BATTERY RECYCLING

This invention relates generally to battery recycling. More specifically, although not exclusively, this invention relates to the recycling of lithium-ion battery materials.

Lithium ion batteries are widely used to power many portable electronics and electric vehicles. However, this type of battery has a finite lifetime and requires replacement after a certain period. The waste generated by lithium-ion batteries represents a significant problem for the environment if it is not recycled because lithium-ion batteries contain a number of heavy metals and toxic chemicals. Therefore, disposal in landfill may be hazardous to the environment, causing soil contamination and water pollution. In addition, there is an environmental cost to sourcing the materials required to produce lithium-ion batteries. There are also ethical concerns surrounding the mining of essential elements for use in the fabrication of lithium-ion batteries including lithium, cobalt, and nickel. Consequently, there are many benefits to recycling and re-using these battery materials including decreased environmental pollution, reduced demand on landfill, lessened demand on finite resources and decreased environmental and human costs in relation to mining virgin resources.

In general, lithium-ion batteries are formed from four essential components: anode, cathode, separator and electrolyte which complete the electrochemical cell. However, in order to safely package the four principal operative components it is also necessary to have a casing in which they are held. Further, various component layers may be provided (e.g. aluminium foil - cathode current collector, copper foil as the anode current collector). It will also be understood that different cathode and anode materials may be deployed, as well as different separators and electrolytes. As such, there is a recognised challenge in the recycling of lithium-ion cells.

Although different organisations have developed different methods for recycling, the, some or all of the steps involved may be generalised into the following categories: stabilisation, comminution, size separation, density separation, magnetic separation, hydrometallurgy, pyrometallurgy, and other steps (R. Sommerville et ai\ Sustainable Materials and Technologies 25 (2020) e00197).

Stabilisation is required before opening cells to prevent thermal runaway and product loss through fire. Thermal runaway is undesirable because this may lead to the synthesis and release of hot, toxic, and corrosive chemicals, and the loss of potentially retrievable components, such as electrolyte and plastic, to combustion. Stabilisation methods may include ohmic discharge, solution discharge, thermal pre-treatment, heat, electrolyte extraction.

Separation methods may be used to separate the components of the cell. The products of separation are plastics, separator and pouch materials, metal, steel casing, Ni and Al tabs, Cu and Al current collectors, and a “black mass” (a powdery fraction formed from crushing cells containing the electrodes or from crushing the electrodes).

Comminution is required to disassemble the cell and to access the components. Commonly used methods include shredding, milling, and/or high sheer mixing.

Size separation may be achieved through sieves, filters, cyclones, Magnetic separation is primarily used to remove steel casing material but can also be used to separate ferromagnetic electrode materials. Density separation is used to separate out the low density plastics and papers or high density metal casings from the mixed cell waste. This can be achieved using shaker tables, vibrating screens, a fluid of intermediate density, or air separation. Other separation methods include froth floatation, which exploits the difference in hydrophobicity between two materials, and electrostatic separation.

The black mass typically contains materials from the negative and positive electrodes; graphite, PVDF, carbon black, metal oxides, and some Al and Cu current collectors. The black mass is reclaimed for further processing such as metal dissolution and precipitation.

It has been reported that approximately 95% of Li-ion batteries ended up in landfill sites rather than being recycled (Heelan, J. et al. JOM 68, 2632-2638 (2016)). In 2019, only 5% of lithium-ion batteries were recycled in the European Union (Nature Energy 4 (2019) 253- 253). There is a clear need for more efficient and accessible recycling methods for lithium- ion battery recycling.

Accordingly, a first aspect of the invention provides a method in accordance with Claim 1.

A second aspect of the invention provides a method for recycling batteries, for example lithium ion battery material, the method comprising the following steps: i. comminution of battery material, e.g. lithium ion battery material, to produce a single fraction wherein >80 wt.%, e.g. >85 wt.%, or >90 wt.%, or >95 wt.% of the pieces have a maximum dimension in the range of less than or equal to 4.0mm; ii. separating the pieces using magnetic separation.

