Binder For Lithium-ion Batteries Research Articles

Thermal treatment effect on electrochemical properties of silicon alloy anodes with poly(ether imide) binder for lithium-ion batteries

The development of silicon-based anodes with high capacity and good cycling stability for next-generation Li+ batteries (LIBs) is a very challenging task due to the large volume expansion of the electrodes during repeated cycling, which leads to fading in capacity. In this study, the electrochemical performance of Si alloy-based anodes with poly (ether imide) (PEI) binder is evaluated after thermal treatment at various temperatures. The systematic study revealed that the thermal treatment of the anodes with PEI binder at above 500 °C results in the partial carbonization of the PEI and remarkably enhances the electrochemical performance, such as cycle life and high rate capabilities. The partially carbonized PEI acts as both a binder and conductive additive for the Si-alloy anodes. This superior electrochemical performance is attributed to the strong adhesion of the partially carbonized PEI binder resulting from enhanced secondary interactions, which maintained good electrical contacts between the active materials, electronic conductors, and current collector during cycling. The partial carbonization strategy can be readily scaled up due to the facile heat treatment process, offering a new approach for developing next-generation high-capacity batteries.

The effect of sulfonated copolymer as a binder on the electrochemical performance of LiFePO4 cathode for lithium-ion batteries

In today's market, lithium-ion batteries are proving to be the most promising and effective rechargeable batteries. In the development of active materials with high energy density for batteries, the design of binders is a bottleneck technology, which produces an interconnected electrode structure. In this study, for developing lithium-ion batteries with high efficiency, the sulfonated copolymer was employed as an effective binder. In order to improve the performance of poly(vinylidene fluoride) (PVDF) as a binder for lithium-ion batteries (LIBs), sulfonated PVDF copolymer was prepared in this study using the atom transfer radical polymerization (ATRP) process. The influence of sulfonated PVDF binder on the electrochemical performances of LIBs was assessed using charge and discharge measurements, cycling performance up to 300 cycles, cycling voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analysis. The investigation indicated decreased concentration polarization and improved lithiation and delithiation kinetics at high number of charge/discharge cycles for LiFePO4 electrodes with sulfonated PVDF binders. The discharge capacity after 300 cycles was 90 mAh g−1 with a capacity retention of 100% at 1C. As a result, the copolymer synthesized in this paper can be utilized to design next-generation polymer binders for high-efficiency LIBs.

Separation of Cathode Material from Aluminum Plate by Ultrasonic Action using Fenton’s Reagent

Polyvinylidene fluoride (PVDF) has been used as a binder in lithium-ion batteries due to its high viscosity, which makes it difficult to separate the cathode material from the aluminum plate when recycling waste lithium-ion batteries. In this study, the peeling effect and mechanism of Fenton’s reagent on the cathode material and aluminum plate of spent lithium-ion batteries under the action of ultrasound has been researched. The results showed that when the ratio of Fe2+/H2O2 was 1:40, temperature was 45 °C, time was 35 min, and liquid-solid ratio was 50:1, the removal rate of cathode material was 98.52%. The combined action of Fenton’s reagent and ultrasonic cavitation oxidized or promoted PVDF to combine with lithium cobalt oxide to form COF3, thereby separating the cathode material from the aluminum foil without changing the structure of lithium cobalt oxide cathode material. Nevertheless, this study may provide a processing method to separate the cathode material from the aluminum plate effectively.

Recovery and Reuse of Composite Cathode Binder in Lithium Ion Batteries.

Here, we investigate the recovery and reuse of polyvinylidene fluoride (PVDF) binders from both homemade and commercial cathode films in Li ion batteries. We find that PVDF solubility depends on whether the polymer is an isolated powder or cast into a composite film. A mixture of tetrahydrofuran:N‐methyl‐2‐pyrrolidone (THF : NMP, 50 : 50 v/v) at 90 °C delaminates composite cathodes from Al current collectors and yields pure PVDF as characterized by 1H nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), wide‐angle X‐ray scattering (WAXS), and scanning electron microscopy (SEM). PVDF recovered from Li ion cells post‐cycling exhibits similar performance to pristine PVDF. These data suggest that PVDF can be extracted and reused during Li ion battery recycling while simultaneously eliminating the formation of HF etchants, providing an incentive for use in direct cathode recycling.

