Every year, more than 500 billion plastic water bottles are produced worldwide, most of them used only once before being thrown away.
Now, scientists have discovered an innovative way to give this waste a second life—by transforming old bottles into high-performance supercapacitors, devices that can store and release energy quickly and efficiently.
The research, published in Energy & Fuels, was led by Professor Yun Hang Hu and his team.
They developed new heat-based techniques to upcycle plastic bottles made of polyethylene terephthalate (PET) into key components for an all-plastic supercapacitor.
Their results show that the upcycled device performed as well—or even slightly better—than similar supercapacitors made with traditional materials.
“PET-derived supercapacitors hold great potential for a wide range of applications, from transportation and electronics to industrial systems,” said Hu.
“This approach helps solve the plastic waste problem while producing sustainable, low-cost energy storage devices.”
Supercapacitors are energy storage devices that can charge and discharge much faster than batteries.
They are especially useful in electric vehicles, renewable energy systems, and portable electronics, where quick bursts of power are needed.
Typically, these devices use carbon-based electrodes separated by a thin layer called a separator, all immersed in a liquid that allows electrical charge to move between the electrodes.
Hu’s team found a way to make both the electrodes and the separator from recycled PET bottles.
To create the electrodes, the researchers shredded the bottles into tiny grains and mixed them with calcium hydroxide.
They then heated the mixture to about 700°C (1300°F) in a vacuum. This process converted the plastic into a porous, electrically conductive carbon material. The team combined this carbon powder with other materials to make thin, flexible electrode layers.
For the separator, the scientists flattened small pieces of PET plastic and carefully poked tiny holes in them with heated needles.
The pattern of holes allowed ions to move smoothly through the liquid inside the supercapacitor, improving its performance.
When the team assembled the complete PET-based supercapacitor, it performed impressively.
It retained 79% of its energy storage capacity over time, slightly outperforming a similar device that used a standard glass fiber separator, which retained 78%. The all-plastic design also made the supercapacitor cheaper to produce and easier to recycle.
According to Hu, the next step is to refine the process and test the devices on a larger scale. “With further optimization, PET-derived supercapacitors could move from lab prototypes to commercial products within the next five to ten years,” he said.
If successful, this technology could turn one of the world’s biggest sources of plastic pollution into a valuable resource—helping power a cleaner, more sustainable future.
