Despite its impressive growth in recent years, the EV lithium-ion battery (LIB) industry still has some catching up to do to reach the levels of maturity of consumer battery manufacturing and the mainstream automotive industry.
There are many varieties of materials and electrochemical couples available in the present lithium-ion battery market. Many manufacturers are designing battery cells specific to the required applications in terms of voltage, state of charge use, lifetime needs, and safety. The selection of specific electrochemical couples also determines the power and energy ratios, as well as the available energy supply.
The largest component in a battery is the cells. The cells used in EVs can take a variety of different forms like prismatic, cylindrical, and pouch cells. They also have different chemistries including lithium-iron phosphate, lithium NCM, and lithium titanate.
To determine its most appropriate form and chemistry composition, a clear understanding of its application, the drive cycle of the vehicle, and power inputs will be required. Most research on LIBs are focused on diverse active electrode materials and suitable electrolytes for high cutoff voltage applications. These are some of the latest innovations in LIB manufacturing processes that are worth mentioning.
The performance of electrodes is determined by the mixing uniformity. The modification based on the current hydrodynamic shear mixing (HSM) system is at present the most economical improvement of mixing efficiency and uniformity.
The use of ball milling and ultrasonic mixing can significantly increase the mixing uniformity for dry powder mixing and high-concentration slurry. The cost and reliability of large-scale mixing need to be evaluated before they can be industrialized. Besides the mixing method, the mixing sequence is also an important aspect of particle distribution.
Two key processes in electrode fabrication are coating and drying. Using an organic solvent in the slurry may help increase the drying time and recovery cost significantly. However, modifying the current drying method would not directly resolve the challenges faced.
Solvent-free manufacturing emerges as an effective method to skip the drying process and avoid the organic solvent. This technology helps to form a continuous self-supporting electrode film, which is then laminated onto the current collector and becomes the final electrode.
Another benefit of solvent-free manufacturing is the potential of making thick electrodes, which are challenging for the traditional slurry cast method due to the structure distortion after the solvent evaporation.
The vacuum drying process generates intense energy and is time consuming. The present drying method usually places the electrodes under a low-pressure environment of 60 degrees Celsius to 150 degrees Celsius and is heated for more than 12 hours. Using an inert gas supply is also an option to add to the process. However, the lower moisture level may not always lead to better electrochemistry and mechanical properties.
Recently, a fast argon-purging post-drying method at room temperature is being more widely utilized. Results show that the electrode treated with quick argon-purging showed the highest capacity for rate and cycling tests. This shows that the argon-purging method has a strong potential to replace vacuum-drying, especially with its high throughput and low energy consumption benefits.
The optimization of electrode manufacturing processes is a complex subject. It involves robust characterization of the slurry components, either in isolation or in combination with various complementary analytical techniques.
The particle size and size distribution must be balanced, as it brings together various aspects like precursor yield, electrochemical performance, solids loading, and slurry stability. All these factors will influence the overall performance of the battery.
It is also important that the synthesized material has the right chemical (elemental) composition to maintain consistent product quality, stability, and product safety. There are several widely used analytical tools used for battery characterization during the manufacturing process:
These analytical tools will provide users with the relevant materials information and lay the foundation for optimizing the properties of the slurry ingredients. These tools also help to meet the objective of achieving the desired electrochemical performance and high electrode manufacturing efficiency.
There are still some ways to go before the lithium-ion battery is accepted by the masses and becomes the market standard. LIB technology still needs to resolve certain aspects of safety and attain the necessary consistent performance.
At the consumer end, cost reduction for mass-scale adoption in applications like EV is still a faraway goal. However, the technology continues to show improved results through new research ideas and innovations in the development of new battery materials, increased production efficiency, and lower production costs.
Reach out to us for more updates on the EV battery market and its applications in markets your business operates in.
Alan Boey has been in the X-ray analytical instrument business for the past 14 years, servicing various industries from minerals and mining, metal manufacturing to electronics and semiconductor businesses. Alan is now engaged with DKSH as a regional product manager for Southeast Asia, specializing in X-ray analytical instruments and providing solutions to fulfill market requirements in material analysis with X-ray diffraction techniques as well as elemental determination via X-ray fluorescence methods.