Solid Content Concentration Research Articles

Design of Dispersant in Cathode of Li-Ion Batteries for Cathode Slurry with High Solid Content and High Battery Performance

Generally, cathode of Li-ion batteries was fabricated through the process that cathode slurry composed of active material, conductive agent, binder and N-Methyl-2-pyrrolidone (NMP) as organic solvent was coated on the aluminum foil, dried and pressed. In recent years, decreasing an amount of NMP has been required in terms of low environmental impact and due to cost reduction regarding material, shipping and machining price. However, the decreasing is possible to raise the viscosity of the cathode slurry and cause the defect of manufacturing process such as mixing, carrying and coating. One of the means of the resolving is addition of dispersant to cathode slurry. The dispersant can make an effect to reduce the slurry viscosity with low amount of solvent because it spreads the distance between each particle and also keep the condition of particle distribution. However, the dispersant may have the potential to be the resistance of the battery reaction because the material is polymer. In this study, we have designed dispersants that have the low viscosity of the cathode slurry with low amount of NMP, and hardly block the battery reaction by means of clarifying the function of dispersants and optimizing the component. The cathode slurry was prepared by the following steps: firstly, acetylene black (AB) as conductive agent, polyvinylidene difluoride (PVdF) as binder and dispersants were mixed with NMP. This paste is commonly called ‘AB paste’. Secondly as active material was added to the AB paste and mixed. The weight ratio of each material is as follows, active material:AB:PVdF:dispersant=89.8:8:1.5:0, 0.16, 0.20. Three solid content concentrations were considered as 48, 56 and 62.5 wt.% by adjusting the amount of NMP. Two dispersant materials were considered as a polyvinyl alcohol (PVA) with the role adsorbing to AB, and an acrylate copolymer including amid groups (ACA) with the role adsorbing to not only AB and but also active materials. They were composed of polymers not to be resistant according to previous study. And three samples were evaluated such as PVA only, PVA/ACA mix (weight ratio; PVA:ACA=85:15) and dispersant free. Cathode was prepared through the process coated the slurry on aluminum foil, dried and pressed. The test cells were assembled with the prepared cathode, anode composed of graphite, separator, and electrolyte including LiPF6. The viscosity of cathode slurry was evaluated under 1S-1 shear rate condition by using Dynamic viscoelasticity measuring device (DMA). And the discharge resistance was evaluated under -30℃, 1C as battery performance. Fig.1 shows the results of cathode slurry viscosity with various solid content concentrations. The tendency that the viscosity increases with increasing solid content concentration is observed. Especially at the 62.5 wt.%, the viscosity with added dispersant had much lower than dispersant-free. Furthermore, the effect to decrease the viscosity with PVA/ACA mix was higher than that with PVA only and the viscosity with PVA/ACA mix is less than 10000 mPas-1 as the target with no defect in the mass production process. These results imply the repulsive force with not only AB but also active material is required at 62.5 wt.% due to the distance between each particle is shorter under higher solid content concentration. Fig.2 shows the discharge resistances with various weight ratios of dispersant / AB used by cathode slurry at 62.5 wt.%. The tendency that the discharge resistance with PVA/ACA mix is slightly higher than PVA only is observed. These results imply that ACA with the role adsorbing to active material may affect to the reaction at the surface of active material. However, the resistance with added dispersant at dispersant / AB = 2 php is close to that with dispersant free is appeared. These results may be mainly depended on the effect of dispersant components not to be resistant and less dispersion performance with dispersant free. More detailed and integrated analysis about the dispersant components will be presented and discussed in this work. Figure 1

Shear properties and water connectivity of wet granules at high solid content concentration

