One-Step Pyro-Synthesis of a Nanostructured Mn3 O4 /C Electrode with Long Cycle Stability for Rechargeable Lithium-Ion Batteries

Flexible Mn3O4/MXene Films with 2D-2D Architectures as Stable and Ultrafast Anodes for Li-Ion Batteries

Mn₃O₄ is regarded as a promising anode material for lithium-ion batteries (LIBs) based on its ultrahigh theoretical capacity (937 mAh g^-1) and low cost but suffers from poor electronic conductivity and large volume variation during the lithiation/delithiation process, which result in dramatic capacity fading and inferior rate capability. Ti₃C₂T_x MXene, a novel two-dimensional transition metal carbide with metallic conductivity, excellent mechanical properties, and hydrophilic surface, could be an ideal candidate to improve the lithium storage performance of Mn₃O₄. Here, a unique flexible, 2D-2D Mn₃O₄/MXene film is fabricated by assembling 2D Mn₃O₄ with Ti₃C₂T_x nanosheets through a simple vacuum filtration approach. In this unique 2D-2D nanostructure, MXene nanosheets buffer the volume change of Mn₃O₄ during the charge/discharge process. Moreover, the introduction of MXene enables the fabricated 2D-2D nanostructure with excellent flexibility and can be directly used as an electrode for LIBs, which is beneficial for enhancing the energy density of the assembled batteries. As a result, the flexible film of Mn₃O₄-MXene-8-2 shows excellent lithium storage performances in terms of specific capacity (931 mAh g^-1 at 0.05 A g^-1), rate capability (624 mAh g^-1 at 1 A g^-1), and cycling stability, demonstrating its great potential for the application in LIBs.

Rational design of 3D net-like carbon based Mn3O4 anode materials with enhanced lithium storage performance

A three-dimensional net-like Mn3O4/carbon paper composite was realized, which delivers a remarkably enhanced rate performance and excellent cycling stability for lithium-ion storage.

Alkoxide hydrolysis in-situ constructing robust trimanganese tetraoxide/graphene composite for high-performance lithium storage

Herein we develop a novel and effective alkoxide hydrolysis approach to in-situ construct the trimanganese tetraoxide (Mn₃O₄)/graphene nanostructured composite as high-performance anode material for lithium-ion batteries (LIBs). This is the first report on the synthesis of Mn₃O₄/graphene composite via a facile hydrolysis of the manganese alkoxide (Mn-alkoxide)/graphene precursor. Before hydrolysis, two dimensional (2D) Mn-alkoxide nanoplates are closely adhered to 2D graphene nanosheets via Mn-O chemical bonding. After hydrolysis, the Mn-alkoxide in-situ converts to Mn₃O₄, while the Mn-O bond is preserved. This leads to a robust Mn₃O₄/graphene hybrid architecture with 15 nm Mn₃O₄ nanocrystals homogeneously anchoring on graphene nanosheets. This not only prevents the Mn₃O₄ nanocrystals agglomeration but also inversely mitigates the graphene nanosheets restacking. Moreover, the flexible and conductive graphene nanosheets can accommodate the volume change. This maintains the structural and electrical integrity of the Mn₃O₄/graphene electrode during the cycling process. As a result, the Mn₃O₄/graphene composite displays superior lithium storage performance with high reversible capacity (741 mAh g^-1 at 100 mA g^-1), excellent rate capability (403 mAh g^-1 at 1000 mA g^-1) and long cycle life (527 mAg g^-1 after 300 cycles at 500 mA g^-1). The electrochemical performance highlights the importance of rational design nanocrystals anchoring on graphene nanosheets for high-performance LIBs application.

