Feasibility of High Surface Area Carbon-LiNi_0.5Mn_1.5O₄ Composite Cathode and Hard Carbon Anode for Lithium-Ion-Based Hybrid Devices

The development of Lithium-ion battery-supercapacitor hybrid devices, known as Lithium-ion capacitors (LICs), is a complex and rigorous process. Current research focuses on improving energy density without compromising cycle life and power density, which are essential criteria for LICs. The different ion-storing mechanisms and reaction kinetics between the two completely different types of electrodes in typical LICs can gradually decrease energy output. To address this, LICs are fabricated with high-rate-capable hard carbon (HC) as the anode and high-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO)-infused high-surface-area carbon (HSAC) as the cathode, introducing a partial intercalation mechanism at the cathode side. This combination has proven to be effective, offering high energy density even at high power (energy density of 68 Wh kg −1 at a power of 12240 W kg −1 ) with a capacity of 126 mAh g −1 even at 2 A g −1 for HC and improved charge storage capacity with a high operating voltage (4.9 V) for the (LNMO+HSAC) composite cathode. These findings demonstrate the importance of maintaining equilibrium between the capacity and kinetics imbalance between the electrodes to make energy-power-cycle life-balanced LICs.