Silicon-carbon Composites Research Articles

Designer Cathode Additive for Stable Interphases on High-Energy Anodes.

Rechargeable lithium-based batteries built with high-energy anode materials (e.g., silicon-based and silicon-derivative materials) are considered a feasible solution to satisfy the stringent requirements imposed by emerging markets, including electric vehicles and grid storage, due to their higher energy density compared to contemporary lithium-ion batteries. The robustness of the solid electrolyte interphase (SEI) layer on high-energy anodes is critical to achieve long-term and stable cycling performances of the batteries. Herein, we propose a new type of designer cathode additive (DCA), i.e., an ultrathin coating layer of elemental sulfur on the cathode, for the in situ formation of a thin and robust SEI layer on various types of high-energy anodes. The DCA elemental sulfur undergoes simultaneous oxidation and reduction paths, forming lithium alkyl sulfate (R-OSO2OLi) and poly(ethylene oxide) (PEO)-like polymers on the anode surface. The as-formed R-OSO2OLi/PEO-modified SEI layer has good lithium cation (Li+) permeability to facilitate fast ion transportation across the interphases and superior elasticity to adapt to large volume changes, which is particularly effective for improving the cycling efficiency of high-energy anodes (e.g., ca. 14-35% increase in capacity retention for the silicon-carbon composite (SiC) or silicon-tin alloy (Si-Sn)||LiFePO4 cells). The present work opens a new avenue toward the practical deployment of high-energy rechargeable lithium-based batteries.

High Rate Performance Flake Si/C Composite Anode Materials of Lithium-Ion Batteries by Oxidization of an Industrial Si–Ca Alloy with CaCO3 in Molten Salt

High rate performance silicon/carbon composite anode materials are popular with lithium-ion batteries. Herein, a flaky silicon–carbon composite (FSCC) anode material with a high rate performance and its facile synthesis are investigated. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectra analyses show that the FSCC comprises flaky crystal Si embedded with or combined with amorphous carbon and a few and uniformly distributed crystal FeSi2. Benefiting from the special structure, the FSCC and especially the ball-milled FSCC exhibit a superior rate performance. Its rate capacity of ∼865 mA h g–1 at 2000 mA g–1 is 82.9% of that at 200 mA g–1. The synthesized method of oxidization of an industrial Si–Ca alloy with CaCO3 in molten CaCl2–NaCl at 600 °C for 1 h and the removal of salt with washing are simple, fast, and friendly to the environment, which shows great prospect for application in practice.

A promising silicon/carbon xerogel composite for high-rate and high-capacity lithium-ion batteries

Silicon-based anodes are widely studied as an alternative to graphite anodes for lithium-ion batteries. Nevertheless, their practical application is mainly limited by the huge volume change that silicon particles undergo due to alloying and de-alloying with lithium ions during discharge/charge processes, which result in cracks and electrode degradation. In the present study, porous silicon-carbon composites are investigated as anode materials for next-generation lithium-ion batteries. These composites are prepared by a cost-effective, easily-scalable method based on a microwave assisted approach for the carbon matrix, followed by dispersion of the silicon in 2-propanol. The electrochemical behavior of the Si/C composites with different proportions of silicon is evaluated in terms of alloying and de-alloying mechanisms of lithium ions, battery reversible capacity, irreversible capacity in the first cycle, retention of capacity along cycling, and cycle efficiency. The composite with 30 wt.% of silicon presents specific discharge capacity as high as 917 mAh g−1 after 200 cycles and excellent stability in the long-term at high current density, which makes it a promising candidate for the lithium-ion battery market.

Strategies for Controlling or Releasing the Influence Due to the Volume Expansion of Silicon inside Si-C Composite Anode for High-Performance Lithium-Ion Batteries.

