Enhanced Electrochemical Performance Ru3+ Doped Li2FeP2O7 as Cathode for Lithium Ion Batteries

Li2Fe1-xRuxP2O7 (x = 0, 0.005, 0.01, 0.02, 0.03, and 0.04) were prepared by a simple sol-gel synthesis method. Detailed lattice information, including the observation of a monoclinic P21/c (14) space group and crystal structure, was determined using XRD with rietveld refinement. To further confirm t...

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Bibliographic Details
Published in:International journal of electrochemical science 2018-12, Vol.13 (12), p.12024-12039
Main Authors: Jung, Hee-Won, Lee, Seong-Hun, Ryu, Kwang-Sun
Format: Article
Language:English
Subjects:
Cathode
Lithium ion batteries
Lithium iron pyrophosphate
pillar effect
Ru-doping
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Summary:Li2Fe1-xRuxP2O7 (x = 0, 0.005, 0.01, 0.02, 0.03, and 0.04) were prepared by a simple sol-gel synthesis method. Detailed lattice information, including the observation of a monoclinic P21/c (14) space group and crystal structure, was determined using XRD with rietveld refinement. To further confirm the oxidation and chemical states of elements within the samples, XPS measurements of each element are used. The electrochemical measurements were conducted using EIS, CV, and galvanostatic charge-discharge testing. Li2Fe0.99Ru0.01P2O7 exhibited an increased specific discharge capacity of 100.22mAh/g at 0.05C and decreased polarization during charge and discharge. Li2Fe0.99Ru0.01P2O7 exhibited the best rate-capabilities at various current densities, as well as the best cycle abilities in the voltage range of 2.0-4.5V. Fe K-edge and Ru K-edge in-situ XAS were carried out for samples of Li2FeP2O7 and Li2Fe0.99Ru0.01P2O7 in order to observe changes in the structures of the materials during electrochemical reaction. The results indicate that the structural rearrangement of Li2Fe0.99Ru0.01P2O7 might be reduced by the slight shrinkage of the lattice due to the “pillar effects” of Ru3+. Also, Li2Fe0.99Ru0.01P2O7 demonstrated higher electronic conductivity and ionic diffusion coefficient than Li2FeP2O7. Therefore, the higher electrochemical performance of Li2Fe0.99Ru0.01P2O7 was related with structure stability, electronic conductivity, and ionic diffusion coefficient.
ISSN:1452-3981
1452-3981
DOI:10.20964/2018.12.49