Evolution of crystal structure and electrochemical performance of layered Li1.20Ti0.44Cr0.36O2/C cathode materials with cycling |
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Authors: | Shuai Li Hongbo Liu Yuxi Chen |
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Affiliation: | 1.College of Materials Science and Engineering/Hunan Province Key Laboratory for Spray Deposition Technology and Application,Hunan University,Changsha,China |
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Abstract: | Carbon-coated layered Li1.20Ti0.44Cr0.36O2/C and pristine Li1.20Ti0.44Cr0.36O2 cathode materials have been synthesized through a sol–gel method followed by high-temperature calcination. Their electrochemical performances have been evaluated, which indicate that the Li1.20Ti0.44Cr0.36O2/C exhibits much higher cyclic stability and capacity than the pristine one. The initial delithiation capacity of the Li1.20Ti0.44Cr0.36O2/C can reach 217.1 mAh g?1. The reversible capacity retention is 94 % after 100 cycles at current density of 23 mA g?1. Ex situ X-ray diffraction and electrochemistry impedance spectroscopy coupled with impedance fitting have been employed to reveal evolution of the crystal structure and the electrochemical kinetics of the Li1.20Ti0.44Cr0.36O2/C with delithiation/lithiation cycling. The results indicate that the cation layers of the Li1.20Ti0.44Cr0.36O2/C experience order to disorder transition. The abrupt delithiation capacity fading and potential drop after the initial cycle are resulted from the order to disorder transition accompanying with steep increase of the charge transfer resistance and decrease of the exchange current density and the Li-ion diffusion coefficient simultaneously. |
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