Solid-state supercapacitors using ionic liquid dispersed Li+-NASICONs as electrolytes

Ceramic ionic conductors exhibit inadequate ionic conductivity for device applications. However, when added with a small amount of ionic liquid (IL), exhibit a substantial conductivity rise. This research demonstrates the use of such IL-ceramic composites, with IL content <= 13 wt%, for capacitor applications. These supercapacitors are designed using IL dispersed Li+ ion conducting fast ionic ceramics as an electrolyte, viz; LiTi2(PO4)(3) (LTP) and Li1.3Al0.3Ti1.7(PO4)(3) (LATP). The cells are fabricated in 2032-coin cells using these composites and activated charcoal coated on the copper foil as the electrode. A typical supercapacitor containing LATP-13 wt% EMIM BF4 as electrolyte at similar to 35 degrees C exhibits high specific capacitance of similar to 181 F-g(-1), specific energy similar to 6.1 Wh-kg(-1), and power of similar to 140 W-kg(-1) at 0.65 mA/cm(2) (0.56 A-g(-1)) and 1 V. Importantly, the choice of IL (size of the ions), as well as the composition of fast ionic ceramic, influences the device performance. For a discharge at 0.56 A-g(-1), a supercapacitor with this composite electrolyte exhibit stability at least up to similar to 13,000 charge/discharge cycles with a fairly stable coulomb efficiency of similar to 99%. At similar to 100 degrees C these cells exhibit a maximum specific capacitance up to similar to 600 F-g(-1). These supercapacitors exhibit appreciable cycling performance at 30-100 degrees C. At higher discharge currents (>= 0.34 A-g(-1)) electric double layer capacitor behavior is witnessed. A stack of two cells is able to glow a white light-emitting diode (3 V) successfully for similar to 30 min.

Automated summary

This research demonstrates the use of IL-ceramic composites for capacitor applications, which exhibit improved ionic conductivity when a small amount of ionic liquid (IL) is added to ceramic ionic conductors. The choice of IL and composition of fast ionic ceramic influence the performance of the device.