Huge Volume Change Research Articles

Modifying SiO as a ternary composite anode material((SiOx/G/SnO2)@C) for Lithium battery with high Li-ion diffusion and lower volume expansion

The silicon suboxide (SiO) anode material is considered to be a promising anode material of Lithium-ion batteries (LIBs), because of its high theoretical capacity. However, there are severe problems for SiO, including the huge volume change (200%), the low electrical conductivity and the low first Coulombic efficiency. In order to solve those problems, a ternary composite ((SiOx/G/SnO2)@C) (G denotes graphite) with carbon coating layer is prepared by ball milling, spray drying and sintering. In the composite, graphite as one part of the active materials, can improve the Coulombic efficiency and control volume change of SiOx. To further restrain the high-volume change of SiOx, the carbon coating layer is designed. In particular, owing to the presence of SnO2, a better electrochemical performance for (SiOx/G/SnO2)@C is obtained. The results show that the first charging capacity of (SiOx/G/SnO2)@C can reach 382.6 mAh g−1 at current density of 100 mA g−1 and the Coulombic efficiency is improved from 62.2% to 74.9%. After 110 cycles, the charging capacity is 424.6 mAh g−1 and the capacity retention rate is 103.9%. In addition, after 90 cycles of rate performance test, (SiOx/G/SnO2)@C exhibited the highest capacity retention of 104.7%.

Manganese-based coordination framework derived manganese sulfide nanoparticles integrated with carbon sheets for application in supercapacitor

Manganese sulfide (MnS) with high specific capacitance and low-cost merits, has been investigated as a potential electroactive material for supercapacitor. However, in practical application, MnS has been suffering from some disadvantageous issues such as insufficient electrical conductivity, serious particle agglomeration as well as huge volume change during continuous charges and discharges, which resulted in a limited specific capacitance, shortened working life and inferior rate performance. Engineering electrode materials with controlled nanostructure and composition is pivotal to improve electrichemical performance of supercapacitors. This paper introduces a facile in situ sulfuration method to fabricate MnS/NSC composite with Mn-hexamethylene tetramine coordination framework as precursor. The results indicated that MnS nanoparticles were highly dispersed and incorporated into nitrogen, sulfur-doped carbon microsheets in MnS/NSC composite. Carbon matrix effectively dispersed and confined the MnS nanoparticles, thus inhibiting aggregation, relieving volume change and retaining structural integrity. Moreover, the 2D conductive carbon matrix reduced the diffusion distance for ions and ensured fast electron delivery. As a result, MnS/NSC electrode delivered a tremendously boosted electrochemical performance for supercapacitor. A large capacitance value about 1881.8F/g was achieved at 1A/g. Even cycling for 3000 loops at 40 A/g, MnS/NSC electrode retained a large capacitance of 404.3F/g. Furthermore, an asymmetric capacitor based on assembly of MnS/NSC composite cathode and activated carbon anode was fabricated. As tested under a current density of 0.1 A/g, it delivered a capacitance of ∼ 110.1F/g and achieved an energy density of 12.4 Wh kg−1 along with a power density of 3.03 kW kg−1. These results demonstrate the potential utilization of MnS/NSC composite as electrodes for energy conversion and storage devices and open up a route for material design for future energy storage devices.

On the magnetic-structure origin of giant magnetostrictive effect in MnCoSi-based metallic helimagnets

