Lithium/Boron Co-doped Micrometer SiOx as Promising Anode Materials for High-Energy-Density Li-Ion Batteries

Morphology Variation of Ternary PdCuSn Nanocrystalline Assemblies and Their Electrocatalytic Oxidation of Alcohols

Metal alloys not only increase the composition and spatial distribution of elements but also provide the opportunity to adjust their physicochemical properties. Recently, multimetallic alloy nanocatalysts have attracted great attention in energy applications and the chemical industry. This work presents the production of three ternary PdCuSn nanocrystalline assemblies with similar compositions via a one-step hydrothermal method. The shape variation of assembly units from nanosheets and nanowires to nanoparticles were realized by adjusting the percentage of Sn in metal precursors. Experimental data show that PdCuSn nanowire networks showed the best catalytic activity by virtue of their optimized morphological characteristics and microscopic electronic structure. With electrooxidation of methanol, ethanol, ethylene glycol, and glycerol at 30 °C, PdCuSn nanowire networks demonstrated catalytic activity of 1129, 2111, 2540, and 1445 mA mg-1, respectively. The catalytic activity for alcohol oxidation is attributed to the production of the electronic structure and morphology features that are most suitable. This is achieved by introducing the proper quantities of Cu and Sn components in the first stage of synthesis. This study would help with the construction of high-efficiency nanostructured alloy catalysts by regulating the electronic structure and morphology.

Batch-Scale Synthesis and Interfacially Enhanced Stability of Silicon Suboxide-Based Anodes toward High-Performance Lithium-Ion Batteries

SiOx anode materials are among the most promising candidates for next-generation high-energy-density lithium-ion batteries (LIBs). However, their commercial application is hindered by poor conductivity, low initial Coulombic efficiency (ICE), and an unstable solid electrolyte interface. Developing cost-effective SiOx anodes with high electrochemical performance is crucial for advanced LIBs. To tackle these issues, this study utilized APTES as a silicon source and carbon nanotubes (CNTs) as additives to prepare a T-SiOx/C/CNTs composite material with N doping and in situ carbon coating using a "molecular assembly combined with controlled pyrolysis" strategy under mild conditions. The in situ carbon coating, formed by the pyrolysis of organic groups on the molecular precursor, effectively protects the inner SiOx active material. The introduced CNTs enhance electron migration and improve the rigidity of the carbon coating layer. The prelithiated T-SiOx@C/CNTs electrode achieves an ICE of 91.6%, with a specific capacity of 622 mAh g-1 after 400 cycles at 1 A g-1 and 475.8 mAh g-1 after 800 cycles. Full cell tests with commercial NCM811 cathodes further demonstrate the potential of T-SiOx@C/CNTs as a highly promising anode material. This work provides some insights into the rational design of advanced anode materials for LIBs, paving the way for their future development and application.

Novel binary regulated silicon-carbon materials as high-performance anodes for lithium-ion batteries

The massive volume dilation, unsteady solid electrolyte interphase, and weak conductivity about Si have failed to bring it to practical applications, although its potential capacity is up to 4200 mAh g-1. For solving these problems, novel binary regulated silicon-carbon materials (Si/BPC) were done by a sol-gel procedure combined with single carbonization. Analytical techniques were systematically utilized to examine the effects of element doping at several gradients on morphology, structure and electrochemical properties of composites, thus the optimal content was identified. Si/BPC preserves a discharge specific capacity of 1021.6 mAh g-1with a coulomb efficiency of 99.27% after 180 cycles at 1000 mA g-1, within the upgrade than single-doped and undoped. In rate test, it has a specific capacity of 1003.2 mAh g-1at a high current density of 5000 mA g-1, quickly back towards 2838.6 mAh g-1at 200 mA g-1. The inclusion of B and P elements is linked to the electrochemical characteristics. In the co-doped carbon layers, the synergistic impact of doping B and P accelerates the diffusion kinetics of lithium ions, boosts diffusion rate of Li+, offers low electrochemical impedance (45.75 Ω). This brings more defects to provide transport carriers and induces a substantial amount of electrochemically active sites, which fosters the storage of Li+, thus making silicon material electrochemically more active and potential.

