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Battery Technology

The role of laboratory mills in battery research, production, quality control and recycling

From initial research through to manufacturing, quality assurance, and recycling processes, RETSCH laboratory mills are crucial at every stage of the battery production value chain. Ball mills are instrumental in battery research and development, playing a significant role in the innovation of new battery material systems.

Giga factories, recycling facilities, and testing laboratories rely on RETSCH mills for homogenizing battery components and battery materials, preparing them for comprehensive quality analysis. RETSCH provides a range of solutions comprising initial crushing, fine grinding, sample division, and particle size analysis through sieving.

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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.

Mixing and coating of battery materials

Battery production involves a wide range of mixing and coating processes. A variety of equipment, such as stirrers and vortex mixers, is typically employed for mixing; ball mills can also be suitable, particularly in research settings. The continuous movement of sample material in a ball mill, regardless of the energy input level or the presence of balls, leads to excellent mixing and coating results.

Process flow chart showing individual steps of electrode manufacturing including mixing and coating applications.

Mixing

Ball mills are suitable for both wet mixing of slurries and dry mixing of bulk materials. An example of a dry mixing process is the production of active cathode materials, necessitating the precise stoichiometric blending of dry ingredients. Wet mixing processes, such as electrode slurry production, involve investigation of factors like material composition, mixing intensities, temperature variations, viscosity changes, and the sequence of adding chemicals to the slurry.

RETSCH mixer mills offer full control over parameters like energy input, time, and temperature. Additionally, they provide a selection of jar materials and sizes, the ability to operate under inert conditions, and the capability to handle multiple samples simultaneously.

Coating

The ball mill coating process relies on two fundamental principles: achieving a homogeneous mixture of two materials and mechanically coating particles. This is accomplished by generating impact effects that facilitate adhesion of the coating material to the particle surface.

Both wet and dry coating methods are employed to improve the performance of battery electrodes. For instance, in lithium-ion batteries, silicon particles might receive a polymer coating to boost cycling stability, or LNMO particles could be enveloped in a ceramic layer to increase the charging rate. In the case of zinc-air batteries, anode particles are coated with beryllium glass to improve rechargeability.

RETSCH ball mills stand out from other coating technologies by providing a straightforward, cost-efficient, and easily scalable solution.

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.

Battery recycling on a lab scale

1. Shredding

In recycling, shredding complete or disassembled batteries is one of the first steps. In research processes to develop new recycling routes, small-scale shredding is performed using RETSCH Cutting Mills.

Cylindrical cells

Pouch cells

Lightweight or heavy fraction

2. Fractionation with sieving machines

Sieving machines like RETSCH's AS 200 series are suitable for the separation of different material fractions,  for example black mass, polymeric and metallic parts.

3. Sample preparation of recycling fractions

In both research projects and established large-scale recycling operations, analyzing the chemical composition of recycled material fractions is essential. Due to the inhomogeneous nature of these materials, they require mechanical processing and pulverization into fine powders for accurate analysis. Specifically, polymer fractions must be ground to facilitate microwave digestion and ICP-MS analysis, enabling the quantification of residual metals like lithium, cobalt, nickel, and manganese. Moreover, the market value of the black fraction is influenced by its concentration of valuable metals, such as lithium and cobalt. To ensure reliable sample preparation, RETSCH offers a comprehensive selection of mills suited for both pre-crushing and fine grinding tasks.

Housing parts
SM300

60 mm / <4 mm

Polymeric foil
CryoMill
10 mm / <800 µm

Metal foil
MM 500 control
15 mm / <800 µm

Black mass
MM 400
2 mm / <300 µm

Various material fractions of a recycling process, before and after homogenization for subsequent analysis to determine purity and market value.

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

X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD) are widely used analysis techniques in battery technology, employed across the entire battery life cycle - from minerals to active battery materials and degradation products. These methods are pivotal for assessing the chemical composition and structural characteristics of materials, including the identification and quantification of various elements and compounds such as
  • nickel content in laterite ores
  • impurities such as iron in silicon raw material
  • the degree of graphitization
  • precious metal residues in the recycled polymer fraction
RETSCH offers a perfectly aligned product portfolio to prepare samples for XRF spectroscopy and XRD. 

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.

Retsch products for sample preparation for XRF analysis

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

Selection of the most suitable mill

RETSCH laboratory mills are an excellent choice for battery research applications and for mechanical sample preparation prior to analysis. The comprehensive portfolio, including jaw crushers, rotor mills, cutting mills, knife mills, ball mills, mortar grinders and auxiliary devices, offers exceptional versatility and ease of use.

RETSCH ball mills, for example, are designed to meet research requirements. They are operable within a glove box and allow for handling controlled atmospheres, with aeration lids and a safety closure device to ensure secure transportation of the grinding jars. To manage thermal conditions during the milling process, some models offer temperature control. The ball mills accommodate a variety of jar sizes and materials.

RETSCH offers comprehensive advice on selecting the best equipment for a specific application. To facilitate the selection process the features and strengths of each ball mill model are visualized in a graph. In the below examples, it is easy to see that the Planetary Ball Mill PM 300 offers advantages in terms of power, final fineness and maximum jar volume compared to the Mixer Mill MM 500 control, which in turn offers easier handling, versatility and the ability to control the temperature during the process.

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. 

VERDER SCIENTIFIC Solutions

True to our guiding principle ENABLING PROGRESS, Verder Scientific can assist you in the development, production and recycling of batteries. Under our umbrella we combine the know-how of five renowned developers and manufacturers of scientific equipment:
CARBOLITE GERO, ELTRA, QATM, RETSCH and MICROTRAC are among the leading specialists in their respective fields of activity which are Heat Treatment, Elemental Analysis, Materialography & Hardness Testing, Milling & Sieving and Particle Characterization.

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Battery Technology - Часто задаваемые вопросы

What is the role of RETSCH laboratory mills in battery research and production?

RETSCH laboratory mills are crucial at every stage of the battery production value chain, from initial research through to manufacturing, quality assurance, and recycling processes. Especially ball mills play a significant role in the innovation of new battery material systems.

Are RETSCH mills suitable for grinding battery materials?

Yes, RETSCH mills are highly suitable for grinding battery materials, especially given the advanced options they offer for working under inert atmospheres, temperature control and cryogenic conditions. They are used for particle size reduction in mechanical synthesis, mixing processes and sample preparation. RETSCH's comprehensive range of mills is also employed in battery recycling through small-scale shredding or sample preparation for analysis. These capabilities make RETSCH mills highly adaptable and effective for the specific requirements of battery material processing.

How are RETSCH mills employed in battery recycling on a lab scale?

For battery recycling, RETSCH offers solutions that include shredding complete or disassembled batteries, fractionation with sieving machines, and sample preparation of recycling fractions for chemical analysis.

How do RETSCH laboratory mills contribute to battery research and materials science?

RETSCH offers laboratory mills and sieving machines designed for the development, analysis, and recycling of battery materials. Our equipment facilitates mechanochemical synthesis, precise particle size reduction, and effective mixing and coating processes. Features like inert atmosphere capability, temperature control options, and process monitoring with GrindControl cater to the specific needs of battery technology research. Additionally, RETSCH provides expert consultation and access to application laboratories, helping researchers select the right tools for their studies.