Lithium-ion battery manufacturing
In our everyday life, we need energy to cover our increasing demand for communication and mobility. At the same time, this energy needs to be produced and stored in sustainable ways to save the precious resources of our ecosystem.
Lithium-ion batteries (LIBs) are widely used in portable electronics, electric vehicles, and grid storage due to their high energy density and long cycle life. Many innovative materials have been adopted and commercialized to increase battery performance.
Battery process technology, on the other hand, bears great potential for improvement to realize the full potential of available chemistry. Twin-screw extrusion can help optimize the manufacturing processes of batteries to make them safer, more powerful, longer lasting, and more cost-effective. Rheological characterization of battery slurries is necessary to ensure an efficient screen-printing process and to develop new formulations.
Lithium-ion battery slurry
During the multi-step process from raw materials to the final battery cell, the use of a twin-screw extruder can improve the critical step of electrode material production (aka battery slurries).
Battery slurry production is commonly realized by batchwise mixing of active materials, carbon black, solvents, binders, and additives in stirred vessels. This process is labor-intensive, bears the risk of batch-to-batch variations, and requires production downtimes for cleaning.
Twin-screw compounding offers a continuous production process with precisely controlled material shear, heat transfer, material throughput, and residence time. The twin-screw extrusion process provides high reproducibility, less cleaning time, and high material and labor efficiency.
The excellent dispersive and distributive mixing capabilities of a twin-screw extruder enable much more homogeneous cathode pastes as compared to alternative batch mixing in, for example, a dissolver. In return, this can lead to improved material properties.
Cathode slurry mixed using a dissolver
© Pictures are courtesy of University of Braunschweig, IPAT, Mr. Mattis Batzer
Learn more about applications in which twin-screw extrusion can help improve the classic production of cathode and anode slurries by moving from a batch that is challenging to scale up to a well-controlled continuous process. A reduction of solvent from the process can save up to 30% of the total energy consumption; here, extruders can help produce almost-dry battery pastes. Ways to overcome the risk of shorting and fire caused by flammable organic electrolyte novel battery types are being investigated. Extruders provide excellent capabilities for solid state battery (SSB) development. An understanding of the rheological properties of an electrode slurry is necessary for a precise printing process to obtain batteries with a high capacity and a high number of charging cycles.
Continuous production of battery slurries
Cathode and anode slurry compounding
- Battery slurries are generally mixed batchwise in planetary mixers.
- The mixing is labor-intensive, has low material efficiency, and bears the risk of batch-to-batch variations.
- Continuous slurry compounding reduces material loss, cleaning time, handling errors, and product variations.
- Twin-screw extruders continuously compound slurries with high reproducibility.
- Control composition, material shear, and temperatures.
Learn more, read the application note: Continuous twin-screw compounding of battery slurries in a confined space
Solvent-free cathode and anode slurries
- Electrodes are generally coated by solvent-casting methods.
- Requires energy consumptive solvent evaporation and recycling techniques.
- Volatile solvents are hazardous and expensive.
- PTFE actis as a binder in solvent-free electrode slurries.
- Compounding of PFTE and active material powders requires high shear.
- Twin-screw extruders successfully compound PTFE and active material to produce solvent-free slurries.
- High shear renders formation of PFTE fibrils binding active material grains.
Learn more, read the application note: Cost-efficient and ecological twin-screw compounding of dry lithium-ion battery pastes
Solid-state lithium batteries
- Pure lithium-metal anode possesses the highest theoretical capacity.
- But, in conventional liquid electrolytes, dendrite growth and instability of lithium metal cause poor cyclability and safety of battery.
- Solid polymer electolytes (SPE's) exhibit a physical barrier against dendrite growth.
- SPE enables safe application of pure lithium-metal anodes in solid-state batteries (SSB).
- Thermo Scientific HAAKE MiniLab Twin-Screw Extruders successfully used for solvent free preparation of a new thermoplastic polymer electrolyte with excellent dispersion.
Learn more by reading the following publications:
R. F. Samsinger, et al. "Influence of the Processing on the Ionic Conductivity of Solid-State Hybrid Electrolytes Based on Glass-Ceramic Particles Dispersed in PEO with LiTFSI"Journal of The Electrochemical Society, Volume 167, Number 12 Citation R. F. Samsinger et al 2020 J. Electrochem. Soc. 167 120538
Francisco González, et al. "High Performance Polymer/Ionic Liquid Thermoplastic Solid Electrolyte Prepared by Solvent Free Processing for Solid State Lithium Metal Batteries"Membranes (Basel). 2018 Sep; 8(3): 55.
Rheology for lithium-ion battery manufacturing
- Understanding the rheological properties of an electrode slurry is necessary to:
- Optimize the coating process
- Define the storage handling
- Characterize the quality of dispersion as a predictor for cell performance.
- Characteristic flow curves (the slurry viscosity over shear rate) provide insight of the slurries' flow behavior in processes like pumping, stirring, and coating.
- Thermo Scientific HAAKE iQ Air Rotational Rheometers are used to measure flow curves over a broad range of shear rates with high precision.
Cathode slurry compounding in a confined space
In this video, the extruder was operated without intervention protection. This is for demonstration purposes only and must not be used in this way.
Battery manufacturing instruments from Thermo Fisher Scientific
During Process Development, versatility and easy handling are paramount. Moisture-sensitive materials, together with solvent vapors hazardous to health, often require electrode production to be carried out under inert atmosphere. Therefore, it is important to be able to operate all instrumentation in a containment area, such as a glove box, without compromising the equipment’s full benefits.
We provide lab- and pilot-scale extrusion equipment that is used globally by numerous academic and industrial market leaders in the area of battery development. Our solutions offer:
- Small footprint — The Thermo Scientific Process 11 Twin-Screw Compounder represents all functionalities of a production extruder scaled down to a lab-sized unit to fit into confined spaces in safety workbenches and glove boxes.
- Robustness — All electronics are fitted into the compact unit and show best performance when operated under inert atmosphere.
- Split and removable barrel design — Easy to open and close, even within tight spaces. Thorough cleaning with no dead spaces. Easy exchange of all contact parts to prevent cross-contamination when performing different application on the same instrument.
- Segmented screw design — Easy customization of mixing behavior for specific application needs.
- Versatility — Wide range of accessories to accommodate a wide variety of applications: granulation setup, film die and take-off, face-cut pelletizer for dry slurries, different die designs for slurry process.