Following months of promising test results, battery researchers at the Department of Energy’s Oak Ridge National Laboratory are recommending that the solid-state battery industry focus on a technique known as isostatic pressing as it looks to commercialize next-generation solid-state batteries.
In an open-access focus review paper for ACS Energy Letters, ORNL researchers recommend attention be given to the little-studied isostatic pressing approach. This process uses fluids and gases such as water, oil or argon inside a machine to apply consistent pressure across a battery component, creating a highly uniform material. With the help of an industry partner that produces this pressing equipment, ORNL researchers found that isostatic pressing could make battery production easier and faster while creating better conditions for energy flow.
(a) Current challenges in processing and integration of solid-state batteries. (b) Uneven density distribution by single uniaxial pressing in rigid die for cylinder. (c) Schematic diagram of a pressure vessel cavity into which the sample is inserted and subjected to isostatic pressure and temperature conditions, and temperature and pressure ranges for Cold Isostatic Processing (CIP) (blue), Warm Isostatic Processing (WIP) (green), and Hot Isostatic Processing (HIP) (orange) techniques. Dixit et al.
ORNL’s Marm Dixit and colleagues found that isostatic pressing can create thin layers of solid, uniform electrolyte, maintaining a high level of contact between the layers for smooth ion movement. The method works with a variety of battery compositions at different temperatures and pressures.
Among the promising results, isostatic pressing was found to be extremely successful at low temperatures and with soft electrolyte materials, which are easier to process and which have favorable crystal structures for ion movement. Previously isostatic pressing of batteries had been done mostly at extremes: very high temperatures or at room temperature, but not in between.
All these materials have their unique advantages that researchers would like to exploit. That’s why it’s important that you can do isostatic pressing at anywhere from room temperature to several thousand degrees Fahrenheit: It means you can use anything from polymers to oxides, the whole range of materials.—Marm Dixit
This versatility is key to a consistent manufacturing process for the broad variety of solid-state battery designs and materials being developed, Dixit said. Isostatic pressing would also be relatively easy to scale up commercially—a finding that has garnered significant attention as companies race to supply solid-state batteries to car manufacturers. Several leading auto companies have announced their intention to sell electric vehicles that run on solid-state batteries within a few years.
Ilias Belharouak, a corporate fellow at ORNL and head of its electrification section, said solid-state battery technology needs to be perfected for large-scale manufacturing.
All solid-state batteries are on a journey for the long haul. But the isostatic pressing technology, if scalable, would provide a way to assemble the battery layers without impractical external pressures.—Ilias Belharouak
Isostatic pressing has been used for decades in fusion bonding and joining materials. Recently, it has been a tool for eliminating voids and anomalies in 3D-printed parts. However, its testing for battery applications has been limited.
ORNL researchers indicated isostatic pressing may also allow manufacturing the three battery layers as a single, dense system rather than creating them separately before joining them.
In the ACS Energy Letters paper, Dixit’s team stressed the importance of pursuing a solid-state battery that can be scaled up for manufacturing.
ORNL researchers are continuing to conduct tests to learn which pressing temperature and pressure combinations work best with different materials, and how those factors affect texture.
Isostatic pressing can alter texture—the question is whether it can actively control it. The ability to manipulate crystal texture would have significant benefits for solid-state batteries.—Marm Dixit
Other contributors include ORNL’s Ruhul Amin, Nitin Muralidharan, Rachid Essehli, Mahalingam Balasubramanian and Ilias Belharouak. ORNL’s research was sponsored by the DOE Office of Energy Efficiency and Renewable Energy Vehicle Technologies Office and made use of two DOE Office of Science user facilities, the Center for Nanophase Materials Sciences at ORNL and the Advanced Photon Source at Argonne National Laboratory.
Marm Dixit, Chad Beamer, Ruhul Amin, James Shipley, Richard Eklund, Nitin Muralidharan, Lisa Lindqvist, Anton Fritz, Rachid Essehli, Mahalingam Balasubramanian, and Ilias Belharouak (2022) “The Role of Isostatic Pressing in Large-Scale Production of Solid-State Batteries” ACS Energy Letters doi: 10.1021/acsenergylett.2c01936