News

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. 

Work during the first six months has focused on the evaluation of different extractants for the target metals: lithium, manganese, cobalt and nickel. Researchers established a liquid-liquid extraction protocol based on two different processes in which the target metal is extracted and recovered separately. During the extraction step, a specific carrier compound selective towards the target metal separates an amount of it from a feed metal solution. The recovery of the metal takes place in the second process, where a stripping solution is employed to recover the metal previously extracted through the carrier. Initial PIMs containing the most efficient extractants have been prepared, characterised and are currently evaluated. The featured image depicts the continuous procedure used to test the synthesised PIMs.

The current industrial pre-treatment and downstream processes (e.g., pyrolysis, calcination, etc.) are still inefficient and have significant limitations. Plastics and electrolytes sacrificed in the initial stages of the recycling process are overlooked when it comes to their recovery. Within the RHINOCEROS project, Chalmers University [CHA] is working on recycling of ignored content of the LIBs waste, electrolyte and polymeric materials by developing an innovative process based on Supercritical Carbon Dioxide (sc-CO₂) technology. 

Due to its environmental friendliness, non-toxic, low cost and straightforward processing features, the sc-CO₂ technology has been attracting both scientific and industrial interest. With consistent leverage over other processes, sc-CO₂ technology is already widely used in various industries including food, cosmetic and pharmaceutical industries [i.e., to decaffeinate coffee or tea, extract vegetable oils etc.] Although it has many applications, its use in battery recycling was recently discovered and the Chalmers research group is one of the pioneers in this field. 

Within the project’s framework, CHA researchers are targeting the development of the sc-CO2 extraction process which will selectively recycle the electrolyte and the polymeric material from the LiB waste. The electrolyte, binder, and separator will be recycled in subsequent steps and purified to reuse in the battery industry. For this purpose, several critical process parameters such as pressure and temperature are investigated to achieve high recycling efficiencies under feasible conditions. 

Electrolyte recovery

The electrolyte in the LiB is a complex system usually composed of a conductive salt dissolved in a matrix of various solvents and additives. The most recent results reported by CHA on sub- and sc-CO₂ research show that at low pressure and temperature conditions, the non-polar electrolyte components (almost 66% of the electrolyte) were selectively recovered without the generation of toxic gas emissions, which are typically generated by thermal recovery processes originated by the decomposition of the thermally unstable conductive salt.

In this recycling step, the polar electrolyte components are left in the sample as residues and a subsequent recycling step using suitable cosolvent is required for their selective extraction. During the upcoming phases, researchers will aim to recover the electrolyte completely, including conductive salt and solvents. 

In this recycling step, the polar electrolyte components are left in the sample as residues and a subsequent recycling step using suitable cosolvent is required for their selective extraction. During the upcoming phases, researchers will aim to recover the electrolyte completely, including conductive salt and solvents. 

The selection of the co-solvent is critically important not only for effective recycling but also for the sustainability and the feasibility of the developed processes. To assess the suitability of the sc-CO₂ process, its environmental impact and economic competitiveness, CHA researchers explored also other solvents, which allowed them to select the most promising candidates for future research.  

In the upcoming months, CHA will study the effects of co-solvent modified sc-CO₂ system parameters on the recycling efficiency of PVDF and the structural properties of the recycled material. Researchers will carry out intensive characterisation studies to clarify the changes in the material structure, to determine the quality, and to optimise the process to reach the reusability goal. 

During the first six months, University of Adger [UiA] received three battery packs (out of the five planned) and manually disassembled them, opening for further analysis. In the future, this activity will feed a digital repository as promised in the first delivery of Work package 3. 

For each battery pack, the analysis includes: 

• a precedence graph informing how components are connected, which, in the upcoming steps, will help determine the best order to dismantle these components automatically.   

• an Excel table listing the characteristics of each type of component other than geometrical characteristics: number of items, mass, material, or other specific features.  
• 3D scanning in the form of point clouds (pcls) to provide information on the geometry and texture of the components constituting the different battery packs. After testing several hardware and algorithms, two of them have been selected.  

In parallel, several of the main important tools have already been identified based on the manual disassembly of these three battery packs, and a tool changer is under development. End effectors (tools) will be able to be changed quickly, including their connection to their power source (electric and/or pneumatic) and their signals. 

In addition, the disconnection of power and signal cables using non-destructive methods – operation identified as critical, has been investigated and currently, a concept is prototyped and evaluated. The main challenge is to design a tool that “fits them all”. Additional activities carried out within WP3 have investigated different sorting (characterisation) methods, based on temperature, mass loss, and other flaws, such as deformations, leakage, trace of heat damages.  

