Silicon-based Anode Materials Research Articles

Effect of silicone segment and imidization of polyimide-based binder on the electrochemical performances of high silicon content anode for lithium-ion batteries

Binders are expected to play important role in silicon-based anode materials, but have not been well explored. In this work, a serial of silicon containing polyimides and polyamides have been synthesized and used as the binder of high content (80wt%) silicon anode. Systematic characterizations have been done on the chemical structures, physical properties of the binders, and the electrochemical performances of silicon-based anode. It was found that the swelling ratio, adhesion strength, and hardness plays important roles on the initial Coulombic efficiency (ICE) and capacity retention of silicon-based anode, and these parameters highly depend on the types and properties of binders. After optimizing the chemical structures and physical properties of the binders, a high specific capacity of 2941 mAh g−1, relatively high initial Coulombic efficiency (ICE) of 83%, and good capacity retention of 85% (after 200 cycles) have been obtained. These results would help researchers to design new types of binders for silicon-based anode to improve its ICE and capacity stability.

Carbon coating optimization on porous silicon as high-performance anode material via fluidized bed chemical vapor deposition

The carbon layer coating is a promising solution to volume expansion and low electron conductivity in silicon-based anodes during lithiation. While numerous methods exist to generate these carbon coatings, Fluidized Bed Chemical Vapor Deposition (FBCVD) has proven superior due to its capacity for producing remarkably uniform and consistent carbon layers, primarily as a result of efficient mass and heat transfer characteristics. However, its application in the context of lithium-ion battery anodes has been sparsely explored and has been principally limited to silicon oxide as the base material. In this paper, porous silicon (PSi) obtained through acid etching of AlSi alloy with an average particle size of 300 mesh was taken as raw materials, and a fluidized bed reactor was employed to realize a uniform and tightly packed carbon layer. Relatively speaking, the PSi@C30 in this work offers a simpler process and promising electrochemical performance, opening a new door for the preparation of high-performance silicon-carbon anodes by FBCVD. Besides, PSi and high-quality carbon layers with structural advantages enabled the authors to obtain high-performance silicon-carbon anode materials. The resulting PSi@C30 composite demonstrated excellent initial coulomb efficiency (88.8 %) and cycling stability (with 83 % capacity retention after 100 cycles at 0.5 A g-1 and a reversible capacity of 1408 mAh g-1). Such a cost-effective and user-friendly technique facilitates the application of FBCVD in silicon-based anode materials for Li-ion batteries, thus accelerating the industrialization of silicon-carbon anodes for high-performance Li-ion batteries in the future.

Si@C Core–Shell Nanostructure-Based Anode for Li-Ion Transport

Silicon-based anode materials are gaining popularity in lithium-ion battery research due to their high theoretical specific capacity compared to the conventional graphite anode. However, the commercialization of silicon-based anode materials has been hampered by their limited electronic conductivity and significant volume expansion. To address these challenges, our strategy was conducted to prepare porous silicon@carbon (p-Si@C) nanocomposites as an anode material using a simple aqueous solution method. In this work, nitrogen-containing p-phenylenediamine was chosen as the carbon source for synthesizing the nanostructured p-Si@C composites. The excellent electrochemical performance can be achieved, with over 100 cycles, a specific capacity of 624 mAh g–1, and a high Coulombic efficiency of 97.2%. These promising results were attributed to efficient Li-ion transport and low volume expansion, which are confirmed by the distribution function of relaxation time plots coupled with impedance spectroscopy technique, followed by the calculation of the expansion rate obtained from the SEM cross-sectional image. Hence, our work not only clearly provides a simple yet valuable method for the preparation of nanostructured silicon-based anode material with good electrochemical performance but also demonstrates its potential for industrial battery-grade development.

Nanostructure and doping effects of a-Si:H and μc-Si:H anode in lithium-ion battery performance

The charge/discharge capacity and cycle performance of lithium-ion batteries (LIBs) are studied in terms of the nanostructure of silicon-based anode materials and doping. The anode material is chosen to be either hydrogenated amorphous silicon (a-Si:H) or hydrogenated microcrystalline silicon (μc-Si:H), in which the doping is controlled between non-doped intrinsic i-type and phosphorous-doped n-type. The results show that a LIB test cell composed of a n-type a-Si:H anode yields a higher performance. The specific capacity during discharge is obtained initially at 2478 mAh/g, 1940 mAh/g after 10 cycles, and 1360 mAh/g after 40 cycles under a 0.2C condition.

