Plasma-assisted metal recovery from battery waste

Abstract

A method for recycling waste is provided. The method includes exposing the waste to a plasma to obtain a plasma-exposed waste, and leaching at least one metal in acid from the treated waste to obtain a treated waste. The method may then further include preferentially leaching lithium from the plasma-exposed waste to obtain a treated waste. The method may further include recovering graphite from the treated waste.

Description

PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCTPLASMA-ASSISTED METAL RECOVERY FROM BATTERY WASTEBACKGROUND

[0001] Lithium-ion batteries (LIBs), with their light weight and high energy densities, are crucial components in the changing global energy landscape fueled by the rise of electric vehicles and the growing energy demands of artificial intelligence. Typically, LIB cathodes comprise mixed transition metal (e.g., Co, Ni, Mn) oxides of lithium (Li), whereas the anode consists of high quality ordered spherical graphite. The depletion in the ores due to over-mining and geopolitical tensions affecting the supply chain has caused all of these necessary components to be categorized as critical minerals. These minerals are not uniformly distributed over the Earth’s crust and are located in specific pockets, many of them in conflicted regions and potential war zones, raising concerns over their unrestricted supply chain. Hence setting up efficient LIB recycling systems are of utmost importance to establish circularity by recovering the critical minerals while finding an effective solution for electronic waste.

[0002] Among the different recycling technologies explored till now, pyrometallurgy and hydrometallurgy, or a combination of both, have been most commonly adapted by industries owing to their ease of operation and ability to deal with large bulks of battery waste. However, pyrometallurgical processes have high energy demands, and often operate beyond 1000°C for long durations, produce noxious emissions and tend to lose lithium in the process. On the contrary, hydrometallurgy involves leaching the critical minerals from the LIB waste in suitable lixiviants at ambient temperatures, which are then recovered by precipitation through chemical means.

[0003] Conventionally, hydrometallurgical approaches are reliant on the use of highly corrosive concentrated inorganic acids and flammable reducing agents, e.g., peroxides, which pose a threat to human health and the environment alike. While milder green solvents, e.g., organic acids and Deep Eutectic Solvents (DESs) have been explored as alternatives, they fall behind in terms of efficiency. Additionally, selective recovery of lithium has remained a challenge across variousPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT hydrometallurgical processes owing to its high solubility, easy degradability and precipitation after all the transition metals. Also, most LIB recycling studies reported so far have mostly focused only on recovery of the transition metals and lithium from cathode, while recovery of the graphite anode and treatment of commercial black mass waste from shredded LIBs remains largely ignored. Further, in Li-ion batteries, during multiple charge discharge cycles, graphite lattice spacing gets expanded, also SEI (solid electrolyte interphase) forms on its surface. However, conventional recycling methods are unable to address these and hence the original structure of graphite is not recovered.

[0004] Accordingly, there exists a need for environmentally friendly and low energy methods for recycling LIB waste streams.SUMMARY

[0005] 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.

[0006] In one aspect, embodiments disclosed herein relate to a method for recycling waste. The method includes exposing the waste to a plasma to obtain a plasma- exposed waste. The waste may be a feedstock selected from the group consisting of black mass from lithium-ion batteries, black mass from sodium ion batteries, cables, wires, fly ash, coal ash, coal char, electronic wastes, renewable energy wastes, mined ores, mined tailings, and combinations thereof. The plasma may include a gas selected from the group consisting of Ar, NH3, O2, CO2, N2, CH4 and H2. Exposing the waste to a plasma may include an exposure time ranging from 2 to 60 minutes.

[0007] The method may further include recovering graphite from the treated waste. When the method further includes recovering graphite from a treated waste the waste may include graphite from a spent battery and the treated waste may include the recovered graphite. The recovered graphite may have improved crystallinity as compared to the graphite from the spent battery. The improved crystallinity may include reduced lattice spacing and / or lower defects. The reduced lattice spacing mayPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT at least 2% reduced, for example between 2 and 6 %. The lower defects may be at least 70% lower, for example between 70 and 95 % lower.

[0008] The recovered graphite may be reused in a device such as an energy storage device or a supercapacitor. The graphite may be reused in a polymer-graphite composite. A composition may include the recovered graphite obtained by the method for recycling waste. An apparatus may include the device obtained by the method for recycling waste. The device may include the composition.

[0009] The method may further include leaching at least one metal from the treated waste in an acid. The leaching at least one metal in an acid includes soaking the treated waste in an organic acid, thereby leaching the non-lithium metal into an acid leachate. The organic acid may be selected from the group consisting of citric acid, lactic acid, acetic acid, ascorbic acid, glycolic acid, malonic acid, formic acid, oxalic acid, uric acid, malic acid, tartaric acid, butyric acid, folic acid and combinations thereof. The organic acid may be present in a concentration ranging from 0.1 M to 2.0 M. The non-lithium metal may be selected from the group consisting of Co, Ni, Mn, Al, Cu and combinations thereof. The second leachate may include at least 90% of the metal originally contained in the waste.

[0010] The method may further include preferentially leaching lithium from the plasma-exposed waste to obtain a treated waste. The preferentially leaching lithium includes soaking or stirring the plasma-exposed waste in water at a temperature of less than 30 °C, thereby leaching lithium into a water leachate. The water leachate comprises less than 20% of the metals leached in acid and at least 80% of the lithium originally contained in the waste. The water may be an effluent from a sewage treatment plant.

[0011] Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.BRIEF DESCRIPTION OF THE FIGURES

[0012] FIG. l is a schematic diagram illustrating a recycling process, according to one or more embodiments.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO.2025-030-PCT

[0013] FIG. 2 is a schematic diagram illustrates a recycling system, according to one or more embodiments.

[0014] FIG. 3 shows magnified images of peaks PXRD peaks corresponding to (003) and (104) planes of LCO and NMC811 in BM and BM samples exposed to different plasma for 5 mins.

[0015] FIG. 4 shows selective Li leaching efficiencies in water at room temperature in 1 hr from BM, CO2P5, N2P5 and H2P5.

[0016] FIG. 5 shows leaching efficiencies of all TMs and Li from BM, CO2P5, N2P5 and H2P5 in 1 M citric acid at room temperature in 1 hr.

[0017] FIG. 6 shows SEM images of the different particles in BM, namely, NMC, LCO and graphite showing morphological changes after exposure to different compositions of plasma, where CO2P5 is the sample generated by exposing BM to CO2plasma for 5 mins, N2P5 is the sample generated by exposing BM to N2plasma for 5 mins, while H2P5 is the sample generated by exposing BM to plasma comprising 60%H2+40%N2for 5 mins.

[0018] FIG. 7 shows SEM images depicting change in morphology of NMC, LCO and graphite with increase in exposure time to 60% H2+40%N2plasma.

[0019] FIG. 8 shows PXRD patterns of the samples exposed to 60% H2+40%N2plasma for different time durations.

[0020] FIG. 9 shows N2adsorption isotherms at 77K for the samples exposed to 60% H2+40%N2plasma for different time durations.

[0021] FIG. 10 shows selective Li LEs in water at room temperature as a function of increase in exposure to 60% H2plasma.

[0022] FIG. 11 shows LEs of TMs and Li in 1 M citric acid at room temperature as a function of increase in exposure to 60% H2plasma.

[0023] FIG. 12 shows elective Li leaching efficiencies at room temperature in water using different methods or water sources.

[0024] FIG. 13 shows LEs of TMs and Li in 1 M citric acid at room temperature as a function of increase in percentage of H2 in the plasma gas mixture.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0025] FIG. 14 shows PXRD pattern of H2PI5 showing the presence of reduced metallic species after exposure to plasma, where the intense graphite peaks have been omitted here for easier visualization.

[0026] FIG. 15 shows Lils XPS spectra of BM and H2PI5.

[0027] FIG. 16 shows Co2p XPS spectra of BM and H2PI5.

[0028] FIG. 17 shows PXRD peaks corresponding to (002) and (101) planes of graphite portraying shifts with increasing plasma pretreatment time.

[0029] FIG. 18 shows Raman spectra of the recovered graphite samples after leaching metals from sample exposed to plasma for different durations.

[0030] FIG. 19 shows lithium-ion battery half-cell performance demonstrated by CV at 0.1 mV / s scan rate for the first three consecutive cycles for Gr@BM.

[0031] FIG. 20 shows lithium-ion battery half-cell performance demonstrated by CV at 0.1 mV / s scan rate for the first three consecutive cycles for Gr@H2P15.

