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When it comes to recycling lithium-ion batteries (LiBs), safety and efficiency are paramount. Classified as hazardous waste under EU legislation, spent LiBs pose significant risks, primarily due to their state-of-the-art (SoA) non-aqueous electrolytes. This complex mixture, which includes conductive salts dissolved in organic solvents and additives, is flammable, volatile, and toxic. By their very nature, the uncontrolled release of these components can harm the environment and endanger workers in recycling plants. Additionally, electrolyte residues in LiB waste streams represent a financial burden for the recycling industry since they are still classified as hazardous waste. Therefore, safely recovering the electrolyte is crucial for developing a secure recycling process.

One promising alternative to traditional methods like vacuum vaporization is supercritical carbon dioxide (ScCO₂) extraction. The easily adjustable properties and excellent mass-transfer characteristics of ScCO₂ make it potentially ideal for selectively extracting electrolyte components from LiB waste, resulting in purified extraction products. Previous research has demonstrated that non-polar electrolyte solvents like dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) can be extracted using low-density CO₂.

Recent results reported by the research team at University of Chalmers (CHA)have shown that by gradually increasing pressure and temperature conditions, more polar electrolyte components such as ethylene carbonate (EC), and propylene carbonate (PC) can also be successfully extracted. However, selective extraction of solvents remains a challenge, requiring further thermodynamic and kinetic data to optimise the process.

Modelling the extraction behaviour allows the designing of an optimised extraction process that achieves high purity solvents. This high purity enables the recycling industry to either resell the solvents for other uses or even reuse them in battery production, making the process more sustainable and economically viable.

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There is an undeclared competition for better, more efficient batteries which pushes researchers to continue developing new methods for extracting and synthesising electrodic materials.

Recovery of lithium as battery grade material

Lithium (Li) is a key component in batteries and scientists involved in the RHINOCEROS Project have been exploring ways to extract it from recycled materials from used batteries known as “black mass” (BM). But one of the challenges scientists are facing is the reduction of fluoride content in extracted Li. Researchers at KIT tested their mechanochemical process for extracting Li from various BM samples provided by partners ACC and TES. Their experiments engaging reactive milling coupled with various reactive agents aimed to reduce the fluoride content of the aqueous solution. These tests showed that using magnesium as a reactive agent yielded most promising results for Li extraction.

Progress in Lithium-Manganese battery materials and Advancements in Reduced Graphene Oxide production

Research team at Sapienza Univ. of Rome (UoS) has been making progress in developing lithium-manganese-rich materials for battery applications. These materials were produced using an integrated hydrometallurgical process, which includes the production of reduced graphene oxide and a co-precipitation method that leads to the formation of lithium-manganese-rich cathodes. The resulting cathode materials are currently undergoing extensive physicochemical and electrochemical characterizations.

For the synthesis of reduced graphene oxide, the researchers compared two methodologies and observed differences in productivity. These differences are now being investigated to determine whether they are influenced by the thermal pre-treatment of the graphite or by the role of metals present in different oxidation states. The use of mechano-chemically treated powder has demonstrated remarkable productivity, reaching approximately 80%.

Enhanced solvometallurgical processes

As evoked by its name, solvometallurgy uses solvents to extract metals. Researchers at TEC have been optimising the process, using additives as copper (Cu) or hydrogen peroxide (H₂O₂) when necessary, achieving a high recovery rate of >95%. However, the process also increased the dissolved Cu content, which required additional steps to reduce it. Researchers are now exploring methods like cementation or electrodeposition to recover and reuse the dissolved Cu. The deep eutectic solvents (DES) were already regenerated and reused, result which could bring a positive impact on the process sustainability assessment.

Direct recovery of battery materials

The Gas-Diffusion Electrocrystallisation (GDEx) technology allows the one-step recovery of metals and synthesis of new materials with high added value. In the framework of the RHINOCEROS project, the research team at VITO has been focusing on optimising the GDEx technology to achieve the selective recovery of nickel (Ni), manganese (Mn), and cobalt (Co), contained in leachates from black mass and achieved 90 % extraction of Ni, Mn and Co. This two-step GDEx process facilitated the removal of all the impurities such as Cu, Fe from the leachate solution. Using the GDEx process, VITO researchers have successfully synthesised Layered Double Hydroxide (LDH) materials and spinel-type nanostructures from the synthetic solutions. The LDH materials were lithiated and LiNi_0.8Mn_0.1Co_0.1O₂ (LNMCO811) was synthesised, which could be used as a cathode active material for lithium-ion batteries (LiBs). The results obtained with synthetic solutions portray the potential of the method to obtain relevant active cathode materials out of leachate solutions.

