South Korean researchers have found the key to producing ultra-thin, high-performance solid-state batteries.
Standard lithium-ion batteries use a liquid electrolyte, which can be flammable.
Solid-state batteries replace this with a safer solid electrolyte. But, manufacturing these solid electrolytes has been a challenge.
Previous methods resulted in thick membranes – sometimes up to 1 millimeter — that reduced energy density.
The Electronics and Telecommunications Research Institute (ETRI) team has developed a game-changing solution: an ultra-thin solid electrolyte membrane, just 18 micrometers thick. That’s nearly as thin as the separators in today’s batteries.
The team has also proven the concept by building a pouch-type cell battery with the new membrane, showing it works well and could be commercially viable.
Solid electrolyte membrane
Researchers created a very thin solid electrolyte membrane (18µm) using a special binder and a dry process.
They used a special binder material that fibrillates or forms tiny fibers when subjected to mechanical force.
The research team achieved a reduction in cell volume, leading to the development of a high-energy density and high-performance all-solid-state secondary battery.
This innovation enhances the battery’s energy storage capacity by up to 10 times compared to cells utilizing a thicker, 1 mm solid electrolyte membrane.
The study discovered that the size of the binder molecules directly impacts how strongly they link together, which is crucial for making strong, thin membranes. This discovery gives manufacturers a precise formula for creating cost-effective, high-quality membranes by using the optimal amount of binder.
“Through an in-depth understanding of the polymer binder fibrillation, we have solved the problem of ultra-thin solid electrolyte membranes, which has been a challenge, with a simple and fast process,” said Shin Dong Ok, the principal researcher at ETRI.
Eliminates the use of solvents
Solid-state batteries are safer than current batteries because they replace flammable liquids with solid materials, preventing fires, explosions, and leaks.
In solid-state batteries, the solid electrolyte membrane is important; it moves ions and stops the electrodes from touching.
Liquid electrolytes are added directly into battery cells, whereas solid electrolytes are pre-made as membranes and then incorporated into the cell during manufacturing.
Moreover, the dry manufacturing method for solid electrolyte membranes eliminates environmentally harmful solvents. This creates stronger, more conductive membranes with precise thickness control.
The researchers’ key achievement is defining a precise mechanical mixing (shearing) standard for dry-process solid-state battery manufacturing.
The development could pave the way for the creation of high-energy, lighter, and smaller solid-state batteries by using ultra-thin membranes that improve ion transfer.
“The success of creating large-scale solid electrolyte membranes with separator-level thickness is expected to significantly improve energy density, which will increase the commercialization potential of all-solid-state secondary batteries with high price competitiveness,” said Park Young Sam, the principal researcher at ETRI’s Smart Materials Research Section, in the press release.
Although the study centered on making thinner solid electrolytes, ETRI researchers will continue to improve ion flow and electrode connections.