Surface Of Si Nanoparticles Research Articles

Constructing stress-release layer on Si nanoparticles for high-performance lithium storage

Tailing structures of silicon anode to alleviate the mechanical stress has an important significance in the development of lithium-ion batteries (LIBs). Herein, the stress-released layer of N-doped cubic carbon on the surface of Si nanoparticles (Si@NCC) is explored to stabilize the electrode. Endowed with the unique superiority, the Si@NCC electrode delivers an impressive lithium storage performance with high specific capacity of 630 mAh/g at 0.1 A/g, excellent cycling stability (72.0 % capacity retention after 100 cycles at 0.1 A/g) and good rate capability (375 mAh/g at 2 A/g). It has been demonstrated that the N-doped cubic carbon shell with high conductivity can effectively limit the expansion and agglomeration of Si nanoparticles. Besides, the COMSOL simulations of the stress distributions in materials confirm that the N-doped cubic carbon layer could remarkably decrease the stress originated from the volume expansion of Si nanoparticles during the lithiation. Therefore, this work provides ideas for the mechanical effect of Si-based anodes for lithium storage and sheds lights on the designing advanced materials toward high-performance energy storage devices.

Bi-Directional H-Bonding Modulated Soft/Hard Polyethylene Glycol-Polyaniline Coated Si-Anode for High-Performance Li-Ion Batteries.

Ultrahigh-capacity silicon (Si) anodes are essential for the escalating energy demands driven by the booming e-transportation and energy storage field. However, their practical applications are strictly hampered by their intrinsically low electroconductivity, sluggish Li-ion diffusion, and undesirably large volume change. Herein, a high-performance Si anode, comprised of a modulated soft/hard coating of polyethylene glycol (PEG) (as Li-ion conductor) and polyaniline (PANI) (as electron conductor) on the surface of Si nanoparticles (NPs) through H-bonding network, is introduced. In this design, the abundant ─OH groups of soft PEG allow it to uniformly cover Si NPs while the hard PANI binds to PEG through its ─N─H group, thus constructing a tight connectin between Si and PEG-PANI (PP). Consequently, the elastic PP allows Si@PP to accommodate the huge volume expansion while possessing fine electronic/ionic conductivity. Therefore, the Si@PP anode exhibits a high initial Coulombic efficiency of 90.5% and a stable capacity of 1871mAhg-1 after 100 cycles at 1Ag-1 with a retention of 85.7%. Additionally, the Si@PP anode also demonstrates a high areal capacity of 3.01mAhcm-2 after 100 cycles at 0.5Ag-1. This work reveals a scalable interface design of multi-layer multifunctional coatings for high-performance electrode materials in next-generation Li-ion batteries.

Well-Dispersed Bi nanoparticles for promoting the lithium storage performance of Si Anode: Effect of the bridging Bi nanoparticles

Silicon (Si) is considered a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity of up to 4200 mAh/g. However, the poor cycling and rate performances of Si induced by the low intrinsic electronic conductivity and large volume expansion during the lithiation/delithiation process limit its practical application. Herein, a novel silicon/bismuth@nitrogen-doped carbon (Si/Bi@NC) composite with nanovoids was synthesized and investigated as an advanced anode material for LIBs. In such a structure, ultrafine bismuth nanoparticles coupled with an N-doped carbon layer were introduced to modify the surface of Si nanoparticles. Subsequently, the lithiated LixBi has excellent high ionic conductivity and acts as a fast transport bridge for lithium ions. The introduced carbon coating layer and nanovoids can buffer the volume expansion of Si during the lithiation/delithiation process, thus maintaining structural stability during the cycling process. As a result, the Si/Bi@NC composite exhibits excellent electrochemical performance, providing a relatively high capacity of 955.8 mAh/g at 0.5 A/g after 450 cycles and excellent rate performance with a high capacity of 477.8 mAh/g even at 10.0 A/g. Furthermore, the assembled full cell with LiFePO4 as cathode and pre-lithium Si/Bi@NC as anode can provide a high capacity of 138.8 mAh/g at 1C after 90 cycles, exhibiting outstanding cycling performance.

