Periodic Reporting for period 3 - ECO2LIB (Ecologically and Economically viable Production and Recycling of Lithium-Ion Batteries)
Período documentado: 2023-01-01 hasta 2024-06-30
Green energy without CO2 emissions is crucial for adapting to climate change. Clean, renewable sources like solar, wind, and hydropower are affected by meteorological conditions, leading to fluctuating energy production. Rechargeable batteries are essential to store excess energy and stabilize production. To enable widespread adoption of battery-based storage systems, they must become more sustainable and affordable. ECO2LIB focuses on the ecological and economic production and recycling of Lithium-Ion Batteries for non-automotive applications, aiming to develop improved battery materials with reduced costs per cycle (€/kWh/cycle), enhancing market penetration.
We developed a fast and scalable method to improve 3D current collectors for negative electrodes in lithium-ion batteries. When covered with a silicon-based coating, these electrodes showed excellent performance, with only a small capacity loss of 0.2% per cycle—much better than standard electrodes. However, the cost to implement this technology in production is beyond the project's budget.
We also created polycarbonate formulations for gel electrolytes, which were applied to the battery's anode and cathode layers. Unfortunately, the lab-scale cells were not stable enough, so further improvements are necessary.
On the positive side, we successfully tested a more eco-friendly manufacturing process for the cathode, which uses water instead of the harmful NMP solvent. This green process worked just as well as the traditional method, but the final drying step needs special attention because the water-based binders tend to absorb moisture. However, these binders also perform better at high temperatures. We achieved the same moisture level in the final cathode by adding a small amount of acid, which didn’t affect the thickness of the electrode. While production on a pilot line has been confirmed, larger-scale manufacturing will require longer processing times.
On the anode side, we developed electrodes with 70% silicon content, using next-generation materials on a mass-production scale. These anodes retained 70% of their capacity after 1,000 charge cycles in full cells. The manufacturing process was scaled up for larger battery formats, like the 21700 type, achieving an energy density of 800 Wh/L. By the end of the project, we had produced 261 of these large cells to build a home energy storage module.
We thoroughly tested the new electrodes, electrolytes, and battery cells, both when they were new and after use, using the multi-technique ECO2LIB approach. We found that the high silicon content in the anodes led to the formation of a protective layer (SEI) on the surface, which changed over time and affected performance. Electrolytes without fluorine provided a more stable SEI, which continued to grow over time. The drop in capacity was mainly caused by the formation of this SEI layer and uneven lithium distribution, which led to defects and damage at the cell level.
We imaged the degradation heterogeneities at the cell level and obtained detailed 3D maps of trapped lithium and inactivated regions after long-term ageing. We found specific deformations and defects caused by silicon agglomeration during the slurry preparation and electrode manufacturing. We also discovered correlations between reaction kinetics, particle motions/volume changes, and fluid dynamics inside industry-grade cylindrical cells, providing key insights into complex chemomechanics during high silicon content battery charge and discharge.
We also developed multi-physics models to understand the effects of mixing silicon with graphite and the internal stresses in the battery. These models were tested with real data and simplified to predict how the battery's capacity would decrease over time. Additionally, we explored an eco-friendly process to recycle batteries, separating different materials. The process successfully separated fine and coarse fractions, but it didn't perform as well as expected due to a specific binder used in the tested cells. We recommend switching to an aqueous binder in future ECO2LIB cells. We also investigated ways to purify the electrolyte solution for reuse, but side reactions with water limited its use in battery production. Water is essential for safety, but the organic components from this process can be repurposed in other areas. In the end, we achieved a 76% battery recovery rate.
A Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) analysis compared ECO2LIB NMC622 lithium-ion cells to current NMC622 reference cells. Despite higher material costs, mainly due to the silicon anode and extra NMC622 oxide, ECO2LIB cells had comparable production costs per kWh due to a higher cell capacity and the employment of water as the cathode solvent, leading to the omission of cost-intensive NMP recovery. While the production of ECO2LIB cells has a higher environmental footprint, the improved energy density reduces the overall impact per kWh provided over the battery's lifetime. Compared to standard cells, ECO2LIB cells lower CO2 emissions by 10% and total costs by 3% over their lifetime. These calculations assume large-scale production and an equal number of cycles for both cell types, though long-term testing may be needed for confirmation. The same recycling rates were assumed for both the standard and ECO2LIB processes, which could be achieved if only aqueous binders are used in future batteries.
We also created polycarbonate formulations for gel electrolytes, which were applied to the battery's anode and cathode layers. Unfortunately, the lab-scale cells were not stable enough, so further improvements are necessary.
On the positive side, we successfully tested a more eco-friendly manufacturing process for the cathode, which uses water instead of the harmful NMP solvent. This green process worked just as well as the traditional method, but the final drying step needs special attention because the water-based binders tend to absorb moisture. However, these binders also perform better at high temperatures. We achieved the same moisture level in the final cathode by adding a small amount of acid, which didn’t affect the thickness of the electrode. While production on a pilot line has been confirmed, larger-scale manufacturing will require longer processing times.