Enhanced the mechanical strength of polyimide (PI) nanofiber separator via PAALi binder for lithium ion battery

Polyimide (PI) nanofiber membrane prepared by electrospinning technique exhibits poor mechanical strength for the slippage of fibers, which limits it applied into lithium ion battery (LIB). In this study, we are devoted to promoting the macro mechanical strength of PI nanofiber membrane by inhibiting the slippage among the fibers. Lithium polyacrylate (PAALi) is a kind of excellent binder, and it contributes to increasing the adhesion effect between the fibers. As a result, the PI nanofiber membrane treated by PAALi solution shows the mechanical strength of 16.1 MPa, higher than 5.0 MPa of pristine PI membrane. The introduction of this binder makes the originally loose and disordered PI nanofibers cross-link with each other and prevents from the slip between the fibers. Surprisingly, the PAALi binder has no effect on the thermal stability and electrochemical performance of PI nanofiber separator. Furthermore, these LiCoO2/Li cells using the modified PI nanofiber separators exhibit better cycling stability and superior rate performance compared with the cells containing pristine PI separators. It demonstrates that the use of PAALi binder is a promising method to improve the mechanical strength of nanofiber membrane, which gets it applied in the high-power LIB.

Analysis of mechanical failure at the interface between graphite particles and polyvinylidene fluoride binder in lithium-ion batteries

The capacity fade corresponding to the mechanical failure of active materials is one of hurdles to overcome in the widespread of echo-friendly vehicles. However, the mechanisms of the mechanical failure at the electrode are not fully understood. In this study, the initiation and propagation of debonding at the interface between an active particle and a binder are investigated using a coupled electrochemical-mechanical and cohesive-zone finite-element model. The effects of particle sizes and lithiation kinetics on the progressive growth of interfacial debonding are studied, and critical states of charges are determined. The normal and shear tractions at the interface are systematically analyzed to understand their role in debonding behavior. The simulation results show that the interfacial debonding is less likely to happen as the particle size and C-rate increase, which is opposite to the inner-particle fracture behavior. The numerical study indicates that there is a trade-off between the inter-particle failure and inner-particle fracture. This study suggests that the binder effect needs to be included in the theoretical model for better understanding of the mechanical failure at the electrode. The debonding failure maps provided from the study can assist in engineering design of active materials and safe operation of batteries.

Influence of copolymer chain sequence on electrode latex binder for lithium-ion batteries

Electrode binders have significant influences on lithium-ion battery performance. Good binders should be able to absorb electrolyte to accelerate lithium-ion transport while simultaneously maintaining adequate adhesion and mechanical strength after swelling. Currently, most polymer binders are based on homo or random copolymers so they may only meet one of these requirements, as an improvement in electrolyte swelling ability is detrimental to mechanical strength, and vice versa. This work investigates whether the design of chain sequence can resolve this contradiction. Reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization is employed to synthesize copolymer latex with different chain sequences as electrode binders, which are examined in both LiFePO4 cathode and silicon anodes. The results show a triblock copolymer chain sequence gives the best performance. The microphase separation in triblock copolymer distributes functionalities of electrolyte affinity and strength maintenance into disparate blocks and therefore satisfies both requirements simultaneously. The advantages of triblock chain sequence are demonstrated by superior ionic conductivity, mechanical strength after electrolyte absorption, and lithium-ion diffusion coefficient and then lead to better battery performance compared with random counterpart and commercial aqueous binders.

Low-Cost Alternatives to Pedot:PSS As Conducting Binders

Pedot:PSS is a molecular level composite material of conjugated polymer (Pedot) and anionic polyelectrolyte, or polyanion (PSS). It is popular in organic electronics and as transparent conductor, because it is water dispersible, conductive and film-forming upon drying. For the same reasons, Pedot:PSS has previously been suggested as binder in lithium-ion batteries. However, its high cost is prohibitive for routine battery applications. This presentation discusses our exploration of chemically similar, but lower-cost molecular polymer composites of conjugated polymers and polyanions, to be used as lithium- and sodium-ion battery binders. Within these composites, the conjugated polymer serves to deliver electronic conductivity, whereas the polyanion allows dispersion of the composite, and provides strong adhesion to battery particles. We perform the oxidative polymerization in the presence of the polyanion, at which the polyanion backbone serves as polymerization template. In this way, the latter becomes a permanently intertwined polymeric dopant within the conjugated polymer. We are presenting data on the electrochemical stability of these binders within typical battery environments and the dependence of electronic conductivity on composition and synthesis methods. Moreover, composite battery electrodes have been fabricated and electrode micro-structure and cycling performance data are presented. Examples are selected based on low-cost polymers of Pyrrole and Aniline, combined with non-traditional polyanion binders, such as Carboxymethyl Cellulose and Alginate. The target of this work is to improve cycling performance of high-capacity, high-volume-change intercalation materials. In traditional composite lithium and sodium intercalation electrodes, such intercalation materials exhibit very little adhesive strength with the typical carbon conductive additive. By combining the adhesive and conductive additive within a single molecular composite binder, the conductor adheres directly to the intercalation material, accommodating volume changes more easily and improving lifetime of high capacity materials.