Self-standing high-performance Si nanoparticle anchored porous carbon fiber composites for Li-ion batteries

Silicon (Si) is a highly promising anode candidate for lithium-ion batteries. However, the huge volume change of Si during the lithiation/delithiation process might cause serious structural damage, thereby restricting its potential application. Herein, a novel self-standing electrode consisting of porous carbon coated Si (Si@p-C) nanoparticles and carbon fibers (Si@p-C/p-CF) is prepared by a facile electrospinning technique. The three-dimensional carbon fiber framework derived from polyacrylonitrile serves as the support for self-standing electrode, which exhibits superior flexibility and satisfactory electrolyte penetration ability. The porous carbon matrix on the surface of Si nanoparticles can effectively buffer the volume expansion of Si during cycling and prevent direct contact between Si and the electrolyte. Attributed to these merits, the obtained (Si@p-C)0.5/p-CF electrode exhibits outstanding cycling stability with a specific capacity of 940 mAh g−1 at 0.2 A g−1 after 400 cycles, delivering great application potential.

Characteristics and electrochemical performances of nickel@nano‐silicon/carbon nanofibers composites as anode materials for lithium secondary batteries

AbstractSi is a next‐generation ideal anode material for Li‐ion batteries (LIBs) because of its high‐theoretical capacity (4200 mAh/g) and natural abundance. However, severe volume expansion and unstable solid electrolyte interface (SEI) film formation during lithiation/delithiation, and poor electron conductivity have significantly restricted the commercial application of Si. In this study, transition metal‐coated Si was synthesized and used as the anode material of LIBs. The transition metal salt of Ni was dissolved in an aqueous solution and used to coat the metal surface of Si nanoparticles. The coating was achieved by dropwise addition of metal solutions into Si dispersions. Thereafter, carbon nanofibers (CNFs) were grown on the transition metal‐coated Si nanoparticles via chemical vapor deposition method. The morphologies, compositions, and crystal quality of transition metal@Si/CNFs composites were characterized by transmission electron microscopy, scanning electron microscopy, x‐ray diffraction, Raman spectroscopy, and thermogravimetric analysis. The electrochemical characteristics of the hybrid anodes were investigated using a coin cell and battery tester. Voltage profile measurements at 0.1 A/g of 0.02 M‐Ni@Si/CNFs composite showed satisfactory initial Coulombic efficiency of 85.6%; 0.01 M‐Ni@Si/CNFs composite exhibited high initial capacity of 1300.9 mAh/g retained to 828.4 mAh/g after 100 cycles, corresponding to 63.7% capacity retention. Even at high current densities, the 0.02 M‐Ni@Si/CNFs composite delivered 342.78 mAh/g of capacity at 5 A/g. This work realizes a Si‐based hybrid anode from Ni‐coated Si catalyst used for direct CNFs synthesis with a stable SEI layer, superior initial Coulombic efficiency with satisfactory cycle and rate performance suitable for commercialized advanced battery applications.

Tracking the Oxidation of Silicon Anodes Using Cryo-EELS upon Battery Cycling.

Silicon is a high-capacity material for the anode of a rechargeable lithium-ion battery. One of the fundamental challenges for using Si in anodes is capacity fading, which has been revealed to be partially associated with the interfacial instability between the Si and liquid electrolyte due to the large volume swing of Si upon charging and discharging. Smart nanoscale design concepts, either presynthesized or formed in situ, have led to the mitigation of the detrimental factors associated with the volume swing of Si. However, it has never been clear how the chemical state of Si evolves and contributes to the capacity fading upon battery cycling. Here, we use cryo-electron energy loss spectroscopy to directly monitor, at a subnanometer scale, the chemical evolution of Si upon battery cycling. We discover that during the cycling process Si particles are progressively oxidized to form SiO2, which is initiated from the particle surface and gradually penetrates toward the interior of the particle, directly contributing to the capacity fading. Possible mechanisms of Si oxidation are postulated. We further show how the cycling stability can be improved by an electrolyte additive to form an effective passivation layer, representatively, even a small concentration of fluoroethylene carbonate causes the formation of an LiF layer on the Si nanoparticle surface that prevents Si oxidation and improves cycling stability. The present work unveils Si oxidation as a previously unrecognized factor that contributes to capacity fading, therefore providing insight into the design of anodes with Si-based materials.

