Conductive Polymer Binder Research Articles

High capacity and high density functional conductive polymer and SiO anode for high-energy lithium-ion batteries.

High capacity and high density functional conductive polymer binder/SiO electrodes are fabricated and calendered to various porosities. The effect of calendering is investigated in the reduction of thickness and porosity, as well as the increase of density. SiO particle size remains unchanged after calendering. When compressed to an appropriate density, an improved cycling performance and increased energy density are shown compared to the uncalendered electrode and overcalendered electrode. The calendered electrode has a high-density of ∼1.2 g/cm(3). A high loading electrode with an areal capacity of ∼3.5 mAh/cm(2) at a C/10 rate is achieved using functional conductive polymer binder and simple and effective calendering method.

3D Hierarchical Porous α‐Fe2O3 Nanosheets for High‐Performance Lithium‐Ion Batteries

To develop a long cycle life and good rate capability electrode, 3D hierarchical porous α‐Fe2O3 nanosheets are fabricated on copper foil and directly used as binder‐free anode for lithium‐ion batteries. This electrode exhibits a high reversible capacity and excellent rate capability. A reversible capacity up to 877.7 mAh g−1 is maintained at 2 C (2.01 A g−1) after 1000 cycles, and even when the current is increased to 20 C (20.1 A g−1), a capacity of 433 mA h g−1 is retained. The unique porous 3D hierarchical nanostructure improves electronic–ionic transport, mitigates the internal mechanical stress induced by the volume variations of the electrode upon cycling, and forms a 3D conductive network during cycling. No addition of any electrochemically inactive conductive agents or polymer binders is required. Therefore, binder‐free electrodes further avoid the uneven distribution of conductive carbon on the current collector due to physical mixing and the addition of an insulator (binder), which has benefits leading to outstanding electrochemical performance.

Toward practical application of functional conductive polymer binder for a high-energy lithium-ion battery design.

Silicon alloys have the highest specific capacity when used as anode material for lithium-ion batteries; however, the drastic volume change inherent in their use causes formidable challenges toward achieving stable cycling performance. Large quantities of binders and conductive additives are typically necessary to maintain good cell performance. In this report, only 2% (by weight) functional conductive polymer binder without any conductive additives was successfully used with a micron-size silicon monoxide (SiO) anode material, demonstrating stable and high gravimetric capacity (>1000 mAh/g) for ∼500 cycles and more than 90% capacity retention. Prelithiation of this anode using stabilized lithium metal powder (SLMP) improves the first cycle Coulombic efficiency of a SiO/NMC full cell from ∼48% to ∼90%. The combination enables good capacity retention of more than 80% after 100 cycles at C/3 in a lithium-ion full cell.

Invited Talk: In Situ Formed Si Nanoparticle Network with Micron-Sized Si Particles for Lithium-Ion Battery Anodes

