Low Barriers and Faster Electron/Ion Transport Rates through the Ga2O3/MnCO3 Anode with a Heterojunction Structure for Lithium-Ion Batteries

Electrode stability can be controlled to a large extent by constructing suitable composite structures, in which the heterojunction structure can affect the transport of electrons and ions through the effect of the interface state, changed band gap width, and the electric field at the interface. As a promising electrode material, the Ga-based material has a conversion between solid and liquid phases in the electrochemical reaction process, which endows it with self-healing properties with the structure and morphology. Based on these, the Ga2O3/MnCO3 composite was successfully synthesized with a heterogeneous structure by introducing a Ga source in the hydrothermal process. Benefitting from the acceleration effect of the internal electric field and the narrower band gap at the interface, a high-capacity Ga2O3/MnCO3 composite electrode (1112 mAh·g-1 after 225 cycles at 0.1 A·g-1 and 457.1 mAh·g-1 after 400 cycles at 1 A·g-1) can be achieved for lithium-ion batteries. The results can provide a reference for the research and preparation of electrode materials with high performance.

The effects of calcination on the electrochemical properties of manganese oxides

Three different crystalline forms of Mn3O4 were successfully prepared by a liquid phase method with different additives. Using XRD, SEM, EDS, BET, compacted density and electrochemical analysis, the effects of different additives on the morphology, phase composition, surface characteristics, specific surface area, electrochemical and other physical and chemical properties of manganese oxides were investigated. The results showed that the rod type Mn3O4 was prepared by mixing ammonia water and anhydrous ethanol in a 1 : 1 ratio and an appropriate amount of cetylmethyl ammonium bromide as the additive. The rod-type Mn3O4 showed a maximum specific surface area of 63.87 m2 g-1 and has the advantages of low compaction density, no introduction of other impurities, and high adsorption potential. It also has excellent electrochemical performance and an impedance of 240 Ω. The specific capacity was as high as 666.5 mA h g-1 at 1C current density and 382.2 mA h g-1 after 200 cycles. The results also showed that the electrochemical performance of Mn2O3 prepared at 700 °C from the rod-type Mn3O4 was the best. When it was used as the anode material of a lithium-ion battery, it showed a high specific capacity of 712.1 mA h g-1 after 200 cycles. Therefore, the rod-type Mn2O3 material has the characteristics of high capacity, low cost and environmental friendliness and is a promising candidate anode material for lithium-ion batteries.

Nanostructured conversion-type anode materials of metal-organic framework-derived spinel XMn2O4 (X = Zn, Co, Cu, Ni) to boost lithium storage

Bimetallic spinel transition metal oxides play a major part in actualizing eco-friendly electrochemical energy storage systems (ESSs). However, structural precariousness and low electrochemical capacitance restrict their actual implementation in lithium-ion batteries (LIBs). To address these demerits, the sacrificial template approach has been considered as a prospective way to strengthen electrochemical stability and rate performance. Herein, metal-organic frameworks (MOFs) derived XMn₂O₄-BDC (H₂BDC = 1,4-dicarboxybenzene, X = Zn, Co, Cu, Ni) are prepared by a hydrothermal approach in order to discover the effects of various metal cations on the electrochemical performance. Among them, ZnMn₂O₄-BDC displays best electrochemical properties (1321.5 mAh g^-1 at the current density of 0.1 A g^-1 after 300 cycles) and high efficiency with accelerated Li⁺ diffusivity. Density functional theory (DFT) calculations confirm the ZnMn₂O₄ possesses the weakest adsorption energy on Li⁺ with a minimized value of -0.92 eV. In comparison with other XMn₂O₄ through traditional fabrication method, MOF-derived XMn₂O₄-BDC possesses a higher number of Li⁺ transport channels and better electric conductivity. This tactic provides a feasible and effective method for preparing bimetallic transition metal oxides and enhances energy storage applications.

