Carboxymethyl Cellulose Binder Research Articles

Enabling Increased Thickness Electrodes Using Binders with Discrete Functionalized Carbon Nanotubes

There are two major development goals currently being addressed by the Lithium Ion battery industry. Energy density (by increasing electrode thickness) and lower cell cost (primarily by reducing non-active components, such as current collectors and separator film). Increasing electrode thickness confronts a number of challenges including control of pasting rheology, maintaining paste integrity during drying, slitting, and battery assembly operations, as well as uniform electrical conductivity and ion transport. Aqueous binders can play a meaningful role in lowering cell cost by reducing manufacturing cost as they eliminate the need for complex equipment and also mitigate environmental hazards associated with organic solvents. Aqueous binders are currently used for graphite anodes, but they are also increasingly used in cathodes. In this paper, we present new results and understanding of aqueous binders in the context of discrete functionalized multiwall carbon nanotubes, MOLECULAR REBAR®, (MR), and their use in developing thicker electrodes. The discreet carbon nanotubes (MR) have been cleaned of catalytic residue and other carbonaceous debris and opened at both ends to allow electrolyte absorption and transport. They are on average 13nm in external diameter and about 900nm in length. The interior cavity diameter is about 5 nm. The surfaces of these tubes are selectively modified to facilitate their role within electrodes, allowing us to tailor lithium transport characteristics, electron transport, and mechanical properties to the desired battery performance targets. Insights will be provided here on the evolution of multi-scale structure in anodes developed with aqueous binder compositions incorporating various ratios of MR combined with conductive carbon black, graphite particles, and various carboxymethylcellulose (CMC) - styrene butadiene rubber (SBR) ratios. In our process, the MR is dispersed as individual tubes in both CMC and SBR binder components. Their content was varied within each polymer phase to study effects on the microstructure. The CMC-MR composite (0-10% wt. relative to CMC) is found to uniformly coat the graphite particles with thickness approximating individual tube diameters while still maintaining a random distribution of the discrete tubes important to ionic conductivity. The SBR–MR composite (0 -10% wt. MR relative to SBR) forms reinforced, elastic, and when MR is added - electron conductive bridges which connect the CMC coated graphite particles and adhere to current collector. Through formulation of SBR-MR special care is taken to ensure that MR does not agglomerate independently and remains intimately entwined within the consolidated latex agglomerate. Determinations were made of the adhesive and cohesive strengths of the dried pastes, before and after calendaring, using a newly developed mechanical test that is more accurate than the simple peel test. The nature of paste shedding or delamination (i.e. roll-to-roll and cell coiling process-ability) is controlled by both the magnitude of the adhesion and cohesion strength and their ratio. Failure analyses of the dried electrodes upon slitting or bending were conducted by electron microscopy and will be illustrated. Both the adhesion characteristics of the pastes at the copper current collector surface and the cohesive failure of the graphite-graphite particles were examined. We learned that the adhesive strength of the graphite coated particles to copper is influenced by the CMC-SBR ratio and is enhanced with the presence of MR. Clear evidence will be presented on the relative sequence of failure events in slitting operations. The cohesive bond strength is also a function of the CMC adhesion to graphite and the characteristics of SBR itself bridging the CMC coated graphite particles. Of importance, is that the discrete carbon nanotubes maintain electrical conductivity while stretching those bonds that cannot be obtained with just conductive carbon black. This means that MR additions to CMC-SBR binders result in stronger and tougher formulations that retain electron transport especially under high volumetric strains, such as strains experienced with higher capacity anode materials like high silicon content graphite. Conventional testing of electrode performance as a function of thickness with the new binder formulations containing MR reveal more consistent behavior and improved cycling of the electrodes. Examination of the solid electrolyte interface layer formation after 300 cycles at room temperature by electron microscopy have shown much smoother, more uniform coverage than graphite anodes without the discrete carbon nanotubes. The ability to control the placement of discrete, clean, functionalized carbon nanotubes in binder formulations has opened new windows to the design of binders for batteries with improved performance and lower cost. There is a natural extension of the science and technology discussed here to other binders such as polyacrylic acid and to advancing aqueous binders for cathode materials.