A third aspect of the invention provides apparatus in accordance with Claim 20.

It has been surprisingly found that magnetic separation of a single fraction of lithium-ion battery material, wherein >80 wt.%, e.g. >85 wt.%, or >90 wt.%, or >95 wt.% (e.g. >96 wt.%, or >97 wt.%, or >98 wt.%, or >99 wt.%, or 100 wt.%) of the pieces have a maximum dimension in the range of less than or equal to 4.0mm, supports high rates of electrode recovery. This is in comparison to magnetic separation of a single fraction of lithium ion battery material wherein >95 wt.% of the pieces have a maximum dimension in the range of greater than 4.0mm, for example, from 4.0mm to 8.0mm.

In embodiments, the method and apparatus comprises comminution of battery material to produce a single fraction wherein >80 wt.%, e.g. >85 wt.%, or >90 wt.%, or >95 wt.% (e.g. >96 wt.%, or >97 wt.%, or >98 wt.%, or >99 wt.%, or 100 wt.%) of the pieces have a maximum dimension in the range of 1.0mm to 4.0mm. In embodiments, the pieces may have a maximum dimension in the range of any one of 1.0, 1.1 , 1.2, 1.3, 1.4, 1.5, 1.6, 1.7,

1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7,

3.8, or 3.9 mm to any one of 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1 , 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, or 1.1 mm. In embodiments, the method comprises comminution of battery material to produce a single fraction wherein >80 wt.%, e.g. >85 wt.%, or >90 wt.%, or >95 wt.% (e.g. >96 wt.%, or >97 wt.%, or >98 wt.%, or >99 wt.%, or 100 wt.%) of the pieces have a maximum dimension in the range of 2.0mm to 4.0mm, for example, 2.8mm to 4.0mm.

As will be appreciated, the electrostatic separation step separates insulators from non insulating (conducting) materials. In the context of batteries, insulating materials may include the separator, parts of the pouch (for pouch cells) and so on.

Advantageously, the use of electrostatic separation, especially with a suitable size range material, has been shown to reduce the production of fines which is beneficial from a handling perspective, and may lead to benefits insofar as a reduction of fines limits potential human exposure to deleterious materials.

For example, previously deployed pneumatic density separation techniques may increase the amount of fines generated. In contrast, in our comminution steps we seek to provide a minimum particle size of 0.5mm, preferably 1mm, which we have found limits fine generation.

The succeeding magnetic separation stage separates magnetic and non-magnetic materials. In the context of batteries, the magnetic separation stage will separate the cathode materials (e.g. NCA, LMO, NMC, LFP) from the anode materials (e.g. graphite, LTO, silica etc).

Batteries typically comprise current collectors. In a lithium ion battery it is usual to have a copper foil as the anode current collector and a aluminium foil as the cathode current collector. In some cells (e.g. LTO cells) the anode current collector may also be aluminium. Beneficially, the anode current collect and the cathode current collector pieces will be separated by the magnetic separation stage (with the anode/cathode materials). This allows for the subsequent step of removing the current collector pieces from the respective anode and cathode streams.

Accordingly, the method and apparatus provides a final stage of separating current collector materials from active (electrode) materials. Final stage separation may be achieved by ultrasonic delamination (see Green Chemistry (2021), 23, 4710-4715, the contents of which are hereby incorporated by reference).

In embodiments, comminution of lithium ion battery material may be performed in a stabilised atmosphere, for example, an atmosphere that is substantially free from oxygen. In embodiments, comminution of battery material, e.g. lithium ion battery material, may be performed under a high flowrate of air, e.g. using a cyclone air mover. Additionally or alternatively, comminution of battery material, for example lithium ion battery material, may be performed under a water spray. In embodiments, comminution of battery material, for example lithium ion battery material, may be performed in a temperature controlled environment. Advantageously, the temperature may be controlled to limit the build-up of heat. In embodiments, comminution of lithium ion battery material comprises shredding the battery material. In embodiments, shredding the battery material may be performed using a low speed high torque shredder, for example comprising interdigitated blades or knives. Advantageously the use of low-speed, high-torque shredders can reduce dust and noise generation whilst reducing knife and drive component wear.

