Electrochemical apparatus for the recovery of lithium from electrode powder of lithium-ion batteries

Abstract

The invention relates to an electrochemical apparatus for the recovery of lithium from electrode powder of lithium-ion batteries, comprising a supply tank for an aqueous suspension of electrode powder, a pair of primary ducts, a pump, a receiving tank, a pair of secondary ducts and an electrolytic unit, which includes an anode, a cation exchange membrane and a cathode compartment.

Description

[0001] Electrochemical apparatus for the recovery of lithium from electrode powder of lithium-ion batteries

[0002] The present invention relates to an electrochemical apparatus for the recovery of lithium from electrode powders originating from cathode production plants or from production waste of lithium-ion batteries or from end-of-life lithium-ion batteries. Said electrochemical apparatus described in the present invention may also be configured for the production of hydrogen.

[0003] In an attempt to reduce the emission of polluting greenhouse gases and to promote more sustainable energy solutions, the use and consequent production of lithium-ion batteries and their components have increased exponentially in recent decades.

[0004] Therefore, the ever-increasing quantity of batteries used in today's society has led to an increased demand for lithium.

[0005] Mining extraction is currently the main source of lithium supply.

[0006] However, the continued exploitation of lithium mineral resources is leading to their rapid depletion. Furthermore, mining is a highly polluting and environmentally destructive process, as it requires large territorial extensions resulting in the destruction of natural ecosystems, and it requires intensive use of water resources for the extraction process and the treatment of the ore, gradually depleting water reserves.

[0007] This scenario makes the development of innovative technologies for lithium recovery crucial, in order to support the growing demand and reduce dependence on mining extraction.

[0008] In an attempt to address this urgent issue, it has been found that waste from cathode production plants, as well as from end-of-life lithium-ion batteries, can represent a valuable source of lithium. Currently, the processes used for recycling lithium-ion batteries are thermal (pyrometallurgical) and with such processes, lithium is lost in the melting slag. On the other hand, there are no available apparatuses on the market for the treatment of waste from the production of cathodes for lithium-ion batteries that allow the recovery of the lithium contained in such waste.

[0009] Conversely, recovering lithium from exhausted batteries and from the waste of their production not only reduces environmental pollution, but can also contribute to preserving natural resources and decreasing dependence on extractive practices, which are highly polluting and destructive for the environment.

[0010] However, lithium recovery represents a challenge in the recycling processes of end-of-life lithium-ion batteries and of lithium-ion battery production waste.

[0011] Firstly, lithium-ion batteries contain a variety of components in addition to lithium, such as cobalt, nickel, manganese and organic solvents and, therefore, separating lithium from these other components requires sophisticated and accurate processes as well as innovative apparatuses and systems. Furthermore, there are different chemistries and configurations of lithium-ion batteries, such as NMC, LFP and LCO, each with different compositions and structures, and this variety complicates the standardisation of recovery processes and of the related apparatuses and systems. Finally, lithium recovery must be economically sustainable, which means that the processes must be efficient, the related apparatuses must be industrially scalable, and the costs must be competitive compared with traditional mining extraction.

[0012] These combined factors make the recovery of lithium from end-of-life batteries and from the waste of their production complex and demanding, albeit essential for environmental sustainability and the reduction of dependence on mineral resources.

[0013] To date, the known industrial processes and related apparatuses, potentially applicable for the recovery of lithium from lithium-ion battery waste or from exhausted lithium-ion batteries, are of the hydrometallurgical type. On the other hand, with hydrometallurgical apparatuses, lithium must be recovered, therefore separated, from a solution containing all the other metals, salts and solvents contained in the batteries, as well as the reagents used during the hydrometallurgical extraction process. This complicates the recovery of lithium with a purity rate suitable for its marketing and to achieve this goal, costly purification operations by solvent extraction are required. In addition, due to the high solubility of lithium salts, it is necessary to concentrate the starting solution and / or add additional precipitating agents in order to induce their precipitation and thus recovery, with considerable energy expenditure.

[0014] These limitations in lithium recovery have also been considered by the recently approved European directive which sets a lithium recovery rate from end-of-life lithium-ion batteries of only 50% compared with a minimum rate of 90% for cobalt and nickel (to be achieved by 2027).

[0015] Examples of processes and electrochemical apparatuses for the recovery of lithium from end-of-life battery cathodes by means of a chemical oxidation reaction in solution are described in CN 116119637A and WO 2023 / 091087, in which lithium extraction takes place through the addition of oxidising agents such as persulphates (SiOs2"), chlorates (CIO ) or ferrocyanide [Fe(CN)6]3, which are reduced by oxidising the iron in the LiFePO4 cathode from Fe2to Fe3, promoting the release of lithium ions (Ei+) into the solution.

[0016] However, this approach presents some drawbacks. In fact, the redox mediators, although regenerable, may progressively degrade or generate by-products, making their replacement or periodic purification necessary.

