First principles calculations on lithium diffusion near the surface and in the bulk of Fe-doped LiCoPO4

The olivine phosphate LiCoPO4 is a prospective cathode material in high-voltage lithium-ion batteries. During lithium diffusion, the ions must overcome the diffusion energy barrier near the surface and in the bulk. Experimental studies have shown that Fe doping can enhance the electrochemical perfor...

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Published inPhysical chemistry chemical physics : PCCP Vol. 24; no. 2; pp. 1147 - 1155
Main Authors Kuan-Ching, Wu, Hsieh, Chieh-Ming, Chang, Bor Kae
Format Journal Article
LanguageEnglish
Published Cambridge Royal Society of Chemistry 04.01.2022
Subjects
Cathodes
Diffusion barriers
Doping
Electrochemical analysis
Electrode materials
Electronic properties
Electronic structure
First principles
Ion diffusion
Lithium
Lithium compounds
Lithium-ion batteries
Mathematical analysis
Olivine
Phosphates
Rechargeable batteries
Structural stability
Surface energy
Surface properties
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Summary:The olivine phosphate LiCoPO4 is a prospective cathode material in high-voltage lithium-ion batteries. During lithium diffusion, the ions must overcome the diffusion energy barrier near the surface and in the bulk. Experimental studies have shown that Fe doping can enhance the electrochemical performance of LiCoPO4 with a doping concentration of x = 0.2 (LiFe0.2Co0.8PO4). DFT calculations can provide detailed understanding of the lithium diffusion mechanism, structural stability, and electronic properties for Fe-doped LiCoPO4 and elucidate the origins for this improvement from a microscopic viewpoint. In this study, the electronic structure of Fe-doped LiCoPO4 was calculated via first principles and compared with that of pristine LiCoPO4. To investigate the surface properties of LiCoPO4, surface energies with low indices were calculated. The results showed that the (010) surface has the lowest surface energy. Minimum energy diffusion pathways and energy barriers were calculated using the NEB method. Our calculations showed that the energy barrier for lithium-ion diffusion can be reduced by Fe doping modification. Furthermore, we investigated the diffusion processes of polarons and lithium ions migrating simultaneously. This study has implications for further application of LiCoPO4 as a cathode material.
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ISSN:1463-9076
1463-9084
DOI:10.1039/d1cp04517b