Periodic Reporting for period 2 - ECO2LIB (Ecologically and Economically viable Production and Recycling of Lithium-Ion Batteries)
Berichtszeitraum: 2022-01-01 bis 2022-12-31
Green energy without CO2 emissions is a key element of adapting to the effects of climate change. However, clean and renewable power sources such as solar, wind or hydropower are subjected to meteorological effects and thus can be very fluctuant with regards to energy production. Undoubtedly, rechargeable batteries are hence the technology of choice to store excess energy and compensate for these instabilities in production. Stationary electrical energy storage devices will unlock the full capacity of clean energy and a non-intermittent delivery of electricity from the point of generation to the point of use. To enable the widespread distribution of battery-based energy storage systems, they have to become more sustainable and affordable for the broad majority. ECO2LIB thus focuses on the ecologically and economically viable production and recycling of Lithium-Ion Batteries for non-automotive applications. The overall target is the development of improved battery materials with significantly reduced costs per cycle (€/kWh/cycle). This will help the market penetration of the technology.
During the third year of the project, a modified 3D copper current collector has been upgraded to produce larger samples by electrodeposition on bare foils. University Warsaw paid attention to the oxidation of the material leading to better adhesion or homogeneity of the material. However, this micro/nano structure has still low mechanical stability.
Supplemental fluorine-free liquid electrolytes with updated formulation or specific formation protocols were tested but they do not lead to long cycle life with graphite silicon anode containing 25% of micrometric scale silicon. In parallel, gel electrolytes were tested based on synthesis by polymerization of two components which should combine continuous ion-conducting pathways through a mechanically robust cross-linked matrix. The ionic conductivities of the resulting electrolytes are still below 0.1 mS.cm-1. The results are under submission as an article in Electrochimica Acta.
On the cathode side, the green aqueous NMC622 manufacturing process is performed with the same capacity retention level as the standard one using NMP solvent. Specific attention has to be paid to the final drying step as water-soluble binders are more hydrophilic while having also better temperature stability allowing finally the same residual water content in the cathode. This result was obtained by integrating a specific acid to stabilize the slurry and to be compliant with the aluminum foil, with a negligible supplemental thickness impact of around 0.3% on the final electrode.
On the anode side, a second electrode generation with an amount of 50w% Si was produced and characterized. It was possible to achieve the targeted cycle life of 70% capacity retention after 300 cycles (100% DOD) at lab scale. Moreover, a next-generation silicon material was introduced and tested. With this material, a capacity retention of 80% after 600 cycles was achieved at lab scale. In addition, anodes with a higher Si content (70w%) were developed and extensively characterized.
The developed electrodes, electrolytes, and battery cells have been characterized in their pristine and aged states, using the multi-technique ECO2LIB approach to correlate (electro)chemical, structural and morphological information at multiple length scales. The composite nature of the anodes, which contain a large amount of silicon, induces SEI formation and structural variations along with cycling, both strongly dependent on the nature of electrolytes and binders, and affecting electrochemical performances. Non-fluorine electrolytes result in a stable, continuously growing solid electrolyte interphase. The capacity drop during cycling is mainly driven by SEI formation and lithium concentration inhomogeneities, which develop at particle, electrode, and cell scales, producing a range of defective regions, from altered buried interfaces to macroscale cell deformations.
The aqueous-based mechanical separation process was tested by 2 different types of cells (portable cells and EV cells). The process successfully separated the fine fraction (active material) and the coarse fraction (casing, foils, separators). The yield of the fine fraction, however, was lower than expected. This is due to the presence of PVDF as cathode binder in the tested cells, which shall be improved to an aqueous binder in next-generation ECO2LIB cells. The electrolyte-containing solution during mechanical separation was also investigated to purify the electrolyte solvent. The results showed that the purity of the products is not good enough to be used again in battery production. Therefore, these organic components can only be used in other applications.
Data gathering and ecological screening of ECO2LIB activities are still ongoing, whereas the focus within the second reporting period was on the assessment of gel polymer electrolytes and water-based electrode production. Within the LCA software, the life cycle inventory modeling of state-of-the-art recycling processes (already established in the first reporting period) was extended by economic flows. Economic information and costs of plants, equipment, etc. were started to collect - for recycling, but for conventional electrode production (using NMP) as well.
