Applied Technology

Series of Progress Achieved in LICs

The lithium ion capacitors (LICs), as green and efficient energy storage devices, require the energy density as high as 30 Wh/kg. LICs are promising substitutes for lead-acid batteries. Recently, the Advanced Energy Storage Technology Center of Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), CAS, has developed high performance LICs devices and solved a series of key technological issues, such as predoping lithium process. After 10000 cycles, the capacity retention of the LICs is above 90%.  In order to make the graphite more valuable, the research center has developed key electrode materials for LICs (J. Mater. Chem., 2012, 22: 24918; J. Mater. Chem. A, 2013, 1: 5949) and electrocatalytic materials for vanadium redox flow batteries (VRFBs) by using graphene materials. Based on the previous studies in high efficient graphene materials for vanadium ion redox reactions (Carbon, 2011, 49: 693; Energy Environ. Sci., 2011, 4: 4710), the scientists have also synthesized the RuSe/reduced graphene oxide composite materials for VO2+/VO2+ redox couples in VRFBs (RSC Adv., 2014, 4: 20379). QIBEBT researchers explored the flexible pyrolytic polyimide graphite film (PGF) as a cathode current collector in lithium ion batteries (LIBs) using lithium bis (trifluoromethane sulfonyl) imide (LiTFSI) based electrolyte. PGF possesses a highly in-plane oriented structure, which endows it with excellent electrochemical corrosion resistance and exhibits much better electrochemical stability than aluminum current collectors in LiTFSI based electrolyte. The result demonstrated that no obvious anodic current occurred up to 4.5 V versus Li+/Li for PGF, while significant corrosion current was found from 3.6 V for aluminum. This indicates that, in LiTFSI based electrolyte, PGF has better electrochemical stability than aluminum does. Furthermore, scientists tested LiMn2O4 on PGF and aluminum as a model electrode, respectively. With regard to the LiMn2O4/PGF electrode, the capacity retention ratio remained 89% after 1000 cycles. And at an elevated temperature of 55oC, the capacity retention ratio kept at 81% after 300 cycles. However, for the LiMn2O4/aluminum electrode, there is hardly any capacity retained after 10 cycles at room temperature (Electrochem. Commun., 2014, DOI: 10.1016/j.elecom.2014.05.001). 

Make Wastes Profitable: Products from Straw

A patent with number of ZL 201210259521.X was recently granted to the Chengdu Institute of Biology, CAS for its “method for production of acetone-ethano-butanol (ABE) from fermented straw”. The Advantage of the use of straw is one stone but two birds: on one hand, it provides a good solution to digest the straw, on the other, high-value products are made available, thus it contributed much to the solution on food safety and the environment. There are roughly about 7X108 tons of straw that could be used per year in China, which constitutes an abundant source for the productiion of ABE. To solve the problems existed in the complex detoxification technique, a new technology was developed for the production of acetone, ethanol and butanol, which includes the pre-treatment, enzymatic hydrolysis, preparation for fermentation medium, preparation of microbial seed inoculant, fermentation of ABE and the solvent distillation. The researchers increased the production output and efficiency by putting in FeSO4, 7H2O in the fermented units, which decreased the production cost and simplified the production process.