Silicon-based Anodes For Lithium-ion Batteries Research Articles

Advances in Coating Materials for Silicon-Based Lithium-Ion Battery Anodes

Silicon anodes, which exhibit high theoretical capacity and very low operating potential, are promising as anode candidates that can satisfy the conditions currently required for secondary batteries. However, the low conductivity of silicon and the alloying/dealloying phenomena that occur during charging and discharging cause sizeable volume expansion with side reactions; moreover, various electrochemical issues result in inferior cycling performance. Therefore, many strategies have been proposed to mitigate these problems, with the most commonly used method being the use of nanosized silicon. However, this approach leads to another electrochemical limitation—that is, an increase in side reactions due to the large surface area. These problems can effectively be resolved using coating strategies. Therefore, to address the issues faced by silicon anodes in lithium-ion batteries, this review comprehensively discusses various coating materials and the related synthesis methods. In this review, the electrochemical properties of silicon-based anodes are outlined according to the application of various coating materials such as carbon, inorganic (including metal-, metal oxide-, and nitride-based) materials, and polymer. Additionally, double shells introduced using two materials for double coatings exhibit more complementary electrochemical properties than those of their single-layer counterparts. The strategy involving the application of a coating is expected to have a positive effect on the commercialization of silicon-based anodes.

Title: Study of Structural Evolution of Silicon-Based Anodes in Lithium-Ion Batteries

The need for electrification across various sectors has led to increased demand for high-performance lithium-ion batteries (LIBs). Today’s commercial LIBs typically make use of a pure-graphite anode which offers long lifespans but a relatively meager capacity of 372 mAh/g. Silicon, by comparison, offers a theoretical capacity of 3600 mAh/g but generally suffers from short life spans due to numerous effects. Combining silicon and graphite active materials to form a composite anode can result in electrodes with improved capacities over pure-graphite systems and enhanced longevity over pure-silicon ones. However, introducing silicon to an otherwise stable graphite electrode can induce failure of the electrode partly due to the volumetric expansion/contraction that silicon experiences during lithiation/delithiation cycles. Understanding the morphological evolution of silicon particles in composite electrodes - particularly in a lithiated state - can yield a more comprehensive understanding of the interactions between the active materials which will contribute to the realization of anodes with improved capacities and lifespans. To date, characterizing lithiated silicon-containing anodes has been difficult owing to the reactivity of the lithiated materials and a lack of suitable methods to probe within an electrode’s bulk. In this work, we demonstrate recent successes in imaging lithiated silicon-composite and silicon oxide-composite electrodes via micro and nanoscale computed tomography (MicroCT, NanoCT) and electrochemical analysis to quantify (1) changes in particle size distributions over charge/discharge cycles, (2) lithium content in silicon particles as a function of depth from the electrode’s surface, (3) changes in particle morphology, and (4) electrode thickness. The development of this technique represents a significant step towards characterizing the physical behavior of silicon particles within electrodes without destroying the surrounding structures.

Porous carbon-coated silicon composites for high performance lithium-ion batterie anode

With the rapid development of silicon-based lithium-ion battery anode, the commercialization process highlights the importance of low-cost and short-flowproduction processes. The porous carbon/silicon composites (C/Si) are prepared by one-step calcination using zinc citrate and nano-silicon as the primary raw materials at a temperature of 950 °C. In this composite, silicon nanoparticles are coated with a porous carbon shell with an average pore diameter of 4.49 nm, which improves the structural stability and electrochemical performance of the anode. Density-functional theory calculations show that the porous carbon enhances the electrical conductivity, facilitates the interlayer migration of Li-ion, and strengthens the gain effect of stress on conductivity. Additionally, stress further reduces the diffusion barriers of Li-ion. The porous C/Si anode demonstrates outstanding specific capacity and rate capability, maintaining a stable specific capacity of 1170 mAh/g at a current density of 0.2 A g−1 after 100 cycles and retaining a reversible specific capacity of 944 mAh/g even at a charging current density of 2 A g−1. The carbon/silicon anode materials prepared using this strategy present a streamlined manufacturing process and exceptional performance, as well as avoiding the post-washing step, providing a pathway toward the scalable application of silicon-based anodes.

