Silicon Anodes In Lithium-ion Batteries Research Articles

Eco-Friendly Water-Processable Polyimide Binders with High Adhesion to Silicon Anodes for Lithium-Ion Batteries.

Silicon is an attractive anode material for lithium-ion batteries (LIBs) because of its natural abundance and excellent theoretical energy density. However, Si-based electrodes are difficult to commercialize because of their significant volume changes during lithiation that can result in mechanical damage. To overcome this limitation, we synthesized an eco-friendly water-soluble polyimide (W-PI) precursor, poly(amic acid) salt (W-PAmAS), as a binder for Si anodes via a simple one-step process using water as a solvent. Using the W-PAmAS binder, a composite Si electrode was achieved by low-temperature processing at 150 °C. The adhesion between the electrode components was further enhanced by introducing 3,5-diaminobenzoic acid, which contains free carboxylic acid (–COOH) groups in the W-PAmAS backbone. The –COOH of the W-PI binder chemically interacts with the surface of Si nanoparticles (SiNPs) by forming ester bonds, which efficiently bond the SiNPs, even during severe volume changes. The Si anode with W-PI binder showed improved electrochemical performance with a high capacity of 2061 mAh g−1 and excellent cyclability of 1883 mAh g−1 after 200 cycles at 1200 mA g−1. Therefore, W-PI can be used as a highly effective polymeric binder in Si-based high-capacity LIBs.

A low-cost and sustainable cross-linked dextrin as aqueous binder for silicon anodes in lithium-ion batteries

Silicon is a promising anode material for lithium-ion batteries (LIBs) because of its impressive theoretical capacity. However, it undergoes severe volume changes in the lithiated state thus limiting its development in LIBs. Herein, a cross-linked dextrin binder is created through in-situ thermal cross-linking of dextrin and the inorganic cross-linker sodium tetraborate decahydrate, which is a cost-effective, “greener” water-soluble binder. This binder can significantly strengthen the adhesion between Si electrode and copper current collector, which is almost three times more effective in adhesion than commercially available CMC binder. Meanwhile, the cross-linked dextrin binder also has superior mechanical properties and is able to well mitigate the huge volume changes upon cycling, consequently achieving an excellent cycling stability and superior rate capability. It is believed that this aqueous binder has the potential to utilize in silicon anodes for high-energy-density LIBs, as well as providing a new idea in the design of binders for other electrode materials which suffer from volume change during cycling.

Bifunctional hydrogen-bonding cross-linked polymeric binders for silicon anodes of lithium-ion batteries

The optimization of polymeric binders has been considered as an effective strategy to accommodate the huge volume change of Si anodes during lithiation and delithiation processes. In this work, three dimensional polymeric binders (CMC/TU) with multiple hydrogen bonds were designed and fabricated through the copolymerization reaction between carboxymethylcellulose sodium (CMC) and thiourea (TU), which possess bifunctional effects on Cu current collectors and Si active materials. On the one hand, similar to the interaction mechanism at rubber-metal boundary in tire industry, the formation of dendritic CuxS layers results in physical interlocked forces to strengthen the binding forces of CMC/TU binders with Cu current collectors. On the other hand, the generation of hydrogen bonds between polymeric binders and Si oxide layers can enhance the binding forces of CMC/TU binders with Si active materials and stabilize the electrode/electrolyte interface. When served as binders to Si microparticles (1–5 μm), they exhibited initial coulomb efficiency of 89.9% and reached 1059 mAh g−1 after 150 cycles, which results from the bifunctional roles of CMC/TU binders for maintaining electrode integrity during the discharge and charge processes. The developed synthetic method provides a strategy to enhance the electrochemical properties of Si-based materials, and can be widely applied to other electrode materials.

In Situ Room-Temperature Cross-Linked Highly Branched Biopolymeric Binder Based on the Diels-Alder Reaction for High-Performance Silicon Anodes in Lithium-Ion Batteries.