Effect of Li–Si composites on electrochemical properties of silicon-based anode materials

Metal silicides are considered promising candidates for the replacement of graphite due to their larger capacity than graphite used in Li-ion batteries. In this work, a type of lithium silicide composite material consisting of LixSi, graphite (G), and porous carbon (PC) together with carbon coating treatment, denoted as (LS-G-PC)@C, was prepared by high-energy ball milling and subsequent pitch pyrolysis. This type of material is used as a pre-lithiation additive to improve the initial Coulombic efficiency (ICE) of Si-based anodes. The microstructural characteristic of (LS-G-PC)@C composite material was analyzed by x-ray diffraction and scanning electron microscopy. The electrochemical properties were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and capacity cycling tests. It has been found that the irregular particles of LS compounds are uniformly dispersed on the graphite sheet, which constitutes an effective conductive network together with PC. The addition of a 5 wt. % (LS-G-PC)@C pre-lithiation additive makes the ICE of a low ICE silicon-based composite material increase by 16%. At a current density of 100 mA g−1, the discharge capacity retention rate of the silicon-based composite increased from 86.1% to 91% after the 19th cycle, showing good cycle stability. Further work is to add higher levels of our pre-lithiation additive in order to improve the ICE significantly.

Silicon Anode: A Perspective on Fast Charging Lithium-Ion Battery

Power sources supported by lithium-ion battery (LIB) technology has been considered to be the most suitable for public and military use. Battery quality is always a critical issue since electric engines and portable devices use power-consuming algorithms for security. For the practical use of LIBs in public applications, low heat generation, and fast charging are essential requirements, but those features are still unsatisfactory so far. In particular, the slow Li+ intercalation kinetics, lithium plating, and self-heat generation of conventional graphite-anode LIBs under fast-charging conditions are impediments to the use of these batteries by the public demands. The use of silicon-based anodes, which are associated with fast reaction kinetics and rapid Li+ diffusion, has great potential to render LIBs suitable for public use in the near future. In this perspective, the challenges in and future directions for developing silicon-based anode materials for realizing LIBs with fast-charging capability are highlighted.

TiO2-Coated Silicon Nanoparticle Core-Shell Structure for High-Capacity Lithium-Ion Battery Anode Materials

Silicon-based anode materials are considered one of the highly promising anode materials due to their high theoretical energy density; however, problems such as volume effects and solid electrolyte interface film (SEI) instability limit the practical applications. Herein, silicon nanoparticles (SiNPs) are used as the nucleus and anatase titanium dioxide (TiO2) is used as the buffer layer to form a core-shell structure to adapt to the volume change of the silicon-based material and improve the overall interfacial stability of the electrode. In addition, silver nanowires (AgNWs) doping makes it possible to form a conductive network structure to improve the conductivity of the material. We used the core-shell structure SiNPs@TiO2/AgNWs composite as an anode material for high-efficiency Li-ion batteries. Compared with the pure SiNPs electrode, the SiNPs@TiO2/AgNWs electrode exhibits excellent electrochemical performance with a first discharge specific capacity of 3524.2 mAh·g-1 at a current density of 400 mA·g-1, which provides a new idea for the preparation of silicon-based anode materials for high-performance lithium-ion batteries.

Low-temperature electrolytes based on linear carboxylic ester co-solvents for SiO x /graphite composite anodes.

Silicon-based anode materials have been applied in lithium-ion batteries with high energy density. However, developing electrolytes that can meet the specific requirements of these batteries at low temperatures still remains a challenge. Herein, we report the effect of linear carboxylic ester ethyl propionate (EP), as the co-solvent in a carbonate-based electrolyte, on SiO x /graphite (SiOC) composite anodes. Using electrolytes with EP, the anode provides better electrochemical performance at both low temperatures and ambient temperature, showing a capacity of 680.31 mA h g-1 at -50 °C and 0.1C (63.66% retention relative to that at 25 °C), and a capacity retention of 97.02% after 100 cycles at 25 °C and 0.5C. Within the EP-containing electrolyte, SiOC‖LiCoO2 full cells also exhibit superior cycling stability at -20 °C for 200 cycles. These substantial improvements of the EP co-solvent at low temperatures are probably due to its involvement to form a solid electrolyte interphase with high integrity and facile transport kinetics in electrochemical processes.

A carbon-covered silicon material modified by phytic acid with 3D conductive network as anode for lithium-ion batteries

The requirement for silicon-based anode material is growing and has received attentions. Silicon is a promising anode material for lithium-ion batteries due to the high theoretical capacity. However, the high volumetric variability of silicon has led to severe chalking and rapid capacity degradation. To ameliorate these problems, a carbon-covered silicon material with a 3D conductive network structure was prepared employing glucose and phytic acid as carbon sources. When acted as the anode for Lithium-ion batteries, the prepared composite material delivered 1612 mAh/g in the first cycle and approximately 600 mAh/g at 0.1 A/g after 200 cycles. In addition, even at 5 A/g, a high capacity of 503 mAh/g was reached, and when recovered to 0.1 A/g, the capacity of 878 mAh/g was maintained.

