Silicon Anodes In Lithium-ion Batteries Research Articles

Understanding solid electrolyte interface formation on graphite and silicon anodes in lithium-ion batteries: Exploring the role of fluoroethylene carbonate

This study explores how fluoroethylene carbonate (FEC) influences the solid electrolyte interface (SEI) layer formation during battery cycling process. FEC improves SEI properties, producing a uniform, chemically stable layer enriched with lithium fluoride. This enhances mechanical resilience and electrochemical stability. FEC also suppresses electrolyte deformation and decomposition, maintaining its initial state. The findings highlight the significance and comprehension of electrolyte additives, offering an electrolyte research pathway for improving Li-ion battery performance and durability.

Novel Binder with Cross-Linking Reconfiguration Functionality for Silicon Anodes of Lithium-Ion Batteries.

Silicon is expected to be used as a high theoretical capacity anode material in lithium-ion batteries with high energy densities. However, the huge volume change incurred when silicon de-embeds lithium ions, leading to destruction of the electrode structure and a rapid reduction in battery capacity. Although binders play a key role in maintaining the stability of the electrode structure, commonly used binders cannot withstand the large volume expansion of the silicon. To alleviate this problem, we propose a PGC cross-linking reconfiguration binder based on poly(acrylic acid) (PAA), gelatin (GN), and β-cyclodextrin (β-CD). Within PGC, PAA supports the main chain and provides a large number of carboxyl groups (-COOH), GN provides rich carboxyl and amide groups that can form a cross-linking network with PAA, and β-CD offers rich hydroxyl groups and a cone-shaped hollow ring structure that can alleviate stress accumulation in the polymer chain by forming a new dynamic cross-linking coordination conformation during stretching. In the half cell, the silicon negative prepared by the PGC binder exhibited a high specific capacity and capacity maintenance ratio, and the specific capacity of the silicon negative electrode prepared by the PGC binder is still 1809 mAh g-1 and the capacity maintenance ratio is 73.76% following 200 cycles at 2 A g-1 current density, indicating that PGC sufficiently maintains the silicon negative structure during the battery cycle. The PGC binder has a simple preparation method and good capacity retention ability, making it a potential reference for the further development of silicon negative electrodes.

Steric molecular combing effect enables Self-Healing binder for silicon anodes in Lithium-Ion batteries

Silicon is a promising anode material for lithium-ion batteries with its superior capacity. However, the volume change of the silicon anode seriously affects the electrode integrity and cycle stability. The waterborne guar gum (GG) binder has been regarded as one of the most promising binders for Si anodes. Here, a unique steric molecular combing approach based on guar gum, glycerol, and citric acid is proposed to develop a self-healing binder GGC, which would boost the structural stability of electrode materials. The GGC binder is mainly designed to weaken van der Waals' forces between polymers through the plasticizing effect of glycerol, combing and straightening the guar molecular chain of GG, and exposing the guar hydroxyl sites of GG and the carboxyl groups of citric acid. The condensation reaction between the hydroxyl sites of GG and the carboxyl groups of citric acid forms stronger hydrogen bonds, which can help achieve self-healing effect to cope with the severe volume expansion effect of silicone-based materials. Silicon electrode lithium-ion batteries prepared with GGC binders exhibit outstanding electrochemical performance, with a discharge capacity of up to 1579 mAh/g for 1200 cycles at 1 A/g, providing a high capacity retention rate of 96%. This paper demostrates the great potential of GGC binders in realizing electrochemical performance enhancement of silicon anode.

Designing Compatible Ceramic/Polymer Composite Solid-State Electrolyte for Stable Silicon Nanosheet Anodes.

