4.4 V lithium-ion polymer batteries with a chemical stable gel electrolyte

• Published in: Journal of power sources Vol. 174; no. 2; pp. 1036 - 1040
• Main Authors: Yamamoto, Takeru, Hara, Tomitaro, Segawa, Ken, Honda, Kazuo, Akashi, Hiroyuki
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 06.12.2007; Elsevier Sequoia
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; High voltage; Lithium-ion polymer battery; Poly(vinylidene fluoride); High voltage; Poly(vinylidene fluoride); Lithium-ion polymer battery; Lithium battery; Infrared spectrometry; Cathode; Polymer gels; Vinylidene fluoride polymer; Ionic conductivity; Energy density; Secondary cell; Oxidation
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2007.06.212

We tested 4.2 V Li-ion polymer batteries (LIPB) with physical gel electrolyte, poly(vinylidene fluoride) (PVDF), 4.4 V LIPB and 4.4 V Li-ion batteries (LIB) with a liquid electrolyte. The discharge capacity of the 4.4 V LIPB reached 520 Wh l −1 which was 9% higher than that of the 4.2 V LIPB. The 4.4 V LIPB had a high capacity retention ratio of 91.4% at 3 C because of the excellent ion conductivity of the PVDF gel. The capacity retention ratio of the 4.4 V LIPB was 82% after 500 cycles, which is comparable to those of some commercial LIBs. The 4.4 V LIPB retained its original thickness even after many cycles and after being stored at 90 °C, whereas the 4.4 V LIB swelled by over 20%. Peaks in the FT-IR spectrum of the discolored separator in the 4.4 V LIB after storage were assigned to C C double bonds, suggesting that the separator in direct contact with the 4.4 V cathode had been oxidized. The PVDF gel electrolyte not only had a high ionic conductivity but also completely suppressed oxidation. The 4.4 V LIPB with PVDF gel electrolyte has properties suitable for practical cells, namely, high energy density, high permanence and it is safe to use.