[0032] FIG. 21 shows lithium-ion battery half-cell performance demonstrated by CV at 0.1 mV / s scan rate for the first three consecutive cycles for CGr.

[0033] FIG. 22 shows galvanostatic charge-discharge (GCD) profiles of Gr@BM, Gr@H2P15, and CGr for the 2ndcycle at 100 mA / g.

[0034] FIG. 23 shows galvanostatic charge-discharge (GCD) profiles of Gr@BM, Gr@H2P15, and CGr for the 2ndcycle at 500 mA / g.

[0035] FIG. 24A shows cycling performance of Gr@BM, Gr@H2P15, and CGr at 100 mA / g current rate for the first 25 cycles.

[0036] FIG. 24B shows long-term cycling stability of the three samples at 500 mA / g current rate and corresponding coulombic efficiency.

[0037] FIG. 25 shows OES spectra of different plasma including CO2, N2, and 60% H2 / N2.

[0038] FIG. 26 shows a comparison of OES spectra between N2 plasma and H2 / N2 plasma mixtures at varying ratios.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0039] FIG. 27 shows an intensity of N2 peak at 316.4 nm and Hapeak at varying H2 ratios.

[0040] FIG. 28 shows an evolution of the temperature of black mass over time in different plasma conditions.

[0041] FIG. 29 shows a schematic representation of a model of three-pronged plasma action which makes the short pre-treatment method extremely effective for facile room temperature leaching of critical minerals in mild solvents.DETAILED DESCRIPTION

[0042] The present disclosure generally relates to a method of recycling lithium- containing waste streams, and in particular embodiments, lithium-ion battery wastes. While the present disclosure refers to lithium-ion battery wastes, as will be appreciated by those skilled in the art, the method described herein can be readily applicable to other wastes, such as fly ash, coal ash, coal char, and electronic wastes, not limited to batteries and waste solar cells. The method described herein is a simple, environmentally friendly and cost-effective method to recover useful metals efficiently and also recover graphite for further use. A first step of treating the LIB waste with a plasma causes physical and chemical changes in the waste so that lithium can be first preferentially recovered from the waste and then other components, such as metals and graphite, can be recovered at high efficiency. The current methods are not limited to a particular battery waste but may be useful for treating commercial grade mixed lithium-ion battery waste, such as black mass. Black mass is conventionally a challenging material to recycle due to its complex composition, chemical heterogeneity and physical properties. However, the methods described herein provide an effective way to efficiently recycle black mass into useful materials. In the methods described, the plasma restores the lattice spacing, and removes SEI, as compared to black mass, producing residual graphite that is comparable in performance to commercial battery grade graphite. It will be understood that as used herein residual graphite is illustrative of recovered graphite.

[0043] Thus, in one or more embodiments, the present disclosure relates to a method for recycling battery waste that includes exposing the battery waste to a plasma to obtain a plasma-exposed battery waste and then preferentially leaching lithium fromPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT the plasma-exposed battery waste to obtain a treated battery waste. The plasma treatment may be conducted using conventional methods with conventional plasma gases. The plasma may be any suitable gas to generate a plasma, and in some embodiments, may be selected from the group consisting of CO2, N2, CH4 H2, Ar, NH3, O2, and combinations thereof. In some embodiments, plasmas containing hydrogen may result in more efficient recycling processes. The treatment time with the plasma may be any suitable treatment time, and may vary based on the type of plasma being used and / or the type of waste being treated. In some embodiments, the treatment may range from 2 minutes to 60 minutes. For example, the treatment time may range from a lower limit of any one of 2, 5, 7, 10, 15, 20 and 25 minutes to an upper limit of any one of 10, 15, 20, 25, 30, and 60 minutes, where any lower limit may be paired with any mathematically compatible upper limit.

[0044] Exposing the battery waste to a plasma creates both physical and chemical changes in the battery waste. Due to the fact that microwave generates a plasma, and the battery wastes described herein typically have a substantial amount of microwaveactive materials such as graphite, the battery waste experiences local microwave activation upon exposure to plasma. Furthermore, the plasma can break chemical bonds in the battery waste, which is believed to facilitate more efficient recovery of valuable components, as described in subsequent sections, and also further described in Examples herein.

[0045] As noted above, the methods described herein include exposing the battery waste to plasma then preferentially leaching lithium from the plasma-exposed waste, thereby leaching lithium into a first leachate. The leaching step may simply include soaking or stirring the waste in water for a period of time, which preferentially extracts lithium, leaving most other components in the battery waste. In contrast to conventional methods, this step may be conducted at room temperature and with impure water. For example, the water may include substantial impurities, such as effluent water from a sewage treatment plant. However, any type of water may be used as available. While room temperature leaching is an effective method for preferentially leaching lithium, elevated temperature leaching may be used for enhanced recovery of lithium. For example, in one or more embodiments, the plasma- exposed battery waste may be soaked or stirred in water at a temperature of less thanPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT30 °C, or less than 25°C, or less than 20°C. In some embodiments, the plasma- exposed battery waste may be soaked in water at a temperature ranging from 20°C to 100°C, which reduces the time of leaching.

[0046] The leachate produced from this initial leaching step, or the first leachate includes less than 20%, less than 15%, or less than 10% of non-lithium metals originally contained in the battery waste. In some embodiments, the first leachate may not contain any Co, Ni, or Mn. Furthermore, the leaching step in water is efficient enough that at room temperature that at least 70% of the lithium originally contained in the battery waste is leached into the first leachate in just one hour. At elevated temperatures, higher efficiencies can be achieved. Exemplary leaching results are described in the Examples herein.

[0047] After the lithium has been preferentially leached from the waste, the method includes leaching at least one non-lithium metal from the treated battery waste, thereby leaching the non-lithium metal into a second leachate. In contrast to conventional techniques that require the use of highly concentrated strong acids to leach metals from battery waste, this step may advantageously be performed using organic acids at low concentrations. For example, the treated battery waste may be soaked in an organic acid at room temperature or elevated temperatures for a time ranging from 5 minutes to one hour. The organic acid may be selected from the group consisting of citric acid, lactic acid, acetic acid, ascorbic acid, glycolic acid, malonic acid, formic acid, oxalic acid, uric acid, malic acid, tartaric acid, butyric acid, folic acid and combinations thereof. The organic acid may be used in a concentration ranging from 0.1 M (molar) to 2.0M. Additionally, the metals leached using an organic acid are not particularly limited and may include any metals, such as transition metals, post transition metals and metalloids. For example, in one or more embodiments, the non-lithium metal is selected from the group consisting of Co, Ni, Mn, Fe, Cu and Al. The metals may be leached with such efficiency that at least 90% of the metals originally contained in the battery waste are leached into the second leachate.

[0048] Finally, once the metals have been effectively and efficiently leached, graphite may also be recovered from the battery waste. While graphite is not typically targeted for recovery, its wide use in energy storage applications, as well as other appliedPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT materials, is increasing the demand for recycling and recovery. Furthermore, conventional recycling methods typically do not remove enough metals from the graphite to produce a useable material. However, the graphite recovered by the methods described herein may have sufficient purity for future use. Furthermore, in some embodiments, the graphite may have improved crystallinity with decreasing lattice spacings, making it suitable for reuse in energy storage devices. As such, the graphite recovered by the methods described herein may be suitable for reuse in energy storage devices.

[0049] As illustrated in FIG. 1, the present plasma pre-treatment allows a single step pretreatment which enables separate recovery, by leaching, of all critical minerals in mild solvents. In the present recycling process, the plasma may be utilized as a fast and efficient pre-treatment step.

[0050] FIG. 1 depicts a recycling process, where a commercial black mass is first exposed to plasma generated by ionizing specific gases in the microwave, thus providing a plasma pretreatment. The plasma exposed sample is first stirred in water at room temperature for the selective extraction of Li and then stirred in citric acid at room temperature for the complete removal of the transition metals (TMs). The residue left behind is the anodic graphite, that is also regenerated in the plasma process. The residue comprises the anodic graphite which is regenerated by the effect of plasma by the reduction of defects and lowering of interlayer spacing. The recovered graphite has excellent efficiency as LIB anode, surpassing commercial graphite in its activity. While illustrated in FIG. 1 and as described further below for LIB recycling, the present plasma pretreatment is a technological innovation that can serve as a versatile pretreatment step for hydrometallurgical extraction of critical minerals.