Currently, silicon is considered among the foremost promising anode materials, due to its high capacity, abundant reserves, environmental friendliness, and low working potential. However, the huge volume changes in silicon anode materials can pulverize the material particles and result in the shedding of active materials and the continual rupturing of the solid electrolyte interface film, leading to a short cycle life and rapid capacity decay. Therefore, the practical application of silicon anode materials is hindered. However, carbon recombination may remedy this defect. In silicon/carbon composite anode materials, silicon provides ultra-high capacity, and carbon is used as a buffer, to relieve the volume expansion of silicon; thus, increasing the use of silicon-based anode materials. To ensure the future utilization of silicon as an anode material in lithium-ion batteries, this review considers the dampening effect on the volume expansion of silicon particles by the formation of carbon layers, cavities, and chemical bonds. Silicon-carbon composites are classified herein as coated core-shell structure, hollow core-shell structure, porous structure, and embedded structure. The above structures can adequately accommodate the Si volume expansion, buffer the mechanical stress, and ameliorate the interface/surface stability, with the potential for performance enhancement. Finally, a perspective on future studies on Si−C anodes is suggested. In the future, the rational design of high-capacity Si−C anodes for better lithium-ion batteries will narrow the gap between theoretical research and practical applications.

Synthesis of porous Si–C composite powder from activated raw materials

A porous silicon-carbon composite was synthesized using a mixture of sucrose, ammonium chloride, and silicon in a neutral gas environment at 1000 °C. Effect of raw materials activation were studied (0, ‌ 1, 2, and 4 h) on the characteristics (microstructure, morphology, phase structure, carbon structure, and electrical resistance) of prepared composite powders using SEM (Scanning Electron Microscope), XRD (X-Ray Diffraction), RAMAN spectroscopy methods, and electrical resistivity measurements. Results showed that mechanical activation promoted the decomposition reaction of raw materials during heat treatment, helped to form spherical carbon particles, reduced carbon particle size (less than 200 nm), and facilitated the formation of the porous carbon structure. Raman spectra also showed the appearance of some carbon in the milled samples before the heat treatment process. Carbon peaks were not observed in the XRD patterns of composite powders due to the nanocrystalline structure of the carbon, while Raman spectra proved the presence of nanocrystalline and amorphous carbon in the structure of the prepared powders. Moreover, mechanical activation increased the content of nanocrystalline and amorphous carbon in the composite powders. Increasing the mechanical activation time up to 4 h, reduced the electrical resistivity of Si–C composite powders to 1.44 Ω-cm.

Porous core-shell B-doped silicon–carbon composites as electrode materials for lithium ion capacitors

Development of anode materials of high capacities, rate capability, and cycling stability is critical for lithium ion capacitors (LICs). Composite electrode design, combining advantages of constituent component materials, is a promising approach for the purpose. Porous core-shell B-doped silicon-carbon spheres, B–Si@1RFC, of small sizes (150 nm) and high specific capacities are successfully synthesized with a one-pot method, followed by carbonization, magnesiothermic reduction, and B-doping, to be composited with reduced graphene oxide (rGO) porous structure of excellent structural and electrical properties to serve as an outstanding anode material, B–Si@1RFC/rGO, for LICs. The LIC, assembled by coupling the B–Si@1RFC/rGO anode with a glucose-derived carbon nanosphere cathode of ultrahigh specific surface areas (1947 cm2 g−1) and pore volumes (2.04 cm3 g−1), delivers a high energy density of 149 Wh kg−1 at a power density of 0.328 kW kg−1 and maintains a decent energy density of 82.1 kW kg−1 at a high power density of 49.3 kW kg−1, together with an excellent cycling stability of retaining 74.4% of the initial energy density after 10,000 cycle operations at 5 A g−1.

Durable silicon-carbon composites self-assembled from double-protected heterostructure for lithium-ion batteries

HypothesisSilicon-carbon composites have been faced with the contact issues between silicon and carbon in the form of material aggregation and inferior dispersion, leading to electrode cracking or kinetic degradation during cycling. In addition to dispersion improvement from interfacial linkage between self-assembled Si nanoparticles (SiNPs) and carbon fibers (CNFs), the positive influences of high-content carboxymethyl cellulose(CMC) (25 wt%) and amorphous carbon are also expected, respectively after the second-step self-assembly and subsequently sintering. ExperimentsA novel composite (i.e. Si-CNF@C) with the decoration of entire SiNPs in the framework of both CNFs and amorphous carbon was prepared via two-step electrostatic self-assembly followed by sintering. Such a composite with heterogeneous nanostructure was used as a lithium-ion battery anode without additional binders or conductive agents. FindingsSiNPs can be well protected with CNFs and amorphous carbon against the dispersion and contact problems under both effects of electrostatic attraction and chemical bonding. With the double-protected heterostructure, such a novel Si-CNF@C electrode exhibits highly reversible capacities of 1200 mAh g−1, 982 mAh g−1, and 849 mAh g−1 after 100, 500, and 1000 cycles at 0.5 A g−1, respectively. The long-term cycling stability with a capacity loss of 0.036% per cycle over 1000 cycles is comparable.

