Hydronium is a positively charged ion produced when a proton is added to a water molecule. The researchers have demonstrated that hydronium ions can be reversibly stored in an electrode material consisting of PTCDA; an organic, crystalline, molecular solid. The battery uses dilute sulphuric acid as the electrolyte.
"It doesn't use lithium or sodium or potassium to carry the charge, and just uses acid as the electrolyte,” said assistant professor Xiulei Ji. “There's a huge natural abundance of acid, so it's highly renewable and sustainable."
According to Ji, cations used in batteries have always been alkali metal, alkaline earth metals or aluminium.
"No non-metal cations were being considered seriously for batteries," he said.
The study observed a big dilation of the PTCDA lattice structure during intercalation – which meant the electrode was being charged.
"Organic solids are not typically contemplated as crystalline electrode materials, but many are crystalline, arranged in an ordered structure," Ji explained. “PTCDA has a lot of internal space between its molecule constituents so it provides an opportunity for storing big ions and good capacity."
The hydronium ions also said to migrate through the electrode structure with low friction which translates to high power.
"It's not going to power electric cars," Ji said. "But it does provide an opportunity for battery researchers to go in a new direction as they look for alternatives for energy storage, particularly for stationary grid storage."