Electrochemical potentials of layered oxide and olivine phosphate with aluminum substitution: A first principles study

Arun Kumar Varanasi, Phani Kanth Sanagavarapu, Arghya Bhowmik, Mridula Dixit Bharadwaj, B. Narayana, Umesh V. Waghmare, Dipti Deodhare, Alind Sharma

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

First-principles prediction of enhancement in the electrochemical potential of LiCoO2 with aluminum substitution has been realized through earlier experiments. For safer and less expensive Li-ion batteries, it is desirable to have a similar enhancement for alternative cathode materials, LiFePO4 and LiCoPO4. Here, we present first-principles density functional theory based analysis of the effects of aluminum substitution on electrochemical potential of LiCoO2, LiFePO4 and LiCoPO4. While Al substitution for transition metal results in increase in electrochemical potential of LiCoO2, it leads to reduction in LiFePO4 and LiCoPO4. Through comparative topological analysis of charge density of these materials, we identify a ratio of Bader charges that correlates with electrochemical potential and determine the chemical origin of these contrasting effects: while electronic charge from lithium is transferred largely to oxygen in LiCoO2, it gets shared by the oxygen and Co/Fe in olivine phosphates due to strong covalency between O and Co/Fe. Our work shows that covalency of transition metal–oxygen bond plays a key role in determining battery potential.
Original languageEnglish
JournalBulletin of Materials Science
Volume36
Issue number7
Pages (from-to)1331–1337
ISSN0250-4707
Publication statusPublished - 2014
Externally publishedYes

Keywords

  • Lithium ion battery
  • Cathodes
  • Density functional theory
  • Density of states
  • Bader charge analysis
  • Electrochemical potential

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