Abstract
In this study, the importance of the preparation technique of Li4Ti5O12 (LTO) anode on its performance in a lithium-ion capacitor (LIC) application was investigated. These desired characteristics include energy density, rate capability, and cycle life. The samples were prepared using three approaches, and the same sol-gel synthesis procedure is applied to obtain phase-pure samples and keep the structural properties similar. The influence of these methods on the LTO anodes was then explored in both half-cell and full-cell LIC devices with an activated carbon (AC) cathode. It was observed that the samples had similar specific capacities and energy densities at low specific currents. However, significant differences were observed in the samples’ morphological properties, the rate capability, and the full-cell cycle life performance. Electrochemical impedance spectroscopy was used to identify the electrochemical kinetics and revealed that the LIC with the best performance was influenced by the LTO anode having the least charge transfer and diffusion resistances prepared using a surfactant. This was due to the small particle size, good particle dispersion, and high specific surface area of the LTO anode. This result points to the importance of the choice of synthesis technique in LIC material’s overall performance.
Highlights
The commercialization of lithium-ion capacitors (LICs) in recent years has led to a wide range of applications such as automotive, emergency power backup, security equipment, and military equipment, underlining the importance of improving this energy storage device [1,2,3]
The first major determining factor on how well an anode material will perform in the LIC system is its structural properties, and it significantly depends on the synthesis process
All the diffraction peaks of the samples were indexed as a cubic spinel structure with Fd-3m space group [14,28,29,30] with ions located at the tetrahedral 8a sites, and tetravalent ions and lithium-ions (Li+ ) were randomly distributed at octahedral 16d sites, whereas oxygen ions were located at the 32e sites [lithium’s electrochemical plating potential (Li)]8a [Li1/3 Ti5/3 ]16d [O4 ]32e
Summary
The commercialization of lithium-ion capacitors (LICs) in recent years has led to a wide range of applications such as automotive, emergency power backup, security equipment, and military equipment, underlining the importance of improving this energy storage device [1,2,3]. There is no comprehensive study reporting on the influence of these preparation methods of LTO on essential characteristics such as energy, power, and cycle life desired in LIC devices, to the best of our knowledge. Some of these methods have been reported in a half-cell and three-electrode cell format in separate literature works [22,26]. Still, they cannot provide a deep comparative understanding needed in selecting the better synthesis technique to obtain a high-performing LTO anode when designing LIC device. The effect of the preparation method on the LIC performance is analyzed and discussed
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