In embodiments, comminution of battery material, e.g. lithium ion battery material, comprises one or more of granulating, milling, and/or high sheer mixing. In embodiments, milling may be performed using a hammer mill. In embodiments, step i. of the method may be performed in ambient and/or dry conditions.

In embodiments, the method may comprise a single comminution step. In embodiments, the method may comprise a single comminution of lithium ion battery material to produce a single fraction wherein >80 wt.%, e.g. >85 wt.%, or >90 wt.%, or >95 wt.% of the pieces have a maximum dimension in the range of less than or equal to 4.0mm. Step i. of the method may be performed in one step, i.e. a single pass through apparatus to cause comminution.

Alternatively, the method may comprise multiple comminution steps. For example the method may comprise passing material through comminution apparatus multiple times to achieve a or the desired size range of materials. For example, a first pass may be deployed and a portion of the material emerging from the first pass (e.g. the larger size fraction), may be subjected to a second pass. Size separation (for example, sieving) may be used to separate the desired, smaller, fraction from the less desired, larger fraction, and the larger fraction may be subjected to a further comminution step.

The method further comprises step iv. removal of the electrolyte after step i. The pieces of comminuted battery material, e.g. lithium ion battery material, will comprise the components of a battery, e.g. lithium ion battery, including the electrolyte. Advantageously, removal of the electrolyte renders the material less hazardous. The resulting material is less toxic and less likely to catch fire or cause an explosion.

Step ii. of the method may be performed in dry conditions. This may be achieved by removing the electrolyte to provide dry material. It has been surprisingly found that magnetic separation under dry conditions is more efficient and provides a higher recovery in comparison to conditions wherein the electrolyte has not been removed.

In embodiments, the method may further comprise sieving the comminuted battery material, e.g. the comminuted lithium ion battery material, of step i, e.g. to remove fine powders. In embodiments, sieving the comminuted battery material, e.g. the comminuted lithium ion battery material, of step i. may be performed after step i. and before step ii. separating the pieces using magnetic separation.

The battery material may comprise pouch cell material, e.g. whole pouch cells. The battery material may comprise prismatic cell material, e.g. whole prismatic cells. The battery material may comprise cylindrical cell material, e.g. whole cylindrical cells.

The battery material may comprise lithium nickel cobalt aluminium oxides (NCA). In embodiments, the battery material may comprise lithium manganese oxide (LMO). The battery material may comprise LMO-NCA. The battery material may comprise or consist of LMO-NCA pouch cell material.

The anode may comprise graphite material.

The battery material may comprise different cathode and/or anode material. Cathode materials may be selected from Lithium Cobait Oxide for Lithium Cobaitate), Lithium Manganese Oxide (also known as spinel or Lithium Manganate), Lithium Iron Phosphate, as well as Lithium Nickel Manganese Cobalt (or NMC), Lithium Nickel Cobait Aluminium Oxide (or NCA) or mixtures. Anode materials may be selected from graphite, lithium titanate, silicon and tin and/or mixtures of two or more thereof.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms “may”, “and/or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is an apparatus for use in electrostatic separation for use in a method according to embodiments of the invention; and

Figure 2 is an apparatus for use in magnetic separation for use in a method according to embodiments of the invention.

In a first step lithium ion battery material was comminuted and dried to create a feed F of small particles where ca 90% of particles had a size in the range of 2.8 to 4 mm. This was performed in a slow speed high torque shredder having two shafts driven by a 4kW motor (sold under the trade mark U5 by Ulster Shredders Limited of Magherafelt, UK). Comminution was carried out at ambient temperatures. In an experiment using pouch cells (LMO-NCA cathodes) each cell was processed in less than 90 seconds.

In some embodiments, larger fractions from the first pass were passed through the shredder one or more times to achieve a required size range.

The material may sieved to achieve a feed F of the required size range.

