WO2025108892A1

WO2025108892A1 - Direct recycling of alkali metal ion battery electrodes

Info

Publication number: WO2025108892A1
Application number: PCT/EP2024/082725
Authority: WO
Inventors: Wolfgang Rohde; Frank Mueller; Dennis Loesch; Lothar Ziegler
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2023-11-20
Filing date: 2024-11-18
Publication date: 2025-05-30
Anticipated expiration: 2026-05-20

Abstract

The present disclosure relates to methods for direct recycling of alkali metal ion battery electrode production scrap.

Description

Direct Recycling of Alkali Metal Ion Battery Electrodes

Field of the invention

Background

Two different basic approaches are used in the recycling of alkali metal ion battery materials, in particular, cathode active materials (CAM) present in the batteries. One approach comprises the complete destruction and dissolution of the cathode active materials by metallurgical processes and subsequent synthesis of new cathode active materials from the metal salts obtained. The other approach comprises the separation of the cathode active materials or anode active materials from battery components and direct re-introduction of the particulate material obtained into electrode production - the so-called "direct recycling".

Direct recycling is especially of interest for production scrap, as the electrode active material in such materials is almost virgin. One challenge in direct recycling is avoiding contamination of the recovered electrode active material. In the worst case, foreign particles present as impurities might cause fatal battery failures. In particular, contamination by aluminum particles in the case of cathodes, or copper particles in the case of anodes, of lithium ion batteries may occur upon the detachment of the electrode active material from the respective current collector foil.

In EP 3 940 872 A1 and EP 2 975 686 A1 , respectively, a rotor impact mill has been suggested for the detachment of the cathode active material from the cathode current collector foil. However, own experiments indicate comparatively high contamination of the material obtained with aluminum.

Christian Hanisch et al.: "In-Production Recycling of Active Materials from Lithium-Ion Battery Scraps", ECS Trans. 64 (2015) 131 -145 describe a process involving mechanical detachment using a cutting mill operated at peripheral rotor speeds of 10 m/s and bottom sieve mesh sizes in the range of 0.75 to 2 mm. The content of aluminum impurities in the product obtained was in the range of from 0.8 to 3%.

Christian Hanisch et al.: "Recovery of Active Materials from Spent Lithium-Ion Electrodes and Electrode Production Rejects" in J. Hesselbach and C. Herrmann (eds.): "Globalized Solutions for Sustainability in Manufacturing: Proceedings of the 18th CIRP International Conference on Life Cycle Engineering, Technische Universitat Braunschweig, Braunschweig, Germany, May 2nd - 4th, 2011", Springer-Verlag, Berlin, Heidelberg 2011 , pp.85-89 describe the influence of the peripheral speed of a cutting mill on the detachment. The peripheral rotor speed was varied between 1.2 and 10 m/s and the sieve mesh size was 2 mm, the content of aluminum impurities in the product obtained was in the range of from 0.7 to 1%. In the same publication, an alternative process for the delamination of cut electrode foil pieces employing N-methyl pyrrolidone (NMP) as solvent for the PVDF binder polymer was described. The pre-cutting was performed manually or by a cutting mill under nondisclosed conditions. The cut foil pieces were directly treated with NMP at 90°C in a stirred reactor without prior sieving. The delamination was done in up to 6 stages of 15 min stirring at 90°C to achieve a final delamination efficiency of 97%, the delaminated coating material had an aluminum content of 0.06%.

CN 106129513 A describes a process of recovering electrode active materials from batteries comprising dismantling of the batteries and treating the electrodes with appropriate solvents to dissolve the binder polymer. In the description it is mentioned that the electrode sheets are cut into pieces of 1 cm², the method of comminution is not further disclosed in detail.

CN 110885072 A describes the delamination of electrode sheets by organic solvents. The electrode sheets are cut into pieces of 10 x 10 cm, the method of comminution is not further disclosed in detail.

