Non-flammable electrolyte could enable safe potassium ion batteries
Lithium ion technology currently dominates energy storage technology, in particular when it comes to electric and hybrid vehicles. However, this battery technology also has major disadvantages such as high costs and environmental problems, and the highly combustible electrolyte makes the battery unsafe. Cheaper ions will replace lithium ions in the future. Potassium ions, for example, are readily available and in principle have good battery properties. However, potassium ion batteries are not safe either, and non-combustible electrolytes are not yet available for them as well.
Materials scientist Zaiping Guo and her team from the University of Wollongong (Australia) may have found a solution to this problem. The researchers developed an electrolyte for the potassium and potassium ion battery based on a fireproofing agent. This electrolyte is not only non-flammable, but also enables the battery to operate at lower salt concentrations, as required for large-scale technical applications, the scientists report.
The main component of the electrolyte is triethyl phosphate, a substance also known as a flame retardant, which has already been tested as a solvent in lithium ion batteries. Here, however, it proved to be less suitable because too high salt concentrations were required and the electrolyte could not be diluted. Only diluted electrolytes are suitable on an industrial scale. However, the scientists were able to reduce the concentration with potassium salts. For potassium and potassium ion batteries, they produced a triethyl phosphate potassium salt electrolyte that is non-flammable and, in suitable concentrations, enables stable charging and discharging cycles. Such concentrations are interesting for technical applications such as electricity storage in the grid area.
According to the authors, the high performance is due to the formation of a uniform solid conductive layer on the electrode. They observed the layer only with the phosphate electrolyte. Conventional carbonate electrolytes could not build up this layer. The phosphate electrolyte remained stable even during repeated cycles. Under the same conditions, however, the conventional carbonate electrolyte decomposed.
These results open up the prospect of safer potassium ion batteries using novel phosphate electrolytes, the scientists believe. Such electrolytes based on flame retardants could be further developed and incorporated into the design of other non-flammable battery systems.
More information: https://scholars.uow.edu.au/display/zaiping_guo