Hollow Porous α-Fe₂O₃ Nanoparticles as Anode Materials for High-Performance Lithium-Ion Capacitors

Abstract

The lithium-ion capacitor (LIC) is a novel energy storage device, pairing battery-type anodes with capacitor-type cathodes, capable of delivering high energy and power densities. The anode materials of excellent high-rate capability, however, are required to resolve the common kinetics imbalance issue for high-performance LICs. A simple one-step solvothermal, metal–organic framework (MOF) evolved process was developed to synthesize hollow porous α-Fe2O3 nanoparticles (α-Fe2O3 HPNPs) as an anode material of excellent high-rate capability for high-performance LICs. The α-Fe2O3 HPNP anode achieved an excellent high-rate capability and cycling stability, through accelerating lithium-ion diffusions with the porous shell and shortening lithium-ion diffusion paths and buffering large volume variations during cycling with the confined hollow space. The quantitative kinetic analyses showed that capacitive processes are the main contributor to the capacity generation of the α-Fe2O3 HPNP anode, making the α-Fe2O3 HPNP an excellent match with capacitor-type cathodes, glucose-derived carbon nanospheres (GCNS) of high specific surface areas, for the assembly of LICs. The α-Fe2O3 HPNP//GCNS LIC delivered a high energy density of 107 Wh kg–1 at 0.24 W kg–1 and maintained an adequate energy density of 86 Wh kg–1 at an extremely high power density of 9.68 kW kg–1. Moreover, it exhibited a high capacity retention of 84% after 2500 cycle operations at 1 A g–1. Both materials and nanostructure of electrodes play a key role for high-performance LICs, and the hollow porous nanoparticulate structure is proven to be an advantageous nanostructure for the anode materials of LICs.

Tunable Synthesis of 3D Niobium Oxynitride Nanosheets for Lithium-Ion Hybrid Capacitors with High Energy/Power Density

“…With the increasing scan rates, the strength of the redox peak increases and shifts slightly, which is mainly caused by the trivial polarization. Due to its unique pseudocapacitive behavior, the current ( i ) in the CV measurements is related to the scan rate ( v ) , where a is an appropriate parameter. The b -value is a key parameter to distinguish the diffusion-controlled insertion process and the surface-limited capacitance behavior.…”

“…With the increasing scan rates, the strength of the redox peak increases and shifts slightly, which is mainly caused by the trivial polarization. Due to its unique pseudocapacitive behavior, the current (i) in the CV measurements is related to the scan rate (v) 9,50 i av b =…”

“…In addition, the service lifetime of LIBs may be obviously shortened while charging and discharging under high-current conditions. In comparison, electric double-layer SCs possess higher power densities and better durability due to the fast adsorption/desorption processes, but suffer from poor energy densities. − Fortunately, lithium-ion hybrid capacitors (LIHCs), which integrate the advantages of the aforementioned two kinds of electrochemical energy storage devices, could achieve high energy/power density and durable service life simultaneously. − Active materials commonly used for LIBs with typical faradaic electrochemical reactions to store energy will be adopted as one electrode for LIHCs, while the other electrode uses materials with capacitive characteristics, relying on the electric double-layer capacitance effect. − However, the electrochemical performance of LIHCs is still unsatisfactory because the kinetics of the Faraday reaction is slower than that of the electric double-layer process. The key to improve the performance of LIHCs is to design novel electrode materials that can balance the kinetic difference between the two electrodes. − …”

Ti3C2 MXene-Encapsulated NiFe-LDH Hybrid Anode for High-Performance Lithium-Ion Batteries and Capacitors

“…Generally, the cathode and anode materials for LICs usually select SC cathode materials and LIB anode materials, respectively . Currently, the kinetics imbalance of the anode and cathode is the most severe challenge for LICs . Hence, rational design of high-rate-capacity anodes is a severe challenge.…”

“…4 Currently, the kinetics imbalance of the anode and cathode is the most severe challenge for LICs. 5 Hence, rational design of high-rate-capacity anodes is a severe challenge.…”