Dynamically Cross-Linked Polymeric Binder-Made Durable Silicon Anode of a Wide Operating Temperature Li-Ion Battery

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

Silicon (Si) has emerged as a preeminent candidate for next-generation lithium-ion batteries (LIBs) anodes, primarily attributed to its exceptionally high specific capacity. Nevertheless, the substantial volumetric expansion accompanying lithium alloying reactions has long posed a critical challenge to the commercial viability of silicon-based anodes. Binders as connectors between the active Si particles, conductive agents, and current collectors, playing a crucial role in stabilizing the structure of silicon anodes in LIBs. Polyacrylic acid (PAA) water-based binders contain abundant carboxyl groups (─COOH) that can enhance adhesive strength. However, simple linear PAA does not adequately accommodate the significant volume expansion of silicon anodes. To address this issue, various structural optimization strategies have been applied to modify PAA binders. In this context, a comprehensive review is conducted on the recently developed PAA-based binders, which cover linear, branched, and 3D network configurations. A meticulous comparison is carried out regarding their initial coulombic efficiency, areal capacity, and material costs. Moreover, in-depth insights are offered to elucidate the mechanisms by which these structural modifications augment the properties of the binders and the performance of the cells. Ultimately, the prospective directions for the evolution of PAA-based binders designed for Si-based anodes in high-energy-density LIBs are deliberated.

Poly(Acrylic Acid)-Based Polymer Binders for High-Performance Lithium-Ion Batteries: From Structure to Properties

Poly(acrylic acid) (PAA) and its derivatives have emerged as promising candidates for enhancing the electrochemical performance of lithium-ion batteries (LIBs) as binder materials. Recent research has focused on evaluating their ability to improve adhesion with silicon (Si) particles and facilitate ion transport while maintaining electrode integrity. Various strategies, including mixing modifications and copolymerization methods, are highlighted and the structural and physicochemical properties of these binders are examined. Additionally, the interaction mechanisms between PAA-based binders and active materials and their impact on key electrochemical properties such as initial Coulombic efficiency (ICE) and cycle stability are discussed. The findings underscore the efficacy of tailored PAA-based binders in enhancing the electrochemical properties of LIBs, offering insights into the design principles and practical implications for advanced battery materials. These advancements hold promise for developing high-performance lithium batteries capable of meeting future energy storage demands.

Bio-Inspired Self-Healing Silicon Anodes: Harnessing Tea Polyphenols to Enhance Lithium-Ion Battery Performance

This study introduces an anode material for lithium-ion batteries, achieved by integrating tea polyphenols (TP) with the widely utilized polyacrylic acid (PAA) binder. The composite material capitalizes on the intrinsic self-healing properties of TP, enhancing the anode's durability and adhesiveness without the need for additional organic synthesis. The incorporation of TP has been demonstrated to significantly elevate ionic conductivity and expedite lithium ion diffusion, thereby reducing interfacial resistance and decelerating the rate of capacity fade due to electrolyte decomposition and silicon particle expansion. Employing a comprehensive analytical toolkit, including Fourier transform infrared spectroscopy, thermogravimetric analysis, peel strength measurements, and density functional theory calculations, we elucidated the physicochemical properties of the Si@PAA-TP anode. The anode's electrochemical performance was systematically assessed through galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy, with scanning electron microscopy providing insights into postcycling mechanical property alterations. This research advances a cost-effective, high-performance adhesive strategy for silicon anodes and contributes to the development.

Cross-Linkable Binders for Si Anodes in High-Energy-Density Lithium-Ion Batteries

Although silicon (Si) has a high theoretical capacity, the large volume expansion during lithiation has greatly hindered its application in high-energy-density lithium-ion batteries (LIBs). Among the strategies for improving the performance of Si anode, the role of binders should not be underestimated. Here, a novel strategy for designing a cross-linkable binder for Si anode has been proposed. The binder with hydroxyl and nitrile groups can be in situ covalently cross-linked through the amide group in the batteries. The cross-linked binder (c-POAH) shows high elasticity and strong adhesion to Si particles and the current collector. Si||Li half coin cells using the c-POAH binder have excellent cycle performance and the capacity retention ratio is 67.1% after 100 cycles at 0.2 C. Scanning electronic microscopy images show that the c-POAH binder can contribute to suppressing the pulverization of the Si anode. Moreover, the investigation with X-ray photoelectronic spectrum demonstrates that the decomposition of the liquid electrolyte on Si anode has been mitigated and the c-POAH binder can promote the formation of a more stable SEI film. Our strategy of endowing the binder with good elasticity through in situ cross-linking has opened up a new route for developing binders, which will definitely promote the application of Si anodes in high-energy-density LIBs.