Potassium-Ion Intercalation into Graphite for High-Voltage and High-Power Batteries

Rechargeable lithium batteries have been recognized as the most successful and sophisticated energy storage devices since their first commercialization in 1991 by Sony. Furthermore, they are used now as an alternative power source for electric motors instead of combustion engines equipped with a fuel tank.1 Electric vehicles equipped with large-scale lithium batteries as power sources have been introduced to the automotive market, promising to reduce the dependence of transportation on fossil fuels in the future. The element lithium is widely distributed in the Earth’s crust and sea, but is not regarded as an abundant element. In contrast, potassium is the seventh most-abundant element in the continental crust and a major element in oceanic waters.2 Furthermore, the standard potential of potassium is lower than that of lithium in propylene carbonate.3 In this study, the electrochemical potassium intercalation into graphite negative electrode is investigated to realize rechargeable potassium-ion batteries. The working electrodes consisted of 90 wt% graphite and 10 wt% binder: poly(vinilydene fluoride) (PVdF), carboxymethyl cellulose (CMC), or sodium polyacrylate (PANa). Metallic potassium foil was used as a counter electrode. The galvanostatic charge/discharge measurements were carried out at C/10 (25 mA g-1) in the voltage range of 0-2 V vs. K/K+. In situ X-ray diffraction (XRD) was conducted for electrodes in K cell. The surface of the electrodes after cycles was characterized by hard X-ray photoelectron spectroscopy (HAXPES), soft X-ray photoelectron spectroscopy (SOXPES), time-of-flight secondary ion mass spectrometry (TOF-SIMS) and scanning electron microscopy (SEM). In Fig. 1a, graphite electrode with PANa binder shows better cyclability than those of electrodes with PVDF and CMC binder due to the interfacial modification, with delivering ca. 250 mAh g-1 of reversible capacity and excellent capacity retention in 1 mol l-1 KFSI EC:DEC solution. In addition, graphite electrode with PANa demonstrates ultrahigh oxidation rate capability of depotassiation up to 40C (11160 mA g-1) rate in a non-aqueous potassium cell as shown Fig. 1b. Furthermore, in-situ XRD confirms reversible phase transition from graphite to different stage intercalation compounds, such as KC8 and KC24. In addition, HAXPES results demonstrate that surface of a graphite electrode is covered with a passive layer after 1st cycle, and no obvious difference between 1st and 10thcycle is observed in the surface layer. From these results, we will further discuss graphite negative electrode for potassium-ion batteries as next-generation battery beyond lithium-ion and sodium-ion.

CMC As Effective Binder for High-Voltage LiNi0.5Mn1.5O4 Electrodes

The development of environmentally friendly, low cost and safe lithium-ion batteries (LIBs) with increased energy and power densities is one of the key challenges to boost the progress of sustainable transport. The energy density of a battery can be enhanced by using high-voltage and/or high-capacity cathode materials. LiNi0.5Mn1.5O4 (LNMO) is one of the most promising high-voltage cathode materials for its high theoretical specific capacity of 146.7 mAh g-1 and high nominal operating voltage of 4.7 V vs. Li+/Li [1]. Combining LNMO with a graphite anode should allow full cells with specific energies higher than 200 Wh kg-1, in order to extend the electric driving range of hybrid electric vehicles (HEVs). However, despite the LNMO's appealing properties, e.g., low cost, environmental friendliness, excellent rate capability and good safety, the major concern that limits the use of this material is its reactivity towards conventional electrolytes, which are prone to decompose at high potentials leading to the formation of a thick surface layer and capacity loss, both being detrimental for the cycling performance of the electrode. Since advanced electrolytes stable over 5 V are under investigation but not yet available [2], several strategies have been pursued to address the interface instability issues, such as the partial substitution of Ni and Mn by dopants and surface modifications [3], the coating with reduced graphene oxides to enhance conductivity and protect the electrode from the reaction with the electrolyte [4-6], and the use of additives in conventional electrolytes [2]. The water-soluble binder, namely sodium carboxymethylcellulose (CMC), is here proposed instead of polyvinylidene fluoride (PVdF), the most common binder in LIBs, for the making of LNMO-composite electrodes. CMC is more eco-friendly than PVdF and appears to be a very promising alternative binder for high-voltage cathode materials [7], even for LiNi0.4Mn1.6O4 [8] and LiNi0.5Mn1.5O4 [9]. This study demonstrates the strong impact of the CMC binder on LNMO-composite electrodes that perform notably better than LNMO-PVdF electrodes, especially upon long cycling, showing higher capacity retention in half cells vs. Li/Li+ in conventional electrolyte (EC:DMC – LiPF6), both at 20° and 40°C. CMC promotes a homogeneous carbon dispersion that may improve the percolating network and, hence, the cycling performance of the electrodes. Therefore, CMC prevents the unwanted reactions between the electrode and electrolyte upon high-operating voltage, as also evinced by the ex-situSEM and XPS characterization of cycled electrodes. Furthermore, graphite//LNMO-CMC full cell was assembled and tested according to the DOE battery test for plug-in HEVs and the preliminary and very promising results are here reported.

