Sandwich-like Mn3O4/carbon nanofragment composites with a higher capacity than commercial graphite and hierarchical voltage plateaus for 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.

Self-induced matrix with Li-ion storage activity in ultrathin CuMnO2 nanosheets electrode

Conversion anode materials such as Mn₃O₄ draw much attention due to their considerable theoretical capacity for lithium-ion batteries (LIBs). However, poor conductivity, slow solid-state Li-ion diffusion, and huge volume expansion of the active materials during charge/discharge lead to unsatisfied electrochemical performance. Despite several strategies like nanocrystallization, fabricating hierarchical nanostructures, and introducing a matrix are valid to address these crucial issues, the achieved electrochemical performance still needs to be further enhanced. What is worse, the matrix with less or no Li-ion storage activity may lower the achieved capacity of the electrodes. Herein, ultra-thin CuMnO₂ nanosheets with the thickness of 5-8 nm were evaluated for LIBs. The ultra-thin sheet-like nanostructure offers sufficient contact areas with electrolyte and shortens the Li-ion diffusion distance. Moreover, the in-situ generated Mn and Cu along with their oxides could play the role of matrix and conductive agent in turn at different stages, relieving the stress brought by volume expansion. Therefore, the as-prepared ultra-thin CuMnO₂ nanosheets electrode displays a remarkable reversible capacity, long cycling stability, and outstanding rate capability (a reversible capacity of 1160.5 mAh g^-1 at 0.1A g^-1 was retained after 100 cycles with a capacity retention of 95.1 %, and 717.8 mAh g^-1 at 2.0 A g^-1 after 400 cycles).

Preparation of a multifunctional P-CF@Mn3O4 composite as a structural anode material

The novel CF@Mn3O4 composite prepared in three steps displays considerable electrochemical characteristics and potential in the flexible vehicle.

Directly Electrospun Carbon Nanofibers Incorporated with Mn3O4 Nanoparticles as Bending-Resistant Cathode for Flexible Al-Air Batteries

Al-air batteries are regarded as potential power source for flexible and wearable devices. However, the traditional cathodes of Al-air batteries are easy to be broken after continuous bending. This is why few Al-air batteries have been tested under the state of dynamic bending so far. Herein, carbon nanofibers incorporated with Mn₃O₄ catalyst have been prepared as bending-resistant cathodes through direct electrospinning. The cathode assembled in Al-air battery showed excellent electrochemical and mechanical stability. A high specific capacity of 1021 mAh/cm² was achieved after bending 1000 times, which is 81.7% of that in platform state. This work will facilitate the progress of using Al-air battery in flexible electronics.

In Situ Synthesis of Mn3 O4 Nanoparticles on Hollow Carbon Nanofiber as High-Performance Lithium-Ion Battery Anode

The practical applications of Mn₃ O₄ in lithium-ion batteries are greatly hindered by fast capacity decay and poor rate performance as a result of significant volume changes and low electrical conductivity. It is believed that the synthesis of nanoscale Mn₃ O₄ combined with carbonaceous matrix will lead to a better electrochemical performance. Herein, a convenient route for the synthesis of Mn₃ O₄ nanoparticles grown in situ on hollow carbon nanofiber (denoted as HCF/Mn₃ O₄ ) is reported. The small size of Mn₃ O₄ particles combined with HCF can significantly alleviate volume changes and electrical conductivity; the strong chemical interactions between HCF and Mn₃ O₄ would improve the reversibility of the conversion reaction for MnO into Mn₃ O₄ and accelerate charge transfer. These features endow the HCF/Mn₃ O₄ composite with superior cycling stability and rate performance if used as the anode for lithium-ion batteries. The composite delivers a high discharge capacity of 835 mA h g^-1 after 100 cycles at 200 mA g^-1 , and 652 mA h g^-1 after 240 cycles at 1000 mA g^-1 . Even at 2000 mA g^-1 , it still shows a high capacity of 528 mA h g^-1 . The facile synthetic method and outstanding electrochemical performance of the as-prepared HCF/Mn₃ O₄ composite make it a promising candidate for a potential anode material for lithium-ion batteries.

