Hierarchically Nanostructured Transition Metal Oxides for Lithium-Ion Batteries

Applications of Metal-Organic-Framework-Derived Carbon Materials

Carbon materials derived from metal-organic frameworks (MOFs) have attracted much attention in the field of scientific research in recent years because of their advantages of excellent electron conductivity, high porosity, and diverse applications. Tremendous efforts are devoted to improving their chemical and physical properties, including optimizing the morphology and structure of the carbon materials, compositing them with other materials, and so on. Here, many kinds of carbon materials derived from metal-organic frameworks are introduced with a particular focus on their promising applications in batteries (lithium-ion batteries, lithium-sulfur batteries, and sodium-ion batteries), supercapacitors (metal oxide/carbon and metal sulfide/carbon), electrocatalytic reactions (oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction), water treatment (MOF-derived carbon and other techniques), and other possible fields. To close, some existing problem and corresponding possible solutions are proposed based on academic knowledge from the reported literature, along with a great deal of experimental experience.

Templated Growth of Crystalline Mesoporous Materials: From Soft/Hard Templates to Colloidal Templates

Mesoporous non-siliceous materials, in particular mesoporous transition metal oxides (m-TMOs), are of interest due to their fascinating electronic, redox, and magnetic properties for a wide range of applications in catalysis and energy storage. Control of the porosity (e.g., pore size, wall thickness, and surface area) and the crystalline degree (e.g., phase composition, crystallinity, and crystal grain size) of m-TMOs are critical for those applications. To crystallize TMOs, high temperature annealing is often needed to remove the amorphous defects and/or tune the compositions of different crystalline phases. This has brought many challenges to surfactant or block copolymer templates used in the process of evaporation-induced-self-assembly to prepare m-TMOs. In this review, we summarize the most recent achievements including the findings in our own laboratory on the use of organosilicate-containing colloids for the templated growth of mesoporous materials. We review a few key examples of preparing crystalline mesoporous oxides using different templating methods. The colloidal templating method by which mesoporous nanostructures can be stabilized up to 1,000°C is highlighted. The applications of m-TMOs and meso metal-oxide hybrids synthesized using organosilicate-containing colloidal templates in photocatalysis and high-temperature catalysis are also discussed.

A multidimensional and hierarchical carbon-confined cobalt phosphide nanocomposite as an advanced anode for lithium and sodium storage

Transition metal phosphides possess remarkable theoretical charge capacities; however, they demonstrate poor intrinsic electrical conductivity and enormous structure changes during cycling. Herein, a novel, multidimensional and hierarchical nanostructure is synthesized which constitutes 0D CoP nanoparticles distrbuted in a 1D dual carbon matrix and further homogenously encapsulated in a 3D graphene (GR) network; this material is denoted as CoP@DC@GR. This synergistic design produces superior advantages for lithium and sodium storage: (i) the ultrasmall and highly dispersed 0D CoP nanoparticles embedded in the 1D dual carbon matrix can decrease the electron/ion transport paths; (ii) the 3D interconnected architecture constructed from 2D GR and the 1D dual carbon matrix guarantees a robust structure to withstand the mechanical stress of the 1D dual carbon matrix, which can relieve volume inflation of the 0D CoP nanoparticles; (iii) the 1D dual carbon matrix and 3D GR frame structure offer continuous electron/ion transport routes, thus promoting rapid reaction kinetics. Due to this multiscale coordinated design, the CoP@DC@GR nanocomposite demonstrates high charge capacity, remarkable cycle stability, and distinguished rate performance; therefore, it possesses fascinating potential in anodes for lithium and sodium storage.

A ternary Ag–TiO2/reduced graphene oxide nanocomposite as the anode material for lithium ion batteries

A Ag–TiO₂/rGO nanocomposite exhibits enhanced electrochemical performance with good stability, as the intra-/inter-grain connectivity is increased between nanosized Ag and TiO₂ particles on the reduced graphene oxide surface.