Encapsulation of nano-Si into MOF glass to enhance lithium-ion battery anode performances

Although metal-organic framework (MOF) glasses have exhibited high potential to be applied as anode materials for lithium-ion batteries (LIBs), their electrochemical performances still need to be greatly improved to match the rapid development of green energy technologies. Silicon is a promising candidate for the next generation of LIB anode but suffers from vast volume fluctuations upon lithiation/delithiation. Here, we present a strategy to in situ grow a kind of MOF, namely, cobalt-ZIF-62 (Co(imidazole)1.75(benzimidazole)0.25) on the surface of Si nano particles, and then to transform the thus-derived material into Si@ZIF-glass composite (SiZGC) through melt-quenching. The robust hierarchical structure of the SiZGC based anode exhibits the specific capacity of ∼650 mA h g-1, which is about three times that of pure ZIF glass and about six times that of pristine ZIF crystal at 1 A g-1 after 500 cycles. The origin of this huge enhancement is revealed by performing structural analyses. The ZIF glass phase can not only contribute to lithium storage, but also buffer the volume changes and prevent the aggregation of Si nano particles during lithiation/delithiation processes.

Influence of Fluoroethylene Carbonate in the Composition of an Aprotic Electrolyte on the Electrochemical Characteristics of LIB’s Anodes Based on Carbonized Nanosilicon

Here, we study an effect of FEC addition to TC-E918 electrolyte on the electrochemical performance of Si/C negative electrodes. The anodes were fabricated from nanosilicon powder coated with a carbon shell by means of a standard slurry technique. The low-temperature reduction of fluorocarbon on the surface of Si nanoparticles was used to form the shell. It was shown that the presence of FEC in the electrolyte increases the cyclic stability of the electrodes and maintains a 1.5-fold higher discharge capacity during 300 cycles. Impedance measurements were used to study changes in the electrode parameters during long-term cycling with and without FEC additives.

A delicately designed functional binder enabling in situ construction of 3D cross‐linking robust network for high‐performance Si/graphite composite anode

AbstractThe silicon (Si)‐based anodes suffer from large volume expansion in the lithiation process. Aiming at improving the cycling stability of a Si/graphite composite anode processed by chemical vapor deposition (CVD) method, a functional aqueous binder was delicately designed and synthesized via an aqueous copolymerization of lithium acrylate and vinyl triethoxy silane (VTEO). The PAA‐VTEO binder can in situ react with the silanol groups on the surface of Si nanoparticles to form a robust 3D cross‐linked network. The resulting extremely high modulus and hardness of this integrated 3D network structure effectively restrained the volume expansion effect and significantly enhanced the electrochemical cycling stability of the CVD‐Si@graphite composite anode. This work will provide new perspectives in designing functional binder for Si‐based anodes.

Eco-Friendly Water-Processable Polyimide Binders with High Adhesion to Silicon Anodes for Lithium-Ion Batteries.

Silicon is an attractive anode material for lithium-ion batteries (LIBs) because of its natural abundance and excellent theoretical energy density. However, Si-based electrodes are difficult to commercialize because of their significant volume changes during lithiation that can result in mechanical damage. To overcome this limitation, we synthesized an eco-friendly water-soluble polyimide (W-PI) precursor, poly(amic acid) salt (W-PAmAS), as a binder for Si anodes via a simple one-step process using water as a solvent. Using the W-PAmAS binder, a composite Si electrode was achieved by low-temperature processing at 150 °C. The adhesion between the electrode components was further enhanced by introducing 3,5-diaminobenzoic acid, which contains free carboxylic acid (–COOH) groups in the W-PAmAS backbone. The –COOH of the W-PI binder chemically interacts with the surface of Si nanoparticles (SiNPs) by forming ester bonds, which efficiently bond the SiNPs, even during severe volume changes. The Si anode with W-PI binder showed improved electrochemical performance with a high capacity of 2061 mAh g−1 and excellent cyclability of 1883 mAh g−1 after 200 cycles at 1200 mA g−1. Therefore, W-PI can be used as a highly effective polymeric binder in Si-based high-capacity LIBs.

