Single-Step Recovery of Divalent Mn Component from LiMn2O4Cathode Material at Hydrothermal Conditions as an Mn-Citrate Complex

Qingxin Zheng, Kensuke Shibazaki, Tetsufumi Ogawa, Masaru Watanabe

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


As one of the most important lithium-ion battery cathode materials for electric vehicles, LiMn2O4 (LMO) cathode material was used as the feedstock of metal recovery in this study. Through a hydrothermal treatment with citric acid (0.3 mol/L), Li and Mn ions were completely leached from a commercial LMO cathode material at 120 °C for 2 min. More importantly, simultaneously with complete leaching of Li and Mn ions from LMO, the Mn component was precipitated and separated as a Mn-citrate complex by adjusting the parameters such as citric acid concentration and holding time. This process avoided the use of high-concentration acids, alkalis, and reductants, and skipped the second separation step, thereby realizing the direct recovery of the Mn component from LMO cathode materials via a green and single-step route. The Mn-citrate complex was identified to be pure C6H8MnO8 or Mn(C6H6O7)H2O, in which Mn existed as in a divalent state. Furthermore, the morphology of the Mn-citrate complex was characterized, and a mechanism was proposed to explain the reactions during this one-step hydrothermal process. Even though the research is just at the initial stage, the Mn-citrate complex reported here is expected to open a new path to the organic acid leaching step of traditional hydrometallurgy and the Mn separation process.

Original languageEnglish
Pages (from-to)10970-10976
Number of pages7
JournalACS Sustainable Chemistry and Engineering
Issue number33
Publication statusPublished - 2021 Aug 23


  • Citric acid
  • Hydrothermal treatment
  • LiMnO
  • Lithium-ion battery
  • Mn recovery
  • Mn-citrate complex

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Renewable Energy, Sustainability and the Environment


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