Methods and systems for recycling lithium-ion battery cathodes

Abstract

Methods and systems for recycling a material of a spent cathode of a lithium-ion battery are disclosed. One method includes mixing an input stream including a lithium metal oxide compound derived from the spent cathode with an acidic stream in an acid leaching unit, mixing a first portion of a basic stream with a first in loop solution in a precipitation unit, and producing the acidic stream and the basic stream in an electrochemical reactor by a salt splitting reaction of a lithium salt. Another method includes providing a three-chamber reactor, where the three-chamber reactor includes an anode chamber formed by an anode and a first ion exchange membrane; a cathode chamber formed by a second ion exchange membrane and a cathode; and a middle chamber formed between the anode chamber and the cathode chamber, where the middle chamber includes a porous solid electrolyte including ion conducting polymer particles functionalized with sulfonate groups. The system includes a three-chamber reactor, an acid leaching unit, a precipitation unit, and a solid accumulator.

Description

ATTORNEY DOCKET NO. 17500-275W01CLIENT REF. NO. 2024-105-PCTMETHODS AND SYSTEMS FOR RECYCLING LITHIUM-ION BATTERY CATHODESBACKGROUND

[0001] Lithium-ion batteries (LIBs) have reshaped everyday life since their discovery and commercialization and are playing increasingly important roles in renewable energy storage and transportation decarbonization to mitigate climate change. However, their rapidly-growing deployments in recent years face major challenges such as the management of spent waste batteries and the limited resources to meet global demands for new battery production. While spent LIBs contain valuable lithium and transition metals such as Co, Ni, and Mn in the cathode, only a small fraction of LIBs are currently recycled due to technical and economic limitations compared to that of the lead-acid battery industry which reaches more than a 99% recycling rate. Fundamental research and technological development in LIB recycling has, therefore, become an urgent need for sustainable growth and development of the LIB industry.

[0002] A key challenge in the commercialization of LIB recycling technology involves the continuous consumption of chemicals (such as acids and bases) and the generation of waste. Moreover, current recycling methods result in severe waste generation (such as NaOH, Na2SO4, NHL, etc.) that needs to be further treated before its discharge to the environment. Accordingly, there exists a need for LIB recycling methods and systems that consume less chemicals and produce less waste.SUMMARY

[0003] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In one aspect, embodiments disclosed herein relate to a method for recycling a material of a spent cathode of a lithium-ion battery. The method includes mixing an input stream including a lithium metal oxide compound derived from the spent cathode with an acidic stream in an acid leaching unit to decompose the lithium metal oxide,thereby providing a first in loop solution including a lithium salt and a metal compound; mixing a first portion of a basic stream with the first in loop solution in a precipitation unit to separate the metal compound as a solid metal compound from a second in loop solution including the lithium salt; feeding the second in loop solution to an electrochemical reactor; producing the acidic stream and the basic stream in the electrochemical reactor by a salt splitting reaction of the lithium salt, where the basic stream includes ionic lithium derived from the lithium salt and the acidic stream includes an anion derived from the lithium salt; and collecting the solid metal compound and the ionic lithium, where the solid metal compound and the ionic lithium are, respectively, first and second recycled materials.

[0005] In another aspect, embodiments disclosed herein relate to a method for recycling a spent cathode of a lithium-ion battery using a three-chamber reactor. The method includes providing a three-chamber reactor, where the three-chamber reactor includes an anode chamber formed by an anode, where the anode includes an anode catalyst for oxidation, and a first ion exchange membrane; a cathode chamber formed by a second ion exchange membrane and a cathode, where the cathode includes a cathode catalyst for reduction; and a middle chamber formed between the anode chamber and the cathode chamber, where the middle chamber includes a porous solid electrolyte including ion conducting polymer particles functionalized with sulfonate groups. The method further includes recycling the spent cathode of the lithium-ion battery by supplying the three-chamber reactor with an internal reducing agent stream to the anode chamber, an oxidizing agent stream to the cathode chamber, and an input stream of lithium sulphate to the middle chamber; applying a voltage to the three-chamber reactor to obtain sulfuric acid and lithium hydroxide from the three-chamber reactor by splitting the input stream of lithium sulphate; acid leaching the spent cathode of the lithium-ion battery with the sulfuric acid to obtain a stream of transition metal sulphate solution; precipitating at least one transition metal from the transition metal sulphate solution with a first portion of the lithium hydroxide to obtain a first recycled product stream including a recycled transition metal hydroxide product, and an output stream of lithium sulphate; obtaining a second recycled product stream including a second portion of the lithium hydroxide, and optionally repeating the recycling operation by providing the output stream of lithium sulphate to the middle chamber to serve as theinput stream of lithium sulphate, where a third portion of the lithium hydroxide is optionally recirculated in the cathode chamber.

[0006] In yet another aspect, embodiments disclosed herein relate to a system for recycling a spent cathode of a lithium-ion battery. The system includes a three-chamber reactor including an anode chamber formed by an anode, where the anode includes an anode catalyst for oxidation, and a first ion exchange membrane; a cathode chamber formed by a second ion exchange membrane and a cathode, where the cathode includes a cathode catalyst for reduction; and a middle chamber formed between the anode chamber and the cathode chamber, where the middle chamber includes a porous solid electrolyte including ion conducting polymer particles. The system further includes an oxidizing agent stream fluidically coupled to the cathode chamber, an internal reducing agent stream fluidically coupled to the anode chamber, a lithium salt stream fluidically coupled to the middle chamber and optionally a replenishing stream including the lithium salt fluidically coupled to the middle chamber, an acid leaching unit fluidically coupled to the three-chamber reactor, a precipitation unit fluidically coupled to the three-chamber reactor and the acid leaching unit, a basic stream fluidically coupling the three-chamber reactor and the acid leaching unit, an acidic stream fluidically coupling the three-chamber reactor to the acid leaching unit, and a solid accumulator coupled to the precipitation unit, where a lithium metal oxide compound of the spent cathode of the lithium-ion battery is provided to the acid leaching unit.

[0007] Other aspects and advantages of the claimed subject matter will be apparent from the following description and appended claims.BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 schematically illustrates a self-looped electrochemical method for recycling a material of a spent cathode of a lithium-ion battery in accordance with one or more embodiments.

[0009] FIG. 2 schematically illustrates a three-chamber PSE reactor for recycling a material of a spent cathode of a lithium-ion battery in accordance with one or more embodiments.

[0010] FIG. 3 schematically illustrates a three-chamber PSE reactor for acid and LiOH generation in accordance with one or more embodiments.

[0011] FIG. 4 schematically illustrates a traditional hydrometallurgy method for recycling a material of a spent cathode of a lithium-ion battery.

[0012] FIG. 5 shows the FEi., of a three-chamber PSE reactor and the pH of acids generated in the middle chamber at 400 mA current under different Li2SO4 input flow rates in accordance with one or more embodiments.

[0013] FIG. 6 shows Li+concentration as a function of electrolysis duration in the middle chamber output, cathode chamber output, and the Li+mass balance during one full cycle in accordance with one or more embodiments.

[0014] FIG. 7 shows the pH of the acidic stream from the middle chamber and the basic stream from the cathode chamber as a function of time including the amount of LiOH produced during one full cycle in accordance with one or more embodiments.

[0015] FIG. 8 shows the LiOH solution concentration obtained from the three- chamber PSE reactor over time in accordance with one or more embodiments.

[0016] FIG. 9 shows the pH diagram cobalt precipitation with LiOH in accordance with one or more embodiments.

[0017] FIG. 10 shows the conversion rates of proton utilization, cobalt and lithium precipitation, and overall recovery rates over one cycle in accordance with one or more embodiments.

[0018] FIG. 11 is the powder XRD patterns of recycled lithium and cobalt in accordance with one or more embodiments.

[0019] FIG. 12 shows the stability, cell voltage, and FEi., of a three-chamber PSE reactor based on the LiOH produced in accordance with one or more embodiments.

[0020] FIG. 13 shows the cell voltage of a three-chamber PSE reactor and transport efficiency over time in accordance with one or more embodiments.

[0021] FIG. 14 shows recovery efficiencies of metals recycled from NMC in accordance with one or more embodiments.

[0022] FIG. 15 shows the powder XRD patterns of recycled transition metal oxides after annealing in accordance with one or more embodiments.

[0023] FIG. 16 schematically illustrates a three-chamber PSE reactor in accordance with one or more embodiments.

[0024] FIG. 17 schematically illustrates a conventional two-chamber reactor with a CEM.

[0025] FIG. 18 shows the I- V curves of a three-chamber PSE reactor in accordance with one or more embodiments compared to a conventional two-chamber reactor with a CEM.

[0026] FIG. 19 shows the Li+crossover FE vs. the electrolysis current density of a three-chamber PSE reactor in accordance with one or more embodiments compared to a conventional two-chamber reactor with a CEM.

