Description:FIELD OF THE INVENTION
[0001] The present disclosure relates to a process for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries. The present disclosure also relates to a system for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries. The spent Lithium ion batteries have 15 wt% to 20 wt% graphite and it is necessary to reuse spent graphite to full fill the future demand of battery grade graphite.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] The drawbacks of the prior art documents includes that most of battery grade graphite is coming from mines which create high water pollution, land fill contamination and require high energy in purification process. No report for the regeneration of graphite from spent Li-ion battery with modified and enhanced electrochemical properties. Reported process are using strong acids like sulfuric acid, hydrochloric acid, nitric acid, acetic acid, formic acid and combinations of thereof for leaching which left around 1-2 wt% metallic impurities in graphite, which turns this graphite in non-ideal for new LIBs. Strong and higher amount of acids are required to leach the metallic impurities from the layered structure of graphite. The major disadvantages of this type of technology are its secondary pollution due to the pretreatment and the excessive amount of acid/alkaline, making the overall cost not economical.
[0004] Due to increasing land fill contamination, carbon emission, greenhouse gases, and price of fossil fuels, electro mobility is being considered a viable option in the form of electric vehicles (EVs). Hence, the graphite demand is increasing day by day and most of this graphite is coming from mines. Mining require a lot of energy and water to produce the battery grade graphite. This water pollution, energy consumption, and landfill contamination can be reduced with the recycling of spent NMC/LCO/LMO/LFP batteries. Recently, around 5% of spent NMC/LCO/LMO//LFP batteries are being recycled, with focus on metal oxides recovery while graphite is still being considered as a secondary product. Hence, to full fill the current demand and to reduce the carbon foot print and land fill contamination, regeneration of spent graphite from spent LIBs can play a crucial role in circular battery materials economy.
[0005] Both pyro-metallurgical and hydrometallurgical processes are being used for the recovery of valuable metal from NMC/LCO/LMO/LFP batteries. Graphite is being considered as by-product at best.
[0006] On the other hand, LIBs requires high purity graphite as anode due to its stable chemistry and electrochemical performance, and the price of battery grade graphite is between $8000--10,000/MT. Thus, the regeneration of graphite from spent LIBs becomes very an important and urgent need of fulfill the future energy demand. As mentioned above, in case of pyro-metallurgical processes, high temperature heating of material is required while in hydrometallurgical is low temperature processes with high production yield in presence of some acids like H2SO4, HCl, HNO3 and H3PO4. Most critical problem in graphite regeneration from spent NMC/LCO/LMO/LFP batteries, is its surface morphology, removal of minor metallic trace, and soft carbon coating.

OBJECTS OF THE INVENTION
[0007] An objective of the present invention is to provide a process for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries.
[0008] Another objective of the present invention is to provide a system for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries.
[0009] Another objective of the present invention is to provide a safe and scalable process by using pre-defined concentration of inorganic acid.
[0010] Another objective of the present invention is to provide a process to modify the surface morphology of graphite by using pre-defined alkali medium.
[0011] Another objective of the present invention is to provide a process for re-circulation of bi-products and reactor designs.
[0012] Yet another objective of the present invention is to produce comparable electrochemical performance as compared to commercially available graphite.

