Thermochemistry of Li1+xMn2- xO4 (0≤x≤1/3) spinel

Miaojun Wang, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Lithium substituted Li1+xMn2- xO4 spinel samples in the entire solid solution range (0≤x≤1/3) were synthesized by solid-state reaction. The samples with x<0.25 are stoichiometric and those with x≥0.25 are oxygen deficient. High-temperature oxide melt solution calorimetry in molten 3Na 2O·4MoO3 at 974 K was performed to determine their enthalpies of formation from constituent binary oxides at 298 K. The cubic lattice parameter was determined from least-squares fitting of powder XRD data. The variations of the enthalpy of formation from oxides and the lattice parameter with x follow similar trends. The enthalpy of formation from oxides becomes more exothermic with x for stoichiometric compounds (x<0.25) and deviates endothermically from this trend for oxygen-deficient samples (x≥0.25). This energetic trend is related to two competing substitution mechanisms of lithium for manganese (oxidation of Mn3+ to Mn 4+ versus formation of oxygen vacancies). For stoichiometric spinels, the oxidation of Mn3+ to Mn4+ is dominant, whereas for oxygen-deficient compounds both mechanisms are operative. The endothermic deviation is ascribed to the large endothermic enthalpy of reduction.

Original languageEnglish (US)
Pages (from-to)1182-1189
Number of pages8
JournalJournal of Solid State Chemistry
Volume178
Issue number4
DOIs
StatePublished - Apr 2005
Externally publishedYes

Keywords

  • Enthalpy of formation
  • LiMnO
  • Lithium ion batteries
  • Spinel
  • Thermodynamics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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