Water-soluble binder in high-performance silicon-based anode for lithium-ion batteries based on sodium carboxymethyl cellulose and waterborne polyurethane

Silicon (Si) material has attracted growing attention in lithium-ion batteries (LIBs) due to its remarkably high-theoretical capacity and abundance on Earth. Despite excellent edges, the widespread application of silicon materials...

Recent progress and challenges in silicon-based anode materials for lithium-ion batteries

This review highlights the importance of silicon-based anodes in lithium-ion batteries, emphasizing their improved performance through modifications involving binders, coatings, composites, and electrolytes.

MXene Clay (Ti2C)-Containing In Situ Polymerized Hollow Core-Shell Binder for Silicon-Based Anodes in Lithium-Ion Batteries.

Silicon, an attractive anode material, suffers fast capacity fading due to the electrical isolation from massive volumetric expansion upon cycling. However, it holds a high theoretical capacity and low operation voltage in its practical application. In this study, a new water-based binder, MXene clay/hollow core-shell acrylate composite, was synthesized through an in situ emulsion polymerization technique to alleviate the fast capacity fading of the silicon anode efficiently. The efficient introduction of conductive MXene clay and the hollow core-shell structure, favorable to electron and ion transport in silicon-based electrodes, gives a novel conceptual design of the binder material. Such a strategy could alleviate electrical isolation after cycling and promises better electrochemical performance of the high-capacity anodes. The effect of the MXene introduction and hollow core-shell on the binder performance is thoroughly investigated using various characterization tools by comparison with no MXene-containing, core-shell acrylate, and commercial styrene-butadiene latex binders. Consequently, the silicon-based electrode containing the MXene clay/hollow core-shell acrylate binder exhibits a high capacity retention of 1351 mAh g-1 at 0.5C after 100 cycles and good rate capability of over 1100 mAh g-1 at 5C.

Dual-functional trisiloxane as binder additive for high volume expansion Li-ion battery electrodes

Silicon-based anodes for lithium-ion batteries have the inherent advantage of higher capacity. However, the inherent expansion of Si within the anodes during cycling, causing low battery life, has limited its application. Various approaches are being investigated to mitigate the adverse effects, ranging from the patterned deposition of Si, blending silicon materials with graphite active materials, and using modified polymeric binders. Inspired by the super spreading capabilities of siloxane compounds and with an aim to optimize the graphite-SiO composite electrode, this work focuses on tweaking the binder formulation with a trisiloxane-based additive which enables uniform dispersion of active material within the electrode and enhances the wetting of the electrolyte within the electrode. In this work, graphite with 15 wt% silicon monoxide was used as an electrode with trisiloxane-modified binder showing much improved electrochemical performance with better mechanical integrity compared to the benchmark electrode. The cell with modified binder exhibited remarkable cycling stability up to 400 cycles at 0.2 C-rate. A detailed study on the role of the trisiloxane additives on the physicochemical properties of electrode materials has also been elucidated. The prospects of employing these additives for similar high-volume expansion electrodes are also discussed.

Constructing a conductive and buffer network on microscale silicon-based anodes for high-performance lithium-ion batteries

The structure and characteristics of the electrodes are essential for the performance of microscale silicon-based anodes for lithium-ion batteries. In this study, various carbon sources with different degrees of graphitization, morphologies, and dispersities were utilized as conductive agents for a microstructured silicon electrode. The findings indicate that micron-sized silicon electrodes can benefit from the addition of flake-conductive graphite, particularly SFG-6, which possesses a high degree of graphitization and dispersion, as well as a particle size similar to that of silicon. This combination results in a well-distributed, uniform conductive and buffering network, leading to improved electrochemical performance overall. After 450 cycles, the Si-SFG-6 composite anode exhibited exceptional long-term stability, delivering a specific capacity of 1102 mA·h g−1 at a current density of 200 mA g−1. Furthermore, even at a higher current density of 2000 mA g−1, the reversible capacity remained impressive at 964 mA·h g−1. The results of this study offer valuable insights for optimizing the structure and properties of microstructured silicon-based anodes, with the aim of achieving superior performance in Li-ion batteries.