Giant magnetostrictive effect, the huge volume and/or shape change of a material under an external magnetic field, is recently discovered in helimagnets with large magnetoelastic interactions. Here we revisit this effect in MnCoSi, a helical metamagnet with a unique Lifshitz tricritical point. By introducing minimal amount of Ni, the modified competing exchange interaction simultaneously lowers the tricritical temperature and even critical field of metamagnetism, leading to a giant, reversible, low-field magnetostrictive effect at ambient temperature. When applying a cyclic low field of 0.5 T, a giant reversible magnetostriction of 550 ppm can be achieved and maintained at 300 K. Interestingly, by advanced 3D-vector magnetic field measurement, a strong relation is found between magnetocrystalline anisotropy and the critical field of magnetostrictive effect. In-situ neutron powder diffraction results further reveal that the incommensurate helical antiferromagnetic structure with moment lying in ab plane transits into a ferromagnetic structure along b axis with increasing magnetic fields. During this metamagnetic transition, dramatical spin rotation triggers sharp anisotropic lattice change via strong magnetoelastic coupling, resulting in giant magnetostrictive effect. The saturated magnetostriction value is closely related with the amplitude of spin rotations. These findings not only design of a potential MnCoSi-based magnetostrictive material but also uncover the specific evolution of magnetic structures in the metamagnetic transition and the possible mechanism behind the macroscopic size change.

Accommodation of Two-Dimensional SiOx in a Point-to-Plane Conductive Network Composed of Graphene and Nitrogen-Doped Carbon for Robust Lithium Storage.

Silicon oxides (SiOx) are one of the most promising anode materials for next-generation lithium-ion batteries owing to their abundant reserve and low lost and high reversible capacity. However, the practical application of SiOx is still hindered by their intrinsically low conductivity and huge volume change. In this regard, we design a novel anode material in which sheet-like SiOx nanosheets are encapsulated in a unique point-to-plane conductive network composed of graphene flakes and nitrogen-doped carbon spheres. This unique composite structure demonstrates high specific capacity (867.7 mAh g-1 at 0.1 A g-1), superior rate performance, and stable cycle life. The electrode delivers a superior reversible discharge capacity of 595.8 mAh g-1 after 200 cycles at 1.0 A g-1 and 287.5 mAh g-1 after 500 cycles at 5.0 A g-1. This work may shed light on the rational design of SiOx-based anode materials for next-generation high-performance lithium-ion batteries.

Carbon coated bimetallic sulfides Co9S8/ZnS heterostructures microrods as advanced anode materials for lithium ion batteries

Lithium ion batteries (LIBs) are widely used in portable electronic devices and hybrid vehicles because of their high energy density, long cycle life and environmental friendliness. Constructing bimetallic sulfide have been demonstrated as most promising strategy for prepare high performance anode materials for LIBs. However, the huge volume change resulting in poor cycle life during the change and discharge process was the key issue of transition metal sulfides. Here, bimetallic sulfide carbon micro-rods consist of Co9S8/ZnS core and outer carbon shell (Co9S8/ZnS@C MRs) is synthesized as anode materials for LIBs. Such a well-designed architecture have various advantages including the bimetallic sulfide Co9S8/ZnS heterostructures can generate built-in electric field, which boosting the ion and electron transfer at the interfaces between Co9S8 and ZnS. Moreover, the outer carbon layer can enhance the conductivity, and buffer the volume expansion of Co9S8/ZnS during the lithiation/delithiation process. As a result, combined with the merits of heterostructures and core-shell structure, the Co9S8/ZnS@C MRs exhibits outstanding electrochemical performance. Specifically, it can deliver a high capacity of 591.1 mAh g−1 after 1000 cycles at 1.0 A g−1, and maintain a capacity of 367 mAh g−1 even at 5.0 A g−1.

Oriented carbon fiber/PEO functional modified polyethylene separator for high-performance lithium metal batteries

The commercialization of lithium (Li) metal batteries is largely hindered by serious safety hazards resulting from dendrite growth and huge volume change of Li metal anode. Herein, we propose a multifunctional oriented polyimide carbon (OPIC) fiber, polyethylene oxide (PEO) modified layer coated commercial polyethylene (PE) separator by doctor-blade casting to guide homogeneous Li deposition. Therefore, the deposited Li morphology becomes more uniform and denser. Owing to the improvement of the Li metal anode side, Li||LiFeO4 full cells assembled with OPIC/PEO@PE separators delivered a discharge capacity of 102.5 mA h g−1 at 1.0C after 200cycles.

