Cross‐Linking Tin‐Based Metal‐Organic Frameworks with Encapsulated Silicon Nanoparticles: High‐Performance Anodes for Lithium‐Ion Batteries

A sheet-like tin-based metal-organic framework with enhanced lithium storage

A novel sheet-like tin-based metal-organic framework exhibited a specific capacity for lithium storage as high as 1033.3 mAh g-1 at 200 mA g-1 with excellent cycling stability. This framework, due to its unique porous structure and multiple lithium storage sites, could better cope with challenges occurring during lithium insertion/extraction than could traditional tin materials.

Inorganic-organic hybrid Cu-dipyridyl semiconducting polymers based on the redox-active cluster [SFe3(CO)9]2-: filling the gap in iron carbonyl chalcogenide polymers

The construction of sulfur-incorporated cluster-based coordination polymers was limited and underexplored due to the lack of efficient synthetic routes. Herein, we report facile mechanochemical ways toward a new series of SFe3(CO)9-based dipyridyl-Cu polymers by three-component reactions of [Et4N]2[SFe3(CO)9] ([Et4N]2[1]) and [Cu(MeCN)4][BF4] with conjugated or conjugation-interrupted dipyridyl ligands, 1,2-bis(4-pyridyl)ethylene (bpee), 1,2-bis(4-pyridyl)ethane (bpea), 4,4'-dipyridyl (dpy), or 1,3-bis(4-pyridyl)propane (bpp), respectively. X-ray analysis showed that bpee-containing 2D polymers demonstrated unique SFe3(CO)9 cluster-armed and cluster-one-armed coordination modes via the hypervalent μ5-S atom. These S-Fe-Cu polymers could undergo flexible structural transformations with the change of cluster bonding modes by grinding with stoichiometric amounts of dipyridyls or 1/[Cu(MeCN)4]+. They exhibited semiconducting behaviors with low energy gaps of 1.55-1.79 eV and good electrical conductivities of 3.26 × 10-8-1.48 × 10-6 S cm-1, tuned by the SFe3(CO)9 cluster bonding modes accompanied by secondary interactions in the solid state. The electron transport efficiency of these polymers was further elucidated by solid-state packing, X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES), density of states (DOS), and crystal orbital Hamilton population (COHP) analysis. Finally, the solid-state electrochemistry of these polymers demonstrated redox-active behaviors with cathodically-shifted patterns compared to that of [Et4N]2[1], showing that their efficient electron communication was effectively enhanced by introducing 1 and dipyridyls as hybrid ligands into Cu+-containing networks.

Organic Anode Materials for Lithium-Ion Batteries: Recent Progress and Challenges

In the search for novel anode materials for lithium-ion batteries (LIBs), organic electrode materials have recently attracted substantial attention and seem to be the next preferred candidates for use as high-performance anode materials in rechargeable LIBs due to their low cost, high theoretical capacity, structural diversity, environmental friendliness, and facile synthesis. Up to now, the electrochemical properties of numerous organic compounds with different functional groups (carbonyl, azo, sulfur, imine, etc.) have been thoroughly explored as anode materials for LIBs, dividing organic anode materials into four main classes: organic carbonyl compounds, covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and organic compounds with nitrogen-containing groups. In this review, an overview of the recent progress in organic anodes is provided. The electrochemical performances of different organic anode materials are compared, revealing the advantages and disadvantages of each class of organic materials in both research and commercial applications. Afterward, the practical applications of some organic anode materials in full cells of LIBs are provided. Finally, some techniques to address significant issues, such as poor electronic conductivity, low discharge voltage, and undesired dissolution of active organic anode material into typical organic electrolytes, are discussed. This paper will guide the study of more efficient organic compounds that can be employed as high-performance anode materials in LIBs.

Redox-Active Tin Metal-Organic Framework with a Thiolate-Based Ligand

Metal-organic frameworks (MOFs) and coordination polymers composed of thiolates as coordinating functional groups are interesting materials with unique optical and electronical properties. Herein, we report the preparation of KGF-4 and KGF-10, two Sn-MOF crystal structures with bonds between Sn and thiolate. KGF-10 was isolated as a pure phase and found to exhibit redox properties and a semiconducting band structure, as confirmed by first-principles (density functional theory) calculations.