Novel Hoberman Sphere Design for Interlaced Mn3O4@CNT Architecture with Atomic Layer Deposition-Coated TiO2 Overlayer as Advanced Anodes in Li-Ion Battery

The Hoberman sphere is a stable and stretchable spatial structure with a unique design concept, which can be taken as the ideal prototype of the internal mechanical/conductive skeleton for the anode with large volume change. Herein, Mn₃O₄ nanoparticles are interlaced with a Hoberman sphere-like interconnected carbon nanotube (CNT) network via a facile self-assembly strategy in which Mn₃O₄ can "locally expand" in the CNT network, limit the volume expansion to the interior space, and maintain a stable outer surface of the hybrid particle. Furthermore, an ultrathin uniform ALD-coated TiO₂ shell is adopted to stabilize the solid electrolyte interphase (SEI), provide high electron conductivity and lithium ion (Li⁺) diffusivity with lithiated Li_xTiO₂, and enhance the reaction kinetics of the Mn₃O₄ by an "electron-density enhancement effect". With this design, the Mn₃O₄@CNT/TiO₂ exhibits a high capacity of 1064 mAh g^-1 at 0.1 A g^-1, a stable cycling stability over 200 cycles, a superior rate capability, and a commercial-level areal capacity of 4.9 mAh cm^-2. In this way, a novel electrode design strategy is achieved by the Hoberman sphere-like CNT design along with the in situ porous formation, which can not only achieve a high-performance anode for LIBs but also can be widely adapted in a variety of advanced electrode materials for alkali metal ion batteries.

Study on the Synthesis of Mn3o4 Nanooctahedrons and Their Performance for Lithium Ion Batteries

Among the transition metal oxides, the Mn₃O₄ nanostructure possesses high theoretical specific capacity and lower operating voltage. However, the low electrical conductivity of Mn₃O₄ decreases its specific capacity and restricts its application in the energy conversion and energy storage. In this work, well-shaped, octahedron-like Mn₃O₄ nanocrystals were prepared by one-step hydrothermal reduction method. Field emission scanning electron microscope, energy dispersive spectrometer, X-ray diffractometer, X-ray photoelectron spectrometer, high resolution transmission electron microscopy, and Fourier transformation infrared spectrometer were applied to characterize the morphology, the structure, and the composition of formed product. The growth mechanism of Mn₃O₄ nano-octahedron was studied. Cyclic voltammograms, galvanostatic charge-discharge, electrochemical impedance spectroscopy, and rate performance were used to study the electrochemical properties of obtained samples. The experimental results indicate that the component of initial reactants can influence the morphology and composition of the formed manganese oxide. At the current density of 1.0 A g^-1, the discharge specific capacity of as-prepared Mn₃O₄ nano-octahedrons maintains at about 450 mAh g^-1 after 300 cycles. This work proves that the formed Mn₃O₄ nano-octahedrons possess an excellent reversibility and display promising electrochemical properties for the preparation of lithium-ion batteries.

Top-down synthesis of sponge-like Mn3O4 at low temperature

A top-down synthetic method was developed for the fabrication of sponge-like Mn₃O₄ composed of Mn₃O₄ nanocrystals by decomposition of manganese formate at 200 °C. The samples were characterized in terms of their structural and morphological properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) studies. TEM and SEM images showed that the morphology of sponge-like Mn₃O₄ structures was mostly retained from the morphology of the manganese formate precursor, which was controlled by the solvothermal process. Large sponge-like Mn₃O₄ structures exhibiting crystallographic symmetry were prepared under solvothermal treatment for a long time. The XRD pattern showed that the Mn₃O₄ exhibit a tetragonal hausmannite structure. The results of N₂ adsorption analysis indicated that the sponge-like Mn₃O₄ nanostructures possess high surface area. The possible formation mechanism of Mn₃O₄ nanostructures has been discussed.