Silicon (Si) appears to be an attractive candidate for lithium-ion batteries because it delivers 10 times greater theoretical (∼4200 mAh/g) specific capacity than that of a traditional graphite anode (∼370 mAh/g). Conductive polymer binder poly(9,9-dioctylfluoreneco-fluorenone-co-methylbenzoic ester) (PFM), was applied to micrometer-sized Si particles, fast fading was still observed due to the mechanical degradation of the Si electrode during cycling. Similarly, this has been demonstrated when using the conventional polymer binder poly(vinylidene fluoride) (PVDF) in prior works. In this contribution, we report a new strategy: by simply adding small amount of nanosized Si (n-Si) as an additive, along with the advantages of the conductive polymer binder (PFM), we are able to apply low-cost and low-specific-area micrometersized silicon particles (m-Si) into lithium-ion battery anodes with high specific capacity and significantly improved cycle life. It has been known that m-Si-based lithium-ion batteries fail in a few cycles due to the pulverization and fatigue of the electrode arising from stresses generated by the huge volume change of Si associated with the insertion and extraction of lithium. Figure 1a shows the schematic presentation of composite anode electrode using m-Si, the conductive polymer binder PFM, and conductive additive acetylene black (AB). AB is nanosized conductive additive used in lithium-ion batteries since its early days. While AB is used in the electrode, it does not contribute to energy storage and acts as a “passive” conductivity enhancer to facilitate electron transport from the active materials to the current collector, which improves electrode power capability. However, because AB has no mechanical binding force to either the Si or the conductive polymer binder PFM, during the large volume expansion of any individual m-Si particles (which is in cube micrometer range) both AB and polymer binders tend to be pushed away from the m-Si particles, leading to a void space or gap between the m-Si particles and the conductive network, leading to broken electrical connections. To maintain conductivity and power capability, a relatively large amount of AB needs to be added, which reduces the volumetric and gravimetric lithium-ion storage capacity. In contrast, when AB is replaced with n-Si particles, as shown in Figure 1b, n-Si tends to self-assemble on the surface of m-Si and form a new 3D network structure with m-Si during the lithiation process. This network forms physical connections between m-Si and helps to draw polymer binder back and holding the integrity of the electrodes during the large volume extraction process of delithiation.As shown in Figure 2a. The anode was composited of m-Si without any n-Si. Cycling of m-Si/AB/PFM started at high lithiation capacity but faded quickly to nearly zero within five cycles, with large initial irreversible capacity. In contrast, as n-Si replaced AB (Figure 2b), a high discharge capacity with only a small decrease was observed within five cycles with a high initial coulombic efficiency of 73%. More significantly, the charge capacity retention was kept up to 75% over 30 cycles.Here we described a facile but effective strategy utilizing micrometer-sized silicon materials as anodes for lithium-ion batteries. By simply adding nanosized silicon into micrometer-sized silicon particles, n-Si tends to self-assemble on the surface of m-Si and form a conductive 3D network during battery operation. The resulting composite electrode showed a significantly improved electrochemical performance, including a highly reversible Li storage capacity, good cycling performance, good rate performance, and high initial Coulombic efficiency. The entire fabrication process is scalable and does not involve expensive silicon growth steps.

Understanding the Performance of Sulfur Electrode Based on Polymer Binders, Sulfur Types and Electrolytes

Due to environmental concerns, it becomes more and more important to find alternative energy sources beyond fossil fuels with increasing demanding of energy. Lithium-ion-batteries (LIB) have drawn significant research attention due to their unique advantages of relatively high energy densities. Applications of LIB have been extended from consumer electronics to large-scale grid energy storage. However, the energy density of currently existing LIB remain insufficient to meet the requirements for applications in electric vehicles (EV) and hybrid electric vehicles (HEV), and thus it is desirable to develop much higher energy density rechargeable batteries with low cost. There has been significant progress in the development of high energy density anode materials such as Si-based alloy etc. over the recent years. However, the low capacity of cathode materials is still one of the major obstacles for developing high-performance batteries. Sulfur has been considered as one of the promising candidates of such cathode material due to its high theoretical capacity (1,675 mAh/g) and its natural abundance. Despite the above advantages, there are still many challenges in developing a practical lithium-sulfur battery for commercialization. As known so far that the problems of lithium-sulfur batteries include: 1) very poor conductivity of sulfur (10-16 S/m at 293 K); 2) large volumetric expansion upon lithiation (80%); 3) dissolution of the intermediate polysulfides during charge-discharge processes. These problems result in fast capacity fading and low Coulombic efficiency and therefore poor cycle performance of lithium-sulfur cells. Considerable efforts have been devoted to solve the above mentioned problems in the Li-S battery system such as encapsulating sulfur particles with conductive carbon, grapheme oxide, or polymer binder, adding confinement for sulfur particles such as loading sulfur into carbon nanotubes and designing core-shell structure etc.Conductive polymer, PEDOT, has been used in lithium-sulfur batteries to coat carbon/sulfur particles to minimize polysulfides dissolution and improve the electrochemical performance of Li-S batteries.The advantages of PEDOT with both good electrical conductivity and enhanced affinity for sulfur and polysulfides have been shown. In this study, we used PEDOT as polymer binder and commercial micrometric sulfur particles to study performance of Li-S batteries. The electrochemical performance of PEDOT based sulfur electrode was compared with that of conventional polymer binder of PVDF based sulfur electrode. Meanwhile, the impact of particle size of sulfur on the electrochemical performance was also studied by comparing commercial micrometric sulfur electrode and synthesized nanometric sulfur electrode. Finally, electrochemical performance of sulfur cells with high viscosity electrolyte and low viscosity electrolyte was compared to study the lithium ion diffusion impact on the polysulfides dissolution.In this study, the electrochemical performance of lithium-sulfur cells with different polymer binder (PVDF vs. PEDOT), different particle sized sulfur powder (micrometric vs. nanometric), and different electrolyte (DOL/DME vs. PEGDME) was investigated. We have demonstrated that PEDOT conductive polymer with commercial micrometric sulfur effectively improved the performance of Li-S batteries due to the bifunction of PEDOT with both good electrical conductivity and enhanced affinity for sulfur and polysulfides. The better cycle performance of micrometric sulfur cell than synthesized colloidal nanometric sulfur cell could be ascribed to the relatively lower sulfur utilization and better prevention of polysulfides dissolution. Meanwhile, the better performance of cells with PEGDME electrolyte than that of DOL/DME electrolyte is due to the larger viscosity, lower particle mobility, and lower polysulfides dissolution. The increased conductivity by conductive polymer and the electrolytes play important roles in the better cycle performance.