Effect of NaOH molarities to the microstructure and sodium storage performance of the Sn-MOF derived SnO2microporous rod

In this study, we demonstrated a facile method to prepare a novel SnO₂microporous rod with various microstructures by controlling NaOH molarities in precursor synthesis processes. Four different molarities of NaOH solution (0.005 M, 0.048 M, 0.12 M and 0.5 M) were used together with o-phthalic acid in Sn-MOF synthesis to determine the effect of ligand [o-C₆H₄CO222-] concentration on microstructure evolution. It was found that increasing NaOH molarity can effectively decrease the size of Sn-MOF rods. Then, the SnO₂microporous rods were obtained by calcinating the as-prepared Sn-MOF as microstructures. Under an optimized experimental condition (NaOH molarity of 0.12 M), the SnO₂rods shows a modest initial coulombic efficiency of 61.3% with a high reversible sodium storage capacity of 503 mAh g^-1after 150 cycles at 50 mA g^-1. Moreover, an impressive reversible sodium storage capacity of 206 mAh g^-1can be obtained at long-term cycling performance (800 cycles at current density of 2 A g^-1). Effects of morphologies to electrochemical performances have been further discussed in aspects of intrinsic resistance, pseudocapacitive contribution, surface area and porous structure and microstructural stability, and the enhanced electrochemical performance could be attributed to factors of enhanced pseudocapacitive charge contribution, optimized microstructures, and structural stability, which ensure the SnO₂-0.12 M to have a good rate performance and cyclability. This nanoscale-engineering method adopted here could be a promising path to fabricate SnO₂-based anodes with novel microstructures for sodium storage applications.

Large-Scale Electric-Field Confined Silicon with Optimized Charge-Transfer Kinetics and Structural Stability for High-Rate Lithium-Ion Batteries

The stereospecific design of the interface effects can optimize the electron/Li-ion migration kinetics for energy-storage materials. In this study, an electric field was introduced to silicon-based materials (C-SiO_x@Si/rGO) through the rational construction of multi-heterostructures. This was achieved by manipulating the physicochemical properties at the atomic level of advanced Li-ion batteries (LIBs). The experimental and density functional theory calculations showed that the unbalanced charge distribution generated a large potential difference, which in turn induced a large-scale electric-field response with a boosted interfacial charge transfer in the composite. The as-prepared C-SiO_x@Si/rGO anode showed advanced rate capability (i.e., 1579.0 and 906.5 mAh g^-1 at 1000 and 8000 mA g^-1, respectively) when the migration paths of the Li-ion/electrons hierarchically optimized the large electric field. Furthermore, the C-SiO_x@Si/rGO composite with a high SiO_x@Si mass ratio (73.5 wt %) demonstrated a significantly enhanced structural stability with a 40% volume expansion. Additionally, when coupled with the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) cathode, the NCM//C-SiO_x@Si/rGO full cell delivers superior Li-ion storage properties with high reversible capacities of 157.6 and 101.4 mAh g^-1 at 500 and 4000 mA g^-1, respectively. Therefore, the electric-field introduction using optimized electrochemical reaction kinetics can assist in the construction of other high-performance LIB materials.

Tin and Tin Compound Materials as Anodes in Lithium-Ion and Sodium-Ion Batteries: A Review

Tin and tin compounds are perceived as promising next-generation lithium (sodium)-ion batteries anodes because of their high theoretical capacity, low cost and proper working potentials. However, their practical applications are severely hampered by huge volume changes during Li⁺ (Na⁺) insertion and extraction processes, which could lead to a vast irreversible capacity loss and short cycle life. The significance of morphology design and synergic effects-through combining compatible compounds and/or metals together-on electrochemical properties are analyzed to circumvent these problems. In this review, recent progress and understanding of tin and tin compounds used in lithium (sodium)-ion batteries have been summarized and related approaches to optimize electrochemical performance are also pointed out. Superiorities and intrinsic flaws of the above-mentioned materials that can affect electrochemical performance are discussed, aiming to provide a comprehensive understanding of tin and tin compounds in lithium(sodium)-ion batteries.