Chitosan, a new and environmental benign electrode binder for use with graphite anode in lithium-ion batteries

Achievements, challenges, and perspectives in the design of polymer binders for advanced lithium-ion batteries

Energy storage devices with high power and energy density are in demand owing to the rapidly growing population, and lithium-ion batteries (LIBs) are promising rechargeable energy storage devices. However, there are many issues associated with the development of electrode materials with a high theoretical capacity, which need to be addressed before their commercialization. Extensive research has focused on the modification and structural design of electrode materials, which are usually expensive and sophisticated. Besides, polymer binders are pivotal components for maintaining the structural integrity and stability of electrodes in LIBs. Polyvinylidene difluoride (PVDF) is a commercial binder with superior electrochemical stability, but its poor adhesion, insufficient mechanical properties, and low electronic and ionic conductivity hinder its wide application as a high-capacity electrode material. In this review, we highlight the recent progress in developing different polymeric materials (based on natural polymers and synthetic non-conductive and electronically conductive polymers) as binders for the anodes and cathodes in LIBs. The influence of the mechanical, adhesion, and self-healing properties as well as electronic and ionic conductivity of polymers on the capacity, capacity retention, rate performance and cycling life of batteries is discussed. Firstly, we analyze the failure mechanisms of binders based on the operation principle of lithium-ion batteries, introducing two models of "interface failure" and "degradation failure". More importantly, we propose several binder parameters applicable to most lithium-ion batteries and systematically consider and summarize the relationships between the chemical structure and properties of the binder at the molecular level. Subsequently, we select silicon and sulfur active electrode materials as examples to discuss the design principles of the binder from a molecular structure point of view. Finally, we present our perspectives on the development directions of binders for next-generation high-energy-density lithium-ion batteries. We hope that this review will guide researchers in the further design of novel efficient binders for lithium-ion batteries at the molecular level, especially for high energy density electrode materials.

Multifunctional Separator Enables High-Performance Sodium Metal Batteries in Carbonate-Based Electrolytes

Sodium metal has become one of the most promising anodes for next-generation cheap and high-energy-density metal batteries; however, challenges caused by the uncontrollable sodium dendrite growth and fragile solid electrolyte interphase (SEI) restrict their large-scale practical applications in low-cost and wide-voltage-window carbonate electrolytes. Herein, a novel multifunctional separator with lightweight and high thinness is proposed, assembled by the cobalt-based metal-organic framework nanowires (Co-NWS), to replace the widely applied thick and heavy glass fiber separator. Benefitting from its abundant sodiophilic functional groups and densely stacked nanowires, Co-NWS not only exhibits outstanding electrolyte wettability and effectively induces uniform Na+ ion flux as a strong ion redistributor but also favors constructing the robust N,F-rich SEI layer. Satisfactorily, with 10 µL carbonate electrolyte, a Na|Co-NWS|Cu half-cell delivers stable cycling (over 260 cycles) with a high average Coulombic efficiency of 98%, and the symmetric cell shows a long cycle life of more than 500 h. Remarkably, the full cell shows a long-term life span (over 1500 cycles with 92% capacity retention) at high current density in the carbonate electrolyte. This work opens up a strategy for developing dendrite-free, low-cost, and long-life-span sodium metal batteries in carbonate-based electrolytes.

Chitosan: Sources, Processing and Modification Techniques

Chitosan, a copolymer of glucosamine and N-acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection. This review, in line with the focus of this special issue, provides the reader with (1) an overview on different sources of chitin, (2) advances in techniques used to extract chitin and converting it into chitosan, (3) the importance of the inherent characteristics of the chitosan from different sources that makes them suitable for specific applications and, finally, (4) briefly summarizes ways of tailoring chitosan for specific applications. The review also presents the influence of the degree of acetylation (DA) and degree of deacetylation (DDA), molecular weight (M_w) on the physicochemical and biological properties of chitosan, acid-base behavior, biodegradability, solubility, reactivity, among many other properties that determine processability and suitability for specific applications. This is intended to help guide researchers select the right chitosan raw material for their specific applications.

