Novel way to fill lithium-ion cells faster

Neutrons pave the way for the accelerated production of lithium-ion cells.

Mounting of a battery cell in the instrument ANTARES at FRM II. (Photo: Wenzel Schürmann / TUM)
Mounting of a battery cell in the instrument ANTARES at FRM II. (Photo: Wenzel Schürmann / TUM)

Scientists at the Technical University of Munich along with the Bosch scientists have created a way that use neutrons to analyze the filling of lithium-ion batteries for hybrid cars with electrolytes.

Filling of lithium cells with electrolyte fluid is one of the most critical and time-consuming processes in battery production. While the genuine filling process takes just a couple of moments, battery makers regularly hold up a few hours to guarantee the fluid is completely assimilated into the pores of the cathode stack. The fact that neutrons are hardly absorbed by the metal battery housing makes them ideal for analyzing batteries.

Now, scientists investigated the filling process at the neutron imaging and tomography facility ANTARES of the research neutron source FRM II.

Bosch developer Dr. Wolfgang Weydanz said, “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. That costs time and money.”

Scientists primarily realized that electrodes were wetted completely in a vacuum within just 50 minutes. Under ordinary weight, this takes around 100 minutes. The fluid spreads uniformly in the battery cell from every one of the four sides, from the outside in.

Moreover, the cathodes assimilate 10% less electrolyte under ordinary weight. The culprit is gassed that hinder the wetting process, as the scientists were able to demonstrate for the first time using the neutrons.

The study is published online in the journal ScienceDirect.