Summary of the invention

The present disclosure provides a method of recycling electrode active material from alkali ion battery (comprising lithium-ion batteries or sodium-ion batteries or potassium-ion batteries or magnesium-ion batteries) electrodes which comprise electrode active material coated on a metal foil. The recovery of the coated electrode active materials comprises four consecutive steps:

1. Mechanical comminution of the foil pieces employing a cutting mill under avoidance of significant detachment of the coating,

2. separating the coarse fraction of coated foil pieces in the material obtained in step 1 from detached coating,

3. solvent treatment of the coarse fraction of coated foil pieces from step 2 in a solvent capable of dissolving the binder polymer within the coating,

4. separation of the delaminated coarse foil pieces from the delaminated electrode active material.

The method of the present disclosure avoids applying strong mechanical forces to the electrode during comminution. A cutting mill operated under conditions exerting low mechanical stress is used to provide smooth cutting conditions and prevent abrasion of metal particles and detachment of the coating from the electrode current collector foil during comminution. This is achieved by employing cutting mills wherein the milling chamber comprising the rotating blades or knifes is separated from the exterior space to which the cut pieces are discharged by a mesh with openings having at least 3 mm width. This explicitly includes the case where the mesh is given by the frame of the exterior space to which the cut pieces are discharged. The electrodes are first cut into pieces of irregular size in a cutting mill operated at conditions where the quotient q of peripheral rotor speed v and mesh diameter d of the sieve bottom of the cutting mill is at most 800 [1/s]. Subsequently, the electrode active material is delaminated from the comminuted electrodes, and the pieces of metal foil obtained are separated from the electrode active material, which then can be recycled into the production of new alkali ion battery electrodes.

Brief description of the drawings

Fig. 1 a shows a diagram of dry delamination efficiency R(D) in a cutting mill (Wanner C17.26) as a function of the quotient q of peripheral rotor speed v and bottom sieve mesh diameter d.

Fig. 1 b shows a diagram of dry delamination efficiency R(D) in a cutting mill according to the data given by Hanisch and Hermann as a function of the quotient q of peripheral rotor speed v and bottom sieve mesh diameter d.

Fig. 2a is a schematic diagram of a cutting mill

Fig. 2b is a schematic diagram of a cross-cutting mill

Fig. 2c is a schematic diagram of another cross-cutting mill

Detailed description

The method of the present disclosure comprises a. comminuting alkali ion battery electrodes comprising electrode active material coated on a metal foil using a cutting mill wherein the milling chamber comprising the rotating blades or knifes is separated from the exterior space to which the cut pieces are discharged by a mesh having openings of at least 3 mm width, the cutting mill being operated at q < 800 [1/s], with q = v/d, v being the peripheral rotor speed of the cutting mill, and d being the mesh diameter of the sieve bottom of the cutting mill, b. removing any particles having a length in at least two dimensions of less than 100 pm from the comminuted electrodes in a first separation step, e.g., by dry sieving (e.g., in a vibratory screener), air classification, cyclonic separation (dry or wet), wet sieving, or combinations thereof, c. subsequently treating the comminuted electrodes with a solvent able to dissolve a binder polymer present in the coating of the metal foil to delaminate the electrode active material from the metal foil, and to produce a slurry comprising dispersed electrode active material and pieces of metal foil, d. separating the pieces of metal foil from the slurry comprising dispersed electrode active material in a second separation step, e.g., by wet sieving or wet separation (e.g., a hydrocyclone), e. optionally, providing a current collector metal foil and coating it with the slurry comprising dispersed electrode active material obtained in step d.

In the method of the present disclosure, off-spec electrodes from alkali ion battery production are comminuted into smaller pieces using a cutting mill. The electrodes can directly be conveyed into the feeding hopper of the cutting mill. It is desired to keep as much as possible of the coating attached to the current collector foils in the comminution step, avoiding any detachment of the coating under the processing conditions.