[0051] The recycling process employs non-thermal plasma as the battery recycling pretreatment. Plasma, the fourth state of matter, is an ionized gaseous system composed of highly energetic electronic species, which can be categorized into thermal and non-thermal plasma. In non-thermal plasma, the electronic species are at much higher temperatures than the neutral and ionic species, allowing it to be used for various purposes that cannot withstand the elevated temperatures produced by thermal plasma. The ionization of gases can be carried out using various sources, suchPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT as radio frequency waves and microwaves, depending on the process objectives. The non-thermal plasma may be microwave induced. Microwaves may be utilized to generate non-equilibrium plasma with high ionization power. Microwave plasma is an electrodeless discharge, where particles absorb the emitted microwave energy for a collision-less heating mechanism. In microwave plasma, a portion of the microwave energy is utilized in keeping the ions and electrons separated, allowing the plasma body to sustain. The microwave plasma may have higher ionization frequency as compared to other plasma generation systems, e.g., radio frequency discharge. High electron density and high electric field may be achieved in microwave plasma technology, leading to elevated electron temperatures. The microwaves as plasma sources may be cost and energy efficient. While different gas compositions have been examined for plasma, as described in the Examples below, a combination of H2 / N2 emerged as the most effective, with the layered metal oxides from LIB cathodes being reduced to their individual metallic or oxide states under the combined effect of hydrogen plasma, microwave and localized heating, making them easily extractable in green solvents.

[0052] The present recycling process may be utilized on commercial grade black mass to ensure >95% recovery of all the critical minerals involved. A short plasma pretreatment enables a subsequent -85% of Li leaching in water at room temperature, while -100%, for example >95%, of all transition metals (e.g. Li, Co, Ni, Mn, and / or Al) can be leached in a mild organic acid (1 M citric acid) at room temperature. Also, the recovered graphite after the leaching process was found to have been regenerated with its innate properties, suggesting its potential reuse in lithium ion batteries (LIBs). Notably, this microwave plasma pretreatment step is the sole energy consuming step in this process flow, since the subsequent metal extractions in lixiviants are all conducted at room temperature. The nature and behavior of plasma and its mechanism during the pretreatment have been studied in detail to provide an in-depth understanding. This is an important technological advancement that can be easily scaled to treat bulk scale commercial LIB waste irrespective of their chemical composition and can also attach economic viability to green lixiviant based processes by drastically reducing time and energy requirements.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0053] The black mass may be produced in bulk by shredding commercial grade LIBs. The commercial grade LIB may be in the form of a spent battery element. The spent battery element may be made up of stacked layers of battery materials, such as layers of the following, stacked in order: copper foil, anode (e.g. graphite), electrolyte (e.g. LiPFe), binder (e.g. polyvinylidene fluoride (PVDF)), cathode (e.g. Li + transition metals (TM)), aluminum foil. The shredding may accomplished by any shredding method suitable for shredding LIBs.

[0054] FIG. 2 illustrates a recycling system for carrying out the recycling process. Recycling system 200 may be automated. The recycling system 200 includes microwave cavity 202 capable of holding a container formed by connection of container top 204 having vacuum line 206 and gas inlet 208 entering therein to container bottom 210 having gas outlet 212 exiting therefrom. Container top 204 and container bottom 210 are suitable to connect and together hold black mass within the microwave cavity 202 while exposed to plasma generated by the microwave cavity 202. Conveyor belt 214 supports container bottom 210 and is adapted to shift container bottom 210 side to side for connection or disconnection with container top 204. The recycling system 200 also includes leaching tank 220 having tank inlet 222 and tank outlet 224. Tank outlet has at least two portions, a top portion 226 and a bottom portion 228, where the portions are defined by a valve 230 therebetween. Valve 230 includes a filter (not shown). Leaching tank 220 may be in position to receive plasma treated black mass from container bottom 210. Conveyor belt 214 is capable of shifting the relative positions of container bottom 210 and leaching tank 220. Li leachate collector 240 and TM leachate collector 242 are supported by conveyor belt 244. Li leachate collector 240 or TM leachate collector 242 may be in position to receive respective leachate, Li leachate or TM leachate, from tank outlet 224. Convery belt 244 is capable of shifting the relative positions of Li leachate collector 240 and / or TM leachate collector 242 relative to tank outlet 224.

[0055] In operation, recycling system 200 may proceed by a method as follows. At step 1, the method includes exposing a sample of black mass to plasma to produce a plasma exposed sample. The conditions of the exposing may include 1 Torr maintained in the container by vacuum line 206 and a gas flow at gas inlet 208 of 40 seem, where the gas is one or more of CO2, N2, CFL, and H2. The exposing mayPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT proceed for 5 - 15 minutes. At step 2, the method includes submitting the plasma exposed sample to the leaching tank 220. At step 3, the method includes leaching the plasma exposed sample with water for Li removal. The conditions of the leaching with water may include a temperature of 30°C and stirring for one hour. At step 4, the method includes collecting the Li in leachate Li leachate collector 240. The collecting includes removing the valve 230 for leachate collection. The collecting may include achieving 85% of Li leached. After the collecting, residual black mass containing TM and graphite remains in the leaching tank 220. At step 5, the method includes leaching the residual black mass with citric acid fortransition metal removal. The conditions of the leaching with citric acid may include a temperature of 30°C, stirring for one hour, and citric acid provided at a concentration in aqueous solution of Imolar (M). At step 6, the method includes collecting TM leachate in TM leachate collector 242 and recovering a graphite residue. After collecting the TM leachate, the graphite residue remains in the leaching tank 220. Recovering the graphite residue may include removing the graphite reside from the leaching tank 220. Recycling system 200 may be used for example for the experiments described in the examples below.

[0056] The examples below illustrate a recovery method that includes a plasma induced pre-treatment for commercial grade battery waste material (black mass). This very short pre-treatment enables the facile leaching of the critical minerals from the black mass into mild organic acids without compromising the quality of recovered graphite, which is otherwise not possible. Additionally, the pre-treatment allows selective leaching of Lithium in water from the black mass.

[0057] In the method of recovery illustrated in the examples, commercial grade battery waste (black mass) comprising the shredded down cathode active material (mixed oxides of lithium and transition metal) and anode (battery grade graphite) is pretreated using a microwave induced plasma method. The battery waste (black mass) also contains traces of the binder, electrolyte and current collectors. In this method, plasma is generated by microwave-induced ionization of different gases. The gases tested are CO2, N2 and H2, and their different ratios. Among the different gases, the plasma generated using H2, N2, CH4, Ar, O2, NH3 gas mixture is the most effective. The black mass exposed to plasma showed selective lithium leaching in water, whichPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT was not seen from the untreated sample. At 80°C, the black mass treated with H2 microwave plasma shows 83% Li leaching in water within 1 h, whereas the untreated sample merely shows 23% Li leaching in water. The selective Li leaching was also observed in water at room temperature where 73% Li leached out from the 5 minute plasma treated sample whereas from the untreated sample, the Li leaching was only 14%. A similar trend was observed in surface water as well. The leaching efficiency nearly increases with increasing the time of plasma treatment. The maximum leaching efficiency is observed from the sample exposed to plasma for 1 hr. Apart from selective leaching of lithium, the use of mild organic acids, e.g., within 30 minutes, 1 M citric acid at 80°C can leach 97% Co, 88% Ni, 97.3% Mn, 97% Li and 92% Al from the 5 min plasma treated sample. However, from the untreated sample, the leaching efficiencies of Co, Ni, Mn, AL, and Li are 39, 64, 63, 65, and 89%, respectively. The use of plasma also removes the intercalated lithium from the admixed graphite within the sample, which shows excellent crystallinity after 5-15 mins of plasma treatment. Hence after the removal of the metals by leaching in mild acids, the graphite can be recovered and reused in batteries. Hence this procedure allows the recovery of the different critical minerals involved in a battery, i.e., Li, Co, Ni, Al and graphite.

[0058] This procedure can be used on other waste streams with useful metals, e.g., fly ash, coal char, etc., to recover critical minerals. Different lixiviants can also be used to leach out metals more efficiently from the waste streams. Different compositions of plasma may also be used by changing the gas flow to get the best results.