[0027] FIG. 20 schematically illustrates a conventional two-chamber reactor with a PEM.

[0028] FIG. 21 shows the I-V curves of a conventional two-chamber reactor with a PEM compared to a conventional two-chamber reactor with a CEM.

[0029] FIG. 22 shows the Li+crossover FE vs. the electrolysis current density of a conventional two-chamber reactor with a CEM compared to a conventional two-chamber reactor with a PEM.

[0030] FIG. 23 schematically illustrates a comparative three-chamber reactor with sand.

[0031] FIG. 24 shows the I-V curves of a three-chamber PSE reactor in accordance with one or more embodiments compared to a three-chamber reactor with sand.

[0032] FIG. 25 shows the Li+crossover FEs at 100 mAcm'2for a three-chamber PSE reactor in accordance with one or more embodiments compared to a three- chamber reactor with sand.

[0033] FIG. 26 schematically illustrates a comparative three-chamber PSE reactor without a CEM.

[0034] FIG. 27 shows the I-V curves of a three-chamber PSE reactor in accordance with one or more embodiments compared to a three-chamber PSE reactor without a CEM.

[0035] FIG. 28 shows the Li+crossover FE vs. the electrolysis current density of a three-chamber PSE reactor in accordance with one or more embodiments compared to a three-chamber PSE reactor without a CEM.

[0036] FIG. 29 schematically illustrates a three-chamber PSE reactor in accordance with one or more embodiments.

[0037] FIG. 30 shows the I-V curves of three-chamber PSE reactors in accordance with one or more embodiments.DETAILED DESCRIPTION

[0038] In the following detailed description of embodiments of the disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. Embodiments described herein may be used in combination with each other.

[0039] In one aspect, embodiments disclosed herein relate to a three-chamber reactor. The three-chamber reactor may include an anode chamber, a cathode chamber, and a middle chamber formed between the anode chamber and the cathode chamber.

[0040] In another aspect, embodiments disclosed herein relate to a system for recycling a spent cathode of a lithium-ion battery. The system may include the three-chamberreactor, a reducing agent stream fluidically coupled to the anode chamber of the three- chamber reactor, an oxidizing agent stream fluidically coupled to the cathode chamber of the three-chamber reactor and an input stream of lithium sulphate fluidically coupled to the middle chamber. The system may further include an acid leaching unit fluidically coupled to the three-chamber reactor and a precipitation unit fluidically coupled to the three-chamber reactor and the acid leaching unit. The system may yet further include a first recycled product stream fluidically coupled to a three chamber reactor and a second recycled product stream fluidically coupled to the precipitation unit.

[0041] In yet another aspect, embodiments disclosed herein relate to a method that includes applying a voltage to the three-chamber reactor, supplying the reducing agent stream to the anode chamber, supplying the oxidizing agent stream to the cathode chamber, and supplying an input stream of lithium sulphate to the middle chamber. After applying the aforementioned elements to the three-chamber reactor, the method may further include performing a recycling operation of a spent cathode of a lithium- ion battery using the acid leaching unit and the precipitation unit to obtain the first recycled product stream from the three-chamber reactor and a second recycled product stream from the precipitation unit.

[0042] In still yet another aspect, embodiments herein relate to a method for recycling a material of a spent cathode of a lithium-ion battery includes mixing an input stream comprising a lithium metal oxide compound with an acidic stream in an acid leaching unit to decompose the lithium metal oxide thereby providing a first in loop solution comprising a lithium salt and a metal compound, wherein the lithium metal oxide compound is derived from the spent cathode, and mixing a first portion of a basic stream with the first in loop solution in a precipitation unit to separate the metal compound as a solid metal compound from a second in loop solution comprising the lithium salt. The method may further include feeding the second in loop solution to an electrochemical reactor; and producing the acidic stream and the basic stream in the electrochemical reactor by a salt splitting reaction of the lithium salt, wherein the basic stream comprises ionic lithium derived from the lithium salt and the acidic stream comprises an anion derived from the lithium salt. The method may further include collecting the solid metal compound and the ionic lithium, wherein the solid metal compound and the ionic lithium are, respectively, first and second recycled materials. The method may furtherinclude priming the electrochemical reactor with an initial out of loop solution of the lithium salt before: mixing the input stream with the acidic stream, mixing the basic stream with the first in loop solution, and feeding the second in loop solution to the electrochemical reactor. The lithium salt may include or be lithium sulphate. The metal may include or be one or more transition metals. The metal may be selected from the group consisting of nickel, manganese, cobalt, and combinations thereof.

[0043] According to one or more embodiments, a method for recycling a material of a spent cathode of a lithium-ion battery is disclosed. The method includes mixing an input stream including a lithium metal oxide compound derived from the spent cathode with an acidic stream in an acid leaching unit to decompose the lithium metal oxide, thereby providing a first in loop solution including a lithium salt and a metal compound; mixing a first portion of a basic stream with the first in loop solution in a precipitation unit to separate the metal compound as a solid metal compound from a second in loop solution including the lithium salt; feeding the second in loop solution to an electrochemical reactor; producing the acidic stream and the basic stream in the electrochemical reactor by a salt splitting reaction of the lithium salt, where the basic stream includes ionic lithium derived from the lithium salt and the acidic stream includes an anion derived from the lithium salt; and collecting the solid metal compound and the ionic lithium, where the solid metal compound and the ionic lithium are, respectively, first and second recycled materials. The method may include priming the electrochemical reactor with an initial out of loop solution of the lithium salt before mixing the input stream with the acidic stream, mixing the first portion of the basic stream with the first in loop solution, and feeding the second in loop solution to the electrochemical reactor. The method may further include periodically supplying the electrochemical reactor with a replenishing stream including the lithium salt. The lithium salt may be lithium sulphate. Mixing the input stream with the acidic stream in the acid leaching unit may further include mixing an external reducing agent stream with the input stream and the acidic stream, where the external reducing agent stream may include hydrogen peroxide. The metal compound may be a transition metal, and the transition metal may be selected from the group consisting of nickel, manganese, cobalt, and combinations thereof. The electrochemical reactor may include a three- chamber reactor with an anode chamber, a cathode chamber, and a middle chamberformed between the anode chamber and the cathode chamber. Producing the acidic stream and the basic stream in the electrochemical reactor by a salt splitting reaction of the lithium salt may include feeding an oxidizing agent stream to the cathode chamber, feeding an internal reducing agent stream to the anode chamber, and applying a voltage across a cathode in the cathode chamber and an anode in the anode chamber. The oxidizing agent stream may include water and the internal reducing agent stream may include hydrogen produced in the cathode chamber. The input stream, the oxidizing agent stream, the external reducing agent stream, and the internal reducing agent stream may define an exclusive set of chemical streams that are provided to a recycling reactor system including the three-chamber reactor, the acid leaching unit, and the precipitation unit, whereby the recycling reactor system is self-sustaining. The voltage may be supplied by a renewable energy source. The anode chamber may be formed by an anode and a first ion exchange membrane, where the anode includes an anode catalyst for oxidation. The cathode chamber may be formed by a second ion exchange membrane and a cathode, where the cathode includes a cathode catalyst for reduction. The first ion exchange membrane may be proton conducting. The first ion exchange membrane may be a proton exchange membrane (PEM). The second ion exchange membrane may be lithium ion conducting. The second ion exchange membrane may be a cation exchange membrane (CEM). The middle chamber may include a porous solid electrolyte. The porous solid electrolyte may include ion conducting polymer particles. When the lithium salt is lithium sulphate, the ion conducting particles may be functionalized with sulfonate groups. The anode catalyst may be active for catalyzing a hydrogen oxidation reaction or an oxygen evolution reaction. The cathode catalyst may be active for catalyzing a hydrogen evolution reaction.

[0044] FIG. 1 schematically illustrates a method 100 according to one or more embodiments for recycling a material of a spent cathode 104 of a lithium-ion battery 102. The method comprises dismantling a spent lithium-ion battery 102, decomposing the spent cathode material 104 with an optional external reducing agent 105 a to form an input stream 105 comprising a lithium metal oxide compound, mixing the input stream 105 in an acid leaching unit 106 with an acidic stream 116 to decompose the lithium metal oxide compound and form a first in loop solution 108 comprising a lithium salt and a metal compound, mixing a first portion of a basic stream 120a withthe first in loop solution 108 in a precipitation unit 110 to separate the metal compound, forming a second in loop solution 112 comprising the lithium salt and a first recycled material 122, feeding the second in loop solution 112 to an electrochemical reactor 114 and applying a voltage from an energy source 118 to electrochemically split the lithium salt producing a basic stream 120 comprising ionic lithium and an acidic stream 116 comprising an anion derived from the lithium salt. As shown in FIG. 1, the resulting acidic stream 116 is fed back into the acidic leaching unit 106 and the basic stream 120 is split into the first portion of the basic stream 120a and a second portion of the basic stream 120b, where the first portion of the basic stream 102a is fed to the precipitation unit and the second portion of the basic stream 120b is fed to a solid accumulation unit (not pictured) to produce solid lithium hydroxide as a second recycled product 124. The first recycled product 122 and the second recycled product 124 are then used to form new lithium-ion batteries 126.

