Doping effects on structure and electrode performance of K-birnessite-type manganese dioxides for rechargeable lithium battery
TL;DR: In this paper, the performance of the cobalt-doped birnessite was improved by a change in the stacking structure, a decrease in the charge transfer resistance, and improved structural stability of the oxide.
About: This article is published in Electrochimica Acta.The article was published on 2008-02-25. It has received 148 citations till now. The article focuses on the topics: Birnessite & Cobalt.
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TL;DR: The superior supercapacitive performance of the MnO2/CNT nancomposite electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.
Abstract: MnO2/carbon nanotube [CNT] nanocomposites with a CNT core/porous MnO2 sheath hierarchy architecture are synthesized by a simple hydrothermal treatment. X-ray diffraction and Raman spectroscopy analyses reveal that birnessite-type MnO2 is produced through the hydrothermal synthesis. Morphological characterization reveals that three-dimensional hierarchy architecture is built with a highly porous layer consisting of interconnected MnO2 nanoflakes uniformly coated on the CNT surface. The nanocomposite with a composition of 72 wt.% (K0.2MnO2·0.33 H2O)/28 wt.% CNT has a large specific surface area of 237.8 m2/g. Electrochemical properties of the CNT, the pure MnO2, and the MnO2/CNT nanocomposite electrodes are investigated by cyclic voltammetry and electrochemical impedance spectroscopy measurements. The MnO2/CNT nanocomposite electrode exhibits much larger specific capacitance compared with both the CNT electrode and the pure MnO2 electrode and significantly improves rate capability compared to the pure MnO2 electrode. The superior supercapacitive performance of the MnO2/CNT nancomposite electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.
427 citations
TL;DR: In this paper, a catpillar-like nanoflaky MnO2/carbon nanotube (CNT) nanocomposites are synthesized via a facile solution method.
Abstract: Caterpillar-like nanoflaky MnO2/carbon nanotube (CNT) nanocomposites are synthesized via a facile solution method. To build a three-dimensional hierarchy architecture, highly porous interconnected MnO2 nanoflakes are uniformly coated on the surface of the CNTs. As a promising anode material for lithium-ion batteries, the nanoflaky MnO2/CNT nanocomposite electrode exhibits a large reversible capacity of 801 mA h g−1 (∼1000 mA h g−1 can be attributed to the MnO2 porous layer alone) for the first cycle without capacity fade for the first 20 cycles and with a good rate capability. The superior electrochemical performance of the MnO2/CNT nanocomposite electrode compared to the pure MnO2 electrode can be attributed to its unique hierarchy architecture, which is able to provide fast lithium ion and electron transport and to accommodate a large volume change during the conversion reactions.
414 citations
TL;DR: Large energy storage textiles are fabricated by weaving flexible all-solid-state supercapacitor yarns to a 15 cm × 10 cm cloth on a loom and knitting in a woollen wrist band to form a pattern, enabling dual functionalities of energy storage capability and wearability.
Abstract: Wearable electronic textiles that store capacitive energy are a next frontier in personalized electronics. However, the lack of industrially weavable and knittable conductive yarns in conjunction with high capacitance, limits the wide-scale application of such textiles. Here pristine soft conductive yarns are continuously produced by a scalable method with the use of twist-bundle-drawing technique, and are mechanically robust enough to be knitted to a cloth by a commercial cloth knitting machine. Subsequently, the reduced-graphene-oxide-modified conductive yarns covered with a hierarchical structure of MnO2 nanosheets and a polypyrrole thin film were used to fabricate weavable, knittable and wearable yarn supercapacitors. The resultant modified yarns exhibit specific capacitances as high as 36.6 mF cm–1 and 486 mF cm–2 in aqueous electrolyte (three-electrode cell) or 31 mF cm–1 and 411 mF cm–2 in all solid-state two-electrode cell. The symmetric solid-state supercapacitor has high energy densities of 0.00...