SUMMARY OF THE INVENTION
[0013] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0014] An aspect of the present disclosure relates to a process for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries comprising: a) mixing of NMC/LCO/LMO/LFP batteries black mass, a first acid by applying current and potential in designed Electro-chemical leaching reactor to obtain a Stage I graphite mixture; b) mixing of the Stage I graphite mixture, a second acid under condition to obtain a Stage II graphite mixture; c) washing the Stage II graphite mixture with an alkaline solution under condition to obtain a Stage III graphite mixture; d) filtering the Stage III graphite mixture to obtain a filtered Stage III graphite mixture and the alkali solution; and e) heating the filtered Stage III graphite mixture with a carbon source under condition to obtain a battery grade graphite.
[0015] Another aspect of the present disclosure relates to a system for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries comprising: a leaching unit is configured to receive a feedstock from NMC/LCO/LMO/LFP batteries black mass, wherein the feedstock is pre-mixed in the electro-chemical leaching (ECL) unit; an ECL unit is configured to receive the spent NMC/LCO/LMO/LFP batteries black mass from black mass reactor, a first acid from acid reactor, wherein the ECL unit is configured to pre-mix the spent batteries black mass, the first acid, by applying current and potential to obtain a Stage I graphite mixture in Stage I filtration unit; a second leaching unit is configured to receive the Stage I graphite mixture from Stage I filtration unit, a second acid from acid reactor, followed by mixing of the Stage I graphite mixture, the second acid to obtain a Stage II graphite mixture; a first filtration unit is configured for filtration to obtain the Stage II graphite mixture which is carried forward in a receiving reactor and the second acid in the filtrate, wherein the second acid is re-circulating to the acid reactor; a washing unit is configured to receive the Stage II graphite mixture from the receiving reactor and an alkali solution from alkali solution reactor followed by mixing the Stage II graphite mixture and the alkali solution in the washing unit and to obtain a Stage III graphite mixture; a second filtration unit is configured to filtrate the Stage III graphite mixture from the washing unit to obtain a filtered Stage III graphite mixture and the alkali solution in the filtrate, wherein the filtered Stage III graphite mixture is carried forward in the surface modified graphite reactor and the alkali solution is re-circulating to the alkali solution reactor; and a calcination unit is configured to receive the filtered Stage III graphite mixture from the surface modified graphite reactor and a carbon source from carbon source reactor followed by heating to obtain a battery grade graphite in a battery grade graphite reactor.
[0016] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0018] FIG. 1 illustrates a flow chart of the process for the regeneration of battery grade graphite from spent Lithium ion batteries.
[0019] FIG. 2 illustrates a flow chart of the system for the regeneration of battery grade graphite from spent Lithium ion batteries.