Solution Based Methods for Fast Determination of Lithium Insertion/Extraction Kinetics

Arguably, the electric and hybrid electric vehicles are the new frontiers in lithium batteries. As a new market it is distinctly different from mass produced microelectronics, not only in the energy per battery unit but also in the power performance requirements. Especially the required charging rates during deceleration and emergency charging, as well as, the discharge rates during startup from standstill are exciting challenges.[1,2] Consequently new chemistries and new materials morphologies like nanowires, shape controlled nanoparticle and size/shape controlled meso-scale agglomerates are being developed at an impressive rate. [3,4]The standard methodology to characterize the rate performance of these new materials is to fabricate composite electrodes that combine the electroactive materials with a conductive matrix and polymer binder.[5] This porous electrode structure is filled with electrolyte and thus electron and electrolyte transfer paths to the active material is established (Figure:Left). This brings about an important question inherent to the composite electrode, i.e. is the electrochemical performance limited by the active material or by the transport of electrons and/or ions in the electrolyte filled electrode structure?In response to this type of question we developed a series of techniques that allow the study of the redox process kinetics without the use of composite electrodes.[6-8] The key to our methodology is that the electrons are delivered and retrieved not by a solid-solid contact to the active material, but via a solution based redox couple (Figure:Right). As such our techniques are similar to the common potential step electrochemical approach while providing two unique advantages: A) the complete surface of the active particle experiences the same electrochemical potential at all times. B) the flux of lithium ions to and from the particle is unobstructed. In turn, this allows the study of materials like transition metal phosphates and silicates without the conductive coating required in the standard electrochemical analysis. Consequently, and possibly for the first time, the effect of the coating and its fabrication process on the lithium insertion/extraction kinetics can be studied. Another advantage of electron transport via redox species is that nanoparticles can be studied without concerns that they due to their small nature have not been properly incorporated in the electrode matrix.In this presentation we will display the analytical techniques that we have developed over the electron transport via solution based redox species theme. This includes in situ and ex situ detection of the reaction progress, as well as, several different redox systems appropriate for different positive electrode materials. Importantly, we will show that sub-second time resolution is possible using a photometric technique and that this approach yields considerably faster results, compared to the procedure required to produce test batteries. Further the reaction uniformity throughout the sample provides new kinetic insight, which can help to distinguish between possible reaction mechanisms, thus providing better fundamental understanding of both new and existing redox chemistries. References. [1] Baisden, A.C., Emadi, A. (2004) IEEE Trans Veh Tech, 53, 199. [2] Zaghib, K., et al. (2013) Materials, 6, 1028. [3] Bi, Z., et al. (2013) RSC Adv, 3, 19744. [4] Bresser, D., et al. (2012) J Power Sources, 219, 217. [5] Park, M., et al. (2010) J Power Sources, 195, 7904. [6] Trinh, N.D., et al. (2012) J Power Sources, 200, 92. [7] Kuss, C., et al. (2013) Chem Sci, 4, 4223. [8] Lepage, D., et al.(2014) J Power Sources, DOI: 10.1016/j.jpowsour.2013.12.054. Figure: Left: Standard battery. Right: Electron transport via solution based redox species. Arrows indicate transport (white: Electron; gray: Lithium) to the active material particle in the center of the image.