397 citations
TL;DR: In this article, a novel hybrid fiber that MnO2 modified graphene sheets on graphene fiber has been fabricated by direct deposition of MnO 2 onto graphene network surrounding graphene fiber (MnO2/G/GF).
202 citations
TL;DR: In this article, ultrathin δ-MnO2 nanosheets were synthesized via in-situ reduction of KMnO4 on graphene oxide using graphene oxide as both reductant and self-sacrificing template.
177 citations
References
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TL;DR: X-ray diffractional studies were carried out for the electrochemical reduction of heat-treated electolytic MnO{sub 2} (250°degree} and 400°degrees}C for 7 days as discussed by the authors.
Abstract: X-ray diffractional (XRD) studies were carried out for the electrochemical reduction of heat-treated electolytic MnO{sub 2} (250{degree} and 400{degrees}C for 7 days) A series of XRD examinations indicated that the reaction proceed 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 electolytic MnO{sub 2}s (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 = 439 {minus} 440 {Angstrom}, c = 286 {minus} 290 {Angstrom}) was converted into a new Li{sub x} MnO{sub 2} phase having an expanded tetragonal sublattice a = 49 {minus} 50 {Angstrom}, c = 282 {minus} 286 {Angstrom}, ie, in a two-phase reaction In the 30-90% reduction, the a-axis increased continuously as a function of reduction degree, ie, in a homogeneous phase reaction The possible crystal structure of the deep discharge product Li{sub x} MnO{sub 2} (x{gt}08) is discussed, assuming a tetragonal unit cell (a = ca 5 {Angstrom}, c = ca 285 {Angstrom}) having the NiAs-type structure by analogy with Li{sub x} RuO{sub 2}, and anmore » orthorhombic unit cell, ie, a = 2 {times} b {Angstrom}, b = ca 5 {Angstrom}, c = ca 285 {Angstrom}« less
692 citations
TL;DR: In this article, the structural features of layered manganese dioxides of the Birnessite family were studied using Raman scattering spectroscopy, which is capable of analysing directly the near-neighbour environment of oxygen coordination around menganese and lithium cations.
633 citations
TL;DR: In this paper, the structure of a synthetic potassium birnessite (KBi) obtained as a finely dispersed powder by thermal decomposition of KMnO4 at 800 °C was studied by single-crystal X-ray diffraction (XRD).
Abstract: The structure of a synthetic potassium birnessite (KBi) obtained as a finely dispersed powder by thermal decomposition of KMnO4 at 800 °C was for the first time studied by single-crystal X-ray diffraction (XRD). It is shown that KBi has a two-layer cell with a = 2.840(1) A and c = 14.03(1) A and space group P63/mmc. In contrast to the structure model proposed by Kim et al. (Chem. Mater. 1999, 11, 557−563), the refined model demonstrates the sole presence of Mn4+ in the octahedral layers, the presence of 0.12 vacant layer sites per octahedron being responsible for the layer charge deficit. In agreement with X-ray absorption spectroscopy result, this layer charge deficit is compensated (1) by the presence of interlayer Mn3+ above or below vacant layer octahedra sharing three Olayer atoms with neighboring Mnlayer octahedra to form a triple-corner surface complex (VITC sites) and (2) by the presence of interlayer K in prismatic cavities located above or below empty tridentate cavities, sharing three edges wit...
173 citations
TL;DR: In this article, a hexagonal form of manganese dioxide was synthesized using mild hydrothermal methods, with a R 3m rhombohedral structure like Lix(H2O)TiS2.
Abstract: We report here the direct synthesis of a hexagonal form of manganese dioxide using mild hydrothermal methods. The reaction of potassium or sodium permanganate in water at 170 °C leads directly to potassium or sodium manganese dioxide, Alk≈0.25MnO2·0.6H2O, with a R3m rhombohedral structure like Lix(H2O)TiS2 and a 7 A repeat distance indicative of a monolayer of water between the manganese dioxide layers. This manganese oxide reacts readily and reversibly with lithium ions.
150 citations