High-Performance Li-Ion and Na-Ion Capacitors Based on a Spinel Li₄Ti₅O₁₂ Anode and Carbonaceous Cathodes

Lithium-ion hybrid capacitors (LICs) have become promising electrochemical energy storage systems that overcome the limitations of lithium-ion batteries and electrical double-layer capacitors. The asymmetric combination of these devices enhances the overall electrochemical performance by delivering simultaneous energy and power capabilities. Lithium titanate (Li₄Ti₅O₁₂, LTO), a spinel zero-strain material, has been studied extensively as an anode material for LIC applications because of its high-rate capability, negligible volume change, and enhanced cycling performance. Here, the different synthetic methods and modifications of the intercalation-type LTO to enhance the overall electrochemical performance of LICs are mainly focused. Moreover, the cathodic part (i.e., the activated carbon derived from various sources, including natural products, polymers, and inorganic materials) is also dealt with as it contributes substantially to the overall performance of the LIC. Not only do the anode and cathode, but also the electrolytes have a substantial influence on LIC performance. The electrolytes used in LTO-based LICs as well as in flexible and bendable configurations are also mentioned. Overall, the previous work along with other available reports on LTO-based LICs in a simplified way is analyzed.