Chemical Vapor Deposition-Assisted Fabrication of Self-Assembled Co/MnO@C Composite Nanofibers as Advanced Anode Materials for High-Capacity Li-Ion Batteries

Constructing the nanostructure of transition metal oxides for high energy density lithium-ion batteries has been widely studied recently. Prompted by the idea that the transition metal can serve as a catalyzer influence on the reversibility of solid-electrolyte interphase films, Co/MnO@C composite nanofibers were designed by electrospinning and chemical vapor deposition methods. The Co/MnO@C electrode showed superior electrochemical performance with a large capacity increase for the first 400 cycles and a high rate performance of 1345 mA h g^-1 at 1000 mA g^-1. There was no obvious decay of capacity over the whole 1000 cycles, demonstrating the excellent cycling stability of the samples. The new design and synthesis of the anodic materials may offer a prototype for high-performance and strong-stability batteries.

Interfacial Superassembly of Grape-Like MnO-Ni@C Frameworks for Superior Lithium Storage

Despite the excellent electrochemical performance of MnO-based electrodes, a large capacity increase cannot be avoided during long-life cycling, which makes it difficult to seek out appropriate cathode materials to match for commercial applications. In this work, a grape-like MnO-Ni@C framework from interfacial superassembly with remarkable electrochemical properties was fabricated as anode materials for lithium-ion batteries. Electrochemical analysis indicates that the introduction of Ni not only contributes to the excellent rate capability and high specific capacity but also prevents further oxidation of MnO to the higher valence states for ultrastable long-life cycling performance. Furthermore, thermodynamic calculation proves that the ultrastable long cycling life of the Ni-Mn-O system originated from a buffer composition region to stabilize the MnO structure. Because of the unique grape-like structure and performance of the Ni-Mn-O system, the MnO-Ni@C electrode displayed an invertible specific capacity of 706 mA h g^-1 after 200 cycles at a current density of 0.1 A g^-1 and excellent cycling stability maintained a capacity of 476.8 mA h g^-1 after 2100 cycles at 1.0 A g^-1 without obvious capacity change. This new nanocomposite material could offer a novel fabrication strategy and insight for MnO-based materials and other metal oxides as anodes for improved electrochemical performance.

Improved electrochemical performance of 2D accordion-like MnV2O6 nanosheets as anode materials for Li-ion batteries

MnV₂O₆ is a promising anode material for lithium ion batteries with high theoretical specific capacity, abundant reserves and inexpensive constituent elements.

3D Hierarchical Microballs Constructed by Intertwined MnO@N-doped Carbon Nanofibers towards Superior Lithium-Storage Properties

MnO is a promising high-capacity anode material for lithium-ion batteries (LIBs), but pristine material suffers short cycle life and poor rate capability, thus hindering the practical application. In this work, a new type of porous MnO microballs stringed with N-doped porous carbon (3DHB-MnO@NC) with a well-connected hierarchical three-dimensional network structure was prepared by the facile self-template method. The 3DHB-MnO@NC electrode can effectively promote the ion/electron transfer and buffer the large volume change of electrode during the electrochemical reaction. As the anode for LIBs, the 3DHB-MnO@NC possesses outstanding cycling performance (1247.7 mA h g^-1 after 90 cycles at 200 mA g^-1 ) and good rate capabilities (949.6 mA h g^-1 after 450 cycles at 1000 mA g^-1 ). The facile self-template method of the prepared 3DHB-MnO@NC composite paves a new way for practical applications of MnO in high performance LIBs.

Uniform MnCo2O4 Porous Dumbbells for Lithium-Ion Batteries and Oxygen Evolution Reactions

Three-dimensional (3D) binary oxides with hierarchical porous nanostructures are attracting increasing attentions as electrode materials in energy storage and conversion systems because of their structural superiority which not only create desired electronic and ion transport channels but also possess better structural mechanical stability. Herein, unusual 3D hierarchical MnCo₂O₄ porous dumbbells have been synthesized by a facile solvothermal method combined with a following heat treatment in air. The as-obtained MnCo₂O₄ dumbbells are composed of tightly stacked nanorods and show a large specific surface area of 41.30 m² g^-1 with a pore size distribution of 2-10 nm. As an anode material for lithium-ion batteries (LIBs), the MnCo₂O₄ dumbbell electrode exhibits high reversible capacity and good rate capability, where a stable reversible capacity of 955 mA h g^-1 can be maintained after 180 cycles at 200 mA g^-1. Even at a high current density of 2000 mA g^-1, the electrode can still deliver a specific capacity of 423.3 mA h g^-1, demonstrating superior electrochemical properties for LIBs. In addition, the obtained 3D hierarchical MnCo₂O₄ porous dumbbells also display good oxygen evolution reaction activity with an overpotential of 426 mV at a current density of 10 mA cm^-2 and a Tafel slope of 93 mV dec^-1.