Systematic Investigation of Binders for Silicon Anodes: Interactions of Binder with Silicon Particles and Electrolytes and Effects of Binders on Solid Electrolyte Interphase Formation.

The effects of different binders, polyvinylidene difluoride (PVdF), poly(acrylic acid) (PAA), sodium carboxymethyl cellulose (CMC), and cross-linked PAA-CMC (c-PAA-CMC), on the cycling performance and solid electrolyte interphase (SEI) formation on silicon nanoparticle electrodes have been investigated. Electrodes composed of Si-PAA, Si-CMC, and Si-PAA-CMC exhibit a specific capacity ≥3000 mAh/g after 20 cycles while Si-PVdF electrodes have a rapid capacity fade to 1000 mAh/g after just 10 cycles. Infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) reveal that PAA and CMC react with the surface of the Si nanoparticles during electrode fabrication. The fresh Si-CMC electrode has a thicker surface coating of SiOx than Si-PAA and Si-PAA-CMC electrodes, due to the formation of thicker SiOx during electrode preparation, which leads to lower cyclability. The carboxylic acid functional groups of the PAA binder are reactive toward the electrolyte, causing the decomposition of LiPF6 and dissolution of SiOx during the electrode wetting process. The PAA and CMC binder surface films are then electrochemically reduced during the first cycle to form a protective layer on Si. This layer effectively suppresses the decomposition of carbonate solvents during cycling resulting in a thin SEI. On the contrary, the Si-PVDF electrode has poor cycling performance and continuous reduction of carbonate solvents is observed resulting in the generation of a thicker SEI. Interestingly, the Lewis basic -CO2Na of CMC was found to scavenge HF in electrolyte.

On the Key Role of the Carbon Conductive Additive on the Performance of Si-Based Electrodes with High Areal Capacities

Silicon-based electrode is a promising candidate in lithium-ion batteries (LIB) due to its significantly higher gravimetric capacity (3579 mAh g-1) in comparison to that of graphite (372 mAh g-1). However, during the process of lithiation/delithiation, the silicon material suffers from a huge volume change which has a negative repercussion on the electrode cycle life through the fracturing of the silicon particles and of the solid electrolyte interphase layer (SEI) and the disconnection of inter-particle contacts. Our group has recently shown that high performance silicon-based anodes can be achieved by combining (i) the use of high-energy ball-milling as a cheap and easy process to produce nanostructured silicon powder, (ii) the processing of the electrode with carboxymethylcellulose (CMC) binder at pH 3 condition, which has been proved to be able to promote the covalent grafting of the CMC to the Si particles; (iii)the use of fluoroethylene and vinylene carbonates (FEC/VC) electrolyte additives resulting in a more stable SEI. (1) One of the biggest challenges of commercializing silicon anodes is to reach a high areal capacity of more than 4 mAh cm-2, in order to achieve a volumetric energy density improvement over the use of conventional graphite-based anodes. Electrodes with such high areal capacity require careful design of their formulation at different scales, and in particular a special attention must be paid to the tailoring of durable intimate contacts between the active material particles and the conductive additive network so that sufficient electron transfer could be achieved throughout the electrode from the copper current collector.(2) Here, silicon-based electrodes of various areal capacities were prepared by using either carbon black (Super P, Timcal), vapor grown carbon nanofibers (VGCFs, Showa Denko), or graphite nanoplatelets (GM15, XGSciences) as conductive additive. These electrodes were examined by using SEM, XRD, Raman, electrical four-probe method and galvanostatic charge/discharge tests. The objective was to establish the relationships between the characteristics of the carbon additive and the electrochemical performance of the electrode. It was observed that the electrical conductivity, capacity retention, and coulombic efficiency of the silicon electrode are significantly affected by the shape, surface area, particle size and crystallinity of the used carbon additives. Spherical-shaped carbon black particles tend to agglomerate and fail in creating a conductive network resilient to the silicon particles’ volume variation. In contrast, vapor grown carbon nanofibers maintain more durable contacts with silicon particles by forming a more resilient conductive network due to their wire-like structure compared to carbon black.(3) Graphite nanoplatelets also create a continuous conductive network and seem to limit the mechanical degradation of the electrode coating, likely by playing the role of electrically conducting lubricant. (4) These results demonstrate that the choice of the conductive additive is of crucial importance for the optimization of silicon negative electrodes with commercially relevant areal capacities. References (1) Gauthier, M.; Mazouzi, D.; Reyter, D.; Lestriez, B.; Moreau, P.; Guyomard, D.; Roué, L. Energy Environ. Sci. 2013, 6(7), 2145. (2) Mazouzi, D.; Karkar, Z.; Reale Hernandez, C.; Jimenez Manero, P.; Guyomard, D.; Roué, L.; Lestriez, B. J. Power Sources 2015, 280, 533–549. (3) Lestriez, B.; Desaever, S.; Danet, J.; Moreau, P.; Plée, D.; Guyomard, D. Electrochem. Solid-State Lett. 2009, 12(4), A76. (4) Nguyen, B. P. N.; Gaubicher, J.; Lestriez, B. Electrochimica Acta 2014, 120, 319–326. Figure 1

