A separator in battery can electrically isolate cathode and anode, which prevent electrical short circuits and allow rapid transport of ionic charge carriers. Nowadays, Polyolefin microporous membranes such as polyethylene (PE), polypropylene (PP), and PP/PE/PP made by a dry or wet process have been commercialized as major separators for lithium-ion batteries. However, these polyolefin-based separators suffer from poor wettability, serious thermal shrinkage and low transverse mechanical strength, whichimpairs the power capability of batteries and bring safety hazards.

Recently, Professor CUI Guanglei and his colleagues from Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, have made major progress on new separators for high power lithium-ion batteries. They have developed biomass-based inflame retarding separators, and the pilot-scale demonstration has been being carried out.

Cellulose, which is the primary component of green plants, is one of the most abundant, renewable resources on the earth and possesses outstanding properties such as high thermal stability, low cost and environmentalfriend. Based on cellulose materials, Prof. CUI and co-workers have successfully developed a highly safe and low cost separator via a “melt blowing-wet lying” process with independent intellectual property. Compared to commercialized microporous PP separator, these biomass based composite separators exhibited higher thermal stability, promising wettability, and desirable flame retardance. The cells using the biomass-based composite separator manifest much better rate capability, superior capacity retention and excellent safety characteristic. Professor CUI’s group hope the optimization of equipment and production processing will be completed by the end of December. An annual output of 300, 000 m2 of biomass-based composite separators can be expected next year.

This work was financial supported by Shandong Province Fund for Distinguished Young Scientist, and Qingdao Key Laboratory for Solar Energy and Energy Storage Technology.

Pilot-scale demonstration of the highly safe biomass-based composite separators (Photograph by Prof. CUI's group)