Constructing highly stable solid electrolyte interphase for Si@Graphene anodes by coupling 2-isocyanatoethyl methacrylate and fluoroethylene carbonate

Si-based anode materials have become the most popular candidate in next generation high-specific energy lithium-ions batteries owing to the advantages of high theoretical capacity, low operation potential, environmental friendliness, and low cost. However, the huge volume changes of Si-based anode during the charging and discharging process results in unstable solid electrolyte interphase (SEI) films and poor cycling performance. Here, 2-isocyanatoethyl methacrylate (IEM) and fluoroethylene carbonate (FEC) are used as functional electrolyte additives to constructing stable and durable inorganic-organic composite SEI films on the surface of Si@Graphene (Si/G) anode. The composite SEI film can tolerate the volume change of Si/G anode. As a result, the Si/G anode shows enhanced initial Coulombic efficiency (ICE), cycling stability and rate capability. Specifically, the ICE of Li||Si/G cell can reach 90%, and the specific capacity of Li||Si/G cell can maintain 1373 mAh g−1 after 100 cycles at the rate of 1 A g−1 by adding 1 vol% IEM and 9 vol% FEC.

Hyperbranched Polymer Network Based on Electrostatic Interaction for Anodes in Lithium-Ion Batteries.

Silicon is considered as one of the ideal anode materials for the new generation of lithium-ion batteries due to its extremely high theoretical specific capacity. Nevertheless, in the actual charging and discharging process, the Si electrode will lose its electrochemical performance due to the huge volume change of Si nanoparticles resulting in detachment from the surface of the fluid collector. The polymer binder can bond the Si nanoparticles together in a three-dimensional cross-linking network, which can thus effectively prevent the Si nanoparticles from falling off the surface of the fluid collector due to the drastic change of volume during the charging and discharging process. Therefore, this study developed a new polymer binder based on electrostatic interaction with hyperbranched polyethylenimine (HPEI) as the main body and water-soluble carboxylated polyethylene glycol (CPEG) as the cross-linker, where the degree of cross-linking can be easily optimized by adjusting the pH value. The results demonstrate that, when the density of positive and negative charges in the binder is relatively balanced at pH 7, the stability of the battery's charge-discharge cycle is significantly improved. After 200 cycles of constant current charge-discharge test, the specific capacity retention rate is 63.3%.

Lithiophilic and conductive framework of 2D MoN nanosheets enabling planar lithium plating for dendrite-free and minimum-volume-change lithium metal anodes

Lithium (Li) is a promising anode for high-energy rechargeable batteries but its practical implementation is impeded by uncontrollable dendrite growth and huge volume changes. Herein, we report a dendrite-free Li composite anode with minimum volume change, which is composed of 3D interpenetrating Li and lithiophilic MoN nanosheets prepared by mechanical rolling and folding. The conductive 2D MoN nanosheets boasting excellent lithiophilic affinity and small lattice mismatch with Li induce planar Li plating therefore suppressing dendrite growth along the perpendicular direction. The MoN nanosheets interwoven framwork provides abundant Li accommodation sites and the horizontally plated Li fills the nanoscale gaps between the MoN nanosheets, thus minimizing volume change during cycling. Li3N generated in situ by the surface reaction between MoN and Li enhances the ionic conductivity and interface stability. The Li-MoN anode shows a low Li plating overpotential of 15.0 mV and excellent stability for 2,500 h at 1 mA cm−2. Paired with the LiFePO4 cathode, the full cell shows 99.7 % Coulombic efficiency and 87.7 % capacity retention after 650 cycles at 170 mA g−1. The results provide insights into the design of 3D host enabling planar Li plating for dendrite-free and minimum-volume-change Li metal anodes.