Safety has also been an important part of the work completed within WP3 during the first six months. A complete monitoring system and a set of safety measures to be followed during the scheduled demanufacturing (discharge, sorting and disassembly) activities have been established.  

During February, when the researchers started examining the available methods for automatic task planning using search algorithms and/or reinforcement learning, the robotic system adaptability was discussed. In anticipation of the implementation and testing phases of these adaptive robotic methods, thorough battery knowledge stored within the digital repository must first be developed.

Focusing on mechanochemical (MC) processing, the chemical transformation of the black masses (BMs) supplied by partners ACCUREC and TES, is planned to be carried out within Work package 4. 

Before MC processing, the black masses were analysed using a combination of different analytical techniques. Both quantitative and qualitative analysis were undertaken to determine the Lithium and transition metals yield of the developing recycling process. 

Using different reducing agents such as Al, Ca, and their mixtures, researchers carried out preliminary investigations of the MC processing of BMs. Within this task, different aspects, such as the role of the ball milling conditions, the ball milling time, presence of other nonreactive components, and nature of the reducing material were investigated. The analysis led to the conclusion that the kinetics of the MC-induced reduction reaction is sensitive to multiple processing parameters, as shown in the featured image: 

XRD patterns of the as-received BMs and products of their reduction after MC processing with Al and Ca as reducing agents: left-TES material; right-ACC material

The upcoming research will focus on improving the reduction reaction kinetics and eliminating the possible safety hazards of fine powder materials. Once finalised, this work will determine the optimal ball milling conditions to be scaled up. 

Recovery of Lithium as battery grade materials

The process described in Task 4.4 leads to the chemical transformation of the black masses (BMs) into ferromagnetic Co-, Ni- and Mn-containing products, which will be separated from other by-products. Lithium will be extracted from the rest of the solid products in the subsequent aqueous leaching process to be further transformed into battery-grade lithium carbonate (Li₂CO₃) salt. 

Within the M1-M6 period, aqueous leaching of the ball-milled samples using Al and Ca as reducing agents (RA) was carried out. At a preliminary stage of investigations, researchers noticed the resulted Li₂CO₃ materials presented small amount of impurities. 

To increase the yield of lithium recycling, in the upcoming period, the research work will target the improvement of the leaching conditions and the purification process.  

X-ray diffraction patterns of the as-milled BM obtained from TES, products of their reduction reactions after MC processing with Al (left) and Ca (right) as RA, and obtained Li salts after aqueous leaching

TECNALIA [TEC] has actively undertaken both the coordination tasks and the experimental activities that correspond to the solvometallurgical treatment of the received black masses. Firstly, the coordination of the project started with the preparation of the kick-off meeting, in which the entire Consortium assembled in San Sebastián (Basque Country – Spain) and comprises administration and management to ensure an efficient development of RHINOCEROS project. 

Also, the experimental section concerning the critical materials extraction from the received black masses from spent batteries started out after receiving the samples from partners ACCUREC [ACC] and KIT.  

After characterisation, TEC performed a first round of tests to these samples using a solvometallurgical route and assessing pre-treatment effect on the process. In parallel, State of Art is analysed for different relevant solvometallurgical systems aiming lithium recovery. New batches of experiments will be performed for process optimisation and new tests will also be performed when further black mass samples are received. 

VITO has developed the Gas-Diffusion Electrocrystallisation (GDEx) technology for various metal extraction processes. The GDEx technology utilises gas-diffusion electrodes to recover and synthesise different electrodic materials in the form of precipitates containing the desired metals. This process has shown promising results in metal recovery and selectivity, particularly for different metal extraction process.

The GDEx team has conducted experiments with synthetic solutions to optimise the metal recovery yield and selectivity by investigating the effect of different metal precursor solution to the process. Once the GDEx process is optimised with synthetic streams and the precipitating mechanisms are better understood, the team plans to extend the process to various spent battery waste products obtained from consortium partners. The process will involve precipitation in the form of layered-double hydroxides, and the team will investigate the downstream steps required to obtain recycled battery-cathode material. This is an important step towards sustainable and environmentally friendly practices in the battery industry.

Find out more information about the GDEx process at http://gdex.vito.be

Publication: Synthesis of material libraries using gas diffusion electrodes. Mater. Chem. A, 2020,8, 11674-11686