[0059] The primary application of this technology is for use in the battery recycling industry, where each individual critical mineral can be recovered from a mixed waste of shredded down battery. The method is independent of the starting material nature and chemical composition and can be used on a wide variety of battery wastes. This alleviates the problems of long time and high temperatures associated with organic acid lixiviants. Additionally, selective leaching of lithium in water, a completely neutral green solvent, becomes possible after the plasma treatment. In future, it may also be used for other waste streams to recover critical minerals from them.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0060] The advantages of the recovery method is in its selectivity, ultrafast nature, environmental benignity, and ability to use higher solid-liquid ratios, which are discussed below.1. The primary advantage of this method is the ability to selectively leach lithium in water even at room temperature as a result of the plasma pre-treatment. The leaching of lithium from the untreated sample is only 14%, whereas from the sample subjected to 5-minute hydrogen plasma, it is 73%. Moreover, similar leaching rates are attained even using surface water. In addition, different agitation techniques such as sonication and planetary centrifugal mixer have found to be effective in the selective leaching of lithium in water within significantly shorter durations.2. In most cases with the existing battery recycling systems, the quality of the graphite gets compromised while extracting other critical minerals. However, with the incorporation of plasma, it has been found that we can recover graphite along with other minerals, without effecting their fundamental properties.3. The common hydrometallurgical processes for LIB cathode recycling involve using harsh corrosive lixiviants like inorganic acids and peroxides at high temperatures. This poses a threat to human health and the environment. Benign organic lixiviants like organic acids are generally not adapted industrially owing to the high temperature and time requirements. However, our method drastically reduces the time of leaching, making these environmentally friendly lixiviants economically viable. For example, at 80°C, within a duration of 30 minutes, a mild acid like 1 M citric acid can leach 97% Co, 88% Ni, 97.3% Mn, 97% Li, and 92% Al from the 5-minute plasma treated sample. However, from the untreated sample, the leaching efficiencies of Co, Ni, Mn, AL, and Li are 39, 64, 63, 65, and 89%, respectively.

[0061] Thus, in one aspect, embodiments disclosed herein relate to a method for recycling waste. The method includes exposing the waste to a plasma to obtain a plasma-exposed waste, and preferentially leaching lithium from the plasma-exposed waste to obtain a treated waste. The preferentially leaching lithium includes soaking the plasma-exposed waste in water at a temperature of less than 30 °C, thereby leaching lithium into a first leachate. The first leachate comprises less than 20% of non-lithium metals and at least 80% of the lithium originally contained in the waste. The water may be an effluent from a sewage treatment plant. The waste may be blackPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT mass from lithium-ion batteries. The plasma may include a gas selected from the group consisting of Ar, NH3, O2, CO2, N2, CH4 and H2. Exposing the waste to a plasma may include an exposure time ranging from 2 to 60 minutes.

[0062] The method may then further include leaching at least one non-lithium metal from the treated waste. The leaching at least one non-lithium metal includes soaking the treated waste in an organic acid, thereby leaching the non-lithium metal into a second leachate. The organic acid may be selected from the group consisting of citric acid, lactic acid, acetic acid, ascorbic acid, glycolic acid, malonic acid, formic acid, oxalic acid, uric acid, malic acid, tartaric acid, butyric acid, folic acid and combinations thereof. The organic acid may be present in a concentration ranging from 0.1 M to 2.0 M. The non-lithium metal may be selected from the group consisting of Co, Ni, Mn, Al, Cu and combinations thereof. The second leachate may include at least 90% of the non-lithium metal originally contained in the waste.

[0063] The method may further include recovering graphite from the treated waste. The graphite may be reused in an energy storage device.

[0064] It will be understood that while methods are illustrated herein, for example in FIG. 1 and FIG. 2, with a water leaching step preferentially leaching lithium in water followed by an acid leaching step leaching a metal, for example a non-lithium metal, in an acid, the water leaching step is not required. Thus, the present inventors contemplate methods as described herein for recycling waste that include exposing the waste to a plasma to obtain a plasma-exposed waste; and leaching a metal in an acid from the plasma-exposed waste to obtain a treated waste. The methods may optionally further include a water leaching step. When the water leaching step is not included, lithium may be leached with other metals in the acid leaching step. When the water leaching step is included, lithium may be preferentially leaching in the water leaching step. When the water leaching step is included, remaining lithium after the water leaching may also be leached in the acid leaching step.

[0065] A better understanding of the present invention and of its advantages will be obtained from the following examples, offered for illustrative purposes only. The examples are not intended to limit the scope of the present invention in any way.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCTEXAMPLESOverview

[0066] A short plasma pre-treatment showed unprecedented efficiency in leaching all the metals in mild green solvents at room temperature and regenerating the residual graphite from commercial black mass. Different gases were explored for the generation of plasma, and a combination of H2 and N2 was found to be most effective in increasing the leaching. Compared to the conventional pretreatment strategies, this novel approach comprising the combination of microwave plasma treatment and green lixiviants has proven to be an overall recycling strategy that can recover all the critical minerals involved, including the graphite. Using water as a lixiviant at room temperature, around -85% of lithium was recovered selectively from the plasma- treated black mass, while the amount that could be recovered from the untreated black mass was barely -25%. In citric acid, the LEs of metals from the plasma-treated black mass were around 95%, whereas that from the untreated black mass was only -27%. Studies performed on the recovered graphite revealed the regenerative capabilities of plasma by facile removal of lithium and SEI, enhancing their reusability potential and lifecycle. This process opens a new world of possibilities in the domain of battery recycling and can become an extremely important technology in the future. Overall, this work marks an important technological advancement that can be extended other hydrometallurgical processes besides LIB recycling as well.

[0067] The steps involved in the experimental procedure for this technology are as follows:1. The black mass is kept in a porcelain boat and introduced in a quartz tube within a microwave oven. A vacuum pump is connected to the quartz tube to maintain low pressure. Gas flow is ensured through the tube at a constant rate. The microwave is irradiated at 1000W to generate plasma. The nature of plasma varies as per the gas chosen. The black mass is exposed to plasma for different time scales starting from 2 min to 60 min.2. After plasma exposure, the black mass is put in different lixiviants (water, mild organic acids) and heated at a certain temperature with stirring. It is then filtered toPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT recover the graphite. The leachate is analyzed to determine the concentration of the cathode metals leached out.3. A solution of sodium hydroxide and ammonium hydroxide is added dropwise to the filtrate to precipitate the dissolved transition metal cations. In a second step, sodium carbonate solution is added at elevated temperatures to ensure lithium precipitation.General Procedures

[0068] The in-house-built microwave reactor mainly consisted of a microwave oven (BP-093, Microwave Research & Applications Co.), a quartz tube, mass flow controllers, and a vacuum pump. The microwave oven operated at 2.45 GHz with 1000 W output power. The microwave cavity was a rectangular waveguide-based chamber with dimensions 13 7 / 8” w x 8 1 / 8” h x 14 5 / 8” d. A quartz tube (outer diameter: 38 mm; inner diameter: 35 mm; length: 4 feet) was inserted horizontally through the center of the cavity. The length of the typical plasma zone was ~35 cm based on optical observation. A crucible containing BM was loaded into the quartz tubing and placed at the center of the microwave oven. The quartz tubing was then pumped down to the vacuum. The plasma was ignited when the desired gas was supplied into the quartz tubing through mass flow controllers. During the treatment, the total gas flow was maintained at 100 seem and the pressure was approximately 1 Torr.

[0069] Hydrogen gas was supplied from a cylinder housed in a ventilated gas cabinet and connected to the plasma reactor via hydrogen-compatible stainless-steel gas lines equipped with flashback arrestors. All plasma experiments were conducted under a canopy hood with active exhaust. The total system pressure was maintained at approximately 1 Torr, minimizing flammability risk. For safe operation, the installation of hydrogen leak detectors and automatic shutoff valves is recommended to provide continuous monitoring and rapid response in case of leaks.

[0070] The OES spectra were collected using an Avantes AvaSpec-ULS4096CL-EVO spectrometer, with an integration time of 10 ms.

[0071] The temperature of black mass during plasma treatment was measured by a Williamson dual -wavelength fiber-optic pyrometer with a temperature range of 600- 1900 °F (316-1038 °C).PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0072] Since the black mass BM was extremely heterogeneous, LEs of each sample were determined by considering the total amount of metals in that amount of sample. For this, a double step leaching experiment was performed. Each leaching experiment was performed over 5 replicates and the average leaching data has been presented with error bars.

[0073] 50 mg of the pristine / plasma exposed sample was taken in a vial. 5 ml DI water / 1 M citric acid is added to it. The mixture is stirred at room temperature for Ih. It is filtered and 100 pL of the filtrate is taken to prepare the ICP solution.

[0074] The residue from the previous step is dissolved in 10 ml aqua regia, which is heated at 60°C for Ih and then left overnight at room temperature. 100 pL is taken from the resultant solution to prepare solution for ICP.