In the method of the present disclosure, the cutting mill is operated at conditions where the quotient q of peripheral rotor speed v and mesh diameter d of the sieve bottom of the cutting mill is at most 800 [1/s], i.e., q = v/d < 800 [1/s]. In some embodiments of the method, the value of q is at most 500 [1/s]. In some embodiments of the method, the value of q is at most 300 [1/s]. In some embodiments of the method, the value of q is at most 200 [1/s]. In some embodiments of the method, q is in the range of from 100 [1/s] to 800 [1/s], e.g., 100 [1/s] to 500 [1/s], In some embodiments of the method, the peripheral rotor speed of the cutting mill is in the range of from 0.1 to 5 m/s, for instance, from 1 to 4 m/s, e.g., from 1 .8 to 3.0 m/s.

Two different types of cutting mills can be used in the method of the present disclosure:

1 . Cutting mills with stator blades mounted on the inner wall of the milling chamber and one rotor equipped with blades. The stator and the rotor blades both are orientated parallel to the rotation axis of the rotor. The milling chamber is separated from the exterior discharge space by a mesh having at least 3 mm mesh width limiting the size of the particles that can leave the milling chamber and pass to the discharge space.

2. Cross-cutting mills comprising two counter-rotating rotors equipped with circular knifes cutting in a direction perpendicular to the rotor axes. These knifes are arranged in such a way that one knife of one rotor gears between two knifes of the opposite rotor. The knives of the two rotors are able to cut sheet-like material into parallel stripes orientated perpendicular to the rotor axes. To cut these stripes into pieces, each knife of the rotor is equipped with blades orientated parallel to the rotor axes or inclined towards the rotor axes with an inclination angle of less than 90°. In these types of mills, the milling chamber is not separated from the discharge space by a mesh, as the dimensions of the cuttings are determined by the arrangement of the circular knifes and the blades.

The cutting mill of type 1 features a sieve bottom having openings through which comminuted material passes and leaves the cutting mill. In some embodiments, the openings are circular holes. In other embodiments, the openings are square holes, rectangular holes or trapezoidal holes (also known as Conidur®). Oblong or transverse holes are possible as well. In some embodiments, the diameter of the openings is at least 4 mm, for instance, at least 8 mm, or at least 12 mm. In some embodiments, the diameter of the openings is in the range of from 4 mm to 16 mm. The diameter is defined here as the largest distance between two opposite sides (square holes) or between two opposite points (circles, rectangles or trapezoids).

In one embodiment of the method, the comminuting step a) is performed under dry conditions. In another embodiment of the method, the off-spec electrodes are wetted with a suitable solvent, preferably the solvent that will be employed in the coating, that is able to be absorbed by the binder polymer present in the coating prior to the cutting. Wetting renders the coating more ductile and helps to avoid detachment of coating particles. The wetting may be performed at elevated temperatures, depending on the type of solvent. Water may be best used in a temperature range of 20 to 90°C; in the case of N-methylpyrrolidone (NMP), a temperature range of 20 to 150°C may be applied. After the comminution, the wetted comminuted material may be dried.

Alkali ion battery electrodes comprise an electrode active material coated on a current collector metal foil. In some embodiments, the metal foil is comprised of aluminum. In other embodiments, the metal foil is comprised of copper. The coating comprises fine particles of electrode active material and a polymeric binder. In some embodiments, the binder polymer comprises polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose, or styrene-butadiene rubber (SBR).

In some embodiments, the electrode is a cathode comprising a cathode active material (CAM) coated on an aluminum foil. Examples of cathode active materials include LiNi_xMn_yCoi-x-yO₂ (NCM), LiFePO₄ (LFP), LiMn₂O₄, Na₂/₃Fei/₂Mni/₂O₂, and Nai.₈8Fe[Fe(CN)₆]-0.18 H₂O. In some embodiments, the electrode is an anode comprising an anode active material coated on a copper foil. Examples of anode active materials include graphite, hard carbon, and molybdenum disulfide.