[0017] Moreover, in the processes and apparatuses described in CN116119637A and WO 2023 / 091087 the cathodic material (EiFePO4) is treated while still adhered to the original aluminium current collector of the battery, directly employing the electrode sheets as active electrodes. However, this configuration proves difficult to apply on an industrial scale, where the standard treatment of end-of-life batteries involves crushing and processing the electrode powder obtained from grinding, making the recovery and direct use of intact electrodes unlikely. Another process that allows for the recovery of lithium from exhausted lithium-ion batteries, and from the waste of their production processes, is described in the scientific article "Aqueous electrochemical delithiation of cathode materials as a strategy to selectively recover lithium from waste lithium-ion batteries” Pier Giorgio Schiavi et al. Volume 88, 2024, Pages 144-153, ISSN 2095-4956, authored by the inventors of the present invention.

[0018] However, although said process is efficient, optimised and innovative for the recovery of lithium from lithium-ion battery waste, an electrochemical apparatus is required that allows this process to be exploited industrially, ensuring large-scale lithium recovery with high purity, while simultaneously reducing operational and environmental costs.

[0019] In view of these shortcomings of the known art, the aim is therefore to provide an apparatus that is industrially scalable and configured to enable the recovery of lithium from solid-state material, not only from cathodic sources but also from electrode powders of waste of and from exhausted batteries, without the need for separation of materials.

[0020] These and other needs are met by an electrochemical apparatus for the recovery of lithium from electrode powder of lithium-ion batteries as defined in the appended claim 1.

[0021] As will be shown in the experimental section, an apparatus according to the present invention is configured to implement a mechanism of Li extraction by direct electrochemical oxidation of the cathodic material of lithium-ion batteries contained in the electrode powder, whatever it may be (LiFePCU, LiCoCL, LiNiCL, LiNiaMnbCocC)2, LiNiaCobALCL, etc.). More specifically, the extraction mechanism implemented by the apparatus of the present invention does not require or provide the use of chemical oxidants, as surprisingly the oxidation can be achieved by means of a faradaic reaction directly through the application of an anodic potential to the material contained in the suspension of solid particles being fed; said faradaic reaction leads to the transfer of electrons, thus to a significant passage of current.

[0022] In addition, the apparatus of the present invention allows to overcome the limitations of the state of the art, in particular those associated with the extraction of lithium from high- performance cathodes, such as LiNiMnCoO . In such materials, the effective release of lithium requires the oxidation of transition metals, such as cobalt, from the Co3+to the Co4+state. However, commonly used redox mediators, such as S20s2', do not possess a sufficiently high oxidative potential to promote such transformation, rendering lithium extraction ineffective.

[0023] Within the context of the present invention, the expression “electrode powder of lithium-ion batteries” is intended to mean a pulverulent solid material obtained from the collection of waste from the production of cathodes for lithium-ion batteries, such as NMC (Nickel- Manganese-Cobalt), LFP (Lithium-Iron-Pho sphate) or LCO (Lithium-Cobalt-Oxide), or from disposal processes of end-of-life lithium-ion batteries. Typically, both production waste and end-of-life batteries are collected from various sources such as electric vehicles, electronic devices and energy storage systems. As regards exhausted batteries, they are usually dismantled to extract the various components and crushed into small pieces to release the electrode materials contained therein.

[0024] The composition of the electrode powder depends on the nature and structure of the waste or the exhausted batteries. In particular, the electrode powder may comprise cathodic material typically consisting of metal oxides such as lithium cobalt oxide (LiCoCh), lithium iron phosphate (LiFePCU), lithium nickel manganese cobalt oxide (NMC) or lithium nickel cobalt aluminium oxide (NCA).

[0025] Optionally, the electrode powder may also comprise anodic material, usually graphitic, but it may also include materials such as lithium titanate (LUTisOiz) or silicon.

[0026] Other polymeric materials may also be present, such as those constituting the separators - used to separate, in fact, the cathode from the anode -, as well as structures, housings and electrical connections.

[0027] Preferably, the electrochemical apparatus for the recovery of lithium from electrode powder of lithium-ion batteries, according to the present invention, comprises a supply tank, capable of containing an aqueous suspension of said electrode powder. Preferably, the electrochemical apparatus for the recovery of lithium from electrode powder of lithium-ion batteries, according to the present invention, comprises an electrolytic unit.

[0028] Said electrolytic unit may include an anode comprising a plate provided with an open serpentine groove.

[0029] Moreover, the electrolytic unit may include a cation exchange membrane having a first side abutting a face of the anode on which the open serpentine groove is exposed.

[0030] The electrolytic unit may further include a cathode compartment comprising a catalytic cathode suitable for the reduction of water and placed abutting a second side of the cation exchange membrane opposite to the first side, and a cathode plate adapted to support the catalytic cathode.

[0031] Moreover, preferably the electrochemical apparatus, according to the present invention, comprises a pair of primary ducts, each in fluid communication with the supply tank and the open serpentine groove of the anode.

[0032] The electrochemical apparatus, according to the present invention, may further comprise a pump, adapted to recirculate the aqueous suspension of electrode powder between the supply tank and the anode, through the pair of primary ducts.

[0033] The electrochemical apparatus, according to the present invention, may further comprise a receiving tank adapted to contain a LiOH solution produced at the cathode compartment of the electrolytic unit.

