Meet the Researcher: Sean Doris Explores How Printed Electronics Can Help Improve Battery Performance
Sean Doris‘ research interests are rooted in the applications of materials chemistry and electrochemistry. As a member of PARC’s Electronic Materials and Devices Laboratory, he is working to develop materials and processes that enable next-generation Printed Electronics.
PARC recently showcased its Cleanroom services and expertise in Printed Electronics at the IDTechEx Show in Santa Clara, California. We sat down with PARC researcher, Sean Doris, to learn more about his work in this area.
Sean, please tell us about your work at PARC.
I’ve been working at PARC since 2017 in the Printed Electronics group under Bob Street. Printed Electronics has been kicked around for a while for various applications, ranging from smart packaging to flexible displays. My background is in electrochemistry, so I’ve been exploring applications of Printed Electronics in electrochemical systems as well as investigating how electrochemistry can extend the capabilities of Printed Electronics.
How would you describe Printed Electronics?
Transistors are the building blocks for many different types of electronics. The conventional means of making transistors is a Cleanroom top-down approach where you deposit layers of material and pattern it using photolithography. You can build multiple layers and produce very small transistors and integrated circuits with this approach.
Printed Electronics is more of a bottom-up approach where you deposit materials with the properties that you want using a printing process. It can be much simpler and more cost effective than the conventional top-down lithography approach, particularly if you’re making something very big. For example, if you need electronics spread over a very large area such as in a display, Printed Electronics has the potential to excel. When I started working at PARC, I realized that batteries are a great example of a large-area system where it could be useful to have control of how current moves within the system. Hence, I’ve been looking at Printed Electronics approaches for doing this.
How do you use Printed Electronics to control the flow of current across a battery?
The best way to explain is to first look at the components of a typical lithium-ion battery cell. It consists of two thin metal foil current-collectors (typically aluminum and copper) that are each coated with a layer of active material that stores the charge. There is a separator between the two electrodes that houses the electrolyte, which allows the flow of ions between the two electrodes. By printing a layer of transistors onto one or both current-collectors, the current flowing between the current-collector and the active material can be controlled at the individual battery cell level. In recent years, PARC has acquired a great deal of expertise with a new class of transistors that are ideal for this application.
Battery manufacturers and users understand that there is some variability between cells. Therefore, when individual cells are combined into larger battery packs, sophisticated electronics can be included that can control how current flows within the battery pack to account for this variability. However, once you get down to the cell level, there’s no control over how current flows within an individual cell using existing technologies. This is the gap that we’re trying to fill with Printed Electronics.
Why is it beneficial to control current flow at the individual battery cell level? What are some applications for this?
One major benefit is to enhance battery safety during internal short-circuits. When batteries are compressed, punctured or otherwise damaged, electrodes can become deformed and come into contact internally – causing an internal short circuit. Consequently, the cell will rapidly discharge through the short circuit and heat up until it enters thermal runaway, a process which releases enormous amounts of heat and can potentially cause a fire. If you’re designing something like an electric vehicle that uses a lot of battery cells, you have to be careful to design the vehicle so that the batteries are protected from damage during impact in order to avoid this catastrophic failure mode. If we can control the way current flows within an individual cell, we can convert the short circuit into a graceful failure mode – meaning the cell will still discharge, but it will discharge slowly enough that the cell doesn’t enter thermal runaway. This gives battery users more flexibility to use batteries in areas that would otherwise be considered too risky, and provides a greater safety margin for using batteries in applications where safety is critical.
In addition to enhancing safety, controlling the current at the individual battery cell level has the potential to improve battery lifetime and charging rate. Since there will inevitably be some variability within individual battery cells, rapid charging can damage the “weaker” portions of the cell. By controlling current at the individual battery cell level, we can allow each portion of the battery to charge as quickly as possible without damaging other parts of the cell.
What other advancements or applications do you envision for Printed Electronics over the next few years?
I think Printed Electronics will start to play a key role in the area of ubiquitous sensing, as there will be an increased demand for low-cost printed sensors for applications like integrating sensors and electronics with 3D objects (i.e., functional 3D printing). I also think we’ll see a shift towards disposable bio-degradable sensors which cannot be easily supported by conventional electronics, and thus presents an opportunity for Printed Electronics.
What do you enjoy most about working at PARC?
I think PARC has established a unique culture in which researchers work in a very collaborative and supportive environment where we all reap the benefits of our work. I also like the fact that I’m not tied to one specific project or one particular specialty. I have the opportunity to work on many different projects and learn about different disciplines that I can use to help advance my own research.
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