MXene Enables Stable Solid‐Electrolyte Interphase for Si@MXene Composite with Enhanced Cycling Stability

AbstractSilicon (Si) has been gaining considerable attention in the field of Li‐ion batteries although unstable solid‐electrolyte interphase (SEI), extreme volume changes and inferior conductivity hinder its practical application. Herein, ultrasonic‐assisted electrostatic self‐assembly of fluidic colloidal coprecipitation of MXene wrapped Si nanoparticles (Si@MXene) is proposed. Utilizing the natural negatively charged MXene to capture positive‐charged Si nanoparticles, the homogeneous Ti3C2Tx MXene coating on Si nanoparticles prevents the nanoparticles from directly contacting the electrolyte and thus enables the formation of a stable SEI film on the composite particulates. Due to the elimination of unstable solid‐electrolyte interphase on the surface of Si nanoparticles, Si@MXene delivers high capacity and excellent retention stability of 94 % after 100 cycles. The strategy demonstrated here offers the rational design of MXene‐coated Si anodes with high capacity and superior cycling stability.

Interface Engineering of Silicon and Carbon by Forming a Graded Protective Sheath for High-Capacity and Long-Durable Lithium-Ion Batteries.

Silicon is one of the most promising anode materials for lithium-ion batteries, whereas its low electronic conductivity and huge volumetric expansion upon lithiation strongly influence its prospective applications. Herein, we develop a facile method to introduce a graded protective sheath onto the surface of Si nanoparticles by utilizing lignin as the carbon source and Ni(NO3)2 as the auxiliary agent. Interestingly, the protective sheath is composed of NiSi2, SiC, and C from the interior to the exterior, thereby guaranteeing excellent compatibility between the neighboring components. Thanks to this unique coating layer, the obtained nanocomposite delivers a large reversible specific capacity (1586.3 mAh g-1 at 0.2 A g-1), excellent rate capability (879.4 mAh g-1 at 5 A g-1), and superior cyclability (88.2% capacity retention after 500 cycles at 1 A g-1). Such great performances are found to derive from a slight volumetric expansion, high Li+ ion diffusion coefficients, good interface stability, and fast electrochemical kinetics. These properties are obviously superior to those of their counterparts, benefiting from the interface engineering. This study offers new insights into constructing high-capacity and long-durable electrode materials for energy storage.

Synergistic carbon coating of MOF-derived porous carbon and CNTs on silicon for high performance lithium-ion batteries

Silicon has been considered as one of the most potential alternatives to traditional graphite anode materials in lithium-ion batteries (LIBs) due to its high specific capacity. However, the practical application of silicon is hampered by its inherent low conductivity and huge volumetric expansion during cycling. Herein, a hybrid of [email protected] nanotubes (CNTs)@carbon nanocomposites in which Si nanoparticles tangled with CNTs are encapsulated into metal-organic-frameworks (MOFs) carbon shell was synthesized through chemical vapor deposition and MOF self-template methods. By growing CNTs on the surface of Si nanoparticles, it is possible to facilitate their encapsulation in ZIF-67 crystals. In addition, the synergistic effect between CNTs and carbon shells doped with nitrogen can efficaciously buffer the expansion of structure and enhance the conductivity of materials. Besides, the porosity of carbon shell and the connection of CNTs can provide channels for the penetration and diffusion of Li+. On the basis of the above merits, the reversible capacity of the resulted composite remains 568.8 mAh g−1 after 200 cycles at 1 A g−1. Moreover, it exhibits a preferable rate performance, thus indicating that this composite is a promising anode material for LIBs.