The commercialization of silicon anode for lithium-ion batteries has been hindered by severe structure fracture and continuous interfacial reaction against liquid electrolytes, which can be mitigated by solid-state electrolytes. However, rigid ceramic electrolyte suffers from large electrolyte/electrode interfacial resistance, and polymer electrolyte undergoes poor ionic conductivity, both of which are worsened by volume expansion of silicon. Herein, by dispersing Li1.3 Al0.3 Ti1.7 (PO4 )3 (LATP) into poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) and poly(ethylene oxide) (PEO) matrix, the PVDF-HFP/PEO/LATP (PHP-L) solid-state electrolyte with high ionic conductivity (1.40 × 10-3 Scm-1 ), high tensile strength and flexibility is designed, achieving brilliant compatibility with silicon nanosheets. The chemical interactions between PVDF-HFP and PEO, LATP increase amorphous degree of polymer, accelerating Li+ transfer. Good flexibility of the PHP-L contributes to adaptive structure variation of electrolyte with silicon expansion/shrinkage, ensuring swift interfacial ions transfer. Moreover, the solid membrane with high tensile limits electrode structural degradation and eliminates continuous interfacial growth to form stable 2D solid electrolyte interface (SEI) film, achieving superior cyclic performance to liquid electrolytes. The Si//PHP-L15//LiFePO4 solid-state full-cell exhibits stable lithium storage with 81% capacity retention after 100 cycles. This work demonstrates the effectiveness of composite solid electrolyte in addressing fundamental interfacial and performance challenges of silicon anodes.

Nanoarchitectonics of 3D-networked bio-based binders for silicon anodes in lithium-ion batteries based on dynamic hydrogen bonding

A bio-based binder was developed to improve the electrochemical performance of silicon-anode lithium-ion batteries.

Dynamic hydrogen bond cross-linking binder with self-healing chemistry enables high-performance silicon anode in lithium-ion batteries

The structure instability and cycling decay of silicon (Si) anode triggered by stress buildup hinder its practical application to next-generation high-energy–density lithium-ion batteries (LIBs). Herein, a cross-linking polymeric network as a self-healing binder for Si anode is developed by in situ polymerization of tannic acid (TA) and polyacrylic acid (PAA) binder labelled as TA-c-PAA. The branched TA as a physical cross-linker complexes with PAA main chains through abundant dynamic hydrogen bonds, endowing the cross-linking TA-c-PAA binder with unique self-healing property and strong adhesion for Si anode. Benefiting from the mechanical robust and hard adhesion, the Si@TA-c-PAA electrode exhibits high reversible specific capacities (3250 mAh/g at 0.05C (1C = 4000 mA g−1)), excellent rate capability (1599 mAh/g at 2C), and impressive cycling stability (1742 mAh/g at 0.25C after 450 cycles). After Ex situ morphology characterization, in situ swelling analysis, and finite element simulation, it is found that the TA-c-PAA binder allows the Si anode to dissipate stress and prevent pulverization during lithiation and delithiation, thus the hydrogen bonds among interpenetrating network may be adaptable to the stress intensity. Our work paves a new avenue for the design of efficient and cost-effective binders for next-generation Si anode in LIBs.

Atomistic Insight into the Role of Porous Structure in Accommodating the Volume Expansion of Silicon Anodes for Lithium-Ion Batteries

Despite possessing high theoretical gravimetric capacity, the practical utilization of silicon anodes for lithium-ion batteries is still challenging because of poor capacity retention caused by massive volume expansion upon lithium insertion. The use of porosity to tackle this issue has widely been scrutinized, and porous silicon materials have been experimentally shown to have improved cycling stability. To provide a fundamental understanding of the structural and chemical evolution, here, we investigate the atomistic behaviors of porous silicon nanowires during lithiation and delithiation by means of a reactive molecular dynamics method. The simulations show that although the porous nanomaterials undergo a large intrinsic volume expansion similar to the non-porous ones, the hollow space available inside the materials can be exploited for lowering the external expansion via the local structure relaxation in the vicinity of the pore. Due to such relaxation, a small pore undergoes structural collapse during the first charge, suggesting that a relatively large pore diameter and a thin wall thickness are required to maintain the porous structural integrity. The simulations also unveil the evolution of the local stresses generated during lithium migration into and out of the materials, which emphasizes the role of porosity in alleviating the induced stresses.

