Scientists have developed a novel method of using fruit peel waste to extract and reuse metals from spent lithium-ion batteries in order to create new batteries. The team demonstrated the concept using orange peel, which efficiently recovered precious metals from battery waste. They then made functional batteries from these recovered metals, creating minimal waste in the process.
The waste-to-resource approach tackles both food waste and electronics waste, supporting the development of a circular economy with zero waste in which resources are kept in use for as long as possible. Spent batteries are conventionally treated with extreme heat (over 500 °C) to smelt valuable metals, which emits hazardous toxic gases. Alternative approaches that use strong acid solutions or weaker acid solutions with hydrogen peroxide to extract the metals are being explored but they still produce secondary pollutants that pose health and safety risks or rely on hydrogen peroxide, which is hazardous and unstable.
With industrial approaches to recycling battery waste generating harmful pollutants, hydrometallurgy — using water as a solvent for extraction — is increasingly being explored as a possible alternative. This process involves first shredding and crushing used batteries to form a crushed material called black mass. Researchers then extract valuable metals from black mass by dissolving it in a mix of strong acids or weak acids plus other chemicals like hydrogen peroxide under heat before letting the metals precipitate. While relatively more eco-friendly than conventional methods, the use of such strong chemicals on an industrial scale could generate a substantial amount of secondary pollutants, posing significant safety and health risks.
The combination of orange peel that has been oven-dried and ground into powder and citric acid — a weak organic acid found in citrus fruits — can achieve the same goal. In lab experiments, the team found that their approach successfully extracted around 90 percent of cobalt, lithium, nickel, and manganese from spent lithium-ion batteries — a comparable efficacy to the approach using hydrogen peroxide.
The key lies in the cellulose found in orange peel, which is converted into sugars under heat during the extraction process. These sugars enhance the recovery of metals from battery waste. Naturally occurring antioxidants found in orange peel, such as flavonoids and phenolic acids, could have contributed to this enhancement as well. Solid residues generated from this process were found to be non-toxic, suggesting that this method is environmentally sound.
From the recovered materials, they then assembled new lithium-ion batteries, which showed a similar charge capacity to commercial ones. Further research is underway to optimize the charge-discharge cycling performance of these new batteries made from recovered materials. The team is now looking to further improve the performance of the batteries generated from treated battery waste. They are also optimizing the conditions to scale up production and exploring the possibility of removing the use of acids in the process.
The waste-to-resource approach could also potentially be extended to other types of cellulose-rich fruit and vegetable waste as well as lithium-ion battery types such