Complex spinel-structure oxides based on Li<sub>2</sub>MM'<sub>3</sub>O<sub>8</sub> and LiMM'O<sub>4</sub> have been systematically investigated on the basis of solid state chemistry and thermodynamics, and are found to constitute a novel family of cathode materials for 5 V lithium batteries. We have targeted lithium cathode materials that operate over 5 V, linked to large capacity and good cycling stability. The spinels prepared by solid state synthesis have been characterised using powder X-ray and neutron diffraction, impedance measurements, thermal analyses, magnetic measurements, XANES spectroscopy, Mossbauer spectroscopy and electrochemical measurements. In a single lithium cell, Li<sub>2</sub>CoMn<sub>3</sub>O<sub>8</sub> and LiCoMnO<sub>4</sub> are shown to be the first cathode materials to operate at discharge voltages over 5 V; Li<sub>2</sub>FeMn<sub>3</sub>O<sub>8</sub> operates at a discharge plateau commencing at 5 V and centred on 4.9 V, offering potentially great economic and environmental advantages as a lithium cathode. LiCoMnO<sub>4</sub> exhibits a discharge capacity of <I>ca</I>. 95 mAhg<sup>-1</sup> at a long plateau centred on 5.0 V in a cell, Li/LiPF<sub>6</sub>, propylene carbonate / LiCoMnO<sub>4</sub>, and therefore has superior energy density to LiMn<sub>2</sub>O<sub>4</sub>, the cathode material used in state-of-the-art cells. This renders LiCoMnO<sub>4</sub> potentially very attractive as a cathode material in practical 5 V lithium battery systems.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:287603 |
| Date | January 1999 |
| Creators | Kawai, Hiroo |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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