The electrode pieces obtained from the cutting mill are sent to a first separation step, wherein any fine particles are separated from the cuttings. In case of dry operation, sieves or air classifiers or combinations of these are employed. In case of wet separation, wet sieves, inclined classifiers, wet cyclones (hydrocyclones), or combinations of these are used, and the liquid preferably is the same that is used in all other wet process steps including the coating step e), if applicable. These fine particles may contain fine metal particles from the current collector foils which should not get into the electrodes produced from the recycled electrode active material and contaminate them. Therefore, the fine fraction obtained in the first separation step is sent to a different recycling process, e.g., a pyro- or hydrometallurgical process as known in the art. It is thus desirable to minimize the generation of fines in the comminution step.

After comminuting the battery electrodes and removing any particles having a length in at least two dimensions of less than 100 pm from the comminuted electrodes, the comminuted electrodes are treated with a solvent able to dissolve a binder polymer present in the coating of the metal foil in order to delaminate the electrode active material from the metal foil and to produce a slurry comprising dispersed electrode active material and pieces of metal foil.

In an embodiment of the method, the coarse material obtained after the first separation step is transferred to a reactor, and the electrode pieces are treated with a solvent able to dissolve the binder polymer in the coating of the electrode pieces. In an embodiment of the method, the solvent comprises N-methyl-2- pyrrolidone (NMP). In another embodiment, the solvent comprises DMSO and/or water. Preferably, the solvent is the same solvent that is used in the electrode coating during the fabrication of the electrodes. In the case of dry- coated electrodes, a solvent is used that is able to dissolve the binder, and the solvent will be removed finally by solid-liquid separation and drying to obtain a dried electrode active material. In an embodiment of the method, the same solvent is used in all steps. The solvent is equivalent to the solvent that is used in the coating process of the electrode production. The treatment with a solvent is preferably performed at elevated temperatures. In the case of water, temperatures up to 100°C are used, in the case of other solvents, the upper temperature limit is given by the boiling point of the solvents. In the case of very high boiling solvents like NMP or DMSO, the temperature preferably is in the range of from 95°C to 150°C.

After the solvent treatment, the mixture of detached coating and electrode carrier foil pieces suspended in the solvent are transferred to a sieve or wet classifier (e.g., a hydrocyclone), or a combination of both, to separate the electrode carrier foil pieces from the detached coating. The pieces of metal foil are separated from the slurry comprising dispersed electrode active material by wet sieving or classification by wet classifiers (e.g., hydrocyclones).

In one embodiment, a single sieve having a mesh width of 100 pm is used to separate the metal foils, allowing the separation of fine and coarse particles in one step. Since usually the size difference between the metal foils and the fine particles is very large, a separation by sieving in several consecutive steps may be advantageous. Thus, in another embodiment, the metal foils are separated with a coarse mesh, e.g., 4 mm, in a first sieving stage, then the slurry obtained is sieved using a 100 pm mesh to separate fine particles. Such sequence of sieving steps can be performed by a stack of different sieves feeding the feed material to the upper coarsest sieve and discharging the product passing the lower finest sieve.

In a sequence of sieving stages, at least one stage may be performed by a wet classifier (e.g., a hydrocyclone) instead of a sieve.

In an embodiment of the method, wet sieving in step d) involves an inclined classifier. In a further embodiment of the method, a sieve screen used for wet sieving in step d) is sprayed with solvent to wash off particles of electrode active materials adhering to the pieces of metal foil. In a further embodiment of the method, the solvent is obtained from the slurry obtained in step d) by solid/liquid separation.

In an embodiment of the method, fine particles are removed from the slurry obtained after step d) by sieving on a sieve screen with a fine mesh (100 pm) or by classification in wet classifiers (e.g., hydrocyclones). After the separation of the carrier foil pieces, the slurry of detached coating obtained may be sieved on another sieve screen with even finer mesh (< 100 pm, or < 50 pm, or even < 20 pm) to remove fine particles.

The slurry comprising electrode active material obtained can be used for coating current collector foils, i.e., for the production of alkali ion battery cathodes or anodes. In one embodiment of the method, pristine electrode active material and/or binder polymer and/or conductivity-enhancing additives are added to the slurry obtained in step d) to adjust the composition of the slurry to match the specifications of a slurry usable for battery electrode coating. In an embodiment, the conductivity enhancing additives comprise carbon black.

