Membranes Made from Electrospun Polyacrylonitrile Nonwoven Fibers with Uniform Diameter for Lithium-Ion Battery Separato
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ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version)
Membranes Made from Electrospun Polyacrylonitrile Nonwoven Fibers with Uniform Diameter for Lithium-Ion Battery Separators Ting Dong1, Waqas Ul Arifeen1, Minchoel Kim1, Jungwook Choi1, Kisoo Yoo1, and Tae Jo Ko1* Department of Mechanical Engineering, Yeungnam University, Gyeongsan 38541, Korea (Received November 16, 2019; Revised January 13, 2020; Accepted January 22, 2020) Abstract: Membranes were prepared from polyacrylonitrile (PAN) fibers with uniform diameter for lithium-ion battery separators using optimized electrospinning parameters. In this work, the coefficient of variation (CV) is proposed as one of the indexes to evaluate the uniform consistency of fiber diameter. The most uniform fibrous membrane was compared with a control group that had different uniformity. The effects of the uniformity of the fiber diameter were studied in terms of the membrane porosity, electrolyte absorption, mechanical tensile strength, and thermal stability. The membranes were assembled into coin cells with lithium cobaltite cathodes and graphite anodes, and the performance of the cells was tested. As the uniformity of the fiber diameter increased, the ionic conductivity improved and the interface resistance decreased. The proposed separator improves the discharge capacity (181 mAh·g-1 at the 0.2C rate), C-rate cycling performance, and Coulombic efficiency (99.64 %), which indicates that the uniform membrane could be a candidate for high-performance lithium-ion battery separators. Keywords: Uniform, Diameter, Polyacrylonitrile, Lithium-ion battery, Separator
non-woven fabric could improve the performance of a battery separator. Consequently, electrospinning has been widely used in the preparation of fibrous membranes for the separators in lithium-ion batteries in recent years [15-20]. Electrospinning can be used to obtain a membrane with adjustable morphology and porosity by changing the spinning conditions [21-23]. Polyacrylonitrile (PAN) is commonly chosen as a desirable material for electrospinning due to its dielectric constant, ionic conductivity, liquid electrolyte absorption, electrochemical stability, and compatibility with the electrodes [24-28]. Moreover, the electrochemical stability of the liquid electrolyte-immersed PAN membrane is higher than that of the commercial Celgard separator [15, 21]. The diameter uniformity of fibers used to make a separator has a significant influence on the ionic conductivity and capacity of the resulting battery. Controlling the internal structure of fibrous membranes can effectively inhibit the formation of straight-through pores in the membranes and provide tortuous paths to allow ions to pass through [21]. It also prevents short circuits between the cathode and anode and ultimately suppresses the explosion of batteries. Thus, electrospun polyacrylonitrile nonwoven membranes with uniform fiber diameter for lithium-ion batteries separators should be achieved to obtain a high-performance battery. However, the fibrous
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