Si-based Anodes Research Articles

N-rich porous Si@SiOx/NC composites derived from in situ polymerisation of acrylic acid as anode for Li-ion batteries

Si possesses a high theoretical specific capacity as anode material for Li-ion batteries. However, it has poor electrical conductivity and severe volume effect during charge-discharge processes, resulting in substantial internal resistance and significantly reduced available capacity. These issues can be greatly mitigated by encapsulating Si nanoparticles within a carbonous material. Hence, network precursors are synthesised herein to encapsulate Si nanoparticles by in situ polymerisation of acrylic acid and melamine. After freeze-drying, the precursors are pyrolysed under Ar atmosphere to obtain homogeneous N-rich porous Si@SiOx/NC composites. A fibrous network structure is acquired by using appropriate amounts of polyacrylic acid and Si. Such a structure provides an outstanding electron transmission network and effectively buffers the volume change of Si to maintain a stable electrode structure. The results show that when the content of Si nanoparticles in the composite is 35.2 wt%, the prepared Si@SiOx/NC−2 composite has abundant micropores (267.90 m2 g−1) and mesopores (17.48 m2 g−1). The material shows an initial discharge-specific capacity of 1833.6 mAh g−1 and Coulombic efficiency of 65%. After 150 cycles at 0.1 A g−1, the discharge-specific capacity is still as high as 922.8 mAh g−1. The excellent electrochemical performance of the Si@SiOx/NC composites is due to the three-dimensional conductive structure. The unique construction could play an important role in expanding the commercial application of Si-based anode materials in Li-ion batteries.

Fabrication of Si/N-doped carbon nanotube composite via spray drying followed by catalytic chemical vapor deposition

Developing an effective structure for the silicon-carbon composite that promotes electric-ionic conductivity and reduces the volume change is a key issue for Si-based anode. In this study, spherical granules comprising silicon nanoparticles (Si-NPs) grafted with nitrogen-doped carbon nanotubes (Si-NCNTs) are fabricated via spray drying followed by catalytic chemical vapor deposition (CCVD). The initial discharge and charge capacities of the Si-NCNTs are 2457 and 1820 mA h g−1, respectively. The Si-NCNTs shows a capacity retention of 57% after 200 cycles as well as improved rate capability when compared to the Si-NPs and commercial CNTs composites (Si-CNTs) fabricated via spray drying alone. The Li+ ion-diffusion-coefficient (DLi+) of the Si-NCNTs is approximately ∼three times larger than that of the Si-CNTs at critical lithiation potential. The NCNTs that form the interconnections between Si-NPs play the role of electrically conductive buffers that could accommodate the volume change produced and favor Li+ ion transport.

Gradient H-Bonding Supports Highly Adaptable and Rapidly Self-Healing Composite Binders with High Ionic Conductivity for Silicon Anodes in Lithium-Ion Batteries.

An ideal binder for high-energy-density lithium-ion batteries (LIBs) should effectively inhibit volume effects, exhibit specific functional properties (e.g., self-repair capabilities and high ionic conductivity), and require low-cost, environmentally friendly mass production processes. This study adopts a synergistic strategy involving gradient (strong-weak) hydrogen bonding to construct a hard/soft polymer composite binder with self-healing abilities and high battery cell environments adaptability in LIBs. The meticulously designed 3D network structure comprising continuous electron transport pathways buffers the mechanical stresses caused by changes in silicon volume and improves the overall stability of the solid electrolyte interphase film. The Si-based anode with a polymer composite binder poly(acrylic acid-g-ureido pyrimidinone5% )/polyethylene oxide (Si/PAA-UPy5% /PEO) achieves a reversible capacity of 1245 mAh g-1 after 200 cycles at 0.5 C, which is 6.6 times higher than that of the Si/PAA anode. After 200 cycles at 0.2 A g-1 , a half-cell comprising Si/C anode with a polymer composite binder (Si/C/PAA-UPy5% /PEO) has a remaining specific capacity of 420 mAh g-1 and a capacity retention rate of 79%. The corresponding full cell with a Li-based cathode (LiFePO4 /Si/C/PAA-UPy5% /PEO) has an initial area capacity of 0.96 mAh cm-2 and retains an area capacity of 0.90 mAh cm-2 (capacity retention rate = 93%) after 100 cycles at 0.2 A g-1 .

High-performance Si@C anode for lithium-ion batteries enabled by a novel structuring strategy.