[0045] According to one or more embodiments, a method for recycling a spent cathode of a lithium-ion battery using a three-chamber reactor is disclosed. The method includes providing a three-chamber reactor, where the three-chamber reactor includes an anode chamber formed by an anode, where the anode includes an anode catalyst for oxidation, and a first ion exchange membrane; a cathode chamber formed by a second ion exchange membrane and a cathode, where the cathode includes a cathode catalyst for reduction; and a middle chamber formed between the anode chamber and the cathode chamber, where the middle chamber includes a porous solid electrolyte including ion conducting polymer particles functionalized with sulfonate groups. The method further includes recycling the spent cathode of the lithium-ion battery by supplying the three-chamber reactor with an internal reducing agent stream to the anode chamber, an oxidizing agent stream to the cathode chamber, and an input stream of lithium sulphate to the middle chamber; applying a voltage to the three-chamber reactor to obtain sulfuric acid and lithium hydroxide from the three-chamber reactor by splitting the input stream of lithium sulphate; acid leaching the spent cathode of the lithium-ion battery with the sulfuric acid to obtain a stream of transition metal sulphate solution; precipitating at least one transition metal from the transition metal sulphate solution with a first portion of the lithium hydroxide to obtain a first recycled product stream including a recycled transition metal hydroxide product, and an output streamof lithium sulphate; and obtaining a second recycled product stream including a second portion of the lithium hydroxide. The anode catalyst may be active for catalyzing a hydrogen oxidation reaction or an oxygen evolution reaction and the internal reducing agent stream may be a stream of hydrogen or water. The cathode catalyst may be active for catalyzing a hydrogen evolution reaction and the oxidizing agent stream may be water. The recycling operation may be repeated by providing the output stream of lithium sulphate to the middle chamber to serve as the input stream of lithium sulfate. The recycling operation may be repeated while recirculating a third portion of the lithium hydroxide in the cathode chamber. Acid leaching the spent cathode of the lithium-ion battery may include providing an external reducing agent for the acid leaching to the sulfuric acid and the spent cathode, where the external reducing agent for the acid leaching optionally includes hydrogen peroxide. The recycling operation may include obtaining an amount of protons through an oxidation reaction at the anode chamber using the internal reducing agent stream and the anode catalyst; obtaining hydrogen and an amount of hydroxide ions through a reduction reaction at the cathode chamber using the oxidizing agent stream and the cathode catalyst, where the amount of hydroxide ions equals the amount of protons; and electrochemically separating the lithium sulphate into lithium ions and sulphate ions in the middle chamber by electrolysis, where the voltage to the three-chamber reactor creates an electric field that transports a portion of the protons from the anode chamber through the first cation exchange membrane to the middle chamber and displaces a portion of lithium ions in the middle chamber through the second cation exchange membrane into the cathode chamber such that the lithium ions react with the hydroxide ions in the cathode chamber to produce the lithium hydroxide and the sulphate ions react with the protons in the middle chamber to produce the sulfuric acid. The hydrogen obtained from the cathode chamber may be provided as the internal reducing agent stream to the anode chamber. The first ion exchange membrane may be proton conducting. The first ion exchange membrane may be a proton exchange membrane. The second ion exchange membrane may be lithium ion conducting. The second ion exchange membrane may be a cation exchange membrane.

[0046] FIG. 2 schematically illustrates a method for recycling a spent cathode of a lithium-ion battery according to one or more embodiments, the method comprisingproviding a three-chamber reactor 200 with an anode chamber 202 with an anode catalyst 204 and a first ion exchange membrane 206 that is a proton conducting membrane, a middle chamber 208 comprising a porous solid electrolyte, a second ion exchange membrane 210 that is a lithium ion conducting membrane, and a cathode chamber 214 comprising a cathode catalyst 221, where an input stream of lithium sulphate 220 derived from a spent cathode of a lithium-ion battery is fed into the middle chamber 208, an internal reducing agent stream 224 is fed into the anode chamber 202, and an oxidizing agent stream 226 is fed into the cathode chamber 214 and a voltage 222 is applied across the anode catalyst 204 and the cathode catalyst 212 to electrochemically split the lithium sulphate into lithium ions and sulfate anions, producing an acidic stream 216 and a basic stream 218.

[0047] In one or more embodiments, the external reducing agent may be mixed with the input stream and the acidic stream in the acid leaching unit in order to enhance the efficiency of the acid leaching process. The external reducing agent may include or be hydrogen peroxide.

[0048] The electrochemical reactor may include a three-chamber reactor comprising an anode chamber, a cathode chamber, and a middle chamber formed between the cathode chamber. The method for recycling a material of a spent cathode of a lithium-ion battery may further include producing the acidic stream and the basic stream in the electrochemical reactor comprises feeding an oxidizing agent stream to the cathode chamber, feeding an internal reducing agent stream to the anode chamber, and applying a voltage across a cathode in the cathode chamber and an anode in the anode chamber. The oxidizing agent stream may include water and the internal reducing agent stream comprises hydrogen produced in the cathode chamber. The lithium metal oxide stream, the external reducing agent stream, the oxidizing agent stream, and the internal reducing agent stream may define an exclusive set of chemical streams that are provided a recycling reactor system including the three-chamber reactor, the acid leaching unit, and the precipitation unit, whereby the recycling reactor system is self-sustaining. The voltage may be supplied by a renewable energy source.

[0049] According to one or more embodiments, a system for recycling a spent cathode of a lithium-ion battery is disclosed. The system includes a three-chamber reactor including an anode chamber formed by an anode, where the anode includes an anodecatalyst for oxidation, and a first ion exchange membrane; a cathode chamber formed by a second ion exchange membrane and a cathode, where the cathode includes a cathode catalyst for reduction; and a middle chamber formed between the anode chamber and the cathode chamber, where the middle chamber includes a porous solid electrolyte including ion conducting polymer particles. The system further includes an oxidizing agent stream fluidically coupled to the cathode chamber, a lithium salt stream fluidically coupled to the middle chamber, an acid leaching unit fluidically coupled to the three-chamber reactor, a precipitation unit fluidically coupled to the three-chamber reactor and the acid leaching unit, a basic stream fluidically coupling the three-chamber reactor and the acid leaching unit, an acidic stream fluidically coupling the three- chamber reactor to the acid leaching unit, and a solid accumulator coupled to the precipitation unit, where a lithium metal oxide compound of the spent cathode of the lithium-ion battery is provided to the acid leaching unit. The system may further include an external reducing agent stream fluidically coupled to the acid leaching unit, where the external reducing agent stream optionally includes hydrogen peroxide. The basic stream may be separated into a first basic stream and a second basic stream, where the first basic stream is fluidically coupled to the precipitation unit and the second basic stream is fluidically coupled to a liquid accumulator, a solid accumulator, or an evaporation unit. The anode catalyst may be active for catalyzing a hydrogen oxidation reaction or an oxygen evolution reaction and the internal reducing agent stream may be a stream of hydrogen or water. The cathode catalyst may be active for catalyzing a hydrogen evolution reaction and the oxidizing agent stream may be a stream of water. The first ion exchange membrane may be proton conducting. The first ion exchange membrane may be a proton exchange membrane. The second ion exchange membrane may be lithium ion conducting. The second ion exchange membrane may be a cation exchange membrane. The cathode catalyst may include a platinum on carbon (Pt / C) catalyst on a carbon cloth electrode. The anode catalyst may include a platinum on carbon (Pt / C) catalyst on a gas diffusion layer electrode. The ion conducting polymer particles may be functionalized with sulfonate groups. The system may further include a replenishing stream including the lithium salt fluidically coupled to the system.

[0050] The anode chamber may be formed by an anode and a first ion exchange membrane, and the anode chamber may include an anode catalyst for oxidation. Thecathode chamber may be formed by a second ion exchange membrane and a cathode, and the cathode chamber may include a cathode catalyst for reduction. The middle chamber may include a porous solid electrolyte including ion conducting polymer particles. The ion conducting particles may be functionalized with sulfonate groups. A person of ordinary skill in the art will appreciate that alternative ion-conducting polymers or resins may be used in the middle chamber.

