Making better batteries : local chemical concentration gradient manipulation with ultrasound to prevent dendrite growth during electroplating

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http://urn.fi/URN:NBN:fi:hulib-202105102096
Title: Making better batteries : local chemical concentration gradient manipulation with ultrasound to prevent dendrite growth during electroplating
Author: Malinen, Henri
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2021
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-202105102096
http://hdl.handle.net/10138/329721
Thesis level: master's thesis
Degree program: Materiaalitutkimuksen maisteriohjelma
Master's Programme in Materials Research
Magisterprogrammet i materialforskning
Specialisation: Elektroniikka ja teollisuusfysiikka
Electronics and Industrial Physics
Elektronik och industrifysik
Abstract: Dendrite prevention can be achieved by manipulating the local chemical concentration gradient by ultrasound. An ultrasonic field, which generates acoustic streaming, can manipulate the ionic flux at the electrode surface by altering the local ion concentration gradient at said surface according to the streaming pattern. The pattern is determined by the ultrasonic field and the geometry of the sonication volume. The preventive action can be directed to an arbitrary point on the surface, or be swept across it to achieve a smoother electroplating. Dendritic growth is concentrated to areas of higher concentration gradient. This is because at the electrode surface both the electric and convective fluxes tend to zero. If the reduction of ions into their metallic form is fast enough, the metal layer growth rate is determined by the diffusive flux, which is determined by the ion concentration gradient and the diffusion constant of the ion in the electrolyte. In this study, tin was used as the transported ion instead of lithium for safety reasons. A custom-made battery mockup cell was constructed for the experiments. The anode was imaged with a usb microscope camera to determine the growth of the dendrites during the process. The electroplating current and piezo driving power were varied between 100 mA to 275 mA and 0 to 6.6 W, respectively. With piezo driving electrical power less than 10 W, it was possible to lower the maximum lengths of dendrites. Finite element method simulations were conducted to validate the hypothesis and experimental results. This ultrasonic method could be used to allow rechargeable, lightweight, high capacity lithium metal batteries. The piezos could be integrated into battery chargers.
Subject: Dendrites
Litihum battery
Electroplating
Ultrasound


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