Implications of the Thermal Stability of FEC-Based Electrolytes for Li-Ion Batteries

Fluoroethylene-carbonate (FEC) is a common co-solvent for high-voltage cathodes and for silicon-based anodes in lithium-ion batteries. However, FEC has a limited thermal stability when used with LiPF6 as conductive salt, and its decomposition can trigger detrimental side reactions. Here, we will examine the reaction mechanism of FEC with LiPF6, confirming that vinylene-carbonate (VC) and HF are produced at elevated temperatures. By full-cell cycling at 45 °C in a T-cell setup with a micro-reference electrode (μ-RE), we can show by electrochemical impedance spectroscopy that these side reactions not only lead to an impedance increase of the anode and the cathode, but also trigger transition metal dissolution. By comparison of FEC and ethylene-carbonate (EC) as cyclic carbonate, we demonstrate that FEC has no advantage at high-voltage operation compared to EC, when employing cathode materials or cathode potentials for which no lattice oxygen is evolved. Finally, we use multi-layer pouch-cells to analyze the gassing of an EC- and FEC-based electrolyte upon extended charge/discharge cycling at 45 °C, showing that the latter leads to cell bulging upon extended charge/discharge cycling at 45 °C due to the oxidation of the VC formed by the thermal decomposition of FEC above ≈4.4 − 4.5 V vs. Li+/Li.

Investigation of Xanthan Gum and Carboxymethyl Cellulose Binders for the Silicon Anode of Lithium-Ion Batteries

The binder is known to play an important role in the cycle stability of silicon-based anodes for lithium-ion batteries. Nature-derived biopolymers such as sodium carboxymethyl cellulose (NaCMC) and xanthan gum (XG) are a promising class of binders that offer several advantages over traditional polyvinylidene fluoride (PVDF). Advantages include better contact between silicon particles and the ability to process the electrodes using water as a solvent. While many studies have explored the fundamental properties of these biopolymer binders and their interaction with silicon, there has been little research on the use of these binders under practical loadings (such as ∼2 mg Si cm−2 and <10 wt% binder). Herein, we compare the electrochemical performance of both NaCMC and XG-based silicon electrodes with a low binder content. Si-binder interactions and their role in electrode performance are revealed with XPS, SEM, and EDX. In addition, we report the results of both a high-silicon (80 wt% Si) and a practical low-silicon (20 wt% Si) composite electrode while using silicon nano powder prepared by industrial-scale synthesis. It is found that NaCMC consistently outperforms XG as a binder, which is attributable to superior cohesion within the electrode.

Research Progress of Functional Binders in Silicon-Based Anodes for Lithium-Ion Batteries

Research Progress of Functional Binders in Silicon-Based Anodes for Lithium-Ion Batteries

Development of Silicon-Based Anode for Lithium-Ion Batteries and Its Application in Solid-State Electrolytes

Yifei Zhou1, Wenfan Feng1, Yanbin Xu*,1, Xingang Liu1, Shuai Wang1, Zhiqiang Lv1, Xiao Li1, Ethan Burcar2, Zhe Wang*,2 and Zhenglong Yang*,1 1. School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China 2. Chemistry Department, Oakland University, Rochester, MI, 48309, USA

Effects of transition metals for silicon-based lithium-ion battery anodes: A comparative study in electrochemical applications

