Lithium-ion Battery Separators Develop Fast in China   

By Li Shun, Energy Storage Material Information Center, CNCIC

Eighty percent of the lithium-ion battery separators used in China are imported

Compared to other rechargeable batteries, lithium-ion batteries feature high energy density, long cycle life, small self-discharge rate, no memory effect and environmental friendliness. Since the first commercial lithium-ion battery was launched by Sony in 1992, it has become a superstar among chemical batteries. As one of the key materials for lithium-ion batteries, the separators between the anodes and cathodes account for nearly 1/3 of the cost of the battery, and its performance determines the battery's internal resistance and interface structure, thereby affecting the battery's capacity, cycling performance and safety. China has become more or less self-sufficient with regard to lithium-ion battery materials in recent years except for separators, especially those for high-power batteries.
   According to statistics, in 2010 the global output of lithium-ion battery separator materials was 351 million square meters, up 38% year on year; and the demand for the separators in China alone reached more than 120 million square meters. With the development of the electric vehicle market, the demand for separators will increase substantially. According to Taiwan Industrial Technology Research Institute's forecast, the global demand will reach 563 million square meters in 2013. Major separator producers around the world are currently expanding their production capacity and will likely double their capacity in the next two years. China imports 80% of the separators it needs, so domestic substitutes have huge growth potential.
   The separators are mainly microporous membranes made from porous polyolefin and are of three types: single-layer polypropylene (PP), single-layer polyethylene (PE), and multilayer PP/PE. As polyolefin has excellent mechanical properties, good chemical stability and low cost, it has been the main material for making the separators. Existing polyolefin membrane production processes are mostly either "the dry process" or "the wet process." As an alternative to polyolefin, ceramics are also used to make separators. Now, ceramic separators have been commercialized. Evonik owns the patent of ceramic separator SEPARION? Currently, Evonik is cooperating with Daimler Group on this technology, and they have set up a joint venture, Li-Tec Battery GmbH (Evonik and Daimler Group hold 50.1% and 49.9% respectively). The joint venture plans to use the Evonik ceramic separator technology to produce vehicle-purposed and industrial power lithium-ion batteries. The ceramic separator has excellent electrochemical properties but is costly and easily broken while in use. In contrast, due to their high cost-performance ratio, polyolefin separators are widely recognized by users.
　　Currently, major global polyolefin separator manufacturers are: Celgard (holding the patent of the one-way stretch dry manufacturing process), UBE (Japan), Asahi Kasei (Japan), Tonen Chemical (Japan), Sumitomo Chemical, Entek (USA) and SK (Korea) (see Table 1).

Table 1 Major global polyolefin separator producers (million square meters /year)
Manufacturer    Structure    Composition    Process    Brand    Capacity

Asahi Kasei    Single layer    PE    Wet    Hipore    170
Celgard    Single layer    PP, PE    Dry / Wet    Celgard    70
    Multi-layer    PP/PE/PP    Dry    Celgard    
    PVDF coverage    PVDF, PP, PE, PP/PE/PP    Dry    Celgard    
Entek    Single layer    PE    Wet    Teklon    11
Tonen Chemical    Single layer    PE    Wet    Setela    68
UBE    Multi-layer    PP/PE/PP    Dry    U-Pore    24
Sumitomo Chemical    Multi-layer    Polyolefin / aromatic polyamide        PERVIO    16
SK    Multi-layer    PP/PE/PP    Dry        15
    Single layer    PE    Dry        
TDK / Nitto Denko    Single layer    PE    Wet    SUNMAP    -
　　
    In 2011, these companies still dominate the global lithium-ion battery separator market. Asahi Kasei controls about 22% of the global market, Celgard 22%, Tonen Chemical 20%, UBE 10%, Entek 6%, SK 12%, Sumitomo Chemical 1%, and Nitto Denko about 1%. The remaining market share (about 6%) is enjoyed by Chinese companies.


Production capacity of separators grows fast in China

Chinese companies (such as Shenzhen Senior Technology Material Co Ltd and Foshan Jinhui Hi-Tech Photoelectric Material Co Ltd) and research institutes (such as the Institute of Chemistry, Technical Institute of Physics and Chemistry, and Guangzhou Institute of Chemistry, all under the Chinese Academy of Sciences (CAS)) have never stopped developing advanced battery separators. Major battery separator producers in China are Shenzhen Senior Technology Material Co Ltd, Foshan Jinhui Hi-Tech Photoelectric Material Co Ltd, and Xinxiang Green New Energy Material Co Ltd (see Table 2). Overall, separators produced by the Chinese companies are of relatively low quality and are mainly incorporated in medium and low-end batteries.

Table 2  Major separator manufacturers in China in 2010 (million square meters /year)
Producer    Capacity    Remark
Shenzhen Senior Technology Material Co Ltd    40    A new project with a capacity of 50 million square meters /year is under construction, and is expected to be completed by 2013
Foshan Jinhui Hi-Tech Photoelectric Material Co Ltd    12    Plan to expand the capacity to 45 million square meters /year
Xinxiang Green New Energy Material Co Ltd    35    Plan to expand the capacity to 60 million square meters /year
Guilin New Times Technology Co Ltd    6    
Shandong Zhenghua Membrane Technology Co Ltd    5    
Changzhou Zhongke Laifang Energy Development Co Ltd    -    The project was put into production in May 2009. Its capacity is unknown
Nantong Tianfeng Electronics Materials Co Ltd    30    
Taiwan Coin Chemical Co Ltd    4.52

   In addition, at least 20 other Chinese companies have been built or are building battery separator production lines, including: Suqian Jinghong Color Printing & Packing Co Ltd, Jiangsu Jiujiujiu Technology Co Ltd, Changzhou Xunteng Electronic Technology Co