A plastic bottle tossed into a recycling bin could one day help power an electric vehicle, smartphone or renewable energy storage system, according to a team of Penn State researchers.
In a new study, researchers converted waste polyethylene terephthalate, or PET, into highly ordered synthetic graphite, a crystalline form of carbon. The formed graphite exhibited large, well-ordered crystallites - or microscopic regions of well-aligned carbon layers - indicating a highly organized crystal structure. These properties exceeded those of commercial natural graphite samples, indicating that the PET-derived material had a more ordered crystal structure. Such structural ordering is a key indicator of suitability for high‑quality anode materials when compared to natural graphite commonly used as a benchmark in battery research.
The findings, published in Diamond and Related Materials, suggest that a common waste material could become a valuable source of battery-grade carbon.
"Most people think of a plastic bottle as waste once they're done using it," said Shakshi Sekar, lead author of the study and a doctoral student in Penn State's John and Willie Leone Family Department of Energy and Mineral Engineering. "Our work shows that the same material can become a valuable resource for producing graphite, which is essential for modern battery technologies."
Classified as a critical mineral by the U.S. Department of Energy, graphite is an integral component of lithium-ion batteries, serving as the anode material that stores and releases electrical charges. As demand for electric vehicles, consumer electronics and grid-scale energy storage systems continue to grow, so does demand for battery-grade graphite.
At the same time, PET remains one of the most widely used plastics in the world, according to the National Association for PET Container Resources. Although many consumers place plastic bottles in recycling bins, much of that material is ultimately discarded, downcycled into lower-value products or sent to landfills.
The research team said they saw an opportunity to address both challenges.
By combining shredded PET plastic with small amounts of graphene oxide and heating the material through a carefully controlled thermal process, the team was able to reorganize carbon atoms within the plastic into highly ordered graphitic structures.
"We're not simply finding a use for waste plastic," Sekar said. "We're creating a valuable material that could help support the growing demand for batteries and clean energy technologies."
The researchers found that adding just 2.5% graphene oxide by weight produced the highest-quality graphite. Under those conditions, the material developed crystallite dimensions that exceeded those associated with natural graphite, indicating an exceptional degree of structural order.
According to the researchers, oxygen-containing functional groups located along the edges of graphene oxide sheets help initiate and promote lateral graphite crystal growth. The exposed graphene surfaces act as templates that guide carbon atoms into highly organized stacked arrangements during graphitization, the process of transforming carbon into graphite.
The team's approach differs from many previous methods used to produce synthetic graphite. Common graphitization techniques often rely on metal catalysts such as iron, nickel or cobalt, which can leave behind impurities that require additional chemical purification steps to be removed.
Instead, these researchers used graphene-based additives that promote graphitization without introducing metallic contaminants.
"By avoiding metal catalysts, we can produce cleaner graphite while reducing chemical use and waste generation," Sekar said.
Eliminating catalyst removal steps could simplify future manufacturing and reduce the environmental footprint associated with producing battery materials, the researchers said.
While additional work is needed to evaluate large-scale production and battery performance, the study demonstrates a promising pathway for transforming one of the world's most common waste streams into a high-value energy storage material.
The findings also point to a broader shift in how plastic waste could be viewed in the future, Sekar noted.
"If waste plastic can become a feedstock for advanced energy materials, it changes how we think about recycling," Sekar said. "Instead of viewing plastic as a disposal problem, we can see it as a resource that helps support clean energy technologies."
Other authors on the study include Randy Vander Wal, professor of energy and mineral engineering at Penn State and faculty member in Penn State's Institute of Energy and the Environment.
The research was supported by the U.S. National Science Foundation.