Referring now to Figure 1 , there is shown an apparatus 1 for use in electrostatic separation for use in a method according to the invention. The apparatus 1 comprises a feed hopper 10, a vibratory feeder 11, an ionising electrode 12, an optional static electrode 13, an earthed titanium roll 14, and a brush 15. There is also shown a sample of the shredded cell feed F, the conductive material C, the insulative material J, and the optional middling material M that has been separated by the electrostatic separation apparatus 1.

In use, the feed F is fed into the feed hopper 10. The feed hopper 10 transfers the feed F onto the vibratory feeder 11, which in turn transfers the feed F onto the surface of the earthed titanium roll 14. The ionising electrode 12 causes the feed material F to become charged according to its conductive or dielectric characteristics as the earthed titanium roll 14 turns, for example in a clockwise direction. The conductive material C passes it’s charge onto the earthed roll, and is collected under the influence of the optional static electrode 13, or falls from the roll under the effect of gravity. The insulative material J remains attracted to the surface of the earthed titanium roll 14, and is removed from the surface of the earthed titanium roll 14 by the brush 15, which is in contact with the surface of the earthed titanium roll 14. The optional middling material M (which may result from materials being adhered together) remains attracted to the surface of the earthed titanium roll 14 for slightly longer than the conductive material C, but for less time than insulative material J. Consequently, the feed F is separated into three fractions: the conductive material C, the insulative material J, and the middling material M.

Example 1

10g of feed F having a maximum dimension of 2.8mm to 4mm is fed into the electrostatic separation apparatus 1. The electrodes of the electrostatic separation apparatus 1 had the following characteristics: 18 KeV, No static electrode, 50 RPM on the earthed roll. Electrostatic separation yielded the following results.

Referring now to Figure 2, there is shown an apparatus 2 for use in magnetic separation of a feed according to the invention. The apparatus 2 comprises a feed hopper 20, a vibratory feed 21, a magnetic roll 22, a rubber pulley belt 23, and a second pulley roll 24. The magnetic roll 22 may be a 300mm rare-earth permanent magnetic roll (e.g. a laboratory scale machine made by Bunting Magnetics Europe Limited of Berkhamstead UK). There is also shown a sample of the shredded cell feed F’, the magnetic material MF, the non-magnetic material NF, and the middling material P that has been separated using the magnetic separation apparatus 2.

In use, the feed F’ which is the conductive fraction separated in the electrostatic separation stage, is fed into the feed hopper 20 and subsequently into the vibratory feed 21. The feed F’ is then transferred to the rubber pulley belt 23, which moves by rotation of the drive roll 24 at a first end, and the unpowered magnetic roll 22 at a second end of the rubber pulley belt 23. Under the influence of the magnetic roll 22, the magnetic material MF remains attracted to the magnetic roll 22 whereas the non-magnetic material NF is not attracted to the magnetic roll 22. Consequently, the feed F is separated into three fractions: the magnetic material MF, the non-magnetic material NF, and the middling materiel P. The magnetic material MF comprises magnetic cathode material MC, and the non-magnetic material NF comprises non-magnetic anode material A.

Example 2

Two samples of feed F’ having a maximum dimension of 2.8mm to 4mm was fed into the magnetic separation apparatus 2. Magnetic separation yielded the following results.

Example 3

The following Examples relate to the grade and recovery of an LMO-NCA pouch cell battery. In this case material was comminuted to provide the following material to determine the efficiency of recovery of materials having different size ranges. The results were obtained using optical sorting and a mass balance.

It has been surprisingly shown that electrostatic/magnetic separation of a single fraction of lithium ion battery material, wherein >80 wt.%, e.g. >85 wt.%, or >90 wt.%, or >95 wt.% of the pieces have a maximum dimension in the range of less than or equal to 4.0mm, provides a cathode recovery of above 85% and an anode recovery of above 80%. This is in comparison to magnetic separation of a single fraction of lithium ion battery material wherein >80 wt.%, e.g. >85 wt.%, or >90 wt.%, or >95 wt.% of the pieces have a maximum dimension in the range of greater than 4.0mm, for example, from 4.0mm to 8.0mm.

It will be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.