High energy density solid state symmetric supercapacitors using ionic liquid dispersed Li⁺ ion-perovskites

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Solid-state ceramic supercapacitors (SSCs) offer safer alternatives to liquid electrolyte-based devices.
• Lithium lanthanum titanium oxide (LLTO) is a promising solid electrolyte but suffers from low ionic conductivity.
• Ionic liquids (ILs) can enhance ionic conductivity and improve electrode interface properties.

Purpose of the Study:

• To develop a novel composite electrolyte for solid-state ceramic supercapacitors.
• To improve the ionic conductivity and electrochemical performance of LLTO-based electrolytes.
• To fabricate and characterize high-performance SSCs for practical energy storage applications.

Main Methods:

• A composite electrolyte was synthesized using perovskite-type LLTO (Li_0.34La_0.51TiO₃) and an ionic liquid (EMIM BF₄).
• Various ionic liquids were incorporated into LLTO to optimize ionic conductivity and electrode compatibility.
• SSCs were fabricated using the optimized electrolyte and activated carbon-coated copper electrodes in a lamination cell.

Main Results:

• The optimal composite electrolyte (∼6 wt% EMIM BF₄ in LLTO) achieved high ionic conductivity (∼10^-3 Ω^-1 cm^-1) at room temperature.
• The fabricated SSCs demonstrated stable cycling for over 10,000 cycles at 2 V with high coulombic efficiency (∼99%).
• A typical cell achieved a specific capacitance of 510 F g^-1 at 0.57 A g^-1 and 2 V, capable of powering LEDs.

Conclusions:

• The novel LLTO-EMIM BF₄ composite electrolyte significantly enhances ionic conductivity for SSCs.
• The developed SSCs exhibit excellent stability, high capacitance, and potential for practical low-power applications.
• This work presents a viable pathway for creating efficient and safe solid-state energy storage devices.