Self-assembled hydrogel nanocube for stimuli responsive drug delivery and tumor ablation by phototherapy against breast cancer

The shape and responsiveness of nanoengineered delivery carriers are crucial characteristics for the rapid and efficient delivery of therapeutics. We report on a novel type of micrometer-sized hydrogel particles of controlled shape with dual pH and redox sensitivity for intracellular delivery of anticancer drugs and phototherapy. The cubical HA-DOP-CS-PEG networks with disulfide links are obtained by cross-linking HA-DOP-CS-PEG with cystamine. The pH-triggered hydrogel swelling/shrinkage was not only affords effective doxorubicin release. It also actively provides the endosomal/lysosomal escape, redox-triggered drug release. The hydrogels degrade rapidly to low molecular weight chains in the presence of the typical intracellular concentration of glutathione. Drug-loaded cube particles found to be 12% more cytotoxic. ICG and DOX-loaded hydrogel cubes demonstrate 90% cytotoxicity when incubated with MCF-7 cancer cells for 24 and 48 h, respectively. This approach integrates the advantages of pH sensitivity, enzymatic degradation, and shape-regulated internalization for novel types of "intelligent" three-dimensional networks with programmable behavior for controlled delivery of therapeutics.

Short-term effects of Mn2O3 nanoparticles on physiological activities and gene expression of nitrifying bacteria under low and high dissolved oxygen conditions

The short-term effects of Mn₂O₃ nanoparticles (NPs) were examined for nitrifying bacterial enrichments exposed under low and high dissolved oxygen (DO) conditions using substrate (ammonia) specific oxygen uptake rates (sOUR), reverse transcriptase - quantitative polymerase chain reaction (RT-qPCR) assays, and by analysis of 16S rRNA sequences. Samples from nitrifying bioreactor were exposed in batch vessels to Mn₂O₃ NPs (1, 5 and 10 mg/L) for either 1 or 3 h under no additional aeration or 0.25 L/min aeration. There was increase in nitrification inhibition as determined by sOUR with increasing dosages of Mn₂O₃ NPs for both low and high DO. At 10 mg/L Mn₂O₃ NPs, the inhibition was about 7-10% for 1 and 3 h exposure in both cases. There was notable reduction in the transcript levels of amoA, hao and nirK for 10 mg/L of Mn₂O₃ NPs under 3 h, high DO exposure, which corresponded well with sOUR. The 16S rRNA sequencing showed that there was an inhibitory effect on ammonia oxidizers activity upon exposure to 10 mg/L of Mn₂O₃ NPs. Collectively, the findings in this study advanced understanding of the different effects of Mn₂O₃ NPs on nitrifying bacteria.

Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid over Holey 2 D Mn2 O3 Nanoflakes from a Mn-based MOF

The aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a promising renewable monomer to produce bio-based polymers such as polyethylene furanoate (PEF), has recently emerged as the subject of increasing interest. Here, holey 2 D Mn₂ O₃ nanoflakes were obtained by a facile thermal treatment of a Mn-based metal-organic framework (MOF) precursor. The structural and morphological properties of the nanoflakes were characterized by powder XRD, FTIR, SEM and TEM to explore the formation process. It was inferred that the linker loss in the MOF precursor and the oxidation of the Mn cation induced by the heat-treatment in air were responsible for the formation of holey 2 D Mn₂ O₃ nanoflakes. The specific morphology and redox cycle of the Mn cation on the surface endowed the synthesized nanoflakes with promising performance on the selective oxidation. The obtained nanoflakes calcined at 400 °C (M400) afforded over 99.5 % yield of FDCA at complete conversion of HMF, which is superior to the catalytic activity of commercial Mn₂ O₃ and activated MnO₂ . To our knowledge, Mn₂ O₃ exhibiting such a high performance on the aerobic oxidation of HMF to FDCA has not yet been reported. Based on the investigation of the experimental parameters, a plausible reaction mechanism was proposed.

