Carbon-coated lithium titanate: effect of carbon precursor addition processes on the electrochemical performance
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RESEARCH ARTICLE
Carbon-coated lithium titanate: effect of carbon precursor addition processes on the electrochemical performance Shilei Ding (✉)1, Zelong Jiang1, Jing Gu2, Hongliang Zhang3, Jiajia Cai1, Dongdong Wang1 1 School of Energy and Environment, Anhui University of Technology, Maanshan 243002, China 2 School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan 243002, China 3 Analysis and Testing Central Facility, Anhui University of Technology, Maanshan 243002, China
© Higher Education Press 2020
Abstract In this paper, two carbon-coated lithium titanate (LTO-C1 and LTO-C2) composites were synthesized using the ball-milling-assisted calcination method with different carbon precursor addition processes. The physical and electrochemical properties of the as-synthesized negative electrode materials were characterized to investigate the effects of two carbon-coated LTO synthesis processes on the electrochemical performance of LTO. The results show that the LTO-C2 synthesized by using Li2CO3 and TiO2 as the raw materials and sucrose as the carbon source in a one-pot method has less polarization during lithium insertion and extraction, minimal charge transfer impedance value and the best electrochemical performance among all samples. At the current density of 300 mA$h$g–1, the LTO-C2 composite delivers a charge capacity of 126.9 mA$h$g–1, and the reversible capacity after 300 cycles exceeds 121.3 mA$h$g–1 in the voltage range of 1.0–3.0 V. Furthermore, the electrochemical impedance spectra show that LTO-C2 has higher electronic conductivity and lithium diffusion coefficient, which indicates the advantages in electrode kinetics over LTO and LTO-C1. The results clarify the best electrochemical properties of the carbon-coated LTO-C2 composite prepared by the onepot method. Keywords lithium titanate, carbon-coated, carbon precursor, synthetic process
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Introduction
Spinel-type lithium titanate has been considered a promising lithium-ion battery material due to its excellent structural stability and good cycle life, especially suitable Received June 28, 2020; accepted August 12, 2020 E-mail: [email protected]
for large-scale energy storage [1–3]. Lithium titanate (LTO), which is called “zero strain material”, has zero volume change during the lithium insertion/extraction and shows an excellent cycling property [4,5]. Moreover, LTO has outstanding safety characteristics with a high lithium intercalation potential (1.55 V vs. Li0/Li+) during discharge, which can also avoid the formation of lithium dendrites and solid electrolyte interphase [1,4]. However, the low electronic conductivity ( < 10–13 S$cm–1) and lithium diffusion coefficient of LTO materials severely limits their high rate capability [5]. To improve the electrochemical performance of LTO, one method is to fabricate nano LTO materials with different morphologies [6–9], shorten the diffusion path of lithium in the solid-state, and enhance the intercalation kinetics. The other method is to modify LTO materials using a doping
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