The present disclosure also provides an electrode active material recovered from electrode sheets which contains less than 0.06 wt% of aluminum metal and less than 0.06 wt% of copper metal. The electrode active material is obtained by the method disclosed herein.

Detailed description of the drawings

Fig 1 a shows a diagram of dry delamination efficiency R(D) in a cutting mill

(Wanner c17.26) as a function of the quotient q of peripheral rotor speed v and bottom sieve mesh diameter d, using values obtained in the working examples of the present disclosure.

Fig 1 b shows a diagram of dry delamination efficiency R(D) in a cutting mill as a function of the quotient q of peripheral rotor speed v and bottom sieve mesh diameter d according to the data disclosed by Hanisch and Hermann.

Fia 2a is a schematic diagram of a cutting mill 20 The mill 20 comprises a rotor

21 featuring rotor blades 22 on its periphery. The mill also comprises a stator 23 featuring stator blades 24 on its inner wall. The rotor 21 and the stator 23 are coaxial. A part of the wall of the stator 23 is formed by a separating mesh 25. Particles having a size smaller than the mesh openings can pass from the space between rotor 21 and stator 23 through the separating mesh 25 into a discharge space 26.

Fig. 2b is a schematic diagram of a cross-cutting mill 30. The cross-cutting mill features two counter-rotating rotors 31 equipped with circular knives 32 cutting in a direction perpendicular to the axes of the rotors 31 . Each circular knife 32 of the rotors 31 is equipped with blades 33 inclined with an inclination angle of less than 90° towards the axes of the rotors 31 . Stationary racks 34 intermesh the circular knives 32 of the rotors 31 . The cutting perpendicular to the rotors occurs by shearing the foils between the circular knives 32 and the stationary racks 34.

Fig. 2c is a schematic diagram of another design of a cross-cutting mill 40. It differs from the design shown in fig. 2b by the absence of stationary racks. Instead, the rotor axes 41 are designed as thick shafts 44, and the cutting perpendicular to the rotors occurs by shear between one circular knife of one side and one shaft of the opposite site. The circular knives 42 are again equipped with blades 43 parallel to or inclined towards the rotational axis.

Examples

Example 1a

5,040 g of a 15 pm aluminum foil was granulated in a cutting mill (Wanner C17.26 sv) equipped with a 4 mm circular hole bottom sieve at a rotor speed of 380 rpm (peripheral rotor speed 3.4 m/s). The material was sieved using a sieve with 100 pm mesh width. No particles <100 pm were found.

Example 1b (comparative)

3950 g of the coarse material >100 pm from example 1 a were introduced into an impact mill of the type Alpine LU100 equipped with a 100 mm plate beater and a 2 mm round hole sieve. The mill was operated at 10.000 rpm. The material obtained contained 0.25 wt% of Al-particles <100 pm, 11.7% between 100 and 500 pm and 88% >500 pm, as measured by sieve analysis. These examples demonstrate that the cutting mill avoids the formation of small Al particles <100 pm, while the impact mill produces a considerable amount of aluminum fines. These examples demonstrate the importance of mechanical forces on the formation of fine Al-particles which can be suppressed in cutting mills even at q-values > 800 [1/sec]. Here, the use of q-values is not helpful as no delamination can occur. In the case of coated metal foils, the delamination can be correlated with the q-values. The formation of Al particles is higher than in the case of non-coated foils, as the coating may also effect the cracking of the metal foils, e.g. by initiation of cracks in the coating and propagation through the metal foil.

Example 2

An aluminum foil (thickness 16 pm) coated with LFP typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 15 mm circular hole bottom sieve at a peripheral rotor speed of 1.8 m/s. 1.3 wt% of a fraction of <100 pm were obtained, which contained 0.06 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. No Al could be detected by XRF in the filter residue. The delamination efficiency measured was 92%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes was 91%.