High capacity rock salt type Li2MnO3-δ thin film battery electrodes

Recent investigations of layered, rock salt and spinel-type manganese oxides in composite powder electrodes revealed the mutual stabilization of the Li–Mn–O compounds during electrochemical cycling. A novel approach of depositing such complex compounds as an active cathode material in thin-film battery electrodes is demonstrated in this work. It shows the maximum capacity of 226 mA h g⁻¹ which is superior in comparison to that of commercial LiMn₂O₄ powder as well as thin films. Reactive ion beam sputtering is used to deposit films of a Li₂MnO_3−δ composition. The method allows for tailoring of the active layer's crystal structure by controlling the oxygen partial pressure during deposition. Electron diffractometry reveals the presence of layered monoclinic and defect rock salt structures, the former transforms during cycling and results in thin films with extraordinary electrochemical properties. X-ray photoelectron spectroscopy shows that a large amount of disorder on the cation sub-lattices has been incorporated in the structure, which is beneficial for lithium migration and cycle stability.

The work demonstrates a novel route to synthesize disorder rich rock salt-type Li₂MnO_3−δ electrodes flaunting remarkably high capacity due to dynamic phase transformation during cycling.

Structural Diversity of Zinc(II), Manganese(II), and Gadolinium(III) Coordination Polymers Based on Two Isomeric N-Heteroaromatic Polycarboxylate Ligands: Structures and Their Derived Mn2O3 for Lithium Storage Applications

Tuning the coordination sites of two isomeric semirigid ligands, 5-(4-pyridin-3-yl-benzoylamino)isophthalic acid (3-H₂PBI) and 5-(4-pyridin-4-yl-benzoylamino)isophthalic acid (4-H₂PBI), afforded six new coordination polymers (CPs), [Zn(3-PBI)(H₂O)]_n (1), {[Mn₂(3-PBI)₂(H₂O)]·DMF·2H₂O}_n (2), {[Gd₂(3-PBI)₃(H₂O)₃]·DMF·3H₂O}_n (3), {[Zn₂(4-PBI)₂]·H₂O}_n (4), {[Mn₂(4-PBI)₂(H₂O)₂]·4H₂O}_n (5), and {(Me₂NH₂)[Gd(4-PBI)₂]·H₂O}_n (6). Structural analysis shows that 1 consists of 2D honeycomb (6,3) net, three sets of networks interlace mutually, generating an unexpected 2D + 2D + 2D → 3D polycatenating interesting system. 2 exhibits a 3D pcu topology. 3 presents a unique 3D with 3,3,6T13 network topology. 4 possesses 3D 2-fold interpenetrated structure with rutile topology. 5 presents an alluring 2D architecture comprising two distinct topologies (kgd and hcb), stacked arrangement in an unexpected ABBABB mode. 6 displays 2D (4,4)-grid network. A differentiation of these structural features indicate that coordination connectivity of metals, together with binding modes of two ligands are accountable for the fascinating structural contrast. In addition, 2 and 5 were then transformed into Mn₂O₃ via a simple heat treatment. Electrochemical test results show that both of the obtained Mn₂O₃ moieties exhibit stable lithium storage properties and excellent rate capabilities.

A Rapid Synthesis of Mesoporous Mn2O3 Nanoparticles for Supercapacitor Applications

Mn2O3 nanomaterials have been recently composing a variety of electrochemical systems like fuel cells, supercapacitors, etc., due to their high specific capacitance, low cost, abundance and environmentally benign nature. In this work, mesoporous Mn2O3 nanoparticles (NPs) were synthesized by manganese acetate, citric acid and sodium hydroxide through a hydrothermal process at 150 °C for 3 h. The synthesized mesoporous Mn2O3 NPs were thoroughly characterized in terms of their morphology, surfaces, as well as their crystalline, electrochemical and electrochemical properties. For supercapacitor applications, the synthesized mesoporous Mn2O3 NP-based electrode accomplished an excellent specific capacitance (Csp) of 460 F·g−1 at 10 mV·s−1 with a good electrocatalytic activity by observing good electrochemical properties in a 6 M KOH electrolyte. The excellent Csp might be explained by the improvement of the surface area, porous surface and uniformity, which might favor the generation of large active sites and a fast ionic transport over the good electrocatalytic surface of the Mn2O3 electrode. The fabricated supercapacitors exhibited a good cycling stability after 5000 cycles by maintaining ~83% of Csp.