On the anode side, we developed electrodes with 70% silicon content, using next-generation materials on a mass-production scale. These anodes retained 70% of their capacity after 1,000 charge cycles in full cells. The manufacturing process was scaled up for larger battery formats, like the 21700 type, achieving an energy density of 800 Wh/L. By the end of the project, we had produced 261 of these large cells to build a home energy storage module.
We thoroughly tested the new electrodes, electrolytes, and battery cells, both when they were new and after use, using the multi-technique ECO2LIB approach. We found that the high silicon content in the anodes led to the formation of a protective layer (SEI) on the surface, which changed over time and affected performance. Electrolytes without fluorine provided a more stable SEI, which continued to grow over time. The drop in capacity was mainly caused by the formation of this SEI layer and uneven lithium distribution, which led to defects and damage at the cell level.
We imaged the degradation heterogeneities at the cell level and obtained detailed 3D maps of trapped lithium and inactivated regions after long-term ageing. We found specific deformations and defects caused by silicon agglomeration during the slurry preparation and electrode manufacturing. We also discovered correlations between reaction kinetics, particle motions/volume changes, and fluid dynamics inside industry-grade cylindrical cells, providing key insights into complex chemomechanics during high silicon content battery charge and discharge.
We also developed multi-physics models to understand the effects of mixing silicon with graphite and the internal stresses in the battery. These models were tested with real data and simplified to predict how the battery's capacity would decrease over time. Additionally, we explored an eco-friendly process to recycle batteries, separating different materials. The process successfully separated fine and coarse fractions, but it didn't perform as well as expected due to a specific binder used in the tested cells. We recommend switching to an aqueous binder in future ECO2LIB cells. We also investigated ways to purify the electrolyte solution for reuse, but side reactions with water limited its use in battery production. Water is essential for safety, but the organic components from this process can be repurposed in other areas. In the end, we achieved a 76% battery recovery rate.
A Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) analysis compared ECO2LIB NMC622 lithium-ion cells to current NMC622 reference cells. Despite higher material costs, mainly due to the silicon anode and extra NMC622 oxide, ECO2LIB cells had comparable production costs per kWh due to a higher cell capacity and the employment of water as the cathode solvent, leading to the omission of cost-intensive NMP recovery. While the production of ECO2LIB cells has a higher environmental footprint, the improved energy density reduces the overall impact per kWh provided over the battery's lifetime. Compared to standard cells, ECO2LIB cells lower CO2 emissions by 10% and total costs by 3% over their lifetime. These calculations assume large-scale production and an equal number of cycles for both cell types, though long-term testing may be needed for confirmation. The same recycling rates were assumed for both the standard and ECO2LIB processes, which could be achieved if only aqueous binders are used in future batteries.
To the best of our knowledge, the ECO2LIB project is the first to provide data on the mass production of next-generation silicon-anode batteries within a funded project. These new batteries show a significant improvement, with over 40% more capacity and stability for 1,000 charge cycles, maintaining 70% of their original capacity at full charge and discharge. What’s notable is that this was achieved using a standard NMC622 cathode. These results make ECO2LIB an important step towards giving the European battery industry a technological edge.
The project’s use of an environmentally friendly process for making cathodes avoids toxic solvents like NMP, replacing them with PFAS-free binders. This water-based method, developed on a pilot scale, is a key step towards more sustainable and cost-effective battery production in Europe.
From a sustainability perspective, ECO2LIB also introduces an innovative water-based recycling process, which significantly reduces energy use and CO2 emissions. This recycling process will be further validated on a larger scale once the ECO2LIB battery is fully developed after the project’s completion.
The project also focuses on a comprehensive assessment of the entire battery life cycle, considering both environmental and economic factors. This helps identify key areas for improving sustainability and competitiveness, and provides recommendations for future advancements. The assessment follows rigorous standards (DIN EN ISO 14040/14044) for both environmental impact and life cycle costing. ECO2LIB aims to support sustainable and competitive battery production, recycling systems, and supply chains in the European Union. This will not only benefit the industry and the environment but will also have a positive socio-economic impact in Europe.
The project’s use of an environmentally friendly process for making cathodes avoids toxic solvents like NMP, replacing them with PFAS-free binders. This water-based method, developed on a pilot scale, is a key step towards more sustainable and cost-effective battery production in Europe.
From a sustainability perspective, ECO2LIB also introduces an innovative water-based recycling process, which significantly reduces energy use and CO2 emissions. This recycling process will be further validated on a larger scale once the ECO2LIB battery is fully developed after the project’s completion.
The project also focuses on a comprehensive assessment of the entire battery life cycle, considering both environmental and economic factors. This helps identify key areas for improving sustainability and competitiveness, and provides recommendations for future advancements. The assessment follows rigorous standards (DIN EN ISO 14040/14044) for both environmental impact and life cycle costing. ECO2LIB aims to support sustainable and competitive battery production, recycling systems, and supply chains in the European Union. This will not only benefit the industry and the environment but will also have a positive socio-economic impact in Europe.