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High-frequency EIS: a powerful tool for the future of mobility

11.03.2024 г.

Артикул

The market for electric vehicles (EVs) is growing rapidly due to environmental and economic factors. As EVs become more mainstream, developments in battery technology will be critical to support the energy storage needs of this growing industry. Solid-state batteries (SSBs) offer a promising alternative to conventional lithium-ion battery technology. Electrochemical characterization of SSBs can be difficult, but by using electrochemical impedance spectroscopy (EIS) at high frequencies (up to 10 MHz), rapid processes are more easily captured.

Battery charging status interface on electric vehicle

Introduction

Electric vehicles offer zero direct emissions and lower fueling costs compared to vehicles powered by fossil fuels. Global EV sales reached 13.6 million units in 2023 and these numbers are projected to rise significantly in the near future [1,2]. 

The batteries that power EVs must store more energy while also being safer, smaller, lighter, and less expensive than current technology allows. Improvements in energy density are particularly important, as battery packs are one of the heaviest and most expensive components in EVs. Improving battery performance will dictate the pace at which automakers can produce EVs that rival combustion engine vehicles in terms of driving range and purchase price.

As discussed in a previous blog post, solid-state batteries (SSBs) are a potentially superior alternative to Li-ion batteries (LIBs). SSBs could help advance the large-scale adoption of EVs by providing higher energy density using a solid electrolyte material rather than a flammable liquid electrolyte. The inherent toughness of solid electrolytes helps improve safety compared to lithium-ion batteries by greatly reducing the risk of fire from short circuits. In addition, solid electrolytes are typically both chemically and thermally more stable than liquid electrolytes, reducing degradation and dendrite formation over time.

Despite still being in the research and development phase (aside from some exceptions [3]), SSB technology holds great promise for enhancing battery performance. This includes allowing for higher voltages, longer battery life, and faster charging capabilities. Significant challenges remain, however, in developing solid electrolytes that can conduct ions as effectively as liquids do at room temperature.

Though all-solid-state battery systems have great potential, they encounter contact issues at the interfaces between the cathode and electrolyte composite (Figure 1, right). These «solid-solid» interfaces pose challenges to the efficient flow of ions and electrons within the battery.