Abstract
Li ion battery (LIB) and electrochemical capacitor (EC) are considered as the most widely used energy storage systems (ESSs) because they can produce a high energy density or a high power density, but it is a huge challenge to achieve both the demands of a high energy density as well as a high power density on their own. A new hybrid Li ion capacitor (HyLIC), which combines the advantages of LIB and Li ion capacitor (LIC), is proposed. This device can successfully realize a potential match between LIB and LIC and can avoid the excessive depletion of electrolyte during the charge process. The galvanostatic charge-discharge cycling tests reveal that at low current, the HyLIC exhibits a high energy density, while at high current, it demonstrates a high power density. Ragone plot confirms that this device can make a synergetic balance between energy and power and achieve a highest energy density in the power density range of 80 to 300 W kg−1. The cycle life test proves that HyLIC exhibits a good cycle life and an excellent coulombic efficiency. The present study shows that HyLIC, which is capable of achieving a high energy density, a long cycle life and an excellent power density, has the potential to achieve the winning combination of a high energy and power density.
Highlights
Based on the analysis of the chemical properties of LIB and LIC, in the present work, we proposed a new hybrid electrochemical device, which synergistically combines the advantages of LIBs and LICs and has the potential to significantly improve the performance of energy storage systems (ESSs)
We present here our study of the proposed energy storage device, hybrid Li ion capacitor (HyLIC), which has shown a high potential to satisfy the twin demands of high power and energy density facing to different operation condition, favorably demonstrating a diagonal characteristic on the Ragone plot
Nuclear Magnetic Resonance (NMR) spectroscopy was performed to analyze the stabilized lithium metal powder (SLMP) loading effect on hard carbon, with the spectra recorded using the prepared samples in a horizontal position with respect to the external applied magnetic field. 7Li NMR spectra were acquired at 233 MHz using a Bruker Avance I 600 MHz (14.1 Tesla) spectrometer
Summary
Commercial active materials were used for both the positive and negative electrodes as received. The slurry mixture of the negative electrode was made of hard carbon (HC, Carbotron P(J), Kureha, Japan) and 5% polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP) as a binder by the mass ratio of 92:8. The positive electrode based on AC was prepared by coating a slurry mixture of activated carbon (AC, AB-520, MTI Corporation) and PVDF binder in NMP solvent by the mass ratio of 9:1. The positive electrode based on LiCoO2 (EQ-Lib-LCO, MTI Corporation) was prepared by mixing 85% active material, 10% carbon black, and 5% PVDF in NMP. Nuclear Magnetic Resonance (NMR) spectroscopy was performed to analyze the SLMP loading effect on hard carbon, with the spectra recorded using the prepared samples in a horizontal position with respect to the external applied magnetic field. The energy density and power density are calculated based on electrode material weight (active materials and binder) of both the negative and the positive electrodes
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