[0034] The electrochemical apparatus according to the present invention may further comprise a pair of secondary ducts, in fluid communication with the cathode compartment and the receiving tank, adapted to enable recirculation of the LiOH solution between the cathode compartment and the receiving tank. The electrochemical apparatus of the invention is preferably configured to carry out redox reactions that, on the one hand, involve the oxidation of metals (excluding lithium) present in the electrode powder to be treated, allowing lithium to selectively pass through the cation exchange membrane. On the other hand, the apparatus of the invention is configured to carry out electrolysis of water, with the formation of hydrogen and OH anions, which may give rise to the formation of LiOH.

[0035] Advantageously, the supply tank of the apparatus according to the invention allows maintaining a continuous, homogeneous and uniform supply of the aqueous suspension of electrode powder to the electrolytic unit. Furthermore, the supply tank allows maintaining an optimal concentration of the suspension, improving the efficiency of the recovery process and the overall reliability of the apparatus.

[0036] The apparatus according to the invention is preferably configured to achieve at the anode the oxidation of metals contained in the electrode powder (excluding lithium), allowing the selective extraction of lithium (delithiation), according to the following reaction: (reaction 1)

[0037] In other words, the apparatus according to an embodiment of the invention enables the solid- state oxidation of the metals contained in the aqueous suspension of electrode powder, thus making it possible to avoid the dissolution of such metals in the aqueous phase and consequently ensuring the selectivity of the passage only of lithium cations through the cation exchange membrane.

[0038] The serpentine groove of the anodic plate specifically allows feeding the apparatus of the invention with the suspension of electrode powder, that is to say, a solid particulate material. In particular, the adoption of a serpentine groove in the apparatus of the present invention makes it possible to define a forced path for the fed suspension, such as to maximise the impacts between the solid particles contained in the suspension itself and the conductive walls of the serpentine, which serves as a current collector. The increase in the number of collisions favours an extension of the electrical contact area between the active material (electrode powder) and the collector, consequently increasing the quantity of material participating in the reaction. As will be illustrated in the experimental section, such a configuration surprisingly enables the initiation of localised faradaic reactions, which generate electron transfer and thus the production of current. Therefore, as the frequency and effectiveness of such interactions increase, the electrochemical activity and the current delivered by the system also increase.

[0039] In the state of the art, the use of serpentines in electrolysers has been described but solely for the purpose of homogeneous transport of electrode material. In the apparatus of the present invention, the serpentine anode acts as a dynamic reactor where mechanical interaction (collision) functionally becomes electrochemical. In fact, by generating controlled impacts between the suspended solid particles and the walls of the serpentine, which serve as currentcarrying surfaces, lithium extraction is achieved.

[0040] Moreover, the anodic plate provided with an open serpentine groove maximises the contact surface between the anode and the aqueous suspension of electrode powder, improving the efficiency of the electrochemical reaction and promoting a faster and more complete recovery of lithium. In addition, the provision of a serpentine groove on the anode allows obtaining a greater contact surface between the anode and the cation exchange membrane, enhancing the selectivity of the membrane for lithium ions and thereby increasing the purity of the obtainable LiOH.

[0041] Advantageously, the cation exchange membrane separates the anode from the cathode compartment, allowing the selective passage of lithium ions and preventing the passage of other species, reducing contamination from other ions. This makes it possible to increase the purity of the LiOH solution produced and thus to improve the quality of the product obtainable by means of the apparatus of the invention.

[0042] The provision of a cathode compartment equipped with a catalytic cathode allows carrying out the water reduction reaction, according to the following reaction: (reaction 2) The catalytic cathode is thus configured for the production of hydrogen and hydroxyls (OH ). In particular, the hydroxyls (OH ) obtainable by means of the apparatus of the invention may be advantageously employed for the recovery of lithium in the form of LiOH.

[0043] At the same time, according to an embodiment, the apparatus of the invention allows the accumulation of H2, which is a valuable by-product and may be used in other industrial applications, sold as an additional product, or used internally as an energy source, creating an additional revenue stream.

[0044] Moreover, the cathode plate, adapted to support the catalytic cathode, ensures a stable structure and optimises the contact between the cathode and the cation exchange membrane, increasing the efficiency of water reduction and lithium recovery.

[0045] The primary ducts ensure a smooth communication between the supply tank and the groove of the anode and ensure a fluid and controlled circulation of the aqueous suspension, ensuring a uniform and constant flow of the suspension and preventing the sedimentation of the electrode powder.

[0046] The pump facilitates the recirculation of the suspension, improving the contact between the electrode powder and the anode, thus increasing the efficiency of the apparatus. Indeed, such continuous recirculation avoids the sedimentation of the powder, maintaining a homogeneous suspension.

[0047] The receiving tank is configured to contain the LiOH solution obtainable in the cathode compartment, facilitating the collection and management of the final product.

[0048] The secondary ducts enable the recirculation of the LiOH solution between the cathode compartment and the receiving tank, improving the efficiency of the collection and allowing the LiOH solution to be gradually concentrated. In this way, the apparatus of the invention may operate in a substantially continuous mode. Therefore, the electrochemical apparatus according to the invention may be conveniently configured so as to treat continuous flows of aqueous suspension of electrode powder, thus being capable of handling large quantities of waste.

