of PP.（2）By modified the 70% calcium alginate fiber content of composite seperator AlgF（70%）with nano inorganic materials（Al₂O₃ and SiO₂）,found that modified seperator reduced its porosity,enhanced the strength（more than four times of the unmodified）,and improved the thermal stability.（3）Through the previous survey,we found that the higher the calcium alginate fiber content in the composite seperator,the better the electrochemical properties of the batteriy.By adding soluble salt alginate（sodium alginate and magnesium alginate）as a binder to the preparation of pure calcium alginate fiber seperator,we found that the aperture size,the cohesive strength between fiber reinforced and the strength of the separator has improved significantly.By the electrochemical window test,the separator electrochemical window is 5 V,and the battery capacity is high.