Electrochemistry of Manganese Dioxide in Lithium Nonaqueous Cell: I . X‐Ray Diffractional Study on the Reduction of Electrolytic Manganese Dioxide

Abstract

X‐ray diffractional (XRD) studies were carried out for the electrochemical reduction of heat‐treated electrolytic MnO2 (250° and 400°C for 7 days). A series of XRD examinations indicated that the reaction proceeded without the destruction of the core structure of electrolytic manganese dioxide (EMD). The structural changes during the electrochemical reductions of both EMDs were described, assuming a tetragonal sublattice. Both heat‐treated electrolytic MnO2normals (HEMDs) behaved similarly in the tetragonal sublattice parameter vs. the reduction degree plots. During the first half of the reduction, HEMD phase having a tetragonal sublattice ( a=4.39–4.40Å , c=2.86–2.90Å ) was converted into a new LixMnO2 phase having an expanded tetragonal sublattice ( a=4.9–5.0Å , c=2.82–2.86Å ), i.e., in a two‐phase reaction. In the 30–90% reduction, the a‐axis increased continuously as a function of reduction degree, i.e., in a homogeneous phase reaction. The possible crystal structure of the deep discharge product LixMnO2 false(x>0.8false) is discussed, assuming a tetragonal unit cell ( a=normalca.5Å , c=normalca.2.85Å ) having the normalNiAs‐normaltype structure by analogy with LixRuO2 , and an orthorhombic unit cell, i.e., a=2×normalbÅ , b=normalca.5Å , c=normalca.2.85Å . From these, assuming an orthorhombic unit cell having a=10.2true7_Å , b=4.9true3_Å , and c=2.8true5_Å , all diffraction lines from the reduction products of HEMD were indexed.

Preparation, characterization and electrochemical performance of γ-MnO2 and LiMn2O4 as cathodes for lithium batteries

“…Here in the present work it seems that after the first discharge curve lithium intercalation goes with a single phase. This observation is in agreement with Ohzuku [13] who claims that the lithium intercalation in y-LixMnO2 occurs in a single phase with typical NiAs structure. David et al [14] also proposed an intercalation in a single lithiated phase, but corresponding to an intergrowth between a very distorted Ramsdellite type structure and spinel structure.…”

Materials and fabrication of electrode scaffolds for deposition of MnO2 and their true performance in supercapacitors

“…Known as electrolytic manganese dioxide (EMD), anodically deposited MnO 2 from acidic Mn 2þ solutions have been widely used in the battery industry for a very long time [198,199]. Pang et al first studied the pseudo-capacitive performances of anodic deposited MnO 2 thin film in 2000 [17,200].…”

Electrochemical Lithium Insertion Into a Manganese Dioxide Electrode in Aqueous Solutions

“…Commercial lithium-ion batteries rely on the application of one of the well-known lithium intercalation hosts i.e., LieoO" LiNiO" Li:Vln,O, or y-MIl02 [1][2][3][4]. Recently, novel materials based on transition metal polyanions have also been proposed, and phosphate compounds crystallizing as Nasicon structures appear to hold particular promise (5-6J.…”