Converting such an everyday waste product as sunflower seed shells in material for rechargeable batteries It's no longer just a striking idea, but a reality in the laboratories of the University of the Basque Country (UPV/EHU). A research team has demonstrated that this type of biomass can be used to manufacture key components for more sustainable batteries.
The project, led by Dr. Nekane Nieto Within the Solid State and Materials Group at the UPV/EHU, he has developed sodium-ion batteries that utilize residual biomass as the base for the anode. These batteries are not only rechargeable, but also They withstand approximately 1.000 charge and discharge cycles maintaining a storage capacity considered adequate for real-world applications.
Sodium-ion batteries to reduce dependence on lithium
Much of the interest in this work lies in the fact that it relies on sodium ion batteriesSodium-based technology has gained traction in recent years as an alternative to conventional lithium batteries. Sodium is much more abundant and cheaper than lithium, and its extraction is less associated with shortages or geopolitical tensions.
Currently, practically all the batteries that power electric vehicles and electronic devices Batteries used daily are lithium-ion. Their manufacture uses lithium, cobalt, nickel, and manganese, elements that are on the European Union's list of critical raw materials due to their limited availability and the environmental impact of their extraction.
The UPV/EHU group is precisely pursuing reduce dependence on those critical materials Developing sodium-based storage systems and using biomass as a carbon source. The idea is that future batteries will not only be energy efficient, but also more sustainable from a European environmental and economic perspective.
Batteries, in essence, are composed of a cathode (positive electrode), an anode (negative electrode) and an electrolyte which allows the movement of ions between both ends. This team's work has focused on the anode, seeking to replace conventional materials with carbons derived from organic waste that would otherwise end up in the trash.
From sunflower seed shells to the anode: how biomass is used
To find the best possible material, the research group has tested different types of residual biomass collected in the Basque CountryAmong the waste materials used are coffee grounds, plant stems, shrubs of invasive species, grape seeds and skins, corn cobs, or even compost obtained from municipal bio-waste.
All this waste is transformed into coals through heat treatment processesThis process yields a carbon-rich material with properties suitable for use as an anode in a battery. Once these carbons are prepared and characterized, they are tested in electrochemical cells to evaluate their storage capacity and stability through numerous charge and discharge cycles.
Among all the materials analyzed, the best results were obtained with the charcoal derived from sunflower seed shellsThese provide a structure that favors the insertion and extraction of sodium ions, allowing charges to move efficiently between the anode and cathode and generate a stable electric current.
The team has even assembled button-type batteries in which the carbon anode made from sunflower seed shells is combined with cathodes containing iron, titanium and/or vanadiumThese elements are not considered as critical as cobalt or nickel and can be used in smaller quantities. This completes a rechargeable cell where both the negative and positive electrodes are placed on relatively abundant materials.
Results: up to 1.000 charging cycles with reduced environmental impact
The prototypes manufactured using this approach have shown highly competitive performance in the laboratoryAccording to the team's data, button-type batteries with carbon anodes from sunflower seed shells are capable of storing an amount of energy suitable for their size and, in addition, can withstand around 1.000 charge and discharge cycles without drastically losing their capacity.
To assess the true scope of this development, the researchers have not limited themselves to measuring electrochemical parameters. They have also carried out a life cycle analysis to determine which anode and cathode combination offers the best balance between energy performance and environmental impact over the entire life of the battery.
In that analysis, different cathode options were compared, always with the premise of choosing chemicals that are as environmentally friendly as possibleCompositions based on iron, titanium, or vanadium have made it possible to reduce the use of critical elements while maintaining performance levels considered satisfactory for specific applications.
The conclusion of this work is that it is rechargeable batteries made from sunflower seed shells and other biomass waste that can be integrated into real solutions, especially where such a high energy density as that offered by the lithium batteries that dominate the market today is not required.
Applications, current limitations, and next steps in the research
Despite the positive results in terms of life cycles and the use of less critical materials, the study's authors themselves emphasize that These sodium-ion batteries still do not match the overall performance of lithium batteries.The energy density remains lower, which limits its use in areas such as electric vehicles, where space and weight are crucial.
At the moment, the most realistic use envisioned for these cells is as complementary system or in smaller devicesThey could be used in triboelectric sensors, small electronic devices or stationary systems where sustainability and cost take precedence over maximum energy density.
The investigation continues for scale the technology to higher capacity batteries and to optimize both the biomass carbon production process and the electrode formulations. The medium-term goal is to develop systems that can compete with commercial solutions in specific segments, while remaining focused on reducing environmental impact.
This work also emphasizes the importance of explore alternatives to established technologiesThe University of the Basque Country (UPV/EHU) insists that it is not enough to improve existing batteries; it is necessary to open alternative lines that allow the use of organic waste and adapt to different applications, so that the industry has a wider range of storage options in the future.
Basque research focused on circular economy
Beyond the technical details, the project fits perfectly into the logic of the circular economy and the use of local resourcesUsing sunflower seed shells, coffee grounds or agricultural waste from the Basque Country as a base to manufacture high value-added materials means giving a second life to waste that usually ends up in landfills or in lower value waste management processes.
The initiative is part of the doctoral thesis of Nekane Nieto ÁlvaroDeveloped within the Solid State and Materials Group under the supervision of Professor Verónica Palomares Durán and Professor Teófilo Rojo Aparicio, some of the work has been carried out in collaboration with the SUPREN group at the Bilbao School of Engineering, reinforcing the multidisciplinary nature of the project within the Basque scientific ecosystem.
From a European perspective, these types of developments fit with the objectives of reduce the use of critical raw materials and move towards cleaner technologies in the field of energy storage. The possibility of manufacturing batteries with materials obtained a few kilometers from where they will be used adds a strategic component of resource sovereignty.
Ultimately, the work of the UPV/EHU shows that it is possible manufacture storage devices from organic waste without completely sacrificing competitive performance. Although these batteries are still far from replacing lithium batteries in all uses, they point towards a model in which some of the energy we consume can depend on recovered and local materials, reducing environmental costs and opening up new opportunities for innovation in Europe.