Cyclodextrins-Based Polyrotaxanes: From Functional Polymers to Applications in Electronics and Energy Storage Materials

The concept of polyrotaxane comes from the rotaxane structure in the supramolecular field. It is a mechanically interlocked supramolecular assembly composed of linear polymer chains and cyclic molecules. Over recent decades, the synthesis and application of polyrotaxanes have seen remarkable growth. Particularly, cyclodextrin-based polyrotaxanes have been extensively reported due to the low-price raw materials, good biocompatibility, and ease of modification. Hence, it is also one of the most promising mechanically interlocking supramolecules for wide industrialization in the future. Polyrotaxanes are widely introduced into materials such as elastomers, hydrogels, and engineering polymers to improve their mechanical properties or impart functionality to the materials. In these materials, polyrotaxane acts as a slidable cross-linker to dissipate energy through sliding or assist in dispersing stress concentration in the cross-linked network, thereby enhancing the toughness of the materials. Further, the unique sliding-ring effect of cyclodextrin-based polyrotaxanes has pioneered advancements in stretchable electronics and energy storage materials. This includes their innovative use in stretchable conductive composite and binders for anodes, addressing critical challenges in these fields. In this mini-review, our focus is to highlight the current progress and potential wider applications in the future, underlining their transformative impact across various domains of material science.

Bio-Inspired Electrodes with Rational Spatiotemporal Management for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are currently the predominant energy storage power source. However, the urgent issues of enhancing electrochemical performance, prolonging lifetime, preventing thermal runaway-caused fires, and intelligent application are obstacles to their applications. Herein, bio-inspired electrodes owning spatiotemporal management of self-healing, fast ion transport, fire-extinguishing, thermoresponsive switching, recycling, and flexibility are overviewed comprehensively, showing great promising potentials in practical application due to the significantly enhanced durability and thermal safety of LIBs. Taking advantage of the self-healing core-shell structures, binders, capsules, or liquid metal alloys, these electrodes can maintain the mechanical integrity during the lithiation-delithiation cycling. After the incorporation of fire-extinguishing binders, current collectors, or capsules, flame retardants can be released spatiotemporally during thermal runaway to ensure safety. Thermoresponsive switching electrodes are also constructed though adding thermally responsive components, which can rapidly switch LIB off under abnormal conditions and resume their functions quickly when normal operating conditions return. Finally, the challenges of bio-inspired electrode designs are presented to optimize the spatiotemporal management of LIBs. It is anticipated that the proposed electrodes with spatiotemporal management will not only promote industrial application, but also strengthen the fundamental research of bionics in energy storage.

Polymeric Binder Design for Sustainable Lithium-Ion Battery Chemistry

The design of binders plays a pivotal role in achieving enduring high power in lithium-ion batteries (LIBs) and extending their overall lifespan. This review underscores the indispensable characteristics that a binder must possess when utilized in LIBs, considering factors such as electrochemical, thermal, and dispersion stability, compatibility with electrolytes, solubility in solvents, mechanical properties, and conductivity. In the case of anode materials, binders with robust mechanical properties and elasticity are imperative to uphold electrode integrity, particularly in materials subjected to substantial volume changes. For cathode materials, the selection of a binder hinges on the crystal structure of the cathode material. Other vital considerations in binder design encompass cost effectiveness, adhesion, processability, and environmental friendliness. Incorporating low-cost, eco-friendly, and biodegradable polymers can significantly contribute to sustainable battery development. This review serves as an invaluable resource for comprehending the prerequisites of binder design in high-performance LIBs and offers insights into binder selection for diverse electrode materials. The findings and principles articulated in this review can be extrapolated to other advanced battery systems, charting a course for developing next-generation batteries characterized by enhanced performance and sustainability.

Tailoring Three-Dimensional Cross-Linked Networks Based on Water-Soluble Polymeric Materials for Stable Silicon Anode