Hierarchical structured Mn2O3 nanomaterials with excellent electrochemical properties for lithium ion batteries

A series of Mn2O3 nanomaterials with hierarchical porous structures was synthesized using three types of leaves as templates. In addition to their different morphologies, different porous nanostructures were achieved by choosing different leaves. The Mn2O3 nanomaterial prepared by using gingko leaves as a template provides a larger pore volume and a higher Brunauer-Emmett-Teller (BET) surface area. At the same time, this material also displays excellent electrochemical performance, that is, the specific capacities are 1274.6 mA h g-1 after 300 cycles and 381.5 mA h g-1 at current densities of 300 and 3000 mA g-1, respectively.

Conversion-type Anode Materials for Alkali-Ion Batteries: State of the Art and Possible Research Directions

In this study, the potential of conversion-type anode materials for alkali-ion batteries has been examined and analyzed in terms of the parameters of prime importance for practical alkali-ion systems. Issues like voltage hysteresis, discharge profile, rate stabilities, cyclic stabilities, irreversible capacity loss, and Columbic efficiencies have been specifically addressed and analyzed as the key subjects. Relevant studies on achieving a better performance by addressing one or more of the issues have been carefully selected and outlook has been presented on the basis of this literature. Mechanistic insights into the subject of conversion reactions are discussed in light of the use of recent and advanced techniques like in situ transmission electron microscopy, in operando X-ray diffraction, and X-ray absorption spectroscopy. Three-dimensional plots depicting the performance of different materials, morphologies, and compositions with respect to these parameters are also presented to highlight the systematic of multiparameter dependencies. Inferences are drawn from these plots in the form of a short section at the end, which should be helpful to the readers, especially young researchers. We believe that this study differs from others on the subject in being focused toward addressing the practical limitations and providing possible research directions to achieve the best possible results from conversion-type anode materials.

Hydrolysis-resistant yttrium alkoxide rhombic dodecahedra prepared by a facile hydrothermal method

The amount of NaOH and the volume ratio of ethylene glycol/water are key factors, which dominate the formation of yttrium alkoxide rhombic dodecahedra and yttrium hydroxide prisms.

Formation of Mn–Cr mixed oxide nanosheets with enhanced lithium storage properties

Novel carbon-free Mn₂O₃/MnCr₂O₄ hybrid nanosheets are synthesized. As an anode for lithium-ion batteries, they deliver a wonderful electrochemical performance.

Dual-porosity Mn2O3 cubes for highly efficient dye adsorption

Dual-porosity materials containing both macropores and mesopores are highly desired in many fields. In this work, we prepared dual-porosity Mn₂O₃ cube materials with large-pore mesopores, in which, macropores are made by using carbon spheres as the hard templates, while the mesopores are produced via a template-free route. The attained dual-porosity Mn₂O₃ materials have 24nm of large-pore mesopores and 700nm of macropores. Besides, the achieved materials own cubic morphologies with particle sizes as large as 6.0μm, making them separable in the solution by a facile natural sedimentation. Dye adsorption measurements reveal that the dual-porosity materials possess a very high maximum adsorption capacity of 125.6mg/g, much larger than many reported materials. Particularly, the adsorbents can be recycled and the dye removal efficiency can be well maintained at 98% after four cycles. Adsorption isotherm and kinetics show that the Langmuir model and the pseudo-second-order kinetics model can well describe the adsorption process of Congo Red on the dual-porosity Mn₂O₃ cube materials. In brief, the reported dual-porosity Mn₂O₃ demonstrates a good example for controlled preparation of dual-porosity materials with large-pore mesopores, and the macropore-mesopore dual-porosity distribution is good for mass transfer in dye adsorption application.

