*3.1. Waterjet-Based Recycling: Process Description*

This process for recycling TBs is a direct recycling process that aims to recover the electrode coatings of a lithium-ion cell and is currently being practiced in a pilot plant of the industrial DeMoBat project partner Erlos GmbH. In addition to LiNixMnyCozO2 (NMC) cells, other cell chemistries with liquid electrolytes are processable with this recycling approach. The recycling process is described below using an NMC cell with a liquid electrolyte. The stoichiometry of the cathode coating is irrelevant and the NMC material recovered by this approach should subsequently be able to be used directly to produce new TBs. To clarify whether this is possible or not is currently being investigated as part of the DeMoBat project. The graphite of the anode can also be recovered, but in this case is

not. Due to the usual cathode material recovery rate of at least 90%, or usually higher, this value has been used for this LCA. The other battery components can be recovered almost completely, except for the electrolyte, as this is not treated and therefore not recovered. In Figure 3, the waterjet-based recycling process flow is illustrated with its material input flows. Material flows leaving the process are not shown, due to the defined system boundary. The waterjet-based recycling process can be divided into six process steps as shown in Figure 3, which shows the energy, compressed air, and cathode material flows. Most of the process steps are automated and some are carried out manually. The entire recycling process requires 0.486 MJ of electrical energy for processing 1 kg of TBs.

**Figure 3.** Process flow chart with material input flows and route of the recyclate, with 1 kg of traction batteries as the initial value.

When delivered, the TBs are opened manually and completely deep discharged. In this step, electrical energy recovered by the deep discharge can be fed into the production grid. To minimize the dangers posed by TBs, they remain short-circuited for 24 h.

After the step of complete deep discharge, the TBs are manually dismantled to the cell level and the separated components, such as the battery housing, the cooling system, the electric and electronics are fed into the usual recycling channels. The energy required for dismantling is low, as it is largely carried out manually at the present time. After removal of the modules, the cells can be separated individually from the battery modules, and, due to the manual disassembly, this step is not energy-intensive. The required energy is allocated to pneumatic, electric power tools and the production environment. Since the compressed air requirement cannot be divided more concretely, it is divided equally between the two sub-process steps of dismantling, as shown in Figure 3. Then, these cells are automatically opened and further disassembled using different methods, depending on the cell typ. In pouch cells, the electrodes and the separator are usually stacked, while in prismatic cells, a stack of cathode, separator, and anode is rolled up. This step is mainly automated. During the cell disassembly, there is no direct treatment of the electrolyte and therefore, some of the electrolyte is trapped in the activated carbon filter.

Since the saturated activated carbon filter is not desorbed in the pilot plant, these materials are replaced regularly. The gases obtained through the opening of the cell, the water jetting, and the drying are captured by a permanent suction system, filtered by activated carbon, and released into the air.

After separation of these components, the anode and cathode are each fed separately into the electrode decoating process. Separating the anode and the cathode significantly increases the purity of the recyclate and eliminates the need of inerting the process, and therefore leads to energy and cost savings. The decoating of the electrodes is primarily a mechanical removal of the electrode coatings with the aid of a water jet, where the anode and cathode are passed through this process step separately, and this is described as water jetting.

High-pressure water jetting processes are being used more and more [31]. The possible applications include cleaning processes, decoating processes, cutting processes and others [32]. When the water flows through the nozzle, the pressurised flowing water is accelerated. The radius of the water jet becomes larger the further the nozzle is positioned from the target. In addition, the water jet speed decreases with increasing distance from the nozzle. This enables using waterjet processes for various applications. For cutting processes using a waterjet, the distance between the nozzle and the target workpiece is kept small, while decoating processes are carried out at a greater distance. This is because as the distance to the workpiece increases, the difference in jet speed between the center of the water jet and the outer edge of the water jet decreases. In this way, a more consistent removal result can be achieved over a larger area [32].

For this process step, the entire electrode is placed on a conveyor belt, which moves at a constant speed through a washing system. In this washing system, a water jet removes the coating from the cathode and anode collector foil. This process water circulates within the washing system and is rarely exchanged, which is why the total water requirement can be classified as low. During this process, the coating material sediments in the catch basin of the washing system can be recovered by filtration. No special temperature is required for water jetting of the electrodes, therefore, this process step is carried out at room temperature. The remaining electrolytes in the coatings of anode and cathode are washed out during the water jetting, thus, they mix with the process water. Those remaining electrolytes cause the process water to become acidic, which is neutralized by adding sodium hydroxide (NaOH). Since the pH value of process water is kept in a slightly basic range, the amount of NaOH required depends on the pH value of the process water. This process step is highly automated, and it is the most energy-intensive process step in this recycling process. In addition to the electrode coating, the water jetting process also recovers the carrier foil, which can then also be specifically recycled.

Then, the recovered electrode material is dried in an oven for 3 h. Dust produced in the process step is also treated by an air purification system. Packaging and sampling are the final steps in the process chain which require the least amount of energy. In this step, the recyclate is ground to a desired particle size and examined according to its composition. The amount of recovered cathode or anode coating depends mainly on the processed TBs, as there are differences in coating thickness and resistance to water jetting.

## *3.2. Greenhouse Gases and Cumulative Energy Consumption*

Figure 4 shows the LCI of the described process flow with a selection of greenhouse gases, particulate matter (PM10), the cumulative energy consumption, and the water consumption, each subdivided into the different process steps. A cumulative energy input (primary energy demand from regenerative and non-regenerative resources) of 3.3 MJ is calculated. As shown in Figure 4, water jetting and air purification are the most energy-intensive process steps, and they are also the biggest emitters of NMVOCs, methane, carbon dioxide, and nitrogen oxides. A closer look at the water jetting step reveals that both NaOH (50%) and the necessary electrical energy are the biggest contributors to gas emissions. For the entire recycling process, a water consumption of 4.6 L could be determined, and water jetting has the largest share of water consumption among all process steps, with approximately 3 L. Although this recycling approach is a waterjet-based process, the water consumption required for water jetting plays only a minor role, with 0.909 L. The remaining water consumption is mainly attributable to the provision of electric

energy and the NaOH. The relatively high impacts of the air purification process step for many emissions are mainly attributable to the filter material (activated carbon), while the necessary energy consumption is less decisive. For the nitrous oxide and fluorinated and chlorinated hydrocarbons, more than 50% of the emitted gas belong to the water jetting step, because of its high energy consumption. The second largest contributor is dismantling, which is due to the high energy requirements and the necessary protective equipment, such as gloves and respiratory protection, as shown in Figure 4. Since sampling and packaging only require a very small amount of electrical energy, this step produces up to 1% of the emitted gases, which is the lowest share as compared with other steps.

**Figure 4.** Life cycle inventory (LCI) with selected emissions and cumulative energy consumption of the waterjet-based recycling with the functional unit of 1 kg traction batteries. Amounts smaller than 1% are not shown.