Synergy of multi-means to improve SnO2 lithium storage performance achieved by one-pot solvothermal method

The high capacity and low operating potential made SnO2 very potential to be used as an anode material, but huge volume changes and poor conductivity defects hindered its practical application. Single improvement strategy had limited promotion on SnO2 lithium storage performance. Here, multi-strategy synergy effect of controlling the crystallinity to amorphous, reconstructing the band edge by Co, N co-doping and combining with graphene to enhance SnO2 electrochemical performances was achieved through a facile one-step solvothermal method. As-prepared cobalt and nitrogen co-doped amorphous SnO2/graphene composite ((Co, N)-a-SnO2/GR) possessed a high discharge specific capacity of 1694.4 mAh g−1 with an initial coulombic efficiency (ICE) of 70.1% at 0.5 A g−1, and good cyclic stability (1056.8 mAh g−1 after 400 cycles). The intrinsically isotropic and long-range disorder nature of the amorphous structure, the narrowing of the SnO2 bandgap caused by Co, N co-doping, and the introduction of graphene could synergistically improve the electrochemical performance of SnO2-based electrode. This kind of multi-ways synergy strategy also shed light on other similar anode materials.

Designing of reinforced two-dimensional molybdenum sulfoselenide microspheres by SnS quantum flakes with N-doped carbon for high performance half/full lithium-ion batteries

Though two-dimensional metal chalcogenides are a promising anode material for Li-ion batteries owing to their high theoretical capacity, they exhibit poor cycling stability and inferior rate performance due to their structural deterioration caused by huge volume change during the repeated cycling. Herein, we report extra-small tin sulfide quantum flakes with nitrogen-doped carbon over two-dimensional molybdenum sulfoselenide microspheres (SnS QFs/[email protected]) to improve the lithium ion-storage capability. The exclusive design of SnS QFs/[email protected] endows the heterostructure with the large surface area, improves charge storage kinetics, maintains robust structural stability and exaggerates ion storage ability. An initial discharge capacity of 962 mAh g−1 is obtained at 100 mAg−1 with good cycling stability (1026 mAhg−1 after 100 cycles) and superior rate capability (628 mAhg−1 at 2000 mA g−1). The full cell with SnS QFs/[email protected] anode and LiNi0.8Co0.1Mn0.1O2 cathode exhibits good cycling performance with a capacity retention of 90.0% after 300 cycles at 0.5 C rate. Our work provides the feasible design of anchoring/infusing quantum-sized active materials into the various two-dimensional structures for the development of high-performance anode materials for advanced Li-ion batteries.

Phenolic resin-derived carbon-confined strategy: Sb2Se3@C@CNTs-600 with ultra-high pseudocapacitive contribution as a superior lithium-ion battery anode

With the advantage of high capacity, Sb2Se3 is one of the potential anodes for lithium-ion batteries. Unfortunately, due to the effects of the poor electronic conductivity and the huge volume changes associated with Sb2Se3, the application of Sb2Se3 in lithium-ion batteries is severely limited. Herein, we designed a composite that Sb2Se3 nanoparticles were encapsulated by phenolic resin-derived carbon at a high temperature. The material (Sb2Se3@C@CNTs-600) has excellent lithium storage properties due to the synergy between the Sb2Se3 and carbon matrix. The intricate conductive structure guaranteed Sb2Se3@C@CNTs-600 excellent electrochemical properties with a reversible capacity of 580 mAh g−1 after 900 cycles at a current density of 1 A g−1. Additionally, the Sb2Se3@C@CNTs-600 electrode exhibits a fantastic rate capability delivering a reversible capacity of 440.5 mAh g−1 on average at 5 A g−1. Furthermore, benefit from the rational structural design, it delivers an ultra-high pseudocapacitive contribution of 93.93% at 1 mV s−1. The results proved that the phenolic resin-derived carbon can effectively mitigate the volume expansion of Sb2Se3 during the lithiation and delithiation processes, ensuing the cycling stability of the Sb2Se3@C@CNTs-600 and enhancing the lithium storage property and rate performance of the Sb2Se3@C@CNTs-600.