Synthesis of Monodispersed Pd Nanoparticles and Ultrathin Twisty Pd Nanowire Networks for Electrooxidation of Ethanol

In recent years, preparing precious metal catalysts with a controllable morphology has become a hot research topic for researchers. In this study, monodispersed palladium (Pd) nanoparticles (NP) and ultrathin Pd twisty nanowire networks (TNN) were synthesized in a solvothermal system using N,N-dimethylformamide (DMF) and oleylamine (OAm) as solvents, Transmission electron microscopy (TEM) images reveal the successful synthesis of nanoparticles and ultrathin TNN microstructures. Electrochemical data show that the current densities of Pd-NP and Pd-TNN for the ethanol oxidation reaction (EOR) reach 1878 mA mg-1 and 1765 mA mg-1, respectively. Compared to commercial Pd/C, Pd-TNN and Pd-NP exhibit better catalytic stability, lower electron transfer barriers, and more resistance to catalyst poisoning. Temperature, pH value, and ethanol concentration are all favorable for the EOR. According to the experimental data, the mechanism of enhanced electrocatalytic activity of Pd-NP and Pd-TNN catalysts for ethanol oxidation is discussed. This paper presents a method for preparing catalysts with stabilized structures to develop Pd-based catalysts for electrocatalytic oxidation reactions.

Constructing a Stable Conductive Network for High-Performance Silicon-Based Anode in Lithium-Ion Batteries

The application of carbon nanotubes to silicon nanoparticles has been used to improve the electrical conductivity of silicon-carbon anodes and prevent agglomeration of silicon nanoparticles during cycling. In this study, the composites are synthesized through an uncomplicated technique that involves the ultrasonication mixing of pyrene derivatives and carbon nanotubes and the formation of complexes with silicon nanoparticles in ultrasonic dispersion and magnetic stirring and then treated under vacuum. When the prepared composites are applied as lithium-ion battery anodes, the Si@(POH-AOCNTs) electrode displays a high reversible capacity of 3254.7 mAh g-1 at a current density of 0.1 A g-1. Furthermore, it exhibits excellent cycling stability with a specific capacity of 1195.8 mAh g-1 after 500 cycles at 1.0 A g-1. The superior electrochemical performance may be attributed to a large π-conjugated electron system of pyrene derivatives, which prompts the formation of a homogeneous CNTs conductive network and ensures the effective electron transfer, while the interaction between hydroxyl functional groups of hydroxypyrene and binder synergizes with CNTs network to further enhance the cycling stability of the composite.

Design of a Bioinspired Robust Three-Dimensional Cross-Linked Polymer Binder for High-Performance Li-Ion Battery Applications

Si has the highest theoretical capacity (4200 mA h g-1) among conventional anode materials, such as graphite (372 mA h g-1), but its large volume expansion leads to deterioration of the battery performance. To overcome this problem (issue), we investigated the use of polysaccharide-based 3D cross-linked network binders for Si anodes, in which the polysaccharide formed an effective 3D cross-linked network around Si particles via cross-linking of polysaccharide with citric acid (CA). Sodium alginate (SA), a natural polysaccharide extracted from brown algae, is a suitable binder material for Si anodes because its abundant hydroxyl (-OH) and carboxyl (-COOH) groups form hydrogen and covalent bonds with the -OH groups present on the Si surface. We found that CA-cross-linked (CA-SA) could effectively prevent the volume expansion of Si anodes through the formation of 3D cross-linked network structures. In addition, the CA-SA binders provide enhanced adhesion strength, enabling the fabrication of more robust electrodes than those prepared using binders with linear structures ("linear binders"). In particular, the fabricated Si-based electrode (high mass loading of 1.5 mg cm-2) with CA-SA binder exhibited outstanding areal capacity (∼2.7 mA h cm-2) and excellent cycle retention (∼100% after 100 cycles).

Body Armor-Inspired Double-Wrapped Binder with High Energy Dispersion for a Stable SiOx Anode

The high specific capacity and relatively low volume expansion of silicon suboxide (SiO_x) highlight its potential as one of the most promising anode materials for lithium-ion batteries. Nevertheless, the traditional binder of polyacrylic acid (PAA) still cannot adapt to enormous stress during the repeated volume expansion/contraction owing to its intrinsic rigid backbone. Inspired by the "soft and hard composite body armor", we herein design a double-wrapped binder consisting of PAA with a high internal Young's modulus (hard part) and polyurethane (DOU) with a low external Young's modulus (soft part). When the SiO_x particle expands during lithiation, the rigid PAA firstly accommodates the volume change to dissipate most of the inner stress, and the elastic DOU with triple dynamic bonds serves as a buffer layer to absorb the residual stress via the breakage/formation of dynamic bonds. By optimizing the PAA/DOU ratio, the SiO_x anode can maintain the integrity during long-term cycling and deliver a relatively high reversible capacity of 1064.1 mAh g^-1 with a preeminent capacity retention of 83.7% at 0.5C after 300 cycles. Such a double-wrapped binder can provide a novel design strategy for multicomponent functional polymer binders toward high-performance SiO_x anodes.