DETAILED DESCRIPTION OF THE INVENTION
[0020] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0021] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0022] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0023] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0024] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it is individually recited herein.
[0025] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0026] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0027] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0028] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0029] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description that follows, and the embodiments described herein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0030] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0031] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0032] Regeneration of graphite from NMC/LCO/LMO/LFP batteries is being avoided due to rigorous regeneration process, low cost compare to other valuables metals like Nickel, Manganese, Cobalt and Lithium. While the spent LIBs have 15 wt% to 20 wt% graphite, thus it is necessary to reuse spent graphite to full fill the future demand of battery grade material. In the present disclosure, more than 95% graphite can be regenerated with purity assay above 99.70%.
[0033] An aspect of the present disclosure provides a process for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries comprising: a) mixing of NMC/LCO/LMO/LFP batteries black mass, a first acid by applying current and potential in designed Electro-chemical leaching reactor to obtain a Stage I graphite mixture; b) mixing of the Stage I graphite mixture, a second acid under condition to obtain a Stage II graphite mixture; c) washing the Stage II graphite mixture with an alkaline solution under condition to obtain a Stage III graphite mixture; d) filtering the Stage III graphite mixture to obtain a filtered Stage III graphite mixture and the alkali solution; and e) heating the filtered Stage III graphite mixture with a carbon source under condition to obtain a battery grade graphite. A flow chart of the process is shown in FIG. 1.
[0034] In an embodiment, the first acid and the second acid are selected from a group consisting of sulphuric acid, nitric acid, phosphoric acid, hydrochloric acid, acetic acid, formic acid and combination thereof. Preferably, the first acid is sulfuric acid, phosphoric acid, hydrochloric and combination thereof. Preferably, the second acid is combination of more than two acids of sulphuric acid, nitric acid, phosphoric acid, hydrochloric acid, acetic acid, formic acid. The first acid has a concentration in the range of 0.1 to 2 M. Preferably, the first acid has a concentration of 1 to 2 M. The second acid has a concentration in the range of 0.1 to 2 M. Preferably, the second acid has a concentration of 0.5 to 1 M. In an embodiment, the first acid and the second acid are different combinations with different ratio.
[0035] In an embodiment, the conditions of the process are: i) step a) includes temperature in the range of 30 to 90 °C, preferably at a temperature in the range of 60 to 90 °C for a period in the range of 2 to 10 hrs, preferably for 3 to 10 hrs with a pressure in the range of 0.5 to 1.5 bar, preferably at a pressure of 1 bar, ii) step b) includes temperature in the range of 30 to 90 °C, preferably at a temperature in the range of 60 to 90 °C for a period in the range of 2 to 10 hrs, preferably for 5 to 10 hrs with a pressure in the range of 0.5 to 1.5 bar, preferably at a pressure of 1 bar, iii) step c) includes temperature in the range of 30 to 100 °C, preferably at a temperature in the range of 50 to 100 °C, for a period in the range of 1 to 5 hrs, preferably for 3 hrs with a pressure in the range of 0.5 to 1.5 bar, preferably at a pressure of 1 bar, and pH in the range of 9 to 14, preferably pH in the range of 10 to 14, and iv) step e) includes temperature in the range of 500 to 900 °C, preferably at a temperature in the range of 750 to 900 °C for a period in the range of 2 to 10 hrs, preferably for 2 to 10 hrs, in controlled environment, preferably argon, nitrogen, CO2 and combination thereof.
[0036] In an embodiment, the acid obtained after filtration in step b) is re-circulated in the process.
[0037] In an embodiment, the alkali solution is step c) is selected from NaOH, KOH, NH4OH and combination thereof.
[0038] In an embodiment, alkali solution obtained after filtration in step d) is re-circulated in the process.
[0039] In an embodiment, the carbon source is selected from a group consisting of organic acid, resins, natural carbon, coal-tar, pitch with low softening points and combination thereof. Preferably, the carbon source is coal tar, pitch and combination thereof.
[0040] In an embodiment, the Stage I graphite mixture has impurities less than 2%, the Stage II graphite mixture has impurities less than 1% and the Stage III graphite mixture has impurities less than 0.3%.
[0041] In an embodiment, the sulfur and sodium, chlorine impurities reduced less than <0.1%.
[0042] In an embodiment of the present disclosure, the NMC/LCO/LMO/LFP batteries black mass and 1M sulfuric acid were mixed by applying current and potential in an Electro-chemical leaching reactor at a temperature of 75°C for a period of 5 hrs with a pressure of 1 bar to obtain a Stage I graphite mixture which had impurities less than 2%. The Stage I graphite mixture was mixed with 1M of sulphuric acid and 1 M of nitric acid at a temperature of 75 °C for a period of 7 hrs to obtain a Stage II graphite mixture which had impurities less than 1%. The sulphuric acid and nitric acid were obtained after filtration, were re-circulated back to the acid reactor for reuse. The Stage II graphite mixture was contacted with NaOH solution at a temperature of 75°C for a period of 3 hrs at a pressure of 1 bar and to maintain a pH of 10 to obtain a Stage III graphite mixture which was filtered to obtain a filtered Stage III graphite mixture and the NaOH solution. The obtained NaOH solution was re-circulated back to the alkali solution reactor for reuse. The Stage III graphite mixture had impurities less than 0.3%. The filtered Stage III graphite mixture was heated with a coal-tar at a temperature of 750 °C for a period of 6 hrs to obtain battery grade graphite. It has been observed from the above process that the obtained battery grade graphite has higher purity and higher yield.
[0043] Another aspect of the present disclosure provides system 200 for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries comprising: a leaching unit 201 is configured to receive a feedstock from NMC/LCO/LMO/LFP batteries black mass, wherein the feedstock is pre-mixed in the electro-chemical leaching (ECL) unit 201-A; an ECL unit 201-A is configured to receive the spent NMC/LCO/LMO/LFP batteries black mass from black mass reactor 201-B, a first acid from acid reactor 201-C, wherein the ECL unit 201-A is configured to pre-mix the spent batteries black mass, the first acid, by applying current and potential to obtain a Stage I graphite mixture in Stage I filtration unit 201-D; a second leaching unit 201-E is configured to receive the Stage I graphite mixture from Stage I filtration unit 201-D, a second acid from acid reactor 201-C, followed by mixing of the Stage I graphite mixture, the second acid to obtain a Stage II graphite mixture; a first filtration unit 201-F is configured for filtration to obtain the Stage II graphite mixture which is carried forward in a receiving reactor 202-A and the second acid in the filtrate, wherein the second acid is re-circulating to the acid reactor 201-C; a washing unit 202-B is configured to receive the Stage II graphite mixture from the receiving reactor 202-A and an alkali solution from alkali solution reactor 202-C followed by mixing the Stage II graphite mixture and the alkali solution in the washing unit 202-B and to obtain a Stage III graphite mixture; a second filtration unit 202-D is configured to filtrate the Stage III graphite mixture from the washing unit 202-B to obtain a filtered Stage III graphite mixture and the alkali solution in the filtrate, wherein the filtered Stage III graphite mixture is carried forward in the surface modified graphite reactor 203-A and the alkali solution is re-circulating to the alkali solution reactor 202-C; and a calcination unit 203-C is configured to receive the filtered Stage III graphite mixture from the surface modified graphite reactor 203-A and a carbon source from carbon source reactor 203-B followed by heating to obtain a battery grade graphite in a battery grade graphite reactor 203-D. The system is shown in FIG. 2.
[0044] In an embodiment, the calcination step has developed about 25-50 nanometer thick carbon coating layer.

