Obtaining information on a battery state of charge is key to enabling a safe and efficient charging and discharging process for Lithium-Sulfur batteries. One method is to record terminal voltage fluctuations that are generated by the internal chemical processes themselves.
Stochastic processes appearing during battery discharge may generate voltage fluctuations at different frequency ranges. The value and slope of these fluctuations at specific frequencies can hint at the state of charge, state of health, manufacturing defects, and other properties of batteries. Understanding the evolution of voltage fluctuations in batteries and other electrochemical power sources is an integral part of any precise electronics measurement or device design.
Brno University has measured the voltage fluctuations of lithium-sulfur and nickel–metal-hydride cells in different time intervals at cell charging. The experiments have identified the main sources of voltage fluctuations: These are fluctuations of the potential barrier on the electrode electrolyte interface and generation recombination processes due to chemical redox reactions, happening in the cell during discharge. Understanding the fluctuation sources is a significant step towards modelling and understanding battery-level voltage fluctuations as well.