Batteries with
clay-based electrolyte/separators were tested at up to 120 degrees Celsius
and showed strong
performance over 120 charge-discharge cycles, according to
scientists at Rice
University. (Credit: Kaushik Kalaga/Rice University)
(November 10, 2015) Rice
University scientists develop materials to power devices in harsh
environments
A unique combination of materials developed at Rice
University, including a clay-based electrolyte, may solve a problem for
rechargeable lithium-ion batteries destined for harsh environments.
The lithium-ion chemistry-based battery revealed this week
is robust enough to supply stable electrochemical power in temperatures up to
120 degrees Celsius (248 degrees Fahrenheit). Such batteries could find use in
space, defense and oil and gas applications, among others.
A clay-based
compound invented at Rice University is an electrolyte and a separator for
lithium-ion
batteries for use in high-temperature environments. (Credit: Jeff Fitlow/Rice
University)
Chemist Pulickel Ajayan and his colleagues at Rice and at
Wayne State University in Detroit describe the material this month in the
American Chemical Society journal ACS Applied Materials and Interfaces.
This discovery, like earlier work on supercapacitors by the
lab, depends on the malleable qualities of bentonite clay and room-temperature
ionic liquids that serve as both a separator and an electrolyte system and
provide a conductive path between a battery’s anode and cathode.
Rice University
graduate student Kaushik Kalaga mixes an electrolyte from clay and a solution
of ionic liquid
and lithium salt. The compound can be used in
rechargeable lithium-ion batteries
that are suitable
for harsh environments. (Credit: Jeff Fitlow/Rice University)
“Clay naturally has a lot of moisture in it, and that’s not
a problem when you’re doing supercapacitors,” said Kaushik Kalaga, a graduate
student in Ajayan’s lab and lead author of the new study. “But a battery has to
have a lithium-ion conductive species in the electrolyte to conduct lithium
ions from the cathode or anode, or vice versa, when you charge and discharge.
“Lithium is very reactive with water, so our first challenge
was to eliminate water from the clay while keeping its structure intact,” he
said.
Kaushik Kalaga
spreads a clay-based electrolyte/separator on one half of a button battery for
testing. The
batteries are meant for high-temperature environments where present
lithium-ion
batteries cannot be used. (Credit: Jeff Fitlow/Rice University)
Kalaga and his team started by baking commercial clay
particles at 650 C for an hour to dry them out. They then combined a
room-temperature ionic liquid and lithium salt and mixed them into the clay in
an oxygen-free glove box. The liquefied salt acts as a source of lithium ions
that conduct through the electrolyte to the electrodes.
The researchers spread the resulting peanut butter-like
slurry between lithium metal electrodes and encapsulated them in coin-shaped
batteries for testing at various temperatures.