Quasi-Solid State Electrolytes for Li-Ion Battery Applications

High energy density secondary batteries are key devices for mobile industrial applications such as electric vehicles, drones and robots. Among attractive new device concepts such as lithium- air, lithium- sulfur, Na/Mg ion and all solid state battery (ASSB), ASSB has been considered to be most promising due to their higher energy density, higher cell output voltage and superior chemical/thermal safety. In this paper, our original approach to electrolyte materials are reported, which are synthesized by hybridization of ionic liquid and nanoparticles. In fact, the quasi-solid state electrolytes have been made by solidification of Li ion conducting ionic liquid by mixing with SiO2 nanoparticles due to strong interaction between ionic liquid molecules and SiO2 surface, which resulted in the electrolytes having liquid-like ionic conductivities in their solid state matrix. All solid state Li battery cell consisting Li metal anode/quasi-solid state electrolytes/LiFePO4 cathode have been successfully fabricated and demonstrated stable charge /discharge cycles more than a thousand under 1.0C-rates in spite of their solid state cell design. More importantly, it has been demonstrated for the first time, bipolar stacked tripled cells with multiple voltages up to 10V are successfully demonstrated on the coin cell CR2032 devices. references [1] Seitaro Ito, Atsushi Unemoto, Hideyuki Ogawa, Takaaki Tomai, and Itaru Honma, J. Power Sources, 2012, 208, 271 [2] Atsushi Unemoto, Hideyuki Ogawa, Seitaro Ito and Itaru Honma, J. Electrochemical Society, 2013, 160, A138 [3] Takaharu MATSUO, Yoshiyuki GAMBE and Itaru HONMA, Scientific Reports,2014,4,6084 [4] Yoshiyuki Gambe, Yan Sun and Itaru Honma, Scientific Reports, 2015, 5, 8869 Figure 1