To understand where the field of ceramics in electronics is headed, you have to think small—really small, as in thicknesses that measure only a few hundred nanometers.
Micro-sized ceramics already play a key role in the functioning of common products, such as computers, smartphones, automotive electronic controls and sensors, televisions and medical devices.
But new, smaller-scale ceramic thin films are destined to have an even bigger impact. In addition to the electronics just mentioned, they can be used in a variety of different applications, including alternative energy storage via solid-state batteries and solar-to-synthetic fuel conversion to novel types of devices for neuromorphic computing, artificial intelligence and the tracking of chemicals in the environment.
Developing smaller-scale ceramic thin films for these new applications will require overcoming several significant hurdles. For example, large-scale integration of solid-state batteries is dependent on being able to assemble battery materials at the lowest possible processing temperature while keeping lithium conduction high. However, integrating ceramic film electrolytes while keeping a high lithium concentration and conduction at a low processing temperature has proven quite challenging.
We have been working to solve this problem in my lab and recently developed an innovative method to produce a ceramic thin film that is lithium rich and only about 330 nanometers thick. Here, we report an alternative ceramic processing strategy through the evolution of multilayers establishing lithium reservoirs directly in lithium–garnet films that allow for lithiated and fast-conducting cubic solid-state battery electrolytes at unusually low processing temperatures.
This technique reduces the processing temperature by hundreds of degrees while creating a ceramic thin film with a high concentration of lithium. The new material maintains a high level of conductivity. The ceramic thin film we produced showed the fastest ionic conductivity yet for a lithium-based electrolyte compound. For this, a lithium–garnet film processed via the multilayer processing approach exhibited the fastest ionic conductivity of 2.9 ± 0.05 × 10−5 S cm−1 (at room temperature) and the desired cubic phase but was stabilized at a processing temperature lowered by 400 °C.
This method enables future solid- state battery architectures with more room for cathode volumes by design, and reduces the processing temperature.
Much more testing needs to be done, but we are hopeful that this new processing method will allow for the development of thinner, solid ceramic electrolytes, which in turn could lead to improvements in batteries for electric cars.
Replacing the flammable liquid organic solvents used as electrolytes in conventional lithium batteries with non-flammable solid ceramic electrolytes would make batteries safer. Plus, a ceramic electrolyte could make electric car batteries lighter, faster to charge, longer lasting, and more durable.
Beyond applications for electric car batteries, this new ceramic thin film processing technique could be used in other areas where lithium-rich, solid-state materials can be used to trigger electrochemical processes. Of particular interest to me are nanofabricated structures and small-system structures for devices that can store and convert energy, compute information, or sense carbon dioxide or various environmental pollutants.
Applications like these will become increasingly important as we transition to a low-carbon energy future.