High Lithium Storage Capacity and Long Cycling Life Fe3S4 Anodes with Reversible Solid Electrolyte Interface Films and Sandwiched Reduced Graphene Oxide Shells

Increasing demands for lithium-ion batteries (LIBs) with high energy density and high power density require highly reversible electrochemical reactions to enhance the cyclability and capacities of electrodes. As the reversible formation/decomposition of the solid electrolyte interface (SEI) film during the lithiation/delithiation process of Fe₃S₄ could bring about a higher capacity than its theoretical value, in the present work, synthesized Fe₃S₄ nanoparticles are sandwich-wrapped with reduced graphene oxide (RGO) to fabricate highly reversible and long cycling life anode materials for high-performance LIBs. The micron-sized long slit between sandwiched RGO sheets effectively prevents the aggregation of intermediate phases during the discharge/charge process and thus increases cycling capacity because of the reversible formation/decomposition of the SEI film driven by Fe nanoparticles. Furthermore, the RGO sheets interconnect with each other by a face-to-face mode to construct a more efficiently conductive network, and the maximum interfacial oxygen bridge bonds benefit the fast electron hopping from RGO to Fe₃S₄, improving the depth of the electrochemical reactions and facilitating the highly reversible lithiation/delithiation of Fe₃S₄. Thus, the resultant Fe₃S₄/RGO hybrid shows a highly reversible charge capacity of 1324 mA h g^-1 over 275 cycles at a current density of 100 mA g^-1, even retains 480 mA h g^-1 over 500 cycles at 1000 mA g^-1, which are much higher than reported values.

Porous and Low-Crystalline Manganese Silicate Hollow Spheres Wired by Graphene Oxide for High-Performance Lithium and Sodium Storage

Herein, a graphene oxide (GO)-wired manganese silicate (MS) hollow sphere (MS/GO) composite is successfully synthesized. Such an architecture possesses multiple advantages in lithium and sodium storage. The hollow MS structure provides a sufficient free space for volume variation accommodation; the porous and low-crystalline features facilitate the diffusion of lithium ions; meanwhile, the flexible GO sheets enhance the electronic conductivity of the composite to a certain degree. When applied as the anode material for lithium-ion batteries (LIBs), the as-obtained MS/GO composite exhibits a high reversible capacity, ultrastable cyclability, and good rate performance. Particularly, the MS/GO composite delivers a high capacity of 699 mA h g^-1 even after 1000 cycles at 1 A g^-1. The sodium-storage performance of MS/GO has been studied for the first time, and it delivers a stable capacity of 268 mA h g^-1 after 300 cycles at 0.2 A g^-1. This study suggests that the rational design of metal silicates would render them promising anode materials for LIBs and SIBs.

Engineering the Li Storage Properties of Graphene Anodes: Defect Evolution and Pore Structure Regulation

A general and mild strategy for fabricating defect-enriched graphene mesh (GM) and its application toward the anode of Li-ion batteries (LIBs) has been reported. The GM with a pore size of 60-200 nm is achieved by employing Fe₂O₃ as the etching reagent that is capable of locally etching the graphene basal plane in a relatively mild manner. Upon different drying technologies, that is, oven drying and freeze-drying, GMs with different porous structure are obtained. The electrochemical Li storage properties of GMs in comparison with graphene aerogels (GAs) disclose that both defect sites and porous structure are crucial for the final anodic performances. We show that only when merged with rich porosity, the GM anode can achieve a better Li storage performance than that of GA. Moreover, we further fabricated nitrogen-doped GM (NGM) using urea as the nitrogen source with a freeze-drying process. Benefiting from the unique structural characteristics, that is, plentiful defects, abundant pores, and nitrogen doping, the NGM anode exhibits high Li storage capacity with good cyclic stability (1078 mAh g^-1 even after 350 continuous cycles at a current density of 0.2 C) and outstanding rate capability. Our finding provides fundamental insights into the influence of defects and pore structure on the Li storage properties of graphene, which might be helpful for designing advanced graphene-based anodes for LIBs.

A new strategy for developing superior electrode materials for advanced batteries: using a positive cycling trend to compensate the negative one to achieve ultralong cycling stability

In this communication, in order to develop superior electrode materials for advanced energy storage devices, a new strategy is proposed and then verified by the (Si@MnO)@C/RGO anode material for lithium ion batteries. The core idea of this strategy is the use of a positive cycling trend (gradually increasing Li-storage capacities of the MnO-based constituent during cycling) to compensate the negative one (gradually decreasing capacities of the Si anode) to achieve ultralong cycling stability. As demonstrated in both half and full cells, the as-prepared (Si@MnO)@C/RGO nanocomposite exhibits superior Li-storage properties in terms of ultralong cycling stability (no obvious increase or decrease of capacity when cycled at 3 A g^-1 after 1500 cycles) and excellent high-rate capabilities (delivering a capacity of ca. 540 mA h g^-1 at a high current density of 8 A g^-1) as well as a good full-cell performance. In addition, the structure of the electrodes is stable after 200 cycles. Such a strategy provides a new idea to develop superior electrode materials for next-generation energy storage devices with ultralong cycling stabilities.