Crosslinked Chitosan Binder for Sustainable Aqueous Batteries

The increased percentage of renewable power sources involved in energy production highlights the importance of developing systems for stationary energy storage that satisfy the requirements of safety and low costs. Na ion batteries can be suitable candidates, specifically if their components are economic and safe. This study focuses on the development of aqueous processes and binders to prepare electrodes for sodium ion cells operating in aqueous solutions. We demonstrated the feasibility of a chitosan-based binder to produce freestanding electrodes for Na ion cells, without the use of organic solvents and current collectors in electrode processing. To our knowledge, it is the first time that water-processed, freestanding electrodes are used in aqueous Na ion cells, which could also be extended to other types of aqueous batteries. This is a real breakthrough in terms of sustainability, taking into account low risks for health and environment and low costs.

Recent Advances in Chitin and Chitosan/Graphene-Based Bio-Nanocomposites for Energetic Applications

Herein, we report recent developments in order to explore chitin and chitosan derivatives for energy-related applications. This review summarizes an introduction to common polysaccharides such as cellulose, chitin or chitosan, and their connection with carbon nanomaterials (CNMs), such as bio-nanocomposites. Furthermore, we present their structural analysis followed by the fabrication of graphene-based nanocomposites. In addition, we demonstrate the role of these chitin- and chitosan-derived nanocomposites for energetic applications, including biosensors, batteries, fuel cells, supercapacitors and solar cell systems. Finally, current limitations and future application perspectives are entailed as well. This study establishes the impact of chitin- and chitosan-generated nanomaterials for potential, unexplored industrial applications.

The preparation of mass producible, highly-cycling stable Si/C anode materials with nano-sized silicon crystals embedded in highly amorphous silicon matrix

The commercial applications of silicon nanomaterials as anode in lithium-ion batteries must solve two important problems, namely low expansion and long-term cycle stability. The former is related to nano-silicon structure, while the latter depends on silicon/carbon composite structure and preparation process. In order to suppress volume expansion appeared during lithiation, this paper selects a kind of silicon nanoparticles (SiNPs) with a high degree of amorphization (81.9%), and designs a stable silicon/carbon composite material structure. Inside this structure, graphite nanoflakes (GNFs) with high specific surface are used as the skeleton, which can provide enough surface area for SiNPs to adhere and avoid the local accumulation of SiNPs. Outside this structure is uniformly coated with a layer of amorphous carbon. Raman and x-ray diffraction results show that after the high-temperature carbonization, the nano-silicon in the composite material still maintains a high degree of amorphization (67.1%) and the average crystallite size of Si has only increased from 3.7 to 9.5 nm. The initial Coulombic efficiency and reversible specific capacity of the composite material are 86.7% and 1374.8 mAh g^-1, respectively. After mixing with commercial graphite, the initial Coulombic efficiency and reversible specific capacity are 93.7% and 426.4 mAh g^-1, respectively. LiNi_0.8Co_0.1Mn_0.1O₂(NCM811) is used as the cathode to produce a soft-pack battery. After 900 cycles at room temperature, the capacity remains 86.2%. The silicon/carbon anode material reported in this paper is of great potential for commercialization.

Gifts from Nature: Bio-Inspired Materials for Rechargeable Secondary Batteries

Materials in nature have evolved to the most efficient forms and have adapted to various environmental conditions over tens of thousands of years. Because of their versatile functionalities and environmental friendliness, numerous attempts have been made to use bio-inspired materials for industrial applications, establishing the importance of biomimetics. Biomimetics have become pivotal to the search for technological breakthroughs in the area of rechargeable secondary batteries. Here, the characteristics of bio-inspired materials that are useful for secondary batteries as well as their benefits for application as the main components of batteries (e.g., electrodes, separators, and binders) are discussed. The use of bio-inspired materials for the synthesis of nanomaterials with complex structures, low-cost electrode materials prepared from biomass, and biomolecular organic electrodes for lithium-ion batteries are also introduced. In addition, nature-derived separators and binders are discussed, including their effects on enhancing battery performance and safety. Recent developments toward next-generation secondary batteries including sodium-ion batteries, zinc-ion batteries, and flexible batteries are also mentioned to understand the feasibility of using bio-inspired materials in these new battery systems. Finally, current research trends are covered and future directions are proposed to provide important insights into scientific and practical issues in the development of biomimetics technologies for secondary batteries.