[0075] The metal filtrates obtained from the leaching process were quantified using a PerkinElmer Avio 550 ICP-OES system. 100 pL from leachate solutions were taken from each of the leachate solutions and diluted with a 2% aqueous solution of nitric acid (HN03) to make 10 ml solutions. The calibration curves were generated using at least 5 out of 7 ICP standard solutions (100, 50, 10, 5, 1, 0.5, and 0.1 ppm), and then only the results with correlation coefficients of equal or greater than 0.999 were used to calculate the leaching efficiencies (LEs). Two wavelengths per element were used in the axial mode, namely, cobalt (228.616 and 230.786 nm), lithium (670.784 nm (radial mode) and 610.362 nm), and nickel (231.604 and 341.476 nm). The gas nebulizer flow rate range was set between 0.45 and 0.75 min-1.

[0076] If the metal concentration determined from step 1 is ml and that from step 2 is m2, the LE was determined as

[0077] 100Characterization of the Commercial Black Mass BM

[0078] The substrate chosen for the examples is a black mass BM, obtained from commercial sources, which has been produced in bulk by shredding commercial grade LIBs. The commercial grade LIB may be spent.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0079] Powder X-ray diffraction (PXRD) was performed on the BM. The PXRD pattern of the BM showed peaks corresponding to LCO (LiCoCh) and NMC (LiNixCoyMmCh) along with strong peaks for graphite. The most prominent peak in the PXRD pattern of BM was at 20 = 26.5°, corresponding to the (002) plane of the graphite, indicating a high percentage of anodic graphite being present in the sample. Additionally, peaks at~20 « 18.7° and 18.9° corresponded to the (003) planes of NMC and LCO, respectively, while peaks at 20 « 44.3° and 44.6° corresponded to the (104) planes of NMC and LCO, respectively.

[0080] Scanning electron microscopy (SEM) was performed on the BM. Under SEM, BM showed the presence of primarily three types of particles - spherical NMCs with ~20 pm diameters, irregular block like LCOs and particles of spherical graphite, as shown for example in FIG. 7, in the leftmost column, for 0 min. pretreatment.

[0081] Thermogravimetric analysis (TGA) was performed on the BM. The TGA analysis performed in an inert atmosphere revealed that the BM did not undergo any major decomposition until 750°C. This ensures the intactness of the minerals in the BM during microwave plasma pre-treatment. A -10% weight loss observed from 180°C to 550°C was attributed to degradation of the Polyvinylidene fluoride (PVDF) binder and electrolyte present in the sample.Exposure to Different Plasma Compositions

[0082] The black mass BM was initially exposed to the microwave plasma using different gas compositions for 5 mins including CO2 (CO2P5), N2 (N2P5) and H2 / N2 (60%H2, 40% N2) (H2P5). The samples were weighed before and after the plasma exposure and did not undergo any significant weight loss during the process, which aligns well with the TGA findings. The resultant materials were analyzed using PXRD, SEM and their surface areas were determined by recording their N2 adsorption isotherms at 77K. The most remarkable change observed in the PXRD is in the peaks corresponding to the (003) planes of NMC811 and LCO at 20 = 18.68° and 18.9°, respectively, which correspond to the plane containing intercalated Li (FIG. 3). In CO2P5, both these peaks start shifting to lower angles, indicating an increase in the lattice spacing in the c direction owing to a repulsion between the oxygen layers due to a Li deficient state (FIG. 3). Additionally, the peak at 20 =18.9° decreases inPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT intensity, indicating the breaking down of the Li intercalation. This is associated with a decrease in the ratio between the intensity of the (003) and (104) peaks of both LCO and NMC811 (I(oo3) / I(io4)). In N2P5, in addition to the shifting to lower angles, these peaks are also significantly diminished in intensity, indicating the breaking down of the Li intercalation in both LCO and NMC. In H2P5, the peaks at 20 = 18.68° and 18.9° completely disappear, implying complete breakdown of the Li intercalation. The peaks corresponding to the (104) planes of both NMC811 and LCO at 20 = 44.3° and 45.2° also disappear, indicating a complete disruption of the LCO and NMC811 lattices. Additionally, significant changes are also observed in the peak at 20 = 44.5° corresponding to (101) plane of graphite, which is discussed in detail in Section 2.4.Room Temperature Metal Extraction in Mild Solvents

[0083] The increase in surface area and generation of cracks can enhance leaching of the TMs and Li from the black mass by allowing the facile seeping of the lixiviant in the material. Additionally, the disruption of the LCO and NMC crystal structures can be instrumental in aiding leaching. BM and the plasma exposed black masses were stirred at room temperature (25°C) for 1 h with water as the lixiviant at a Rm / v ratio of lOmg / ml. At room temperature in water, we observe a selective leaching of Li from the samples which increases in the same order as the BET surface area, from 21.8% in BM to 74.5% in H2P5. The leaching of Li is associated with the leaching of small amounts of Al from all of the samples, while no other TMs are detected in the solution (FIG. 4). Hence due to the application of merely 5 mins of 60% H2 plasma, selective leaching of 74.5% Li can be obtained simply by stirring in water at 25°C within an hour. Previously, at 25 °C, only 25% LE of Li in water from NMC cathodes has been reported in 3 h. Next, in order to leach out the TMs, a mild organic acid, namely 1 M citric acid is employed at room temperature (25°C) for 1 h. As expected, we observe a drastic improvement in the LEs in the plasma exposed samples, with H2P5 showing the highest LEs in all cases. Here, Co, Ni, Li and Mn LEs from BM are 9.7, 9.1, 27.4, and 31.8% respectively. In H2P5, the LEs increased remarkably, with LE for Co being 94.9%, that for Ni being 80.6%, 96.3% for Li and 94.5% for Mn, respectively (FIG. 5). Hence a short plasma pre-treatment can attach commercial viability to green solvents, e.g., water or citric acid by ensuring high LEs without the expenditure ofPATENT APPLICATION ATTORNEY DOCKET NO. 17500-280W01 CLIENT REF. NO. 2025-030-PCT further heat energy. Further details on the morphological changes, adsorption and leaching of the different plasma exposed samples are discussed below.

[0084] Analysis of the metal content was performed on the BM. The BM as digested using aqua regia in a microwave digestor, and the concentrations of the different metals were determined using ICP-OES. However, since it was a commercial shredded down battery wastes, the BM contained large particles, with extreme local heterogeneities. Hence it was difficult to conclude a uniform metal concentration from the BM. Table 1 lists metal content in the samples after exposure to plasma of different composition for 5 mins. The particles after exposure to plasma of different composition for 5 mins are illustrated in FIG. 6.Table 1

[0085] Under SEM, both LCO and NMC particles appear to be shrunken and cracked due to the plasma exposure (FIG. 6). However, in all cases, the spherical graphite particles remain unaffected by the plasma exposure. While the NMC particles in BM are secondary spherical structures with diameters ~20 nm, comprising closely packed primary granules, exposure to plasma causes their diameters to shrink and the particles to crack (CO2P5). The packing of the primary particles is also affected owing to crack propagation in the spherical morphology, as seen in N2P5 and spherical structures also get deformed to oblong shapes (H2P5). However, in all cases, the spherical graphite particles remain unaffected by the plasma exposure.

[0086] Since the exposure to 60% H2 plasma shows the highest LEs in all cases, the time of plasma exposure was extended for 15 mins (H2PI5), 30 min (H2P3O) and 60 mins (H2P6O) to see the effect on the black mass (FIG. 7). FIG. 7 shows thePATENT APPLICATION ATTORNEY DOCKET NO. 17500-280W01 CLIENT REF. NO. 2025-030-PCT comparison of the different characteristics of the samples exposed to H2 plasma for different time durations. Under SEM, with the increase in plasma exposure time, the NMC spheres are deformed, undergo shrinkage, and also show cracks. The secondary granules in this morphology also fuse and lose their distinct regular shape (FIG. 7). Similarly, for LCO, the particles appear to crack and break down to smaller pieces upon increasing the time of plasma exposure. However, the spherical graphite particles remain unharmed even in H2P6O when exposed to plasma for 60 mins.