Silicon (Si) is an auspicious anode material in next-generation lithium-ion batteries due to its exceptional theoretical gravimetric capacity, environmental friendliness, and high natural abundance. However, the practical application of Si anodes remains a "must-solve" challenge because of its drastic capacity fading that results from the inherent property of drastic volume expansion of Si during repeated lithiation and delithiation. Developing binders employed in robust electrodes has been considered an economical and practical method to affect the electrochemical performance of Si-based electrodes. Some natural polymers have demonstrated good adhesive properties with Si-active materials. However, they have limited capacity to keep the structural integrity of electrodes because the network structures solely based on weak hydrogen bonds are susceptible to deformation during cycling. Herein, we develop an in situ covalently cross-linked three-dimensional (3D) supramolecular network and apply it to the Si electrode to improve cycling performance. This network architecture is constructed using furan-modified branched arabinoxylan of corn fiber gum (CFG) and an ionically conductive cross-linker of maleimido-poly(ethylene glycol) (PEG) through the Diels-Alder reaction. The maleimide groups in PEG can react spontaneously with the furan groups in CFG at room temperature without any other stimulation, thus forming strong covalent bonds in the network. The cross-linked CFG-PEG binder has demonstrated robust adhesive properties with Si-active materials and the current collector. The branching of CFG and functional groups of PEG are conducive to improving the lithium-ion conductivity in the silicon anode, resulting in excellent rate performances. The Si anode with a cross-linked CFG-PEG binder exhibits superior cycling stability. As a result, an in situ cross-linking 3D network as a novel binder has a great potential for fabricating an advanced Si anode in next-generation Li-ion batteries.

Utilizing a Novel Electrolyte Additive for Improvement of the Solid Electrolyte Interphase on Silicon Anodes of Lithium-Ion Batteries

Graphite is currently the most widely used anode material in lithium-ion batteries due to its layered structure and long cycling stability. However, any lithium-ion batteries built with graphite are inherently limited by graphite’s moderate theoretical capacity of 372mAh/g and subsequent low energy density. A more promising anode material is silicon due to its significantly higher theoretical capacity of 3579mAh/g, creating a much higher energy density. Unfortunately, silicon experiences large volume changes during cycling that causes the pulverization of active materials, thus fracturing the electrode surface and reducing electrical conductivity. The constant morphology changes furthermore damage the formation of a stable solid electrolyte interphase (SEI) on the silicon particles, causing continuous consumption of electrolyte and thickening of the SEI layer. These all contribute to rapid capacity decay and short cycle life. One way to improve the cycling performance of silicon anodes is to include electrolyte additives like fluoroethylene carbonate (FEC) that preferentially reduce on the surface of the anode. These additives enable the ability to develop a more robust and flexible passivation film that can accommodate electrode expansion. In this study, a novel electrolyte additive formulation was used to improve the long-term cycling stability of silicon anode half cells. The resultant SEI layer was characterized using X-ray photoelectron spectroscopy and attenuated total reflectance infrared spectroscopy as well as examined using scanning electron microscopy for morphology changes.

Effect of Temperature on Silicon-Based and Silicon-Rich Anodes for Li-Ion Batteries

