Researchers have cooked up a technique to make battery materials that is about as easy as making instant ramen. They take plastic from single-use water bottles and put it in a good old kitchen microwave for two minutes.
It’s not quite as simple as that, of course, but it’s close. Purdue University chemical engineers started with polyethylene terephthalate (PET), the most commonly used plastic for packaging and containers. Even though global plastic recycling rates are very low, PET is the most recycled and recyclable plastic. But the recycled material is usually lower quality and hence of lower value than virgin plastics. Finding new uses for it such as chemicals and fuels, or a high-value battery material, could increase its recycling rate.
Breaking down PET into its chemical constituents for recycling typically involves harsh chemical reactions that use high temperature or pressure, long reaction times, and requires a catalyst.
The new method, presented in the journal ACS Sustainable Chemistry & Engineering, is much easier and faster. The researchers shredded PET bottles into tiny flakes, which they blasted with ultra-fast microwave radiation for two minutes using a household microwave.
This resulted in a compound called disodium terephthalate, which scientists have been investigating as a potential material for the negative electrodes, or anodes, in lithium-ion and sodium-ion batteries. Today’s batteries used graphite-and-copper anodes, but disodium terephthalate would be much cheaper and easier to make on a large scale since it can be produced from waste PET.
To make anodes, the researchers mix the disodium terephthalate with carbon black to make a composite. They tested anodes made with this composite in both lithium and sodium ion battery cells.
Source: Sourav Ghosh et al. Rapid Upcycling of Waste Polyethylene Terephthalate to Energy Storing Disodium Terephthalate Flowers with DFT Calculations. ACS Sustainable Chem. Eng. 2020.