Electrochemical properties of Sn-Co electrode with various kinds of binder materials for sodium ion batteries

Discharge–charge properties of Sn-Co anode materials with various kinds of binders [polyvinylidene difluoride (PVdF), polyacrylic acid (PAA), sodium polyacrylate (PAANa), sodium carboxymethyl cellulose (CMC), and polyimide (PI)] for sodium ion batteries were investigated to determine the correlation between cycle performance and the properties of electrode with binder. Sn-Co electrodes with PAA or CMC binders exhibited better cycle properties (discharge capacities of more than 400mAh/g up to 20 cycles) than with PVdF, PAANa, or PI. These cycle properties with PAA or CMC were due to smaller changes in the electrode volume that occurred during cycling, as revealed by in situ light microscopy.

Sodium titanate cuboid as advanced anode material for sodium ion batteries

Sodium titanate (Na2Ti6O13) cuboid is successfully prepared and employed for anode electrode materials in sodium-ion batteries (SIBs). Their sodium storage properties are presented by undertaking polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC) as different binders. At a current density of 0.1 C, the sodium titanate cuboid with CMC and PVDF exhibits discharge capacity of 269.5 mAh g−1 and 251.0 mAh g−1, respectively. At the 200th charge/discharge cycle, the reserved discharge capacity for Sodium titanate cuboid electrode with CMC binder is 173.6 mAh g−1, amounting to a capacity retention of 94.4%, much higher than that employing PVDF as binder (the discharge capacity of 69.3 mAh g−1 and the capacity retention of 54.1%). The rate capability test and the Coulombic efficiency data also manifest that the Sodium titanate cuboid utilizing CMC as binder is superior to the ones with PVDF. These enhanced electrochemical performance mainly derive from the strong cohesive strength of CMC binder and the swellability of PVDF binder, verifying the importance of a binder to the optimization of sodium storage behavior.

Ionically‐Functionalized Poly(thiophene) Conductive Polymers as Binders for Silicon and Graphite Anodes for Li‐Ion Batteries

AbstractNext‐generation anode materials for Li‐ion batteries such as silicon can lead to ten times more capacity than the state‐of‐the‐art graphite. However, novel binders are required to overcome the detrimental effects of volume changes during battery cycling of silicon because of the poor chemical interaction and electrical conductivity between silicon and the binder. Most studies focus on either ionic binders or electrically conductive binders, but herein it was demonstrated that a new family of polymers based on electrically conductive poly(thiophene) functionalized with an ionic alkyl carboxylate groups of various lengths can successfully work as multifunctional binders for silicon and commercial graphite anodes in Li‐ion battery half‐cells. It was determined that the polymer with shorter side chain (PT‐3‐LiA) gives the highest reversible capacity upon pairing with graphite or silicon, reaching 3000 mAh g−1 in the case of the latter, a capacity 500 mAh g−1 (≈22 %) higher than those obtained with the electrically, but non‐ionically, conductive PEDOT:PSS binder and the ionically, but non‐electrically, conductive sodium carboxymethyl cellulose (NaCMC) binder. It is demonstrated that the superior performance of this new type of multifunctional binders can be attributed to their ability to maintain their doping level and conductivity as well as due to good interaction with the silicon surface during cycling.