Dispersed distribution derived integrated anode for lithium ion battery

With the development of portable communication devices and electric vehicles, there is a great need for energy storage devices with lighter weight and higher energy density. In this paper, a new method by combining waster-paper-synthesized conductive paper (CP) and active material MnO2 together is developed to obtain a new type of anode without any binder for lithium ion batteries. By this way, we can obtain low density anode with active material in CP, instead of the commonly-used heavy metal current collector. Also, binder has been abandoned, which are usually used to combine active material into anode, to further decrease weight. The multi walled carbon nanotube (MWCNT) was added in serves as a component of CP and the conductive agent for active material. Compared to traditional anode coated on Cu current collector, the CP-combined anode can greatly improve the electrochemical performance of active material MnO2. It can let more particles to fully participate in the reaction and therefore boost the specific capacity to a great extent (about 3 times higher). It delivered an initial specific capacity of 1629.9 mA h g−1 at a current density of 100 mA g−1 and maintained about 67% even after 100 cycles. What’s more, it shows reversible capacity of about 260 mA h g−1 at high current density of 1000 mA h g−1. Our original synthesis method of anode, which shows far-reaching referential value and environmental significance, can be generalized to other electrodes and other battery systems.

Self-Doped Conjugated Polymeric Binders Improve the Capacity and Mechanical Properties of V₂O₅ Cathodes.

Polymeric binders serve to stabilize the morphology of electrodes by providing adhesion and binding between the various components. Successful binders must serve multiple functions simultaneously, including providing strong adhesion, improving conductivity, and providing electrochemical stability. A tradeoff between mechanical integrity and electrochemical performance in binders for lithium-ion batteries is one of the many challenges of improving capacity and performance. In this paper, we demonstrate a self-doped conjugated polymer, poly(9,9-bis(4′-sulfonatobutyl)fluorene-alt-co-1,4-phenylene) (PFP), which not only provides mechanical robustness but also improves electrode stability at temperatures as high as 450 °C. The self-doped PFP polymer is comprised of a conjugated polyfluorene backbone with sulfonate terminated side-chains that serve to dope the conjugated polymer backbone, resulting in stable conductivity. Composite electrodes are prepared by blending PFP with V2O5 in water, followed by casting and drying. Structural characterization with X-ray diffraction and wide-angle X-ray scattering shows that PFP suppresses the crystallization of V2O5 at high temperatures (up to 450 °C), resulting in improved electrode stability during cycling and improved rate performance. This study demonstrates the potential of self-doped conjugated polymers for use as polymeric binders to enhance mechanical, structural, and electrochemical properties.

Study on the Fading Mechanism of SiO-based Anodes Using Styrene Butadiene Rubber and Carboxymethyl Cellulose as Binders for Lithium-ion Batteries

Three kinds of SiO-based electrodes and one graphite electrode were fabricated using styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders. The cycling results showed that the more amount of SiO in the electrodes was, the faster the capacity of the electrode dropped and the lower coulombic efficiency of the electrode performed. Thus, it was the fading of SiO resulted in the SiO-based anodes reversible capacity dropping. In order to analyze the fading mechanism of the SiO-based anodes, SiO electrode was done 10% capacity lithiation/delithiation cycling, during which the volume change of the electrode should be negligible. The results showed that the voltage difference between the maximum and minimum values of the SiO anode cell kept increasing, which indicated that the SiO anode fading happened. The SEM images of SiO anodes illustrated that before cycling, the surface of SiO particles were smooth and tidy, and the SiO particles’ edge was sharp, while the surface of SiO particles became roughness, the edge was blurry, and there were fewer conductive additives on the SiO particles’ surface after cycling, which implied that electronic conductivity of the electrode became worse after cycling. It can be concluded that electronic conductivity played an important role in the electrode. We believe that boosting the electronic conductivity of the SiO-based electrode is one of the important methods to improve the cell cycle performance.

