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.