Core-shell structured Si@Cu3Si-Cu nanoparticles coated by N-doped carbon as an enhanced capacity and high-rate anode for lithium-ion batteries

• Both Cu 3 Si and NC of Si@Cu 3 Si-Cu@NC are formed during the carbonization of dopamine. • Core-double shell structured Si@Cu3Si-Cu@NC nanoparticles can effectively enhance the stability of Si-based anode. • Si@Cu3Si-Cu@NC nanoparticles shows a high performance (1105.5 mAh g -1 ) under 5A g -1 as LIB anode. Silicon based anode material is regarded as a promising candidate for Lithium ionic batteries (LIBs) due to its high theoretical specific capacity. Nevertheless, the capacity degradation triggered by high volume expansion has seriously hindered its application in LIBs. Herein, a novel structure of core-shell structured Si@Cu 3 Si-Cu nanoparticles coated by N-doped carbon (Si@Cu 3 Si-Cu@NC) is designed and synthesized via a two-step thermal reduction process. In this design, the copper shell and N-doped carbon can significantly limit and accommodate the volume change of Si during cycling. The in-situ formation of Cu 3 Si at the interface further improves the structural stability. The doping of N in carbon is conducive to the rapid transmission of electrons and ions as well as optimizes the electrochemical performance of the material. Therefore, the optimized Si@Cu 3 Si-Cu@NC nanocomposite anode shows prominent rate performance and delivers a reversible capacity of 1105.5 mAh g -1 after 100 cycles at a high current density of 5 A g -1 , which exhibits the great potential of the nanocomposite as high-performance LIBs anode material.

The silicon-based anode in lithium-ion battery

Lithium-ion batteries are now widely used in our society. Developing advanced anode material to improve the property of Lithium-ion batteries has aroused more and more attention in recent years. The silicon-based material is one of the most popular materials for the anode owning to the unique advantages of theoretically high capacity, low operating point, rich material resources, and environmental friendliness. However, the decay of capacity fading during the cycling resulting from huge volume change and poor conductivity of this kind of anode material significantly limited the applications. Thus, novel strategies need to be developed urgent. For this scope, the silicon-based components with different materials and structures have been developed. Here we summarized a series of silicon-based components, involving in oxide composite materials, silicon/metal oxide composite materials, Si/Carbon nanotubes composite materials, and graphene composite material, from the aspects of the preparation process, microstructure, and performance of these silicon-based anode materials.

Low-Dimensional Nanostructures for Silicon-Based Anode Materials in Lithium-Ion Batteries

Electricity is becoming more important as an alternative energy replacing fossil fuels, as it can be obtained from solar, tide, and wind while being mostly harmless to the environment. The lithium-ion battery (LIB) has high potential in this regard. The silicon-based anode of LIB is a strong performer among different designs of LIBs and entered into service due to high specific energy and low operation potential. However, volume expansion during charging is a pressing problem. Low dimensional nanomaterials possess high specific surface area and special micro-mechanical properties, which can mitigate this problem effectively. This article focuses on cutting-edge nanoscale research from three-dimensionality angles, including 0D, 1D and 2D. For 0D, the core-shell structure is discussed, and modified structures based on the core-shell structure are introduced with a brief discussion on the preparation and structural features. For 2D anodes, silicon-based thin-film materials offer better stability and higher specific capacity. The preparation method of magnetron sputtering is discussed, and p-type doped SiOx/Si/SiOx sandwich LIB anodes are also introduced.

Porous silicon covalently-grafted with chloro-styrenic carbons for fast Li+ diffusion and durable lithium-storage capability

Silicon-based anode materials have critical issues such as drastic volume changes, huge stress generation, and the thickening of solid‒electrolyte interphase layer. Thus, a new strategy for improving silicon interface is necessary for significantly enhanced Li+ ion transportation and structural stability during prolonged cycling, while simultaneously reducing severe side reactions. Herein, we prepared porous silicon particles covalently linked with styrene-based polymers (polystyrene (PS) and poly(4-chlorostyrene) (PCS)) via a facile non-atmospheric thermolytic process at a low-temperature (≤400 °C), in which the decomposed styrenic carbon fragments are covalently grafted on the silicon surface via Si–O–C and Si–C species. Notably, PCS-grafted porous silicon exhibited the significantly enhanced electrochemical performance (i.e., a high rate capability of 1270 mAh g−1 at 20 A g−1, 90.7% of initial capacity at 4 A g−1, and a reversible capacity of 1725 mAh g−1 after 200 cycles), because of the dual covalent linkages of Si–C and Si–O–C species in chloro-styrenic carbons that provide durable lithium storage capability and fast Li+ transportation. Specifically, the Si–C linkage enforced the formation of a durable interlayer that protects the Si active material from reactive electrolytes, and the polarized Si–O–C linkage facilitates the rapid transport of Li+ ions.

