Structural and electrochemical studies of 3 V Li{sub x}MnO{sub 2} cathodes for rechargeable Li batteries
- Bar-Ilan Univ., Ramat-Gan (Israel). Dept. of Chemistry; and others
X-ray diffraction studies (XRD) were carried out for the investigation of the synthesis and electrochemical reduction of lithiated MnO{sub 2}. The optimal Li:Mn ratio for a heat-treated mixture of LiNO{sub 3} + {gamma}-MnO{sub 2} at 370 C (20 h) with a minimum of impurities, such as {gamma}-{beta}-MnO{sub 2} or spinel, was shown to be equal to 0.33. A combined application of the open-circuit voltage (OCV), slow-scan-rate cyclic voltammetry and XRD measurements was used for the investigation of the intercalation mechanism. The initial compound, Li{sub 0.33}MnO, was shown to undergo only one essential reversible transition during its electrochemical reduction to Li{sub 0.75}MnO{sub 2}, with a voltage plateau appearing around 3 V. It was conclusively demonstrated that both a thermal synthesis in a certain range of Li:Mn ratio and electrochemical reduction upon cycling result in the phase transition from Li{sub 0.3}MnO{sub 2} to Li{sub 0.5}MnO{sub 2} spinel. The characteristic feature of the latter reduction process is that it is essentially irreversible and occurs in a thin surface layer of the initial material. The formation of this thin layer seems to be responsible for a drop in the capacity of practical electrodes during their charge-discharge cycling. A plausible explanation for this effect is discussed.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 603724
- Journal Information:
- Journal of the Electrochemical Society, Vol. 144, Issue 12; Other Information: PBD: Dec 1997
- Country of Publication:
- United States
- Language:
- English
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