High-Value Utilization of Silicon Scraps and Excrementum Bombycis to Synthesize Silicon-Carbon Composites as Anode Materials for Li-Ion Batteries

High-Value Utilization of Silicon Scraps and Excrementum Bombycis to Synthesize Silicon-Carbon Composites as Anode Materials for Li-Ion Batteries

One-step synthesis of interface-coupled Si@SiOX@C from whole rice-husks for high-performance lithium storage

As the world transitions towards an electric vehicle-driven future, demand for energy storage materials has continued to grow. Silicon-carbon composites are considered one of the most promising anode materials for lithium-ion batteries owing to their superior electrochemical performance. However, their commercialization is seriously limited due to the use of chemical reagents as carbon source, unstable coating structures and the complexity of the synthesis process. Herein, a facile one-step carbonization method at 800 °C was used to prepare Si@SiOX@C-800 composite by using rice husks, 1‑butyl‑3-methylimidazolium acetate (BMIMAcO) and silicon nanoparticles (Si-NPs). When the optimized Si@SiOx@C-800 was applied to the anode of lithium-ion batteries, it exhibited prominent reversible capacity (694 mAh g−1 at 0.1 A g−1), with remarkable rate performance (220 mAh g−1 at 2 A g−1), and excellent cyclic stability (460 mAh g−1 with a capacity retention of 105.7% at 1 A g−1 after 1000 cycles). The coupling of interfaces by Si-N bonds led to the formation of a double-layered structure which enhanced Li+ diffusion coefficients and electrochemical kinetics, while tremendously limiting the volume variation of Si nanoparticles (Si NPs). The double-shell-structured Si@SiOX@C-800 composite material which was facilely synthesized using an eco-friendly approach presented superior electrochemical performance.

Design of ultrafine silicon structure for lithium battery and research progress of silicon-carbon composite negative electrode materials

As demand for high-performance electric vehicles, portable electronic equipment, and energy storage devices increases rapidly, the development of lithium-ion batteries with higher specific capacity and rate performance has become more and more urgent. As the main body of lithium storage, negative electrode materials have become the key to improving the performance of lithium batteries. The high specific capacity and low lithium insertion potential of silicon materials make them the best choice to replace traditional graphite negative electrodes. Pure silicon negative electrodes have huge volume expansion effects and SEI membranes (solid electrolyte interface) are easily damaged. Therefore, researchers have improved the performance of negative electrode materials through silicon-carbon composites. This article introduces the current design ideas of ultra-fine silicon structure for lithium batteries and the method of compounding with carbon materials, and reviews the research progress of the performance of silicon-carbon composite negative electrode materials. Ultra-fine silicon materials include disorderly dispersed ultra-fine silicon particles such as porous structures, hollow structures, and core-shell structures; and ordered ultra-fine silicon, such as silicon nanowire arrays, silicon nanotube arrays, and interconnected silicon nano-films. The article analyzes and compares the composite method of ultrafine silicon and carbon materials with different structural designs, and the effect of composite negative electrode materials on the specific capacity and cycle performance of the battery. Finally, the research direction of silicon-carbon composite negative electrode materials is prospected.

Fluorine-functionalized core-shell Si@C anode for a high-energy lithium-ion full battery

To illuminate the effect of F on a carbon coating and the surface modification process of the bulk, a fluorine functionalized core-shell silicon-carbon composite (Si@C) is prepared by a high-temperature pyrolysis process using PVDF and nano-Si as raw materials. By using PVDF, simultaneous modification of the core-shell silicon-carbon composite is realized, and a good theoretical model is established for the electrochemical behavior after fluorine modification, especially the surface and interfacial reaction of the Si-based anode. When the Si@C composite is used as an anode material in a lithium-ion battery, it delivers a reversible capacity of 683 mAh/g at 200 mA/g and a capacity retention of 67% after 50 cycles. A high-energy lithium-ion full battery configured from the Si@C anode and commercial LiNi0.6Co0.2Mn0.2O2 (Si@C||LiNi0.6Co0.2Mn0.2O2) delivers an energy density that reaches 335.1 Wh/kg (vs. the cathode), making it a bright prospect for the regulation and control of interfacial/surface reactions in Si-based energy storage systems.

