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The electrochemical properties of an electrode material based on a high-capacity silicon/reduced graphene oxide composite are studied. It was determined that the optimal potentials for reversible insertion/extraction of lithium are in the range of 50–2000 mV. The discharge capacity is 980 mAh g–1 at the charge rate 0.3 C and discharge rate 1.0 C. The addition of vinylene carbonate to the electrolyte solution leads to the stabilization of the solid electrolyte layer on the electrode surface. The discharge capacity is 866 mAh g–1 at the 170th charge/discharge cycle. [ABSTRACT FROM AUTHOR]

Recently, the application of energy storage systems and electric vehicles has increased the importance of lithium-ion batteries (LIBs). However, despite their rising significance, the ability to increase their capacity through power generation of the anode is limited. In this study, we developed an LIB anode material made of silicon (Si) nanoparticle-embedded carbon-nanofiber web film (SNE-CWF) that showed excellent cycling performance when low current activation was performed. Further, we examined the electrochemical properties of SNE-CWF electrodes fabricated through our process as anodes in LIB. The capacity of Si embedded carbon nanofiber showed high specific capacity at 1001–1557 mAh/g at low current density of 20 mA/g than carbon nanofiber (initial capacity of 604 mAh/g). After activation with low current density, the 5 wt% SNE-CWF electrode provided a capacity of 870 mAh/g even when the current was increased to 200 mA/g, and capacity retention at 20th cycle was 92.7%, showing the most stable performance out of all the materials tested. Hence, the stability of performance in LIB was enhanced. The low current electrochemical activation method of SNE-CWF presented through this experiment is expected to suggest a new approach for the manufacture of next-generation electrode material for LIBs. [ABSTRACT FROM AUTHOR]

Silicon-based photovoltaic technology is helpful in reducing the cost of power generation; however, it suffers from economic losses and environmental pollution caused by silicon cutting waste. Herein, a hydrothermal method accompanied by heat treatment is proposed to take full advantage of the photovoltaic silicon cutting waste and biomass excrementum bombycis to fabricate flake-like porous Si@C (FP-Si@C) composite anodes for lithium-ion batteries (LIBs). The resulting FP-Si@C composite with a meso-macroporous structure can buffer the severe volume changes and facilitate electrolyte penetration. Meanwhile, the slightly graphitic carbon with high electrical conductivity and mechanical strength tightly surrounds the Si nanoflakes, which not only contributes to the ion/electron transport but also maintains the electrode structural integrity during the repeated lithiation/delithiation process. Accordingly, the synergistic effect of the unique structure of FP-Si@C composite contributes to a high discharge specific capacity of 1322 mAh g−1 at 0.1 A g−1, superior cycle stability with a capacity retention of 70.8% after 100 cycles, and excellent rate performance with a reversible capacity of 406 mAh g−1 at 1.0 A g−1. This work provides an easy and cost-effective approach to achieving the high-value application of photovoltaic silicon cutting waste, as well as obtaining high-performance Si-based anodes for LIBs. [ABSTRACT FROM AUTHOR]

The structural characteristics of litchi shell-derived carbon are conducive to regulation and modification. Using biomass waste litchi shells as carbon source and nano-silicon particles to prepare silicon-carbon composite materials to relieve the volume effect of silicon in the charge and discharge process, litchi shell-derived activated carbon (LAC) with high specific surface area (1011.115 m2 g−1) and high porosity was obtained from litchi shell as silicon buffer matrix by simple high-temperature calcination and activation of ZnCl2. A silicon-carbon composite material (3D LAC@Si) with an embedded cladding structure was prepared with a high-energy ball milling process. In the electrochemical performance test, 3D LAC@Si as the negative electrode of a lithium-ion battery showed a high lithium storage capacity of 834.4 mAh g−1 and a high coulombic efficiency of 98.34% after cycling 100 cycles at a current density of 0.2A g−1. [ABSTRACT FROM AUTHOR]