Several governments are committed to fight against climate change and, reducing the pollution derived from the utilization of fossil fuel powered cars is considered as a part of the solution. Therefore, environmentally friendly electric vehicles (EVs) keep on gaining importance [1], [2] . Nevertheless, in order to extend the autonomy range of EVs to that achieved by internal combustion cars, next-generation lithium-ion batteries (LIBs) with larger specific capacities and subsequent higher energy densities are required.Replacing graphite, the anode widely used in current LIBs, with other materials capable of providing much larger capacities, is a well-known strategy to boost the specific capacity of this technology [3], [4] . In this sense, silicon is one of the most promising materials, not only because it can deliver a capacity (~3579 mAh/g) approximately 10 times that of graphite (~370 mAh/g) [5], [6] , but also because it is an affordable substitute anode material for LIBs, since it is the second most abundant element in the earth’s crust [7] .Numerous scientific investigations have been carried out in silicon anodes for LIBs, however, a parameter that has not been assessed and would be crucial in its real performance in EVs is the effect that temperature would have over its cyclability. To determine such effect, we have conducted galvanostatic tests with silicon-based and silicon-rich anodes in half-cells at different temperatures. Besides, the absence or presence of fluoroethylene carbonate (FEC) as electrolyte additive has also been evaluated. The different capacities and cycle-lifes observed, along with the possible kinetic mechanisms behind them, will be here discussed. We gratefully acknowledge support from the U. S. Department of Energy (DOE), Vehicle Technologies Office. Argonne National Laboratory is operated for DOE Office of Science by UChicago Argonne, LLC, under contract number DE-AC02-06CH11357. The U.S. government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the government. [1] M. Armand and J-M. Tarascon. Nature 2008, 451, 652-657. Building better batteries. [2] C. C. Chan. EEE 1999 International Conference on Power Electronics and Drive Systems, PEDS’99, Hong Kong. The Past, Present and Future of Electric Vehicle Development. [3] W-J. Zhang, J. Power Sources 2011, 196 (1), 12-24. A review of the electrochemical performance of alloy anodes for lithium-ion batteries. [4] V. Etacheri, R. Marom, R. Elazari, G. Salitra and D. Aurbach. Energy Environm. Sci. 2011, 4, 3243-3262. Challenges in the development of advanced Li-ion batteries: a review. [5] X. Su, Q. Wu, J. Li, X. Xiao, A. Lott, W. Lu, B. W. Sheldon and J. Wu. Adv. Energy Mater. 2014, 4, 1300882. Silicon-Based Nanomaterials for Lithium-Ion Batteries: A Review. [6] H. Wu and Y. Cui. Nanotoday 2012, 7(5), 414-429. Designing nanostructured silicon anodes for high energy lithium ion batteries. [7] U. Kasavajjula, C. Wang and A. J. Appleby. Journal of Power Sources 2007, 163, 1003. Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells.

Xylitol-Maleic Anhydride as Small-Molecule Binders for Silicon Anodes in Lithium-Ion Batteries

The theoretical capacity (∼4200 mAh g−1) of silicon (Si) electrode is almost tenfold higher than that of commercially available graphite. However, the cycle-life performance of the Si electrode is poor. Herein, small molecules, sugar alcohol (xylitol) and maleic anhydride, are used as an aqueous binder to obtain high-performance Si electrodes. The xylitol-maleic anhydride (X-MA) binder is in situ polymerized by esterification of maleic anhydride with xylitol and oxa-Michael addition of an α,β-unsaturated ester with hydroxyl groups of xylitol during the preparation of slurry and the drying of electrode. The X-MA binder is characterized by Fourier-transform infrared and solid-state 13C nuclear magnetic resonance spectroscopy, confirming that the esterification and oxa-Michael addition reactions occur during the fabrication of Si electrodes. The results of thermogravimetric analysis and differential scanning calorimetry show that X-MA has good thermal stability and is an elastomer. The 180° peeling test results indicate that the presence of hydroxyl groups in the xylitol moiety results in a strong interaction between the binder and Si nanoparticles, improving the mechanical properties of the Si electrode. Furthermore, the Si electrode with the X-MA binder exhibits a high energy capacity of 4012 mAh g−1 at 0.1 C, enhanced C-rate performance, and good cycle-life performance.

A novel functional polymeric binder for silicon anodes in lithium-ion batteries

Si is known to have an extremely high theoretical capacity and regarded as an optimal anode candidate for the next-generation LIBs. But unfortunately, the dramatic volume change during repeated charge/discharge processes leads to its repaid capacity fading. Here we report a novel composite functional binder, which is constructed by cross-linking PEDOT: PSS and CMC by C-O-S bonds. The obtained polymeric binder features superb electrical conductivity, strong interactions (hydrogen bonds) between binder and Si surface and robust mechanical strength through cross-linking, thus the structural and electrochemical properties of the Si anode was dramatically improved, including the smooth electrode surface and the low electrode expansion rate after repeated cycles, as well as the high initial capacity (3892 mAh·g-1) and coulomb efficiency (81%), the excellent capacity retention (1106.4 mAh·g-1 after 100 cycles) and rate capability (600 mAh·g-1 at 5 A·g-1).

A Novel Tin-Bonded Silicon Anode for Lithium-Ion Batteries.