Formation of porous nitrogen-doped carbon-coating MnO nanospheres for advanced reversible lithium storage

Herein, we have developed a facile and effective approach for synthesizing a novel kind of porous nitrogen-doped carbon-coated MnO nanosphere. The porous Mn₂O₃ nanospheres are initially obtained by the calcination treatment of a coordination self-assembled aggregation precursor (referred to as Mn(OAc)₂-C-8). Then, MnO@N-doped carbon composites (MnO@NCs) are obtained by the calcination of the Mn₂O₃ nanospheres coated with polydopamine (Mn₂O₃@PDA). The MnO@NCs are evaluated as an anode for lithium ion batteries (LIBs), which exhibit high specific capacity, stable cycling performance (1096.6 mA h g^-1 after 100 cycles at 100 mA g^-1) and high coulombic efficiency (about 99% over 100 cycles). The unique structure design and synergistic effect not only settle the challenges of low conductivity and poor cycling stability of transition metal oxides but also resolve the imperfection of inferior specific capacity of traditional graphite materials. Importantly, it may provide a commendable conception for developing new-fashioned anode materials to improve the lithium storage capability and electrochemical performance.

Good lithium storage performance of Fe2SiO4 as an anode material for secondary lithium ion batteries

The electrochemical properties of Fe₂SiO₄ particles were systematically investigated and our results proved that fayalite presents great specific capacity, superior rate capability and long battery cycle life when tested in the form of a half-cell.

Synthesis of porous Mn2O3 embedded in reduced graphene oxide as advanced anode materials for lithium storage

The porous Mn₂O₃ nanospheres embedded in reduced graphene oxide delivered superior lithium storage ability including high reversible specific capacity, cycling stability and rate performances as an anode material in lithium-ion batteries.

Conversion Reaction-Based Oxide Nanomaterials for Lithium Ion Battery Anodes

Developing high-energy-density electrodes for lithium ion batteries (LIBs) is of primary importance to meet the challenges in electronics and automobile industries in the near future. Conversion reaction-based transition metal oxides are attractive candidates for LIB anodes because of their high theoretical capacities. This review summarizes recent advances on the development of nanostructured transition metal oxides for use in lithium ion battery anodes based on conversion reactions. The oxide materials covered in this review include oxides of iron, manganese, cobalt, copper, nickel, molybdenum, zinc, ruthenium, chromium, and tungsten, and mixed metal oxides. Various kinds of nanostructured materials including nanowires, nanosheets, hollow structures, porous structures, and oxide/carbon nanocomposites are discussed in terms of their LIB anode applications.

Reconstruction of Mini-Hollow Polyhedron Mn2O3 Derived from MOFs as a High-Performance Lithium Anode Material

A mini-hollow polyhedron Mn2O3is used as the anode material for lithium-ion batteries. Benefiting from the small interior cavity and intrinsic nanosize effect, a stable reconstructed hierarchical nanostructure is formed. It has excellent energy storage properties, exhibiting a capacity of 760 mAh g-1 at 2 A g-1 after 1000 cycles. This finding offers a new perspective for the design of electrodes with large energy storage.

Porous Mn2O3 microcubes with exposed {001} facets as electrode for lithium ion batteries

Porous Mn₂O₃ microcubes with exposed {001} facets have been obtained and the Li-ion batteries in which they are applied deliver a high reversible capacity.

Facile synthesis of MOF-derived Mn2O3 hollow microspheres as anode materials for lithium-ion batteries

In this article, we report a facile and scalable route for the fabrication of Mn₂O₃ hollow microspheres by direct pyrolysis of Mn-based metal–organic frameworks at 450 °C with a heating rate of 10 °C min⁻¹ in air.

A simple synthesis of hollow Mn2O3 core–shell microspheres and their application in lithium ion batteries

Hollow Mn₂O₃ core–shell microspheres were successfully fabricated via a mixed method including a solution method and a subsequent thermal decomposition.

