Particle size reduction of battery materials

The particle size and particle size distribution of the active materials significantly define the overall battery performance, like capacity, power density, rate capability, energy density, life cycle stability, and safety. RETSCH sample mills are used for particle size reduction of raw materials like nickel, manganese, cobalt, lithium-containing material or graphite or for the deagglomeration of active electrode materials.

Particle size reduction of silicon

^{Volume-based particle size distribution of the original sample and after 60 min of grinding in the High-Energy Ball Mill Emax and Mixer Mill MM 500 nano.}

Particle size reduction of LPS under controlled atmosphere and temperature

^{Sulphidic solid electrolyte (LPS) together with some balls in a 125 ml Screw-Lock jar of the MM 500 control, opened in a glove box.}

Particle size reduction of graphite through wet grinding

^{Jar filled with a graphite sample for colloidal grinding in the MM 500 nano using isopropanol.}

Synthesis of new battery materials

Mechanochemical synthesis has become particularly popular in the field of battery technology, where it is used to produce innovative electrolytes, separators or multiphase composites of high purity or to optimize their microstructure. For example, synthesizing novel solid electrolytes through a solvent-free process or improving their performance and stability. Another application is in environmentally-friendly recycling reactions such as the mechanochemical reduction of cathode material for lithium-ion batteries. All types of ball mills are suitable for mechanical synthesis. The chemicals involved are typically air-sensitive and expensive, so batch processing in small-cavity jars - as available for RETSCH Mixer Mills - is advantageous.

Process control with GrindControl

Monitoring temperature and pressure is critical in battery material development to ensure optimum conditions for maintaining material integrity. These parameters influence the physical and chemical properties of the materials and directly affect their performance. Accurate control of these conditions is essential to achieve consistent results and enable successful scaling of production processes. Special lids are available to measure temperature and pressure inside the vessel.

RAMAN Spectroscopy with Mixer Mills

Mixer mills are particularly well-suited for in-situ RAMAN spectroscopy, enabling detailed study of mechanochemical reaction kinetics. The MM 400 is equipped with a removable bottom plate which has two openings through which the RAMAN spectrometer points towards the bottom of the transparent PMMA grinding jars. The mill offers processing times of up to 99 hours.

Working under inert atmospheres

The usual process for handling atmosphere-sensitive materials is to fill and open the jars in the glove box. Aeration lids can also be used to control or change the atmosphere in the closed jar. It is also possible to house a complete planetary ball mill in a glove box.

Visit our mechanochemistry page to learn more about mechanochemical applications with RETSCH ball mills.

Sample preparation of batteries for analysis

Typically, the analytical characterization of materials requires only a small quantity, ranging from a few grams to milligrams. Without proper sample preparation, the analysis results will lack significance. To ensure reliable outcomes, the sample must be truly representative, meaning its composition should reflect the complete initial material. This necessitates thorough mechanical homogenization to eliminate inhomogeneities through grinding and mixing prior to sampling. Additionally, it is crucial to avoid introducing any contaminants into the material during sample preparation, as this could falsify the results.

Sample preparation for X-ray techniques

For XRF spectroscopy, samples typically need to be ground to particle sizes <100 µm. Jaw crushers and sample dividers are used for initial crushing, followed by fine grinding in a ball or disc mill. Finally, a pellet is pressed to produce a compacted sample with high element concentration and a smooth surface, ensuring optimum X-ray detectability.

^{Sample of manganese oxide before and after the milling process in the PM 100. For XRF analysis the sample is pressed into a pellet.}

For XRD, a gentler grinding method and even finer particle sizes are required to preserve the sample’s crystal lattice structure. The XRD-McCrone Mill is ideally suited for this purpose.

^{Copper ore sample in its original state (left), pre-crushed in a jar crusher (middle) and prepared with XRD-Mill McCrone for the analysis of molecular structure with X-ray diffraction.}

View our Interactive Topic Poster with short videos on sample preparation for XRF/XRD.

Sample preparation of battery materials with metal components

Material analysis of anodes and cathodes is a fundamental element of quality control and research.  Understanding the composition, structure and properties of these key components is essential for optimizing battery performance, capacity and lifetime.

In a lithium-ion battery, an electrode consists of a coating of active material (metal oxide or carbon-based compound) on a current collector (aluminum or copper). Due to the metal component, the comminution of electrodes is challenging. Similar material mixtures of electrode powder and metal components are found in recycling processes. Large samples can be pulverized using a cutting mill. For fine grinding, ball milling may be an option. However, it must be remembered that ball mills do not crush but tend to flatten metal particles. However, powders containing metal particles can be pulverized to a certain extent, especially when cryogenic grinding is applied.

Sample preparation of polymeric materials

Polymers used in battery components have specific requirements for mechanical and thermal resistance; therefore, analysis of their chemical composition is essential to understand their limitations and to formulate the appropriate composition. Cutting mills are used for initial crushing of macroscopic polymer parts, typically followed by pulverization in a ball mill. In both cases, it may be necessary to embrittle the sample in liquid nitrogen to ensure effective pulverization.

The CryoKit facilitates manual freezing before ball milling. Additionally, RETSCH provides mills equipped with an integrated cooling system, such as the CryoMill and the Mixer Mill MM500 control. These laboratory ball mills are engineered specifically for grinding elastic materials under cryogenic conditions. During this process, the sample is cooled to extremely low temperatures, while the mill actively maintains the grinding jar at a consistent temperature of -196°C, ensuring efficient and effective grinding.

^{Polymer sample prepared with CryoKit}

^{Polymer sample prepared with CryoMill}

^{Polymer sample prepared with MM 500 control}

Laboratory ball mills with active temperature control

Material processing in ball mills often generates high temperatures, exceeding 80°C, which can negatively affect the process when working with temperature-sensitive samples. Cooling or even freezing of sample materials may be required to facilitate size reduction, prevent agglomeration, maintain sample integrity for subsequent analysis or to control mechanochemical reactions. The temperature increase is primarily due to impact and friction effects within the jar and is influenced by the design of the mill and its ability to dissipate heat. RETSCH accounts for these factors by offering ball mills with active temperature control options to maintain low jar temperatures during grinding or to freeze samples for embrittlement.

Emax

The Emax is equipped with an integrated cooling system and offers the functionality to set a maximum temperature, resulting in automatic cooling breaks during operation.

MM 500 control

The MM 500 control continuously cools the jars during operation with thermal fluids like water, glycol or liquid nitrogen. In this way, a minimum temperature of - 100 °C can be achieved, and it is also possible to heat the jars.

CryoMill

The CryoMill features an integrated cooling system which continually cools the grinding jar with liquid nitrogen before and during the grinding process for maximum cooling down to -196°C. 

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