The severe volumetric changes occur during the lithiation/de-lithiation of silicon materials, which are the main cause of battery capacity failure. In this study, the expansion behavior of a cell composed of a silicon-carbon anode and Li(Ni 0.5 Co 0.2 Mn 0.3)O 2 (NCM523) was measured using the electrochemical dilatometry, and the contributions of different silicon and carbon components to the expansion were analyzed, along with factors affecting the cyclic stability of the silicon carbon anode. The results indicate that amorphous carbon can inhibit the volume expansion of monocrystalline silicon in the late stage of lithiation, thereby ensuring the cyclic stability of silicon. The cyclic stability of silicon-carbon composites is affected by irreversible expansion and expansion variation, and these two factors are negatively correlated. This research provides insights and guidance for the design of silicon carbon electrodes with superior electrochemical performance. • The impact of silicon-carbon components on cycle stability. • The depth of lithiation influences the expansion of the anode. • Amorphous carbon can effectively inhibit the expansion of silicon anode. • The change in expansion is negatively correlated with irreversible expansion. [ABSTRACT FROM AUTHOR]

In this study, we propose a mass production-able and low-cost method to fabricate the anodes of Li-ion battery. Carbonaceous anodes, integrated with thin amorphous silicon layers by plasma enhanced chemical vapor deposition, can improve the performance of specific capacity and coulombic efficiency for Li-ion battery. Three different thicknesses of a-Si layers (320, 640, and 960 nm), less than 0.1 wt% of anode electrode, were deposited on carbonaceous electrodes at low temperature 200◦C. Around 30 mg of a-Si by plasma enhanced chemical vapor deposition (PECVD) can improve the specific capacity ~42%, and keep coulombic efficiency of the half Li-ion cells higher than 85% after first cycle charge-discharge test. For the thirty cyclic performance and rate capability, capacitance retention can maintain above 96%. The thicker a-Si layers on carbon anodes, the better electrochemical performance of anodes with silicon-carbon composites we get. The traditional carbonaceous electrodes can be deposited a-Si layers easily by plasma enhanced chemical vapor deposition, which is a method with high potential for industrialization. [ABSTRACT FROM AUTHOR]

Silicon-based anode materials have numerous advantages, including abundant reserves, high specific capacity, and environmental friendliness, which is an important direction for the development of anode materials in the future. However, the volume of silicon changes significantly during the processes of lithiation and de-lithiation, which limit its widespread use. In this study, silicon-carbon composites were prepared by using a high-temperature pyrolysis method. Among them, silicon was used as an active material, and phenolic resin served as the carbon source. Si@C showed better cycling stability and reversibility in constant current cycling tests compared silicon and graphite directly composites. Furthermore, according to the results of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), the addition of amorphous carbon can effectively reduce the electrode damage caused by volume expansion and the shrinkage of silicon materials, which has a positive effect on the stability of SEI. Additionally, the high conductivity of amorphous carbon improves the electrochemical kinetics of the battery during cycling, thereby enhancing the performance of silicon anodes. [ABSTRACT FROM AUTHOR]

Influence exerted by the temperature of annealing in the atmosphere of argon on the ability of Si‒C nanocomposites to enable a reversible introduction of lithium has been studied. It was found that the higher the annealing temperature in the formation of a composite, the lower the capacity of the electrode fabricated from this composite. X-ray diffraction analysis and scanning electron microscopy demonstrated that the capacity decreases because silicon carbide of cubic modification β-SiC inactive toward formation of lithium alloys or intercalates is formed at T ≥ 1100°C. [ABSTRACT FROM AUTHOR]

A novel method to fabricate porous silicon–carbon nanocomposites has been suggested. The method uses carbon monofluoride reduction by silicon. The produced composite materials are formed by silicon nanoparticles confined into a carbon shell. The contacts of these particles provide current flowing across the formed carbon matrix. The dependences of density, porosity, and resistivity on the composition of Si–C composite pellets obtained by the suggested method have been determined. The studied materials are of interest for developing negative electrodes for lithium-ion batteries with high capacity. [ABSTRACT FROM AUTHOR]