Si anode has drawn growing attention because of its features of large specific capacity, low electrochemical potential, and high natural abundance. However, it suffers from severe electrochemical irreversibility due to its large volume change during cycling. In spite of the achievement of improved electrochemical performance after compositing with carbon materials, most of the reported Si/C composite anodes lack a simple preparation process. To obtain a promising Si-based anode material, both simple preparation process and improved performance are necessary. Herein, inspired by the structure of shock proof foam, a novel structure of Si-based composite (Si@FeNO@P), consisting of Si nanoparticles embedded within a highly graphitized Fe3C/Fe3O4 hybrid nanoparticle-interspersed foam-like porous carbon matrix, has been constructed using a simple method, consisting of simple mixing, drying, and carbonization processes. Thus, the well-designed composite structure effectively mitigates issues resulting from volumetric change of the Si during cycle and hence improves its performance significantly. The research results confirm outstanding performance of the Si@FeNO@P anode in the aspects of cycle durability, specific capacity, and rate capability, with 1116.1 (250th cycle), 858.1 (500th cycle), and 503.1 (500th cycle) mA h g-1 at 100, 1000, and 5000 mA g-1, respectively. By comparing the performance and structure of Si@FeNO@P with other control samples, it was substantiated that the outstanding performances of the Si@FeNO@P anode depend on the synergistic effects of the well-designed unique carbon matrix, conductive Fe3C, and Fe3O4-in situ derived metallic Fe nanoparticles during cycling. The outstanding electrochemical performance and simple preparation route make the Si@FeNO@P anode promising for lithium-ion battery applications. This work also gives useful insights into the development of high-performance Si-based anodes with simple practical methods.

Research progress in nanotechnology for enhanced silicon-based and iron-based anodes for lithium-ion batteries

Recent research has focused on making suitable anode materials for lithium-ion batteries and using nanotechnology to refine composite electrode materials with high reversible capacity and strong stability. However, much work remains to be done to develop these materials into commercially viable solutions. The anode materials must have high reversible capacity, a long lifetime, and the ability to accept and release lithium ions repeatedly. Nano-engineered composite anode materials based on silicon and iron have shown good promise but need improved electrochemical properties and longer effective lifetimes. This paper summarizes the performance characteristics of Si-based and Fe-based anodes and ways to improve their performance through nanoengineering.

AlSixP: A new family of ternary Si-based anodes for Li-ion batteries with superior Li-storage properties

Silicon, as the highest capacity lithium-ion battery (LIB) anode material, has been commercialized due to its mature industrial foundation, abundant reserves, and environmental benign. However, its relatively slow Li-ionic and electronic conductivity impede its large-scale application when fast charging and discharging are required. To significantly improve the reaction kinetics, we propose to co-introduce aluminum and phosphorus into silicon at the same time, forming a novel family AlSi x P (x = 1, 3, 6) solid solutions. As anodes for LIBs, the equimolar compound of AlSiP presents longer cycling stability and much higher rate performance than Si counterparts due to the faster electronic and Li-ionic conductivity and the rich underlithiated electrochemical intermediates of which reduce the volume variation. The AlSi 3 P and AlSi 6 P are also prepared and present similar Li-storage superiority, suggesting the AlSi x P series materials are promising to be utilized in the real world.

Enzymatically demethylated pectins: from fruit waste to an outstanding polymer binder for silicon-based anodes of Li-ion batteries

Enzymatically demethylated citrus pectins: an efficient polymer binder in Si-based anodes of Li-ion batteries.

The Microparticles SiOx Loaded on PAN-C Nanofiber as Three-Dimensional Anode Material for High-Performance Lithium-Ion Batteries

Three-dimensional C/SiOx nanofiber anode was prepared by polydimethylsiloxane (PDMS) and polyacrylonitrile (PAN) as precursors via electrospinning and freeze-drying successfully. In contrast to conventional carbon covering Si-based anode materials, the C/SiOx structure is made up of PAN-C, a 3D carbon substance, and SiOx loading steadily on PAN-C. The PAN carbon nanofibers and loaded SiOx from pyrolyzed PDMS give increased conductivity and a stable complex structure. When employed as lithium-ion batteries (LIBs) anode materials, C/SiOx-1% composites were discovered to have an extremely high lithium storage capacity and good cycle performance. At a current density of 100 mA/g, its reversible capacity remained at 761 mA/h after 50 charge-discharge cycles and at 670 mA/h after 200 cycles. The C/SiOx-1% composite aerogel is a particularly intriguing anode candidate for high-performance LIBs due to these appealing qualities.