The strength, conductivity, elasticity, inactivity against lithium, and tunability properties of transition metals (TMs) are the major reasons these metals are used to synthesize silicon-based lithium-ion battery (LIBs) composite anodes. This is because TMs significantly influence and improve the overall electrochemical performance of LIB electrodes by mitigating the undesired expansion of silicon. The effects of different elemental transition metals copper (Cu), titanium (Ti), nickel (Ni), and iron (Fe) on the electrochemical performance of silicon-based composites were compared, and the phases formed during milling were correlated to the behavior of the composites in which they are present. The excellent performance of these electrodes was attributed to the reaction mechanism of transition metals after the first conversion reaction during lithiation and remained inactive during the ensuing cycles. It was found that the strength and ductile nature of nickel accounts for relieving mechanical stress induced on Silicon during the insertion and extraction of lithium ions. All copper-containing composites showed high stability in cycling but low capacity, which is attributed to the high amounts of copper, contained in these composites and the reaction of copper with silicon during milling. The presence of titanium improved the electrical conductivity and mechanical strength of the electrodes. Iron-containing composites were observed to highly withstand deformation due to the strength of the matrix. Moreover, the addition of 10 wt. percentage carbon improved the cycle performance and rate capability of Cu-Fe-Si-C, Cu-Ni-Si-C, Ni-Fe-Si-C, and Ni-Ti-Si-C. These composites showed stable cycling performance of 654.42 mAh g–1, 686.16 mAh g–1, 657.56 mAh g–1, and 643.29 mAh g–1 respectively after 100 cycles capacity at 1 C.

Graphene supported double-layer carbon encapsulated silicon for high-performance lithium-ion battery anode materials

Carbon coating has been an effective procedure to tackle the severe structural degradation and poor conductivity during cycling of silicon-based anodes in lithium-ion batteries (LIBs). However, the traditional coated carbon usually is tight and thus limit the fast-charging rate and high specific capacity. Herein, through in-situ formation of metal-organic frameworks on the surface, silicon particles were firstly coated by an inside carbon layer. Followed by a solvothermal reaction with the mixture of sucrose and graphene oxide, the second carbon layer outside the silicon particles was deposited, and simultaneously a highly conductive graphene network was formed. After a high temperature pyrolysis process, a graphene matrix supported silicon material with inward multi-channel carbon and outward tight activated carbon was prepared. This unique core/double-layer carbon structure, combined with the highly conductive graphene frameworks, render the material to demonstrate excellent electrochemical performance as anode materials for LIBs in terms of both lithium storage capacity and cycling stability. Thus, the electrode materials deliver a high specific capacity of 1528.1 mA h g−1 at the current density of 0.1 A g−1 and rate capacity retention of 45.5% at 1 A g−1 to 0.1 A g−1. Simultaneously, a highly stable reversible capacity of 1182 mAh g−1 with 89.5% retention over 240 cycles at a current density of 0.2 A g−1 and 484 mAh g−1 with 76.8% retention after 450 cycles at 1.0 A g−1 were obtained. This work can offer an alternative approach for high-energy and low-cost silicon-based anodes for LIBs.

Optimizing Aqueous Binders for Next-Generation Lithium-Ion Batteries: A Practical Approach