Poor cyclic stability and low rate performance due to dramatic volume change and low intrinsic electronic conductivity are the two key issues needing to be urgently solved in silicon (Si)-based anodes for lithium-ion batteries. Herein, a novel tin (Sn)-bonded Si anode is proposed for the first time. Sn, which has a high electronic conductivity, is used to bond the Si-anode material and copper (Cu) current collector together using a hot-pressed method with a temperature slightly above the melting point of Sn. The cycling performance of the electrode is studied using a galvanostatic method. Nanoindentation and peeling tests are conducted to measure the mechanical strength of the electrodes. Direct current polarization and galvanostatic intermittent titration techniques are applied to assess the conductivity of the composites. Electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy are conducted to evaluate the effect of the coating layer on the cycling ability of the composites. The Sn-bonded Si anodes show superior cycling stability and high rate performance with an improved initial Coulombic efficiency. Analyses reveal that the low-melting-point Sn helps to markedly improve the electronic conductivity of the electrodes and serves as a metallic binder as well to enhance the adhesive strength of the electrode. It is hopeful that this novel Sn-bonded Si anode provides a new insight for the development of advanced Si-based anodes for LIBs.

Multiple Network Binders via Dual Cross-Linking for Silicon Anodes of Lithium-Ion Batteries

Multiple Network Binders via Dual Cross-Linking for Silicon Anodes of Lithium-Ion Batteries

Enhancing the electrochemical performance of silicon anodes for lithium-ion batteries: One-pot solid-state synthesis of Si/Cu/Cu3Si/C electrode

To obtain Si anodes with high-performance Li-ion batteries, a nanostructured Si-based composite is synthesized via a facile one-pot solid-state reaction. The Si-based anode composed of Si, Cu, and polyvinylidene fluoride (PVDF) binder is heated at 500 °C under continuous argon flow to obtain a Si/Cu/Cu3Si/C (SCCC) anode. The Cu/Cu3Si phases and carbonized PVDF provide conductive pathways between active Si particles, improving electrical conductivity. In addition, Cu3Si phases form between Si and Cu, anchor metallic Cu in Si particles and help to maintain electronic conductivity and alleviate mechanical stress during cycling. As a result, the SCCC anode shows significantly enhanced electrochemical properties. It delivers 1,773 mAh g−1 after 300 cycles at a current density of 2 A g-1, whereas the Si anode exhibits close to zero capacity. The improvements in electrochemical performance are ascribed to reduced internal resistance and mechanical stress resulting from the Cu/Cu3Si phases and carbonized PVDF binder.

Dopamine-modified carboxymethyl cellulose as an improved aqueous binder for silicon anodes in lithium-ion batteries

The intractable issues of silicon anodes hinder its wide application in high-capacity Li-ion batteries. Binders are proven to be one of the effective ways to enhance the electrochemical performance of Si anodes. Inspired by mussels, the water soluble binder carboxymethyl cellulose (CMC) is modified through amidation reaction, and the dopamine moieties are successfully introduced into the polymer backbone of CMC. The dopamine-modified CMC (CMC-DOP) is confirmed by liquid 1H nuclear magnetic resonance (1H NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The CMC-DOP with polar catechol groups and affluent anchoring points exhibits higher adhesive force and superior electrochemical performance. The Si @ CMC-DOP electrode delivers a high initial specific capacity of 3418.2 mAh g−1 and maintains satisfactory capacity of 1650.6 mAh g−1 after 200 cycles. Furthermore, the tight wrapping/coating effect of CMC-DOP binder can effectively protect the active material from exposure to electrolyte, and reduce the decomposition of electrolyte as well as the massive formation of solid electrolyte interface (SEI) layers. The Si electrode with CMC-DOP binder shows slight polarization and intact structure in long-term cycling.

A highly crosslinked polymeric binder for silicon anode in lithium-ion batteries

Silicon as the anode materials had great development prospect in lithium-ion batteries owing to its high capacity. However, during the cycling process, silicon anode’s huge volume expansion would cause the material's severe crushing and disintegration. In order to effectively limited its volume expansion, designed a new highly crosslinked binder, Synthesis of Oxidized Starch (OS) and Polyacrylic Acid (PAA) by crosslinked esterification reaction, and used to reduce the negative effects of Si electrode in the cycling process. Compared to the polyacrylic acid (PAA) binder, the crosslinked polymer binder could effectively increase the Silicon anode’s electrochemical performance. The initial specific discharge capacity and coulomb efficiency of the crosslinked polymer binder electrode were 3441.7 mA h g−1 and 62.39 %, while those of the polyacrylic acid (PAA) binder electrode were only 3526.9 mA h g-1 and 53.59 %. At the current density of 200 mA g-1 after 100 cycles, the discharge capacity and capacity retention of the electrode with the crosslinked polymer binder was 1386.2 mA h g−1 and 40.28 %, greater than those of the electrodes with polyacrylic acid (1068.1 mA h g−1/30.28 %). This solution provided a design of new crosslinked polymer binder, which could be used for the pragmatic application of the anode material with large volume variation.