Dual carbon boosts silicon-based anodes for excellent initial coulombic efficiency and cycling stability of lithium-ion batteries

Benefiting from its ultrahigh theoretical capacity and abundant resources, silicon (Si) is considered a prospective anode material. However, Si faces great challenges in practical applications, such as low initial coulombic efficiency (ICE) and rapid capacity decay. Herein, a silicon/graphite/reduced graphene oxide (Si/Gt/RGO) composite was prepared by agitation, freeze-drying, and heat treatment, where Si nanoparticles were embedded in a graphite (Gt) matrix and tightly wrapped by reduced graphene oxide (RGO). Graphite can promote ICE, improve lithium-ion (Li+) transport kinetics, and serve as the matrix to mitigate the swelling of Si. RGO further ensures rapid Li+ diffusion and forms a flexible shell of Si nanoparticles. The flexible shell formed by RGO can relieve internal stress and increase the tolerance of Si swelling. The dual carbon (graphite and RGO) protects Si nanoparticles from pulverization and ensures the electronic contact of Si, thereby rendering superior electrochemical properties. Si/Gt/RGO shows an excellent ICE (81.54 %), a promoted cycling stability (1007.0 mAh g−1 at 0.2 A g−1 after 100 cycles with capacity retentions of 91 % and 686.3 mAh g−1 after 200 cycles at 1 A g−1) and an outstanding rate capability (475.8 mAh g−1 at 3 A g−1). The research provides a methodology for simultaneously enhancing the ICE and cycling properties of silicon-based (Si-based) anodes and provides an idea for the rational design of LIB anodes with high- energy- density.

An electrochemical compatibility investigation of RTIL-based electrolytes with Si-based anodes for advanced Li-ion batteries

Silicon is amongst the most attractive anode materials for Li-ion batteries because of its high gravimetric and volumetric capacities; importantly, it is also abundant and cheap, thus sustainable. For a widespread practical deployment of Si-based electrodes, research efforts must focus on significant breakthroughs to addressing the major challenges related to their poor cycling stability. In this work, we focus on the electrolyte-electrode relationships to support the scientific community with a systematic overview of Si-based cell design strategies reporting a thorough electrochemical study of different room temperature ionic liquid (RTIL)-based electrolytes, which contain either lithium bis(fluorosulfonyl)imide (LiFSI) or lithium bis(trifluoromethylsulfonyl)imide (LiTFSI). Their galvanostatic cycling performances with mixed silicon/graphite/few-layer graphene electrodes are evaluated, with first cycle Coulombic efficiency approaching 90% and areal capacity ≈2 mAh/cm2 in the limited cut-off range of 0.1–2 V vs. Li+/Li0. The investigation evidences the superior characteristics of the FSI-based RTILs with respect to the TFSI-based one, which is mostly associated with the superior SEI forming ability of FSI-based systems, even without the use of specific additives. In particular, the LiFSI-EMIFSI electrolyte composition shows the best performance in both Li-half cells and Li-ion cells in which the Si-based electrodes are coupled with 4V-class composite NMC-based cathodes.

Machine Learning in the development of Si-based anodes using Small-Angle X-ray Scattering for structural property analysis

Material development processes are highly iterative and driven by the experience and intuition of the researcher. This can lead to time consuming procedures. Data-driven approaches such as Machine Learning can support decision processes with trained and validated models to predict certain output parameter. In a multifaceted process chain of material synthesis of electrochemical materials and their characterization, Machine Learning has a huge potential to shorten development processes. Based on this, the contribution presents a novel approach to utilize data derived from Small-Angle X-ray Scattering (SAXS) of SiO2 matrix materials for battery anodes with Neural Networks. Here, we use SAXS as an intermediate, high-throughput method to characterize sol–gel based porous materials. A multi-step-method is presented where a Feed Forward Net is connected to a pretrained autoencoder to reliably map parameters of the material synthesis to the SAXS curve of the resulting material. In addition, a direct comparison shows that the prediction error of Neural Networks can be greatly reduced by training each output variable with a separate independent Neural Network.

Si-TiSi2 clusters eutectic nanoparticles as high initial coulombic efficiency anodes for lithium-ion batteries

The poor initial coulombic efficiency of silicon-based anode electrode is a major challenge hindering its practical application. In the initial cycle, the excessive consumption of lithium ions leads to significant reduction in energy density. Here, we propose a unique structure of eutectic nanoparticles containing TiSi2 clusters in the main phase of Si. The interaction between TiSi2 cluster and Si increases the lattice spacing of Si, reduces the lithium-ion insertion resistance and improves the initial coulombic efficiency of the electrode. The Si-TiSi2 clusters eutectic nanoparticles provide a high initial coulombic efficiency of 89.7% at 0.5 A g−1. This work provides a new enlightenment for high initial coulombic efficiency Si-based anodes.