A metal-organic-framework approach to engineer hollow bimetal oxide microspheres towards enhanced electrochemical performances of lithium storage

Nanosized electrode materials with a hollow structure, larger specific surface area, and lower energy density as well as more void space are widely adopted for high-performance lithium-ion batteries. In this work, we obtained bimetal-organic frameworks of Fe/Mn-MOF-74 with a hollow microsphere morphology via a facile one-step microwave method and further used it to fabricate hollow Fe-Mn-O/C microspheres. Endowed with the metal-organic-framework-derived carbon-coated nanoparticle-assembled hollow structure with hierarchical porous characteristics and synergistic effects between two different metal species, the Fe-Mn-O/C electrode exhibits outstanding electrochemical performances as the anode of lithium-ion batteries. It achieves improved cycling performance (1294 mA h g-1 after 200 cycles at 0.1 A g-1) and good rate capability (722, 604, and 521 mA h g-1 at 0.2, 0.5 and 1 A g-1). The smart design of a hollow morphology with uniform two metal species can promote the synthesis of multimetal oxides and their carbon composites, as well as their further potential application for energy-storage.

Pyrosynthesis of Na3 V2 (PO4 )3 @C Cathodes for Safe and Low-Cost Aqueous Hybrid Batteries

Rechargeable hybrid aqueous batteries (ReHABs) have emerged as promising sustainable energy-storage devices because all components are environmentally benign and abundant. In this study, a carbon-wrapped sponge-like Na₃ V₂ (PO₄ )₃ nanoparticle (NVP@C) cathode is prepared by a simple pyrosynthesis for use in the ReHAB system with impressive rate capability and high cyclability. A high-resolution X-ray diffraction study confirmed the formation of pure Na ion superionic conductor (NASICON) NVP with rhombohedral structure. When tested in the ReHAB system, the NVP@C demonstrated high rate capability (66 mAh g^-1 at 32 C) and remarkable cyclability over 1000 cycles (about 72 % of the initial capacity is retained at 30 C). Structural transformation and oxidation change studies of the electrode evaluated by using in situ synchrotron X-ray diffraction and ex situ X-ray photoelectron spectroscopy, respectively, confirmed the high reversibility of the NVP@C electrode in the ReHAB system through a two-phase reaction. The combined strategy of nanosizing and carbon-wrapping in the NVP particles is responsible for the remarkable electrochemical properties. The pyrosynthesis technique appears to be a promising and feasible approach to prepare a high-performance electrode for safe and low-cost ReHAB systems as nextgeneration large-scale energy storage devices.

Novel Bake-in-Salt Method for the Synthesis of Mesoporous Mn3O4@C Networks with Superior Cycling Stability and Rate Performance

The commercial applications of Mn₃O₄ in lithium ion batteries (LIBs) are greatly restricted because of the low electrical conductivity and poor cycling stability at high current density. To overcome these drawbacks, mesoporous Mn₃O₄@C networks were designed and synthesized via an improved bake-in-salt method using NaCl as the assistant salt, and without the protection of inert gas. The added NaCl plays a versatile role during the synthetic process, including the heat conducting medium, removable hard template and protective layer. Because of the homogeneous distribution of Mn₃O₄ nanoparticles within the carbon matrix, the as-prepared Mn₃O₄@C networks show excellent cycling stability in LIBs. After cycling for 950 times at a current density of 1 A g^-1, the discharge capacity of the as-prepared Mn₃O₄@C networks is determined to be 754.4 mA h g^-1, showing superior cycling stability as compared to its counterparts. The valuable and promising method, simple synthetic procedure and excellent cycling stability of the as-prepared Mn₃O₄@C networks makes it a promising candidate as the potential anode material for LIBs.

Electrochemical construction of three-dimensional porous Mn3O4 nanosheet arrays as an anode for the lithium ion battery

The architectures of 3D pores, self-supported structure and nanosheet arrays synergistically improve the electrochemical performance of Mn₃O₄.

A sponge network-shaped Mn3O4/C anode derived from a simple, one-pot metal organic framework-combustion technique for improved lithium ion storage

Sponge shaped Mn₃O₄/C anode derived from simple, one-pot MOF-C technique exhibits excellent cyclability for lithium ion batteries.