Which are the needs and requirements in lithium battery cell manufacturing? We would provide you some tips to improve your quality check and inspection strategy in lithium battery cell manufacturing. A strong quality inspection strategy allows you to improve heavily your lithium battery cell performance and production quantity.
Few days ago I had very interesting meetings with Inspection systems makers about quality inspection in lithium cell manfuacturing lines and many opinions and topics raised during these long meetings.
Since we’ve worked and we are working on both sides of the supply chain equipment/device makers and cell/battery pack makers we have very clear the needs of both and even we understand the point of views of both but as usual is important to find a compromise as soon as possible to avoid any delay in the project.
We can start from the cell/battery maker point of view:
When they need to start a pilot production, the want to have full process control and data to start to optimize the process so almost every time they want to check and monitor the process with multiple device to try to get as much data as possible.
For sure their target is not just to a full control and overview of the process but even get the machine in very short time with the cheapest price.
What is the equipment/device maker point of view?
Get clear requirements soon as possible to choose the hardware and the system configuration from mechanical, electrical and software point of view.
A real example
Welding process in lithium tabless cylindrical batteries.
Let’s assume we are going to weld the cathode disc to the can rivet terminal.
There are some strategies to do that (you can find more details, real example and explanation in our “From 0 to Hero – Tabless Cylindrical cell manufacturing Guideline”), one strategy is welding through the JR inner core diameter or from the bottom side of the rivet.
For sure this two solutions have different constraints and allows different systems.
Let’s assume we use laser welding technology (you can find all Laser welding applications for cylindrical cells here):
- If we weld through the JR inner core diameter is really difficult perform a vision inspection of the welding spot since the light should pass through the entire JR height in a hole of 5-7mm Diameter.
A pathway could be use a process monitoring system based on interferometer of photo-diode sensor. These systems allows to monitor online and in-live the welding process and with a close loop even make it more stable.
A second pathway is measure the electrical resistance of the welding spot. Indeed, the role of the welding in cell manufacturing is ensure a good connection between parts which usually are working at low stress level but even ensure a super low electrical resistance to avoid any heat up during charging and discharging process or at least avoid super hot points where all the heat is concentrated.
- If we weld from the bottom side of the rivet, the welding spot is visible so we can use a vision inspection, now the question is 2D or 3D camera?
For sure we can still use the laser process monitoring system and even the electrical resistance measurement.
Does have sense use multiple inspection systems in lithium cell manufacturing for each single process?
The answer is: depends what you want to check and which data you want to collect.
From our perspective as lithium battery consultants, the inspection systems or process monitoring systems choice is based on the following KPIs:
- Data Processing Time and response time
- Device dimension
- Price
- Close loop possibility – Open system
- Reliability
Data processing Time:
The lithium cell and battery pack manufacturing is moving every year to higher throughput machines and equipment. This evolution foreseen every year shorter cycle time for each process flow so faster communication between devices, faster acquisition of data, faster response and higher system reliability.
The target is to reach higherlithium battery cell throughput keeping constant the number of process units and module. If 5 years ago the welding module was able to guarantee 10 cells/minute, now the same process should take place at 50cells/minute throughput.
The data processing time and response time are based on the inspection or monitoring technology, on the communication systems and the number of data we’re getting from the process.
Device dimension:
In lithium cell manufacturing the space has a very high cost in term of investment and operating cost. The lithium cell manufacturing take place in dry room which the price increase with the dry room area. To minimize the costs machines and equipment must be small!
In small equipment even the inspection device should be small and compact otherwise we lose the benefit of a small machine. Even for this reason in lithium battery manufacturing is important to increase the throughput keeping constant the number of machine modules or stations.
Price:
Price is not a super important KPI for inspection system especially in lithium battery manufacturing. Systems which allow the company to improve the production OEE have a huge adding value for the end user. Lithium battery companies are happy to spend money for something with allows them to gain more money, is a investment!
Close loop possibility – Open system:
We start saying the inspection system or process monitoring system MUST provide data, must provide numbers! Quality in lithium battery manufacturing is a must for OEE and and users. You can classify your lithium battery cells quality only based on data.
With data we’re able to build AI algorithms, define working window and optimize the process.
The inspection and monitoring system have to provide data to stabilize the process and understand how the process parameters and the quality data affect the overall battery cell performance and working life.
Reliability:
The measuring or inspection method of lithium battery cell inspection systems should be as much robust as possible. The physic principle how to get the information about the quality should be robust and simple. The idea is to install inspection systems to improve the quality of lithium battery cells and improve the production OEE. The data must be reliable.
Build a quality management system in lithium battery manufacturing is not easy, especially when you need to start from zero. It’s important to understand which are the main process to inspect and why. Based on these answers is possible to define the best solutions present in the market.