A scalable silicon/graphite anode with high silicon content for high-energy lithium-ion batteries

High-capacity Si-based anodes are urgently needed for high-energy lithium-ion batteries in forthcoming electric vehicles and energy storage systems. However, it is still a challenge to prepare Si anodes with high Si content materials as well as good electrochemical performance because the accumulation and growth of Si lead to large volume expansion, pulverization and cycling degradation. Herein, we demonstrate feasibility of a high-capacity Si-based anode via a scalable and simple route using high Si content (31.6 wt%) Si/graphite composite, consisting of thin Si nanolayer and edge-sites-exposed graphite. This architecture effectively alleviates the volume changes of Si and facilitates lithium-ion transport. As a result, the Si/graphite composite delivers a reversible capacity of 1,080 mAh/g with an initial Coulombic efficiency of 86.3% and achieves outstanding cycling stability (94.3% capacity retention after 100 cycles). When combined with commercial graphite-blended systems for a 1.5 Ah pouch-type full-cell test under a high electrode density (1.6 g/cm3) and areal capacity (3.46 mAh/cm2), the composite demonstrates excellent cycling stability at 25 and 45 °C, respectively, and good high-rate performance. This strategy offers a practical feasibility of next-generation high-capacity anode for high-energy LIBs.

Silicon quantum dots inlaid micron graphite anode for fast chargeable and high energy density Li-ion batteries.

The pursuit of rapid charging and high energy density in commercial lithium-ion batteries (LIBs) has been one of the priorities in battery research. Silicon-Carbon (Si-C), a possible substitute for graphite as an anode electrode material, is one prospect to achieving this goal. There is a debate as to whether nanoscale or the micron-scale silicon is more favourable as anode materials for LIBs. Micron-scale silicon exhibits relatively higher initial coulomb efficiency (CE) compared with nanoscale silicon, while its cycle stability is poorer. However, minimizing silicon normally benefits the cycle stability, but introduces serious side reactions, due to the large active surface for nanoscale silicon. Here, we propose silicon quantum dots (Si QDs) inlaid in micron graphite (SiQDs-in-MG) as an anode for high energy density and fast charging LIBs. The Si QDs almost eliminate the volume change typically observed in Si during long-term cycling, while the graphite blocks solvent entering the channels and contacting the SiQDs, promoting the generation of a stable solid electrolyte interphase, which is not in direct contact with the Si. SiQDs-in-MG addresses the main issues for Si-based anodes and is expected to achieve high energy density when in combination with a Lithium-Nickel-Manganese-Cobalt-Oxide (NMC) cathode in pouch cells.

Density functional theory assessment of the lithiation thermodynamics and phase evolution in si-based amorphous binary alloys

Development of novel alloy-based anodes has the potential to increase the energy storage capacity of current Li-ion based energy storage technology. In particular, Si-based anodes are of interest due to their high theoretical capacity, but suffer from poor cycle and calendar life stemming from large volumetric expansion and a non-passivating solid-electrolyte interface. The addition of amorphous components to the Si anode has been shown to improve the mechanical and chemical stability during lithiation. In this study, we use density functional theory (DFT) to probe the thermodynamics of amorphous alloy formation in a range of binary Si-X alloy systems, where X constitutes any element from periodic table groups 1-17. The alloying elements are classified as active or inactive components based on the reactivity with Li, where active elements form stable binary compounds with Li and inactive elements do not. We find that when alloying inactive elements, most inactive components do not fully reduce and hence result in the extrusion of metallic phases. Formation of Si-X compounds with no reactivity to Li results in deactivation of Si and decreased capacity. Alloying with Li-inactive elements also bypasses early Si lithiation stages and decreases the onset potential for lithiation. Most of the Li-active elements do not form stable Si-X binaries or Li-Si-X ternaries, resulting in lithiation potentials composed of voltage steps matching those of the base elements (Li x X and Li x Si), while the others may not be of much practical use due to their high lithiation potentials or preciousness, but may buffer against volumetric expansion.

