Water-based batteries can be an alternative to lithium

Metal-free water-based batteries are unique and completely different from those that use cobalt in its lithium-ion form. The research group's focus on this type of battery stems from a desire for greater control over the domestic supply chain, as cobalt and lithium are usually sourced in other countries. In addition, safer battery chemistry could prevent potential fires.

Chemical engineering professor dr. Jodie Lutkenhaus and Assistant Professor of Chemistry Dr. Daniel Tabor published their findings on lithium-free batteries in the journal Nature Materials.

"There would be no more battery fires because everything is water-based," said Lutkenhaus. If the expected shortage of materials occurs in the future, the price of lithium-ion batteries will likely increase. If we have an alternative battery, we can turn to this chemical composition, where the supply is much more stable, because we can make them in the United States of America and the materials to make them are available here."

Lutkenhaus said that water batteries consist of a cathode, an electrolyte and an anode. Cathodes and anodes are polymers that can store energy, and the electrolyte is water mixed with organic salts. The electrolyte is key to ionic conductivity and energy storage through interaction with the electrode.

»Če electrode during its cycles tooč it swells up, then it can't transfer electrons very well and you lose all of your performance,'' she said. "I believe there is a 1,000 percent difference in energy storage capacity depending on the choice of electrolyte due to swelling effects."

According to their article, redox-active, non-conjugated radical polymers (electrodes) are promising candidates for metal-free water batteries due to the high discharge voltage of the polymers and fast redox kinetics. The reaction is complex and difficult to solve due to the simultaneous transfer of electrons, ions and water molecules.

Tabor's research group supplemented the experimental efforts with computer simulations and analyses. The simulations enabled insight into the microscopic molecular picture of structure and dynamics.

“Theory and experiment often work closely together in understanding these materials. One of the new things we do computationally in this paper is to actually charge the electrode to more than state of charge and we see how the surroundings respond to that charge," said Tabor.

The researchers macroscopically observed whether the battery's cathode performed better in the presence of certain types of salt by precisely measuring how much water and salt went into the battery during operation.

"We did this to explain what we observed experimentally," he said. "Now we would like to extend our simulations to future systems. We had to confirm our theory about what the forces are that drive such injection of water and solvent."

“With this new energy storage technology, we are one step closer to lithium-free batteries. At the molecular level, we have a better idea of why some battery electrodes work better than others, and this gives us strong evidence and guidance on how to move forward in materials design,' said Tabor.