EXAMPLES
[0045] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Example 1
[0046] Stage I graphite was recovered from NMC/LCO/LMO/LFP batteries black mass after electrochemical leaching at pre-defined current and voltage range. A system 200 for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries. A leaching unit 201-A was configured to recover stage-I graphite, at pre-defined current and voltage to receive a feedstock from NMC/LCO/LMO/LFP batteries black mass 400-500 Kg and acid 4-6 KL of pre-defined concentration, from unit 201-B and 201-C respectively and around 97-125 kg stage I graphite was recovered at 201-D. Unit 201-E was configured at pre-defined current and voltage to receive the stage-I graphite 97-125 kg and acid 1-1.5 KL of pre-defined concentration from 201-D and 201-C respectively and acid was re-circulating to unit 201-C from 201-F. Unit 202-B was configured recover stage-III graphite to mix the Stage II graphite 95-120 kg and alkaline solution 0.6KL – 1KL from unit 202-A and 202-C respectively. Alkaline solution was re-circulating to unit 202-C from 202-D filtration unit and around 90-115 Kg graphite was recovered. Unit 203-A was configured to mix the carbon source from and stage-III graphite unit 203-B and 202-D respectively. Unit 203-C received the mixture of stage-III graphite and carbon source for calcination from 203-A. Battery grade, graphite was finally recovered in from solid powder around 90-115 kg. The reaction parameters, recovery and purity of Stage I graphite, Stage II graphite and Stage III graphite are given in below Table 1:

