Design and Synthesis of CoP/r-GO Hierarchical Architecture: Dominated Pseudocapacitance, Fasted Kinetics Features, and Li-Ion Capacitor Applications

The lithium-ion capacitors (LICs) become potential energy storage devices because they have both outstanding energy density of lithium-ion batteries (LIBs) and excellent power density of supercapacitors (SCs). However, significant challenges such as the discrepant energy-storage mechanism of the anode and the cathode material must be addressed for their practical applications. We reported a method to enhance the electrochemical kinetics of CoP by combining with reduced graphene oxide(r-GO) conductive network and designed the 3D urchin-like CoP nanorods that reduce the volume expansion of CoP during Li+ insertion/extraction. The resulting prepared high capacitive characteristic 3D CoP/r-GO nanocomposite electrode delivered a specific capacity of 510 mAh g–1 at 0.1A g–1 after 500 cycles in a LIB half-cell, and its b value is up to 0.93 by kinetic calculation. The LIC device assembled with the 3D CoP/r-GO nanocomposites anode and activated carbon (AC) cathode, it provided a distinctive energy density of 119.3Wh kg–1 (current density is 0.1A g–1) and power density of 8400 W kg–1 (current density is 4.8A g–1). This result indicates that the energy density and power density of LICs can be enhanced by improving the dynamic characteristics of the electrode material.