The inner liquid distribution in wet granules strongly influences their mechanical properties. In this study, we examined the shear properties (internal friction angle, cohesion, storage modulus and loss modulus) of wet granules composed of graphite particles and water, and determined their inner water connectivity using X-ray refraction contrast imaging computed tomography (CT) to elucidate their correlation. At high solid content concentration (CSC) region (CSC = 85 wt.%), internal friction angle of wet granules was slightly lower than that of wet granules with lower CSC, and their cohesion becomes almost zero. Furthermore, storage modulus of wet granules at CSC = 85 wt.% was the highest among all wet granules. The X-ray CT and scanning electron microscopy (SEM) observations revealed that the water connectivity in the wet granules was in the pendular state and graphite particles fractured under shear test at CSC = 85 wt.%. From these results, it can be concluded that lower shear cohesion at CSC = 85 wt.% is caused by an increase in the number of isolated liquid bridges, and particle fracture results in a decrease in the internal friction angle owing to decreasing roughness of shear plane. Furthermore, the particle fracture also resulted in the higher storage modulus at CSC = 85 wt.% in rheological measurements.

X-ray radiation monitor for measuring solids content in fluid fine tailings.

The extraction of bitumen from oil sands produces fluid fine tailings (FFT) consisting mainly of water, sands, clay, and residual bitumen. Generally, devices with radioactive sources are used to measure the variation of FFT density or solids concentration inline, but to date there is no suitable device for in situ monitoring in tailings storage facilities such as large tailings ponds. In this study, an alternative method using high-resolution spectrometry based on a low radiation intensity source and a cadmium telluride (CdTe) detector was used to measure the solids content in tailings samples based on X-ray attenuation. The radiation source used in the experiment was a 1 μCi 133 Ba. GEANT4, a Monte Carlo-based simulation code that calculates the transmission of radiation through matter, was used to simulate the results of this study and build calibration curves that can determine the solids content concentration based on measured sample composition. Experiments and simulations were performed on various concentrations of both actual FFT samples from tailings facilities and kaolin as a model material. Good agreement between the experimental and simulation results was observed, paving the way for a potential real-time solids content measurement system that could be deployed over large areas to measure the settling of FFT in tailings ponds.

Weathering Stability and Durability of Birch Plywood Modified with Different Molecular Weight Phenol-Formaldehyde Oligomers.

This study investigated the effect of phenol-formaldehyde (PF) resin treatment on the weathering stability and biological durability of birch plywood. Silver birch (Betula pendula) veneers were vacuum-pressure impregnated with four different PF resins with average molecular weights (Mw) of 292 (resin A), 528 (resin B), 703 (resin C), and 884 g/mol (resin D). The aging properties of PF resin modified birch plywood were analyzed using artificial weathering with ultraviolet (UV) light, UV and water spray, and weathering under outdoor conditions. The same combinations of PF-treated plywood specimens were then tested in soil-bed tests to determine their resistance against soft-rot wood decay. It was not possible to compare weathering processes under artificial conditions to processes under outdoor conditions. However, the weathering stability of birch plywood treated with PF resins A, B, and C, scored better than plywood treated with commercial resin D (regardless of solid content concentration [%]). Results from unsterile soil bed tests showed improvements in resistance to soft-rot wood decay compared to untreated plywood and solid wood. Mass loss [%] was lowest for birch plywood specimens treated with resin of highest solid content concentration (resin D, 20%). Provisional durability ratings delivered durability class (DC) ratings of 2–3, considerably improved over untreated solid wood and untreated birch plywood (DC 5).

Kinetics of Polymer-Fullerene Phase Separation during Solvent Annealing Studied by Table-Top X-ray Scattering.