Structure and Stability of the Solid Electrolyte Interphase on Silicon Anodes of Lithium-Ion Batteries

The solid electrolyte interphase (SEI) acts as a protection layer on the surface the anodes of lithium ion batteries to prevent further electrolyte decomposition. Understanding the fundamental properties of the SEI is essential to the development of high capacity silicon anodes. However, the detailed mechanism of the generation of the evolution of the SEI on the silicon anodes is not fully understood. This manuscript reviews our recent investigations of the SEI on silicon anodes. We have studied the fundamental formation mechanism of the SEI on silicon anodes, along with the evolution which occurs to the SEI upon cycling.

Design of high-energy-dissipation, deformable binder for high-areal-capacity silicon anode in lithium-ion batteries

• The efficient energy-dissipation binder is harnessed on silicon anodes. • A synergized static and dynamic strategy is used to release the stress. • The mechanism is clarified by in-situ IR and finite element simulations. • Unprecedented cycling performances are achieved at high areal capacity. Although silicon has the highest theoretical capacity among the existing anode materials, its practical application is highly hindered by huge interface stress arising from large volume change upon cycling. Herein, an efficient energy-dissipation engineering was harnessed on high-capacity silicon anodes through a synergized “static” (chemically crosslinking) and “dynamic” (physically crosslinking) binder. In this dual network, the disassociation of non-covalent hydrogen bonds greatly facilitates the dispersion and release of unfavorable stress, while the permanent chemical bonding network enables a deformable network to sustain the electrode structure. Such a strategy effectively avoids both materials and electrodes deterioration and promises a better Si-based anode: a high areal capacity of 2 mAh cm −2 with capacity retention of 91.3% after 200 cycles. Meanwhile, the energy-dissipation mechanism was further clarified by temperature-dependent FTIR and finite element simulations.

Polysaccharide-based self-healing polymer binder via Schiff base chemistry for high-performance silicon anodes in lithium-ion batteries

The use of crosslinked glycol chitosan (GCS) is explored as an efficient, low-cost, eco-friendly, and water-soluble polymer binder for Si anodes in lithium-ion batteries (LIBs). A supramolecular, self-healing 3D network is constructed between the amino groups in glycol chitosan and the dialdehyde groups of oxidized alginate (OSA) through dynamic Schiff base reactions. The oxidized alginate crosslinker spontaneously reacts with the natural polymer to form an imine bond, which leads to the formation of a supramolecular network. This mechanism provides this polymer binder with strong and dynamic covalent bonding for Si anodes (GCS-I-OSA), which can effectively buffer the large volume changes in Si that occur during the lithiation/delithiation process. The obtained GCS-I-OSA-10 binder-based Si anode exhibited excellent electrochemical performance, with a high degree of reversibility (2316 mAh g−1 at 0.2 C after 100 cycles). In addition, the GCS-I-OSA-10 electrode exhibited excellent rate performance, achieving high reversibility (2185 mAh g−1 at a high current density of 5C) and high long-term cycling stability (1507 mAh g−1 after 200 cycles), even at a high current density (1C). Moreover, even when applied to commercial Si/graphite composite anodes, this GCS-I-OSA-10 binder was able to deliver superior cycle performance (with a specific capacity of 1364 mAh g−1 at a current density of 0.2 C after 100 cycles), demonstrating excellent potential for practical applications in LIBs.

