Self‐Sacrificial Template‐Directed Synthesis of Metal–Organic Framework‐Derived Porous Carbon for Energy‐Storage Devices

Metal–organic framework (MOF)‐derived carbon materials exhibit large surface areas, but dominant micropore characteristics and uncontrollable dimensions. Herein, we propose a self‐sacrificial template‐directed synthesis method to engineer the porous structure and dimensions of MOF‐derived carbon materials. A porous zinc oxide (ZnO) nanosheet solid is selected as the self‐sacrificial template and two‐dimensional (2D) nanostructure‐directing agent to prepare 2D ZIF‐8‐derived carbon nanosheets (ZCNs). The as‐prepared ZCN materials exhibit a large surface area with hierarchical porosity. These intriguing features render ZCN materials advanced electrode materials for electrochemical energy‐storage devices, demonstrating large ion‐accessible surface area and high ion‐/electron‐transport rates. This self‐sacrificial template‐directed synthesis method offers new avenues for rational engineering of the porous structure and dimensions of MOF‐derived porous carbon materials, thus exploiting their full potential for electrochemical energy‐storage devices.On the surface: A self‐sacrificial template‐directed synthesis method is proposed to engineer the porosity and dimensions of MOF‐derived carbon materials. By using a porous nanosheet solid as the self‐sacrificial template and two‐dimensional (2D) nanostructure‐directing agent, 2D ZIF‐8‐derived carbon nanosheets are prepared, which exhibit a large ion‐accessible surface area and rapid ion transport as the electrode materials for electrochemical energy‐storage devices.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137193/1/celc201500536-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137193/2/celc201500536.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137193/3/celc201500536_am.pd

Self-templated formation of uniform NiCo2O4 hollow spheres with complex interior structures for lithium-ion batteries and supercapacitors

Despite the significant advancement in preparing metal oxide hollow structures, most approaches rely on template-based multistep procedures for tailoring the interior structure. In this work, we develop a new generally applicable strategy toward the synthesis of mixed-metal-oxide complex hollow spheres. Starting with metal glycerate solid spheres, we show that subsequent thermal annealing in air leads to the formation of complex hollow spheres of the resulting metal oxide. We demonstrate the concept by synthesizing highly uniform NiCo2O4 hollow spheres with a complex interior structure. With the small primary building nanoparticles, high structural integrity, complex interior architectures, and enlarged surface area, these unique NiCo2O4 hollow spheres exhibit superior electrochemical performances as advanced electrode materials for both lithium-ion batteries and supercapacitors. This approach can be an efficient self-templated strategy for the preparation of mixed-metal-oxide hollow spheres with complex interior structures and functionalities

General formation of MS (M = Ni, Cu, Mn) box-in-box hollow structures with enhanced pseudocapacitive properties

Complex hollow structures of metal sulfides could be promising materials for energy storage devices such as supercapacitors and lithium-ion batteries. However, it is still a great challenge to fabricate well-defined metal sulfides hollow structures with multi-shells, hierarchical architectures, and non-spherical shape. In this work, a template-engaged strategy is developed to synthesize hierarchical NiS box-in-box hollow structures with double-shells. The NiS box-in-box hollow structures constructed by ultrathin nanosheets are evaluated as electrode materials for supercapacitors. As expected, the NiS box-in-box hollow structures exhibit excellent rate performance and impressive cycling stability due to their unique nano-architecture. More importantly, the synthetic method can be easily extended to synthesize other transition metal sulfides box-in-box hollow structures. For example, we have also successfully synthesized similar CuS and MnS box-in-box hollow structures. The present work makes a significant contribution to the design and synthesis of transition metal sulfides hollow structures with non-spherical shape and complex architecture, as well as their potential applications in electrochemical energy storage

Ultrathin mesoporous NiCo2O4 nanosheets supported on Ni foam as advanced electrodes for supercapacitors

A facile two-step method is developed for large-scale growth of ultrathin mesoporous nickel cobaltite (NiCo2O4) nanosheets on conductive nickel foam with robust adhesion as a high-performance electrode for electrochemical capacitors. The synthesis involves the co-electrodeposition of a bimetallic (Ni, Co) hydroxide precursor on a Ni foam support and subsequent thermal transformation to spinel mesoporous NiCo2O4. The as-prepared ultrathin NiCo2O4 nanosheets with the thickness of a few nanometers possess many interparticle mesopores with a size range from 2 to 5 nm. The nickel foam supported ultrathin mesoporous NiCo2O4 nanosheets promise fast electron and ion transport, large electroactive surface area, and excellent structural stability. As a result, superior pseudocapacitive performance is achieved with an ultrahigh specific capacitance of 1450 F g−1, even at a very high current density of 20 A g−1, and excellent cycling performance at high rates, suggesting its promising application as an efficient electrode for electrochemical capacitors