High-Performance All-Solid-State Li-S Batteries Enabled by Reaction Kinetics Enhancement and Interface Stabilization

Compared to the conventional lithium-sulfur (Li-S) batteries using liquid electrolytes, all-solid-state lithium-sulfur batteries (ASSLSBs) own the merits of eliminating polysulfide shuttle effects, potentially higher energy density, and superior safety. However, there are challenges of low utilization of sulfur caused by poor ion and electron conductions in the cathode, huge interfacial resistance due to the contact loss caused by huge volume change of sulfur during cycling, and sluggish reaction kinetics and higher thermodynamic barriers because of the one-step reaction from S8 to Li2S reactions. Also, the carbon additive could accelerate the decomposition of sulfide solid-state electrolyte (SSE) resulting newborn impedance. Therefore, it is significant to interface engineering the carbon additive through surface modification and functionalization to improve the electrochemical stability, charge transfer, and reaction kinetics in ASSLSBs.Herein, for the first time, we designed a highly conductive carbon fiber decorated with vertically grown MoS2 nanosheets and applied it in ASSLSBs. The chemical and electrochemical compatibility among MoS2, sulfur, and sulfide SSE can greatly improve the stability of the cathode and therefore maintain pristine interfaces between the different compositions for stable ion and electron transport. The presence of electrical-conductive metallic 1T MoS2 and its uniform distribution on carbon fiber without aggregation benefit the electron transfer between carbon and sulfur. Meanwhile, the unique layered structure of MoS2 can be intercalated by a large amount of Li atoms and therefore facilitate both ionic and electronic conductivity. In consequence, the charge transfer and reaction kinetics were greatly enhanced, and the decomposition of SSEs was successfully relieved. As a result, our ASSLSB delivered an ultrahigh initial discharge capacity of 1456 mAh g-1 with ultrahigh initial coulombic efficiency and maintained high-capacity retention of 78 % at 0.1 C after 220 cycles. The batteries also obtained remarkable rate performance of 1069 mAh g-1 at 1 C. This study pioneered new idea that fabricating the high performance ASSLSBs through developing surface functionalized and stabilized conductive carbon additives with metal sulfides.

Analysis of Mechanical Properties and Electrochemical Behavior of Li-Ion Secondary Batteries According to Particle Size of Silicon Anode

Li-ion secondary batteries have been applied to various electronic devices since Sony released a lithium secondary battery using hard carbon as an anode in 1991. The market for large secondary batteries is gradually expanding and moving forward. And although high energy density, cyclability, and stability are required for use in various applications at this time, the currently commercialized graphite anode is facing the limit of theoretical capacity (LiC6, 372 mAh/g).While research on next-generation anode materials is underway to increase the energy density of lithium secondary batteries, silicon has a high theoretical capacity close to 4000 mAh/g, attracting attention as an anode for next-generation lithium-ion batteries. However, the capacity retention rate is low due to the huge volume change and low electrical conductivity that occur during charging and discharging of silicon.In order to solve this problem, many studies are being conducted, such as a) making a silicon-sized structure into a nano-scale and porous structure, b) oxidizing silicon, and c) a composite with a carbon material. Among them, much attention has been paid to improving the electrochemical performance of a silicon-based anode by designing a structure by fabricating silicon in a nano size. Compared to conventional silicon materials, nano-sized silicon was able to better withstand the stress caused by volume expansion during charging/discharging in the nano-surface-to-volume ratio. As a result, intergranular cracking can be limited, thereby improving cycle stability and maintaining high capacity. The particles can shorten the diffusion path of lithium by providing a stable electron and Li-ion transport path, and can provide increased rate-limiting properties and reduced resistance.In this study, the effect of the manufactured silicon grain size on the mechanical and electrochemical properties of the Li-ion secondary battery was studied by various analytical methods.

Constructing three-dimensional N-doped carbon coating silicon/iron silicide nanoparticles cross-linked by carbon nanotubes as advanced anode materials for lithium-ion batteries

