Mechanism of electrochemical activity in Li2MnO3

Alastair D. Robertson, Peter G. Bruce*

*Corresponding author for this work

Research output: Contribution to journalArticle

333 Citations (Scopus)

Abstract

Lithium intercalation compounds based on lithium manganese oxides are of great importance as positive electrodes for rechargeable lithium batteries. It is widely accepted that Li+ may be extracted (deintercalated) from such lithium manganese oxides accompanied by oxidation of Mn up to a maximum oxidation state of +4. However, it has been suggested recently that further Li+ removal may be possible. Among the mechanisms that have been proposed to charge balance the removal of Li+ are Mn oxidation beyond +4 or loss of O2-. To investigate this phenomenon we have selected Li2MnO3, a layered compound Li[Li1/3Mn2/3]O2 with a ready supply of mobile Li+ ions but with all Mn already in the +4 oxidation state. We show that a substantial quantity of Li (at least 1.39 Li) may be removed. At 55 °C this occurs exclusively by oxidation of the nonaqueous electrolyte, thus generating H+ which exchange one-for-one with Li+ to form Li2-xHxMnO3. The presence of H+ between the oxide layers results in a change of the layer stacking from O3 to P3, the latter being more stable for O-H-O bonding. At 30 °C initial Li removal is accompanied by oxygen loss (effective removal of Li2O) but further Li+ removal involves the same proton exchange mechanism as observed at 55 °C. The reaction is partially reversible. On extended cycling the material converts to spinel.

Original languageEnglish
Pages (from-to)1984-1992
Number of pages9
JournalChemistry of Materials
Volume15
Issue number10
DOIs
Publication statusPublished - 1 May 2003
Externally publishedYes

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Oxidation
Lithium
Manganese oxide
Lithium Compounds
Ion exchange
Intercalation compounds
Lithium batteries
Oxides
Electrolytes
Protons
Ions
Oxygen
Electrodes
lithium manganese oxide

Cite this

Robertson, Alastair D. ; Bruce, Peter G. / Mechanism of electrochemical activity in Li2MnO3. In: Chemistry of Materials. 2003 ; Vol. 15, No. 10. pp. 1984-1992.
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abstract = "Lithium intercalation compounds based on lithium manganese oxides are of great importance as positive electrodes for rechargeable lithium batteries. It is widely accepted that Li+ may be extracted (deintercalated) from such lithium manganese oxides accompanied by oxidation of Mn up to a maximum oxidation state of +4. However, it has been suggested recently that further Li+ removal may be possible. Among the mechanisms that have been proposed to charge balance the removal of Li+ are Mn oxidation beyond +4 or loss of O2-. To investigate this phenomenon we have selected Li2MnO3, a layered compound Li[Li1/3Mn2/3]O2 with a ready supply of mobile Li+ ions but with all Mn already in the +4 oxidation state. We show that a substantial quantity of Li (at least 1.39 Li) may be removed. At 55 °C this occurs exclusively by oxidation of the nonaqueous electrolyte, thus generating H+ which exchange one-for-one with Li+ to form Li2-xHxMnO3. The presence of H+ between the oxide layers results in a change of the layer stacking from O3 to P3, the latter being more stable for O-H-O bonding. At 30 °C initial Li removal is accompanied by oxygen loss (effective removal of Li2O) but further Li+ removal involves the same proton exchange mechanism as observed at 55 °C. The reaction is partially reversible. On extended cycling the material converts to spinel.",
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Mechanism of electrochemical activity in Li2MnO3. / Robertson, Alastair D.; Bruce, Peter G.

In: Chemistry of Materials, Vol. 15, No. 10, 01.05.2003, p. 1984-1992.

Research output: Contribution to journalArticle

TY - JOUR

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AU - Bruce, Peter G.

PY - 2003/5/1

Y1 - 2003/5/1

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AB - Lithium intercalation compounds based on lithium manganese oxides are of great importance as positive electrodes for rechargeable lithium batteries. It is widely accepted that Li+ may be extracted (deintercalated) from such lithium manganese oxides accompanied by oxidation of Mn up to a maximum oxidation state of +4. However, it has been suggested recently that further Li+ removal may be possible. Among the mechanisms that have been proposed to charge balance the removal of Li+ are Mn oxidation beyond +4 or loss of O2-. To investigate this phenomenon we have selected Li2MnO3, a layered compound Li[Li1/3Mn2/3]O2 with a ready supply of mobile Li+ ions but with all Mn already in the +4 oxidation state. We show that a substantial quantity of Li (at least 1.39 Li) may be removed. At 55 °C this occurs exclusively by oxidation of the nonaqueous electrolyte, thus generating H+ which exchange one-for-one with Li+ to form Li2-xHxMnO3. The presence of H+ between the oxide layers results in a change of the layer stacking from O3 to P3, the latter being more stable for O-H-O bonding. At 30 °C initial Li removal is accompanied by oxygen loss (effective removal of Li2O) but further Li+ removal involves the same proton exchange mechanism as observed at 55 °C. The reaction is partially reversible. On extended cycling the material converts to spinel.

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