[0049] Further features and advantages of the invention are described below and defined in the dependent claims.

[0050] All the claims form an integral part of the present description.

[0051] Preferably, the receiving tank of the apparatus of the invention is also suitable for containing H2 in gaseous form.

[0052] Advantageously, the hydrogen generable through the apparatus of the invention is efficiently collected and stored in the receiving tank. This allows the use of hydrogen as an energy resource, improving the overall energy efficiency of the system. Furthermore, this reduces the risks associated with the dispersion of gaseous hydrogen into the working environment, improving the operational safety of the apparatus and, therefore, facilitates the management of hydrogen, making it available for further applications in a safe manner.

[0053] In the apparatus according to the invention, the plate of the anode may be made of titanium.

[0054] Indeed, it has been found that titanium is highly resistant to corrosion in aqueous and acidic environments, and it also possesses excellent mechanical strength, which ensures the robustness and structural stability of the anode during operations carried out by the apparatus, even under electrochemical stress conditions. Such characteristics of titanium allow a long duration and stability of the anode, reducing the need for maintenance of the electrochemical apparatus. Titanium also offers good electrical conductivity, necessary to facilitate the electrochemical reactions implementable with the apparatus of the invention. It has thus been found that the use of titanium in the anode may improve the efficiency of mass transfer and the rate of electrochemical reactions, leading to a higher efficiency of lithium recovery of the apparatus of the invention. Furthermore, it has been verified that titanium is compatible with many electrolytes and materials present in the electrode powders, minimising undesired reactions and ensuring the purity of the obtainable LiOH.

[0055] Alternatively to titanium, the plate of the anode may be made of graphite.

[0056] Indeed, although graphite is characterised by lower mechanical properties compared to titanium, it may also be used as a material in the manufacture of the anodic plate with open serpentine.

[0057] In fact, all materials that are electrochemically inert within the potential range of interest and poor catalysts of the water oxidation reaction — which could compete with the oxidation of metals (reaction 1) for lithium extraction — are good candidates from the electrochemical standpoint for the manufacture of this anodic component.

[0058] Preferably, in the apparatus of the invention the cation exchange membrane is a membrane selective to the passage of cations only, including Li+.

[0059] Advantageously, this allows a significant selectivity of the membrane towards the lithium cation, ensuring that only Li+ions pass through the membrane and thus preventing the passage of other ions. This significantly increases the purity of the obtainable LiOH and prevents the hydroxyls generated in the cathode compartment from migrating towards the anode, reacting (for example, according to the reaction: 4OH' —> 2H2O + O2 + e-) and being consumed to the detriment of the formation of LiOH. Furthermore, this minimises undesired reactions, improving the overall efficiency of the electrochemical apparatus. The use of a highly selective membrane also makes it possible to maintain stable operating conditions, improving the consistency and reproducibility of the operations implementable by the apparatus of the invention.

[0060] In particular, the inventors have selected some materials preferably employable for making the membrane selective to the passage of cations only, including Li+. In particular, it is preferable to use cation exchange membranes resistant to alkaline environments, such as commercially available membranes including FKL-PK-130 and Fumasep FKL-PK-75, or cation exchange membranes for chlor-alkali applications based on PFSA, such as GLN417. Preferably, the catalytic cathode of the cathode compartment in the apparatus of the invention comprises a catalyst for the electrochemical reduction of water, selected from the group that includes PGM (Platinum Group Metals) catalysts - for example platinum-based (Pt), iridium (Ir), rhodium (Rh), palladium (Pd) -, noble metals (such as Au, Ag) and transition metals (such as Co, Ni, Fe, Cu, Sn).

[0061] It has indeed been verified by the inventors that this group of materials increases the efficiency of the electrochemical reduction of water in the apparatus of the invention, improving the production of hydrogen and OH anions. In fact, an efficient water reduction leads to a greater production of OH anions, which react with Li+ions to form LiOH. This increases the purity and quantity of obtainable LiOH, enhancing the efficiency of the apparatus.

[0062] In particular, catalysts such as platinum, iridium and other noble metals are highly resistant to corrosion and harsh operating conditions, ensuring a long lifetime of the catalytic cathode and stability over time.

[0063] Moreover, within the scope of the present invention, it has been verified that the use of these catalysts reduces the overpotential required for the water reduction reaction. This means that electrolysis through the electrochemical apparatus of the invention may take place at lower voltages, reducing energy consumption and improving the energy efficiency of the apparatus.

[0064] Furthermore, the possibility of choosing from a variety of catalysts (PGM, noble metals and transition metals) allows optimisation of the catalytic cathode according to specific operating needs and costs, improving the configuration versatility of the apparatus of the invention.

[0065] Preferably, the cathode plate of the cathode compartment of the apparatus of the invention is made of steel or of plastics stable in alkaline environments selected from the group comprising polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE) and polypropylene (PP). Advantageously, these plastics, compared to metallic materials (steel), being electrically insulating, prevent direct contact between the anode and cathode, thus avoiding short circuits.