For stable battery operation of silicon (Si)-based anodes, utilizing cross-linked three-dimensional (3D) network binders has emerged as an effective strategy to mitigate significant volume fluctuations of Si particles. In the design of cross-linked network binders, careful selection of appropriate cross-linking agents is crucial to maintaining a balance between the robustness and functionality of the network. Herein, we strategically design and optimize a 3D cross-linked network binder through a comprehensive analysis of cross-linking agents. The proposed network is composed of poly(vinyl alcohol) grafted poly(acrylic acid) (PVA-g-PAA, PVgA) and aromatic diamines. PVgA is chosen as the polymer backbone owing to its high flexibility and facile synthesis using an ecofriendly water solvent. Subsequently, an aromatic diamine is employed as a cross-linker to construct a robust amide network that features a resonance-stabilized high modulus and enhanced adhesion. Comparative investigations of three cross-linkers, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-oxidianiline, and 4,4'-oxybis[3-(trifluoromethyl)aniline] (TFODA), highlight the roles of the trifluoromethyl group (-CF3) and the ether linkage. Consequently, PVgA cross-linked with TFODA (PVgA-TFODA), featuring both -CF3 and -O-, establishes a well-balanced 3D network characterized by heightened elasticity and improved binding forces. The optimized Si and SiOx/graphite composite electrodes with the PVgA-TFODA binder demonstrate impressive structural stability and stable cycling. This study offers a novel perspective on designing cross-linked network binders, showcasing the benefits of a multidimensional approach considering chemical and physical interactions.

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.

Advances in Polymer Binder Materials for Lithium-Ion Battery Electrodes and Separators

Lithium-ion batteries (LIBs) have become indispensable energy-storage devices for various applications, ranging from portable electronics to electric vehicles and renewable energy systems. The performance and reliability of LIBs depend on several key components, including the electrodes, separators, and electrolytes. Among these, the choice of binder materials for the electrodes plays a critical role in determining the overall performance and durability of LIBs. This review introduces polymer binders that have been traditionally used in the cathode, anode, and separator materials of LIBs. Furthermore, it explores the problems identified in traditional polymer binders and examines the research trends in next-generation polymer binder materials for lithium-ion batteries as alternatives. To date, the widespread use of N-methyl-2-pyrrolidone (NMP) as a solvent in lithium battery electrode production has been a standard practice. However, recent concerns regarding its high toxicity have prompted increased environmental scrutiny and the imposition of strict chemical regulations. As a result, there is a growing urgency to explore alternatives that are both environmentally benign and safer for use in battery manufacturing. This pressing need is further underscored by the rising demand for diverse binder research within the lithium battery industry. In light of the current emphasis on sustainability and environmental responsibility, it is imperative to investigate a range of binder options that can align with the evolving landscape of green and eco-conscious battery production. In this review paper, we introduce various binder options that can align with the evolving landscape of environmentally friendly and sustainable battery production, considering the current emphasis on battery performance enhancement and environmental responsibility.

Cyclodextrins for Lithium Batteries Applications

Due to their high energy and power density, lithium-ion batteries (LIBs) have gained popularity in response to the demand for effective energy storage solutions. The importance of the electrode architecture in determining battery performance highlights the demand for optimization. By developing useful organic polymers, cyclodextrin architectures have been investigated to improve the performance of Li-based batteries. The macrocyclic oligosaccharides known as cyclodextrins (CDs) have relatively hydrophobic cavities that can enclose other molecules. There are many industries where this "host-guest" relationship has been found useful. The hydrogen bonding and suitable inner cavity diameter of CD have led to its selection as a lithium-ion diffusion channel. CDs have also been used as solid electrolytes for solid-state batteries and as separators and binders to ensure adhesion between electrode components. This review gives a general overview of CD-based materials and how they are used in battery components, highlighting their advantages.

Reducing volume expansion in micro silicon anodes via aramid nanofibers for stable lithium-ion batteries

The aramid nanofibers form networks on micro silicon particles (ANF-SMPs) by cryofixation and acid-induced protonation, whose zongzi-like wrapping structure reduces volume expansion during (de)lithiation. The obtained ANF-SMP electrode achieves a high capacity retention of 90.7% after 100 cycles at 0.5C, which maps a promising future for anodes with a long lifespan.

A novel nanosphere-in-nanotube iron phosphide Li-ion battery anode displaying a long cycle life, recoverable rate-performance, and temperature tolerance

Currently, non-ideal anodes restricts the development of long-term stable Li-ion batteries. Several currently available high-capacity anode candidates are suffering from a large volumetric change during charge and discharge and non-stable solid interphase formation. Here, we develop a novel nanosphere-confined one-dimensional yolk-shell anode taking iron phosphide (FeP) as a demonstrating case study. Multiple FeP nanospheres are encapsulated inside an FeP nanotube through a magnetic field-assisted and templated approach, forming a nanosphere-in-nanotube yolk-shell (NNYS) structure. After long-term 1000 cycles at 2 A g^-1, the NNYS FeP anode shows a good capacity of 560 mA h g^-1, and a coulombic efficiency of 99.8%. A recoverable rate-performance is also obtained after three rounds of tests. Furthermore, the capacities and coulombic efficiency remain stable at temperatures of -10 °C and 45 °C, respectively, indicating good potential for use under different conditions.