Deutsche Version  ACT
News | 7.7.2016
Accumulators

Sound waves reduce charging times

Staff members Sandra Ebert and Sabrina Tietze at the test rig in the laboratory at the Institute of Sensor and Actuator Technology.
© ISAT
Right, subtraction of the two charging curves (left) with and without sound irradiation in the 3-electrode system. The charging curves with (red) and without sound introduction (blue) can be seen at the top.
© ISAT
Test rig by Seuffer.
© Seuffer GmbH

Accumulator charging time is particularly important for electric vehicles. Transport processes in the boundary layer between the electrode and electrolyte are among the limiting factors for charging speed. In the four-year BELAKUSTIK research project, scientists investigated whether charge transport can be accelerated with high-frequency sound waves. In experiments with lead acid batteries, charging times were reduced by up to 10 per cent. However, further research is required into practical applications in battery systems.

Acoustic sound waves influence the kinetics of electrochemical processes. Scientists have proven that using electropolishing experiments. In their experiments, they succeeded in increasing current by over 50 per cent, which is indicative of increased charge carrier transport.
Can these results be transferred to accumulators? The project partners tried to answer this question using lead-sulphuric acid batteries as an example. For this purpose, they built an automated test rig to irradiate high-frequency sound waves into battery systems.

Lead-acid cells with different numbers of electrodes were set up for the accumulator experiments. They found that the acoustic waves are scattered and dampened at the lattice structure and lead paste of the electrodes in the accumulator. In spite of the structure, which is not conducive to sound wave dispersion, waves were still stimulated onto these electrodes. An influence on the charging and discharging curves due to the acoustic waves was also observed.

The scientists succeeded in proving the influence of acoustic waves on charging properties in both the 3-electrode system and the 15-electrode system (figure at top left). The difference between the charging curve without sound (blue) and the charging curve with sound (red) shows the significant influence of the sound waves on electrochemical transport processes. In the 15-electrode system, the charging time decreased by up to 10 per cent.

In spite of initial successes, the researchers played down the expectations for market maturity of additional battery components. They are currently investigating whether other types of battery offer better chances of success. Redox flow batteries are promising candidates. Their geometry is more suitable for homogeneous wave introduction.

Supported by: The Federal Government on the basis of a decision by the German Bundestag

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