Paper Biomass Could Yield Lithium-Sulfur Batteries


Rensselaer Polytechnic Institute

A byproduct of the papermaking industry could be the answer to creating long-lasting lithium-sulfur batteries.

A team from Rensselaer Polytechnic Institute has created a method to use sulfonated carbon waste called lignosulfonate to build a rechargeable lithium-sulfur battery.

Lignosulfonate is typically combusted on site, releasing carbon dioxide into the atmosphere after sulfur has been captured for reuse. A battery built with the abundant and cheap material could be used to power big data centers, as well as provide a cheaper energy-storage option for microgrids and the traditional electric grid.

“Our research demonstrates the potential of using industrial paper-mill byproducts to design sustainable, low-cost electrode materials for lithium-sulfur batteries,” Trevor Simmons, a Rensselaer research scientist who developed the technology with his colleagues at the Center for Future Energy Systems (CFES), said in a statement.

Rechargeable batteries have two electrodes—a positive cathode and a negative anode. A liquid electrolyte is placed in between the electrodes to serve as a medium for the chemical reactions that produce electric current. In a lithium-sulfur battery, the cathode is made of a sulfur-carbon matrix and the anode is comprised of a lithium metal oxide.

Sulfur is nonconductive in its elemental form. When combined with carbon at elevated temperatures it becomes highly conductive, but can easily dissolve into a battery’s electrolyte, causing the electrodes on either side to deteriorate after only a few cycles.

Different forms of carbon, like nanotubes and complex carbon foams, have been tried to confine the sulfur in place, but have not been successful.

“Our method provides a simple way to create an optimal sulfur-based cathode from a single raw material,” Simmons said.

The research team developed a dark syrupy substance dubbed “brown liquor,” which they dried and then heated to about 700 degrees Celsius in a quartz tube furnace.

The high heat drives off most of the sulfur gas, while retaining some of the sulfur as polysulfides—chains of sulfur atoms—that are embedded deep within an activated carbon matrix. The heating process is then repeated until the correct amount of sulfur is trapped within the carbon matrix.

The researchers then ground up the material and mix it with an inert polymer binder to create a cathode coating on aluminum foil.

Thus far, the team has created a lithium-sulfur battery prototype the size of a watch battery that can cycle approximately 200 times.

They will now attempt to scale up the prototype to markedly increase the discharge rate and the battery’s cycle life.

“In repurposing this biomass, the researchers working with CFES are making a significant contribution to environmental preservation while building a more efficient battery that could provide a much-needed boost for the energy storage industry,” Martin Byrne, CFES director of business development, said in a statement.

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