The Structure of Fully H-Inserted γ-Manganese Dioxide Compounds

MacLean, Lachlan A. H.; Tye, F. L.

doi:10.1006/jssc.1996.0163

Cited by 26 publications

(19 citation statements)

References 9 publications

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“…For the deformation of the structure to occur primarily in the ac plane (i.e. the plane orthogonal to the 2 × 1 tunnels of ramsdellite) is consistent with what has been reported both for proton 10,21,40,41 and lithium ion insertion. 23 Comparison of our R-MnO 2 data set with published diffraction patterns for R-MnO 2 chemically reduced in lithium-ion containing organic media 23 suggests that the structural evolution of the material is similar under the two sets of reduction conditions (Fig.…”

Section: Samplesupporting

confidence: 89%

Electrochemical Behavior of Electrolytic Manganese Dioxide in Aqueous KOH and LiOH Solutions: A Comparative Study

Rus

Moon

Bai

et al. 2015

J. Electrochem. Soc.

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As an inexpensive and high capacity oxidant, electrolytic manganese dioxide (γ-MnO 2 ) is of interest as a cathode for secondary aqueous batteries. Electrochemical behavior of γ-MnO 2 was characterized in aqueous 5.0 M KOH and LiOH solutions, and found to depend strongly upon cation identity. In LiOH and mixed LiOH / KOH solutions, Li-ion intercalation appeared to operate in competition with proton intercalation, being favored at higher [Li + ] and, for mixed electrolytes, lower sweep rates. Electrochemical and in situ X-ray diffraction data indicated that γ-MnO 2 underwent a chemically irreversible transformation upon the first reduction in LiOH solution, while in KOH solution, structure was largely unchanged after the first cycle. These experiments with γ-MnO 2 as well as with a closely-related, ramsdellite-like sample, suggest that depending on sample morphology/rate capability, the irreversible process proceeds either through a solid-solution reaction or a two-phase reaction followed by a solid-solution reaction. While discharge capacity and capacity retention during galvanostatic cycling of γ-MnO 2 were worse in LiOH than in KOH solution, some improvement was noted in a mixed LiOH/KOH solution. Electrolytic manganese dioxide (EMD or ε/γ-MnO 2 ) is the material most commonly employed as the cathode in primary alkaline batteries and primary non-aqueous lithium cells owing to its relatively low cost, low toxicity, high reduction potential, and high gravimetric capacity. Unfortunately, MnO 2 -based secondary cells tend to have limited cycle life, due to the conversion of active material into electrochemically inactive or electronically resistive phases, such as hausmannite (Mn 3 O 4 ) or hetaerolyte (ZnMn 2 O 4 ) in aqueous cells, 1,2 and to pulverization associated with large changes in volume with state of charge.3 Under certain conditions, however, γ-MnO 2 can be cycled with relatively good capacity retention. Major criteria for reversible cycling are to limit the depth of discharge to minimize the solubility of manganese in lower oxidation states, and to avoid the formation of soluble high oxidation state species during charging (i.e. MnO 4 2− ). 4,5,6,7 It has also been reported that the use of LiOH instead of KOH as the electrolyte can improve the cycle life of γ-MnO 2 . 8 The structure of γ-MnO 2 is highly defective both in terms of type and concentration of defects. According to the De Wolff model, the structure is thought to be an intergrowth of ramsdellite and pyrolusite layers (Fig. 1).9,10 Both phases have tunnel-structures, as is apparent from the viewpoint in Fig. 1. γ-MnO 2 also contains microtwinning defects, which introduce kinks to the tunnel structure.10 Manganese vacancies can also be present and necessitate the incorporation of protons (Ruetschi protons) in the structure to maintain charge balance. 12In aqueous KOH or NH 4 Cl media (in the case of a Leclanché cell), the reduction of the Mn 4+ to Mn 3+ is accompanied by the incorporation of protons into the tunnels in the structure (along th...

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Section: Samplesupporting

confidence: 89%

Electrochemical Behavior of Electrolytic Manganese Dioxide in Aqueous KOH and LiOH Solutions: A Comparative Study

Rus

Moon

Bai

et al. 2015

J. Electrochem. Soc.

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show abstract

“…The solid state reduction of oxide under the e!ect of alcohol is generally accompanied by the insertion of cations (30), and will be studied further in a forthcoming paper (31). All these reaction paths are summarized in Fig.…”

Section: Fig 2 Reaction Steps and Intermediate Phases Observable Dumentioning

confidence: 98%

Preparation of Metallic Powders and Alloys in Polyol Media: A Thermodynamic Approach

Larcher

Patrice

2000

Journal of Solid State Chemistry

133

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“…However, this has proved challenging because of the complex and preparation-dependent microstructure it accommodates. In particular, the X-ray diffraction (XRD) patterns are typified by broad peaks indicating a high degree of disorder [10,1] and are influenced by the production process [11]. Accordingly, g-MnO 2 is subdivided into three groups: natural (NMD), chemical (CMD) and electrochemical (EMD).…”

Section: Introductionmentioning

confidence: 99%