Cyanoethylated Carboxymethyl Chitosan as Water Soluble Binder with Enhanced Adhesion Capability and electrochemical performances for LiFePO4 Cathode

Cyanoethylated carboxymethyl chitosan (CN-CCTS) has been synthesized through a straightforward cyanoethylation reaction by reacting CCTS with acrylonitrile in NaOH aqueous solution. CN-CCTS shows improved adhesion strength of 0.047N/cm as compared with 0.013N/cm for CCTS after introducing cyanoethyl group in the chemical structure of CCTS. The electrochemical performances of LiFePO4 electrode with CN-CCTS binder have been investigated and compared with those using water soluble sodium carboxymethyl cellulose (CMC) and non-aqueous polyvinylidene difluoride (PVDF) binder. LiFePO4 electrode with CN-CCTS exhibits better cycling stability and rate capability, retaining 56.3% capacity of C/5 at 5C rate as compared with 48.4% and 32.8% for CMC and PVDF, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy measurement reveal that LiFePO4 electrode with CN-CCTS has a more favorable electrochemical kinetics than that with CMC and PVDF, thus better rate capability.

Impact of the Film Storage Conditions on the Performance of Si-Based Anodes for Li-Ion Batteries

For several years, great attention has been paid to silicon as negative electrode material for Li-ion batteries, due to its very high gravimetric capacity (3579 mAh g-1) in comparison to that of graphite (372 mAh g-1). However, Si electrodes suffer from poor cyclability due to the large volumetric expansion (up to 300%) of Si upon its lithiation, resulting in the electrode architecture disintegration, and in the instability of the solid electrolyte interphase (SEI). We have recently shown that low-cost and high-performance Si-based electrodes can be obtained by combining (i) the use of ball-milled (nanocrystalline) Si powder resulting in a smoother phase transition; (ii) the processing of the electrode at pH 3 with carboxymethylcellulose (CMC) binder favoring the covalent grafting of the CMC to the Si particles; (iii) the use of fluoroethylene and vinylene carbonates (FEC/VC) electrolyte additives resulting in a more stable SEI.1 In the present study, it is shown for the first time that the storage conditions of the Si-based film before assembling in the electrochemical cell has also a major impact on the electrode performance. This is illustrated in Fig. 1 which compares the evolution of the discharge capacities with cycling* of ball-milled Si-based electrodes prepared after storage at room temperature of the composite film** (a) for 1 day and 55 days in air and (b) for 6 days in air (10-15% relative humidity) and in humid air (70% relative humidity). It clearly appears that the film storage in air has a very positive impact on the electrode cycle life, which is accentuated under humid atmosphere. A possible explanation is that during the film storage, water molecules from air react with the film and modify the chemical links between the Si particles and the CMC binder. This tends to be confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis of the composite electrodes***. Indeed, as shown in Fig. 2, a significant increase of the peak centered at 1630 cm− 1 assigned to the stretching band of the carboxyl group of CMC is observed for the film stored in humid air, while the peak centered at 1750 cm-1assigned to a covalent bond between Si and CMC is decreased. This suggests an increase of the hydrogen bonds between the Si particles and CMC binder (Fig. 3), which could increase the deformability of the electrode, favorable to its mechanical stability with cycling. We believe that an optimum covalent / hydrogen bond ratio is required to obtain a film sufficiently rigid to maintain electronic connections but flexible enough to vary in volume without breaking/peeling off during cycling. * Electrodes were cycled in Swagelok-type cells with Li as counter/ref. electrode at full capacity between 1 and 0.005 V at a current density of 480 mA g-1 of Si. The electrolyte was LP30 + 10wt%FEC. ** (Si + CB + CMC+ pH3 buffer salts) in a weight ratio of 73.1/11.0/7.3/8.6. The Si loading was 1 mg/cm2. *** Electrodes were dried at 100°C under vacuum prior to ATR-FTIR analysis (same procedure as prior electrode cycling). Reference 1. M. Gauthier, D. Mazouzi, D. Reyter, B. Lestriez, P. Moreau, B. Lestriez, D. Guyomard, L. Roué. A low-cost and high-performance Si-based electrode for Li-ion batteries. Energy Environ. Sci. 6 (2013) 2145–2155. Figure 1

Effect of Crosslinking of Guar Gum As a Bio-Derivative Binder for Negative Electrodes of Lithium-Ion Batteries

