Effects of carbon black on the electrochemical performances of SiOx anode for lithium-ion capacitors

Lithium-ion capacitor (LIC) is a power-type energy storage device, possessing the advantages of high energy density, high power density, long cycle life and wide working temperature range. Silicon-based anode materials for LICs have ultrahigh theoretical specific capacities, about 5-10 times higher than traditional graphite anode. However, since silicon-based materials are semiconductors and the electrical conductivity is limited, the imbalance in reaction kinetics between the rapid non-Faradaic capacitive cathode and sluggish Faradaic redox anode is one of the main barrier to high-performance LICs. In this work, the effects of carbon conductive additive on the electrochemical performances of SiOx anode have been studied. Carbon black (CB, Super C45) shows good electrical conductivity and moderate initial coulombic efficiency, suitable for the conductive additive of SiOx anode. Due to the conducting network and the buffer space for volume expansion/contraction during lithiation/de-lithiation, the combination of CB and SiOx particles play a synergetic effect on improving rate capability and cycling stability of SiOx anode. The reversible specific capacity of SiOx anode containing 30 wt% CB can reach 1549 mAh g(-1) in the voltage range of 0.01-2.0 V. It remains no capacity decay after 500 cycles in the shallow voltage range of 0.1-0.6 V, indicating that SiOx is a very promising anode material for LICs.