[0051] In one or more embodiments, the anode catalyst may be active for catalyzing a hydrogen oxidation reaction (HOR). To do so, the anode may include a platinum on carbon (Pt / C) catalyst on a gas diffusion layer electrode (e.g., 20% platinum on Carbon XC-72). The first ion exchange membrane, forming one wall of the anode chamber, may be proton conducting. In addition, the cathode catalyst may be active for catalyzing a hydrogen evolution reaction (HER). To do so, the cathode catalyst may include a platinum on carbon (Pt / C) catalyst on a carbon cloth electrode. The second ion exchange membrane, forming one wall of the cathode chamber, may be lithium ion conducting.

[0052] In one or more embodiments, the internal reducing agent stream may be a stream of hydrogen, while the oxidizing agent stream may be a stream of water. A person of ordinary skill in the art will appreciate that alternative reducing agent streams and oxidizing agent streams may be used.

[0053] Hydrogen and hydroxide ions may be obtained through a reduction reaction at the cathode chamber using the oxidizing agent stream and the cathode catalyst, after applying the voltage to the three-chamber device and supplying the oxidizing agent stream to the cathode chamber. In addition, protons may be obtained through an oxidation reaction at the anode chamber using the internal reducing agent stream and the anode catalyst after supplying the oxidizing agent stream to the anode chamber. Due to the electrochemical reactions at the anode and the cathode, the amount of hydroxide ions generally equals the amount of protons that are obtained. Within the middle chamber, the input stream of lithium sulphate may be electrochemically separated, or split, into lithium ions and sulphate ions using electrolysis. The voltage applied to the three-chamber reactor may create an electric field that transports a portion of the protons from the anode chamber through the first cation exchange membrane to the middle chamber while displacing a portion of lithium ions in the middle chamberthrough the second cation exchange membrane into the cathode chamber. In the cathode chamber, lithium ions may react with hydroxide ions to produce the lithium hydroxide. In the middle chamber, the sulphate ions may react with the protons from the anode to produce sulfuric acid.

[0054] The spent cathode of the lithium-ion battery may be supplied to the acid leaching unit along with the sulfuric acid from the middle chamber to produce a stream of transition metal sulphate solution. The transition metal may be precipitated from the transition metal sulphate solution using the precipitation unit and a first portion of the lithium hydroxide to obtain the first recycled product stream. In this case, the first recycled product stream may include a recycled transition metal hydroxide product. From the same reaction, an output stream of lithium sulphate may be obtained. A second portion of the lithium hydroxide may be isolated to obtain the second recycled product stream.

[0055] The recycling operation may be repeated by providing the output stream of lithium sulphate, obtained from the precipitation unit, to the middle chamber to serve as the input stream of lithium sulphate. In this way, the necessary components to drive the chemical reactions of the recycling operation are generated in-situ and reused, forming a “self-looped” system. However, the initial cycle may involve supplying a small investment of lithium sulphate to begin. As another example of the self-looped aspect of the methods and systems of the present disclosure, the hydrogen obtained from the cathode chamber may be provided as the internal reducing agent stream to the anode chamber. In addition, the recycling operation may be repeated while recirculating a third portion of the lithium hydroxide in the cathode chamber. Doing so may lower the interfacial concentration gradient across the second ion exchange membrane and into the cathode chamber.

[0056] In one or more embodiments, acid leaching the spent cathode may involve providing hydrogen peroxide as an external reducing agent to the sulfuric acid and spent cathode. However, beyond hydrogen peroxide, the methods and systems of the present disclosure may be utilized without the need of providing any additional chemical streams. In some embodiments, a replenishing stream may be fluidically coupled to the three-chamber reactor. The replenishing stream may comprise lithium salt, one or more reducing agents, an oxidizing agent, an acidic solution, a basic solution, or somecombination thereof, to periodically resupply the system and balance the chemical reactions.

[0057] As described above, the voltage applied to the three-chamber reactor may come from renewable sources, such as solar energy, wind power, hydroelectric plants, and geothermal energy systems. In this way, embodiments of the present disclosure avoid the use of additional chemicals beyond the initial investment of lithium sulphate (and possibly hydrogen peroxide) and also avoid the use of scarce energy resources.EXAMPLESMaterials and Chemicals

[0058] Lithium sulfate (Li2SO4, L6375-500 g), LiCoCh powder (97%, 014049-30), Nafion-117 solution (527084-25 mL), Hydrogen peroxide (H2O2, 30%, 1.07209.2500), cation exchange resin Dowex 50W X8 (50-100 mesh, 44509-100g) and sand (50-70 mesh) were purchased from Sigma Aldrich. Pt / C powder, Hydrophilic carbon cloth (ELAT-Hydrophilic Plain Cloth) electrode, hydrophobic gas diffusion layer carbon paper (GDL, Sigracet 28 BC), Nafion-117 membrane (PEM), and Nafion N2100TX membrane (used as CEM, can be replaced by ePTFE-reinforced Nafion) were purchased from Fuel Cell Store. NMC powder (LiNiMnCoCh) was purchased from MTI corporation. IrCh electrode was purchased from the Dioxide Materials. Millipore water (18.2 MQ cm) was used throughout all experiments.Preparation of Spent LCO Cathode

[0059] Spent LCO cathode, delithiated LiCoO2, was obtained by the electrochemical delithiation of the commercial LCO using a pouch-cell Li-ion battery configuration. Around 50 mg of LCO was well dispersed on aluminum foil as the positive electrode of the battery, and a piece of lithium metal was used as both the negative electrode and reference. A polymer separator soaked with organic electrolyte (1 M LiPFe in EC / DEC) was sandwiched by the LCO and Li metal electrodes. The delithiation process was conducted under a constant current of 0.2 mA towards a cutoff voltage at 4.3V. The Spent LCO cathode was then extracted from the pouch-cell setup andwashed with H2O and isopropanol each for several times, and dried in a vacuum oven overnight.Preparation of Pt / C Electrodes for HER Reaction

[0060] 40 mg active catalyst (Pt / C) and 160 pL of Nafion-117 binder solution were mixed with 4 mL of 2-propanol (Sigma- Aldrich). After sonication in ice water for 30 min, the obtained homogeneous ink was air-brushed onto a 5 *5-cm2hydrophilic carbon cloth electrode at 60 °C. Then the as-prepared electrode was hot-pressed on the cation exchange membrane at 90 °C for 10 min.Preparation of Pt / C Electrodes for HOR Reaction

[0061] The procedure of fabrication Pt / C anodes for HOR reaction followed the same procedure to prepare the cathode electrode disclosed above, except the gas diffusion layer (GDL) electrode was used. After the sonication of the mixture of 40 mg active catalyst (Pt / C), 160 pL of Nafion-117 binder, and 4 mL of 2-propanol, the obtained homogeneous ink was air-brushed onto a 5x5-cm2gas diffusion layer electrode at 60 °C. Then the prepared electrode was further dried in a vacuum at room temperature before use.Three-chamber PSE Reactor Cell Configuration and Electrochemical Measurements

[0062] The salt splitting and acid / base generation were conducted in a porous solid electrolyte (PSE) cell. The general cell configurations and the production setup are illustrated in FIGs. 1-3. The CEM close to cathode (Pt / C on carbon cloth) is Nation N2100TX, and the CEM close to anode side (Pt / C on carbon paper) is the Nafion-117 membrane. The active electrode area was 4 cm2. The cathode side was supplied with DI water for HER reaction. DI water was bubbling with nitrogen gas to remove dissolved oxygen, and the water flow rate was controlled by a syringe pump. In the middle chamber, the styrene-divinylbenzene sulfonated copolymer Dowex 50W X8 hydrogen form cation conductor (50-100mesh) was employed as the porous solid electrolyte (PSE). The IM Li2SO4 flowed into the PSE layer controlled by a syringe pump. The flow rate at the outlet was calibrated using a measuring cylinder. The anode side was provided with the 8.0 seem H2 gas for HOR reaction. All cell resistances were measured by the potentiostatic electrochemical impedance spectroscopy (PEIS), and all the cell voltages were reported without any iR compensation. For the cyclability tests,to avoid sudden voltage changes at the beginning of each cycle, the current density was gradually ramped up: starting at 25 mA cm'2, increasing to 50 mA cm'2, and finally reaching 100 mA cm'2, with each step lasting ~30 seconds. The increasing voltage drop at the end and beginning of each cycle, as shown in FIG. 12 discussed below, reflects this activation process, and for ramping periods exceeding 50 seconds, additional data points at 25 and 50 mA cm'2may be recorded.Ion Transport Number Calculation

[0063] tLi+Li+ transport number (or Li+ transport efficiency, between 0 and 1) describes the amount of Li+ crossed through CEM over the total number of electrons transferred. tLi+: The concentration of Li+ was determined vialC (Ion Chromatography) and ICP-MS (Inductively coupled plasma mass spectrometry) characterization. For continuous flow, the t for Li+ at the cathode is calculated using the following Equation 1 : (maximum 100%) Eqn. 14

[0064] For recirculation flow, the t for Li+ at the cathode is calculated using the following Equation 2: (maximum 100%) Eqn. 2Example 1 - General Method and System of Battery Recycling

[0065] FIG. 3 illustrates a system of the present disclosure which includes a three- chamber reactor 300 which is configured along with an acid leaching unit 302 and a precipitation unit 304 to recycle spent cathodes of lithium ion batteries into manufactured feedstocks. The methods and systems described herein address the inefficiencies of conventional acid-base separation in current pH-swinging electrolyzers. The three-chamber reactor may include a cathode 310, anode 306, and middle solid electrolyte layer 308, enabling simultaneous production of sulfuric acid 312 and pure lithium hydroxide 314. These components are utilized to leach spent cathodes and separate lithium from other transition metals (Co, Ni, Mn, etc.), facilitating a zero-water generation self-looped electrochemical LIB cathode recycling process. Methods and systems of the present disclosure reduce environmental impact,lower costs, and provide high-purity manufacturing feedstocks for battery manufacturing.