Silicon (Si), have been considered as promising anode material for lithium-ion batteries (LIBs), due to its high theoretical specific capacity of 4200 mAh g−1. However, the poor electrical conductivity and large volume change during lithiation/delithiation process, resulting in poor cycling stability, and seriously hindered the practical application in LIBs. Herein, a multiple Si/FexSiy@NC/CNTs composite is synthesized and investigated as advanced anode materials for LIBs via a simple one-step method. Such multiple Si/FexSiy@NC/CNTs composite has several merits including the FexSiy can not only accommodate the huge volume change of Si nanoparticles, but also enhance the conductivity upon discharge/charge process. Furthermore, the in-situ growth CNTs may help establish a long-range conductivity, and the Nitrogen-doped carbon (NC) layer can further improve the conductivity of Si, as well as inhibit the direct contract between electrolyte and Si during cycling process. Accordingly, the Si/FexSiy@NC/CNTs-1 exhibits excellent cycling stability (a high capacity of 994.4 mAh g−1 is maintained at 1.0 A g−1 after 600cycles) and outstanding rate capability (a suitable capacity of 441.7 mAh g−1 was obtained even at 5.0 A g−1). Moreover, the assembled full cell can achieve a capacity of 141.4 mAh g−1 after 65 cycles at 1.0C, exhibiting outstanding cycling stability. This work provides a prospective way for the commercial production of high-performance Si-based anode materials for LIBs.

Amorphous carbon nanofibers incorporated with ultrafine GeO2 nanoparticles for enhanced lithium storage performance

As a potential anode material with high theoretical specific capacity, the practical application of GeO 2 is largely hindered by huge volume change and low reactivity, Herein, we proposed the engineering of dual amorphous GeO 2 @C nanofibers via facile electrospinning and thermal annealing process. In this design, numerous ultrafine GeO 2 particles are evenly anchored in carbon nanofibers, which could relief the stress in the carbon material during the lithium/delithiation process. Moreover, the low binding energy of Ge-O bond in the dual amorphous GeO 2 /C nanofibers render for convenient charge transfer. As a result, the electrode delivers highly reversible conversion (GeO 2 + 4Li ↔ Ge + 2Li 2 O) and alloying (Ge + 4.4Li ↔ GeLi 4.4 ) reaction. Furthermore, the GeO 2 @C nanofibers with large specific surface area also supply more active sites for pseudocapacitive lithium storage. Benefitting from the typical structure, the dual amorphous GeO 2 @C nanofibers electrode exhibits high reversible capacity of 1053 mAh g −1 at 0.3 A g −1 after 1000 cycle, and superior rate capacity of 476 mAh g −1 at 5 A g −1 . The excellent electrochemical performance endows dual amorphous GeO 2 @C nanofibers competitive electrode material for next-generation lithium-ion batteries. • Dual amorphous GeO 2 @C nanofibers were prepared by a facile and efficient approach. • Dual amorphous GeO 2 @C nanofibers display outstanding lithium storage properties. • Dual amorphous structure benefits for superior lithium storage.

In-situ growth flower-like binder-free 3D CuO/Cu2O-CTAB with tunable interlayer spacing for high performance lithium storage

Copper-based oxides are attractive anode materials for lithium-ion batteries (LIBs) due to their abundant resources, low cost, non-toxic and high capacity. However, copper-based oxides will produce a huge volume change during lithiation/delithiation, and the structural strain caused by periodic volume changes may cause the exfoliation of active materials. Herein, a flower-like binder-free three-dimensional (3D) CuO/Cu2O-CTAB was prepared by introducing CTAB, which homogeneously grew in situ on a copper mesh framework. The binder-free 3D sample guarantees direct contact between the active material and the copper mesh, maintaining the structure stability. The flower-like CuO/Cu2O-CTAB with a small size reveals larger active interfaces and provides more active sites. The introduction of CTAB enlarges the interlayer spacing of CuO/Cu2O, increases the active sites for lithium storage, and adapts to the volume change of the material during lithiation/delithiation. In addition, the expanded interlayer structure helps decrease the ion diffusion energy barrier for accelerating electrochemical reaction kinetics. Therefore, CuO/Cu2O-CTAB exhibits better lithium storage performance (2.9 mAh cm−2 at 0.5 mA cm−2) than bare CuO/Cu2O (1.8 mAh cm−2 at 0.5 mA cm−2).