Polysaccharides for sustainable energy storage - A review

The increasing amount of electric vehicles on our streets as well as the need to store surplus energy from renewable sources such as wind, solar and tidal parks, has brought small and large scale batteries into the focus of academic and industrial research. While there has been huge progress in performance and cost reduction in the past years, batteries and their components still face several environmental issues including safety, toxicity, recycling and sustainability. In this review, we address these challenges by showcasing the potential of polysaccharide-based compounds and materials used in batteries. This particularly involves their use as electrode binders, separators and gel/solid polymer electrolytes. The review contains a historical section on the different battery technologies, considerations about safety on batteries and requirements of polysaccharide components to be used in different types of battery technologies. The last sections cover opportunities for polysaccharides as well as obstacles that prevent their wider use in battery industry.

Tin Oxide Encapsulated into Pyrolyzed Chitosan as a Negative Electrode for Lithium Ion Batteries

Tin oxide is one of the most promising electrode materials as a negative electrode for lithium-ion batteries due to its higher theoretical specific capacity than graphite. However, it suffers lack of stability due to volume changes and low electrical conductivity while cycling. To overcome these issues, a new composite consisting of SnO2 and carbonaceous matrix was fabricated. Naturally abundant and renewable chitosan was chosen as a carbon source. The electrode material exhibiting 467 mAh g−1 at the current density of 18 mA g−1 and a capacity fade of only 2% after 70 cycles is a potential candidate for graphite replacement. Such good electrochemical performance is due to strong interaction between amine groups from chitosan and surface hydroxyl groups of SnO2 at the preparation stage. However, the charge storage is mainly contributed by a diffusion-controlled process showing that the best results might be obtained for low current rates.

Green water-based binders for LiFePO4/C cathodes in Li-ion batteries: a comparative study

Compared with environmentally harmful binder polyvinylidene fluoride for Li-ion battery cathodes, green water-based binders have large content of carboxyl groups, which can provide additional lithium ion transfer channels to improve rate performance.

Highly Efficient Multicomponent Gel Biopolymer Binder Enables Ultrafast Cycling and Applicability in Diverse Battery Formats

Electrode materials with a high performance and stable cycling have been commercialized, but the utilization of state-of-the-art Li-ion batteries in high-current rate applications is restricted because of limitations in other battery components, in particular, the lack of an efficient binder. Herein, a novel multicomponent polymer gel binder (PGB) is presented, comprising the biopolymer chitosan as the host, embedded with the 1-butyl-1-methylpyrrolidinium dicyanamide (PYR₁₄DCA) ionic liquid and the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. The multicomponent approach leads to carbon black arrangement along well-distributed chitosan chains in the electrodes, forming a highly electronic conductive network. Furthermore, the plasticizing effect of the ionic liquid leads to an enhanced ionic conductivity. As a result, shorter charge-transfer paths are enabled, leading to an exceptionally high rate capability in LiFePO₄ and Li₄Ti₅O₁₂ half cells, up to 50C. LiFePO₄||Li₄Ti₅O₁₂ full cells using the PGB for both electrodes also demonstrated stable cycling at 10C, with an impressively high discharge capacity of 173 mA h·g^-1 after 1000 cycles. In addition, freestanding electrodes could also be realized and functioning flexible Li-ion cells were successfully demonstrated. Thus, the novel water-processable binder offers multifaceted advantages, making the approach highly promising for industrial implementation.

Sulfonation of alginate grafted with polyacrylamide as a potential binder for high-capacity Si/C anodes

A systematic approach for how to find an appropriate polymer binder for high-capacity LIB anodes is presented in this study. As an example, a newly-developed SAlg-g-PAAm binder, alginate functionalized with sulfo groups and subsequently grafted with polyacrylamide, is used for the Si/C electrode. Various characteristics of the binder polymer itself, two basic characteristics of the electrode with respect to the binder, and the effect of the binder on cell performance are subsequently investigated. In all respects, the SAlg-g-PAAm polymer is a very promising binder for high-capacity anodes. The sulfo groups in the binder improve the ionic conductivities in both the binder and the electrode, leading to reduced charge transfer resistance. In addition, the sulfonation of the alginate grafted with polyacrylamide significantly enhances the mechanical and adhesion properties of the binder and consequently decreases the volume change generated during cycles. These advantages of the SAlg-g-PAAm binder ultimately lead to a considerable enhancement in the electrochemical performance of the high-capacity Si/C electrodes.