[0066] For example, a system including the three-chamber reactor uses a solid electrolyte in the reactor to recover lithium and transition metals from spent lithium- ion batteries. The three-chamber solid electrolyte reactor can produce sulfuric acid from the middle chamber while generating pure lithium hydroxide at the cathode. Sulfuric acids and lithium hydroxide may be used to leach spent cathodes and separate lithium from other transition metals, respectively. The solid electrolyte thus serves as an extra layer of porous, ion-conducting polymers between the anode and the cathode of the reactor. By operating electrochemical hydrogen evolution / oxidation reactions in a three-chamber reactor, an initial input of Li2SO4 solution can be split into lithium hydroxide and sulfuric acid, followed by a stoichiometric acid leaching and alkaline precipitation process to fully separate spent lithium metal oxides into high purity lithium and transition metal hydroxide products. FIGs. 2 and 3 illustrates three-chamber reactors along with examples of the chemical reactions that may take place according to the methods of the present disclosure.

[0067] As seen from FIG. 1, porous solid electrolyte (PSE) reactors can produce sulfuric acid and pure lithium hydroxide. Followed by a stoichiometric acid leaching and alkaline precipitation process, the spent lithium metal oxides can be separated into high purity lithium and transition metal hydroxide products. The disclosed methods and systems application extends to various lithium-ion battery cathodes, including lithium cobalt oxides, lithium manganese oxide, ternary lithium batteries (NMC), etc. Examples herein include LiCoCh and LiNii / 3 / 3Mm / 3 / 3Coi / 3 / 3O2 as examples of lithium-ion battery cathode materials to show the versatility of this disclosure.

[0068] The exemplified application of the three-chamber reactor uses cationconducting polymer particles functionalized with sulfonate groups as porous solid electrolyte, Nafion as proton exchange membrane (PEM), and Nafion N2100TX or ePTFE-reinforced Nafion as cation exchange membrane (CEM). However, any variations of ion-conducting polymers or resins may be used in the middle chamber, and any chlor-alkali membrane can be used as CEM (as long as it does not damage the original systems).

[0069] This example enables efficient recovery of materials from lithium-ion batteries (LIBs) without continuous consumption of external acids and bases. Conventional lithium-ion battery recycling technology involves energy- and waste-intensive processes. Moreover, current recycling methods will result in severe waste generation (such as NaOH, Na2SO4, NHC, etc.) that needs to be further treated before its discharge to the environment. The methods and systems described herein allow continuous, efficient, and high-rate production of lithium hydroxide and sulfuric acid, followed by a stoichiometric acid leaching and alkaline precipitation process to separate spent lithium metal oxides into high purity (> 99.7%) lithium and transition metal hydroxide products. The lithium salt electrolyte can be restored at the end of each recycling cycle. In these methods, spent lithium cobalt / nickel / manganese oxide batteries can be fully recycled as battery manufacturing feedstocks without consuming external acid / base and avoid external cation contaminations or waste stream treatments.

[0070] This example demonstrates continuous and stable operation for over 500 hours (equivalent to 26 cycles) under a current density of 100 mA / cm2Under a 400-mA 4cm2-cell electrolysis current, a generation of 0.65 M LiOH solution can be stably obtained to recycle 10.7g LCO particles into 4.6g of LiOH IUO and 10.2kg of Co(OH)2 per day. This electrolysis rate, when scaled up to a 1 m2electrode device, can recycle 26.8 kg LCO particles into 11.5 kg of LiOH IUO and 25.5kg of Co(OH)2 per day.

[0071] As described above, FIG. 2 illustrates a PSE reactor for Li2SO4 splitting, acid leaching, and the separation between lithium and transition metals by LiOH precipitation process. The electric energy input can come from renewable sources, and the final outputs are high-purity LiOH and Co(OH)2 (in the case of LiCoO2 for example), without any chemical wastes generated during the whole process as shown in FIG. 1. A self-looped electrochemical battery recycling system includes the following three main steps: (1) Li salt electrolysis in a porous solid electrolyte (PSE) reactor, (2) LiCoO2 dissolution and (3) Li / Co separation via Co precipitation. The net energy input is electricity that can come from renewable sources, and the final products are high-purity LiOH and Co(OH)2 with high recovery efficiencies.

[0072] The recycling loop is primed with an initial investment of a small amount ofLi2SO4. The initial investment of Li2SO4 is used for the first cycle. The Li2SO4 iscontinuously regenerated at the end of the cycle (or the beginning of the next cycle). The first step involves the electrochemical Li salt splitting, Li2SO4 + 2H2O = 2LiOH + H2SO4, to in situ generate sulfuric acid and lithium hydroxide for the following leaching and precipitation reactions, respectively. Due to the charge balances during electrolysis, the molar number of generated protons exactly equals to that of hydroxide ions, which differs from external acid / alkaline sources and guarantees the following steps’ precise stoichiometry. Step 2 is the cathode decomposition reaction by mixing spent LiCoCh powders with the in situ generated protons, 2LiCoCh + 3H2SO4 + H2O2 = Li2SO4 + 2CoSO4 + O2 + 4H2O, where H2O2 is introduced as a reducing reagent to facilitate this leaching process. After the acid leaching, Li+and Co2+mixture (1: 1 molar ratio in the case of pristine LiCoCh) will be further separated by tuning the pH using only a portion of the in situ generated LiOH stream (step 3): 2LiOH + CoSO4 = Li2SO4 + Co(OH)2j, resulting in Co(OH)2 solids as the recycled Co product, and Li2SO4 solution as the next starting point of the recycling process. Meanwhile, the unused LiOH stream is the recycled Li product. The overall reaction can be presented as: 2LiCoO2 + 2H2O + H2O2 + electricity -> 2LiOH + 2Co(OH)2+ O2.

[0073] A quantitative analysis can additionally illustrate the whole recycling process. In an ideal case based on the reaction stoichiometry, assuming 1 mole of protons and 1 mole of hydroxides are generated via step 1, 1 / 3 mole of Li+and 1 / 3 mole of Co2+will be produced from LiCoO2 in step 2 when all the protons can be consumed. As a result, step 3 only requires 2 / 3 of the basified stream from step 1 to precipitate the 1 / 3 mole of Co ions, and the remaining 1 / 3 mole of LiOH becomes the recycled Li products. Therefore, for every 1 mole of proton / hydroxide generated from electrolysis, 1 / 3 mole of LiCoO2 can theoretically be recycled into LiOH and Co(OH)2. The cathode materials from spent battery may have lower Li ratios, which would require slight adjustments in the process but does not affect the overall recovery efficiencies.Example 2 - Discussion of Additional Battery Recycling Processes

[0074] Among the different components of LIBs, the recycling of cathode materials is crucial due to the high value transition metals, such as Co, Ni, Mn, as well as the remaining lithium ions. There are two major strategies proposed for cathode recycling: i) cathode reactivation for direct recycling, and ii) cathode material decomposition into raw materials or chemical feedstocks. While direct recycling is likely to reduce theenergy consumption and / or require fewer recycling steps, it remains challenging to precisely control the quality of the reactivated materials such that they meet requisite industry standards. Breaking down the spent cathode materials into raw materials can be smoothly integrated into the existing battery manufacturing supply chain, but current methods are primarily based on pyrometallurgy and hydrometallurgy, both involve energy- and waste-intensive processes, such as high temperature or substantial chemical usage. For example, FIG. 4 illustrates a traditional hydrometallurgy method 400, where spent lithium-ion batteries are dismantled and strong acids and reducing agents are used to leach cathode materials into ions, strong acids are used to first leach cathode materials into ions, followed by adding alkaline solutions to separate transition metals from lithium via precipitation as shown in FIG. 4. Due to the continuous consumption of acids and bases, the process results in waste generation (such as NaOH, Na2SO4, and NH4+) that needs to be further treated before its discharge to the environment. More importantly, the use of alkaline solutions introduces external cations such as Na+or NH4+that potentially contaminate the Li source, potentially complicating the Li ion recovery due to the ions’ similarities. In addition, traditional hydrometallurgy typically yields lithium salts, such as lithium carbonate (Li2COs) or lithium sulfate (Li2SO4), which requires further processing to be converted into lithium hydroxides (LiOH), a precursor for the production of most high-nickel or high-energy- density lithium batteries.