A carboxymethyl vegetable gum as a robust water soluble binder for silicon anodes in lithium-ion batteries

The dramatic volume change and electrode pulverization hinder the practical utilization of silicon-based anodes for lithium-ion batteries. Studies show that binders can be an effective approach to solve these issues. Herein, the natural vegetable gum-guar gum (GG) is modified through carboxymethylation method. The carboxymethyl guar gum (CMGG) exhibits rapid water solubility, excellent thermal stability, high viscosity and robust adhesion. When it is applied as a binder for silicon anodes, the CMGG possessing affluent hydroxyl and carboxyl groups can effectively accommodate the significant volume variations of silicon particles through the formation of intensive hydrogen bonds. The Si @ CMGG electrode not only retains a high reversible capacity of 1865 mAh g−1 after 200 cycles with a capacity decay rate of 0.12% for each cycle, but also holds a capacity of 1287.1 mAh g−1 after 100 cycles with high mass loading of 1.15 mg cm−2. Furthermore, the CMGG binder can promote the lithium-ion transport like guar gum and reduce the electrode polarization, which is helpful in maintaining the electrochemical stability of Si anodes at high current density.

Dual Cross-Linked Polymer Networks Derived from the Hyperbranched Poly(ethyleneimine) and Poly(acrylic acid) as Efficient Binders for Silicon Anodes in Lithium-Ion Batteries

The condensation of poly(acrylic acid) (PAA) with small amounts of hyperbranched poly(ethyleneimine) (PEI) resulted in the dual cross-linked network cxPAA-PEI(x) (x: wt % of PEI, x = 1, 3, and 5), ...

TEMPO-oxidized cellulose nanofibers as versatile additives for highly stable silicon anode in lithium-ion batteries

Silicon (Si) has been considered the most promising anode material for next-generation lithium-ion batteries due to its high theoretical capacity and natural abundance. However, the Si anode suffers from massive volume change, which results in challenging cycling performance. Many researches demonstrated that polymeric binder plays an important role to sustain the structural integrity of Si anodes. While most studies about the binder material have been focused on enhancing distinctive properties such as adhesive strength and mechanical property, it has been recently shown that binder distribution can help to improve electrochemical performance. Herein, we introduce TEMPO-oxidized cellulose nanofiber (TOCNF) as a versatile additive for the binder of silicon anode. The one-dimensional morphology of TOCNF efficiently reinforces the mechanical properties of the electrode. The TOCNF additive also contains carboxylic groups with sufficient flexibility to induce intimate interaction with Si via hydrogen bonding. Based on all of these beneficial features of TOCNF, the addition of ~ 1 wt% of TOCNF of the whole weight of silicon anode slurry significantly improved cycling stability. With pre-mixing, the resulting Si-TOCNF allows efficient water-based binder solution penetration, thus improving uniform binder distribution of electrode. Furthermore, the well-distributed binder protects silicon surface and forms a stable SEI layer. The current study suggests that the TOCNF additive facilitates uniform binder distribution in the electrode with enhanced mechanical properties, leading to improved cycling performance.

Restorable Neutralization of Poly(acrylic acid) Binders toward Balanced Processing Properties and Cycling Performance for Silicon Anodes in Lithium-Ion Batteries.

Neutralization of poly(acrylic acid) (PAA)-based binders using lithium hydroxide is a common strategy for fabricating silicon anode laminates, which improves rheological properties of slurries toward high-quality electrode laminates. However, the significantly increased basicity causes degradation of Si particles while the irreversible conversion of carboxylic acid groups to lithium carboxylates undermines the binding strength, collectively leading to adverse cycling performance of the fabricated Si anodes. Herein, a novel neutralization process for PAA binders is developed. A weak base, ammonia (NH3), was discovered as a neutralizing agent that still promotes rheological response of binder solutions but results in a reduced pH increase. Interestingly, the resulting ammonium carboxylate groups may cleave during the drying process to restore the neutralized PAA (PAA-NH3) binders to their pristine states. The best-performing composition of 50% neutralization (PAA-50%NH3) provides comparable rheological response as a PAA-Li binder as well as much improved cycling performance. The half-cells using the PAA-50%NH3 binder can deliver 60% capacity retention over 100 cycles at C/3 rate, affording a 23.8% increase compared to PAA-Li half-cells. This restorable neutralization process of PAA binders represents an innovative strategy of mitigating issues from slurry processing of Si particles to achieve concurrent improvements in high-quality lamination and cycling performance.