A systematic approach for how to find an appropriate polymer binder for high-capacity LIB anodes is presented in this study.

Sequence-Defined Peptoids with -OH and -COOH Groups As Binders to Reduce Cracks of Si Nanoparticles of Lithium-Ion Batteries

Silicone (Si) is one type of anode materials with intriguingly high theoretical capacity. However, the severe volume change associated with the repeated lithiation and delithiation processes hampers the mechanical/electrical integrity of Si anodes and hence reduces the battery's cycle-life. To address this issue, sequence-defined peptoids are designed and fabricated with two tailored functional groups, "-OH" and "-COOH", as cross-linkable polymeric binders for Si anodes of LIBs. Experimental results show that both the capacity and stability of such peptoids-bound Si anodes can be significantly improved due to the decreased cracks of Si nanoparticles. Particularly, the 15-mer peptoid binder in Si anode can result in a much higher reversible capacity (ca. 3110 mAh g-1) after 500 cycles at 1.0 A g-1 compared to other reported binders in literature. According to the density functional theory (DFT) calculations, it is the functional groups presented on the side chains of peptoids that facilitate the formation of Si-O binding efficiency and robustness, and then maintain the integrity of the Si anode. The sequence-designed polymers can act as a new platform for understanding the interactions between binders and Si anode materials, and promote the realization of high-performance batteries.

Effect of Combined Conductive Polymer Binder on the Electrochemical Performance of Electrode Materials for Lithium-Ion Batteries

The electrodes of lithium-ion batteries (LIBs) are multicomponent systems and their electrochemical properties are influenced by each component, therefore the composition of electrodes should be properly balanced. At the beginning of lithium-ion battery research, most attention was paid to the nature, size, and morphology peculiarities of inorganic active components as the main components which determine the functional properties of electrode materials. Over the past decade, considerable attention has been paid to development of new binders, as the binders have shown great effect on the electrochemical performance of electrodes in LIBs. The study of new conductive binders, in particular water-based binders with enhanced electronic and ionic conductivity, has become a trend in the development of new electrode materials, especially the conversion/alloying-type anodes. This mini-review provides a summary on the progress of current research of the effects of binders on the electrochemical properties of intercalation electrodes, with particular attention to the mechanisms of binder effects. The comparative analysis of effects of three different binders (PEDOT:PSS/CMC, CMC, and PVDF) for a number of oxide-based and phosphate-based positive and negative electrodes for lithium-ion batteries was performed based on literature and our own published research data. It reveals that the combined PEDOT:PSS/CMC binder can be considered as a versatile component of lithium-ion battery electrode materials (for both positive and negative electrodes), effective in the wide range of electrode potentials.

Microporous Binder for the Silicon-Based Lithium-Ion Battery Anode with Exceptional Rate Capability and Improved Cyclic Performance

Silicon anodes have attracted much attention owing to their high theoretical capacity. Nonetheless, an inevitable and enormous volumetric expansion of silicon in the lithiated state restrained the development of the silicon anode for lithium-ion batteries. Fortunately, the utilization of the high-performance binder is a promising and effective way to overcome such obstacles. Herein, a polymer of intrinsic microporosity (PIM) is applied as the binder for the silicon anode, which is composed of a rigid polymer backbone, an intrinsic porous structure, and active carboxyl groups (PIM-COOH). Compared to the traditional binder, both the long-term stability and rate performance of the electrode using PIM-COOH as the binder are significantly improved. The mechanism responsible for the enhanced performance is investigated. The PIM-COOH binder provides stronger adhesion toward the current collector than the conventional binders. The unique rigid polymer backbone and porous structure of the PIM-COOH binder enable a good capability to withstand the volume change and external stress generated by the Si anode. The porous structure of the PIM-COOH binder enhances lithium-ion transportation compared to the SA binder, which improves rate performance of the silicon anode. This work provides a unique insight into design, synthesis, and utilization of the binders for lithium-ion batteries.