Nowadays, large-sized lithium-ion batteries (LIB) for electric vehicles (EV) and energy storage systems (ESS) require extraordinary long-cycled, high-powered, and high-capacity, when compared to small-sized LIBs for mobile devices. In addition, it is also necessary to actively respond to environmental problems by applying green materials. From our previous results, guar gum binders, branched polysaccharides, facilitated the transport of lithium ions in Li4Ti5O12(LTO) electrodes than conventional carboxymethyl cellulose (CMC) binders, linear polysaccharide, even though their adhesive strength were not as strong as CMC[1]. Unlike polyvinylidene fluoride (PVdF), guar gum binder was soluble in water, thus allowing the LIB manufacturing process to be environmentally friendly. In this study, we investigate the effect of crosslinking of the guar gum binder on their mechanical properties in the LTO electrodes. To evaluate the effect of these crosslinking, a variety of physical and electrochemical characterization are applied. Reference 1. Bo-Ram Lee, So-Jin Kim and Eun-Suok Oh, Journal of the Electrochemical Society, 161, A2128-A2132 (2014)

Environmental Friendly Electrode Preparation for Hybrid Battery-Supercapacitors Based on Li3V1.95Ni0.05(PO4)3/C and Activated Carbon

In the last years, hybrid battery-supercapacitors have been a rising interest toward the improvement of both the energy density and power density in comparison to the classical systems [1]. By using Li-insertion materials and activated carbon it is possible to develop high energy and high power density Li-ion supercapacitors. Among the various numbers of Li-ion materials, Li3V1.95Ni0.05(PO4)3/C shows excellent performances at very high C-rates, with very high specific discharge capacity (93 mA h g-1 at 100 C) and a capacity retention of 97% after 1000 cycles [2]. Most of the currently used Li-ion battery electrodes are based on poly(vinylidene difluoride) (PVDF) due to its good electrochemical stability and binding capability within the electrode composite. However, the cost and the environmental impacts of these widely used PVDF based electrodes are still a concern in the battery industry. Thus, lot of effort has been put toward the pursuit of an environment-friendly, cost-effective binder for lithium-ion batteries, such as carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) [3].In this study, the effect of CMC and PAA binders in the battery-like counter part on the mechanical and electrochemical behaviour in the hybrid battery-supercapacitor electrodes is explored (see Table 1). In particular, Li3V1.95Ni0.05(PO4)3/C has been studied both as high energy and high power anode and cathode, between 3.0-1.5 and 3.0-4.3 V vs. Li+/Li. Commercial activated carbon (AC) (Haycard) and LP30 (Merck) has been used as counter electrode and electrolyte, respectively. Furthermore, the functionalization of PAA during the electrode preparation will be investigated and shown during the presentation. Table 1. Electrode compositions. Compositions Active material LVNP / wt.% Conductive agent Super P / wt.% Binder /wt.% 1 80 10 9% CMC + 1% SBR 2 85 5 9% CMC + 1% SBR 3 86 5 9% PAA References [1] D. Cericola, R. Kötz, Electrochim. Acta 72 (2012) 1–17. [2] M. Secchiaroli, G. Giuli, B. Fuchs, R. Marassi, M. Wohlfahrt-Mehrens, S. Dsoke, DOI: 10.1039/c5ta00976f. [3] J. Chong, S. Xun, H. Zheng, X. Song, G. Liu, P. Ridgway, J. Q. Wang, V. S. Battaglia, J. Power Sources 196 (2011) 7707– 7714. Acknowledgments Financial support from the German Federal Ministry of Education and Research (BMBF) under the grant 03EK3021 is gratefully acknowledged.

DC 열플라즈마를 이용하여 제조된 산화철 나노입자의 광 전기화학적 물분해 효율 증가연구

In this research, hematite nanoparticles were synthesized by DC thermal plasma process to increase the overall surface area. The effect of binders on hematite electrodes was investigated by changing the type and composition of binders when preparing electrodes. Nitrogen gas was also added to the DC thermal plasma process in order to dope the hematite with N for enhancing photoelectrochemical properties of hematite nanoparticles. The efficiency of water splitting reaction was measured by linear sweep voltammetry (LSV) under solar simulator. In LSV measurements, the onset potential and maximum current density at a fixed voltage were measured. The durability of electrodes was checked by repeating LSV measurements. CMC (carboxymethyl cellulose) binder with 50 : 1 composition exhibits the highest current density of 12 mA/cm 2 and CMC binder

Cathodically induced antimony for rechargeable Li-ion and Na-ion batteries: The influences of hexagonal and amorphous phase