Silicon-carbon composites are considered as the most promising anode materials for lithium ion batteries. Currently, most silicon-carbon composites were prepared by solid nano‑silicon particles as the silicon source, which suffers from high price and uneven dispersion. Here, we used tetraethyl orthosilicate as the liquid silicon source and polyvinylpyrrolidone as the carbon source. Both were homogeneously mixed in the liquid phase, and then processed through electrospinning, carbonization and nitrogen-doped processes to obtain free-standing nitrogen-doped carbon coated silicon monoxide (N-doped C/SiO x). When served as anode material, N-doped C/SiO x can possess a reversible capacity of 488 mAh g −1 at 0.5 C (0.6 A g −1) and 377 mAh g −1 at a high current density of 2 C (2.4 A g −1). In addition, copper foil is not used as a collector for free-standing electrode structure, and eliminates the coating process of traditional electrodes, which reduces production costs. It is proposed that a facile strategy to fabricate silicon-carbon composites with good electrochemical properties and cost-effective way for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Silicon/mesoporous carbon (Si/MC) composites with optimum Si content, in which the volumetric energy density would be maximized, while volume changes would be minimized, have been developed. The composites were prepared by dispersing Si nanoparticles in a phenolic resin as a carbon source, subsequent carbonization, and etching with hydrofluoric acid (HF). Special attention was paid to understanding the role of HF etching as post-treatment to provide additional void spaces in the composites. The etching process was shown to reduce the SiO2 native layer on the Si nanoparticles, resulting in increased porosity in comparison to the non-etched composite material. For cell optimization, vinylene carbonate (VC) was employed as an electrolyte additive to build a stable solid electrolyte interphase (SEI) layer on the electrode. The composition of the SEI layer on Si/MC electrodes, cycled with and without VC-containing electrolytes for several cycles, was then comprehensively investigated by using ex-situ XPS. The SEI layers on the electrodes working with VC-containing electrolyte were more stable than those in configurations without VC; this explains why our sample with VC exhibits lower irreversible capacity losses after several cycles. The optimized Si/MC composites exhibit a reversible capacity of ~800 mAhg−1 with an average coulombic efficiency of ~99 % over 400 cycles at C/10.

The studies of fundamentally new electrochemical systems for lithium-ion batteries of new generation, which were performed at the Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, are briefly reviewed. The results of investigation of lithium insertion into negative electrodes based on silicon and silicon-carbon composites and operation of positive electrodes of nano-structured materials based on vanadium oxides are described. [ABSTRACT FROM AUTHOR]

Silicon/carbon (Si/C) composites have become the mainstream anodes for silicon-based lithium-ion batteries (LIBs) with outstanding stability and high capacity, in which carbon can significantly stabilize the silicon anodes. Currently, most Si/C composites use nano‑silicon as raw materials, which suffer from low energy density, high price and preparation complexity. Here, we have developed a silicon-graphite‑carbon ternary composite (Si-G-C-15) with cheap micron-sized silicon as raw materials. It was prepared by ball-milling of micron silicon and graphite and subsequent carbonization of PAN, followed by NaOH selective etching. Electrochemical test results demonstrate that Si-G-C-15 can possess a reversible capacity of 965 mAh/g at 200 mA/g, with a capacity retention of 71.34% and 786 mAh/g at a high current density of 1 A/g after 100 cycles. Notably, this facile preparation process of silicon anodes with high rates and good capacity stability highlights the potential practical application. [Display omitted] • A facile routine is developed to fabricate silicon-graphite-carbon ternary composite. • Silicon anode using micro-sized silicon is low-cost and has high energy density. • NaOH etching method is powerful to improve electrode cycling stability and rate capability. [ABSTRACT FROM AUTHOR]