[0066] Preferably, the electrochemical apparatus according to the invention is configured to apply a constant potential difference between the anode and the catalytic cathode comprised between 1.5 and 5 V, more preferably between 1.5 and 3.5 V (for example 2 V, 2.5 V, 3 V, 3.5 V), and / or to apply a constant current such that a maximum potential difference of 5 V, more preferably 3.5 V (for example 2 V, 2.5 V, 3 V, 3.5 V) between the anode and the cathode is not exceeded.

[0067] Within the scope of the present invention, it has been tested that this potential difference advantageously allows a precise management of electrochemical reactions at the anode and cathode, avoiding over-oxidations or undesired reactions that could compromise the efficiency of the electrochemical apparatus and the purity of the obtainable product. It has been particularly observed that at a potential between 1.5 and 5 V, it is possible to selectively oxidise the metals constituting the lithiated oxides (for example NMC, LFP, LCO) while limiting the oxidation of other species present in the electrode powder (such as conductive carbons, graphite) and of water (2H2O —> O2 + 4H+). This is particularly important in order to maximise the energy efficiency of the process achievable by the apparatus of the invention. The present inventors have observed that by configuring the apparatus of the invention to operate within this potential range, the oxidation of these metals may be efficiently favoured.

[0068] Furthermore, within the scope of the present invention it has been tested that a constant and well-defined potential difference and / or current contributes to the stability of the process, reducing variations and fluctuations that could negatively affect the efficiency of the electrochemical apparatus and the quality of lithium recovery. At the same time, it has also been tested that by operating within this potential range or at a current that prevents exceeding a potential of 5 V, more preferably of 3.5 V, the risk of degradation of the anode and cathode materials is reduced, prolonging the operational life of the apparatus of the invention and reducing maintenance costs.

[0069] Preferably, the electrochemical apparatus according to the invention is configured to treat an aqueous suspension of electrode powder with a concentration comprised between 1 and 0.01 g / ml.

[0070] It has also been observed that configuring the electrochemical apparatus of the invention to operate with such a concentration of the aqueous suspension of electrode powder ensures an ideal balance between the availability of active materials and the fluidity of the suspension, improving the overall efficiency of the apparatus.

[0071] Within the scope of the present invention, it has in fact been tested that such a concentration range allows the optimisation of the electrochemical reaction implementable by the apparatus and represents the right compromise to reduce the risk of oversaturation or excessive dilution, thereby ensuring optimal contact between the electrode powder particles and the surface of the electrodes. Moreover, such concentration range of the aqueous suspension of electrode powder facilitates the management of the suspension, preventing sedimentation or aggregation problems of the particles, and maintaining stable operating conditions. The inventors have also verified that this specific concentration range maximises mass transfer and reactivity, increasing the concentration of the obtainable LiOH and facilitating the final recovery of lithium as LiOH salt, for example through crystallisation of the solution obtainable by means of the apparatus of the invention.

[0072] This configuration also reduces the operating costs of the electrochemical apparatus of the invention, optimising the use of the aqueous solvent and minimising the need for frequent maintenance.

[0073] Preferably, in the electrochemical apparatus according to the invention, the receiving tank is configured to draw H2 by means of a valve applied at an apical portion of the receiving tank.

[0074] Advantageously, this allows an efficient collection of the gaseous hydrogen obtainable with the apparatus of the invention, improving the management and use of this valuable by- product.

[0075] In particular, the valve allows the controlled release of hydrogen, increasing operational safety and reducing the risk of gas accumulation in the apparatus, which could cause dangerous pressures. Moreover, the possibility of drawing hydrogen facilitates its storage or integration into other industrial apparatuses, making the operability of the apparatus more sustainable and economically advantageous. This configuration also contributes to maintaining stable operating conditions in the receiving tank, ensuring optimal management of the obtainable products and by-products.

[0076] The electrochemical apparatus of the invention may comprise a plurality of juxtaposed electrolytic units and fluidically and electrically connected to one another in series.

[0077] Said plurality of electrolytic units is preferably configured to be electrically and fluidically connected so as to provide a constant potential difference between 1.5 and 5 V or such that a maximum potential difference of 5 V is not exceeded.

[0078] Within the scope of the present invention, the constant potential difference between 1.5 and 5 V or the maximum potential difference of 5 V when a constant current is applied is to be understood as the potential difference at the ends each individual electrolytic unit.

[0079] Within the scope of the present invention, it has been observed that the juxtaposition of a plurality of electrolytic units facilitates the scalability of the apparatus, allowing the addition of further units to increase treatment capacity without having to redesign an entire industrial apparatus. Moreover, this modular approach offers operational flexibility, enabling the apparatus of the invention to adapt to variations in the quantity of electrode powder to be treated.

[0080] The inventors have also observed that the fluidic connection between the units ensures a continuous and uniform flow of the aqueous suspension of electrode powder through the entire apparatus equipped with multiple electrolytic units, improving the homogeneity of the treatment of the electrode powder and the quality of the obtainable final product. Furthermore, the series electrical connection ensures balanced distribution of the current, optimising electrochemical reactivity in each unit and ensuring stable and consistent apparatus performance.

