"Liquid-in-Solid" and "solid-in-Liquid" Electrolytes with High Rate Capacity and Long Cycling Life for Lithium-Ion Batteries

Herein we present a new class of ionogel electrolyte for lithium-ion batteries, which can be prepared in either "liquid-in-solid" or "solid-in-liquid" form. The electrolytes are prepared by a nonaqueous self-assembly sol-gel process, in which ionic liquid electrolyte is immobilized within an inorganic gel. These electrolytes were found to exhibit high ionic conductivity, low electronic conductivity, and good thermal and mechanical stability. The inorganic gels weaken the interaction of anions and cations and thereby improve lithium salt dissociation and enhance transport of Li⁺. Also, the electrolytes are stable: no spontaneous phase separation occurs after 1 year of storage. In addition, their synthesis and shaping are very easy and cheap and form a new class of solid electrolytes, which offer exciting opportunities for preparation of in situ solid-state lithium-ion batteries. Cells with LiFePO₄ cathodes and ionogel electrolyte attained a capacity of 150 mAh/g for more than 300 cycles, and even at the 2C rate, the capacity still stayed over 98 mAh/g. There are no prior reports of solid-state batteries employing ionogel electrolyte that exhibit high capacity.