Hierarchical nanostructures derived from cellulose for lithium-ion batteries

Recent advances in natural cellulose substance derived hierarchical nanomaterials applied as anodic materials for lithium-ion batteries are summarized.

3D plum candy-like NiCoMnO4@graphene as anodes for high-performance lithium-ion batteries

3D plum candy-like NiCoMnO4 microspheres have been prepared via ultrasonic spraying and subsequently wrapped by graphene through electrostatic self-assembly. The as-prepared NiCoMnO4 powders show hollow structures and NiCoMnO4@graphene exhibits excellent electrochemical performances in terms of rate performance and cycling stability, achieving a high reversible capacity of 844.6 mA h g-1 at a current density of 2000 mA g-1. After 50 cycles at 1000 mA g-1, NiCoMnO4@graphene delivers a reversible capacity of 1045.1 mA h g-1 while the pristine NiCoMnO4 only has a capacity of 143.4 mA h g-1. The hierarchical porous structure helps to facilitate electron transfer and Li-ion kinetic diffusion by shortening the Li-ion diffusion length, accommodating the mechanical stress and volume change during the Li-ion insertion/extraction processes. Analysis from the electrochemical performances reveals that the enhanced performances could be also attributed to the reduced charge-transfer resistance and enhanced Li-ion diffusion kinetics because of the graphene-coating. Moreover, Schottky electric field, due to the difference in work function between graphene and NiCoMnO4, might be favorable for the redox activity of the NiCoMnO4. In light of the excellent electrochemical performance and simple preparation, we believe that 3D plum candy-like NiCoMnO4@graphene composites are expected to be applied as a promising anode materials for high-performance lithium ion batteries.

3D Porous Tin Created by Tuning the Redox Potential Acts as an Advanced Electrode for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have attracted significant research interest for large-scale electric energy storage. However, anodes with good rate capability and long cycle life are still lacking. Here, a three-dimensional (3D) porous Sn on Cu foil (Sn/Cu) is prepared by tuning the redox potential of Cu⁺ /Cu with a ligand of thiourea to trigger the replacement reaction between Cu and Sn²⁺ . The as-synthesized Sn/Cu is used as an integrated porous electrode and can be directly applied as an advanced freestanding electrode for SIBs. Such a unique structure can efficiently relieve the strain caused by sodiation/desodiation and benefit penetration of the electrolyte and diffusion of Na⁺ . This is a merit of its large reversible capacity of about 700 mAh g^-1 at 2500 mA g^-1 for 400 cycles. A full battery of Sn/Cu//Na₃ (VO_0.5 )₂ (PO₄ )₃ F₂ is constructed, which presents a high energy density of 311.7 Wh kg^-1 and long lifespan of 200 cycles. This facile synthesis strategy and good electrochemical performance will encourage more investigations into structure design of functional materials.

Operando investigations of lithiation and delithiation processes in a BiVO4 anode material

Conversion and alloying reactions in BiVO₄ as an anode material for lithium-ion batteries.

Recent Progress on Two-Dimensional Nanoflake Ensembles for Energy Storage Applications

The rational design and synthesis of two-dimensional (2D) nanoflake ensemble-based materials have garnered great attention owing to the properties of the components of these materials, such as high mechanical flexibility, high specific surface area, numerous active sites, chemical stability, and superior electrical and thermal conductivity. These properties render the 2D ensembles great choices as alternative electrode materials for electrochemical energy storage systems. More recently, recognition of the numerous advantages of these 2D ensemble structures has led to the realization that the performance of certain devices could be significantly enhanced by utilizing three-dimensional (3D) architectures that can furnish an increased number of active sites. The present review summarizes the recent progress in 2D ensemble-based materials for energy storage applications, including supercapacitors, lithium-ion batteries, and sodium-ion batteries. Further, perspectives relating to the challenges and opportunities in this promising research area are discussed.