Chitosan-grafted-poly(aniline-co-anthranilic acid) as a water soluble binder to form 3D structures for Si anodes

We graft an electrically conductive poly(aniline-co-anthranilic acid) (PAAA) polymer capable of interacting with Si particles onto chitosan, a natural hydrophilic polymer, to form a chitosan-grafted-PAAA (CS-g-PAAA) copolymer, and use it as a new water soluble polymeric binder for Si anodes to relieve the physical stress resulting from Si volume change during charge/discharge cycles. The carboxylic acid functional groups within the PAAA structure, as well as the chitosan functional groups, bind to silicon particles to form a stable 3D network, resulting in high adhesion. Because the binder is conductive, the electrode using the CS-g-PAAA-8 : 1 with an optimal composition ratio of CS to PAAA of 8 : 1 shows a high initial capacity of 2785.6 mA h g⁻¹, and maintains a high capacity of 1301.0 mA h g⁻¹ after 300 cycles. We also extract chitosan directly from crab shells, and fabricate a Si@ECS-g-PAAA electrode by grafting PAAA onto the extracted-chitosan (ECS). This electrode records an initial capacity of 3057.3 mA h g⁻¹, and maintains a high capacity of 1408.8 mA h g⁻¹ with 51.4% retention after 300 cycles. Overall, we develop a polymeric binder with outstanding cell properties, ease of fabrication, and high water solubility for Si anodes by grafting a conductive PAAA onto chitosan.

We develop a polymeric binder with outstanding cell properties, and high water solubility for Si anodes by grafting a conductive PAAA onto chitosan.

One-step Synthesized Silver Nanoparticles Using Isoimperatorin: Evaluation of Photocatalytic, and Electrochemical Activities

In the current study, isoimperatorin, a natural furanocoumarin, is used as a reducing reagent to synthesize isoimperatorin mediated silver nanoparticles (Iso-AgNPs), and photocatalytic and electrocatalytic activities of Iso-AgNPs are evaluated. Iso-AgNPs consisted of spherically shaped particles with a size range of 79-200 nm and showed catalytic activity for the degradation (in high yields) of New Fuchsine (NF), Methylene Blue (MB), Erythrosine B (ER) and 4-chlorophenol (4-CP) under sunlight irradiation. Based on obtained results, Iso-AgNPs exhibited 96.5%, 96.0%, 92%, and 95% degradation rates for MB, NF, ER, and 4-CP, respectively. The electrochemical performance showed that the as-prepared Iso-AgNPs exhibited excellent electrocatalytic activity toward hydrogen peroxide (H2O2) reduction. It is worth noticing that the Iso-AgNPs were used as electrode materials without any binder. The sensor-based on binder-free Iso-AgNPs showed linearity from 0.1 µM to 4 mM with a detection limit of 0.036 μM for H2O2. This binder-free and straightforward strategy for electrode preparation by silver nanoparticles may provide an alternative technique for the development of other nanomaterials based on isoimperatorin under green conditions. Altogether, the application of isoimpratorin in the synthesis of nano-metallic electro and photocatalysts, especially silver nanoparticles, is a simple, cost-effective and efficient approach.

Chitosan complements entrapment of silicon inside nitrogen doped carbon to improve and stabilize the capacity of Li-ion batteries

A facile strategy to entrap milled silicon (m-Si) particles using nitrogen-doped-carbon (N-C@m-Si) to overcome the dramatic volume changes in Si during intercalation of lithium ions and to improve its electronic conductivity is reported here. The only natural nitrogen containing biomaterial alkaline polysaccharide, i.e., chitosan, is used as the carbon source. Simple hydrothermal technique followed by a subsequent carbonization process is used to synthesize N-C and N-C@m-Si particles. N-C@m-Si exhibited significantly improved electrochemical performance as compared to bare m-Si, which is confirmed by the obtained discharge capacity of 942.4 mAh g⁻¹ and columbic efficiency of 97% after 50 cycles at 0.1C rate. With regard to the N-C electrodes, the obtained discharge capacity of 485.34 mAh g⁻¹ and columbic efficiency of 99.78%, after 50 cycles at 0.1C rate is superior to the commercial graphite electrodes. The solid electrolyte interphase (SEI) layer that formed over m-Si and N-C@m-Si electrodes is characterized using X-ray photoelectron spectroscopy. Compared to the SEI layer that formed over m-Si electrode after 10 charge-discharge cycles, the N-C@m-Si electrode had a stable lithium fluoride and carbonate species. Brief reaction mechanisms, representing the formation of different species in the SEI layer, is derived to explain its behavior during the electrochemical processes.

