Research progress in low-temperature lithium-ion capacitors

Lithium-ion capacitors (LICs) utilize cathode materials of electrical double-layer capacitors and anode materials of lithium-ion batteries, which could combine their advantages of high energy density, high power density, and long cycle life. In recent years, LIC has developed rapidly and has been applied in many fields, such as power storage and new energy transportation. However, while possessing these advantages, it also inherits the poor low-temperature performance of lithium-ion batteries, severely limiting its widespread application. In some occasions, the viscosity of electrolyte may increase or even solidify, affecting the normal transportation and charge transfer of ions. increase in impedance prevents the normal operation of the LIC, severely limiting its all-weather applications. Improving the low-temperature performance of LIC has become an urgent issue, has received widespread attention from all walks of life. Electrodes and electrolytes are the main components of LIC, numerous studies have shown that the relationship between electrode and electrolyte directly determines the energy storage process of LIC at low temperature. Therefore, this article reviews the recent research progresses on the design and fabrication of low-temperature LIC from the viewpoint of electrode and electrolyte, Firstly, the research on key electrode materials for high-performance low-temperature LIC is discussed, including chemical modification, surface modification, ion insertion, and the development of new electrode materials for rapid intercalation of traditional carbon-based materials. Secondly, the electrolyte system that matches the electrode material is also critically reviewed. Starting from the main components of the electrolyte - lithium salts, solvents, and additives - this article summarizes the past year's progress on low-temperature electrolytes in LICs. Emphasis was placed on additives for LIC electrolyte, which, as the essence of the entire electrolyte system, are the most controllable factor in the entire electrolyte system and currently the most available factor for selection. They can reduce the viscosity of the electrolyte with minimal content and improve the low-temperature charging and discharging ability of LIC. Commonly used low-temperature additives such as FEC, VC, PS, LiODFB all demonstrate excellent low-temperature performance. The article concludes by summarizing the research progress of the new generation of low-temperature electrolytes, and provides a tentative outlook toward next-generation LICs with a wide temperature range.