Table 1: Reaction parameters, recovery and purity of Stage I graphite to Stage III graphite.
Leaching Parameter
Reaction parameters-Stage I graphite
Solid to Liquid (S/L) (%) Acid conc. (Molar) Temp (°C) Time (hr) Recovery (%) Purity (%)
7.5 1 60-90 3-6 85-90 95-97
10 1 60-90 3-6 93-95 95-98
12.5 1 60-90 3-6 90-95 95-97
15 1 60-90 3-6 80-90 90-95
20 1 60-90 3-6 75-85 90-93
10 1.5 80-90 6-10 80-94 95-98
10 2 80-90 6-10 80-92 90-96
12.5 1.5 80-90 6-10 80-92 90-95
15 1.5 80-90 6-10 90-94 90-94
Reaction parameters-Stage II Graphite
Solid to Liquid (S/L) (%) Acid conc. (Molar) Temp (°C) Time (hrs) Recovery (%) Purity (%)
7.5 0.75 70-90 3-10 85-90 95-97
10 0.5 60-90 5-10 90-95 98-99.2
10 1 80-90 3-10 85-90 97-99
10 0.25 60-90 5-10 90-95 98-99
12.5 0.5 60-90 5-10 87-92.5 97-98.5
12.5 0.75 60-90 5-10 85-91 97-98.3
12.5 0.75 60-90 5-10 85-93 97-98
15 0.75 60-90 5-10 85-94 95-96
Alkaline Washing
Reaction parameters-Stage III Graphite
Solid to Liquid (S/L) (%) Base Base conc. (Molar) PH Range Temp. (Celsius) Time (hrs) Recovery (%) Purity (%)
10 NaOH 0.5 10-14 50-100 3-5 90-95 98-99.6
10 1 12-14 50-100 3-5 87-90 98-99
10 0.25 12-14 50-100 3-5 87-92 98-99.4
10 KOH 0.5 10-14 50-100 3-5 90-95 98-99.2
10 1 10-14 50-100 3-5 90-96 99-99.7
10 0.25 10-14 50-100 3-5 85-90 98-99.5
10 NH4OH 0.5 10-14 50-100 3-5 85-90 98.5-99.2
10 1 10-14 50-100 3-5 85-93 97-99
10 0.25 10-14 50-100 3-5 90-95 98-99

[0047] The stage I recovery is maximum 94% graphite with purity level 98% using solid to liquid ratio 1:10 during leaching in 1.5 M acid solution at temperature 80-90 °C for 6-10 hrs. The stage II recovery is maximum 95% graphite with purity level 99.2% using solid to liquid ratio 1:10 during leaching in 0.5 M acid solution at temperature 60-70 °C for 5-10 hrs. The stage III maximum recovery is range 95-96% graphite with purity level in range 99.5-99.7% using solid to liquid ratio 1:10 during alkaline washing (0.5 M ) solution, pH of medium is in range 10-14 at temperature 50-100 °C for 3-5 hrs.
[0048] Battery grade graphite anode was recovered by surface modification steps. Reversible specific capacity of graphite was obtained in range of 340-348 mAh/g using different carbon sources with maximum loading 2% and kept it at 450-900 °C for 5-10 hrs in inert atmosphere. The surface area of recovered graphite is in range 3-6.45 m2/g and crystallite size is in range 140-168 nm. Reaction parameters for Surface modification are shown in Table 2 below:

Table 2: Reaction parameters for Surface modification.
Surface Modification
Reaction parameters-High temperature Reaction
Carbon Source Loading % Temp
°C Time (hrs) Particle Size (D50, micron) Surface area (m2/g) Average Crystallite Size(nm) Reversible Specific capacity (mAh/g)
Organic acid 4 450 5-10 2.0 3.00 140 340.24
500 5-10 5.0 5.88 151 342.34
550 5-10 6.0 6.50 167 340.65
Coal-tar <2 750 5-10 3.0 3.74 139 345.23
850 5-10 4.5 4.34 151 347.65
900 5-10 5.0 6.54 167 348.32
Pitch A <2 750 5-10 2.5 4.57 140 345.65
850 5-10 3.7 6.12 150 346.76
900 5-10 4.2 6.45 168 347.41
Pitch B <2 750 5-10 3.2 4.05 142 346.78
850 5-10 4.2 5.32 151 347.54
900 5-10 5.5 5.85 171 349.45
Commercial Graphite sample 5-7 6-8 100-200 360-370

[0049] Graphite was recovered from different types of spent batteries received from different segment such as EV, consumer electronics and energy storage etc. The chemistry varies from NMC, LFP, LCO and LMO. The recovery percentage is in range 84-86%. Bulk processing of Graphite recycling are shown in Table 3 below:
Table 3: Bulk processing of Graphite recycling.
Batch Type of BM Batch size (kg) Graphite % in BM Graphite in BM (kgs) Stage I Recovery Stage II Recovery Stage III Recovery Process yield (%)
1 NMC 1 100 26% 26.0 24.4 23.2 22 85.7
2 NMC 2 200 27% 54.0 50.8 48.2 46 85.7
3 LFP 400 30% 120.0 112.8 107.2 104 86.6
4 LCO 500 24% 120.0 114.0 109.4 105 87.6
5 LMO 1000 28% 280.0 263.2 250.0 238 84.8
Average process yield (%) 86.1

[0050] ICP results of graphite recovered from NMC spent batteries are shown in Table 4. Metal impurities present in graphite at different stages (Stage I, Stage II & Stage III) were analyzed by ICP.