Green and Rational Design of 3D Layer-by-Layer MnO x Hierarchically Mesoporous Microcuboids from MOF Templates for High-Rate and Long-Life Li-Ion Batteries

Rational design and delicate control on the textural properties of metal-oxide materials for diverse structure-dependent applications still remain formidable challenges. Here, we present an eco-friendly and facile approach to smartly fabricate three-dimensional (3D) layer-by-layer manganese oxide (MnO _x) hierarchical mesoporous microcuboids from a Mn-MOF-74-based template, using a one-step solution-phase reaction scheme at room temperature. Through the controlled exchange of metal-organic framework (MOF) ligand with OH^- in alkaline aqueous solution and in situ oxidation of manganese hydroxide intermediate, the Mn-MOF-74 template/precursor was readily converted to Mn₃O₄ or δ-MnO₂ counterpart consisting of primary nanoparticle and nanosheet building blocks, respectively, with well-retained morphology. By X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy, high-resolution TEM, N₂ adsorption-desorption analysis and other techniques, their crystal structure, detailed morphology, and microstructure features were unambiguously revealed. Specifically, their electrochemical Li-ion insertion/extraction properties were well evaluated, and it turns out that these unique 3D microcuboids could achieve a sustained superior lithium-storage performance especially at high rates benefited from the well-orchestrated structural characteristics (Mn₃O₄ microcuboids: 890.7, 767.4, 560.1, and 437.1 mAh g^-1 after 400 cycles at 0.2, 0.5, 1, and 2 A g^-1, respectively; δ-MnO₂ microcuboids: 991.5, 660.8, 504.4, and 362.1 mAh g^-1 after 400 cycles at 0.2, 0.5, 1, and 2 A g^-1, respectively). To our knowledge, this is the most durable high-rate capability as well as the highest reversible capacity ever reported for pure MnO _x anodes, which even surpass most of their hybrids. This facile, green, and economical strategy renews the traditional MOF-derived synthesis for highly tailorable functional materials and opens up new opportunities for metal-oxide electrodes with high performance.

Design and synthesis of graphene/SnO2/polyacrylamide nanocomposites as anode material for lithium-ion batteries

Tin dioxide (SnO2) is a promising anode material for lithium-ion batteries owing to its large theoretical capacity (1494 mA h g-1). However, its practical application is hindered by these problems: the low conductivity, which restricts rate performance of the electrode, and the drastic volume change (400%). In this study, we designed a novel polyacrylamide/SnO2 nanocrystals/graphene gel (PAAm@SnO2NC@GG) structure, in which SnO2 nanocrystals anchored in three-dimensional graphene gel network and the polyacrylamide layers could effectively prevent the agglomeration of SnO2 nanocrystals, presenting excellent cyclability and rate performance. A capacity retention of over 90% after 300 cycles of 376 mA h g-1 was achieved at a current density of 5 A g-1. In addition, a stable capacity of about 989 mA h g-1 at lower current density of 0.2 A g-1 was achieved.

Functional Hybrid Materials Based on Manganese Dioxide and Lignin Activated by Ionic Liquids and Their Application in the Production of Lithium Ion Batteries

Kraft lignin (KL) was activated using selected ionic liquids (ILs). The activated form of the biopolymer, due to the presence of carbonyl groups, can be used in electrochemical tests. To increase the application potential of the system in electrochemistry, activated lignin forms were combined with manganese dioxide, and the most important physicochemical and morphological-microstructural properties of the novel, functional hybrid systems were determined using Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), scanning electron microscopy (SEM), zeta potential analysis, thermal stability (TGA/DTG) and porous structure analysis. An investigation was also made of the practical application of the hybrid materials in the production of lithium ion batteries. The capacity of the anode (MnO₂/activated lignin), working at a low current regime of 50 mA·g-1, was ca. 610 mAh·g-1, while a current of 1000 mA·g-1 resulted in a capacity of 570 mAh·g-1. Superior cyclic stability and rate capability indicate that this may be a promising electrode material for use in high-performance lithium ion batteries.