High stability of sub-micro-sized silicon/carbon composites using recycling Silicon waste for lithium-ion battery anode

Abstract Silicon-carbon composite is recognized as one of the most promising anodes for high-energy lithium-ion batteries. In this work, a kind of sub-micro-sized silicon (Si) recycled from solar cell industrial cutting waste has been explored as lithium-ion battery anode through a simple compound process. Coated and bound by chitosan pyrolyzed hard carbon, the Si particles (most) were distributed in graphite particles in a balanced way to form silicon-graphite-carbon (SCG) composite. Hence, as-prepared SCG anode delivers a stable cycling performance, with a reversable capacity of 741 mAh g−1 at 100 mA g−1 after 400 cycles and retention of 98.8%. In addition, that the slower electrolyte penetration phenomenon for chitosan derived hard carbon anode plus SCG anode has been found, should and can be modified by pre-activation. The better stability as well as higher rate capability (587 mAh g−1 at 400 mA g−1) of SCG anode proved that the strategy of hard carbon as a glue while graphite as main frame structure works on making up defects of sub-micron Si. The remarkable cycling performances and low-cost manufacturing process make Si particles of larger size also show important commercial application values.

Optimal microstructural design of pitch-derived soft carbon shell in yolk-shell silicon/carbon composite for superior lithium storage

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.

Rapid iodine capture from radioactive wastewater by green and low-cost biomass waste derived porous silicon-carbon composite.

The effective and safe capture and storage of radioactive iodine (129I or 131I) are of significant importance during nuclear waste storage and nuclear energy generation. Herein, a porous silicon–carbon (pSi–C) composite derived from paper mill sludge (PMS) is synthesized and used for rapid iodine capture. The influences of the activator type, the impregnation ratio of the paper mill sludge to the activator, carbonization temperature, and carbonization time on the properties of the pSi–C composite are investigated. The pSi–C composite produced in the presence of ZnCl2 as the activator and at an impregnation ratio of 1 : 1, a carbonization temperature of 550 °C, and a carbonization time of 90 min has a surface area of 762.13 m2 g−1. The as-synthesized pSi–C composite exhibits promising iodine capture performance in terms of superior iodine adsorption capacity (qt) of around 250 mg g−1 and rapid equilibrium adsorption with in 15 min. The devised method is environmentally friendly and inexpensive and can easily be employed for the large-scale production of porous silicon-activated carbon composites with excellent iodine capture and storage from iodine-contaminated water.

Electrochemical scissoring of disordered silicon-carbon composites for high-performance lithium storage

Practically adapted physical integration of silicon and carbon predominates as a viable solution to realize high energy density batteries, however, the composite structure is vulnerable to fracture. Here we report a molecular-level mixed silicon-carbon composite anode through thermal pyrolysis of silane and subsequent mechanical mill, entailed by electrochemical dissociation and reclustering of such disordered silicon-carbon bonds during the cycles. Lithium insertion induces heterolytic fission of the bonds into sub-nanometre silicon particles segregated by redox-active carbon framework validated by microscopy analysis and reactive molecular dynamics simulation. The embedded structure with a high packing density of silicon prevents detrimental electrochemical coalescence and direct contact to a liquid electrolyte to stabilize the interfaces, while three-dimensional (3D) carbon framework buffers large volume expansion of silicon to enable an extended full battery cycling.

Biological enzyme treatment of starch-based lithium-ion battery silicon-carbon composite

Silicon/carbon composites have the disadvantages of large volume expansion and high cost, which limits their commercial application. In this study, green and economic starch was used to prepare porous starch (PS) under the action of enzymes, and then nano-silica was embedded in the PS. A PS based carbon/silicon/carbon composite was prepared by coating and carbonizing the starch slurry, which can alleviate the volume expansion of silicon. The results show that the anode composite material with 20% silicon content has a high initial capacity of 869 mAh g−1 and an initial Coulombic efficiency of 66% at 0.2 A g−1, and the specific capacity is maintained 450 mAh g−1 after 100 cycles. When the silicon content reaches 30%, the reversible capacity of the composite is 1490 mAh g−1 at a current density of 0.2 A g−1, and the capacity remains 850 mAh g−1 after 100 cycles. Its excellent properties and stability are attributed to the abundant porosity of the carbon in the starch derived layer, which improves the structural stability and electrochemical kinetics. This method provides a reference for the sustainable and environmental protection of lithium-ion battery anode materials.