Cathodic corrosion, a green electrochemical method, has been employed to obtain Sb nanomaterials utilized as anode material for lithium-ion batteries and sodium-ion batteries. Interestingly, two different corrosion mechanisms are found, coming from the impact of electrolyte, resulting in the formation of hexagonal and amorphous Sb in aqueous and organic solution, respectively. With the help of water-soluble carboxymethyl cellulose binder and the electrolyte additive fluoroethylene carbonate, both hexagonal and amorphous Sb electrodes exhibit good cycling stability when utilized as anode materials for lithium-ion batteries and sodium-ion batteries. Additionally, both the hexagonal and amorphous Sb electrodes show very good rate capability in lithium-ion batteries. Even at high current density (2000 mA g−1), the hexagonal and amorphous Sb give reversible capacities of 422 and 379 mA h g−1, respectively. Surprisingly, when used as anode materials for sodium-ion batteries, the hexagonal Sb electrode exhibits a good rate performance of 632, 625, 569, 515 and 426 mA h g−1 at a current density of 100, 200, 500, 1000, and 2000 mA g−1, respectively. However, limited rate performance is observed from the amorphous Sb electrode in case of sodium-ion battery due to the large impedance.

Engineering study on TiSnSb-based composite negative electrode for Li-ion batteries

Micrometric TiSnSb is a promising negative electrode material for Li-ion batteries when formulated with carboxymethyl cellulose (CMC) binder and a mixture of carbon black and carbon nanofibers, and cycled in a fluoroethylene carbonate (FEC)-containing electrolyte. Here, other binder systems were evaluated, polyacrylic acid (PAAH) mixed with CMC, CMC in buffered solution at pH 3 and amylopectin. However CMC showed the better performance in terms of cycle life of the electrode. Whatever the binder, cycle life decreases with increasing the active mass loading, which is attributed to both the precipitation of liquid electrolyte degradation products and to the loss of electrical contacts within the composite electrode and with the current collector as a consequence of the active particles volume variations. Furthermore, calendaring the electrode unfortunately decreases the cycle life. The rate performance was studied as a function of the active mass loading and was shown to be determined by the electrode polarization resistance. Finally, full cells cycling tests with Li1Ni1/3Co1/3Mn1/3O2 at the positive electrode were done. 60% of the capacity is retained after 200 cycles at the surface capacity of 2.7 mAh cm−2.

Water‐Soluble Conductive Composite Binder Containing PEDOT:PSS as Conduction Promoting Agent for Si Anode of Lithium‐Ion Batteries

AbstractA novel water‐soluble conductive composite binder consisting of carboxymethyl cellulose (CMC) as binder and aqueous poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as conduction‐promoting agent is reported for the Si anode of Li‐ion batteries. The introduction of conductive PEDOT:PSS into a water‐soluble binder facilitates the formation of homogenous and continuous conducting bridges throughout the electrode and increases the compaction density of the electrode by reducing the content of the commonly used conducting agent of acetylene black. Galvanostatic testing, cyclic voltammetry and electrochemical impedance spectroscopy measurements show that the electrodes using the composite binder exhibit higher initial Coulombic efficiencies, better cycling and rate performance, and more favorable electrochemical kinetics compared with the electrodes using CMC binder with acetylene black conducting agent.

Mechanism of interactions between CMC binder and Si single crystal facets.

Interactions of the active material particles with the binder are crucial in tailoring the properties of composite electrodes used in lithium-ion batteries. The dependency of the protonation degree of the carboxyl group in the carboxymethyl cellulose (CMC) structure on the pH value of the preparation solution was investigated by Fourier transform infrared spectroscopy (FTIR). Three different distinctive chemical states of CMC binder were chosen (protonated, deprotonated, and half-half), and their interactions with different silicon single crystal facets were investigated. The different Si surface orientations display distinct differences of strength of interactions with the CMC binder. The CMC/Si adhesion forces in solution and Si wettability of the silicon are also strongly dependent on the protonation degree of the CMC. This work provides an insight into the nature of these interactions, which determine the electrochemical performance of silicon composite electrodes.

Effect of a thin ceramic-coating layer on thermal and electrochemical properties of polyethylene separator for lithium-ion batteries

In this paper, a new kind of ceramic-coating separator for lithium-ion batteries is successfully prepared by forming a ceramic layer consisted of Al2O3 powder, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) mix binder onto one side of pristine PE separator. During the preparation of the separator, water is used as solvent and a very small amount of SBR–CMC mixture is applied as binder to obtain better thermal stability. The effect of thickness of the ceramic-coating layer on its thermal stability, physical properties and electrochemical performance is also investigated. The results clearly showed that the ceramic-coating separator with SBR–CMC binder has wonderful thermal stability, good wettability and high uptake of liquid electrolyte. Pouch cell tests with the ceramic-coating separator also show excellent stable cycle performance.