[0081] In addition, it has been found that this configuration of the apparatus of the invention also improves maintenance and management, since any interventions may be carried out on individual units without interrupting the operability of the apparatus. Overall, the integration of a plurality of electrolytic units in series makes the electrochemical apparatus of the invention more efficient, scalable, flexible and easy to manage, increasing productivity and reducing operating costs.

[0082] The functional and structural characteristics of some preferred embodiments of an electrolyser device for lithium recovery according to the invention will now be described.

[0083] Before describing in detail a plurality of embodiments of the invention, it should be clarified that the invention is not limited in its application to the constructional details and the configuration of the components presented in the following description or illustrated in the drawings. The invention can assume other embodiments and of being practised or implemented in various ways. It should also be understood that the phraseology and terminology are for descriptive purposes only and should not be construed as limiting.

[0084] An embodiment is shown by way of illustrative and non-limiting example in the appended Figure 1, wherein the reference numeral 100 denotes an electrochemical apparatus for the recovery of lithium from electrode powder of lithium-ion batteries according to the present invention.

[0085] Figure 1 shows an exploded view of the electrochemical apparatus 100.

[0086] The electrochemical apparatus 100 comprises a supply tank 101 configured to contain an aqueous suspension of electrode powder. The supply tank 101 supplies the aqueous suspension of electrode powder continuously and stably, maintaining an optimal concentration of the suspension to improve the lithium recovery efficiency of the electrochemical apparatus 100.

[0087] The electrochemical apparatus 100 comprises an electrolytic unit 110 responsible for carrying out the electrochemical reactions required to isolate lithium from the other components of the electrode powder and convert it into a storable and reusable form, such as LiOH.

[0088] In particular, the electrolytic unit 110 includes an anode 111, a cation exchange membrane

[0089] 114, and a cathode compartment 115 comprising a catalytic cathode 116 and a cathode plate 117 adapted to support the catalytic cathode 116.

[0090] The anode 111 comprises a plate 112 provided with an open serpentine groove 113.

[0091] The cation exchange membrane 114 has a first side abutting the face of the anode 111 on which the open serpentine groove 113 is exposed. The second side of the cation exchange membrane 114, opposite the first side, is placed abutting a side of the cathode compartment

[0092] 115.

[0093] The electrolytic unit 110 is configured to use electrical energy to induce redox reactions.

[0094] Specifically, the electrochemical apparatus 100 is configured to convey the aqueous suspension of electrode powder from the supply tank 101 to the anode 111, which is made for example of titanium, and oxidises the components of the electrode powder. In particular, the configuration of the anode 111, which includes a plate 112 provided with an open serpentine groove 113, increases the contact surface between the anode 111 itself and the suspension, improving the reactivity and efficiency of the electrochemical apparatus 100.

[0095] The catalytic cathode 116 may comprise, for example, a PGM catalyst which may consist of platinum in the form of nanoparticles distributed on a conductive support such as activated carbon or on metallic substrates, or alternatively the PGM catalyst may consist of iridium oxide (TrO?) on a conductive substrate; or again it may be based on palladium in the form of nanoparticles, possibly alloyed with other metals such as silver or gold, on supports such as activated carbon or thin films.

[0096] Thanks to its composition, the catalytic cathode 116 reduces water, producing hydrogen and OH anions.

[0097] The cation exchange membrane 114, placed between the anode 111 and the catalytic cathode 116, is configured to allow the selective passage of lithium ions, preventing the passage of other negatively charged ionic species.

[0098] Therefore, this configuration of the electrolytic unit 110 of the electrochemical apparatus 100 ensures that lithium is effectively separated from other metals present in the electrode powder and collected as a LiOH solution.

[0099] The electrochemical apparatus 100 provides a pump (not illustrated) and a pair of primary ducts 105. In particular, the pump recirculates the aqueous suspension of electrode powder between the supply tank 101 and the anode 111 through the pair of primary ducts 105, ensuring a uniform distribution of the suspension and preventing sedimentation.

[0100] Moreover, the electrochemical apparatus 100 includes a receiving tank 102, configured to contain the LiOH solution obtainable in the cathode compartment 115.

[0101] The receiving tank 102 may also be provided with a valve 102a at an apical portion, allowing controlled drawing of gaseous H2, improving the management and safety of the apparatus 100.

[0102] The receiving tank 102 may also be configured to contain the LiOH solution with a concentration, for example, of 1 M.

[0103] In addition, a pair of secondary ducts 106 fluidically connects the cathode compartment 115 to the receiving tank 102, allowing the recirculation of the LiOH solution and ensuring a stable concentration of the final product. Depending on the composition of the incoming electrode powder, it will be possible to determine the residence time of the suspension inside the anode 111 and the cathode compartment 115. Consequently, it will be possible to adjust the flow rates of the two fluids in the primary and secondary ducts in order to ensure the residence time necessary for the completion of the reactions. In this way, it will be possible to discharge and feed the supply tank 101 and the receiving tank 102 at a predetermined flow rate, thus enabling the continuous operation of the apparatus 100.