An Elastic Cross-Linked Binder for Silicon Anodes in Lithium-Ion Batteries with a High Mass Loading

Due to the urgent demand for lithium-ion batteries (LIBs) with a high energy density, silicon (Si) possessing an ultrahigh capacity has aroused wide attention. However, its practical application is seriously hindered by enormous volume changes of the Si anode during cycling. Developing novel binders suitable for the Si anode has proven to be an effective strategy to improve its electrochemical performance. Herein, we constructed a three-dimensional network binder, in which the polyacrylic acid (PAA) long chains are cross-linked with one kind of amino acid, lysine (Lys). The abundant polar groups in PAA/Lys enable it to tightly adhere to the Si particles via hydrogen bonds, and the cross-linked structure prevents irreversible slipping of the PAA chains upon volume variation of the particles. The Si used was obtained from a sustainable route by recycling photovoltaic waste silicon. With high elasticity and strong adhesion, the PAA/Lys binder can effectively keep the structural integrity of the Si electrode and improve its electrochemical performance. The Si electrode using the PAA/Lys binder exhibits a good cycling stability (1008 mAh g^-1 at 2 A g^-1 after 250 cycles). Even with a high mass loading of 3.03 mg cm^-2, the Si anode can remain stable for 100 cycles at a high fixed areal capacity of 3.03 mAh cm^-2. This work gives a practical method to make stable Si electrodes using sustainable Si source and environmentally friendly amino acid-based binders.

Embedding Atomically Dispersed Iron Sites in Nitrogen-Doped Carbon Frameworks-Wrapped Silicon Suboxide for Superior Lithium Storage

Silicon suboxide (SiOx ) has attracted widespread interest as Li-ion battery (LIB) anodes. However, its undesirable electronic conductivity and apparent volume effect during cycling impede its practical applications. Herein, sustainable rice husks (RHs)-derived SiO2 are chosen as a feedstock to design SiOx /iron-nitrogen co-doped carbon (Fe-N-C) materials. Using a facile electrospray-carbonization strategy, SiOx nanoparticles (NPs) are encapsulated in the nitrogen-doped carbon (N-C) frameworks decorating atomically dispersed iron sites. Systematic characterizations including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) verify the existence of Fe single atoms and typical coordination environment. Benefiting from its structural and compositional merits, the SiOx /Fe-N-C anode delivers significantly improved discharge capacity of 799.1 mAh g-1 , rate capability, and exceptional durability, compared with pure SiO2 and SiOx /N-C, which has been revealed by the density functional theory (DFT) calculations. Additionally, the electrochemical tests and in situ X-ray diffraction (XRD) analysis reveal the oxidation of Lix Si phase and the storage mechanism. The synthetic strategy is universal for the design and synthesis of metal single atoms/clusters dispersed N-C frameworks encapsulated SiOx NPs. Meanwhile, this work provides impressive insights into developing various LIB anode materials suffering from inferior conductivity and huge volume fluctuations.

Templated Synthesis of SiO2 Nanotubes for Lithium-Ion Battery Applications: An In Situ (Scanning) Transmission Electron Microscopy Study

One of the weaknesses of silicon-based batteries is the rapid deterioration of the charge-storage capacity with increasing cycle numbers. Pure silicon anodes tend to suffer from poor cycling ability due to the pulverization of the crystal structure after repeated charge and discharge cycles. In this work, we present the synthesis of a hollow nanostructured SiO₂ material for lithium-ion anode applications to counter this drawback. To improve the understanding of the synthesis route, the crucial synthesis step of removing the ZnO template core is shown using an in situ closed gas-cell sample holder for transmission electron microscopy. A direct visual observation of the removal of the ZnO template from the SiO₂ shell is yet to be reported in the literature and is a critical step in understanding the mechanism by which these hollow nanostructures form from their core-shell precursors for future electrode material design. Using this unique technique, observation of dynamic phenomena at the individual particle scale is possible with simultaneous heating in a reactive gas environment. The electrochemical benefits of the hollow morphology are demonstrated with exceptional cycling performance, with capacity increasing with subsequent charge-discharge cycles. This demonstrates the criticality of nanostructured battery materials for the development of next-generation Li⁺-ion batteries.