factors: electrode materials, electrolytes, and separators. [18] Finding suitable electrode materials to promote and realize their commercialization is still considered one of the major challenges. [19][20][21] Up to now, electrode materials have commonly included carbon materials (CMs), [5,13,22] conducting polymer materials (CPMs), [23] transition metal oxides (TMOs), [24] and others. [25][26][27] However, they all have their respective shortcomings; for instance, CMs tend to restack and then decrease the specific surface area, which is an important index for CM performance. [28][29][30] CPMs show the same phenomenon that the original structure will collapse under long-term charge/discharge process. [23] Although the above two types of electrode materials have good electron conductivity, their changing specific surface area and structures during use make them unlikely to be promising electrode materials. TMOs always have a good reversible faradic reaction due to their valence flexibility. However, in comparison to CMs, their poor electron conductivity may lower their specific capacity. [31][32][33] Transition metal sulfides (TMSs) have attracted tremendous attention due to their high specific capacity. For example, nickel and cobalt sulfides (e.g., NiS x , CoS x ) have specific capacities that are double of their oxide counterparts (e.g., NiO x , CoO x ). [22,[34][35][36] This is because the replacement of oxygen with sulfur, an element with a lower electronegativity, increases the performance compared to TMOs. [37,38] However, their unyielding volume change during the cycling process has hindered their further development and application in lithium and sodium rechargeable batteries. [39] Though TMSs possess high specific capacities and excellent rate capabilities when used for SCs, it is difficult to achieve all these objectives simultaneously from a single material. Therefore, the hybridization of different materials with different properties is becoming an interesting research area. Recent papers have testified that the adulteration of graphene or graphene derivatives can solve these issues and increase the electrochemical performance of energy storage devices. [40][41][42] It can be attributed to the properties of graphene: 2D conductive networks, a large specific surface area, and good physicochemical stability. In addition to these properties, their porous structure can effectively promote the diffusion of electrolyte ions. Therefore, 2D graphene is one of the ideal support framework materials to prepare TMS@graphene composites for electrode materials. [43][44][45][46] Transition metal sulfides, as an important class of inorganics, can be used as excellent electrode materials for various types of electrochemical energy storage, such as lithium-ion batteries, sodium-ion batteries, supercapacitors, and others. Recent works have identified that mixing graphene or graphene derivatives with transition metal sulfides can result in novel composites with better electrochemical performance. This review summarizes ...

Metal–organic frameworks (MOFs), which consist of central metal nodes and organic linkers, constitute a fast growing class of crystalline porous materials with excellent application potential. Herein, a series of Mn‐based multimetallic MOF (bimetallic and trimetallic MIL‐100) nano‐octahedra are prepared by a facile one‐pot synthetic strategy. The types and proportions of the incorporated elements can be tuned while retaining the original topological structure. The introduction of other metal ions is verified at the atomic level by combining X‐ray absorption fine structure experiments and theoretical calculations. Furthermore, these multimetallic Mn‐based MIL‐100 nano‐octahedra are utilized as sulfur hosts to prepare cathodes for Li–S batteries. The MnNi‐MIL‐100@S cathode exhibits the best Li–S battery performance among all reported MIL‐100@S composite cathode materials, with a reversible capacity of ≈708.8 mAh g−1 after 200 cycles. The synthetic strategy described herein is utilized to incorporate metal ions into the MOF architecture, of which the parent monometallic MOF nano‐octahedra cannot be prepared directly, thus rationally generating novel multimetallic MOFs. Importantly, the strategy also allows for the general synthesis and study of various micro‐/nanoscale MOFs in the energy storage field.

batteries, sodium-selenium (Na-Se) batteries, Li-tellurium (Li-Te) batteries, and Na-S batteries) have their own distinctive applications due to their various characteristics. To explore new materials with high performance, large studies have been devoted to the development of nextgeneration batteries.Porous carbon (PC) materials possess many unique properties due to their large surface areas, high conductivity, large pore volumes, high thermal stability, and surface functionalities, [22][23][24] leading to their wide use in energy storage and conversion. Traditionally, PC can be obtained via various methods, such as the direct heat treatment of organic precursors, hard template or nanocast methods, and soft template methods. However, the production of PC from these methods cannot be scaled-up because of certain barriers (disordered structure with wide size distributions, complicated processes, etc.). [23,25,26] Metal-organic frameworks (MOFs) have drawn wide research interest as a novel class of porous materials that are crystalline materials consisting of metal ions and organic ligands. [4,21,[27][28][29][30][31] Since the report on the MOF-templated synthesis of PC in 2008, [32] a large number of studies have been reported on the use of MOFs as suitable precursors/templates for carbon synthesis. [22,26,[33][34][35] At present, a large number of studies indicate that zeolitic imidazolate framework-8 (ZIF-8), MOF-5, MIL-125 (Ti) (MIL = Materials of Institute Lavoisier), and ZIF-67 with excellent thermal stability and unique porous structures are the more commonly used MOF precursors (Scheme 1). [3,36,37] All of them, ZIF-8, possessing nitrogen-containing ligands, has high porosity and thermal stability. [38][39][40] MOF-5 possesses excellent thermal stability, high porosity, and so on. [41] MIL-125, an active photocatalyst, includes cyclic octamers of TiO 2 octahedra. [42,43] ZIF-67 has a tunable pore aperture, highly stable structure, and catalytic activity. [37,44,45] The above-mentioned MOFs have been widely used for gas adsorption, molecular separation, catalysis, batteries, supercapacitors, and so on. [13,14,33] Moreover, carbon hybrids containing nanostructured metal species (e.g., metal oxides (MOs)) are likely to form under in situ carbonization conditions. [46] Compared with the carbonaceous materials from conventional precursors, MOF-derived carbon materials have significant advantages with high specific surface areas, tailorable porosities, unique morphologies, and easy functionalization with other heteroatoms. [14,23,31] For example, Xu and co-workers [47] obtained 1D carbon nanorods via the pyrolysis The applications of carbon and carbon-based materials with high porosity, high surface area, and functionalities based on metal-organic framework precursors and/or templates have attracted significant research interest in recent years, particularly in the field of batteries. The chemical and physical properties of carbon and carbon-based materials obtained by the heat treatment of various metal-organic ...

