Faculty Spotlight: Feng Lin

A global push to end the use of gasoline-powered cars in the coming decades has created a rat race amongst the auto industry to develop dependable electric vehicles.    

Given the scrutiny placed upon it, Tesla has emerged as one of the clubhouse leaders, but many companies and countries have laid out plans for battery-powered automobiles. How fast these cars develop will largely depend on the technological advancements of their batteries, and in a wider sense, the area of electrochemical energy storage.

This is the expertise and one of the research interests of Feng Lin, an assistant professor in the Department of Chemistry in the College of Science, as well as a new affiliated faculty member of MII.

Although car batteries are one of the most popular areas of energy storage, Lin said there's a much wider application and broader need for improved energy storage. As communities rely more on cleaner, renewable energy sources, batteries will be needed to fill in the gaps, such as at night when there's no available solar energy.

"Electrochemical energy storage is an interesting topic because it's not competing with any energy harvesting method," Lin said. "It's just a way to store energy into batteries and deliver it wherever and whenever it's needed."

Lin and his lab mainly work on two types of batteries: lithium-ion and sodium-ion. Lithium-ion batteries are known for their use in consumer electronics and electric vehicles. However, Lin sees significant challenges for automobile mass production.

For one, lithium is expensive and resource-limited. Sodium, on the other hand, is cheaper, more abundant, and has similar properties as lithium, so sodium-ion batteries could be a longer-term alternative. However, breakthroughs are needed to increase the energy density of sodium-ion batteries, and Lin said the future market will likely be occupied by many types of batteries targeted for different applications.

Additionally, lithium-ion batteries present significant safety challenges. Consumer electronics and electric vehicles have caught on fire because of the flammable liquid electrolyte stored inside. Lin is looking at the viability of replacing liquid electrolytes with high performance solid-state electrolytes.

"One pathway we have is using polymers, which are not flammable and provide reasonable conductivity for ions," Lin said. "We also work with ceramic membranes to form composites."

Lin began his work in battery research as a postdoc at Lawrence Berkeley National Laboratory after completing his Ph.D. thesis on smart windows at Colorado School of Mines and National Renewable Energy Laboratory. He was attracted to the field because of the excitement around it and its potential to reshape the energy landscape.

"German, Japanese, and U.S. auto companies have dominated the gasoline vehicle technologies market," Lin said. "But electric vehicles can potentially put everybody on the same starting line again.

"Some countries put down 2025 as the goal to terminate the production or sale of gasoline vehicles, but realistically, it's only seven years away. I think there are tremendous challenges along the way. However, we should always have hope. I'd say the shift will happen over the next 20 years. Scientists, engineers, industries, and governments will have to work together to accelerate the pace."

Lin always had his sights set on academia, but he took a one-year break after Berkeley to work in industry before joining the Virginia Tech faculty in 2016.

"I worked with experts in different aspects of the battery technology in the industry," Lin said. "Batteries are very application-oriented and you really need to learn what the market needs. My philosophy for batteries has been that we should focus on the fundamental challenges while keeping our work relevant to real-world applications."

After a year and a half in Blacksburg, Lin saw opportunities to advance his battery work through the science and engineering collaborations available through MII.

"Polymers are largely used at all levels in a battery system, but our group usually uses commercial polymers," Lin said. "We have already started exploring polymers with MII faculty members Louis Madsen and Michael Schulz – their groups will design high-voltage, stable polymers, and we can use them in our batteries to increase energy density and safety."

From the engineering side, Lin envisions tapping into the 3-D printing expertise of MII to find ways to change the architecture of batteries.

"Batteries aren't just for electric vehicles," Lin said. "Technologies are evolving; more applications will need batteries. It's hard to predict their limits. You can make them large enough to store energy from a power plant, and you can make them small to power an electrical circuit."

Lin said he's excited to join MII, where the interdisciplinary research environment can expand the scope of energy storage research. Lin also feels the need to educate next-generation scientists and engineers in this field. He will teach a new course in the fall in the Department of Chemistry called "Fundamentals of Batteries."