[0104] The entire electrochemical apparatus 100 may be configured to treat an aqueous suspension of electrode powder with a concentration comprised between 1 and 0.01 g / ml, optimising the efficiency of the lithium recovery operations.

[0105] Furthermore, the electrochemical apparatus 100 may include a plurality of electrolytic units 110 juxtaposed and connected to one another in series, increasing the capacity and operational efficiency of the apparatus 100 on an industrial scale.

[0106] The electrochemical apparatus 100 is configured to apply a constant potential difference comprised between 1.5 and 5 V (for example 2 V, 2.5 V, 3 V, 3.5 V, 4 V, 4.5 V) between the anode 111 and the catalytic cathode 116, and / or to apply a constant current such that a maximum potential difference of 5 V, more preferably 3.5 V, is not exceeded between the anode 111 and the catalytic cathode 116.

[0107] When the apparatus 100 includes a plurality of electrolytic units 110, the electrical series connection is configured so as to generate at the end of each electrolytic unit 110 a constant potential difference comprised between 1.5 and 5 V or a constant current such that a maximum potential difference of 5 V is not exceeded.

[0108] In order to apply the potential difference or constant current to the electrodes, the electrochemical apparatus 100 may comprise an external circuit (not illustrated), which includes a power supply source, such as a direct current generator or a battery. The external circuit is configured to provide a constant voltage or current, depending on the operational requirements of the electrochemical apparatus.

[0109] For example, the power supply may be an adjustable direct current (DC) generator, which allows precise setting of the desired potential difference between the anode 111 and the catalytic cathode 116. Alternatively, batteries or specific DC power supplies for industrial applications may be used.

[0110] The terminals of the power supply are connected to the electrodes, for example, via conductive cables. Specifically, preferably the positive terminal (+) is connected to the anode, while the negative terminal (-) is connected to the cathode. This enables the circulation of current through the circuit and the electrodes.

[0111] The potential difference applied between the anode 111 and the catalytic cathode 116 may be adjustable via the direct current generator, maintaining a constant value comprised between 1.5 and 5 V. This adjustment is appropriate to control the electrochemical reactions and ensure the selective oxidation of metals other than lithium and therefore the proper overall operation of the electrochemical apparatus 100.

[0112] Alternatively, the generator may be configured to supply a constant current, automatically adjusting the voltage to maintain the desired current. This is particularly useful to ensure that the potential difference does not exceed 5 V, thereby protecting the integrity of the electrodes and optimising the operability of the apparatus 100.

[0113] The external circuit may be equipped with monitoring instruments to measure voltage and current in real time, allowing operators to control operating conditions and make any necessary adjustments. Additionally, safety devices, such as fuses and switches, may be installed to prevent overvoltage or overcurrent that could damage the apparatus.

[0114] Once the external circuit is configured, the potential difference or direct current is applied to the electrodes (anode 111 and catalytic cathode 116), initiating redox reactions within the electrolytic unit 110. The electric current causes the oxidation of the electrode powder at the anode 111 and the reduction of water at the cathode 116, producing hydrogen and OH anions. The cation exchange membrane 114 allows the selective passage of lithium ions, which are then collected as a LiOH solution in the receiving tank 102. According to an aspect of the invention, an electrochemical apparatus 100, according to one or more of the embodiments described and illustrated above, is fed with a suspension of electrode powder, for example of the type previously described.

[0115] The electrochemical apparatus 100, in this way, ensures precise control of electrochemical reactions, making it possible to recover lithium and ensuring the purity of the obtainable final product. In addition, the possible use of an adjustable power supply allows the apparatus 100 to be adapted to different operating conditions and to optimise its performance on a large industrial scale.

[0116] Various aspects and embodiments of an electrochemical apparatus according to the invention have been described. It is intended that each embodiment may be combined with any other embodiment. Furthermore, the invention is not limited to the described embodiments but may be varied within the scope defined by the appended claims.

[0117] EXPERIMENTAL EXAMPLE

[0118] The experimental part below is provided solely for illustrative and non-limiting purposes of the scope of the invention as defined by the appended claims. The experimental part refers to the attached drawings, in which:

[0119] - Figure 2a shows the trend of the current recorded during a potential scan from 0.5 to 2.0 V, using as delithiation process electrodes a titanium sheet anode (reference “titanium sheet”) and a serpentine-grooved anode (reference “serpentine”), according to an embodiment of the present invention;

[0120] - Figure 2b shows a photograph comparing on the right the geometric features of the titanium sheet (right) used in the experimental example, and on the left the anode with serpentine groove according to an embodiment of the present invention (left).

[0121] Materials and Methods

[0122] To evaluate the effectiveness of the apparatus of the invention, lithium extraction experiments were conducted from a suspension of electrode powder by linear sweep voltammetry (LSV) in a three-electrode configuration.

[0123] Said suspension of electrode powder was obtained by dispersing electrode powder (thus containing both cathodic and anodic material from an end-of-life lithium-ion battery) in an aqueous solution, with a powder concentration of 0.1 g / L.