Example 3

An aluminum foil (thickness 16 pm) coated with LFP typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 4 mm circular hole bottom sieve at a peripheral rotor speed of 1.8 m/s. 8.7 wt% of a fraction of <100 pm were obtained, which contained 0.26 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved with a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. No Al could be detected by XRF in the filter residue. The delamination efficiency measured was 96%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes was 88%.

Example 4

An aluminum foil (thickness 16 pm) coated with LFP typically employed in commercial lithium-ion batteries was treated in a cutting mill (Pallmann PS 3 1/2) equipped with a 15 mm square hole bottom sieve at a peripheral rotor speed of 12 m/s. 3 wt% of a fraction of <100 pm were obtained, which contained 0.05 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. The filter residue contained 0.25 wt% Al, as measured by XRF. The delamination efficiency measured was 91%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes for the mechanical and solvent delamination was 88%.

Example 5 An aluminum foil (thickness 16 urn) coated with NCM containing 0.3 wt% Al typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 15 mm circular hole bottom sieve at a peripheral rotor speed of 1.8 m/s. 8.8 wt% of a fraction of <100 pm were obtained, which contained 0.4 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. The filter residue contained 0.31 wt% Al, as measured by XRF. Thus, at most 0.01 wt% Alparticles from the current collector foil were present. The delamination efficiency measured was 94%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes for the mechanical and solvent delamination was 86%.

Example 6

An aluminum foil (thickness 16 pm) coated with NCM containing 0.3 wt% Al typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 15 mm circular hole bottom sieve at a peripheral rotor speed of 4 m/s. 25.4 wt% of a fraction of <100 pm were obtained, which contained 0.46 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. The filter residue contained 0.3 wt% Al, as measured by XRF. Thus, no Al-particles from the current collector foil were present. The recovery of delaminate coating suitable for the coating of new electrodes measured was 86%. The resulting overall delamination efficiency for the mechanical and solvent delamination was 64%.

Example 7 (comparative)

An aluminum foil (thickness 16 pm) coated with NCM containing 0.3 wt% Al typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 2 mm circular hole bottom sieve at a peripheral rotor speed of 1.8 m/s. 63 wt% of a fraction of <100 pm were obtained, which contained 0.54 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. The filter residue contained 0.31 wt% Al, as measured by XRF. Thus, at most 0.01 wt% Alparticles from the current collector foil were present. The delamination efficiency measured was 77%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes for the mechanical and solvent delamination was 29%.

Example 8 (comparative)

An aluminum foil (thickness 16 pm) coated with NCM containing 0.3 wt% Al typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 4 mm circular hole bottom sieve at a peripheral rotor speed of 4 m/s. 51 wt% of a fraction of <100 pm were obtained, which contained 0.53 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. The filter residue contained 0.31 wt% Al, as measured by XRF. Thus, at most 0.01 wt% Alparticles from the current collector foil were present. The delamination efficiency measured was 72%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes for the mechanical and solvent delamination was 35%.

Example 9

An aluminum foil (thickness 16 pm) coated with NCM containing 0.3 wt% Al typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 4 mm circular hole bottom sieve at a peripheral rotor speed of 3 m/s. 50 wt% of a fraction of <100 pm were obtained, which contained 0.46 wt% Al, as measured by XRF.

7 g of the coarse material >100 pm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. The filter residue contained 0.33 wt% Al, as measured by XRF. Thus, at most 0.03 wt% Alparticles from the current collector foil were present. The delamination efficiency measured was 72%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes for the mechanical and solvent delamination was 36%.

Example 10

An aluminum foil (thickness 16 pm) coated with NCM containing 0.3 wt% Al typically employed in commercial lithium-ion batteries was treated in a cutting mill (Wanner c17.26 sv) equipped with a 4 mm circular hole bottom sieve at a peripheral rotor speed of 1.8 m/s. 28.4 wt% of a fraction of <100 pm were obtained, which contained 0.43 wt% Al, as measured by XRF. 7 g of the coarse material >100 gm were suspended in 28 g NMP and heated at 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 gm sieve. For analytical purposes, the sieved material <100 pm was finally filtered, washed first with NMP and then with deionized water, and dried. The filter residue contained 0.3 wt% Al, as measured by XRF. Thus, no Al-particles from the current collector foil were present. The delamination efficiency measured was 85%. The resulting overall delamination efficiency for the mechanical and solvent delamination was 61%.