Si nanoparticles confined in N, P- doped double carbon as efficient anode materials for lithium ion batteries

To tackle mechanical structure instability and low conductivity of silicon-based anode materials, Si nanoparticles enclosed in N, P doped double carbon (N, P-Si/CNTs/C) are designed and manufactured by simple mechanical ball milling and high-temperature carbonization methods. The mechanical action makes carbon nanotubes (CNTs) and silicon particles evenly and tightly intertwined, and a uniform and stable pitch-derived carbon layer is formed on the surfaces of Si particles and CNTs. The N, P-Si/CNTs/C composites have strong oxidation resistance, excellent electrical conductivity and more defects. N, P-Si/CNTs/C composites exhibit positive lithium storage performance as anode materials for lithium-ion batteries. The initial discharge/charge specific capacities of N, P-Si/CNTs/C electrodes are 1494.0/1243.6 mA h g−1 at 0.2 A g−1 with an initial coulombic efficiency of 83.24 %, yet it maintains 603.9 mA h g−1 after 100 cycles with the initial coulombic efficiency of 83.24 %. The specific discharge capacity is 1153.6 mA h g−1 even at 0.5 A g−1. The efficient lithium storage performance is due to the three-dimensional double-carbon network to effectively protect Si nanoparticles from oxidation, increase cycle stability and rate capability, and buffer volume expansion of Si nanoparticles. Doping with N and P can provide a lot of active sites and help the electrolyte penetrate.

High-Temperature Magnesiothermic Reduction Enables HF-Free Synthesis of Porous Silicon with Enhanced Performance as Lithium-Ion Battery Anode.

Porous silicon-based anode materials have gained much interest because the porous structure can effectively accommodate volume changes and release mechanical stress, leading to improved cycling performance. Magnesiothermic reduction has emerged as an effective way to convert silica into porous silicon with a good electrochemical performance. However, corrosive HF etching is normally a mandatory step to improve the electrochemical performance of the as-synthesized silicon, which significantly increases the safety risk. This has become one of the major issues that impedes practical application of the magnesiothermic reduction synthesis of the porous silicon anode. Here, a facile HF-free method is reported to synthesize macro-/mesoporous silicon with good cyclic and rate performance by simply increasing the reduction temperature from 700 °C to 800 °C and 900 °C. The mechanism for the structure change resulting from the increased temperature is elaborated. A finite element simulation indicated that the 3D continuous structure formed by the magnesiothermic reduction at 800 °C and 900 °C could undertake the mechanical stress effectively and was responsible for an improved cyclic stability compared to the silicon synthesized at 700 °C.

(Invited) 3D Electrode Architectures for High Power and High Energy Lithium-Ion Battery Operation - Recent Approaches and Process Upscaling

During the next decades, combustion driven cars will be completely replaced by electrical vehicles (EVs) and it seems quite obvious that liquid electrolyte lithium-ion batteries (LIBs) will be the dominating energy storage system for the next at least 5 to 10 years. As a consequence, in Europe numerous Gigafactories have recently been planned with this state of technology. However, the current lithium-ion battery technology suffers so far from some restrictions like the inability to combine high power and high energy operations at the same time. This limitation is mainly attributed to the cathode architecture and respective mass loading. In addition, the further demand for a significantly enhanced fast charging mainly requires an optimization of the anode design flanked by a high areal capacity. Advanced 3D electrode architectures based on a thick film electrode concept seem to be the most promising approach to overcome the current limitations in battery performances. However, respective technology innovations need to provide a high compatibility grade to existing manufacturing routes in order to enable the required integration in existing and planned factories. For so-called “generation 3” materials, i.e., nickel-rich lithium nickel manganese cobalt oxide (NMC) cathode and silicon-based anode materials, structuring technologies using cutting edge ultrafast high power lasers, are being developed in order to manufacture 3D electrode architectures with high areal capacity. Multibeam laser processing using diffractive optical elements and dual scanner approaches were established in order to enable high processing speeds in roll-to-roll electrode handling systems. The technology readiness level (TRL 6) is demonstrated for pouch cells geometries. For water-based NMC 622 and silicon-graphite composites the laser structuring process was developed. Different structures including hole, grid, and line patterns, were studied regarding their impact on electrochemical performances such as high-rate capability and cell lifetime. Lithium concentration profiles of unstructured and structured electrodes were studied post mortem using laser-induced breakdown spectroscopy (LIBS) in order to evaluate lithium intercalation/deintercalation efficiencies and detect possible cell degradation processes. In comparison to unstructured electrodes, 3D electrodes could hereby always be identified as superior: unstructured thick film electrodes show a significant drop in capacity retention for high power operation and tend to form hot spots acting as starting point for cell failure. The upscaling process is flanked by a further improvement of electrode design. For this purpose very recently laser induced forward transfer (LIFT) is applied as printing technology to draw new concepts for sophisticated model electrode architectures with advanced electrochemical performances. Finally, the micro-/nano-scaled texturing of current collectors and separator material is discussed as further possible approaches for boosting the electrochemical performances of LIB pouch cells.