A strategy and detailed explanations to the composites of Si/MWCNTs for lithium storage

Nano-Si/MWCNTs composite was a representative solution to improve Si-based anode material’s rate performance in lithium-ion batteries (LIBs). However, the problems of easy agglomeration of silicon nanoparticles and carbon nanotubes hindered Si/MWCNT’s further development. In this study, we combine silicon nanoparticles with MWCNTs cleverly by utilizing freeze-drying method to solve the problems and enhance silicon-based material’s rate performance. Compared with Si-MWCNTs composite treated by electric blast-drying method, the rate performance of Si-MWCNTs treated by freeze-drying is significantly improved, especially at different current densities. When Si-MWCNTs are encapsulated in FPC (flour-derived porous carbon, FPC), the as-obtained Si-MWCNTs-PVPC-FPC-SC-1 (sucrose-derived carbon, SC) prepared by freeze-drying method delivers a reversible capacity of 1347.5 mAh g−1 at 0.1 A g−1 after cycling at 5 A g−1 and a reversible capacity of 501 mAh g−1 at 1 A g−1 after 500 cycles. Our study demonstrates that the freeze-drying method can solve the problems of easy agglomeration of silicon nanoparticles and MWCNTs as well as improve Si-based anode’s rate performance for LIBs. The synthetic route presented in this paper is low-cost and easy to scale up for silicon-carbon (Si/C) composites with high rate performance and long cycle life.

3D graphene-like nanosheets/silicon wrapped by catalytic graphite as a superior lithium storage anode

Silicon–carbon composites, which exhibit the advantages of both carbon and silicon materials, are regarded as the most promising anode for lithium ion battery. In this work, a composite of 3D graphene-like nanosheets/silicon wrapped by catalytic graphite (G-3DGNs-Si) was prepared via a chemical oxidation–thermal expansion strategy and high-temperature sintering method. The obvious interlinked 3D-layered spaces in 3DGNs arranged orderly can uniformly accommodate silicon nanoparticles (SiNPs). 3DGNs can relieve the volume expansion and improve the electrical conductivity of SiNPs. In addition, the catalytic graphite evenly coated on the 3DGNs-Si can further improve electrochemical performance. The G-3DGNs-Si composite anode can achieve 90% reversible capacity retention (957.2 mAh g−1) at 0.2 A g−1 after 100 cycles (78.9% after 300 cycles). The method is effective and easy to operate. This work provides a novel idea for designing silicon–carbon composites.

A Commercial Carbonaceous Anode with a-Si Layers by Plasma Enhanced Chemical Vapor Deposition for Lithium Ion Batteries

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.

The pitch-based silicon-carbon composites fabricated by electrospraying technique as the anode material of lithium ion battery

Silicon is regarded as one of the most promising anode materials for high performance lithium-ion battery (LIB) due to its high theoretical specific capacity. However, the low electrical conductivity and the severe volume change during charging and discharging process result in poor cyclic performance. In this study, a low cost, high-purity silicon powder from the sawing waste in photovoltaic industry was used as the active material. Pitch from petroleum residue was used as carbon source to provide a good conductive pathway and prevent the drastic volume changes of Si. The pitch-based silicon-carbon composites with a porous structure were fabricated by electrospraying technique followed by a sequence of thermal processes. The results of the charge/discharge showed that the 100th charge capacity of 1515 mAh/g at 0.2 C with the retention of 73.95% while the 200th charge capacity of 929 mAh/g at 0.5 C with the retention of 70.61% (Pitch-Si-0.5) can be obtained. On the other hand, the sample with medium content of Si showed charge capacity of 522 mAh/g at 0.5 C with the extremely high retention of 94.99% after 200 cycles. The rate capability indicated that the soft carbon derived from pitch provided a good rate capability because of its amorphous structure. We demonstrated that industrial wastes can form a superior anode material for LIB application.