Supplemental fluorine-free liquid electrolytes with updated formulation or specific formation protocols were tested but they do not lead to long cycle life with graphite silicon anode containing 25% of micrometric scale silicon. In parallel, gel electrolytes were tested based on synthesis by polymerization of two components which should combine continuous ion-conducting pathways through a mechanically robust cross-linked matrix. The ionic conductivities of the resulting electrolytes are still below 0.1 mS.cm-1. The results are under submission as an article in Electrochimica Acta.
On the cathode side, the green aqueous NMC622 manufacturing process is performed with the same capacity retention level as the standard one using NMP solvent. Specific attention has to be paid to the final drying step as water-soluble binders are more hydrophilic while having also better temperature stability allowing finally the same residual water content in the cathode. This result was obtained by integrating a specific acid to stabilize the slurry and to be compliant with the aluminum foil, with a negligible supplemental thickness impact of around 0.3% on the final electrode.
On the anode side, a second electrode generation with an amount of 50w% Si was produced and characterized. It was possible to achieve the targeted cycle life of 70% capacity retention after 300 cycles (100% DOD) at lab scale. Moreover, a next-generation silicon material was introduced and tested. With this material, a capacity retention of 80% after 600 cycles was achieved at lab scale. In addition, anodes with a higher Si content (70w%) were developed and extensively characterized.
The developed electrodes, electrolytes, and battery cells have been characterized in their pristine and aged states, using the multi-technique ECO2LIB approach to correlate (electro)chemical, structural and morphological information at multiple length scales. The composite nature of the anodes, which contain a large amount of silicon, induces SEI formation and structural variations along with cycling, both strongly dependent on the nature of electrolytes and binders, and affecting electrochemical performances. Non-fluorine electrolytes result in a stable, continuously growing solid electrolyte interphase. The capacity drop during cycling is mainly driven by SEI formation and lithium concentration inhomogeneities, which develop at particle, electrode, and cell scales, producing a range of defective regions, from altered buried interfaces to macroscale cell deformations.
The aqueous-based mechanical separation process was tested by 2 different types of cells (portable cells and EV cells). The process successfully separated the fine fraction (active material) and the coarse fraction (casing, foils, separators). The yield of the fine fraction, however, was lower than expected. This is due to the presence of PVDF as cathode binder in the tested cells, which shall be improved to an aqueous binder in next-generation ECO2LIB cells. The electrolyte-containing solution during mechanical separation was also investigated to purify the electrolyte solvent. The results showed that the purity of the products is not good enough to be used again in battery production. Therefore, these organic components can only be used in other applications.
Data gathering and ecological screening of ECO2LIB activities are still ongoing, whereas the focus within the second reporting period was on the assessment of gel polymer electrolytes and water-based electrode production. Within the LCA software, the life cycle inventory modeling of state-of-the-art recycling processes (already established in the first reporting period) was extended by economic flows. Economic information and costs of plants, equipment, etc. were started to collect - for recycling, but for conventional electrode production (using NMP) as well.
From a sustainability perspective, the progress beyond the state-of-the-art is an aqueous-based recycling process that saves a lot of energy as well as CO2 emissions. This dedicated recycling process will then be validated at a larger scale when the ECO2LIB cell is successfully developed after the end of the project.
The project aims at a systematic assessment of the entire life cycle of the project ECO2LIB, taking into account environmental as well as economic aspects, allowing the identification of key drivers of sustainability, optimisation potentials, deduction of recommendations as well comparison to state-of-the-art technologies to evaluate the competitiveness of ECO2LIB approaches. This will be realized by thorough LCA assessment according to DIN EN ISO 14040/14044 as well as Life Cycle Costing. ECO2LIB will then be able to give a contribution to sustainable and competitive battery production and recycling systems and value chains in the European Union. This will not only have an impact on the industry and the environment but also on the socio-economic impact in Europe.
The project aims at a systematic assessment of the entire life cycle of the project ECO2LIB, taking into account environmental as well as economic aspects, allowing the identification of key drivers of sustainability, optimisation potentials, deduction of recommendations as well comparison to state-of-the-art technologies to evaluate the competitiveness of ECO2LIB approaches. This will be realized by thorough LCA assessment according to DIN EN ISO 14040/14044 as well as Life Cycle Costing. ECO2LIB will then be able to give a contribution to sustainable and competitive battery production and recycling systems and value chains in the European Union. This will not only have an impact on the industry and the environment but also on the socio-economic impact in Europe.