6 minute read
Empowering Battery Research and Production with Advanced Analytical Solutions
Source: ATA Scientific Pty Ltd
Lithium-ion (Li-ion) batteries are predicted to play a key role in the trend toward renewable and sustainable industrial electrification solutions. As fossil fuels are phased out and CO2 regulations become more stringent, the increase in demand to provide ever more lightweight, low-cost, safe, high-power and fastcharging batteries has accelerated advances in battery technology. Access to the right tools and technologies can help optimise R&D and production cycles, investigate causes of battery failure, improve safety, and speed up time-to-market, to keep technological progress moving in sync with modern global demands. Here we discuss a complementary set of physical, chemical, and structural analysis solutions designed to enable rapid, high-precision analysis of particle size and shape distribution plus elemental composition of battery materials for the entire process from research through to production.
Measuring Particle Size – Why is it Important?
The performance of a battery can be characterised according to the amount of energy that it can store or the amount of power that it can produce. The maximum battery power can be increased by decreasing the particle size of the electrode material and increasing the surface area. Battery power is determined by the rate of reaction between the electrodes and the electrolyte, while storage capacity is a function of the volume of electrolyte within the cell. These properties are intrinsically linked to the intercalation structure and particle size of the electrode particles, which determine how well the mobile ions are taken up and released by the electrode. Particle size distribution and particle shape influence particle packing, hence the volume of electrolyte that can be accommodated within the interstitial voids of the electrode, which affects storage capacity. As a result, a mixture of coarse and fine particles is often used in the electrodes to increase surface area, whilst also controlling the overall packing fraction of the electrode material to allow good contact between the electrode and the electrolyte. Particle sizing of electrode materials is commonly performed using the Mastersizer 3000 which uses automated laser diffraction technology. With a measurement range that runs from 0.01 to 3500 µm, the Mastersizer is the particle sizing technology of choice for most battery manufacturing applications – starting from precursor to the final milled electrode materials. The Malvern Insitec online process systems deliver real-time monitoring of particle size for automated process control. These can be used for either the monitoring of particle size evolution in precursor slurry or in the control of electrode material size right after the mill. Smaller particles in electrode slurry production can be prone to agglomeration and/or flocculation, resulting in uneven electrode coatings and ultimately compromising the electrochemical performance. Aggregation and stability can be monitored by measuring zeta potential (particle charge) using the Malvern Zetasizer Ultra. A low zeta potential will indicate particles likely to aggregate whereas a high zeta potential will form a stable dispersion. The Malvern Zetasizer Ultra builds on the legacy of the industry-leading Zetasizer Nano Series adding high-resolution sizing (Multi-Angle Dynamic Light Scattering) and particle concentration capabilities.
Measuring Porosity - Why is it Important?
Porosity is an important parameter both for the separator and for the electrolyte to transport lithium-ions between the anode and cathode. By controlling porosity, higher intra-electrode conductivity can be achieved to ensure adequate electron exchange as well as sufficient void space for electrolyte access/transport of lithium-ions for intercalation of the cathode. Higher porosity means less heat generated in the cell and greater
Figure 1 shows a typical manufacturing process for Li-ion batteries. The anode and cathode active materials are processed into a slurry before coating, calendaring, and drying. Uniform dispersion of the solid content (active materials) with minimal agglomeration is critical for a highquality final product.
Figure 2 Particle size distribution of three batches of NCM cathode materials made with different processing parameters Figure 3 Particle size distribution of three batches of synthetic graphite made with different heating conditions
energy density. However, excessive porosity hinders the ability of the pores to close, which is vital to allow the separator to shut down an overheating battery. The Micromeritics AutoPore V Series utilises Mercury Porosimetry, a technique based on the intrusion of mercury into a porous structure under controlled pressures, to calculate pore size distributions, total pore volume, total pore surface area, median pore diameter and sample densities.
Measuring Surface Area - Why is it important?
Increasing the surface area of the electrode improves the efficiency of the electrochemical reaction and facilitates the ion exchange between electrode and electrolyte. Lower surface area materials are better suited for improved cycling performance of the cell resulting in longer battery life. High surface area presents some limitations due to the degradation interaction of the electrolyte at the surface and resultant capacity loss along with thermal stability. Nanoparticles hold promise to increase surface area without capacity loss by permitting shorter diffusion paths for lithium-ions between the graphite particles which facilitates fast charge and more efficient discharge rates and improves the capacity of the battery. The Micromeritics TriStar II Plus is an automated, three-station, surface area and porosity analyser. MicroActive software allows the user to overlay a mercury porosimetry pore size distribution with a pore size distribution calculated from gas adsorption isotherms to rapidly view micropore, mesopore, and macropore distributions in one easy-to-use application.
Quantifying Particle Shape - Why is it Important?
Shape will affect the electrode coating in terms of packing density, porosity and uniformity. Spherical shaped particles will pack more densely than fibrous or flake shaped particles. The average strain energy density stored in a particle increases with the increasing sphericality. Fibrous and flake shaped particles are expected to have a lower tendency for mechanical degradation than spherical-shaped particles. Automated imaging using the Malvern Morphologi 4 is commonly employed for particle shape analysis of electrode materials but can also be coupled with Raman spectroscopy to give particlespecific structural and chemical information.
Deviations in chemical composition or impurities in electrode materials can significantly affect final battery performance. For this reason, chemical composition and elemental impurity analysis are an integral part of the battery manufacturing process. Simple to operate and fast to learn, the Phenom XL G2 scanning electron microscope (SEM) is an unrivalled technique that allows users to observe the 3D structure of electrodes after production; the size and granulometry of raw powders; the size of pores and fibres in insulating membranes and the response of materials to electrical or thermal solicitations. Using fully integrated X-Ray analysis (Energy Dispersive Spectrometer, EDS) the distribution and identity of elements including the presence of contaminants in the battery sublayer can quickly be revealed.
The Phenom XL G2 is the only SEM that can be placed within an argon-filled glovebox, allowing users to perform research on air sensitive lithium battery samples.
Whether you are a battery component manufacturer looking for greater process efficiency and better quality control, or a researcher striving to determine the performance parameters of newly emerging battery materials, our solutions will offer you the new levels of insight and control needed to power the production of superior quality batteries.
Contact us for a demonstration or quote today! ATA Scientific Pty Ltd +61 2 9541 3500 enquiries@atascientific.com.au www.atascientific.com.au