Bio-Based Adenine-Derived Polyimide as a Dual-Functional Binder for the Silicon Anode in Lithium-Ion Batteries

Bio-Based Adenine-Derived Polyimide as a Dual-Functional Binder for the Silicon Anode in Lithium-Ion Batteries

Unlocking the potential of silicon anodes in lithium-ion batteries: A claw-inspired binder with synergistic interface bonding

Binders play a crucial role in enhancing the cycling stability of silicon anodes in next-generation Li-ion batteries. However, traditional linear polymer binders have difficulty withstanding the volume expansion of silicon during cycling. Herein, inspired by the fact that animals’ claws can grasp objects firmly, a claw-like taurine-grafted-poly (acrylic acid) binder (Tau-g-PAA) is designed to improve the electrochemical performance of silicon anodes. The synergistic effects of different polar groups (sulfo and carboxyl) in Tau-g-PAA facilitate the formation of multidimensional interactions with silicon nanoparticles and the diffusion of Li ions, thereby greatly improving the stability and rate performance of silicon anodes, which aligns with results from density functional theory (DFT) simulations. As expected, a Tau-g-PAA/Si electrode exhibits excellent cycling performance with a high specific capacity of 1003 ​mA ​h ​g−1 ​at 1 ​C (1 ​C ​= ​4200 ​mA ​h ​g−1) after 300 cycles, and a high rate performance. The design strategy of using polar small molecule-grafted polymers to create claw-like structures could inspire the development of better binders for silicon-based anodes.

Interweaving Elastic and Hydrogen Bond-Forming Polymers into Highly Tough and Stress-Relaxable Binders for High-Performance Silicon Anode in Lithium-Ion Batteries.

A central challenge in practically using high-capacity silicon (Si) as anode materials for lithium-ion batteries is alleviating significant volume change of Si during cycling. One key to resolving the failure issues of Si is exploiting carefully designed polymer binders exhibiting mechanical robustness to retain the structural integrity of Si electrodes, while concurrently displaying elasticity and toughness to effectively dissipate external stresses exerted by the volume changes of Si. Herein, a highly elastic and tough polymer binder is proposed by interweaving polyacrylic acid (PAA) with poly(urea-urethane) (PUU) elastomer for Si anodes. By systematically tuning molecular parameters, including molecular weights of hard/soft segments and structures of hard segment components, it is demonstrated that the mechanical properties of polymer binders, such as elasticity, toughness, and stress relaxation ability, strongly affect the cycling performance of Si electrodes. This study provides new insight into the rational design of polymer binders capable of accommodating the volume changes of Si, primarily by judicious modulation of the mechanical properties of polymer binders.

Demystifying the Asymmetry in Lithiation/Delithiation Behaviors of Silicon Anodes for Lithium-Ion Batteries

One critical factor that impedes the wide adoption of electric vehicles is the charging time, which is considerably longer when compared to the refuel time of internal combustion vehicles. To shorten the charging time to less than 6 minutes, extremely fast charging (XFC) of more than 10C is required. In recent years, silicon was regarded as a promising candidate for fast charging because it has a high energy density and is less prone to lithium dendrite growth. However, existing Silicon technologies have not surpassed the 6-minute charging goal. Here, we discuss the possibility for XFC of a three-dimensionally engineered electrically conductive porous Ni/Si composite anode. This anode structure can effectively alleviate the huge volume change upon cycling and provide a pathway for fast electron and ion conduction. Although it shows excellent delithiation (discharging) rate capabilities when coupled with an optimized electrolyte, the lithiation capacity is severely limited at higher C-rates. To study the asymmetry in lithiation/delithiation and the mechanism of relatively sluggish lithiation, we performed rate performance test, Galvanostatic Intermittent Titration Technique (GITT) and Direct Current Electrochemical Impedance Spectroscopy (DCEIS). Based on our findings, we propose the potential rate limiting step for lithiation, which is believed to improve the charging rates substantially when overcome.