Table 4: ICP table for NMC/LCO/LMO BM processing.
Process NMC BM Stage I Graphite Stage II Graphite Stage III Graphite
Al (mg/kg) 2053.87 742.2 472.46 20.00
Co (mg/kg) 163490.06 2535.7 0.00 63.20
Cu (mg/kg) 403.80 0.0 0.00 0.00
Fe (mg/kg) 851.75 0.0 0.00 0.00
Li (mg/kg) 7250.44 0.0 0.00 0.00
Mn (mg/kg) 22747.64 0.0 0.00 0.00
Na (mg/kg) 208.09 0.0 0.00 250.00
Ni (mg/kg) 2257.77 0.0 0.00 0.00
P (mg/kg) 1000.00 200.0 100.00 10.00
S(mg/kg) 0.00 9800.0 1000.00 250.00
Si (mg/kg) 1000.00 2500.0 3000.00 15.00
Other possible impurities (mg/kg) 5000.00 1000.0 500.00 200.34
Purity (%) 79.37 98.32 99.49 99.92

[0051] Metal impurities present in graphite at different stages (Stage I, Stage II & Stage III) were analyzed by ICP. The purity of graphite recovered from LFP spent batteries is shown in Table 5.

Table 5: ICP table for LFP BM processing
Process LFP BM Stage I Graphite Stage II Graphite Stage III Graphite
Al (mg/Kg) 3033.7 854.0 301.0 35
Co (mg/Kg) 0 0.0 0.0 0
Cu (mg/Kg) 180.8 0.0 0.0 0
Fe (mg/Kg) 215268.9 3500.0 220.0 62
Li (mg/Kg) 5940.9 0.0 0.0 0
Mn (mg/Kg) 0 0.0 0.0 0
Na (mg/Kg) 0 0.0 0.0 0
Ni (mg/Kg) 0 0.0 0.0 0
P (mg/Kg) 136592.3 200.0 250.0 21
S(mg/Kg) 0 8800.0 1100.0 260
Si (mg/Kg) 798.3 500.0 700.0 17
Other possible impurities (mg/kg) 4500.00 900.0 600.00 180.34
Purity (%) 63.37 98.52 99.68 99.94