Growth of ultrathin mesoporous Co3O4 nanosheet arrays on Ni foam for high-performance electrochemical capacitors

An advanced electrode for high-performance electrochemical capacitors has been designed by growing ultrathin mesoporous Co3O4 nanosheet arrays on the Ni foam support. This unique 3D electrode manifests exceptional supercapacitive performance with ultrahigh specific capacitance at high current densities and excellent cycling stability

Top-down synthesis of interconnected two-dimensional carbon/antimony hybrids as advanced anodes for sodium storage

Nanoparticle-based electrode materials have sparked enormous excitement in the sodium-ion battery community because of potentially fast transport kinetics. However, they may suffer from many challenging static and dynamic problems, such as agglomeration of nanoparticles, high contact resistance, volume change, and instability of solid electrolyte interphase. Herein, we develop inter-connected 2D carbon nanosheets in which ultrasmall 0D Sb nanodots are embedded homogenously through a previously unexplored top-down strategy. Starting from the laminar structure K 3 Sb 3 P 2 O 14 , H 3 Sb 3 P 2 O 14 nanosheets are exfoliated by ion exchange and then serve as templates for the synthesis of carbon sheets and Sb nanodots. Such combination of multi-dimensional and multi-scale nanostructures in the electrode materials lead to excellent electron/ion transport kinetics and pronounced integrity of the electrode structure on cycling, providing a promising pathway for developing advanced electrode materials in terms of reversibility, rate capability and cycle life

General Strategy for Designing Core–Shell Nanostructured Materials for High-Power Lithium Ion Batteries

Because of its extreme safety and outstanding cycle life, Li₄Ti₅O₁₂ has been regarded as one of the most promising anode materials for next-generation high-power lithium-ion batteries. Nevertheless, Li₄Ti₅O₁₂ suffers from poor electronic conductivity. Here, we develop a novel strategy for the fabrication of Li₄Ti₅O₁₂/carbon core–shell electrodes using metal oxyacetyl acetonate as titania and single-source carbon. Importantly, this novel approach is simple and general, with which we have successfully produce nanosized particles of an olivine-type LiMPO₄ (M = Fe, Mn, and Co) core with a uniform carbon shell, one of the leading cathode materials for lithium-ion batteries. Metal acetylacetonates first decompose with carbon coating the particles, which is followed by a solid state reaction in the limited reaction area inside the carbon shell to produce the LTO/C (LMPO₄/C) core–shell nanostructure. The optimum design of the core–shell nanostructures permits fast kinetics for both transported Li⁺ ions and electrons, enabling high-power performance

Design and Tailoring of a Three-Dimensional TiO₂–Graphene–Carbon Nanotube Nanocomposite for Fast Lithium Storage

Nanocrystalline TiO₂ grown on conducting graphene nanosheets (GNS) and multiwalled carbon nanotubes (CNTs) via a solution-based method to form a three-dimensional (3D) hierarchical structure for fast lithium storage. CNTs in the unique hybrid nanostructure not only prevent the restacking of GNS to increase the basal spacing between graphene sheets but also provides an additional electron-transport path besides the graphene layer underneath of TiO₂ nanomaterials, increasing the electrolyte/electrode contact area and facilitating transportation of the electrolyte ion and electron into the inner region of the electrode. Such a 3D TiO₂–GNS–CNT nanocomposite had a large specific surface area of 291.2 m² g^–1 and exhibited ultrahigh rate capability and good cycling properties at high rates

Hierarchical Metal Sulfide/Carbon Spheres: A Generalized Synthesis and High Sodium-Storage Performance

The development of suitable anode materials is far from satisfactory and is a major scientific challenge for a competitive sodium-ion battery technology. Metal sulfides have demonstrated encouraging results, but still suffer from sluggish kinetics and severe capacity decay associated with the phase change. Herein we show that rational electrode design, that is, building efficient electron/ion mixed-conducting networks, can overcome the problems resulting from conversion reactions. A general strategy for the preparation of hierarchical carbon-coated metal sulfide (MS subset of C) spheres through thermal sulfurization of metal glycerate has been developed. We demonstrate the concept by synthesizing highly uniform hierarchical carbon coated vanadium sulfide (V2S3 subset of C) spheres, which exhibit a highly reversibly sodium storage capacity of 777mAhg(-1) at 100mAg(-1), excellent rate capability (410mAhg(-1) at 4000mAg(-1)), and impressive cycling ability