Space-confined synthesis of a novel Ge@HCS-rGO yolk-shell nanostructure as anode materials for enhanced lithium storage

Germanium (Ge) is considered as a promising anode material due to its high lithium storage capability. However, the huge volume change during cycling cause serious structural degradation and poor cycling stability. Yolk-shell nanostructure design is an effective way to solve such problems for electrode materials such as Ge and Si. Herein, we proposed the design and synthesis of a novel Ge@hollow carbon sphere-reduced graphene oxide (Ge@HCS-rGO) yolk-shell nanostructure as anode via a space-confined strategy for the first time. Rational void space is engineered in the yolk-shell structure, offering a buffer zone for adapting the volume expansion of Ge core particles with protective carbon shells upon lithiation, while the 3D conductive network with hierarchical pores provides fast electron and Li-ion transport channels. Benefiting from the unique structural dual-protection of 3D conductive network and yolk-shell nanostructure, the as-synthesized Ge@HCS-rGO anode exhibits high discharge capacity (2117.3 mA h g−1 at 0.2 C), enhanced cycling stability (958.6 mA h g−1 up to 200 cycles at 0.2 C) and excellent rate capability (1010.0 mA h g−1 at 4 C). The electrochemical performance of Ge@HCS-rGO yolk-shell anode is greatly improved compared with bare Ge and Ge@HCS anode, suggesting its great potential to develop high performance electrode materials with large volume expansion.

Cu3Si-Modified Silicon Nanoparticles Encapsulated within SiOx and Hollow Carbon for Lithium-Ion Battery Anodes

Silicon (Si), a promising anode material for lithium-ion batteries, usually suffers from low capacity retention and poor rate performance due to its huge volume change issue and low electronic conductivity. The synergistic effect brought by the composite of carbon, metal silicide, and silicon is proven to be an effective measure to enhance the performance of silicon-based anodes. Herein, Cu3Si-modified silicon nanoparticles (SiNPs) encapsulated within SiOx and hollow carbon shell (M-Si@H-C) are designed and constructed by an electroless deposition and pyrolysis process, which delivers high specific capacity (1150 mAh g–1 at 0.21 A g–1 and 450 mAh g–1 at 8.4 A g–1) and long cycling stability (86.3% capacity retention after 200 cycles at 1 A g–1). The nanostructure and formation mechanism of the M-Si@H-C is elucidated by employing X-ray diffraction and transmission electron microscopy techniques. The enhancement to the lithium storage performance of the nanostructure is clarified on the basis of the microstructure investigation and electrochemical determination.

Preparation of SiC-Coated Silicon Nanofiber/Graphite Composites as Anode Material for Li-Ion Batteries by the Chemical Vapor Deposition Method

Abstract Si material has huge lithium storage capacity, but its huge volume changes during charging and discharging making it difficult to use. However, by using nano-sizing Si material and building a coating structure can effectively reduce the capacity reduction caused by the expansion of the Si material. In our experiment, dichlorodimethylsilane was used as the silicon source and carbon source for the deposition of silicon nanofibers and SiC-coated on a spherical graphite substrate, and then the SiC cladding was deposited without changing the temperature and silicon source, and only the C to H ratio in the atmosphere was controlled to build the cladding layer. In our experiment, silicon nanofibers were deposited on graphite surfaces using dichlorodimethylsilane as the silicon source, followed by SiC cladding on the surface of the Si/G composites using dichlorodimethylsilane as the silicon source and carbon source. The end product was controlled by controlling only the C to H ratio in the atmosphere at the same temperature. The preparation of SiC@Si/G composites with silicon nanofibers and cladding structures by a single CVD process and single raw materials. The material has a silicon nanofiber structure and SiC coating structure. The presence of silicon is effective in providing very high capacity and the presence of the SiC layer is effective in improving the capacity retention of the composite material for increasing the Coulomb efficiency of the material. At a current density of 100 mA h g−1, the material has a reversible capacity of 647.3 mA h g−1 at the first cycle. After 100 cycles, it has a 76.2% retention rate. The electrodes can be extremely stable after cycling without significant swelling.