She checked out apples, rice husks and bitter gourd. But the Chinese eggplant became an early front runner.
"It's very porous, which suggests a high surface area to volume ratio," she said.
By using eggplant, or brinjal, to create more durable, cheaper and environmentally friendly batteries, Shannon Lee has made Singapore history. The 17-year-old is the first Singaporean to win a top prize at the annual Intel International Science and Engineering Fair, sometimes called the Olympics of the science calendar.
The National Junior College (NJC) Year 6 student beat close to 1,800 students from around the world this month. "Her research may significantly improve batteries of the future and may have a wide range of applications, such as improving the energy performance of hybrid vehicles," read her award's citation.
"My jaw dropped," she told The Straits Times last week. "It was my first time at the fair."
The fair is the world's largest pre-college science competition. It is organised by the non-profit, US-based Society for Science and the Public and is supported by computer giant Intel.
Students from more than 70 countries competed in this year's edition, held earlier this month in Los Angeles in the United States.
Shannon's project won her three awards, including US$58,000 (S$72,700) for higher education and the Intel Foundation Young Scientist Award, the fair's second-most prestigious honour.
The top prize, the Gordon E. Moore Award, went to US student Nathan Han, 15, for developing a computer programme that studies gene mutations linked to breast and ovarian cancer.
Shannon said she started thinking about batteries as part of an NJC programme allowing students to work with an institution on a research project.
"There is a lot of interest and excitement around the world about electric and hybrid cars, so I thought, how can I make the batteries better?" she said.
After getting advice from her mentors at the Agency for Science, Technology and Research's Institute of Materials Research and Engineering (IMRE), she focused on finding a substitute from nature for a battery component.
Researchers have sought to improve metal-air batteries as a replacement for the conventional lithium-ion battery found in many electronic devices.
Metal-air batteries use oxygen as a key component, and so are lighter and safer, but suffer from poor durability and high cost.
Shannon focused on zinc-air batteries. "I looked at different plants and vegetables that could act as a suitable conductive material for the air cathode of the batteries," she said.
She discovered that freeze- dried, burnt eggplant could act as a catalyst for a reaction at the battery's cathode. This led her to develop carbonised eggplant as a replacement for a much more expensive and less durable material. "I used so many eggplants I lost count. I think the supermarket I went to loves me now," she said.
"She was here almost every day during her school holidays," said Dr Li Bing, her mentor at IMRE. "We gave her a general research direction and some advice but we didn't need to offer much.
"She was dedicated, independent and had good practical, hands-on skills."
But for now, Shannon has more pressing concerns.
"I have not even had time to celebrate because I am taking my common tests now," she said with a laugh. "Let me get through my exams first."
This article was first published on May 26, 2014.
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