Toward high specific capacity and high cycling stability of pure tin nanoparticles with conductive polymer binder for sodium ion batteries

Pure Sn nanoparticles electrode with Poly(9,9-dioctylfluorene-co-fluorenone-co-methylbenzoic ester) (PFM) conductive binder was prepared and tested in sodium ion battery. It showed higher specific capacity and higher cycling stability without any carbon black compared with Sn/CMC (carboxy methylated cellulose) and Sn/PVDF (polyvinylidene fluoride) electrode. The Sn in Sn/PFM electrodes delivered 806 mAh g−1 at C/50 and 610 mAh g−1 at C/10. After 10 cycles at C/10, the capacity of Sn had no decay. SEM and TEM images showed that the Sn particles in Sn/PFM electrode were still in good conductive network despite big volume change, but parts of Sn particles in Sn/CMC or Sn/PVDF electrode are electrically isolated.

Intrinsically conductive polymer binders for electrochemical capacitor application

Little attention has been devoted so far to the development of new binders for electrode materials. In this work, an intrinsically conductive solution-processable polymer adhesive was prepared through the combination of polyaniline (PANI) with three organic additives as a ternary dopant for both conducting and gluing properties. With an optimized composition and no heat treatment process or conductive fillers, the conductive adhesive (Q-PANI) had a conductivity of 1.1 S cm−1 and 20–25% better adhesive ability than polyvinylidene fluoride insulating binder. Q-PANI showed good redox properties in an acidic electrolyte. Importantly, Q-PANI itself had a high specific capacitance of 108.7 F g−1. As a result, Q-PANI as a binder was found to significantly enhance the electrode performance of pseudocapacitive nanomaterials (polypyrrole nanospheres and PANI nanofibrils) and electric double-layer capacitive nanomaterials (carbon black). Thus, it is further expected that the combination of conductive and adhesive characteristics will make Q-PANI a very promising conductive paste and coating agent for various applications other than as an electrode binder.

High capacity and cyclic performance in a three-dimensional composite electrode filled with inorganic solid electrolyte

Three-dimensional (3-D) composite electrodes are prepared by one-step sintering of the laminated LiCoO2 and 0.44LiBO2·0.56LiF pellets, in which the amorphous 0.44LiBO2·0.56LiF solid electrolyte melts during the sintering process and fills the interspaces in the underlying highly conductive 3-D frame formed by LiCoO2. The one-step sintering process yields a compact electrode structure of ∼92% in relative density, which contains no electronic conductive additives or polymer binder. For better characterization of the composite electrode, liquid electrolyte is used in the battery test, but the vast majority of the active material is in the all-solid-state environment. The specific capacity of the 3-D composite electrode is dependent on the thickness of the composite electrodes. The 100-μm-thick 3-D composite electrode possesses high specific discharge capacity of 131 mAh g−1 at C/20 rate (96% utilization of the active material), excellent cycling performance for the measured 20 cycles and good rate capability at various discharge rates. The 200-μm-thick 3-D composite electrode delivers 88% of the theoretical capacity, i.e., 120 mAh g−1, and a significantly enhanced surface capacity of ∼9 mAh cm−2, which is much higher than that of the electrode used in the conventional all-solid-state lithium battery.

Development of Electronically Conductive Polymer Binders for Anode Materials in Lithium Ion Batteries

not Available.

Microwave-assisted synthesis of functionalized graphene on Ni foam as electrodes for supercapacitor application

The electrodes of supercapacitors were prepared via a simple and convenient strategy by microwave-assisted synthesis of functionalized graphene on Ni foam (FG-Ni foam) in ambient condition. The functionalized graphene on Ni foam was directly used as electrode for electrochemical double layer capacitance without any conductive agents and polymer binders, such as acetylene black and polyterafluoroethylene. The direct contact between FG and the foam current collector without any polymer binder helps to decrease the resistance of the FG-Ni foam electrode and improve the cycle life of the supercapacitor based on the FG-Ni foam electrodes. FG-Ni foam exhibits good electrochemical performance with a maximum specific capacitance of 265Fg−1 at the charge/discharge current density of 1Ag−1 with 5M NaOH as electrolyte. After 10,000 cycling GCD tests, a high level retaining specific capacitance of 261Fg−1 was obtained which still retained 97.7% of the initial capacity and the charge/discharge efficiency was approximate to 99.9%.