Real‐Time Dilation Observation of Si‐Alloy Electrode Using Thermally Treated Poly (Amide‐Imide) as a Binder for Lithium Ion Battery

Real time dilation behaviors of a Si‐Ti‐Fe‐Al alloy electrode adopting a poly (amide‐imide) binder were investigated to understand the effects of thermal treatment temperature for PAI binder on the electrochemical performance of the Si‐alloy electrode using an in‐situ electrochemical dilatometer. In situ measurement of the electrode thickness showed that the changes in the volume of the Si electrode was suppressed by heat treatment greater than 300 °C, which well agreed with the improved cycle performance of the Si‐alloy electrode thermally treated at the same temperature. Differential dilation plots of the Si‐alloy electrodes were found to reveal more detailed changes in the volume of the Si‐alloy electrode, thus showing that the enhanced mechanical strength of thermally treated PAI effectively could control the expansion and contraction of the Si‐alloy electrode and ensuring a more stable cycle performance of the Si‐alloy electrode.

Enhancing the electrochemical performance of lithium ion battery anodes by poly(acrylonitrile–butyl acrylate)/graphene nanoplatelet composite binder

Graphene nanoplatelet (GnP), which consists of small stacks of graphene, is used as a reinforcement to enhance the performance of the poly(acrylonitrile-butyl acrylate) (PANBA) binder in a lithium ion battery (LIB). To the best of our knowledge, this is the first time that a conductive nanofiller such as GnP has been used in a conventional water-dispersed polymer and applied as a binder for LIB. Our so-called PANBA/GnP nanocomposites are made with either 0.5 wt%, 1 wt%, or 2 wt% of GnP. The nanocomposites are synthesized via an in situ emulsion polymerization technique and are very well-dispersed, homogeneous, and stable for at least 6 months. The elongation and electrical conductivity of the PANBA/GnP nanocomposites exceed those of the PANBA non-filled polymer, and the PANBA/GnP nanocomposite binder ultimately enhances the electrochemical performance of the high-capacity silicon/graphite mixture anode.

High-performance Si flexible anode with rGO substrate and Ca2+ crosslinked sodium alginate binder for lithium ion battery

For the purpose of free-standing and stable silicon anode for lithium-ion battery, a silicon flexible anode is fabricated through a sequential filtration process and a post heat treatment. The reduced graphene oxide film is employed as a substrate, upon which the silicon nanoparticles, carbon nanotubes, and Ca2+ crosslinked sodium alginate are built. The prepared silicon flexible anode exhibits great electrochemical performance, due to the good flexibility and electric conduction of the reduced graphene oxide substrate, and the mechanical reinforcement of the strong three dimensional network formed by carbon nanotubes and Ca2+ crosslinked sodium alginate binder. The specific capacity of silicon flexible anode regarding the total mass of the electrode is as high as ∼1100 mAh g–1 at current density of 0.1 A g–1, 7 times higher than that of the traditional silicon anode with Cu foil current collector (∼150 mAh g–1). Moreover, it shows satisfactory rate capacity and favorable cycle stability (70% capacity retention after 100 cycles). Due to the flexibility, free-standing feature, and high electrochemical performance, the silicon flexible anode is potential for future applications in flexible lithium-ion battery and light-weight electronics.

Use of poly[ionic liquid] as a conductive binder in lithium ion batteries

In the present work, we studied the performance of different new binders based on poly[ionic liquids] (POILs) using a well-known negative electrode material such as Li4Ti5O12 (LTO) compound and ionic liquids (ILs) as solvents. We used an IL formed by Pip1,4Tf2N with N-butyl-N-methyl piperidinium (Pip1,4) as the cation and bis(trifluoromethanesulfonyl)imide (Tf2N−) as the anion. We tested two POILs as binders, composed of either LiTf2N, Pip1,4Tf2N, and PVDF or poly[diallyldimethylammonium]Tf2N (PDDA) as the polymer precursors (PVDF-IL and PDDA-IL, respectively). The best Li+ transport number as well as the smallest contact angle (electrolyte membrane) was obtained for the PDDA-IL polymer. The swelling effect better facilitates impregnation than the other polymers. The LTO/PDDA-IL combination showed the best specific capacity, 70 mAh g−1, and a stable prolonged cycling. We identified the TiIV/TiIII redox reversible processes by cyclic voltammetry experiments and the differential capacity profiles. Additionally, we measured the Li+ diffusion coefficient to be approximately 10−12 cm2 s−1. When different binders and IL-solvents are employed in a typical LTO cell, we demonstrated that the factors that determine cell performance are the ionic conductivity and the swelling effect.

