Neutron tomography shows how battery cells fill with electrolyte
Filling lithium cells with electrolyte fluid after the placement of electrodes in a battery cell is one of the most critical and time-consuming processes in battery production. While the actual filling process takes only a few seconds, battery manufacturers often wait several hours to ensure the liquid is fully absorbed into the pores of the electrode stack.
The fact that neutrons are hardly absorbed by the metal battery housing makes them ideal for analyzing batteries. That is why Bosch worked with scientists from the TU Munich and the University of Erlangen-Nuremberg to investigate the filling process at the ANTARES neutron imaging and tomography facility at TUM.
Manufacturers of lithium cells often fill the empty cells in a vacuum. The process is monitored indirectly using resistance measurements. “To make sure that all the pores of the electrodes are filled with the electrolyte, manufacturers build in large safety margins,” said Dr. Wolfgang Weydanz at Bosch. “That costs time and money.”
The data from the tomography showed that the electrodes were wetted completely in just over 50 minutes in a vacuum, compared to around 100 minutes at atmospheric pressure. The liquid spreads evenly in the battery cell from all four sides, from the outside in.
In addition, the electrodes absorb ten percent less electrolyte under normal pressure as a result of gases that hinder the wetting process, and this was demonstrated for the first time using the neutrons.
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