[0075] In contrast, a self-looped electrochemical battery recycling method according to one or more embodiments, enables internal acid / base generation for the precise recovery of Li and Co from spent LiCoCh, with no chemical waste generated during the recycling process. This strategy may also be applied to recover transitional metals from other lithium metal oxide cathodes. By electrochemically converting Li2SO4 solution into LiOH and H2SO4 with a high Li+transport efficiency (tu+> 90%) and operation current density (> 100 mA / cm2) in a three-chamber porous solid electrolyte reactor, spent LiCoO2 cathode was separated into high-purity LiOH (>99.7%) and CO(OH)2 (>99.8%) products with a high recovery rate of over 91.2% for Li and 97.0% for Co. Up to 4.8 mol / L of LiOH solution can be obtained in the solid electrolyte reactor while still maintaining over 50% tLi+. The solid electrolyte reactor showed superiorperformance compared to other electrolyzer designs and maintained excellent stability of over 500 hours of operation.Example 3 - PSE Cell Operation Design

[0076] A detailed electrochemical characterization of the PSE reactor for Li2SO4 splitting is a prerequisite to fully understand the reactor’s intrinsic electrochemical properties and optimize the cell operation conditions for LIB recycling. As shown in FIG. 3, there are two liquid streams in this exemplary reactor: the Li2SO4-to-acid stream in the middle PSE chamber, where Li2SO4 is converted into an acidic solution (a mixture of Li2SO4 and H2SO4), and the other is water-to-LiOH alkaline stream in the cathode chamber, where water is used as input, and the outlet consists of water flux mixed with LiOH generated during the electrochemical process. These liquid streams can either be operated via a batch recirculation or a continuous flow manner. By systematically analyzing the impacts of different flow patterns on the device performance, it was determined that a batch recirculation in the cathode chamber and a continuous flow in the PSE layer would benefit the tu+ when delivering acid and alkaline streams at high concentrations. When continuously flowing IM Li2SO4 (0.36 mL per min) into the PSE layer, the tLi+ at 400mA of 3-chamber PSE was maintained at or above 80 %, however, when the catholyte flow rate was continuously held at about 0.27mL per min, poor tLi+ due to the low flow rate was observed. By recirculating the electrolyte at the cathode chamber with a high volumetric flow rate, the interfacial Li+concentration is effectively diluted, therefore the interfacial concentration gradient barrier across the CEM is lowered, while still continuously accumulating bulk LiOH at the end of the cycle; along the PSE chamber, a continuous but slow electrolyte flow can minimize the interruption of aligned Li+layer at the CEM / electrolyte interface, and reduce the impact of accumulated protons on tu+ as in the case of recirculation.

[0077] A step-by-step process optimization of an exemplary PSE reactor operation (4- cm2electrode area) was conducted: To achieve a sufficient decomposition rate of LCO powders, the pH of the middle layer output needs to be as low as possible while still maintaining a good tLi+. As shown in FIG. 5, under a fixed current of 100 mA / cm2, by gradually decreasing the flowrate of middle layer Li2SO4 solution (1 M) from 2.0 to 0.2 mL / min, the pH of acidified stream decreased from 1.8 to 0.6. While the concentration of output protons was increased by more than one order of magnitude, the tu+ based onLi+collected from the catholyte was slightly dropped from up to 95% to 82%, suggesting the high Li+selectivity of the CEM and the PSE layer. To balance the output pH and tLi+, in the following tests, flowrate of 0.36 mL min-1 in the middle layer electrolyte was used to continuously output a pH of ~ 0.85 while achieving ~ 90% tLi+.

[0078] As lower pH output from the PSE layer benefits the LCO dissolution process, higher pH, or higher concentrations of LiOH in the catholyte will benefit the Co precipitation process without introducing excessive water for evaporation. To evaluate how the catholyte Li+accumulation could impact the pH and the Li+transport number in middle layer, a Li+mass balance analysis during a 10-hour Li2SO4 salt splitting process was established using 200 mL 1 M Li2SO4 for the PSE layer stream (continuous flow) and 200 mL DI water for the catholyte stream (recirculation) as shown in FIG. 6. Due to ion transport and osmotic effects, the volumes of catholyte and PSE layer electrolyte showed slight changes during electrolysis.. The output Li+concentration from the PSE layer was stabilized at ~ 1.5 M, suggesting an electrolyte composition of H2SO4 and Li2SO4, with a very stable pH output of ~ 0.9 as shown in FIG. 7. The missing Li+from the PSE layer stream was well-matched with that detected in the catholyte. As shown in FIG. 6, the LiOH concentration was linearly increased to ~ 0.65 M at the end of this salt splitting electrolysis, corresponding to ~ 3.3g of LiOH powder after water evaporation, as shown in FIG. 7. The LiOH accumulation gradually increased the catholyte pH from neutral at the beginning to -13.20, agreeing well with the calculated amount of LiOH. The total Li+mass in the system was well maintained and equal to the initial input value during the electrolysis, as shown in FIG. 6. More importantly, the cell voltage and tu+ were maintained stable at 1.8 V and -90% under 100 mA / cm2, respectively, suggesting little impact of catholyte Li+accumulation on the cell performance until a reasonably high LiOH concentration for practical battery recycling. However, to determine the maximum LiOH concentration the PSE reactor can attain, an additional experiment was performed with a reduced volume (20 mL) catholyte for recirculation and extended electrolysis duration. FIG. 8 shows that up to 4.8 M of LiOH was obtained while maintaining a tu+ of over 50% (considering volume increase from 30 mL to 44 mL due to electro-osmotic water crossover), which is high considering the LiOH theoretical solubility of 5.1 M at room temperature.Example 4 - LCO Recycling

[0079] The efficient generation of acidified stream and basified stream via Li2SO4 salt splitting provides the foundation for the following LCO recycling steps. To maximize the utilization efficiency of the generated protons, the pH of the solution after mixing the acidified stream with LCO particles should be as high as possible to increase the leached-out Li and Co. This was determined with by tracking the leaching of Li and Co from O.llmol LCO by first mixing a 500 mL acidified stream mixture of 0.33M H2SO4 (0.165 mol) and 0.75M Li2SO4 (0.375 mol), then adding 30 mL of 30% H2O2 and the 0.1 Imol LCO to form a 530 mL pink mixture of 0.21M CoSO4 (0.1 Imol) and 0.81M Li2SO4 (0.43mol). During the cobalt leaching process, 360 mL of LiOH was produced from the cathode and added to tune the pH to about 10, resulting in an 890 mL slurry of 0.11 mol Co(OH)2 and 0.54 mol Li2SO4 which was filtered and washed, leaving 0.11 moles of gel-like Co(OH)2 which can be dried to a powder. LiOH was also produced. The input stock in the middle chamber was 540 mL 1.0 M Li2SO4 and the output was 500 mL of acidified stream. In this case, excessive LCO particles were used and the temperature was optimized as well as H2O2 amount. Based on a pH (~4.0 to 4.8) of the final solution after acid leaching, the proton utilization efficiency is above 99.9%, which means that less than 0.1% of produced LiOH from cathode is required to neutralize unused acids during the cobalt precipitation step as shown in FIG. 9. Meanwhile, to maximize the recovery of Co via Co(OH)2 precipitation, slightly excessive LiOH was needed to raise the pH during the precipitation. As shown in FIG. 9, there was a pH plateau that represents the Co2+precipitation process. The remaining Co2+concentration in the solution (unprecipitated Co) was monitored using ion chromatography (IC) while LiOH was gradually added. The Co2+peak became negligible from IC when the pH was above 10, and the remaining Co concentration in the solution was less than 0.000058 M at pH = 10.5, representing a Co recovery efficiency of > 99.95% considering the starting Co concentration of 0.21 M leached from LCO. To reach this pH for high Co recovery efficiency, around 65% of LiOH generated from the cathode was consumed, see FIG. 9, which is close to the theoretical value of 66.7% as discussed in the above quantitative analysis. When the pH was around 10-11, 99.95% of Co2+ions were precipitated as Co(OH)2, corresponding to about 0.05% Co2+ion loss. As a result, the remaining 35% LiOH solution from theLi2SO4 salt spliting process, and the Co(OH)2 precipitates are the final products after one loop, and the solution would turn back to Li2SO4 again for the next loop.

