The renewable biomass materials have important application prospect in the field of sustainable energy materials. In the vast blue ocean, there are abundant of seaweed polysaccharides, chitin and other biomass materials. Based on these marine biomass materials, high performance energy materials have been developed, which have important ecological, economic and social benefits.

The Biomimetics for Energy Storage Group at Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences has developed lithium ion battery (LIB) separators using cellulosic biomass materials and thermostable polymeric materials by nonwoven technology for electric vehicles (EVs) & hybrid electric vehicles (HEVs) (ACS Appl Mater. Inter. 2013, 5, 128-134). This separator has a unique chemical and physical structure, which is beneficial for the access of electrolyte, favor of the migration of lithium ions and the transport of electron. Moreover, the separator exhibits very exciting thermal stability at high temperature. So far, the key technical issues have been solved by optimizing the material design and integrating innovation of the molding process. Three patents have been authorized in the crucial materials and equipment (ZL201110147715.6，ZL201110147725.X，ZL201220602823.8).

It is crucial to develop high performance LIB separators with low cost, superior thermal stability and enhanced flame retardancy. The polysulfonamide/sodium alginate/silica composite separator has been developed (J. Electrochem. Soc., 2013, 160 (6), A769-A774). The batteries using polysulfonamide-based composite separator show excellent charge-discharge behavior and satisfactory cycle stability even at a high temperature of 120 oC. These advanced characteristics would boost the application of polysulfonamide-based composite separator for high-power LIBs.

Polyvinylidene fluoride, which is a non-aqueous soluble binder, has been widely applied in the preparation of electrode for LIB. But during the preparation of slurry, large amount of methyl pyrrolidine is used as solvent. Other disadvantages, such as high production cost, environmental pollution, low Young's modulus, brittleness, poor flexibility and low tensile strength, are also difficult to handle. The electrodes using such kind of binder often suffer from power-material-falling phenomenon and material-cracks during the charge-discharge process. Marine biomass materials (such as sodium alginate, chitin, carrageenan) possess advantages like low cost, abundant and excellent adhesion properties. Nevertheless they exhibited poor film-forming property. The team has developed a novel aqueous soluble binder through functional modification of the marine biomass materials. Such binder with high elastic modulus, economic and environmental friendly can withstand the expansion and contraction of the electrode active material particles during cycling. It is particularly suitable for high potential positive electrode materials and silicon-based electrode materials which have high energy density. So far, four patents have been applied.

Traditional electrolytes (LiPF6) have some disadvantages, such as high cost, poor thermal stability and extremely sensitive to water. So we have designed and synthesized novel biomass lithium borate salts (Electrochim Acta 2013, 92, 132-138). The raw material is abundant in nature. Furthermore, the synthesis process is preceded via a one-step reaction in aqueous solution. The obtained polymer electrolyte exhibits highly thermal stability, better electrochemical stability and high ionic conductivity. These fascinating characteristics would endow this polymer electrolyte a promising separator for power LIB in military or space fields. Two patents have been applied.

Based on the technological breakthroughs in high performance separator, electrolyte salt and binder, supercapacitors with high energy density and high power density have been developed by employing an advanced technology of pre-doing lithium ions. In such devices, nanostructured metal nitrides are used as electrode materials. The interface between electrode and electrolyte is stabilized by virtue of the biomasscellulosemembrane and the additives in the electrolyte. The energy density of the supercapacitors is as high as 30Wh/kg, which is comparable to that of lead acid batteries (J. Mater. Chem., 2012, 22, 24918; J. Mater. Chem. A, 2013, 1, 5949; ACS Nano, 2013, DOI: 10.1021/nn401402a). The research team is now optimizing the device configuration and developing lithium ion capacitors with excellent performance under the support of the 863 Project. Four patents have been authorized up to now (ZL200910226430.4, ZL201010104001.2, ZL201010104003.1, ZL201010108048.6)

The research was supported by National Basic Research Program of China (973), National High Technology Research and Development Program (863), Natural Science Foundation of China, and “Strategic Priority Research Program” of the Chinese Academy of Sciences.

Contact:

Prof. CUI Guanglei
Email: cuigl (AT) qibebt.ac.cn