The demand for lithium-ion batteries continues to grow as the need for renewable energy increases. Over the past few decades, lithium-ion batteries have seen widespread adoption in portable electronics, and they are increasingly being used in electric vehicles. To satisfy the energy density needed for these next-generation applications, new anode materials with high-energy densities are required. Traditional graphite is a very stable intercalation-based anode, but its low capacity has driven many researchers to identify alternatives. Silicon (Si) has one of the highest gravimetric energy densities known when alloyed with lithium. Unlike graphite which is limited to 1 lithiumion per 6 carbon atoms (LiC6), the lithium-silicon alloy Li15Si4 has nearly 4 lithium ions per silicon atom. This gives silicon a theoretical capacity of 3579 mAh/g, compared to the 372 mAh/g for graphite. However, the challenge with silicon (and most alloy anodes) is its poor stability— as the alloying of lithium and silicon is accompanied with a 300% volume expansion. On a microscopic scale, this causes material/electrode swelling and pulverization, which in turn causes severe capacity fade in a few cycles.The binder is known to play an important role in the cycle stability of silicon-based anodes for lithium-ion batteries. Polyvinylidene fluoride (PVDF) has traditionally been the binder used in the preparation of both graphite anodes and lithium metal oxide cathodes. It is electrochemically stable; that is, it is not reduced at the low potential of the anode (~5 mV vs Li) and is not oxidized at the high potential of the cathode (5 V vs Li). However, PVDF has three main disadvantages. First, PVDF cannot accommodate the large volumetric expansion of silicon lithiation. As a result, batteries using PVDF as a binder with silicon will experience a very rapid drop in capacity. Second, PVDF is not water soluble and requires the use of organic solvents like N-Methyl-2-pyrrolidone (NMP) during electrode processing. Finally, the cost of PVDF is approximately 20 USD/kg, which is several times greater than competing binders like sodium carboxymethylcellulose (NaCMC) at 6 USD/kg.Next-generation binders should be inexpensive, able to accommodate the expansion of silicon, and use environmentally friendly processing. Natural biopolymers (such as NaCMC and xanthan gum XG) are a promising class of binders that offer several advantages over traditional polyvinylidene fluoride (PVDF). Biopolymers contain many carboxylate and hydroxyl functional groups which aid in the formation of noncovalent bonding with the oxide surface of silicon. In particular, xanthan gum is a high molecular weight polysaccharide produced extracellularly by the bacteria Xanthomonas campestris. It is water soluble and thus eliminates the need for organic solvents. In addition, its high molecular weight is known to provide better capacity retention, owing to the long molecular chains that can accommodate silicon expansion. While existing studies have explored the fundamental properties of these biopolymer binders and their interaction with silicon, there has been little research on the use of these binders under realistic processing conditions (≤ 10 wt% binder). Herein, we optimize the electrochemical performance of both NaCMC and XG-based silicon electrodes with a low binder content. In addition, we report results for both a high-silicon (≥80 wt%) and a practical low-silicon (20 wt%) composite, all while using nano silicon prepared by industrial-scale synthesis. Figure 1 below shows the capacity retention of different electrode preparations. A higher initial capacity is expected with 80% silicon. However, the overall stability is superior for the low silicon-high graphite (G) composites. Keywords: high-capacity anodes; binders; biopolymers; silicon; lithium-ion batteries Figure 1. Capacity vs cycle number for 1st Generation Si-based electrodes. Cycled at C/10. References H. Yim, S. Niketic, N. Salem, O. Naboka, and Y. Abu-Lebdeh, J. Electrochem. Soc., 164, A6294–A6302 (2017).Zhao, S. Niketic, C. H. Yim, J. Zhou, J. Wang, and Y. Abu-Lebdeh, ACS Omega, 3, 11684–11690 (2018).M. Courtel and Y. Abu-Lebdeh, “Use of Xanthan Gum as an Anode Binder,” Patent 10,483,546 B2, 2019.Li, Z. G. Wu, Y. M. Liu, Z. W. Yang, G. K. Wang, Y. X. Liu, Y. J. Zhong, Y. Song, B. H. Zhong, and X. D. Guo, Ionics (Kiel)., 27, 1829–1836 (2021). Figure 1

A dual force cross-linked γ-PGA-PAA binder enhancing the cycle stability of silicon-based anodes for lithium-ion batteries

