Inspired by the
principles of a conventional sodium ion battery, Illinois mechanical science
and engineering
professor Kyle Smith, right, and graduate student Rylan Dmello found they
could desalinate
salt water more efficiently than using traditional methods. Photo by L. Brian
Stauffer
(February 5, 2016) The
technology that charges batteries for electronic devices could provide fresh
water from salty seas, says a new study by University of Illinois engineers.
Electricity running through a salt water-filled battery draws the salt ions out
of the water.
Illinois mechanical science and engineering professor Kyle
Smith and graduate student Rylan Dmello published their work in the Journal of
the Electrochemical Society.
“We are developing a device that will use the materials in
batteries to take salt out of water with the smallest amount of energy that we
can,” Smith said. “One thing I’m excited about is that by publishing this
paper, we’re introducing a new type of device to the battery community and to
the desalination community.”
Interest in water desalination technology has risen as water
needs have grown, particularly in drought-stricken areas. However, technical
hurdles and the enormous amounts of energy required have prevented wide-scale
implementation. The most-used method, reverse osmosis, pushes water through a
membrane that keeps out the salt, a costly and energy-intensive process. By
contrast, the battery method uses electricity to draw charged salt ions out of
the water.
The researchers were inspired by sodium ion batteries, which
contain salt water. Batteries have two chambers, a positive electrode and a
negative electrode, with a separator in between that the ions can flow across.
When the battery discharges, the sodium and chloride ions – the two elements of
salt – are drawn to one chamber, leaving desalinated water in the other.
In a normal battery, the ions diffuse back when the current
flows the other direction. The Illinois researchers had to find a way to keep
the salt out of the now-pure water.
“In a conventional battery, the separator allows salt to
diffuse from the positive electrode into the negative electrode,” Smith said.
“That limits how much salt depletion can occur. We put a membrane that blocks
sodium between the two electrodes, so we could keep it out of the side that’s
desalinated.”