[0080] The overall recovery efficiency of one full recycling loop process can be seen in FIG. 10, including both the acid leaching and the alkaline precipitation process, and is calculated to be 99.76%, and 99.85% for Li and Co recycling, respectively. This is based on the mass loss as LiOH trapped in Co(OH)2 precipitates and Co impurity in Li2SO4, ignoring other possible loss such as liquid or solid transport. Moreover, on the basis of the amount of produced LiOHTLO and Co(OH)2 powder after precipitation and drying, it was calculated that more than 91.2% of Li and 97.0% of Co in the initial spent LiCoCh was successfully recycled.

[0081] The purity of the recovered LiOH and Co(OH)2 products were analyzed by X- ray diffraction (XRD), IC, and inductively coupled plasma mass spectrometry (ICP- MS). The possible impurities could be the following three scenarios: Li impurity in CO(OH)2 when trapped inside the precipitates; Co impurity in LiOH due to incomplete Co precipitation in Step 3 that crossed over to the cathode side in the next round of salt spliting; and SO42' impurities in both LiOH and Co(OH)2. FIG. 11 shows the XRD paterns which confirmed the crystal structures of LiOH and Co(OH)2 powders obtained from the LCO recycling were without other potential impurity peaks such as Li2SO4, CoO, or Li2COs. ICP-MS was also used to carefully quantify potential impurity elements in LiOH and Co(OH)2 as shown in Tables 1 and 2 below, which suggested around 0.0001 wt% impurity in LiOH and less than 0.317 wt% impurity in Co(OH)2. The high purity of the recovered products can offer potentially smooth feeding of these recovered Li and Co materials into existing batery manufacturing supply chains.Table 1. Impurities Present in Recycled LiOH and Co(OH)2Table 2. Impurities Present in Recycled LiOH and Co(OH)2 as Weight Mass Ratios

[0082] To evaluate the practical long-term stability of the PSE device for this selflooped electrochemical LCO recycling strategy, the cycling capacity was increased and multiple cycles were performed. The cycling stability was evaluated by applying a constant current density of 100 mA cm2(4 cm2, 400 mA total current), with 500 mL 1.0 M Li2SO4 solution as the starting stock solution for the whole course of stability testing (200 mL for the first 10 cycles, and switched to 500 mL for the following 16 cycles, flow rate: 0.36 mL min'1). Over 26 cycles, the LiOH generation rate was maintained above 15 gm^d'1. Benefiting from the reliable electrocatalysts, membranes, porous solid electrolytes, and the cell configuration, the 3 -chamber PSE cell shows excellent stability in producing LiOH at the cathode as well as generating acids at the middle chamber. As shown in FIG. 12, the 3-chamber PSE reactor can be stably operated for more than 500 hours, including 26 cycles, with negligible degradations in terms of both cell voltages (less than 300 mV increase) as well as tu+ (maintaining > 80% after 500 hours). The Li2SO4 solution used after the very first cycle was not freshly prepared but was regenerated from the prior cycle after the Co(OH)2 precipitation process. Under the 400-mA cell electrolysis current, a generation of ~ 0.65 M LiOH solution can be stably obtained for each cycle (see FIG. 12, 10-hour electrolysis for the first 10 batches of 200 mL and 25-hour electrolysis for the following 500 mL batches). This electrolysis rate, when scaled up to a 1 m2electrode device, can recycle -26.8 kg LCO particles into 11.5 kg of LiOH H2O and 25.5kg of Co(OH)2 per day.Example 5 - Comparing Multiple Reactor Designs

[0083] To efficiently produce acidified and basified streams from Li2SO4 electrolysis with minimal chemical input or side products, a three-chamber PSE reactor coupledwith hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) was employed as discussed above. The reason to choose the HER / HOR redox to drive the salt splitting is due to their fast reaction kinetics and small overpotentials. In addition, the generated H2 from cathode can be collected and looped back to anode, without any net consumption or production of H2 during the electrolysis. Of course, other types of redox reactions can be flexibly coupled in this reactor with different cell voltages, product generation or consumption. As schematically shown in FIG. 2, the PSE layer consists of dense yet permeable cation-conductive polymer particles functionalized with sulfonate groups. This layer was sandwiched by two types of cation exchange membranes: one for proton exchange (PEM) and the other for lithium-ion transport (CEM). Pt / C catalyst coated carbon fibre paper and a gas diffusion layer (GDL) electrode were used for HER and HOR, respectively. By continuously flowing Li2SO4 solution through the PSE layer chamber while operating HER / HOR electrolysis, protons generated via HOR on the anode (H2 —> 2H++ 2e’) were driven by the electrical field to move across the PEM towards the middle layer and displace the Li+towards the cathode chamber to form LiOH (2H2O + 2e" — > H2 + 2OH ). The PSE layer not only facilitates efficient cation conduction between the cathode and anode and the formation of targeted products, but also reduces ohmic drops and enhances the ion transport efficiency and stability of various electrocatalytic reactions as shown in Table 3 below. As a result, acidified and basified stream were produced in the middle and cathode chamber, respectively. A chlor-alkali CEM (Nafion N2100TX or ePTFE-reinforced Nafion) was chosen for the cathode side to maximize the selectivity of Li+crossover vs. the competing H+(defined as transport number, or transport efficiency).Table 3. Performance Comparison Between Electrochemical Reactors

[0084] The electrochemical battery recycling strategy can be flexibly extended beyond LCO cathode to other lithium metal oxide cathode materials. LiNii sMni 3C01 3O2 (NMC), one of the most common cathode materials used in electrical vehicles to test the PSE reactor’s applicability. As shown in FIG. 13, after a 10-hour electrochemical salt spitting (same operation condition as LCO), the continuous flow of acidified stream was applied to decompose LiNii / 3M / 3Coi / 3O2 powders to become Li+ / Ni2+ / Mn2+ / Co2+mixed solution, and the basified stream from cathode was then used to co-precipitate Ni2+ / Mn2+ / Co2+to NiMnCo(OH)x. This NiMnCo hydroxide precipitation had the same elemental ratio with the battery cathode being recycled, and can be directly used as the feeding stock for new NMC fabrications. The pH was tuned to ~ 10.5 to ensure that 99.8% of transition metal ions were converted to hydroxide precipitations. After the following filtration and drying process, the green NiMnCo(OH)xpowders were collected, and the upper solution, which contains Li2SO4, was redirected into the PSE reactor for the next cycle of electrochemical salt spitting, from 10 h to 20 h, see FIG. 13. Individual transition metals such as Ni, Mn, and Co were not further separated in this study, this mixture compound with certain atomic ratios could be directly fed into the NMC battery electrode fabrication chain.

[0085] The conversion efficiency of different metals from NMC to hydroxides (FIG. 14) were estimated using IC and ICP-MS, including both transition metal conversion (by measuring the transition metal contents in precipitation, NMC ternary precursor, NiMnCo(OH)x, and transition metal loss in the upper Li2SO4 solutions, ) as well as Li conversion (by measuring the amount of final LiOH H2O products, and the Li loss in NiMnCo(OH)xprecipitation). The mixed metal hydroxide precipitates were further annealed in air to produce mixed metal oxides. FIG. 15 shows the powder XRD patterns of the post-annealed precipitation from LiCoCh and LiNii / sMm / sCoi / sCh showed that the transition metal oxides are high purity CO3O4 and NiCoMnCL. respectively.

[0086] The advantages of the three-chamber PSE reactor design can be clearly shown by comparing the electrochemical performance with other cell configurations (Table Z and FIGs. 16-30). First, compared with a conventional 2-chamber membrane electrode assembly (MEA) reactor, FIGs. 17 and 20, where both cathode and anode reactions inthis application are limited within liquid electrolytes, the exemplary reactor illustrated in FIG. 16, the PSE middle chamber allows for Li2SO4 stream flow, thus enabling the anode chamber to efficiently operate HOR using GDL electrodes. More importantly, the PSE layer also functions as an important “buffer layer” to effectively dilute the proton flux generated at the sharp anode / membrane interface, and thus promote the Li+transport towards the cathode chamber. As shown in Table 3 and FIGs. 16-19, the MEA-CEM cell presented a higher cell voltage than that of the PSE cell as well as the MEA-PEM cell, suggesting an interfacial proton repulsion effect against the Li This buffer layer’s benefit was also reflected from the improved Li+transport number as shown in FIGs. 16-19, where the PSE reactor presented over 90% tu+ across the whole current density range as compared with less than 50% in the case of MEA design. Second, the middle layer PSE plays an important role in improving cell performance. As a control experiment, illustrated in FIG. 23, when using inert silicon dioxide with a similar size to the PSE particles to instead pack the middle layer, the cell showed a larger resistance and thus higher cell voltages as shown in Table 3, and FIGS. 23-25, suggesting that the PSE particles facilitated Li+ion transport across the middle layer. After these above-discussed cell design optimizations, the PSE reactor showed a high electrochemical performance to split Li2SO4, delivering 100 mA / cm2large current under 1.8 V while maintaining a 90% Li+transport efficiency, thereby forming the foundation for the following steps of LIB recycling.