In-situ processing nano-porous silicon into 3D conductive structure as high-capacity anode for lithium-ion batteries

The use of high-capacity materials in lithium-ion batteries (LIBs) is critical for achieving higher energy density. In this paper, a highly-dispersed three-dimensional (3D) graphene-wrapped porous nano-silicon composite (P-Si@rGO, where rGO is reduced graphene oxide) is synthesized from SiO2 and graphene oxide through a novel and facile approach that consists of freeze-drying and in-situ magnesium-thermal reduction. The composite is then utilized as a high-capacity anode for LIBs. A number of attractive properties are evident in this new silicon-based composite and include qualities such as individually encapsulated and highly dispersed silicon particles, close Si—O—C interactions between silicon and graphene, a porous design for the silicon structure, and a bulky porosity. These merits significantly enhance the reaction kinetics of the electrode and endow the composite with both a large electrical contact area and a sufficient buffer space to cope with the volume change during the lithiation/delithiation process. Ultimately, the P-Si@rGO sample demonstrates an excellent cycling stability, boasting a capacity of 1123 mAh g−1 at 1000 mA g−1 over 500 cycles. In this paper, materials with different morphologies are prepared by changing the magnesium-thermal reaction time, so as to study the effects of phase composition and microstructure of the composites on their electrochemical performances. Importantly, the reasons for the capacity increase seen in later stages of the cycling process are also investigated. In brief, these findings provide new insights into the future functional evolution of silicon-based anode materials.

Synthesis of micro-nano sphere structure silicon–carbon composite as anode material for lithium-ion batteries

Here, a new micro-nano sphere structure of silicon–carbon composite anode materials is fabricated using spray drying and surface modification. Fulvic acid (FA) is used as the carbon source, which forms voids between nanoscale silicon–carbon particles. The results demonstrate by rate performance that particle voids can significantly enhance the lithium-ion transport rate. The Si@FA-2 material offered a high capacity of 917.28 mAh g−1 after 100 cycles at a current density of 0.1 A g−1. Thus, fabricating a micro-nano sphere structure using FA as the carbon source offers a helpful exploration of silicon-based anode materials.

Synchrotron Holotomography on Silicon-Based Anode Materials for Improved Lithium Ion Batteries

Synchrotron Holotomography on Silicon-Based Anode Materials for Improved Lithium Ion Batteries

Yolk-shell-structured SiO2@N, P co-doped carbon spheres as highly stable anode materials for lithium ion batteries

Silicon-based materials have attracted great interest as potential candidates for graphite anodes owing to their extremely high specific capacity and low working potential. Nevertheless, the conventional application of silicon-based anode materials is seriously limited by their poor electrical conductivity and severe volume change. Herein, the development of high-performance anode materials for lithium ion batteries (LIBs) is demonstrated using yolk-shell-structured SiO2@N, P co-doped carbon spheres (SiO2@NPC Y.S.) with an optimized yolk size. The highly controlled structure with sufficient void spaces between the yolk and shell can effectively alleviate the volume swelling of SiO2, thereby improving the long cyclability during repeated lithiation/delithiation. Furthermore, N, P co-doped carbon shells can not only improve the electrical conductivity but also encourage the expansion of the interlayer distance of carbon, which is favorable for both Li + storage and rate performance. SiO2@NPC Y.S. shows a high capacity retention of 94.3% and reversible specific capacity of 705 mAh g−1 over 300 cycles at a current density of 0.1 A g−1. This work would pave the way for the design of anode materials of LIBs with highly controlled yolk-shell structures and heteroatom co-doping.