Study on preparation of polyacrylonitrile/polyimide composite lithium-ion battery separator by electrospinning
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Study on preparation of polyacrylonitrile/polyimide composite lithium-ion battery separator by electrospinning Lin Li1
, Ping Liu1, Qin Shan Fu1, Yong Gong1, Shi Rong Zhang1, Heng Ji He1, Jian Chen1,a)
1
Material Corrosion and Protection Key Laboratory of Sichuan Province, Sichuan University of Science and Engineering, Zigong 643000, China Address all correspondence to this author. e-mail: [email protected]
a)
Received: 25 September 2018; accepted: 2 January 2019
Compared with commercial polyolefin membranes, polyacrylonitrile (PAN) membrane prepared by electrostatic spinning has higher porosity, electrolyte uptake, thermal stability, and lithium-ion conductivity, etc. However, poor mechanical performance has largely limited the application of electrospun PAN separators. In this study, PAN/polyimide (PI) composite membrane is prepared by electrostatic spinning to improve the mechanical and electrochemical performances. Scanning electron microscopy, thermal analysis method, and electrochemical methods were used for evaluation of the electrospun composite membrane. The results show that the composite membrane possesses good thermal stability and exhibits better mechanical performance than pristine PAN membrane (increasing by 1.1 times in tension strength). The addition of PI can increase porosity and fluid absorption rate obviously. In addition, the composite membrane has high ionic conductivity (18.77 × 10−4 S/cm), wide electrochemical window (about 4.0 V), and excellent cycling performance. It can retain a discharge specific capacity of 153 mA h/g even after 50 cycles at 0.5 C. The electrospun PAN/PI membrane may be a promising candidate for lithium-ion battery separators.
Introduction The separators play a key role in lithium-ion battery. It isolates the positive and negative electrodes and allows Li1 ions to pass quickly during charge and discharge [1]. The separators are insulated and have low electrical resistance, good dimensional stability, mechanical strength, good lyophilicity, and small thickness, etc. [1, 2, 3]. Nowadays, the Celgard separators are usually adopted in commercial lithium-ion batteries due to their chemical stability and mechanical property. However, the Celgard separator shows poor liquid absorption rate, liquid retention rate, and thermal stability [2, 3, 4]. When the battery is overcharged or misused, it is easy to get out of control and cause a safety accident [5, 6]. Herein, improving the safety of lithium-ion battery is becoming a hot topic. Ji et al. modified the electrolyte to improve the safety of battery, and the results reveal that the modified electrolyte allows the battery to have enough time to release heat and avoid thermal runaway of the battery [7, 8]. Liu et al. fabricated a composite membrane (SiO2@PI/PE/PI@SiO2) containing a high melting point phase and a low melting point phase [9]. When the temperature
ª Materials Research Society 2019
reached 135 °C, the middle polyethylene (PE) layer melted and closed the micropores to isolate cathode and anode, and the top and b
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