Silicon (Si) is considered to be one of the most suitable anode materials for high energy density lithium-ion batteries due to its high theoretical specific capacity. However, the practical application of Si anode is limited by its huge volume change, leading to the rupture of electrode during cycling. In this study, a natural polymer of poly-glutamic acid ( γ -PGA) is derived from nattomycin gum and poly-acrylic acid (PAA) through thermal cross-linking method and served as a dual force cross-linked binder. The two polymers are firmly bonded by dehydration to form the cross-linked γ -PGA-PAA binder with stable ester bonds, which readily creates hydrogen bonding forces with the hydroxyl groups on Si surface. The γ -PGA-PAA exhibits robust mechanical properties to achieve excellent electrochemical performance of Si-based electrode. When the γ -PGA-PAA is used as binder of Si nanoparticle anodes, the capacity retention of Si/ γ -PGA-PAA electrode can reach 63.1% after 300 cycles at charge/discharge current density of 420 mA g −1 with a mass loading of about 0.7 mg cm −2 . As a comparison, the capacity retentions of the Si/PAA and Si/ γ -PGA electrodes are respectively 8.7 and 17.9% under the same conditions. At higher current density of 2940 mA g −1 , the capacity retention of Si/PAA electrode has dropped dramatically to 23.3%, and the Si/ γ -PGA-PAA electrode keeps still high-capacity retention of 72.5% after 400 cycles, while the Si/ γ -PGA electrode can only last 40 cycles. When the three binders are applied to SiO electrode with 1 mg cm −2 loading, the γ-PGA-PAA binder yields also the highest capacity retention of 87.3% after 100 cycles at 160 mA g −1 , while those corresponding to PAA and γ-PGA binders are 81.3% and 74.9%, respectively. XPS characterization results indicate that the γ -PGA-PAA binder has a strong adhesion to Si particles. This cross-linked binder network of γ -PGA-PAA effectively enhances the cycling performance and maintains the structural integrity of Si and SiO electrodes.

Protective Coating Layers via Phosphazene Compounds for Stabilizing Silicon Anode Materials

In recent years, lithium-ion batteries (LIBs) are widely used in electric vehicles (EVs) and mobile energy storage devices (ESDs), which has led to higher requirements for energy density. To fulfill these requirements, tremendous attention has been paid to design advanced LIBs with various silicon active materials as alternative negative electrodes to replace graphite (372 mAh g-1) due to their high theoretical gravimetric capacity (4200 mA h g-1).[1,2] However, silicon as potential anode material suffers from huge volume changes during charging and discharging and has a poor electronic conductivity which negatively impacts the long-term performance and prevents high silicon contents from practical application.[3] Additionally, an unstable crystalline silicon structure tends to pulverization during the (de)lithiation process.[4] To compensate the volume changes, alleviate pulverization and maintain high electronic conductivity, silicon-doped graphite composites with protecting coating layers are a promising approach. In this context, phosphazene compounds are investigated concerning their silicon protecting properties in silicon-doped graphite composites. In detail electrochemical performance measurements in pouch full-cells (NCM523||SiOx/C), supressing gas formation properties and post-mortem analyzes were carried out to characterize phosphazene compounds as additive materials. The introduction of the dual-additive approach in state-of-the-art electrolytes leads to synergistic effects between FEC and phosphazene compounds which accelerate the durability of silicon particles and results in enhanced electrochemical performance. Reference: [1]Zuo X, Zhu J, Muller‐Buschbaum P, Cheng Y, Silicon based lithium‐ion battery anodes: a chronicle perspective review, Nano Energy, 2017, 31, 113‐143.[2]Jimenez A. R., Klöpsch R., Wagner R., Rodehorst U. C., Kolek M., Nölle R., Winter M., Placke T., A step toward high-energy silicon-based thin film lithium ion batteries, ACS Nano, 2017, 11, 5, 4731-4744.[3] Berla A. L., Lee S. W., Ryu I., Cui Y., Nix W. D., Robustness of amorphous silicon during the initial lithiation/delithiation cycle, Journal of power sources, 2014, 258, 253-259.[4] Casimir A., Zhang H., Ogoke O., Amine J. C., Lu J., Wu G., Silicon-based anodes for lithium-ion batteries: Effectiveness of materials synthesis and electrode preparation, Nano Energy, 2016, 27, 359-376.

