Researchers Develop a Solid Electrolyte to Create Safer and Efficient Batteries

The chloride nature of the electrolyte is key to the battery’s stability at operating conditions above 4 volts


Researchers at the University of Waterloo, Canada, who are members of the Joint Center for Energy Storage Research in the U.S. (JCESR), claimed that they had developed a new solid electrolyte to help create solid-state lithium-ion batteries.

The electrolyte is composed of lithium, scandium, indium, and chlorine and conducts lithium-ions well but electrons poorly. The combination is essential to create an all-solid-state battery that functions without losing the capacity for more than a hundred cycles at a high voltage of above four volts and thousands of cycles at intermediate voltage.

The researchers said the chloride nature of the electrolyte is key to its stability at operating conditions above 4 volts that is suitable for typical cathode materials that form the mainstay of today’s lithium-ion cells.

Linda Nazar, a research professor at Waterloo University and a member of JCESR, said the main attraction of a solid-state electrolyte is that it could not catch fire, and it allowed for efficient placement in the battery cell.

According to the researchers, existing iterations of solid-state electrolytes focus heavily on sulfides, which oxidize and degrade above 2.5 volts. Therefore, they require incorporating an insulating coating around the cathode material that operates above 4 volts. This impairs the ability of electrons and lithium ions to move from the electrolyte and into the cathode.

To develop a chloride electrolyte, the researchers decided to swap out half of the indium for scandium that provided lower electronic and higher ionic conductivity. The new technology became attractive because they oxidize only at high voltages, and some are chemically compatible with the best cathodes available.

Nazar said spinel is a crucial chemical to the ionic conductivity in the material’s crisscrossing 3D structure. The researchers balanced the load of spinel with as many charge-carrying ions as possible and left sites open for the ions to move through.

The researchers said an ideal solution would be to have half the sites in the spinel structure be lithium occupied while the other half remained open. However, creating that situation is hard to design.

In addition to the good ionic conductivity of the lithium, the researchers needed to make sure that the electrons could not move easily through the electrolyte to trigger its decomposition at high voltage.

Nazar said the new technology helps establish a clear interface between the cathode material and solid electrolytes, responsible for the stable performance even with high amounts of active materials in the cathode.

As a result, solid-state lithium-ion batteries, consisting of entirely solid components, have become attractive because they offer an enticing combination of higher safety and increased energy density.

In September 2021, researchers from Helmholtz Institute Ulm and Cheongju University developed a new lithium-metal battery that claims to offer a high energy density of 560 watt-hours per kilogram with good stability.

Mercom had earlier reported that QuantumScape, a solid-state lithium metal batteries developer, designed a solid-state lithium battery, which could increase the range by 80% compared to ordinary lithium-ion batteries.