[0124] The experiment was conducted using two different electrode configurations:

[0125] - a flat titanium sheet, shown in Figure 2b on the right, used as a conventional anode according to known technique; the dimensions of the titanium sheet were specifically selected to match the surface area of the serpentine, so as to allow a direct comparison between the two electrode configurations;

[0126] - a titanium serpentine anode according to an embodiment of the present invention, having a surface area equivalent to that of the titanium sheet, and designed to interact dynamically with the suspension and to act as a reactive current collector.

[0127] Both configurations - sheet and serpentine - were tested individually as working electrodes in an electrochemical apparatus as described previously, equipped with a cation exchange membrane (Fumasep FKL-PK-130) having a first side abutting the serpentine groove of the anode. A platinum mesh electrode was used as counter electrode.

[0128] During each experiment, the concentration of the electrode suspension remained the same. A variable potential was then applied in LSV mode, from 0.5 V to 2.0 V versus an Ag / AgCl electrode, recording the resulting current as a function of the applied potential to compare the current-potential response generated in both cases and evaluate the charge transfer efficiency between the solid particles and the electrode under analysis.

[0129] Results

[0130] As shown in Figure 2a, surprisingly the serpentine anode configuration according to the present invention generates a significantly higher current throughout the entire potential range (0.5-2.0 V) compared with the titanium sheet. In particular, in the case of the serpentine, oxidation peaks indicative of a real faradaic reaction are observed, occurring thanks to the contact between the cathodic powder particles and the conductive surface of the serpentine electrode. On the contrary, in the sheet configuration, the current intensity is noticeably reduced and lacks characteristic peaks attributable to delithiation processes; without being bound by theory, this suggests that the current detected in the sheet configuration is almost exclusively attributable to the oxidation of water present in the suspension and not to electrode particle-anode interaction.

[0131] These results demonstrate that the apparatus according to the present invention provides a technical advantage over the known solutions in the prior art. In particular, surprisingly, the geometry of the anode, which promotes repeated impacts between the particles and the conductive walls, in synergy with the other features of the apparatus, enables better charge transfer, and thus greater efficiency in the lithium extraction process from electrode material that would otherwise be discarded. Such superior performance is achieved without the use of additives or redox mediators, making the apparatus more effective and simpler to implement, as well as less expensive from a chemical standpoint.

Claims

CLAIMS1. Electrochemical apparatus (100) for the recovery of lithium from electrode powder of lithium-ion batteries comprising:- a supply tank (101), adapted to contain an aqueous suspension of said electrode powder,- an electrolyte unit (110) that includes: an anode (111), comprising a plate (112) provided with an open serpentine groove (113); a cation exchange membrane (114), having a first side abutting the face of said anode (111) on which said open serpentine groove (113) is exposed; and a cathode compartment (115), comprising: a catalytic cathode (116) suitable for the reduction of water, said catalytic cathode being placed close to a second side of the cation exchange membrane (114) opposite the first side; and a cathode plate (117) adapted to support the catalytic cathode (116); a pair of primary ducts (105), each being in fluid communication with said supply tank (101) and said open serpentine groove (113) of the anode (111); a pump, designed to recirculate the aqueous suspension of electrode powder between the supply tank (101) and the anode (111), through said pair of primary ducts (105); receiving tank (102) adapted to contain a LiOH solution produced in the cathode compartment (115) of the electrolytic unit (110); and a pair of secondary ducts (106), in fluid communication with the cathode compartment (115) and said receiving tank (102), adapted to enable recirculation of said LiOH solution between the cathode compartment (115) and the receiving tank (102).

2. Apparatus according to claim 1, wherein the receiving tank (102) is also adapted to contain H2 in gaseous form.

3. Apparatus according to any one of claims 1 or 2, wherein the plate (112) of the anode(111) is made of titanium.

4. Apparatus according to any of the previous claims, wherein the cation exchange membrane (114) is a membrane selective to the passage of cations only, including Li+.

5. Apparatus according to any one of the preceding claims, wherein the catalytic cathode (116) comprises a catalyst for the electro-chemical reduction of water, chosen from the group that includes PGM catalysts, noble metals and transition metals.

6. Apparatus according to any of the preceding claims, wherein the cathode plate (117) is made of steel or of plastics stable in alkaline environments chosen from the group comprising PEEK, PTFE and PP.

7. Apparatus according to any one of the preceding claims, configured to apply a constant potential difference of between 1.5 and 5 V be-tween the anode (111) and the catalytic cathode (116), and / or to apply a constant current such that a maximum potential difference of 5 V is not exceeded between the anode (111) and the catalytic cathode (116).

8. Apparatus according to any of the preceding claims, configured to process an aqueous suspension of electrode powder with a concentration between 1 and 0.01 g / mL.

9. Apparatus according to any one of the preceding claims, wherein the receiving tank (102) is configured to spill H2 by means of a valve (102a) applied at an apical portion of the receiving tank (102).

10. Apparatus according to any one of the preceding claims, comprising a plurality of electrolytic units (110) juxtaposed and fluidically and electrically connected to each other in series, wherein said plurality of electrolytic units (110) is configured to be electrically and fluidically connected so as to provide a constant potential difference between 1.5 V and 5 V or a constant current such that a maximum potential difference of 5 V is not exceeded.

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