Facile fabrication of highly porous Co3O4 nanobelts as anode materials for lithium-ion batteries

Highly porous Co₃O₄ nanobelts were successfully synthesized by using a hydrothermal technique, followed by calcination of the Co(OH)₂ precursor.

Graphene-coated mesoporous Co3O4 fibers as an efficient anode material for Li-ion batteries

The graphene-coating porous cobalt oxide fibers (Co₃O₄@G) were synthesized using coordination polymers as precursors through calcination and subsequent self-assembly process. The obtained materials exhibit good electrochemical performances.

Electrochemical energy storage in Mn2O3 porous nanobars derived from morphology-conserved transformation of benzenetricarboxylate-bridged metal–organic framework

MOF-derived Mn₂O₃ shows a high capacity of ∼410 mA h g⁻¹ as a 2 V anode and an ultrahigh energy density of 147.4 W h kg⁻¹ as a supercapacitor.

Three-Dimensional (3D) Bicontinuous Hierarchically Porous Mn2O3 Single Crystals for High Performance Lithium-Ion Batteries

Bicontinuous hierarchically porous Mn₂O₃ single crystals (BHP-Mn₂O₃-SCs) with uniform parallelepiped geometry and tunable sizes have been synthesized and used as anode materials for lithium-ion batteries (LIBs). The monodispersed BHP-Mn₂O₃-SCs exhibit high specific surface area and three dimensional interconnected bimodal mesoporosity throughout the entire crystal. Such hierarchical interpenetrating porous framework can not only provide a large number of active sites for Li ion insertion, but also good conductivity and short diffusion length for Li ions, leading to a high lithium storage capacity and enhanced rate capability. Furthermore, owing to their specific porosity, these BHP-Mn₂O₃-SCs as anode materials can accommodate the volume expansion/contraction that occurs with lithium insertion/extraction during discharge/charge processes, resulting in their good cycling performance. Our synthesized BHP-Mn₂O₃-SCs with a size of ~700 nm display the best electrochemical performance, with a large reversible capacity (845 mA h g⁻¹ at 100 mA g⁻¹ after 50 cycles), high coulombic efficiency (>95%), excellent cycling stability and superior rate capability (410 mA h g⁻¹ at 1 Ag⁻¹). These values are among the highest reported for Mn₂O₃-based bulk solids and nanostructures. Also, electrochemical impedance spectroscopy study demonstrates that the BHP-Mn₂O₃-SCs are suitable for charge transfer at the electrode/electrolyte interface.

MOF-derived ultrafine MnO nanocrystals embedded in a porous carbon matrix as high-performance anodes for lithium-ion batteries

Although MnO has been demonstrated to be a promising anode material for lithium-ion batteries (LIBs) in terms of its high theoretical capacity (755 mA h g(-1)), comparatively low voltage hysteresis (<0.8 V), low cost, and environmental benignity, the application of MnO as a practical electrode material is still hindered by many obstacles, including poor cycling stability and huge volume expansion during the charge/discharge process. Herein, we report a facile and scalable metal-organic framework-derived route for the in situ fabrication of ultrafine MnO nanocrystals encapsulated in a porous carbon matrix, where nanopores increase active sites to store redox ions and enhance ionic diffusivity to encapsulated MnO nanocrystals. As an anode material for lithium-ion batteries (LIBs), these MnO@C composites exhibited a high reversible specific capacity of 1221 mA h g(-1) after 100 cycles at a current density of 100 mA g(-1). The excellent electrochemical performance can be attributed to their unique structure with MnO nanocrystals dispersed uniformly inside a porous carbon matrix, which can largely enhance the electrical conductivity and effectively avoid the aggregation of MnO nanocrystals, and relieve the strain caused by the volumetric change during the charge/discharge process. This facile and economical strategy will extend the scope of metal-organic framework-derived synthesis for other materials in energy storage applications.

Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mn (x) (+) oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure-property relationships. The oxidation process related to the different MnO x species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnO x species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnO x species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species.