The data obtained in the above examples are summarized in Table 1 .

Table 1

Comparative example

The data show that the detachment of the coating by dry milling in a cutting mill increases with increasing peripheral rotor speed v and with decreasing bottom sieve mesh diameter d of the cutting mill. The quotient q of peripheral rotor speed v and the sieve mesh diameter d can be correlated with the detachment of the coating R(D), and for the NCM-coated materials for the data given here can be expressed by the equation:

R(DNCM) = 0.062 q = 0.062 v/d

The data reported in Hanisch et al.: "In-Production Recycling of Active Materials from Lithium-Ion Battery Scraps", ECS Trans. 64 (2015) 131 -145 ("Hanisch"), and in Christian Hanisch et al.: "Recovery of Active Materials from Spent Lithium-Ion Electrodes and Electrode Production Rejects" in J. Hesselbach and C. Herrmann (eds.): "Globalized Solutions for Sustainability in Manufacturing: Proceedings of the 18th CIRP International Conference on Life Cycle Engineering, Technische Universitat Braunschweig, Braunschweig, Germany, May 2nd - 4th, 2011", Springer-Verlag, Berlin, Heidelberg 2011 , pp.85-89 ("Herrmann") also can be approximated by linear equations. However, the range of q values of the present disclosure and those shown in the references cover completely different ranges of q values.

In the present disclosure, the q values are in the range of from 100 to 1 ,000 [1/s], while the q range reported in Herrmann is from 600 to 5,000 [1/s], and the q range given in Hanisch is from 5,000 to 13,333 [1/s].

The different ranges can be shown in diagrams, as in Figure 1 a and b, which are diagrams of dry delamination efficiency R(D) in a cutting mill as a function of the quotient q of peripheral rotor speed v and bottom sieve mesh diameter d.

In case of the LFP-coated samples, the number of experiments is not sufficient to demonstrate such a correlation. What can be seen is that the amount of dry detachment is much lower for the LFP samples than for the NCM samples at similar q values. The higher the q value, the higher the mechanical stress exerted on the electrode pieces will be, and the more coating will be detached. The data in the table also show that below a value of q = 500 [1/s], no aluminum is detected in the coating delaminated by solvent treatment ("Al (wet)"). For NCM-coated samples, it has been found that at q < 800 [1/s], the dry detachment of the coating is below or equal to 50 wt%, at q < 500 [1/s], the dry detachment of the coating is below 30 wt%, and the aluminum content in the coating delaminated by a solvent treatment ("Al (wet)") is at most 0.01 wt%. Preferred are q values below 500 [1/s], which are obtainable by using low peripheral speeds below 4 m/s in the cutting mill, and a bottom sieve having a large mesh of 4 mm and more; or even q values below 300 [1/s], which are obtainable by using low peripheral speeds below 4 m/s in the cutting mill, and a bottom sieve having a large mesh of 15 mm and more. Hereby the dry detachment can be further reduced to below 20 wt%, or even below 10 wt%.

Example 11

In this example, an aluminum foil (thickness 16 pm) coated with LFP containing no Al as typically employed in commercial lithium-ion-batteries was treated in an IDEAL 2445CC cross-cutting mill. 2.8 wt% of a fraction having a particle size <100 pm and containing 0.1 w% Al (measured by XRF) was obtained. The coarse material >100 pm was delaminated as follows: 2.8 g of the coarse material >100 pm were suspended in 24.9 g NMP and heated to 120°C. The hot slurry was stirred with a glass blade stirrer at 300 rpm for 1 h. After cooling down to ambient temperature, the slurry was wet sieved using a 1 mm sieve to separate the foil pieces, and subsequently with a 100 pm sieve. For analytical purposes, the material having a particle size <100 pm was filtered, washed first with NMP and then with deionized water, and dried. In the filter residue, no Al could be detected by XRF. The delamination efficiency measured was 92%. The resulting overall recovery of delaminate coating suitable for the coating of new electrodes for the mechanical and solvent delamination was 89%.

