High Rate Capability of All-Solid-State Lithium Batteries Using Quasi-Solid-State Electrolytes Containing Ionic Liquids

Here we demonstrate a high rate capability of all-solid-state lithium batteries using quasi-solid-state electrolytes containing an ionic liquid. We fabricated solid-state electrolyte using an ionic liquid: 1 mol l(-1) lithium bis(fluorosulfonyl) imide dissolved 1-Ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (LiFSI/EMI-FSI) and fumed silica nanoparticles with a variety of volume fractions. The fabricated freestanding film with 85% volume fraction of LiFSI/EMI-FSI exhibited an ionic conductivity and self-diffusion coefficient of lithium-containing species; 10.2 mS cm(-1) and 3.3 x 10(-11) m(2) s(-1) at 35 degrees C. We revealed that the increase in the volume fraction of the LiFSI/EMI-FSI led to the decrease in concentration polarization resistance, leading to an enhanced rate capability in Li vertical bar LiFePO4 batteries. The fabricated Li vertical bar LiFePO4 batteries using freestanding electrolyte films with 85 vol% LiFSI/EMI-FSI exhibited a high capacity (>150 mAh g(-1)) at 1 C (0.6 mA cm(-2)) based on that at 0.1 C. Further, we fabricated bipolartype all-solid-state lithium batteries assembled by stacking of Li vertical bar LiFePO4 cell components in a single package. The bipolar-type lithium batteries exhibited the increased packing energy density, depending on the number of stacked cells. These results open opportunities of designing all-solid-state lithium batteries for high energy and power density using quasi-solid-state electrolytes. (c) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.