Lithium-ion batteries are the current standard for mobile devices and electric vehicle (EV) power sources. However, aqueous batteries are emerging as an alternative to lithium.
Specifically, a new study from the Tokyo University of Science (TUS) in Japan shows the potential potassium-ion batteries (KIBs) may have as an alternative to lithium. These alternatives are emerging due to the environmental, safety and limited availability of lithium.
KIBs are made from abundant materials and are safer than lithium-based batteries and can use a water-in-salt electrolyte (WISE), making it thermally and chemically stable. However, solid-electrolyte interphases (SEI) that form electrodes and electrolyte solution to stabilize the technology in KIBs has not been tested.
How they tested
Researchers used two analytical techniques to test KIBs: Scanning electrochemical microscopy (SECM); and operando electrochemical mass spectrometry (OEMS). These were used to observe how SEI forms and reacts in real time during the operation of a KIBs.
The TUS team found that SEI forms a passivating layer in WISE similar to the reaction in lithium-ion batteries. This ensure that a stable performance and higher durability of KIBs was possible. However, the coverage of the SEI layer was incomplete at higher operating voltages leading to hydrogen evolution.
“While our results reveal interesting details on the properties and stability of SEI found in one particular WISE, we should also focus on reinforcing the SEI network to achieve improved functionality,” said Shinichi Komaba, professor at TUS. “SEI could perhaps be improved by the development of other electrolytes that produce unique SEIs, but also through the incorporation of electrolyte additives or electrode surface pretreatment.”
Additionally, researchers found that the SECM and OEMS techniques used showed a means to track the development, coverage, ion transfer and stability of SEI that could be used in a variety of electrolytes and electrodes.
Potassium-ion batteries and other aqueous batteries will be needed in the future and could replace expensive and hazardous lithium batteries used for EVs, energy storage, smart grids and marine applications. This will also aid in the transition to carbon-neutral energy generation, TUS said.
The full research can be found in the journal Wiley Online Library.