A High-Energy Lithium-Ion Capacitor by Integration of a 3D Interconnected Titanium Carbide Nanoparticle Chain Anode with a Pyridine-Derived Porous Nitrogen-Doped Carbon Cathode

Lithium-ion capacitors (LICs) are hybrid energy storage devices that have the potential to bridge the gap between conventional high-energy lithium-ion batteries and high-power capacitors by combining their complementary features. The challenge for LICs has been to improve the energy storage at high charge-discharge rates by circumventing the discrepancy in kinetics between the intercalation anode and capacitive cathode. In this article, the rational design of new nanostructured LIC electrodes that both exhibit a dominating capacitive mechanism (both double layer and pseudocapacitive) with a diminished intercalation process, is reported. Specifically, the electrodes are a 3D interconnected TiC nanoparticle chain anode, synthesized by carbothermal conversion of graphene/TiO₂ hybrid aerogels, and a pyridine-derived hierarchical porous nitrogen-doped carbon (PHPNC) cathode. Electrochemical properties of both electrodes are thoroughly characterized which demonstrate their outstanding high-rate capabilities. The fully assembled PHPNC//TiC LIC device delivers an energy density of 101.5 Wh kg^-1 and a power density of 67.5 kW kg^-1 (achieved at 23.4 Wh kg^-1), and a reasonably good cycle stability (≈82% retention after 5000 cycles) within the voltage range of 0.0-4.5 V. A hybrid Li-ion capacitor is developed using a pyridine-derived porous nitrogen-doped carbon cathode, 3D interconnected titanium carbide nanoparticle chains as the anode, and LiPF₆ as electrolyte. The demonstrated high energy and power densities of such a hybrid device can bridge the gap between Li-ion batteries and EDLCs.