The High Performance Silicon Anodes Including New Water Based Binder in Lithium Ion Batteries

Silicon based negative active material has very high charge capacity and is widely applied to a high capacity battery. However, the silicon based negative active material may expand by about 300% to about 400% during charge and discharge. Recently much attention has been devoted developing functional binders that can improve adhesion on silicon particle and accommodate substantial volume change during the charge/discharge process to maintain the electrode structure. The binders for silicon electrodes hold stiff polymeric backbones as like carboxymethyl cellulose (CMC), poly(acrylic acid), and alginate show better electrochemical performance than commercial binders. Despite promising progress, the current research on polymer binders for silicon is still far from the practical application where high mass loading is necessary for the high areal capacity. Here we report high performance silicon anodes using new water based binder including inorganic binder. This polymer matrix is compatible with lithium ion slurry manufacturing process, and can maintain both electric conductivity and mechanical integrity during the battery operation which results in good stability, rate capability, and cycle-life characteristics at high mass loading (>10mg/cm2).

Stability and rheological study of sodium carboxymethyl cellulose and alginate suspensions as binders for lithium ion batteries

ABSTRACTCurrently, the most widely used binder in batteries is polyvinylidene fluoride with N‐methyl‐2‐pyrrolidone used as a solvent. This solvent is flammable and toxic. Here, we focus on the suitability of using water‐soluble sodium alginate (Na‐alginate) and sodium carboxymethyl cellulose (Na‐CMC) as alternative biobased binder materials for the anodes of lithium ion batteries. It reduces the environmental impact of current manufacturing processes. However, control of the rheological characteristics of the binder whilst containing active and conductive additives is key for optimized processing. Here, we perform stability and rheological measurements of Na‐alginate and Na‐CMC solutions containing varying amounts of graphite and carbon black used as active and conductive materials, respectively. Compared with the benchmark Na‐CMC, the degree of flocculation shows that for the same concentration of binder in water, Na‐alginate suspensions are more stable. The rheology measurements show that Na‐alginate slurries have a higher viscosity than Na‐CMC at a shear rate of 50 s−1 with that for a 1.5% of Na‐alginate binder being 1.26 Pa s while for Na‐CMC it was for 0.20 Pa s. The loss factor was lower for Na‐Alginate, between 2 and 3 against between 2.9 and 3.3 for Na‐CMC, showing a more developed network structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46217.

Lithium sulfonate-grafted poly(vinylidenefluoride-hexafluoro propylene) ionomer as binder for lithium-ion batteries.

Lithium sulfonate-grafted poly(vinylidenefluoride-hexafluoro propylene) P(VDF-HFP) ionomers are synthesized through covalent attachment of taurine and used as binder for the LiFePO4 cathode of lithium-ion batteries(LIBs). The incorporation of the ionomer binders will add ionic conducting channels inside the electrodes, and prevent electrolyte depletion during rapid charge–discharge processes. It leads to an improved performance of LIBs using the ionomer binders including cycling stability and rate capability compared to that of LIBs using non-ionic binders (PVDF and PVDF-HFP). Therefore, the lithium sulfonate-grafted P(VDF-HFP) ionomers offer a new route to develop high-power LIBs.

The High Performance Silicon Anodes Including New Water Based Binder in Lithium Ion Batteries

Silicon based negative active material has very high charge capacity and is widely applied to a high capacity battery. However, the silicon based negative active material may expand by about 300% to about 400% during charge and discharge. Recently much attention has been devoted developing functional binders that can improve adhesion on silicon particle and accommodate substantial volume change during the charge/discharge process to maintain the electrode structure. The binders for silicon electrodes hold stiff polymeric backbones as like carboxymethyl cellulose (CMC), poly(acrylic acid), and alginate show better electrochemical performance than commercial binders. Despite promising progress, the current research on polymer binders for silicon is still far from the practical application where high mass loading is necessary for the high areal capacity. Here we report high performance silicon anodes using new water based binder including inorganic binder. This polymer matrix is compatible with lithium ion slurry manufacturing process, and can maintain both electric conductivity and mechanical integrity during the battery operation which results in good stability, rate capability, and cycle-life characteristics at high mass loading (>4.5 mg/cm2).

Electrochemical Decomposition of Poly(Vinylidene Fluoride) Binder for a Graphite Negative Electrode in Lithium-Ion Batteries

To clarify the electrochemical decomposition of poly (vinylidene fluoride) (PVdF) used as a binder for lithium-ion batteries while simultaneously verifying the correlation between electrode resistance and the PVdF content in graphite negative electrodes, in this study, we applied lithium bis (trifluoromethanesulfonyl) imide, which suppresses graphite exfoliation, as a salt. As a result, the electrochemical decomposition of PVdF was observed at a higher potential than that at which the electrolyte was decomposed during the reduction process. Additionally, this study demonstrated (through electrochemical impedance spectroscopy analysis) that electrode resistances such as solid electrolyte interface and charge transfer resistance proportionally increased with the PVdF content.