3D Printing of Silicon-Based Anodes for Lithium-Ion Batteries

In order to meet the target for the next generation lithium-ion batteries, electrochemical performance such as energy and power density must be increased significantly at the same time. Optimized electrode architectures including 3D battery concepts and advanced materials are in development to achieve this goal. The use of silicon-graphite composite electrodes instead of graphite anodes is currently investigated. This is due to the fact that silicon can provide almost one order of magnitude higher specific energy density (3579 mAh/g) in comparison to natural graphite (330 - 372 mAh/g). However, during lithiation, i.e., lithium silicide formation, a volume expansion of about 300 % can take place, while during lithium intercalation in graphite about 10 % volume expansion can be observed. A huge volume expansion leads to a tremendous mechanical degradation of the anode resulting in a drop in capacity, and a limited battery lifetime.In the presented study, laser induced forward transfer (LIFT) is applied as printing technology to develop sophisticated graphite and graphite-silicon electrode architectures with advanced electrochemical performances. LIFT was performed using a pulsed nanosecond UV laser with a repetition rate of up to 30 kHz and a maximal power of 10 W. To enable an accurate printing process during LIFT, the properties and compositions of the active material inks as well as the laser and process parameters have to be optimized. The printing process in combination with laser structuring provides a high flexibility regarding the final electrode design. In the presented study, the formation of multi-layer electrodes with spatial variation in electrode composition is achieved. As active materials silicon nanoparticles (SNPs) and various types of graphite, i.e., natural graphite, mesocarbon microbeads (MCMB), and artificial flake-like graphite with an average particle diameter of 1 µm up to 15 µm are utilized. The geometry and thickness of each printed layer is adapted with regard to an optimized electrochemical performance and cell lifetime. A single layer thickness of 5 µm up to 20 µm was achieved, while areal capacities of multi-layer anodes reaches values of 2 to 4 mAh/cm². In addition to the applied active materials and architecture concepts, different solvent and binder systems are investigated with regard to process scalability and an improved environmental compatibility. The printed electrodes are electrochemically characterized by rate capability measurements at C-rates of up to 5C. A correlation between capacity retention and electrode architecture is achieved. The results are discussed in terms of upscaling and impact on the next generation anode material.

Carboxymethylated tamarind polysaccharide gum as a green binder for silicon-based lithium-ion battery anodes

Binders pave the way for silicon (Si)-based lithium-ion batteries (LIBs) by alleviating excessive expansion of Si and offer an intriguingly high theoretical specific capacity (4200 mAh g−1), even with small amounts of additive. Here, we report a novel aqueous binder, carboxymethylated tamarind polysaccharide gum (1-CMT), created by modifying a low-cost, abundant, and non-toxic natural polysaccharide (tamarind kernel powder) under mild conditions. The Si@1-CMT electrode has a satisfactory specific capacity of 3626.7 mAh g−1 as well as a coulombic efficiency of 90.96% at the initial cycle; the Si mass loading is approximately 0.75 mg cm−2. A specific capacity of 1176 mAh g−1 is retained after 200 cycles at a strict current density of 2000 mA g−1; the corresponding value for a Si@CMC electrode is only 697 mAh g−1. The 1-CMT electrode has a specific capacity greater than 1600 mAh g−1 even under a current density of 4000 mA g−1. The unique branched chain structure and substantial number of free polarfunctionalgroups explain the outstanding electrochemical properties. Hence, 1-CMT acts as a premium binder in a Si-based anode that can be used to create high-performance batteries.

Drop-on-demand 3D-printed silicon-based anodes for lithium-ion batteries

Drop-on-demand 3D-printed silicon-based anodes for lithium-ion batteries