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The multi-interactions between nanoparticles and micro-particles, as well as polymers are responsible for complex rheological behavior in electrode slurry, which has crucially influenced the quality and lifetime of lithium-ion batteries. To clarify the shear- and time-dependent rheological behavior of the multi-component slurry, the effect of various components on the yield stress, viscosity, and thixotropic time scales has been investigated by steady-state and transient step experiments. The results demonstrate that the amounts of added carbon black, polymeric binders, and active material play a significant role in the rheological properties. In the steady-state tests, the viscosity of the slurry increases with the increase of the carbon black, polymer, and active material content. However, the yield stress of the slurry only distinctly increases when the carbon black and polymer are increased, while it is virtually unaffected by large particles of the active material. In the transient tests, the destroyed timescale rises and the recovery timescale reduces as the carbon black, polymer, and active material content are increased. The quantitative relationship between various components and rheological behaviors will be useful for the preparation and coating process of slurry. [ABSTRACT FROM AUTHOR]

The electrolyte filling process of battery cells is one of the time-critical bottlenecks in cell production. Wetting is of particular importance here, since only completely wetted electrode sections are working. In order to accelerate and facilitate this process, the authors of this study developed a method to significantly increase the wettability of graphite-based anodes by a laser surface modification using low energy nanosecond laser pulses. The anode surface microstructure was evaluated by means of white-light interferometry and scanning electron microscopy. The assessment of wettability was done by drop test and capillary rise test of the liquid electrolyte. The results show that there is a predominantly selective ablation process for laser energy inputs below 2 J/m by which the graphite active material remains unaffected and the binder material is decomposed. The observed increase in surface roughness correlates with the increasing wettability. Investigations using Raman spectroscopy showed that laser treatment leads to a damage on the crystalline structure of the graphite particle surface. However, treating an entire anode including 6 wt% binder and conductive carbon black has shown that the overall amorphous content of the anodes surface can be reduced by 32% through treating the surface with a laser energy of 1.29 J/m. Up to that point, which is the resulting parameter range for the selective process, it is possible to ablate the amorphous binder and carbon black phase coevally exposing graphite particles while keeping their crystalline structure. Exceeding that range, ablation of the whole anode composite dominates and amorphization of the graphite surface occurs. The electrode's capacity was tested on half-cells in coin cell format. For the whole laser parameter range investigated, the anodes capacity matches the mass loss caused by laser ablation. No additional capacity loss was observed due to amorphization of the exterior graphite particle's surface. [ABSTRACT FROM AUTHOR]

In this study, within the defined orthogonal array of Taguchi design, the hydrothermal process parameters have been optimized for fabricating the smallest particle sized iron oxide (Fe2O3) particles. The finest particle size (210 nm) has been achieved when 0.02 M FeCl3 solution at pH 10 is hydrothermally treated for 90 min with an autoclave filling ratio of 100% (D3). Afterwards, to improve the physical properties of iron oxide particles, carbon black powder is added into the precursor solution as the seeding agent before the hydrothermal treatment. Structural and morphological analyses show that upon the existence of carbon in the precursor solution, C-supported Fe2O3 (D5) is fabricated. In the latter, carbon is present in graphitic form and no carbide formation is detected. Electrochemical test results verify that unlike to Fe2O3 (D3), C-supported Fe2O3 (D5) electrode performs lower charge transfer resistance and polarization leading to higher first coulombic efficiency, capacity retention, and improved rate performance, eventually. Thanks to the favorable characteristics of the latter, after 150 cycles, D5 performs 550, 390, and 333 mAh g−1 discharge capacities under loads of 50 mA g−1, 500 mA g−1, and 1.5 A g−1, respectively. Finally, to understand the contribution of capacitive and diffusion-controlled reactions to the total stored charge, an adopted sweep rate method has been used. The calculated voltammograms reveal that fabricating C-supported Fe2O3 particles led to improved rate performance because faradaic reactions that occur at the surface of the material prevail. [ABSTRACT FROM AUTHOR]

Locust Bean Gum (LBG, carob bean gum) was investigated as an environmentally friendly, natural, and water-soluble binder for cathode (LFP) and anode (LTO) in lithium-ion batteries (Li-ion). For the first time, we show LBG as an electrode binder and compare to those of the most popular aqueous (CMC) and conventional (PVDF) binders. The electrodes were characterized using TGA/DSC, the galvanostatic charge–discharge cycle test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Thermal decomposition of LBG is seen to begin above 250 °C with a weight loss of about 60 wt% observed at 300 °C, which is sufficient to ensure stable performance of the electrode in a Li-ion battery. For CMC, weight loss at the same temperature is about 45%. Scanning electron microscopy (SEM) shows that the LFP–LBG system has a similar distribution of conductive carbon black particles to PVDF electrodes. The LTO–LBG electrode has a homogeneous dispersion of the electrode elements and maintains the electrical integrity of the network even after cycling, which leads to fast electron migration between LTO and carbon black particles, as well as ion conductivity between LTO active material and electrolyte, better than in systems with CMC and PVDF. The exchange current density, obtained from impedance spectroscopy fell within a broad range between 10−4 and 10−2 mA cm−2 for the LTO|Li and LFP|Li systems, respectively. The results presented in this paper indicate that LBG is a new promising material to serve as a binder. [ABSTRACT FROM AUTHOR]

