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Materials Research Bulletin, 1991
Electrochemically active lithium-manganese-oxide phases have been synthesized by chemical leachin... more Electrochemically active lithium-manganese-oxide phases have been synthesized by chemical leaching of LizO from the rock salt phase LizMnO 3 (LizO.MnOz) with acid at 25°C. Preliminary electrochemical tests have shown that capacities of approximately 200 mAh/g based on the mass of the lithium-manganese oxide electrode can be obtained in room-temperature lithium cells, and that capacities in excess of 140 mAh/g can be achieved on cycling. Although a detailed structure analysis of an extensively delithiated sample has not yet been undertaken, it is believed that it may be a novel layered lithium-manganese oxide compound Li2_xMnO3_xa (0<x<2) with a cubic-close-packed oxygen anion array in which some of the Li + ions are ionexchanged with H + ions. Heat-treatment of an extensively delithiated LizMnO 3 sample at 300°C in air transforms the product to a ¥/13-MnO 2 type phase, whereas delithiated samples that still contain an appreciable amount of lithium transform on heating to a two-phase product of Li2MnO 3 and a compound with a spinel-related structure.
Materials Research Bulletin, 1992
A highly crystalline ct-MnO 2 phase has been synthesised by acid treatment of LizMnO 3. A neutron... more A highly crystalline ct-MnO 2 phase has been synthesised by acid treatment of LizMnO 3. A neutron-diffraction study has shown that the stoichiometry of this phase is Ao.36Mn0.9102 (or MnO2o0.2A20) where A refers predominantly to H + ions and a very minor concentration of Li + ions. Heat-treatment at 300°C leaves a virtually anhydrous a-MnO 2 product. The absence of any foreign cation such as K ÷, Na ÷ or Rb ÷ within the channels of the structure has raised the possibility of utilizing the a-MnO z framework as a high performance electrode for secondary lithium cells. Preliminary electrochemical data indicate that capacities in excess of 200 mAh/g are achievable from these a-MnO z electrodes in room-temperature lithium cells. Cyclic voltammograms show that lithium is inserted into a-MnO 2 in a two-step process and that this process Js reversible.
Journal of Solid State Chemistry, 2004
De Wolff disorder, microtwinning, and point defects which are characteristic for g-MnO 2 have bee... more De Wolff disorder, microtwinning, and point defects which are characteristic for g-MnO 2 have been studied using molecular modeling. Particular attention was paid to the effects these defects have on the X-ray diffraction (XRD) pattern. Comparisons with observed XRD patterns allow identification of structural features in chemical (CMD) and electrochemical (EMD) manganese dioxide. The major factor determining the structure of g-MnO 2 is de Wolff disorder. CMD materials are characterized by a larger percentage of pyrolusite while EMD materials contain more ramsdellite. Microtwinning occurs to a larger extent in EMD than in CMD materials. EMD materials are also higher in energy.
Journal of Materials Chemistry, 1992
Journal of Solid State Chemistry, 1994
Journal of Solid State Chemistry, 1993
ABSTRACT
Journal of Solid State Chemistry, Jun 1, 1993
ABSTRACT
Materials Research Bulletin, 1991
Electrochemically active lithium-manganese-oxide phases have been synthesized by chemical leachin... more Electrochemically active lithium-manganese-oxide phases have been synthesized by chemical leaching of LizO from the rock salt phase LizMnO 3 (LizO.MnOz) with acid at 25°C. Preliminary electrochemical tests have shown that capacities of approximately 200 mAh/g based on the mass of the lithium-manganese oxide electrode can be obtained in room-temperature lithium cells, and that capacities in excess of 140 mAh/g can be achieved on cycling. Although a detailed structure analysis of an extensively delithiated sample has not yet been undertaken, it is believed that it may be a novel layered lithium-manganese oxide compound Li2_xMnO3_xa (0<x<2) with a cubic-close-packed oxygen anion array in which some of the Li + ions are ionexchanged with H + ions. Heat-treatment of an extensively delithiated LizMnO 3 sample at 300°C in air transforms the product to a ¥/13-MnO 2 type phase, whereas delithiated samples that still contain an appreciable amount of lithium transform on heating to a two-phase product of Li2MnO 3 and a compound with a spinel-related structure.
Materials Research Bulletin, 1992
A highly crystalline ct-MnO 2 phase has been synthesised by acid treatment of LizMnO 3. A neutron... more A highly crystalline ct-MnO 2 phase has been synthesised by acid treatment of LizMnO 3. A neutron-diffraction study has shown that the stoichiometry of this phase is Ao.36Mn0.9102 (or MnO2o0.2A20) where A refers predominantly to H + ions and a very minor concentration of Li + ions. Heat-treatment at 300°C leaves a virtually anhydrous a-MnO 2 product. The absence of any foreign cation such as K ÷, Na ÷ or Rb ÷ within the channels of the structure has raised the possibility of utilizing the a-MnO z framework as a high performance electrode for secondary lithium cells. Preliminary electrochemical data indicate that capacities in excess of 200 mAh/g are achievable from these a-MnO z electrodes in room-temperature lithium cells. Cyclic voltammograms show that lithium is inserted into a-MnO 2 in a two-step process and that this process Js reversible.
Journal of Solid State Chemistry, 2004
De Wolff disorder, microtwinning, and point defects which are characteristic for g-MnO 2 have bee... more De Wolff disorder, microtwinning, and point defects which are characteristic for g-MnO 2 have been studied using molecular modeling. Particular attention was paid to the effects these defects have on the X-ray diffraction (XRD) pattern. Comparisons with observed XRD patterns allow identification of structural features in chemical (CMD) and electrochemical (EMD) manganese dioxide. The major factor determining the structure of g-MnO 2 is de Wolff disorder. CMD materials are characterized by a larger percentage of pyrolusite while EMD materials contain more ramsdellite. Microtwinning occurs to a larger extent in EMD than in CMD materials. EMD materials are also higher in energy.
Journal of Materials Chemistry, 1992
Journal of Solid State Chemistry, 1994
Journal of Solid State Chemistry, 1993
ABSTRACT
Journal of Solid State Chemistry, Jun 1, 1993
ABSTRACT