Modulation and quantitative study of conformal electrode-electrolyte interfacial chemistry toward high-energy-density LiNi0.6Co0.2Mn0.2O2‖SiO-C pouch cells

High-nickel layered ternary cathode coupling with Si-based anode is one of the most promising strategies to realize high-energy-density batteries for power electric vehicles. However, undesired interfacial instability on both sides of cathode and anode causes continuous parasitic reactions and phase transformations, and results in fast degradation of the batteries. To address this issue, herein, in-situ reliable, compact and ionically conductive interface films are constructed effectively on both LiNi0.6Co0.2Mn0.2O2 (NMC622) cathode and SiO-C anode simultaneously by simply using a multifunctional additive, lithium difluorobis(oxalato) phosphate (LiDFBOP), due to its preferential redox reactivity then efficiently influencing the subsequent electrochemical behaviors of bulk electrolyte. These films shield the electrodes against the electrolyte attack, thus enabling long-term cycling stability and enhancing Coulombic efficiency of NMC622/SiO-C pouch cells. In addition, the highly Li-ionically conductive interphases also promote the electrode kinetics, which ensure the excellent rate capability as well as low temperature performance. The underlying interface formation mechanisms in term of specific consumption amount of additive on each electrode simultaneously are quantitatively studied by combining several complementary advanced characterizations techniques such as IC, TOF-SIMS, XPS and HRTEM etc., which not only benefit to predict the optimal addition content for cost-effective electrolyte in the actual conditions, but also validate that abundant Li-containing fluorinated inorganics and organic species regulate the microstructure and the composition of interface films, leading to enhanced ionic conductivity and intensified structure integrity, then finally contributing to the improved electrochemical performance of full pouch cells. New and in-depth insight in additive-involved interface reactions provides new opportunities for the design of rational surface films to realize high-energy batteries.

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 pursuit of commercial silicon-based microparticle anodes for advanced lithium-ion batteries: A review

Silicon (Si) is one of the most promising anode materials for high-energy lithium-ion batteries. However, the widespread application of Si-based anodes is inhibited by large volume change, unstable solid electrolyte interphase, and poor electrical conductivity. During the past decade, significant efforts have been made to overcome these major challenges toward industrial applications. This review summarizes the recent development of microscale Si-based electrodes fabricated by Si microparticles or other industrial bulk materials from the perspective of industrialization. First, the challenges for microscale Si anodes are clarified. Second, structural design strategies of stable micro-sized Si materials are discussed. Third, other critical practical metrics, such as robust binder construction and electrolyte design, are also highlighted. Finally, future trends and perspectives on the commercialization of Si-based anodes are provided.

The Role of Oxygen in Lithiation and Solid Electrolyte Interphase Formation Processes in Silicon-Based Anodes

Silicon oxides (SiOx) have been considered as promising alternatives to pure Si in high energy anodes in lithium-ion batteries (LIBs) due to their improved cycling stability. However, their fundamental lithiation mechanism has not yet been systematically investigated, and potential collateral downsides remain unclear. In this work, we report on the role of oxygen in lithiation/delithiation and solid electrolyte interphase (SEI) formation processes in SiOx thin film model electrodes with different oxygen contents. We show that the SiOx anodes with higher oxygen content experience smaller volume change and form a thinner and more stable SEI, both of which are beneficial for cycling stability. However, these SiOx anodes also show an irreversible lithiation at around 0.7 V attributed to the reduction of Si oxides, leading to lower first cycle coulombic efficiency that is undesirable for practical applications. Overall, these results offer a balanced perspective on the advantages and disadvantages that oxygen brings to Si-based anodes in LIBs.

Dual structure engineering of SiOx-acrylic yarn derived carbon nanofiber based foldable Si anodes for low-cost lithium-ion batteries.

Silicon (Si) is attracted much attention due to its outstanding theoretical capacity (4200 mAh/g) as the anode of lithium-ion batteries (LIBs). However, the large volume change and low electron/ion conductivity during the charge and discharge process limit the electrochemical performance of Si-based anodes. Here we demonstrate a foldable acrylic yarn-based composite carbon nanofiber embedded by Si@SiOx particles (Si@SiOx-CACNFs) as the anode material. Since the amorphous SiOx and carbon (C) coating on the outside of the Si particles can provide a double buffer for volume expansion while reducing the contact between the Si core and the electrolyte to form a thin and stable solid electrolyte interface (SEI) film. Simultaneous in-situ electrochemical impedance spectroscopy (in-situ EIS) and galvanostatic intermittent titration technique (GITT) tests show that SiOx and C have higher ion/electron transport rates, and in addition, using acrylic fiber yarn and Zn(Ac)2 as raw materials reduces the manufacturing cost and enhanced mechanical properties. Therefore, the half-cell can achieve a high initial Coulombic efficiency (ICE) of 82.3% and a reversible capacity of 1358.2 mAh/g after 180 cycles. It can return to its original shape and remain intact after four consecutive folds, and the soft-pack full battery can also light up LED lights under different bending conditions.