Facile fabrication of oxide layer for si anode with enhanced lithium storage performances via plasma oxidation

Fabrication of oxide layer over Si-based anode materials is recognized as a promising strategy to enhance the cycling performance of Si-based anodes through alleviating the severe volume variation during the lithiation/delithiation processes. In this work, an extremely simple and green plasma oxidation strategy is exploited to fabricate SiOx layer on the surface of Si nanoparticles. The obtained Si@SiOx materials deliver significant enhanced cycling stability (1201 mAh g−1 at 200th cycle) and promoted initial coulombic efficiency (89.96%) for application in lithium ions batteries (LIBs). The fabricated SiOx layer, which can not only serve as mechanical protect coating to buffer the huge volume change of Si, but also improve the electrolyte wettability of anode to facilitate the contact between electrolyte and electrode, thus promoting the transmission of lithium ions in the electrode. The presented work provides a simple and energy-efficiency and absolute green method to modify the surface of nanoparticles has been inspired preliminarily, and the prepared Si@SiOx materials exhibit promising electrochemical performances could be applied in the energy storage field.

Ternary Cross-Linked Multi-Functional Blended Polymers for High-Performance Silicon Anodes in Lithium-Ion Batteries

Silicon (Si) based anode material is highly attractive for next-generation lithium‐ion batteries (LIBs) due to its unparalleledtheoretical capacity and abundance. However, a severe problem of Si is the significant volume change associated with thelithiation processes, resulting in reduced capacity retention. Researchers have traditionally considered the roles ofinteractive binders and conductive additives as separate entities. These two components often lead to remarkablydecreased mass ratio of Si to nonactive material, which inevitably limits the electrode capacity. To achieve an enhanceutilization efficiency, herein, we have developed a multifunctional nanocomposite binder for high capacity nano-size Sibasedmaterial through a cross-linked polymer of carboxymethylcellulose (CMC), polyacrylic acid (PAA) spine withgraphenized polyacrylonitrile (PAN) through a gradual carbonizing route. This nanocomposite strongly interacts with Simaterial, providing a robust nanoarchitecture with abundant conductive pathways for Li-ion transport. CMC and PAA with alarge number of carboxyl groups provide binding ability by sturdy three-dimensional (3D) cross-linked network with relativelya thin SiO2 mechanical binding film on the surface of Si nanoparticles onto a highly porous carbon and forming a stablesolid electrolyte interface (SEI) layer. Meanwhile, graphenized PAN provides a highly interconnected conductivenanoarchitecture of a nitrogen-doped graphenized-like structure (NG), which provides enhanced pathways for lithium iondiffusion. Without any conductive additives, this nanocomposite material not only shows a high superior 1st dischargecapacity of 3473 mAh g-1, high initial Coulombic efficiency of 89%, excellent rate capability, and remarkable cycling life formore 600 cycles when cycled at high current density of 3000 mA g-1, but also maintaining good cyclability with a constanthigh areal capacity of ~ 2.7 mAh cm-2. Together with the ease of fabrication, this provides a promising avenue forcommercial LIBs. Figure 1

Designing Solid Electrolyte Interface for Stabilized Silicon Anode for Lithium-Ion Battery

The exploration for the next generation of anode materials in the lithium-ion batteries is a vital subject in energy storage field. Silicon (Si) stands out among all the candidate materials due to its high theoretical specific capacity (4200 mAh/g for Li4.4Si), high safety and low cost. However, one of the biggest issues causing rapid capacity fade of Si anode is the continuous breakage and reformation of SEI due to unstable electrode/electrolyte interphase. One effective way to address it is to use electrolyte additives as represented by vinylene carbonate (VC) and fluoroethylene carbonate (FEC). It is believed that the decomposition of FEC generates electrochemical stable LiF and elastomeric polymerizable vinylene carbonate radical. These decomposition products form a passive layer on Si surface, leading to improved electrochemical performance. However, it is hard to control the composition and structure of the SEI.We take a different approach attempting to solve the above issue. Organic functional groups are introduced on the surface of Si nanoparticles (SiNPs) via Pt-catalyzed hydrosilylation reaction. The surface group helps form more robust SEI thus boosts the electrochemical performance of silicon anode evidenced in both half- and full-cells. This method provides an efficient approach confronting the issues associated with SEI. Figure 1

Peculiarities of electronic structure and composition in ultrasound milled silicon nanowires

The combined X-ray absorption and emission spectroscopy approach was applied for the detailed electronic structure and composition studies of silicon nanoparticles produced by the ultrasound milling of heavily and lowly doped Si nanowires formed by metal-assisted wet chemical etching. The ultrasoft X-ray emission spectroscopy and synchrotron based X-ray absorption near edges structure spectroscopy techniques were utilize to study the valence and conduction bands electronic structure together with developed surface phase composition qualitative analysis. Our achieved results based on the implemented surface sensitive techniques strongly suggest that nanoparticles under studies show a significant presence of the silicon suboxides depending on the pre-nature of initial Si wafers. The controlled variation of the Si nanoparticles surface composition and electronic structure, including band gap engineering, can open a new prospective for a wide range Si-based nanostructures application including the integration of such structures with organic or biological systems.