Enhancing capacitive deionization performance with charged structural polysaccharide electrode binders

Capacitive deionization (CDI) performance, as measured by salt adsorption capacity (SAC) and energy normalized adsorption of salt (ENAS), is frequently limited by anion repulsion at the positive electrode. In this work, we investigate the ability to prevent co-ion repulsion by increasing complementary fixed charged within the electrode macropores by binding composite CDI electrodes with the ionically charged structural polysaccharides chitosan and carboxymethyl cellulose. When employing asymmetrically charged electrode binders, co-ion repulsion was prevented, resulting in SAC and ENAS values that were three times greater than composite electrodes bound with polyvinylidene fluoride (PVDF) and similar to CDI electrodes composed of chemically modified carbon. Polysaccharide binders did not modify the charge balance in the carbon micropores but did shift the discharge voltage of maximum adsorption, enabling a shift in operating voltage that prolonged cycle lifetime without a significant loss in performance. The mechanism of improved salt accumulation with polysaccharide binders was explored with a one-dimensional model that integrated CDI and ion-exchange membrane covered (MCDI) sub-units. Model simulations indicate that carbon macropores covered with thin layers of charged polysaccharides increase adsorption by a sequential accumulation and release of salt to depleted uncovered pores.

Exploring Chemical, Mechanical, and Electrical Functionalities of Binders for Advanced Energy-Storage Devices

Tremendous efforts have been devoted to the development of electrode materials, electrolytes, and separators of energy-storage devices to address the fundamental needs of emerging technologies such as electric vehicles, artificial intelligence, and virtual reality. However, binders, as an important component of energy-storage devices, are yet to receive similar attention. Polyvinylidene fluoride (PVDF) has been the dominant binder in the battery industry for decades despite several well-recognized drawbacks, i.e., limited binding strength due to the lack of chemical bonds with electroactive materials, insufficient mechanical properties, and low electronic and lithium-ion conductivities. The limited binding function cannot meet inherent demands of emerging electrode materials with high capacities such as silicon anodes and sulfur cathodes. To address these concerns, in this review we divide the binding between active materials and binders into two major mechanisms: mechanical interlocking and interfacial binding forces. We review existing and emerging binders, binding technology used in energy-storage devices (including lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, and supercapacitors), and state-of-the-art mechanical characterization and computational methods for binder research. Finally, we propose prospective next-generation binders for energy-storage devices from the molecular level to the macro level. Functional binders will play crucial roles in future high-performance energy-storage devices.

Aqueous Binder Enhanced High-Performance GeP5 Anode for Lithium-Ion Batteries

GeP5 is a recently reported new anode material for lithium ion batteries (LIBs), it holds a large theoretical capacity about 2300 mAh g-1, and a high rate capability due to its bi-active components and superior conductivity. However, it undergoes a large volume change during its electrochemical alloying and de-alloying with Li, a suitable binder is necessary to stable the electrode integrity for improving cycle performance. In this work, we tried to apply aqueous binders LiPAA and NaCMC to GeP5 anode, and compared the difference in electrochemical performance between them and traditional binder PVDF. As can be seen from the test result, GeP5 can keep stable in both common organic solvents and proton solvents such as water and alcohol solvents, it meets the application requirements of aqueous binders. The electrochemistry results show that the use of LiPAA binder can significantly improve the initial Coulombic efficiency, reversible capacity, and cyclability of GeP5 anode as compared to the electrodes based on NaCMC and PVDF binders. The enhanced electrochemical performance of GeP5 electrode with LiPAA binder can be ascribed to the unique high strength long chain polymer structure of LiPAA, which also provide numerous uniform distributed carboxyl groups to form strong ester groups with active materials and copper current collector. Benefit from that, the GeP5 electrode with LiPAA can also exhibit excellent rate capability, and even at low temperature, it still shows attractive electrochemical performance.