(Digital Presentation) An Initiator-Free and in-Situ Constructed Solid Electrolyte for High Energy Density Batteries with Si Anodes

The emerging electrical applications and transportation electrification call for safe and energy-dense batteries with long lifespans and considerable power outputs. For the current graphite-majority LIBs, the anode takes up more than 30% of the mass ratio and around 50% of the volume ratio within the cell unit because of the low specific capacity of the graphite (theoretical capacity ~372 mAh g-1), leading to a low energy density around 200 Wh kg-1. Replacing the insertion-type graphite anode with the conversion-type Si anode (theoretical capacity ~3579 mAh g-1) [1] or the Li-metal anode (theoretical capacity ~3860 mAh g-1) could help reduce the mass and volume portion to less than 5% and 10%, respectively, which is thus of great significance for further promotion of the energy density (>350 Wh kg-1) at the cell level. Aside from the performance-related issues, the safety concerns of LIBs should also be well addressed. Therefore, solid state electrolytes have triggered worldwide interest in the past few years for its incomparable safety of anti-combustion and no leakage. Besides, the solid-state electrolytes could also boost the promotion of battery energy density.However, most of the current research about solid-states electrolytes adopt Li-metal as the anode. Though solid-state Li-metal batteries (SSLMBs) are acclaimed to have the highest gravimetric specific energy density theoretically, it is challenged by several critical issues. First, the Li-metal anode could not well address the dendrite issue, which limits the critical current density (< 0.5 mA cm-2) and areal capacities (< 0.5 mA cm-2) of the battery [2]. Secondly, most of the reported SSLMBs are carried out at high-temperature (60℃ or above) or with incredibly huge pressure (fabrication at > 200 MPa; operation at > 50 MPa) [3][4], which is not realistic in the common scenarios. Besides, nearly all the reported SSLMBs are tested with large Li-excess (low reversibility of Li-plaiting and stripping) and limited cathode loadings (inefficient conductivity), leading to unacceptable energy densities of the cells.Herein, we present that the Si-anode, which is not as widely as Li-metal studied in solid-state batteries, is a well-qualified candidate for the Li-metal for practical solid batteries. The pure Si anode (~2.1 mAh cm-2) with the solid electrolyte can be stably cycled at room temperature without external pressure for more than 150 cycles with no sharp capacity fade and a remained capacity over 1800 mAh g-1. The Si||LiFePO4 full cell adopting this electrolyte could achieves 120 stable cycles with high Coulombic efficiencies (>99.9%). This study shows that the in-situ polymerized solid electrolyte could be well matched with Si-anode for practical high energy density battery configuration. Acknowledgement The work described in this paper was fully supported by a grant from the Research Grants Council of the Hong Kong Special Administrbative Region, China (Project No. R6005–20). Reference [1] M.S. Kang, I. Heo, S. Kim, J. Yang, J. Kim, S.-J. Min, J. Chae, W.C. Yoo, High-areal-capacity of micron-sized silicon anodes in lithium-ion batteries by using wrinkled-multilayered-graphenes, Energy Storage Mater. 50 (2022) 234–242.[2] Q. Zhao, S. Stalin, C.Z. Zhao, L.A. Archer, Designing solid-state electrolytes for safe, energy-dense batteries, Nat. Rev. Mater. 5, (2020) 229–252.[3] D.H.S. Tan, Y.-T. Chen, H. Yang, W. Bao, B. Sreenarayanan, J. Doux, W. Li, B. Lu, S. Ham, B. Sayahpour, J. Scharf, E.A. Wu, G. Deysher, H.E. Han, H.J. Hah, H. Jeong, J.B. Lee, Z. Chen, Y.S. Meng, Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes, Science 373 (2021) 1494–1499.[4] Y. Ren, Z. Cui, A. Bhargav, J. He, A. Manthiram, A Self-Healable Sulfide/Polymer Composite Electrolyte for Long-Life, Low-Lithium-Excess Lithium-Metal Batteries, Adv. Funct. Mater. 2106680 (2021) 1–10. Figure 1