Conductive Polymer Binder-Enabled Cycling of Pure Tin Nanoparticle Composite Anode Electrodes for a Lithium-Ion Battery

Pure tin (Sn) nanoparticles can be cycled in stable and high gravimetric capacity (>500 mAh/g) with a polyfluorene-type conductive polymer binder in composite electrodes. Crystalline Sn nanoparticles (<150 nanometers, nm) were used as anode materials in this study. The average diameter of Sn secondary particles is 270 nm, calculated based on BET surface area. The composite electrodes contain a conductive polymer binder that constitutes 2% to 10% of the material, without any conductive additives (e.g., acetylene black). The electrode containing the 5% conductive binder showed the best cycling performance, with a reversible capacity of 510 mAh/g. Crystallinity of Sn particles gradually degrades during cycling, and pulverization of particles was observed after long-term cycling, leading to the capacity fade. The conductive polymer binder shows advantages over other conventional binders, such as Poly(vinylidene difluoride) (PVDF) and carboxymethylcellulose (CMC) binders, because it can provide electrical conductivity and strong adhesion during Sn volume change.

Octahedral Co3O4 particles threaded by carbon nanotube arrays as integrated structure anodes for lithium ion batteries

Octahedral Co3O4 particles threaded by ultra-long multi-walled carbon nanotube (MWCNT) arrays were prepared by a hydrothermal process and subsequent calcination. The Co3O4 octahedron with the (111) facets attaches to MWCNTs uniformly and closely. The composite can be used as an integrated anode for lithium ion batteries (LIBs) without any other additives (such as conductive additives and polymer binder), which exhibits a high reversible capacity of 725 mA h g(-1) at a current density of 100 mA g(-1), and excellent cyclic stability without capacity degradation over 100 cycles at a current density of 500 mA g(-1). The high performance can be attributed to the unique structure: (i) the ultra-long MWCNT array facilitates fast electron transfer; (ii) the tight adhesion between Co3O4 and MWCNTs prevents particle drifting and agglomeration; (iii) the free space between MWCNTs promotes fast ion transport and alleviates the large volume variation during discharge-charge process. This work demonstrates the great potential of MWCNT arrays as substrate and provides insights for the design and direct use of MWCNT array-based materials in LIBs, which will be helpful for future development of high-performance electrode materials.

Electrospun LiFe1−yMnyPO4/C Nanofiber Composites as Self‐Supporting Cathodes in Li‐Ion Batteries

AbstractLiFe1−yMnyPO4/C nanofiber composites are applied as cathode materials in Li‐ion batteries and their electrochemical properties are explored. Nanofiber meshes are synthesized via electrospinning of commercially available precursors (LiOH·H2O, FeSO4·7H2O, MnSO4·H2O, H3PO4, and polyvinylpyrrolidone). Nanofibers calcined at 850 °C under Ar/H2 (95/5 vol%) atmosphere are directly used as self‐supporting electrodes in Swagelok half cells without the need for any conductive additive or polymer binder. The morphology, phase, and chemical composition of as‐prepared and heat‐treated samples are analyzed by means of X‐ray powder diffraction, thermogravimetric analysis, and electron and scanning microscopy techniques. Brunauer–Emmett–Teller gas adsorption–desorption measurements show a high specific surface area (111m2 g−1) for LiFe0.5Mn0.5PO4. The influence of different Fe/Mn ratios on the morphology, electrical, and electrochemical performances are analyzed.

Conductive Polymer Binder for High Capacity Alloy Anode

not Available.

Intrinsic Surface Stability in LiMn2–xNixO4–δ (x = 0.45, 0.5) High Voltage Spinel Materials for Lithium Ion Batteries

This work reports the surface stability of the high vollage Li ion cathode LiMn2_,Ni,Ooh (x = 0.5, 0.45) by comparing thin fi lm and powder composite electrodes after cycling using X-ray photoelectron spectroscopy. The thin film electrodes offer the abili ty to probe the surface of the material without the need of a conductive agent and polymer binder typically used in composite electrodes. The resulls suggest that neither oxidation of PP6 to POF3 nor the decomposition of ethylene carbonate or dimethylene carbonate occurs on the surface of the spinel material. These resulls confirm the enhanced cycling stability and rate capability associated with the high vollage spinel material and suggests that the SE!IIayer fonns due to the reaction of electrochemically inactive components in composite electrodes with the electrolyte.

Secondary cell having a lithium intercolating manganese oxide

A secondary lithium ion cell having an anode, a cathode and a nonaqueous electrolyte wherein the cathode comprises sub-micron-size amorphous, microporous, lithium-intercalateable manganese oxide having an internal surface area greater than about 100 m2 /g. The cathode may include an electrically conductive lithium-intercalateable polymer binder. A sol-gel process for making the amorphous quatravalent manganese oxide is disclosed.