Lithium-ion batteries are the preferred power source for devices ranging from cardiac pacemakers to the rapidly growing fleet of electric vehicles. They are conceptually simple devices consisting of a uniform bit of lithium compound located on either side of a collector.
The Devil, of course, is in the details.
The lithium compound must have identical physical characteristics including thickness and density or the battery won’t last very long. In a pacemaker battery, for example, it starts out as a reactive powder loaded into a die the size of a quarter and pressed to a precisely specified thickness with up to 10,000 lb of force while it goes through a four-minute thermal cure cycle.
The thickness of the disk has to be monitored and maintained during the entire cycle by adjusting the pressure as the physical characteristics of the powder change in response to the thermal cure cycle. And since the battery is going into a device that will be implanted into a human body, the process also needs to generate a quality report with force, position, temperature and time information for every single piece that’s produced.
This is exactly the application Promess solved for one battery manufacturer using a standard Electro-Mechanical Assembly Press (EMAP) fully electric servo press with built-in force and position monitoring to do the work and a Promess UltraPRO controller to make the setup and control easy and flexible. That system has been replicated successfully over the last decade for a broad range of small lithium-ion batteries.
But what about batteries that aren’t small? The lithium compound used to manufacture larger batteries, including those for electric vehicles, is produced in sheets whose area is measured in square feet rather than square inches, requiring press forces up to 100,000 lb. That requires an entirely different kind of press, but fortunately not a different kind of technology because the electric servo press and UltraPRO combination has proven to be quite scalable with a little creative engineering.
Promess took on the challenge and the result is a platen-type press technology based on the concept of joined motion using the UltraPRO to synchronize multiple EMAP units to drive a platen that applies force uniformly over a large area. EMAP locations around the platen are flexible, but the most common configuration places one at each corner to even out the loading.
The key to making this work is controlling the EMAPs to provide even loading over the entire platen area. Since each EMAP has a built-in force and position sensor, an operator can use this information to individually adjust platen loading on the fly. A global force and position reading is given by summing this data in real time using Promess’ patented Dabex live variables. This is easily handled by the UltraPRO controller. This upscaled version of the technology can generate up to 400,000 lb of force in a press able to produce sheets of lithium compound measuring 4 x 8′ and larger.
It’s efficient because one piece of software seamlessly controls all axes using simple step-based programming for easy setup. The units are joined and synchronized by Promess before shipping so nothing needs to be adjusted when the unit arrives.
It’s economical because no PLC is needed. The Promess software contains conditional logic that can be scaled from basic to advanced for any process. Calibration is also simple with easy to use interface and autocalibration.
It’s extremely flexible. Users can adopt advanced programming features in their development that are considered “standard” to the Promess software, such as using closed-loop control methods to press to a rate of change, or a full press-load dwell cycle. In doing so, processes with these powdered materials can be infinitely customized to achieve results currently unobtainable using standard hydraulic controls. Once the development is completed, these programs can easily be transferred from the development stations to the production cells. Generally, this is done using the same development programs with little change, saving time and money.
Scaling the proven technology that makes pacemaker batteries longer lasting and more reliable promises to bring the same benefits to lithium-ion battery production across the board. Given the explosive growth of devices that depend on these batteries, and the high cost of the materials used in their manufacture, the benefits of precision manufacturing technologies like Promess’ Platen Press are sure to become increasingly important in the coming years.