Research and development of a non flammable safety lithium ion battery

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Commercialized lithium ion batteries have several advantages for the energy storage devices, such as a high operating voltage, a high energy density and relatively good cycle durability. However, the use of a flammable and easily leaking liquid electrolyte is unavoidable in the present lithium ion cells. Many researchers have been developing the solid polymer electrolyte in order to raise safety of cells. However, the ionic mobility in electrolyte is greatly spoiled by the solidification of electrolyte, and the polymer battery which has practical performance is not obtained. In this project, aiming to develop a truly safe Li ion polymer cell with a good charge and discharge performance, we will develop a novel solid polymer electrolyte which has high ion-conductive and non-flammable polymer gel.We present a new design of a lithium gel-polymer battery, fabricated with a (LILP) composite consisting of a lithium salt dissolved in an ionic liquid (binary Li-IL) and an ultra high molecular weight ionic liquid polymer (ILP). This polymer, with a Mw of over a million, was prepared by the bulk radical polymerization of a novel ionic liquid monomer, N, N-diethyl-N- (2-mthacryloylethyl)-N-methylammonium bis (trifluoromethylsulfonyl) imide (DEMM-TFSI). The polymer could form a binary Li-IL solid at a concentration of only 5 wt%. We selected high power-active electrode materials, and combined them with the LILP system. The demonstration vapor-free cell had a higher discharge performance than a conventional lithium polymer battery: at 40℃, it retained 83% of its discharge capacity at a 3C current, and relatively good cycle performance. This is the first report of to knowledge that a lithium ion cell with a LILP system performed, in terms of cell performance and cycle durability, at a level of practical utility.