Solvent annealing is an efficient way of phase separation in polymer-fullerene blends to optimize bulk heterojunction morphology of active layer in polymer solar cells. To track the process in real time across all relevant stages of solvent evaporation, laboratory-based in situ small- and wide-angle X-ray scattering measurements were applied simultaneously to a model P3HT:PCBM blend dissolved in dichlorobenzene. The PCBM molecule agglomeration starts at ∼7 wt % concentration of solid content of the blend in solvent. Although PCBM agglomeration is slowed-down at ∼10 wt % of solid content, the rate constant of phase separation is not changed, suggesting agglomeration and reordering of P3HT molecular chains. Having the longest duration, this stage most affects BHJ morphology. Phase separation is accelerated rapidly at concentration of ∼25 wt %, having the same rate constant as the growth of P3HT crystals. P3HT crystallization is driving force for phase separation at final stages before a complete solvent evaporation, having no visible temporal overlap with PCBM agglomeration. For the first time, such a study was done in laboratory demonstrating potential of the latest generation table-top high-brilliance X-ray source as a viable alternative before more sophisticated X-ray scattering experiments at synchrotron facilities are performed.

Hydrophilic nano-silica coating agents with platinum and diamond nanoparticles for denture base materials

Preventing microorganisms from adhering to the denture surface is important for ensuring the systemic health of elderly denture wearers. Silica coating agents provide high hydrophilicity but lack durability. This study investigated solutions to improve the durability of the coating layer, determine an appropriate solid content concentration of SiO2 in the silica coating agent, and evaluate the effect of adding platinum (Pt) and diamond nanoparticles (ND) to the agent. Five coating agents were prepared with different SiO2 concentrations with/without Pt and ND additives. The contact angle was measured, and the brush-wear test was performed. Scanning electron microscopy was used to investigate the silica coating layer. The appropriate concentration of SiO2 was found to be 0.5-0.75 wt%. The coating agents with additives showed significantly high hydrophilicity immediately after coating and after the brush-wear test. The coating agents with/without additives formed a durable coating layer even after the brush-wear test.

Development of High Performance Electrode of Lithium Ion Battery By High Speed Manufacturing Using Continuous Kneading Process

The authors have developed the continuous kneading process for lithium ion battery (LIB) slurry to prepare for future mass production and cost reduction. It is very important operation in a battery manufacturing process to disperse electrode materials because battery performance is decided by the dispersion states of electrode materials. A batch operation is generally used as a conventional method, and it needs long operation time to make dispersion slurry. Getting dispersion slurry using some of the next generation active materials having modified-surface and fine grain size is difficult for the conventional method. To provide a dispersing device capable of efficiently obtaining dispersion force is required. We use twin screw type continuous kneading machine. This continuous kneader can disperse a wide range of viscosity. The continuous kneader is also applied in various industries such as food and chemical in order to have excellent dispersing ability. Due to continuous process, automation and cost reduction become possible, and production speed is improved. The continuous kneader is closed horizontal twin screw type. The twin screws are constructed of many paddles which are mounted on the twin shafts. Each paddle is separate piece that can be arranged to suit various mixing characteristics. The shafts rotate in the same direction. The paddles are arranged in pairs along the mixing circuit, and have a constant clearance between the tip of the paddle and the inner barrel wall, as well as the tip of the paddle to the surface of the opposite piece. This gives the benefit of mixing efficiency. Volume of material is changed in compression and expansion according to paddle's rotation. Shearing actions between the barrel and paddle, and between paddles increases efficiency of kneading and dispersion. The continuous kneader was applied to the tape for manufacturing magnetic recording medium, because dispersion plays important role. The magnetic powder became finer according to enhance data capacity, the continuous kneader could manufacture good dispersion magnetic coating material in response to this change. Manufacturing of lithium ion battery electrode slurry is kneading powder materials in binder resin in the similar way of making the magnetic tape. The authors included the know-how obtained by improving manufacturing of the magnetic tape in continuous kneading process of lithium ion battery electrode slurry. The authors have performed examination of suitable kneading conditions of dispersion slurry production by using Li(Ni1/3Mn1/3Co1/3)O2 (NMC) and LiFePO4(LFP) as cathode active materials. The dispersion state of the slurry using the continuous kneader is controlled by the paddle arrangement, the rotary speed of the shaft and the supply conditions of raw materials. Several elements of kneading conditions have beneficial effect on slurry viscosity and battery performance. After changing some of kneading conditions, excellent dispersion slurries were obtained. The slurry from optimized continuous process showed high battery performance. Cyclic performance of laminated pouch type cell showed a stable characteristic about 2,000 cycles at the charge-discharge rate of 3C. The battery performance was comparison with the slurry made by using batch operation. Rate characteristics and cyclic performance of the slurry made by continuous kneading process showed better than made by batch operation. The paddle arrangement and the supply conditions of raw materials influence the dispersion state of slurry. The solid content concentration in the continuous kneader changes when supply conditions of raw materials was changes, it was considered that the dispersion of raw materials advanced by adjusting the solid content concentration appropriately. This high speed continuous kneading process greatly improves not only the battery performance but also productivity of the electrode slurry. Our high speed continuous kneading process can manufacture about 60 times faster than the conventional batch operation according to our estimates. Therefore the cost reduction may be practiced in LIB mass production. The above-mentioned results indicate that the high speed process of high performance electrode slurry made by the continuous kneader is effective method. Figure 1