Modified Separator Performing Dual Physical/Chemical Roles to Inhibit Polysulfide Shuttle Resulting in Ultrastable Li-S Batteries

In this paper we describe a modified (AEG/CH) coated separator for Li-S batteries in which the shuttling phenomenon of the lithium polysulfides is restrained through two types of interactions: activated expanded graphite (AEG) flakes interacted physically with the lithium polysulfides, while chitosan (CH), used to bind the AEG flakes on the separator, interacted chemically through its abundance of amino and hydroxyl functional groups. Moreover, the AEG flakes facilitated ionic and electronic transfer during the redox reaction. Live H-cell discharging experiments revealed that the modified separator was effective at curbing polysulfide shuttling; moreover, X-ray photoelectron spectroscopy analysis of the cycled separator confirmed the presence of lithium polysulfides in the AEG/CH matrix. Using this dual functional interaction approach, the lifetime of the pure sulfur-based cathode was extended to 3000 cycles at 1C-rate (1C = 1670 mA/g), decreasing the decay rate to 0.021% per cycle, a value that is among the best reported to date. A flexible battery based on this modified separator exhibited stable performance and could turn on multiple light-emitting diodes. Such modified membranes with good mechanical strength, high electronic conductivity, and anti-self-discharging shield appear to be a scalable solution for future high-energy battery systems.

New eco-friendly low-cost binders for Li-ion anodes

In the production of commercial Li-ion batteries, the active materials slurries are generally prepared using polyvinylidene fluoride (PVdF) as binder because of its good adhesion properties and electrochemical stability. Unfortunately, there are some disadvantages related to the use of PVdF: the most important is the use of toxic and environmentally unfriendly solvents, such as N-methyl-pyrrolidone (NMP), and the second is the high costs. In the light of these considerations, it seemed straightforward to investigate the suitability of some water-soluble, inexpensive, and eco-friendly materials to test as alternative binders (sodium alginate, chitosan tragacanth gum, gelatin). The rheological properties of these materials have been investigated in addition to the electrochemical characterization. Furthermore, graphite electrodes with PVdF, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) binders have been considered for sake of comparison. We found that some of these water-soluble binders, besides good electrochemical performances, showed a high adhesion to the current collector and a good electrochemical stability under the experimental conditions employed, which makes them interesting for the next generation of Li-ion batteries.

Liquefied walnut shell-derived carbon nanofibrous mats as highly efficient anode materials for lithium ion batteries

Mechanically flexible walnut shell-derived carbon nanofibers (CNFs) of 175 nm diameter were fabricated from a liquefied walnut shell—polyvinyl alcohol (PVA) hybrid solutionviaconventional electrospinning followed by one-step carbonization.

Cross-Linked Chitosan as an Efficient Binder for Si Anode of Li-ion Batteries

We investigate the use of chitosan (CS) as a new cross-linkable and water-soluble binder for the Si anode of Li-ion batteries. In contrast to the traditional binder utilizing a hydrogen bond and/or van der Waals force-linked anode electrodes, CS can easily form a 3D network to limit the movement of Si particles through the cross-linking between the amino groups of CS and the dialdehyde of glutaraldehyde (GA). Chemical, mechanical, and morphological analyses are conducted by Fourier transform infrared spectroscopy, tensile testing, and scanning electron microscopy. The cross-linked Si/CS-GA anode exhibits an initial discharge capacity of 2782 mAh g(-1) with a high initial Coulombic efficiency of 89% and maintained a capacity of 1969 mAh g(-1) at the current density of 500 mA g(-1) over 100 cycles.

Environment-friendly cathodes using biopolymer chitosan with enhanced electrochemical behavior for use in lithium ion batteries

The biopolymer chitosan has been investigated as a potential binder for the fabrication of LiFePO4 cathode electrodes in lithium ion batteries. Chitosan is compared to the conventional binder, polyvinylidene fluoride (PVDF). Dispersion of the active material, LiFePO4, and conductive agent, Super P carbon black, is tested using a viscosity analysis. The enhanced structural and morphological properties of chitosan are compared to the PVDF binder using X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FE-SEM). Using an electrochemical impedance spectroscopy (EIS) analysis, the LiFePO4 electrode with the chitosan binder is observed to have a high ionic conductivity and a smaller increase in charge transfer resistance based on time compared to the LiFePO4 electrode with the PVDF binder. The electrode with the chitosan binder also attains a higher discharge capacity of 159.4 mAh g(-1) with an excellent capacity retention ratio of 98.38% compared to the electrode with the PVDF binder, which had a discharge capacity of 127.9 mAh g(-1) and a capacity retention ratio of 85.13%. Further, the cycling behavior of the chitosan-based electrode is supported by scrutinizing its charge-discharge behavior at specified intervals and by a plot of dQ/dV.