[0087] Adsorption isotherms were obtained from the BM. The generation of cracks in the BM particles can lead to increased surface area. Hence to investigate, N2 adsorption was performed on all the samples at 77 K. All the samples exhibit Type IV isotherms indicating mesoporous structures. Additionally, the plasma exposed samples exhibit the formation of hysteresis, indicating the generation of connected pores with the possibility of capillary condensation. The total volume of N2 adsorbed increased gradually in the order of BM<CO2P5<N2P5<H2P5, with H2P5 showing a total uptake of 29.01 ml / g N2 at P / PO =1 (Table 2). Although the increase in BET surface area from BM is minor in case of N2P5 and CO2P5, it was almost tripled in H2P5 to 17.91 m2 / g from 5.6 m2 / g in BM. Upon increasing the plasma exposure time to more than 15 mins, there was no significant improvement in the N2 uptake amount or the BET surface area (Table 2). Table 2 illustrates that the values of surface area (BET) increase from BM to H2PI5.Table 2PATENT APPLICATION ATTORNEY DOCKET NO. 17500-280W01 CLIENT REF. NO. 2025-030-PCT

[0088] The plasma exposed samples exhibited the formation of hysteresis, indicating the generation of connected pores with the possibility of capillary condensation. H2P5 showed the highest adsorption, showing a total uptake of 29.01 ml / g N2 at P / PO =1 and a BET surface area of 17.91 m2 / g (Table 1). Table 2 lists BET surface area and N2 adsorption capacity of the samples at 77K.

[0089] Table 3 lists comparison of leaching efficiency and the ID / IG in the residual graphite in BM samples exposed to EE plasma for the increased durations of 0 min., 5 min., 15 min. 30 min., and 60 min. corresponding to FIG. 7 and Table 2. Table 3 illustrates the Li extractability increased from BM to H2PI5.Table 3

[0090] It was observed that the original material (BM) had NMC and LCO, where Co and Ni oxidation states are +3 and +4. In H2P15, there is no trace of NMC or LCO. Instead, metallic Co andNi (oxidation state 0), CoO, NiO (oxidation state +2), Co3O4 (oxidation state +3), Li2O, LiOH, MnO are found in H2P15 (Figure 7). Among the materials tested for Figure 7, H2PI5 was an optimal residual graphite. As illustrated in Figure 7 and discussed above, longer treatment times tended to degrade the residual graphite as compared to H2PI5, whereas, as illustrated in Tables 2 and 3, shorter treatment times tended to worsen properties and / or performance as compared to H2P15.

[0091] Most remarkably, as seen from the PXRD analysis, beyond 5mins, the peaks corresponding to the CAMs LCO and NMC completely disappear (FIG. 8). The PXRD contour plot clearly showed that the while the peaks for LCO and NMCPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT completely disappear beyond 5 mins, the graphite peaks remained intact throughout and widens around 60 mins of plasma exposure time. At 15 mins, several new peaks appeared which can be attributed to different metallic and metal oxide species originating from the reduction of the CAM material. The presence of metallic Co and Ni alongside their oxides is noted, along with MnO, and Li2O. The N2 adsorption isotherm at 77K shows an increase in the BET surface area (FIG. 7) and the total N2 uptake upon increasing the time of plasma exposure from 5 mins to 15 mins (FIG. 9, Table 2). All samples exhibit a Type IV isotherm, with a wide hysteresis.

[0092] Leaching of the critical minerals was attempted from the samples exposed to 60% H2 plasma for different time durations using mild solvents previously used, i.e., water and 1 M citric acid. First, water was used as a lixiviant at room temperature while stirring with a Rm / v of lOmg / ml and afforded selective Li leaching from all the samples. The percentage of Li leaching from the pristine BM is 21.6%, which increases to 74.5% in H2P5 after 5 mins of plasma exposure, and to 81.1% in H2PI5 after 15 mins of plasma exposure. However, beyond 15 mins, the Li LE does not increase significantly and the LEs from H2P3O and H2P6O are 83.3 and 81.3% respectively (FIG. 10). A similar trend is observed in the case of the TM leaching, where after 15 mins of plasma exposure, -100% LE is observed from all TMs and Li. In the case of Ni, the LE peaks at H2PI5 (93.9%) and is somewhat decreased to -82% in H2P3O and H2P6O (FIG. 11). The formation of Li2O due to the plasma exposure causes the Li to be extremely labile and easy to leach, as a result of which LEs of -80% can be obtained by simply sonicating H2P6O in water for 30 mins at room temperature or rotating it in a thinky mixer for 3 mins. Additionally, surface water was obtained from Buffalo Bayou in Houston, Texas, and was used for Li leaching without further purification (FIG. 12). After stirring H2P6O in this surface water at room temperature for 1 hr at a Rm / v of lOmg / ml, -75% Li leaching was observed, proving the efficiency of the plasma pretreatment for a variety of lixiviants.

[0093] In order to check the influence of the percentage of H2 gas in the plasma composition, a gas mixture containing 90% H2 and 10% N2 was used to generate plasma using microwave. However, when leaching was performed in 1 M citric acid, no further increase in LEs were observed, indicating that 60% H2 is sufficient to achieve the highest LEs (FIG. 13).PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0094] The leachate solution in citric acid was treated with 1 M oxalic acid to obtain TM oxalate as precipitate. The obtained precipitate had a regular cuboidal morphology as observed under SEM. This precipitate was successively grinded with LiOH to lithiate it and annealed at high temperature to obtain NMC. The NMC obtained showed the typical PXRD signature and clustered morphology of NMC.Understanding the Effect of Plasma on Metals

[0095] While SEM and XRD indicate that plasma disrupts the morphology and lattice structure of the CAMs, allowing easy seepage of lixiviants for facile leaching, it is also important to understand the chemical changes brought about by the plasma. Close inspection of the PXRD pattern of EEPIS reveals the presence of several species, primarily metallic and oxide states of the metals reduced from the CAMs (FIG. 14). While Co and Ni show signature peaks for their different oxides as well as their metallic states, Mn shows existence as MnO. The Li that was present in the CAMs in BM is converted to a mixture of Li2O and LiOH. This is further corroborated by examining the XPS spectra of Lils and Co2p before and after plasma treatment. The Lils spectrum in BM shows the presence of various species, e.g., LiF, LiOH and Li2O that occur in the SEI. After plasma exposure, LiF degrades owing to the high temperature and is not observed in H2PI5. Additionally, the Li from NMC and LCO assumes small molecular forms, e.g., LiOH and Li2O, and the Li2O / LiOH ratio significantly increases (FIG. 15). In BM, deconvolution of the Co2p band reveals the presence of both Co3+and Co2+peaks at 784.1 eV and 788.4 eV, respectively. Although delithiation can increase the oxidation states of Co within the bulk particles in cycled CAMs, surface reconstruction can lead to partial reduction of Co3+to Co2+, leading to the co-existence of both states.45,46After exposure to 60% H2 plasma for 15 mins, i.e., in H2PI5, while both Co3+and Co2+peaks exist, the intensity and area of the Co2+peak significantly increases, indicating towards reduction of the Co3+phase from BM (FIG. 16). Additionally, there is also the appearance of a band at 794.9 eV, corresponding to the Co2pi / 2 band of metallic Co, confirming reduction due to exposure to plasma. The Ols spectra in BM was centered at 533.5 eV, with a wide band corresponding to organic carbonates owing to the binder and delithiated CAMs. In H2PI5, there was a significant enhancement in the peak at 532.4 eV corresponding to crystalline inorganic oxides, owing to the formation of the metallic oxide phasesPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT during plasma exposure. The reduction of the metals to their respective oxides or metallic forms aided in their enhanced leaching in citric acid. In case of Li, Li2O and LiOH both had excellent solubilities in water at room temperature, leading to the high Li LE in water at room temperature after plasma exposure.