Characterization of well‐defined poly(ethylene glycol) hydrogels prepared by thiol‐ene chemistry

AbstractConsidering the large number of applications for hydrogels, a better understanding of the relation between molecular structure and mechanical properties for well‐defined hydrogel is essential. A new library has been compiled of poly(ethylene glycol) polymers (PEG) of different length end functionalized with diallyl, dithiol, and dimethacrylate, and crosslinked with complementary trifunctional crosslinkers. In this study, the hydrogels were initially analyzed by FT‐Raman and NMR to study the conversion ratio of the functional groups. The effects of solvent type, solid content concentration, curing time and length of the PEG chains on the final leaching, swelling and tensile properties of the hydrogels were studied. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Rootstock and Cultural Conditions Affect Sweet Cherry Fruits Composition

The demand for sweet cherries (Prunus avium L.) fresh fruits consumption in Romania has been increasing gradually over the last few years, suggesting that production should be more expanded. More and more private investors established their modern cherry orchards to meet market demands. In order to find the most suitable combination between cultivar, rootstock and agroecological conditions which respond with high productivity and better fruits quality, a study has been started in different areas and take into consideration a large number of varieties and rootstocks combinations. The trial was carried out as follows: in north of the Bucharest in the experimental field of UASVMB, at the Istrita Fruit Nursery Station, Buzau and at Moara Domneasca Didactic Farm, Ilfov. The studied sweet cherry varieties were ‚’Kordia’, ’Ferrovia’, ’Firm Red’, ’Giant Red’, ’Early Red’, ’Van’, ’Stella’ and ’Skeena’. The rootstocks used for these cultivars were PHLC, CAB6P, CAB11E, Colt and P. mahaleb. Biochemical analyses have been done in the UASVMB laboratory. For the scion– rootstock combination, soluble solids content concentration was determinate using a digital refractometer, titratable acidity by tritimetry with KOH 0,1N, ascorbic acid by extraction in oxalic acid 1% and HPLC dosage and anthocyanins content by spectrophotometric determination after an HCL 1% methanol extraction. The biggest fruits were collected from GiantRed/CAB6P trees (9 g/fruit at Istrita Station) which also registered a higher value of soluble solids content (15 % at Istrita and 16% in Bucharest) than other combinations. Toghether with FirmRed/CAB6P and FirmRed/CAB11E, the same GiantRed/CAB6P accumulated more ascorbic acid in fruits. The acidity was much lower at Kordia/PHLC (0,44% malic acid) at Istrita and higher at Van/mahaleb (0,87%) which also recorded the highest value of anthocyans (7,81 mg/100g) in the second half of june at Moara Domneasca Didactic Farm. GiantRed/CAB6P had only 1,52 mg/100g anthocyans in fruits but proves to be a very tasty and attractive sweet cherry variety for fresh consumption. Because the performance of all these tested combinations has not been described yet in the Romanian growing conditions, the data presented need to be confirmed by further researches on several years.