Investigation of a Difunctional Electrolyte Engineered for Capacitor Batteries

Recently, the rapid advancement of electric vehicles has resulted in a growing demand for enhanced battery performance, particularly in application scenarios that necessitate fast (dis)charging properties and ultralong cycle life. The capacitor lithium-ion batteries, which fully leverage the synergistic advantages of a double electric layer and redox reaction storage mechanisms of lithium-ion batteries to optimize both energy and power properties, are poised to play a significant role to meet these requirements. Herein, this paper designs a difunctional electrolyte and investigates its effects on the electrochemical behaviors within a capacitor lithium-ion battery. The objective of this study is to develop functional electrolytes for capacitor lithium-ion batteries tailored for carbon-rich systems with dual energy storage mechanisms. The capacitor lithium-ion battery comprising LiNi0.6Co0.2Mn0.2O2-activated carbon (cathode)||hard carbon (anode) demonstrates attractive performance, while utilizing a difunctional electrolyte system of LiPF6 and tetraethylammonium tetrafluoroborate. With the additives of vinylidene carbonate and fluorinated ethylene carbonate, the batteries exhibit commendable reversible capacities of 111.5 and 116 mAh/g at 180 mA/g, respectively, with capacity retention rate exceeding 90% after 100 cycles. Consequently, this research provides both theoretical and technical support for the advancement of capacitor lithium-ion batteries characterized by a wide operating temperature range, extended lifespan, and enhanced safety.