[0096] The ToF-SIMS analysis carried out on pelletized BM and H2PI5 further confirmed the findings of the XPS. A cesium ion beam was employed to etch the sample, and the signals received from up to a depth of 10 nm were integrated for cumulative analysis. The ratio of intensities of different species present in H2PI5 to that in BM was obtained. A value <1 indicated a lowering in the concentration of the particular species after plasma treatment. The presence of Co2+significantly increased post-plasma treatment, which is in accordance with the XPS analysis. In case of Li, while LiOH and Li2COs species decreased, Li2O increased to a great extent, corroborating the findings from XPS. From the PXRD, XPS and ToF-SIMS analysis, it was thus clear that the H2 plasma created a highly reducing environment, which reduces the metallic species in the CAMs, thereby disrupting the layered structures and aiding in the subsequent leaching.Anodic Graphite Regeneration

[0097] The extraction of all the metals from the plasma treated black mass by the action of citric acid results in the recovery of the anodic graphite as the residue. During cycling in LIBs, the solid electrolyte interface (SEI) is deposited as an interfacial layer on the graphite anode. Additionally, the constant lithiation and delithiation causes expansion of the graphitic layer, leading to volume expansion and eventual decline in energy storage activity. These structural defects cannot be eliminated by simple isolating the graphite by physical means, e.g., froth flotation, and additional regenerative methods are of utmost importance to facilitate the reuse of graphite in LIBs. Exposure to plasma regenerates the graphite structure by restoring its structure, while enabling facile removal of the metals. The comparative PXRD pattern of graphite recovered from BM (Gr@BM) with the graphite recovered from plasma exposed samples (Gr@H2P5, Gr@H2P15, Gr@H2P30 and Gr@H2P60 obtained from H2P5, H2PI5, H2P3O and H2P6O, respectively) shows distinct shifts in the signature graphite peaks at 20 = 26.6° and 44.4° corresponding to (002) and (101) planes (FIG.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT17) respectively. The peak at 20 = 26.6°, corresponding to the inter-layer graphitic spacing, exhibits a shift towards higher angles in the Gr@H2P5 and Gr@H2P15 from that in BM. This can be attributed to the lattice contraction of the graphite and complete delithiation of the graphite under the influence of plasma. The lattice contraction imparted by 15 minutes of plasma treatment is further corroborated by the lattice spacings visible in the Transmission Electron Microscope (TEM) image, which is 0.343 nm in Gr@BM and is reduced to 0.328 nm in Gr@H2P15 (Table 4). However, beyond 15 mins, the peak corresponding to the (002) plane shifts back towards lower angles in Gr@H2P30 and Gr@H2P60, implying lattice expansion. A similar trend is followed by the peak at 20 = 44.3° corresponding to the (101) plane, which also shifts to higher angles in H2P5 and H2PI5 and shifts back to lower angles in Gr@H2P30 and Gr@H2P60. This indicates that exposure to plasma for a long duration disrupts the lattice structure owing to thermally induced lattice strain and the etching effect induced by H2. The H2 plasma attains a temperature of ~700°C (FIG. 27) and hence longer exposure initiate thermal degradation in the graphite structure. The recovered graphite was also analyzed using Raman spectroscopy, which corroborates the conclusions drawn from the PXRD analysis. The G band at -1550 cm'1, arising from the sp2 hybridized graphitic carbon, becomes sharper and blueshifts with exposure to plasma for 5 and 15 mins (Gr@H2P5 and Gr@H2P15, respectively) (FIG. 18). Additionally, the D band at 1350 cm'1also diminishes in intensity from BM with exposure to plasma till 15 mins of exposure time. Beyond 15 mins, however, the D band regains intensity owing to the appearance of defects. The ID / IG ratio is 0. 872 in BM, which reduces to 0.097 in Gr@H2P15 owing to structural regeneration and again increases to 0.766 in H2P6O owing to defect formation (Table 4). The results shown in Table 4 illustrate decreased lattice spacing by 4.4%, lower defects by 88% of the residual graphite as compared to black mass. The lowering of ID / IG illustrates the lower defects. This lowering of defects is also shown in Figure 18. The decreased lattice spacing and lowered defects each illustrate improved crystallinity.Table 4PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0098] In addition to the G and D bands, the plasma exposed samples also exhibited the appearance of the 2D band at 2700 cm'1which follow a similar trend as the above- mentioned peaks. The deconvolution of the Cis band in the XPS spectrum of Gr@BM showed the presence of bands corresponding to C=C, C-O, and C=O. Additionally, the presence of C-F can be observed, originating from the PVDF binder used in the manufacture of the battery. Gr@H2P15 shows a sharper Cis band, with a lower intensity of C-0 and C=O bands, and a sharper band corresponding to C=C.

[0099] The lithiation / delithiation behavior of the Gr@BM, Gr@H2P 15 and commercial battery-grade graphite (CGr) was investigated using cyclic voltammetry (CV) at a scan rate of 0.1 mV / s over a voltage range of 0.001-2.5 V for the first three consecutive cycles. The CV of the neat sample Gr@BM exhibits a pronounced peak at -0.51 V during the first cycle, which is attributed to the formation of the solid electrolyte interphase (SEI) layer resulting from the reductive decomposition of the electrolyte on the graphite surface. This peak disappears in subsequent cycles (FIG. 19), indicating the formation of a stable SEI layer that facilitates Li-ion passivation during lithiation / delithiation. From the second cycle onward, the -0.51 V peak is absent, signifying the stabilization of the SEI. The CV curves for the second and third cycles of the neat sample show strong overlap, reflecting high electrochemical reversibility. Additionally, minor humps observed between -1.5-2.5 V can be attributed to the presence of metal impurities in Gr@BM owing to incomplete leaching. The CV profiles of the Gr@H2P15 (FIG. 20) and CGr (FIG. 21) both demonstrate a reduction peak appears around -0.61 V during the first cycle, also attributed to SEI formation, which disappears in the following cycles. Second cycle onward, the CV of both samples demonstrate excellent reversibility. The galvanostatic charge-discharge (GCD) profiles at a current density of 100 mA / g for the second cycle of all three compositions are shown in FIG. 22. The second-cycle GCD profiles at a current density of 500 mA g1are displayed in FIG. 23. Notably, anPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT increase in reversible capacity after several initial cycles was observed, a common phenomenon for such electrode materials. This behavior is attributed to the initially high cell polarization, which decreases as the cell becomes activated, leading to improved reversible capacity. This trend was evident in both Gr@H2P15, and CGr (FIG. 23). FIGS. 19, 20, 22, and 23 illustrate the improved performance of the residual graphite as compared to black mass. The present inventors believe that this is due at least in part to the decreased lattice spacing, improved crystallinity, and lower defects of the residual graphite as compared to black mass, illustrated by Table 4. FIGS. 20, 21, 22, and 23 illustrate the comparable performance of the residual graphite to commercial battery grade graphite.

[0100] Cycling stability tests were further conducted at a current density of 100 mA / g within a 0.001-2.0 V voltage range for the first 25 cycles across all three compositions (FIG. 24A). Gr@BM shows an initial charge / discharge capacity of -149.9 / 154 mAh / g and retains a reversible capacity of -67.5 mAh / g after 25 cycles, with nearly 100% coulombic efficiency. Gr@H2P15 exhibits a significantly higher initial charge / discharge capacity of -262.5 / 279.7 mAh / g and maintains a reversible capacity of -245 mAh / g after 25 cycles, also with -100% coulombic efficiency. In comparison, CGr delivers an initial charge / discharge capacity of -243.3 / 247 mAh / g and retains a reversible capacity of -250 mAh / g after 25 cycles, again with -100% coulombic efficiency.

[0101] Long-term cycling stability at high current rates is a crucial parameter for evaluating battery electrode materials. To assess this, we conducted 1000 continuous charge-discharge (GCD) cycles at a current density of 500 mA g1for all three compositions (FIG. 24B). CGr exhibited an initial reversible capacity of -64.5 mAh g stabilizing at -60 mAh g1after 1000 cycles with nearly 100% coulombic efficiency. In contrast, Gr@H2P 15 showed a much higher initial reversible capacity of -134 mAh g1, which stabilized at -97 mAh g1after 1000 cycles, maintaining -100% coulombic efficiency and -72% capacity retention. Gr@BM started at -51 mAh g1and stabilized at -46 mAh g1after 1000 cycles. The minor capacity fading in this case could be attributed to structural defects and morphological degradation of the electrode surface.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0102] GCD profiles recorded at various intervals from the 5th to the 1000th cycles were obtained for Gr@BM, Gr@H2P15, and CGr, respectively. It was observed that Gr@H2P15 sample showed much better LIB anode performance than the commercial graphite. The present inventors believe that the battery activity demonstrated by Gr@H2P15 is one of the best achieved from graphite recovered from spent LIBs.

[0103] Further, the reversible capacity restoration property for the Gr@H2P15 sample exhibited significantly higher stability compared to Gr@BM and CGr, demonstrating -69% reversible capacity retention after 1000 cycles. This highlights the superior electrochemical performance of the Gr@H2P15 sample. The present inventors believe that the proposed recycling strategy offers a promising alternative approach for recovering graphite from spent battery materials.