based on connecting central metal atoms/ clusters and organic ligands, have attracted considerable attention. [3][4][5] MOFs can be rationally designed by modifying their constituting metal atoms/clusters and organic ligands, allowing a control of their shapes and sizes. [6] Shapes are typically controlled by introducing modulators (cosolvents or surfactants) that preferentially adsorb onto specific crystal planes, consequently hampering their growth. Furthermore, the size can be adjusted by changing the solvent ratio or reaction time. For these reasons, MOFs are endowed with outstanding properties and potential applications, such as in sensors, [7] electrocatalysis, [8,9] and energy-storage devices. [10,11] The porous structure of MOFs makes them promising host materials to anchor sulfur in Li-S batteries, and this has attracted considerable attention because of their high theoretical capacity (1675 mAh g −1 ). [12,13] The main obstacle to impede commercialization of Li-S batteries is the shuttle effect, leading to an irreversible loss of sulfur during the discharge process. [14] At present, a variety of carbonaceous materials have been adopted as host materials to enable uniform dispersion of sulfur. [15] However, the physical confinement of lithium polysulfides (LPS, chemical formula: Li 2 S x , 4 ≤ x ≤ 8) in nonpolar carbonaceous materials is not sufficient to prevent Metal-organic frameworks (MOFs) with controllable shapes and sizes show a great potential in Li-S batteries. However, neither the relationship between shape and specific capacity nor the influence of MOF particle size on cyclic stability have been fully established yet. Herein, MIL-96-Al with various shapes, forming hexagonal platelet crystals (HPC), hexagonal bipyramidal crystals (HBC), and hexagonal prismatic bipyramidal crystals (HPBC) are successfully prepared via cosolvent methods. Density functional theory (DFT) calculations demonstrate that the HBC shape with highly exposed (101) planes can effectively adsorb lithium polysulfides (LPS) during the charge/discharge process. By changing the relative proportion of the cosolvents, HBC samples with different particle sizes are prepared. When these MIL-96-Al crystals are used as sulfur host materials, it is found that those with a smaller size of the HBC shape deliver higher initial capacity. These investigations establish that different crystal planes have different adsorption abilities for LPS, and that the MOF particle size should be considered for a suitable sulfur host. More broadly, this work provides a strategy for designing sulfur hosts in Li-S batteries.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202107836.

Polypyrrole coated hollow MOF composites are synthesized for Li–S battery electrodes, combining the porous structure of ZIF-67 and high conductivity of polypyrrole. The composites obtained a high initial specific capacity and good cycling performance.

The introduction of high-entropy into Prussian blue analogues (PBAs) has yet to attract attention in the field of lithium-sulfur battery materials. Herein, we systematically synthesize a library of PBAs from binary to high-entropy by a facile coprecipitation method. The coordination environment in PBAs is explored by X-ray absorption fine structure spectroscopy, which together with elemental mapping confirm the successful introduction of all metals. Importantly, electrochemical tests demonstrate that high-entropy PBA can serve as polysulfide immobilizer to inhibit shuttle effect and as catalyst to promote polysulfides conversion, thereby boosting its outstanding performance. Additionally, a variety of nanocubic metal oxides from binary to senary are fabricated by using PBAs as sacrificial precursors. We believe that a wide range of new materials obtained from our coprecipitation and pyrolysis methodology can promote further developments in research on PBA systems and sulfur hosts.

The practical application of Li‐S batteries is largely impeded by the “shuttle effect” generated at the cathode which results in a short life cycle of the battery. To address this issue, this work discloses a bimetallic metal‐organic framework (MOF) as a sulfur host material based on Al‐MOF, commonly called (Al)MIL‐53. To obtain a high‐adsorption capacity to lithium polysulfides (Li2Sx, 4 ≤ x ≤ 8), we present an effective strategy to incorporate sulfiphilic metal ion (Cu2+) with high‐binding energy to Li2Sx into the framework. Through a one‐step hydrothermal method, Cu2+ is homogeneously dispersed in Al‐MOF, producing a bimetallic Al/Cu‐MOF as advanced cathode material. The macroscopic Li2S4 solution permeation test indicates that the Al/Cu‐MOF has better adsorption capacity to lithium polysulfides than monometallic Al‐MOF. The sulfur‐transfusing process is executed via a melt‐diffusion method to obtain the sulfur‐containing Al/Cu‐MOF (Al/Cu‐MOF‐S). The assembled Li‐S batteries with Al/Cu‐MOF‐S yield improved cyclic performance, much better than that of monometallic Al‐MOF as sulfur host. It is shown that chemical immobilization is an effective method for polysulfide adsorption than physical confinement and the bimetallic Al/Cu‐MOF, formed by incorporation of sulfiphilic Cu2+ into porous MOF, will provide a novel and powerful approach for efficient sulfur host materials.

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