A Flame Retardant Gel Polymer Electrolyte Containing Mg(OH)2 Particles for Lithium Ion Battery

Abstract

Although lithium ion batteries (LIBs) as an energy storage device have been identified as the most promising candidate for large scale automotive and aerospace applications, safety issues still remain to be secured. Hence in order to improve the safety of LIBs, we introduce a new gel polymer electrolyte (GPE) containing the frame retardant material, magnesium hydroxide (Mg(OH)2). First, a dense polymer film of the thickness of 20 µm is prepared by casting the precursor solution consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) as a polymer matrix, dibutyl phthalate (DBP) as a pore generation agent, and Mg(OH)2 as a flame retardant agent, in acetone. And then, DBP is extracted in the methanol bath to make pores in the polymer film. They are gelled with additional liquid electrolyte, 1.15M LiPF6 in ethylene carbonate/ethyl methyl carbonate (EC/EMC, 3/7 by vol). Mg(OH)2 composited GPE exhibits a distinguished fire-retardant properties, which results in a relevant self-extinguishing time (SET) reduction. The ionic conductivity is also greatly enhanced in the GPEs with increasing ratio of Mg(OH)2. Due to the hydrophilic properties of Mg(OH)2, unit cells employing LiCoO2 cathode, the composite GPE, and graphite anode achieve significant improvements in rate capability and cycle performance that were closely associated with their improved uptake for liquid electrolyte. The electrochemical stability of the GPE with Mg(OH)2 is comparable to that without Mg(OH)2. This results imply that Mg(OH)2composited GPE can provide the large-format LIBs with greatly improved safety. Acknowledgements This work was supported by the Energy Technology Program of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20142010102980) Refernces 1. Daeyong Yeon , Yunju Lee , Myung-Hyun Ryou , Yong Min Lee, Electrochimica Acta 157 (2015) 282-289 2. Myung-Hyun Ryou, Yong Min Lee, Jang Wook Choi, Jung-Ki Park, Electrochemistry Communications 17 (2012) 18-21 3. Yong Min Lee, Dong-Hyun Ko, Jun Young Lee, Jung-Ki Park, Electrochimica Acta 52 (2006) 1582–1587