[0104] In comparison, recycled graphite recovered from spent lithium-ion batteries (LIBs) by conventional means is typically more suitable for secondary applications that place lower demands on structural integrity, e.g., in supercapacitors, polymer composites, or water purification systems. Due to the structural defects accumulated during battery operation, this graphite rarely meets the stringent performance requirements for reuse as LIB anode material. Even when reintroduced into batteries, it often exhibits poor electrochemical activity and limited cycle life.Understanding the Plasma Action

[0105] Optical emission spectroscopy (OES) was employed to understand the nature of the plasma that the black mass is exposed to. OES allows the non-intrusive analysis of the emission from the excited plasma species while they undergo spontaneous relaxation, which provides valuable insights into the nature of the plasma discharge.5,6 The OES spectra obtained from plasma originating from different gaseous sources collected at the center of the microwave system is represented in FIG. 25. For CO2 plasma, the CO third positive (3P) system and CO Angstrom system are observed, which correspond to the b32+-> a3nrand->1!! transitions, respectively.7 Additionally, prominent peaks at 778.1 nm (3p5P -> 3s5S) and 845.4 nm (3p3P -> 3s3S) represent atomic oxygen (O), which facilitates the oxidation of metals and graphite during plasma treatment of black mass. In N2 plasma, various nitrogen-related emissions are evident, such as N2 second positive (2P) systemPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT(C3n -> B3n), N2+ first negative (IN) systemand N2 first positive (IP) systemalongside peaks from atomic nitrogen (N).9 When H2 is introduced into the N2 plasma, the OES spectra reveal additional peaks corresponding to hydrogen emissions, specifically the Ha and HP lines at 657.0 nm and 486.9 nm, respectively FIG. 26. The OES spectra also shows that increasing H2 content in the H2 / N2 mixture leads to an enhanced intensity of the Ha peak, while those related to N2 steadily diminish, as has been observed by tracking the intensity of the Ha peak and the N2 peak at 316.4 nm across different H2 ratios FIG. 27.

[0106] The temperature of the black mass during the plasma treatment was measured using an infrared (IR) pyrometer (FIG. 28). The maximum temperature attained during the plasma was found to be in a range near 700°C. The black mass heats up rapidly, reaching 600 °C within the first three minutes of exposure. A stable temperature range is achieved within -5-10 mins, with the stabilized temperature calculated as the average temperature between 10 to 30 mins of plasma exposure. Among the different plasma sources explored, pure N2 plasma produced the highest stabilized temperature of 749.1 °C. The addition of H2 led to a reduction in stabilized temperature, with the temperature being 720.0°C for 10% H2, 695.1°C for 30% H2, and 708.4°C for 50% H2, respectively. For 90% EE, the stabilized temperature significantly decreased to 664.0°C, which can be attributed to the instability of plasma in a predominantly H2 environment. The temperatures induced by plasma treatment are sufficiently high to facilitate metal reduction within the black mass. The rapid heating effect achieved through plasma treatment enables efficient processing in a short duration, and the stability of the induced temperature over extended periods suggests its potential for sustained, long-term treatments.

[0107] While not wishing to be limited by theory, the efficacy of the microwave plasma pretreatment in LIB recycling may be attributed to a combination of various factors (FIG. 29), as described below.

[0108] A factor is physical lattice disruptions by plasma species. As has been discussed above, the plasma species, generated by the ionization of gas in microwave, collide with the BM particles to etch and crack the CAM particles. This increases their porosity and allows easy seepage of lixiviants for facile leaching (FIG. 29 Panel I).PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT

[0109] Another factor is reductive environment. According to the TGA, the binder PVDF and additional hydrocarbons formed from electrolyte residues degrade in the 200-300°C range, forming amorphous carbon, that initiates carbothermic reduction of the CAM. This leads to the generation of metals, individual metal oxides and carbon monoxide. Additionally, the black mass is also exposed to an extremely reductive environment created by the microwave-induced hydrogen plasma. Hydrogen plasma is considered to be an even more powerful reductant than gaseous hydrogen, owing to the concentrated stream of donor species that can participate in reduction reactions. Moreover, the reduction of metal oxide in the presence of hydrogen ions at around lOOOK is thermodynamically more favorable for metal oxide reduction rather than molecular hydrogen.57 (FIG. 29 Panel II)

[0110] Yet another factor is surface plasma from graphite. A major component of BM is graphite, which is an excellent absorber of microwaves. Hence, during the pretreatment process, the absorption of microwave occurs uniformly throughout the surface resulting in rapid homogenous temperature elevation across the sample (FIG. 29 Panel III). It has been recently demonstrated that in a microwave field, graphite self-induces an electric field on its surface, leading to plasma discharges that create intense localized heating domains, that regenerate the graphite by removal of the SEI and residual binder.58 This mechanism is potentially active in this case as well, and the localized thermal stress is propagated to adjacent CAM particles, leading to lattice disruptions. This also allows the effect of plasma to spread throughout the bulk of the BM and not just the surface.

[0111] A thermal pre-treatment method at 900°C for 2 h failed to achieve comparable LEs as the short plasma pre-treatment in 1.0 M citric acid. Additionally, thermal pretreatment led to the appearance to defects and lattice expansions in the graphite leading to the shifts of the PXRD peaks corresponding to (100) and (002) planes of graphite to lower angles. A preliminary lab scale comparative cost analysis of both pre-treatment processes also indicated that the plasma process is far more advantageous economically as compared to a thermal pre-treatment. Additionally, the presence of graphite in the black mass was found to be extremely important for the propagation of the effect of plasma. The same plasma treatment on bare NMC811 wasPATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT not effective in disrupting the NMC lattice completely, as evident from PXRD patterns.

[0112] 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

PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCTCLAIMSWhat is claimed:

1. A method for recycling waste comprising: exposing the waste to a plasma to obtain a plasma-exposed waste; and leaching a metal in an acid from the plasma-exposed waste to obtain a treated waste.

2. The method of claim 1, wherein the waste comprises a feedstock selected from the group consisting of black mass from lithium ion batteries, black mass from sodium ion batteries, cables, wires, fly ash, coal ash, coal char, electronic wastes, renewable energy wastes, mined ores, mined tailings, and combinations thereof.

3. The method of claim 1, further comprising recovering graphite from the treated waste, wherein the waste comprises graphite from a spent battery and the treated waste comprises recovered graphite.

4. The method of claim 2, wherein the recovered graphite has reduced lattice spacing compared to the graphite from the spent battery.

5. The method of claim 2, wherein the recovered graphite has lower defects compared to the graphite from the spent battery.

6. The method of claim 2, further comprising reusing the recovered graphite in a device selected from the group consisting of energy storage devices, supercapacitors, and combinations thereof.

7. The method of claim 1, wherein the method further comprises preferentially leaching lithium before the leaching the metal in the acid.

8. The method of claim 5, wherein the preferentially leaching lithium comprises soaking or stirring the plasma-exposed waste in water at a temperature of less than 30 °C, thereby leaching lithium into a water leachate.

9. The method of claim 5, wherein the first leachate comprises less than 20% of nonlithium metals.PATENT APPLICATIONATTORNEY DOCKET NO. 17500-280W01CLIENT REF. NO. 2025-030-PCT10. The method of claim 5, wherein the first leachate comprises at least 80% of the lithium originally contained in the waste.

11. The method of claim 1, wherein the metal is selected from the group consisting of Co, Ni, Mn, Al , Cu and combinations thereof.

12. The method of claim 1, wherein the metal is selected from the group consisting of Co, Ni, Mn, Al , Cu and combinations thereof.

13. The method of claim 1, wherein the leaching the metal in the acid comprises soaking or stirring the treated waste in an organic acid, thereby leaching the metal into an acid leachate.

14. The method of claim 9, wherein the organic acid is selected from the group consisting of citric acid, lactic acid, acetic acid, ascorbic acid, glycolic acid, malonic acid, formic acid, oxalic acid, uric acid, malic acid, tartaric acid, butyric acid, folic acid and combinations thereof.

15. The method of claim 9, where the organic acid is present in a concentration ranging from 0.1 M to 2.0 M.

16. The method of claim 9, wherein the acid leachate comprises at least 80% of the metal originally contained in the waste.

17. The method of claim 1, wherein the plasma comprises a gas selected from the group consisting of Ar, NH3, O2, CO2, N2, CH4 and H2.

18. The method of claim 1, wherein the exposing the waste to a plasma comprises an exposure time ranging from 2 to 60 minutes.

19. A composition comprising the recovered graphite made by the method of any one of claims 2-4.

20. An apparatus comprising the device made by the method of claim 5.

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