Research Progress on the Structural Design and Optimization of Silicon Anodes for Lithium-Ion Batteries: A Mini-Review

Silicon anodes have been considered one of the most promising anode candidates for the next generation of high-energy density lithium-ion batteries due to the high theoretical specific capacity (4200 mAh g−1) of Si. However, high lithiation capacity endows silicon anodes with severe volume expansion effects during the charge/discharge cycling. The repeated volume expansions not only lead to the pulverization of silicon particles and the separation of electrode materials from the current collector, but also bring rupture/formation of solid electrolyte interface (SEI) and continuous electrolyte consumption, which seriously hinders the commercial application of silicon anodes. Structural design and optimization are the key to improving the electrochemical performances of silicon anodes, which has attracted wide attention and research in recent years. This paper mainly summarizes and compares the latest research progress for the structural design and optimization of silicon anodes.

The Effects of Lithium Ions and pH on the Function of Polyacrylic Acid Binder for Silicon Anodes

Binder plays a critical role in the performance of silicon anodes for lithium-ion batteries, specifically by connecting particles of active material and promoting adhesion to the current collector. Recent studies have differed on the relative cycle life of silicon anodes made from water-based polyacrylic acid (PAA) vs LiOH-PAA binders. Differences between the two may be due to the pH value or the extra Li+ in the binder, both of which change when LiOH is added to PAA. Here we investigate the impact of these two variables on the performance of silicon anodes. Regarding the effect of Li+, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results confirm our hypothesis that the extra Li+ facilitates ion transport. Regarding pH, we find that high pH in binders is detrimental to the electrode mechanical integrity, as observed in peeling tests and cross-sectional imaging. However, viscosity tests reveal that increased pH benefits the coating and mixing process. Our cycling results show that LiOH-PAA binder maintains greater cell capacity than does PAA, and further that LiOH-PAA at pH 4.5 leads to a cell with the highest capacity. Therefore, an intermediate pH is an optimal compromise between benefits observed for the low and high pH experiments.

A novel design idea of high-stability silicon anodes for lithium-ion batteries: Building in-situ “high-speed channels” while reserving space

As one of the most promising anode materials for high-performance lithium-ion batteries, the commercial application of Si faces many dilemmas. In this paper, a facile method is developed to substantially improve the cycling stability of Si-based anodes. Firstly, based on the Kirkendall effect, the Si nanoparticle was transformed into multi-Si-void@SiO2 by heat-treatment. Then, the acid precipitation process was used to coat the lignin on the surface of the multi-Si-void@SiO2 structure via the hydrogen-bond interaction, and after in-situ carbonization, multi-Si-void@SiO2@lignin-based carbon composite was formed. The optimum electrode material maintained the specific capacity of 759 mA h g−1 after 1300 cycles at the current density of 1.0 A/g. The great electrochemical performance is attributed to the four components of voids, Si, SiO2 and lignin-based carbon (LC) performing their duties and synergistically, making the electrode exhibit excellent cycle stability. After long-term charge/discharge process, SiO2 layer is fully activated to construct Li4SiO4 and Li2O “high-speed channels”, providing a “bridge” for Si to connect with the outside. And the reserved space inside the structure is conducive to the free expansion and contraction of Si. Meanwhile, lignin, as a cheap and renewable carbon source, greatly reduces the cost of material preparation. Consequently, the multi-Si-void@SiO2@LC composite presented here provides a feasible strategy for the large-scale development of highly stable Si-based anodes.

Sponge-Like Porous-Conductive Polymer Coating for Ultrastable Silicon Anodes in Lithium-Ion Batteries.