Recovery of materials from low concentration waste streams

Aiming towards a zero-waste strategy for the recovery of metals from battery refining waste waters, LEITAT is working on the development and evaluation of novel polymer inclusion membranes (PIM). PIMs are a type of liquid membrane in which the liquid phase, the extractant, is held within a polymeric network. The interest in these membranes has been growing exponentially over the past few years as an alternative separation technique to conventional solvent extraction.

During the previous six months, the team at LEITAT have been investigating two types of membranes that have shown high selectivity, recovering manganese (Mn) and cobalt (Co) from mixed metal solutions. In their future research, LEITAT will use these membranes in combination to ensure increased selectivity of targeted metals.

Optimising lithium carbonate recovery

Lithium carbonate(Li₂CO₃) is another critical material for batteries, and researchers at TEC and LEITAT are working to optimise its recovery from various solutions. This involves fine-tuning the conditions for Li₂CO₃ precipitation, including the influence of pH and the presence of other cations. Tests are currently conducted with both synthetic solutions and real leachates to ensure the effectiveness of the process. Additionally, efforts are underway to automate the recovery process, which includes assembling elements for pH monitoring and CO₂ bubbling systems.

Bringing innovations to market

To bring these innovations to market, researchers are preparing to scale up their processes. This involves a selective process based on data collection, life cycle assessment (LCA) and life cycle cost (LCC) analysis, to ensure the best technological routes are chosen to be further upscaled and meet the production demands.

Author: KIT

During the third semester, researchers from KIT further studied and improved the conditions for the mechanochemical transformation of black mass (BM) into metallic black mass (MBM). Since BM supplied by ACC is already in a reduced state, they focused on reducing BM supplied by TES. This BM consists mostly of NMC (lithium nickel manganese cobalt oxides) cathode material and graphite, which was found to slow down the reaction kinetics. The reduction of the cathode active material by the metallic reducing agent result in the formation of the transition metals along with lithium oxide (Li₂O) and the oxide of the respective reducing agent, which can be monitored by X-ray diffraction.

In contrast to the previous two semesters, researchers switched from shaker mills to planetary mills, which enable control of the rotation speed and larger volumes that can be processed. Various parameters such as ball-to-sample ratio (BSR), ball size, total load and rotation speed were investigated to optimise for a short reaction time.

Main take-aways

In general, the higher the BSR, the more mechanical energy can be transferred per gram of powder which results in a more intense milling and a faster reaction; however, this limits the throughput. Larger balls, on the one hand, lead to higher kinetic energies. On the other hand, fewer balls are used to keep the BSR constant resulting in a lower collision frequency. The maximum rotation speed is lower to prevent damage to the grinding media.

With Calcium as the reducing agent, no reaction was achieved at all. An unfavorable combination of ductility and size of the calcium pieces seems to resist further size reduction, which is required for the reaction.

Aluminium has the advantage of being used as a current collector and is already present in the black mass. However, during the reaction, LiAlO₂ is formed, which is limiting the subsequent Li extraction efficiency in WP5. This problem can be avoided when magnesium is used as the reducing agent, which proved to be more reactive than aluminium but doesn’t form other lithium compounds than Li₂O.

Compared to the shaker mill, a higher reaction rate was observed in the planetary mill. Researcher from KIT achieved a complete conversion of the lithium transition metal oxide in the planetary mill within 3 h using Mg as the reducing agent. In a larger version of the mill, the required milling time increases to 8 hours. Here, further investigations are planned for the next months.

Read previous article on the pre-treatment operations: Pre-treatment operations: Reactive milling for the production of metallic black mass

Benefits of “offline programming”

Simulation environments have been widely used in robotics for demonstration and planning purposes. This typically takes place within a simulation software or any other platform that can replicate the robot’s dynamics, workspace and surrounding environment, and enable robotic programming. This replication system has proved to be cost- and time-efficient due to a series of advantages: no risk of disrupting the production by removing the robot from the production line, high flexibility allowing infinite number of configurations on a virtual model of the robot, reduced risk of equipment damage due to high predictability of malfunctions. For instance, operational industrial robots can be tested in a simulation environment before deployment. This process is often referred to as “offline programming”.