Application of Si particles recycled from industrial waste for Si/rGO electrode composition for lithium rechargeable battery production

In this work, a facile synthesis method of silicon/reduced graphene oxide composite (SRC) for lithium ion battery (LIB) production using silicon particles recycled from photovoltaic industrial waste sludge is demonstrated. The surfactant assisted self-assembly is effective in synthesizing homogeneous SRC. The SRC from recycled Si presents a high initial capacity of 1480 mAh g−1 at a current density of 100 mA g−1 with stable capacity retention of 65% after 50 cycles at a current density of 200 mA g−1. The rate capability tests show prospective performances of 962 and 623 mAh g−1 at current density of 500 mA g−1 and 2 A g−1, respectively. The high rate capability is attributed to the direct connection of rGO nanosheets on the surface of Si nanoparticles (NPs). This facile surfactant assisted self-assembly synthesis presented in this study is an unprecedented verification of Si particle recycling from industrial waste for lithium rechargeable battery production.

Si nanoparticles veiled with ultrathin rGO film reduced directly by precoated Ni template: Fabrication and electrochemical performance

Si/graphene composite has been considered as a promising structure to limit the volume expansion and improve poor conductivity of silicon anode. Herein, a novel method to prepare Si/reduced graphene oxide (Si/rGO) composite anode was proposed. With this approach, nickel shell was pre-coated on Si particles via electroless deposition before used as a template to in-situ reduce GO. During the reduction process, the nickel template can as well promote the self-assembly of graphene sheets on the surface of Si nanoparticles. Following these facile and convenient processes, a Si/rGO hybrid-structure can be directly fabricated. Compared with pure Si anode, this Si/rGO composite displays a greatly improved electrochemical performance in both cycling stability and rate capability. It delivers a reversible capacity as high as 975 mA h g−1 and 717 mA h g−1 after 300 cycles under the current densities of 1 A g−1 and 3 A g−1, respectively. Meanwhile, its capacity can still maintain at 602 mA h g−1 even at a rather higher current of 5 A g−1.

Multi-modal anti-counterfeiting and encryption enabled through silicon-based materials featuring pH-responsive fluorescence and room-temperature phosphorescence

Optical silicon (Si)-based materials are highly attractive due to their widespread applications ranging from electronics to biomedicine. It is worth noting that while extensive efforts have been devoted to developing fluorescent Si-based structures, there currently exist no examples of Si-based materials featuring phosphorescence emission, severely limiting Si-based wide-ranging optical applications. To address this critical issue, we herein introduce a kind of Si-based material, in which metal-organic frameworks (MOFs) are in-situ growing on the surface of Si nanoparticles (SiNPs) assisted by microwave irradiation. Of particular significance, the resultant materials, i.e., MOFs-encapsulated SiNPs (MOFs@SiNPs) could exhibit pH-responsive fluorescence, whose maximum emission wavelength is red-shifted from 442 to 592 nm when the pH increases from 2 to 13. More importantly, distinct room-temperature phosphorescence (maximum emission wavelength: 505 nm) could be observed in this system, with long lifetime of 215 ms. Taking advantages of above-mentioned unique optical properties, the MOFs@SiNPs are further employed as high-quality anti-counterfeiting inks for advanced encryption. In comparison to conventional fluorescence anti-counterfeiting techniques (static fluorescence outputs are generally used, thus being easily duplicated and leading to counterfeiting risk), pH-responsive fluorescence and room-temperature phosphorescence of the resultant MOFs@SiNPs-based ink could offer advanced multi-modal security, which is therefore capable of realizing higher-level information security against counterfeiting.