• The facile and cost-effective preparation process of yolk-shell Si/C composites and modification methods with high scalability. • The designed pore channel structures endowing the optimal lithium storage capacity and volume change tolerance. • The high crystallinity ensures the outstanding electronic conductivity and robust carbon shell. • The optimal Si/C composite with a well matching microstructure of carbon shell exhibits excellent cycling performance and rate capacity (55% retention at 300th cycle, 743 mAh g−1 at 2 A g−1). • Correlation between microstructural feature (crystallinity and pores) of the carbon shell and the electrochemical behaviors of the Si/C electrodes is established. Silicon-carbon composites have proved to be effective in addressing the issues of silicon anodes, however, few works focus on understanding the effect of the microstructure of the carbon component on their electrochemical performance. Herein, we prepare a series of yolk-shell structured silicon-carbon nanocomposites with adequate voids through a facile and scalable process. By deliberately selecting the pitch species and delicately adjusting the heat treatment temperature, the microcrystal texture and pore structure of the soft carbon can be easily tuned. Finally, a well matching of the crystalline and pore structure ensure the rapid charge transport and the good structural robustness, further endowing the optimal lithium storage, cycle performance and rate capability of the electrodes. The Si/C composite with an optimized carbon shell delivers a reliable cycle stability with a capacity retention ratio of 55% after 300 cycles at 0.2 A g−1 and a remained capacity of 743 mAh g−1 at a high current density of 2.0 A g−1. Importantly, the correlation between the lithium storage of the Si/C composites and the microstructure features (crystallinity and pores) of the carbon shell has been established, which may provide an effective guidance for optimizing the microstructure design of the promising Si/C anode materials. We established the relationship between designed microstructural feature (crystallinity and pores) of the carbon shell and corresponding electrochemical performance of the Si/C anodes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

It is suggested to form porous silicon-carbon nanocomposites via thermal reduction of carbon monofluoride by silicon. For this purpose a mixture of powders of nanocrystalline silicon and fluorocarbon is subjected to cold compaction and the resulting pellets are annealed in an inert atmosphere at T = 800 °C. The density, porosity, structure, composition, and electrical resistivity of thus produced Si–C materials have been studied in detail in relation to the content of the monofluoride in the starting mixture. It was shown that the materials obtained have a hierarchical porous structure constituted by silicon nanoparticles in a shell of finely dispersed carbon. The shells contacting with each other form a carbon matrix providing a high electrical conductivity of the material. The composite was used to fabricate negative electrodes of lithium-ion batteries with increased storage capacity. The electrochemical characteristics of Si–C nanocomposite anodes of varied composition were analyzed and those with high carbon content demonstrated the best performance. • New simple method to form porous silicon-carbon nanocomposites is proposed. • Properties of thus produced Si-C materials have been studied in relation to the content of CF x in the starting mixture. • The material consists of silicon nanoparticles in a carbon shell, which provides high electrical conductivity. • The composite was tested as anode material for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Silicon can be used in a variety of applications. Particularly, silicon particles are attracting increased attention as energy storage materials for lithium-ion batteries. However, silicon has a limited cycling performance owing to its peeling from the current collector and the volume expansion that occurs during alloying with lithium in the charging process. Significant contributors to this problem are the even distribution of silicon nanoparticles within the carbon matrix and their deep placement in the internal structure. In this study, we synthesized silicon nanoparticles and carbon materials via a bottom-up approach using a new method called plasma in solution. Silicon nanoparticles and the carbon matrix were synthesized in a structure similar to carbon black. It was confirmed that the silicon particles were evenly distributed in the carbon matrix. In addition, the evaluation of the electrochemical performance of the silicon–carbon matrix (Si–C) composite material showed that it exhibited stable cycling performance with high reversible capacity. [ABSTRACT FROM AUTHOR]