A free-standing, flexible lithium-ion anode formed from an air-dried slurry cast of high tap density SnO2, CMC polymer binder and Super-P Li

A free-standing electrode film composed of high tap density SnO2 particles and carboxymethyl cellulose binder with Super-P Li (SP-Li) conductive carbon was formed from an aqueous slurry cast by doctor-blading. Upon air-drying, the free-standing film spontaneously evolved via delamination from the substrate as the slurry solvent evaporated. The electrodes cut from the free-standing film were ∼5 μm thick with a SnO2 loading of ∼0.5 mg cm−2. The films were found to be easily handled, flexed and folded. For evaluation of the durability of the free-standing films, the tensile strength and elongation at break were measured: 13 MPa and 1.7%. The robustness of the electrically conductive network was measured with a four-point probe: the initial electrical resistivity of the film (0.6 Ω cm) was observed to increase by 6% after folding, applying pressure to the crease and unfolding. When tested in a coin cell, the electrode cycled stably with near 100% coulombic efficiency at up to 2 C and without capacity fade for 100 cycles at 1 C. To adjust the areal capacity of the cell, multiple free-standing films could be stacked. An electrode formed from several stacked films with an active material mass loading of greater than 4 mg cm−2 was found to cycle stably at 2.6 mA h cm−2 tested at 0.33 mA cm−2 current density. For evaluating cycling performance of the electrode while flexed, an electrode was placed in a once-folded pouch cell for testing at 1 C and cycled stably for 20 cycles before slight capacity fade was observed. For free-standing electrodes, 1D or 2D carbons such as carbon nanotubes (CNT) or graphene are commonly used to provide both mechanical strength and electrical conductivity. Here, CNTs were substituted for the SP-Li and similar free-standing films were made and compared. With CNT, the electrode strength at break as well as the electronic conductivity increased, but, despite this, the cycling performance of the electrodes made using the low-cost SP-Li carbon exceeds that of the electrodes made with orders-of-magnitude more expensive 1D carbon.

Effects of Electrolytes, Additives, and Binders on Cycling Performance of Hard Carbon for Na-Ion Batteries

Lithium resources do not seem particularly limited but the access to this essential resource could be potentially uncertain. Additionally, the cost of lithium keeps increasing with the prospect of commercialization of Li-ion batteries. Thus, other abundant resources, preferably of low cost, must be investigated as the charge carrier to ensure energy sovereignty, therefore Na-ion batteries become the promising device in this regard. In our laboratory, by using carbon materials as negative electrodes for Na-ion batteries, we have demonstrated the practical satisfactory performance of the Na-ion batteries.[1] The use of electrolyte additives is one of the most effective methodologies to improve the electrode performance. Recently we have reported that the FEC additive facilitates the formation of stable solid electrolyte interphase (SEI) on the surface of electrodes and reduces irreversible capacity.[2] We have also reported, binders, which are used for the preparation of composite electrodes from powder materials, as essential components to improve the electrochemical performance and surface structures of graphite electrodes in Li cells.[3] In this study, the impact of polymer binders and electrolyte components on the hard carbon electrodes in Na cells is examined.The hard carbon electrodes were prepared by mixing different binders, such as poly(vinilydene fluoride) (PVDF), carboxymethyl cellulose (CMC), and sodium polyacrylate (PAANa). As shown in Fig. 1, around 150 mAh g-1 of capacity was lost after 100th cycles in the case of PVDF binder. However, the capacity retention was dramatically improved by using electrodes with CMC and PAANa binders. To obtain information on the chemical components of the SEI layer, hard X-ray photoelectron spectroscopy (HAXPES) spectra of the SEI formed in electrolyte were collected in the synchrotron facility. Fig. 2 shows the HAXPES spectra of hard carbon electrodes before and after the first cycle with PVDF or CMC binder. The peak at 284.5 eV is assigned to C-C bonding originating from hard carbon. In the case of electrode with CMC, C-C peak intensity is relatively lower than that of PVDF. This result indicates that the thicker film is formed on the surface of hard carbon with CMC. The peak of alkyl carbonate exists in the case of PVdF after the first cycle whereas, in the case of CMC, the peaks of alkyl group and Na2CO3appear. The difference suggests that these components of surface film on hard carbon could be related to the improved cycleability. In this presentation, the effect of not only binders but also electrolytes (including solvents, salts, and additives) will be discussed from characterization with powerful surface analysis techniques such as SEM, TOF-SIMS, XPS and HAXPES.