Lithium-Ion Capacitors and Hybrid Lithium-Ion Capacitors—Evaluation of Electrolyte Additives Under High Temperature Stress

Lithium-ion capacitors (LICs) and Hybrid LICs (H-LICs) were assembled as three-layered pouch cells in an asymmetric configuration employing Faradaic pre-lithiated hard carbon anodes and non-Faradaic ion adsorption-desorption activated carbon (AC) cathodes for LICs and lithium iron phosphate (LiFePO4-LFP)/AC composite cathodes for H-LICs. The room temperature rate performance was evaluated after the initial LIC and H-LIC cell formation as a function of the electrolyte additives. The capacity retention was measured after charging at high temperature conditions, while the design factor explored was electrolyte additive formulation, with a focus on their stability. The high temperature potential holds simulate electrochemical energy materials under extreme environments and act to accelerate the failure mechanisms associated with cell degradation to determine robust electrolyte/additive combinations.