Researchers at Department of Engineering Sciences, University of Agder have been designing a simulator within a virtual environment to visualise and test various demanufacturing approaches for battery packs, allowing them to collect necessary data such as process duration, disassembly tools – all without the need of physical experiments. This innovative exploration not only streamlines data gathering but can also help identify and remove unforeseen bottlenecks in the disassembly process.

Environment configuration and use case application for battery pack demanufacturing

Using a simulation environment, known for its high-fidelity graphical capabilities, researchers at UiA were able to create a controlled virtual space ideal for visualising complex robotic processes and interactions related to demanufacturing electric vehicle (EV) batteries. The robotic cell design is decomposed across all the subtasks/segments of the disassembly process, with specific consideration to safety aspects and optimised efficiency and accessibility of robotic manipulators.

In order to study in depth and to demonstrate the efficacy of a proposed fully automated demanufacturing line, researchers at UiA meticulously recreated a virtual environment where they simulated the disassembly of a an EV battery pack. This simulation encompasses the entire process from automated discharging to the disassembly of packs into modules, subsequent characterisation, sorting, and finally, the disassembly of modules into individual cells. All elements of the simulation are animated using the simulation platform and a robotic operating system code, providing a holistic view of the potential automation within the demanufacturing process.

For this particular use case, researchers at UiA have calculated the time individually for each disassembly operation, reaching roughly between 12 and 14 minutes for the entire process.

The findings of this research that replicated the complete demanufacturing of EV LiB pack in a virtual, yet realistic industrial setting, illustrate the leverage of automated processes over conventional approaches conventionally relying on manual techniques. The simulation provides estimates for operation time for a given disassembly procedure (disassembly sequence and disassembly process). Upcoming steps will involve AI to generate and optimise the procedures. Additionally, the simulation can identify solutions to minimise human exposure to potential hazards associated with battery disassembly processes. Future in depth and multidisciplinary research is required to optimise the disassembly sequences and process in the simulated environment by training reinforcement learning agents and including a collision avoidance system, to name a few.

Ultimately, the aim of this research is to anticipate the increasing number of EV batteries that will be decommissioned soon, and to ensure a proper management of waste, while recovering all the resources available in clean mobility technologies.

Discover UiA’s previous activities

Despite a different objective, the RHINOCEROS project partners have shown growing interest in the Digital Battery Passport, an initiative of FREE4LIB, a sister project from the Cluster Hub “Production of raw materials for batteries from European resources”. This collaboration shows our commitment to contributing to the European battery community through the exchange of knowledge and experience.

The FREE4LIB workshop had a three-fold objective, including a brief presentation of the preliminary results of the battery passport concept development, the outline of the implementation challenges and potential follow-ups of industrial scale-up, and the clear differentiation between battery second use (B2U) versus recycling. The event drew approximately 50 participants from various segments of the battery value chain, which ensured a comprehensive and multifaceted perspective of the subject matter.

The introductive session presented the FREE4LIB project, briefly highlighting past achievements and focusing mainly on the remaining activities outlined in the workplan. The following session was led by Julius Ott (industrial engineer with expertise in circular economy at Karl-Franzens-Universität Graz). During the past year, researchers at Univ. of Graz worked on finalising data collection and processing related to the development of a data model of the digital passport platform which aims to close the information gap between beginning-of-life (BoL) and end-of-life (EoL) battery lifetime. This interactive session turned out to be an appropriate opportunity for researchers at Univ. of Graz to present the outcomes of their data collection and handling, and to evaluate their relevance within the reality portrayed by the workshop attendees.

Participants, predominantly familiarised with the EU-funded battery projects, confirmed the findings reported by Univ. of Graz. However, they also raised concerns about data sharing. The outcomes of the interactive session, complementing prior research, will serve as valuable guidance for the FREE4LIB project in implementing the battery passport within their project.

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For additional background information on the digital passport developed by FREE4LIB, please refer to previous articles.