Manufacturing of a battery
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2020/12/15 16:04:52
At first glance, a battery has cells, modules and strings – which makes it similar to a PV panel. However, major differences become obvious when comparing the individual cells. A PV cell operates according to the quantum photovoltaic effect; a battery cell relies on chemical reactions. The operating principle of a battery is more like a chemical process engineering plant, and as a result the manufacturing processes differ significantly.
Unlike PV cells, lithium-ion battery cells need to be monitored individually for voltage, current and temperature for safety and performance reasons. The quality and accuracy of the battery management system plays an equally important role in the performance and safety of the overall battery system. That means all processes related to the manufacturing of the corresponding electronics need to be managed similarly to the production of a PV inverter.
Making a high performance, safe battery system is not rocket science, but it does require extensive diligence. The main challenge is in creating a three-dimensional structure (a round or prismatic cell) out of a largely two-dimensional structure (layers of foil).
As an example, a common 50MWh BESS will have a surface area in the magnitude of 500,000 square meters (i.e. approximately 5,000,000 square feet) of electrode pairs. That’s equivalent to the area of 70 soccer fields. If the BESS were coupled to a 50MWp PV power plant, the surface area of the battery cells would be larger than the surface area of the PV panels charging them.
To manufacture these cells, it is critical to create this surface with extreme precision. A common benchmark is that the maximum deviation of surface thickness should not exceed 1% to 2%. If a manufacturer exceeds this, the battery runs a higher risk of becoming a safety hazard and suffering accelerated performance degradation.
The manufacturing of a battery can generally be separated into four major steps:
1. Initial quality control and electrode production
2. Cell stack assembly
3. Drying, electrolyte filling, formatting, ageing, and sorting
4. Assembling cells into a battery
Cover Image: The manufacturing quality of lithium-ion batteries is a key determinant of lifetime performance. Image: PI Berlin.
This is the opening extract of an article which appears in full in the latest edition of our quarterly technical journal, PV Tech Power (Vol.24), in 'Storage & Smart Power', the dedicated section contributed by the team at Energy-Storage.news. The full article looks at each of the different manufacturing steps in detail, as well as discussing other critical factors in decision-making such as warranties and testing. To download the entire article as an individual paper, or to subscribe to or download the entire 108-page book, visit the PV Tech Store.
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