[0087] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A method for recycling a material of a spent cathode of a lithium-ion battery, comprising: mixing an input stream comprising a lithium metal oxide compound with an acidic stream in an acid leaching unit to decompose the lithium metal oxide compound thereby providing a first in loop solution comprising a lithium salt and a metal compound, wherein the lithium metal oxide compound is derived from the spent cathode; mixing a first portion of a basic stream with the first in loop solution in a precipitation unit to separate the metal compound as a solid metal compound from a second in loop solution comprising the lithium salt; feeding the second in loop solution to an electrochemical reactor; producing the acidic stream and the basic stream in the electrochemical reactor by a salt splitting reaction of the lithium salt, wherein the basic stream comprises ionic lithium derived from the lithium salt and the acidic stream comprises an anion derived from the lithium salt; and collecting the solid metal compound and the ionic lithium, wherein the solid metal compound and the ionic lithium are, respectively, first and second recycled materials.

2. The method of claim 1 , comprising: priming the electrochemical reactor with an initial out of loop solution of the lithium salt before: mixing the input stream with the acidic stream, mixing the first portion of the basic stream with the first in loop solution, and feeding the second in loop solution to the electrochemical reactor.

3. The method of claim 2, further comprising periodically supplying the electrochemical reactor with a replenishing stream comprising the lithium salt.

4. The method of any of the preceding claims, wherein the lithium salt comprises lithium sulphate.

5. The method of any one of the preceding claims, wherein mixing the input stream with the acidic stream in the acid leaching unit further comprises mixing an external reducing agent stream with the input stream and the acidic stream, wherein the external reducing agent stream optionally comprises hydrogen peroxide.

6. The method of any one of the preceding claims, wherein the metal compound comprises a transition metal selected from the group consisting of nickel, manganese, cobalt, and combinations thereof.

7. The method of any one of the preceding claims, wherein the electrochemical reactor comprises a three-chamber reactor comprising: an anode chamber, wherein the anode chamber is formed by an anode and a first ion exchange membrane, the anode comprising an anode catalyst for oxidation; a cathode chamber, wherein the cathode chamber is formed by a cathode and a second ion exchange membrane, the cathode comprising a cathode catalyst for reduction; and a middle chamber formed between the anode chamber and the cathode chamber, wherein the middle chamber comprises a porous solid electrolyte comprising ion conducting polymer particles.

8. The method of claim 7, wherein producing the acidic stream and the basic stream in the electrochemical reactor by a salt splitting reaction of the lithium salt comprises feeding an oxidizing agent stream to the cathode chamber, feeding an internal reducing agent stream to the anode chamber, and applying a voltage across the cathode in the cathode chamber and the anode in the anode chamber.

9. The method of claim 8, wherein the oxidizing agent stream comprises water and the internal reducing agent stream comprises hydrogen produced in the cathode chamber.

10. The method of claim 9, wherein the input stream, the oxidizing agent stream, the external reducing agent stream, and the internal reducing agent stream define an exclusive set of chemical streams that are provided to a recycling reactor system comprising the three-chamber reactor, the acid leaching unit, and the precipitation unit, whereby the recycling reactor system is self-sustaining.

11. The method of claim 7, wherein the lithium salt comprises lithium sulphate and the ion conducting particles are functionalized with sulfonate groups.

12. The method of claim 7, wherein the anode catalyst is active for catalyzing a hydrogen oxidation reaction or an oxygen evolution reaction and the cathode catalyst is active for catalyzing a hydrogen evolution reaction.

13. A method for recycling a spent cathode of a lithium-ion battery, comprising: providing a three-chamber reactor comprising: an anode chamber formed by an anode and a first ion exchange membrane, the anode comprising an anode catalyst for oxidation, a cathode chamber formed by a second ion exchange membrane and a cathode, the cathode comprising a cathode catalyst for reduction, and a middle chamber formed between the anode chamber and the cathode chamber, wherein the middle chamber comprises a porous solid electrolyte comprising ion conducting polymer particles, wherein the ion conducting particles are functionalized with sulfonate groups, recycling the spent cathode of the lithium-ion battery by: supplying the three-chamber reactor with an internal reducing agent stream to the anode chamber, an oxidizing agent stream to the cathode chamber, and an input stream of lithium sulphate to the middle chamber, applying a voltage to the three-chamber reactor to obtain sulfuric acid and lithium hydroxide from the three-chamber reactor by splitting the input stream of lithium sulphate, acid leaching the spent cathode of the lithium-ion battery with the sulfuric acid to obtain a stream of transition metal sulphate solution, precipitating at least one transition metal from the transition metal sulphate solution with a first portion of the lithium hydroxide to obtain a first recycled product stream, the first recycled product stream comprising a recycled transition metal hydroxide product, and an output stream of lithium sulphate,obtaining a second recycled product stream comprising a second portion of the lithium hydroxide, and optionally repeating the recycling operation by providing the output stream of lithium sulphate to the middle chamber to serve as the input stream of lithium sulphate, wherein a third portion of the lithium hydroxide is optionally recirculated in the cathode chamber.

14. The method of claim 13, wherein the anode catalyst is active for catalyzing a hydrogen oxidation reaction or an oxygen evolution reaction and the internal reducing agent stream is a stream of hydrogen or water.

15. The method of claim 13, wherein the cathode catalyst is active for catalyzing a hydrogen evolution reaction and the oxidizing agent stream is a stream of water.

16. The method of claim 13, wherein acid leaching the spent cathode of the lithium-ion battery comprises providing an external reducing agent for the acid leaching to the sulfuric acid and the spent cathode, wherein the external reducing agent for the acid leaching optionally comprises hydrogen peroxide.

17. The method of claim 13, wherein the recycling operation comprises: obtaining an amount of protons through an oxidation reaction at the anode chamber using the internal reducing agent stream and the anode catalyst; obtaining hydrogen and an amount of hydroxide ions through a reduction reaction at the cathode chamber using the oxidizing agent stream and the cathode catalyst wherein the amount of hydroxide ions equals the amount of protons, and wherein the hydrogen is optionally provided as the internal reducing agent stream to the anode chamber; and electrochemically separating the lithium sulphate into lithium ions and sulphate ions in the middle chamber by electrolysis, wherein the voltage to the three-chamber reactor creates an electric field that transports a portion of the protons from the anode chamber through the first cation exchange membrane to the middle chamber and displaces a portion of lithium ions in the middle chamber through the second cation exchange membrane into the cathode chamber, andwherein the lithium ions react with the hydroxide ions in the cathode chamber to produce the lithium hydroxide and the sulphate ions react with the protons in the middle chamber to produce the sulfuric acid.

18. A system for recycling a spent cathode of a lithium-ion battery, the system comprising: a three-chamber reactor comprising: an anode chamber formed by an anode and a first ion exchange membrane, the anode comprising an anode catalyst for oxidation, a cathode chamber formed by a second ion exchange membrane and a cathode, the cathode comprising a cathode catalyst for reduction, and a middle chamber formed between the anode chamber and the cathode chamber, wherein the middle chamber comprises a porous solid electrolyte comprising ion conducting polymer particles; an oxidizing agent stream fluidically coupled to the cathode chamber; an internal reducing agent stream fluidically coupled to the anode chamber; a lithium salt stream fluidically coupled to the middle chamber and optionally a replenishing stream comprising the lithium salt fluidically coupled to the middle chamber; an acid leaching unit in which a lithium metal oxide compound of the spent cathode of the lithium-ion battery is provided, the acid leaching unit fluidically coupled to the three-chamber reactor; a precipitation unit fluidically coupled to the three-chamber reactor and the acid leaching unit; a basic stream fluidically coupling the three-chamber reactor to the precipitation unit; an acidic stream fluidically coupling the three-chamber reactor to the acid leaching unit; and a solid accumulator coupled to the precipitation unit.

19. The system of claim 18, further comprising an external reducing agent stream fluidically coupled to the acid leaching unit, wherein the external reducing agent stream optionally comprises hydrogen peroxide.

20. The system of claim 18, wherein the anode catalyst is active for catalyzing a hydrogen oxidation reaction or an oxygen evolution reaction and the internal reducing agent streamis a stream of hydrogen or water; and wherein the cathode catalyst is active for catalyzing a hydrogen evolution reaction and the oxidizing agent stream is a stream of water.

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