The positive electrode of a Li-ion battery is made from active material, a binder and conductive material. In this work, the direct and interaction effects of these components on electrochemical performance of a Li-ion cell is studied using design of experiments. For this purpose, a two-level full factorial design was used and interactions were analyzed using analysis of variance. The content of carbon black and graphite as conductive materials and polyvinylidene difluoride as binder are considered as input parameters. Theactive material is NCM622 in the current work. Initial discharge capacity and Warburg coefficient obtained from impedance spectroscopy are output responses. Eleven experiments along with the central points were conducted to determine the relationship between process parameters and the output responses. This information is needed to optimize the output. It was observed that all three parameters are significant. In low carbon black and graphite content, the binder has a negative effect on both parameters, but in high levels of carbon black content it has a positive effect due to the better connectivity of carbon particles with each other. The results show that interaction of carbon black-binder and carbon black-graphite are also significant. Mathematical models were presented in order to optimize the parameters. [ABSTRACT FROM AUTHOR]

An all-solid-state battery (ASSB) with a new structure based on glass-ceramic that forms Na2FeP2O7 (NFP) crystals, which functions as an active cathode material, is fabricated by integrating it with a β″-alumina solid electrolyte. Two important factors that influence the rate capability of this ASSB were optimised. First, the particle size of the precursor glass powder from which the NFP crystals are formed was decreased. Consequently, the onset temperature of crystallisation shifts to a lower temperature, which enables the softening of NFP crystals and their integration with β″-alumina at a low temperature, without the interdiffusion of different crystal phases or atoms. Second, the interface between the β″-alumina solid electrolyte and cathode active materials which consisted of the NFP-crystallised glass and acetylene black used as a conductive additive, is increased to increase the insertion/release of ions and electrons from the active material during charge/discharge processes. Thus, the internal resistance of the battery is reduced considerably to 120 Ω. Thus, an ASSB capable of rapid charge/discharge that can operate not only at room temperature (30 °C) but also at −20 °C is obtained. This technology is an innovative breakthrough in oxide-based ASSBs, considering that the internal resistance of liquid electrolyte-based Li-ion batteries and sulphide-based ASSBs is ~10 Ω. [ABSTRACT FROM AUTHOR]

A simple method was applied to control the morphology of LiMn2O4 and Li1.05Mn1.97Nb0.03O4 in the sintering process by premixing a suitable proportion of acetylene black in the raw material. Both specific discharge capacity and cycling stability of the samples were improved. The results demonstrated that the doped samples showed excellent electrochemical performance at both 25 °C and 55 °C. [ABSTRACT FROM AUTHOR]

Sedimentation of opaque suspensions of carbon black and lithium-iron-phosphate was investigated by spin-echo-based magnetic resonance imaging. Optical methods are usually applied to determine settling velocities, but are limited with respect to high concentrations and optical transparency. The presented method uses intensity data from the noninvasively measured magnetic resonance signal of the sample. The settling velocity is obtained from the evolution of the signal intensity profiles based on the contrast in 1H magnetic resonance imaging between particles and liquid. New insights into the sedimentation in opaque suspensions are provided, since the 1H images uncover the spatial distribution of the particles and its agglomerates, as well as the shape of the settling front. Additionally, the sedimentation was experimentally studied using a sedimentation balance, which gravimetrically measures the increase in mass fraction over time due to the settling of particles. By parallel usage of these two methods, the sedimentation processes of opaque suspensions of lithium-ion-battery electrode materials were investigated. The sedimentation balance covers high, technically relevant concentrations. Limiting factors of the methods are discussed, which are mainly signal intensity in the magnetic resonance imaging and the increasing viscosity of highly concentrated suspensions. [ABSTRACT FROM AUTHOR]

Novel MoS/acetylene black (AB) composite was developed using a single-step hydrothermal method. A systematic characterization revealed a few-layered, ultrathin MoS grown on the surface of AB. The inclusion of AB was found to increase the capacity of the composite and achieve discharging capacity of 1813 mAhg. [ABSTRACT FROM AUTHOR]