Urgent calls for reversible cycling performance of silicon (Si) requires an efficient solution to maintain the silicon-electrolyte interface stable. Herein, a conductive biphenyl-polyoxadiazole (bPOD) layer is coated on Si particles to enhance the electrochemical process and prolong the cells lifespan. The conformal bPOD coatings are mixed ionicelectronic conductors, which not only inhibit the infinite growth of solid electrolyte interphase (SEI) but also endow electrodes with outstanding ion/electrons transport capacity. The superior 3D porous structure in the continuous phase allows the bPOD layers to act like a sponge to buffer volume variation, resulting in high structural stability. The in situ polymerized bPOD coating and it-driven thin LiF-rich SEI layer remarkably improve the lithium storage performance of Si anodes, showing a high reversible specific capacity of 1600 mAh g-1 even after 500 cycles at 1 A g-1 along with excellent rate capacity of over 1500 mAh g-1 at 3 A g-1 . It should be noticed that a long cycle life of 800 cycles with 1065 mAhg-1 at 3 A g-1 can also be achieved with a capacity retention of more than 80%. Therefore, we believe this unique polymer coating design paves the way for the widespread adoption of next-generation lithium-ion batteries.

Conductive Polymer Frameworks in Silicon Anodes for Advanced Lithium-Ion Batteries

Silicon anode is endowed with a high theoretical specific capacity. Unfortunately, its applicability in lithium-ion batteries is hindered by several inevitable problems, which are associated with volume changes (i.e., particle pulverization, solid electrolyte interphase layer instability, and electrode failure) and low electrical conductivity of silicon. Among the accessible strategies to enhance the anode performance, conductive polymer frameworks have been envisioned as solutions to overcome the problems. Conductive polymers can jointly bind and electronically connect silicon particles to regulate extensive volume changes while providing pathways for charge transport in a low-cost fashion. This review starts with a detailed summary of conductive polymer framework features in silicon anodes. The main section presents an in-depth discussion and current advancements of the most widely used conductive polymers in silicon anodes [i.e., polyfluorene, polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene)] and several other conductive polymers. In the penultimate part, we review the performance evaluation of silicon anodes with five main conductive polymers and provide perspectives on future challenges of batteries from the standpoint of device manufacturing scale-up. In the final part, we briefly summarize the discussed advancements of conductive polymer frameworks in silicon anode for lithium-ion batteries.

Hybrid Ionically Covalently Cross-Linked Network Binder for High-Performance Silicon Anodes in Lithium-Ion Batteries

Silicon has gained considerable attention as an anode material in lithium-ion batteries due to its high theoretical capacity. However, the significant volume changes that occur during lithiation/delithiation processes often result in poor cycling stability of silicon anodes. In this study, a hybrid ionically covalently cross-linked network binder carboxymethylcellulose-hyperbranched polyethyleneimine (CMC-HBPEI) is successfully constructed by “switching” ionic bonds and partially “converting” them to covalent bonds to buffer the volume variation of silicon anodes. In this hybrid cross-linked network, the covalently cross-linked network is responsible for maintaining the structural integrity of the anode, while the ionically cross-linked network utilizes the bonding reversibility to sustainably dissipative the mechanical stress and self-heal the structural breakages generated from the lithiation expansion of silicon. By changing the drying temperature of the anode, the ratio of covalent and ionic bonds in the hybrid cross-linked network can be adjusted to balance the mechanical stability and bonding reversibility of the CMC-HBPEI binder. Even after 300 cycles of charging/discharging under a current density of 500 mAg−1, the specific capacity of the optimized Si/CMC-HBPEI anode remains at 1545 mAhg−1.

Naturally nitrogen-doped self-encapsulated biochar materials based on mouldy wheat flour for silicon anode in lithium-ion batteries

Naturally nitrogen-doped self-encapsulated biochar materials based on mouldy wheat flour for silicon anode in lithium-ion batteries

Carboxymethyl Three-Dimensional Cross-Linked Biopolymer Binder for High-Performance Silicon Anodes in Lithium-Ion Batteries

Carboxymethyl Three-Dimensional Cross-Linked Biopolymer Binder for High-Performance Silicon Anodes in Lithium-Ion Batteries