Properties of the solid-electrolyte interphase (SEI) found in a highly concentrated K(FSA)0.6(OTf)0.4 ⋅ 1H2O electrolyte are being revealed through advanced in situ methods. Scanning electrochemical microscopy (SECM) reveals a passivating but discontinuous SEI film. Operando mass spectrometry (OEMS) measurements confirm a shift in the evolution of detectable H2 from −0.9 V to <−1.4 V vs. Ag/AgCl when changing from dilute to concentrated electrolytes. Credit: Dr. Zachary T. Gossage et al.
A team of researchers from Tokyo University of Science- (TUS) have published their findings on solid-electrolyte interphases (SEI) in Potassium-ion batteries (KIBs). Utilizing scanning electron microscopy and operando electrochemical mass spectrometry the researchers observed how SEI forms in real time.
Lithium-ion batteries (LIB) have long been the go-to power source for electronic devices, however, with the limited availability of lithium as well as the environmental impacts of its extraction researchers are on the hunt for its replacement. KIBs are a prominent prospect as they are made from abundant materials and offer increased safety over their lithium counterparts. The largest challenge currently faced by researchers is stemming the hydrogen evolution at the negative electrode. In lithium-ion batteries, the SEI that forms between the electrodes helps stabilize the electrodes, however, this stabilization has scarcely been researched for use in KIBs.
In the study, published in Angewandte Chemie International Edition, the researchers discovered that SEI forms a passive layer in water-in-salt electrolyte (WISE) batteries such as KIBs, similar to how it behaves in LIBs. This layer helps suppress hydrogen evolution, ensuring improved stability and durability in KIBs.
“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, a TUS professor who led the study. “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.”
Aqueous batteries such as KIBs will play a critical role in sustainability and safety in the future. Their further development could provide a promising alternative to LIBs and increase energy storage accessibility while providing a greener pathway forward.