The peripheral rotor speed for the cross-cutting mill employed in this example was estimated by the following method: a paper sheet of 11 mm width and 295 mm length was cut in the cross-cutting mill within 4 seconds. 74 cuttings having an average length of approx. 22 mm were obtained. The rotor diameter was estimated to be 30 mm, and the number of blades on the rotary knife was 4. From these data, a peripheral rotor speed of from 0.1 m/sec to at most 0.3 m/sec could be estimated. The corresponding q-value is below 1.5 [1/sec] with a d-value of approx. 240 mm.

List of reference numerals

20 cutting mill

21 rotor

22 rotor blade

23 stator

24 stator blade

25 separating mesh

26 discharge space

30 cross-cutting mill

31 rotor

32 circular knife

33 blade

34 rack

40 cross-cutting mill

41 rotor axe

42 circular knife

43 blade

44 shaft

Claims

1. A method of recycling electrode active material from alkali metal ion battery electrodes which comprise an electrode active material coated on a metal foil, the method comprising a. comminuting the electrodes using a cutting mill or a cross-cutting mill, wherein a milling chamber of the cutting mill or cross-cutting mill is separated from a discharge space of the cutting mill or cross-cutting mill by a mesh having openings of at least 3 mm width, and the cutting mill cross-cutting mill is operated at q < 800 [1/s], with q = v/d, v being the peripheral rotor speed of the cutting mill, and d being the diameter of the openings of the mesh, b. removing any particles having a length in at least two dimensions of less than 100 pm from the comminuted electrodes in a first separation step, c. subsequently treating the comminuted electrodes with a solvent able to dissolve a binder polymer present in the coating of the metal foil to delaminate the electrode active material from the metal foil, and to produce a slurry comprising dispersed electrode active material and pieces of metal foil, d. separating the pieces of metal foil from the slurry comprising dispersed electrode active material in a second separation step, e. optionally, providing a current collector metal foil and coating it with the slurry comprising dispersed electrode active material obtained from step d.

2. The method of claim 1 , wherein the milling chamber is separated from the discharge space by a mesh having openings of at least 4 mm width.

3. The method of claim 1 , wherein the milling chamber is separated from the discharge space by a mesh having openings of at least 15 mm width

4. The method of any one of claims 1 to 3, wherein the first separation step involves dry sieving, air classification, dry or wet cyclonic separation, wet sieving, or combinations thereof.

5. The method of any one of claims 1 to 4, wherein the second separation step involves wet sieving or wet cyclonic separation, or combinations thereof.

6. The method of any one of claims 1 to 5, wherein particles having a length in at least two dimensions of less than 100 pm are removed from the slurry obtained after step d) by sieving on a sieve screen with a fine mesh.

7. The method of any one of claims 1 to 5, wherein particles having a length in at least two dimensions of less than 100 pm are removed from the slurry obtained after step d) by employing wet cyclones (hydrocyclones).

8. The method of any one of claims 1 to 7, wherein pristine electrode active material and/or binder polymer and/or conductivity enhancing additives are added to the slurry obtained in step d) to adjust the composition of the slurry to match the specifications of a slurry for an alkali ion battery electrode coating.

9. The method of any one of claims 1 to 8, wherein the solvent comprises N-methyl-2-pyrrolidone (NMP).

10. The method of any one of claims 1 to 8, wherein the solvent comprises dimethyl sulfoxide (DMSO) and/or water.

11. The method of any one of claims 1 to 10, wherein the binder polymer comprises polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

12. The method of any one of claims 1 to 11 , wherein the electrode active material comprises LiNi_xMn_yCoi-_x-yO2 (NCM).

13. The method of any one of claims 1 to 11 , wherein the electrode active material comprises lithium iron phosphate (LFP).

14. The method of any one of claims 1 to 13, wherein the metal foil is comprised of aluminum or copper.