[0052] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

ADVANTAGES OF THE PRESENT INVENTION
[0053] The present disclosure discloses that a) this cutting edge technology is suitable for the production of battery grade graphite from spent Li-ion batteries, b) this technology used pre-defined concentration of inorganic acid which make the process safe and scalable, c) the process uses pre-defined alkaline medium which help to modify the surface morphology of graphite, d) the process uses pre-defined alkaline medium which also help to remove the trace impurities of aluminum, silicon, cobalt, nickel etc, e) the process uses pre-defined alkaline medium which also help to improve the crystallinity of acid treated graphite, f) no secondary pollution generation due to re-circulation of bi products and reactor designs, g) the present invention uses economically cheap and widely available carbon sources such citric acid, resins/coal tar pitch etc, h) electrochemical performance is comparable to commercially available graphite of same specifications.
[0054] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
Reference numeral:
System: 200
Leaching unit: 201
Electro-chemical leaching (ECL) unit: 201-A
Black mass reactor: 201-B
Acid reactor: 201-C
Stage I filtration unit: 201-D
Second leaching unit: 201-E
First filtration unit: 201-F
Washing chamber: 202
Receiving reactor: 202-A
Washing unit: 202-B
Alkali solution reactor: 202-C
Second filtration unit: 202-D
Surface modification chamber: 203
Surface modified graphite reactor: 203-A
Carbon source reactor: 203-B
Calcination unit: 203-C
Battery grade graphite reactor: 203-D
, Claims:1. A process for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries comprising:
a) mixing of NMC/LCO/LMO/LFP batteries black mass, a first acid by applying current and potential in designed Electro-chemical leaching reactor to obtain a Stage I graphite mixture;
b) mixing of the Stage I graphite mixture, a second acid under condition to obtain a Stage II graphite mixture;
c) washing the Stage II graphite mixture with an alkaline solution under condition to obtain a Stage III graphite mixture;
d) filtering the Stage III graphite mixture to obtain a filtered Stage III graphite mixture and the alkali solution; and
e) heating the filtered Stage III graphite mixture with a carbon source under condition to obtain a battery grade graphite.
2. The process as claimed in claim 1, wherein the first acid and the second acid are selected from a group consisting of sulphuric acid, nitric acid, phosphoric acid, hydrochloric acid and combination thereof.
3. The process as claimed in claim 1, wherein the first inorganic acid has a concentration in the range of 0.1 to 2 M.
4. The process as claimed in claim 1, wherein the first acid and the second acid are different.
5. The process as claimed in claim 1, wherein the conditions of the process are:
i) step a) includes temperature in the range of 30 to 90 °C for a period in the range of 2 to 10 hrs with a pressure in the range of 0.5 to 1.5 bar,
ii) step b) includes temperature in the range of 30 to 90 °C for a period in the range of 2 to 10 hrs with a pressure in the range of 0.5 to 1.5 bar,
iii) step c) includes temperature in the range of 30 to 100 °C for a period in the range of 1 to 5 hrs with a pressure in the range of 0.5 to 1.5 bar and pH in the range of 9 to 14, and
iv) step e) includes temperature in the range of 500 to 900 °C for a period in the range of 2 to 10 hrs.
6. The process as claimed in claim 1, wherein the acid obtained after filtration in step b) is re-circulated in the process.
7. The process as claimed in claim 1, wherein the alkali solution obtained after filtration in step d) is re-circulated in the process.
8. The process as claimed in claim 1, wherein the carbon source is selected from a group consisting of organic acid, resins, natural carbon, coal tar, pitch and combination thereof.
9. The process as claimed in claim 1, wherein the Stage I graphite mixture has impurities less than 2%, the Stage II graphite mixture has impurities less than 1% and the Stage III graphite mixture has impurities less than 0.3%.
10. A system (200) for regeneration of battery grade graphite from spent NMC/LCO/LMO/LFP batteries comprising:
a leaching unit (201) is configured to receive a feedstock from NMC/LCO/LMO/LFP batteries black mass, wherein the feedstock is pre-mixed in the electro-chemical leaching (ECL) unit (201-A);
an ECL unit (201-A) is configured to receive the spent NMC/LCO/LMO/LFP batteries black mass from black mass reactor (201-B), a first acid from acid reactor (201-C), wherein the ECL unit (201-A) is configured to pre-mix the spent batteries black mass, the first acid, by applying current and potential to obtain a Stage I graphite mixture in Stage I filtration unit (201-D);
a second leaching unit (201-E) is configured to receive the Stage I graphite mixture from Stage I filtration unit (201-D), a second acid from acid reactor (201-C), followed by mixing of the Stage I graphite mixture, the second acid to obtain a Stage II graphite mixture;
a first filtration unit (201-F) is configured for filtration to obtain the Stage II graphite mixture which is carried forward in a receiving reactor (202-A) and the second acid in the filtrate, wherein the second acid is re-circulating to the acid reactor (201-C);
a washing unit (202-B) is configured to receive the Stage II graphite mixture from the receiving reactor (202-A) and an alkali solution from alkali solution reactor (202-C) followed by mixing the Stage II graphite mixture and the alkali solution in the washing unit (202-B) and to obtain a Stage III graphite mixture;
a second filtration unit (202-D) is configured to filtrate the Stage III graphite mixture from the washing unit (202-B) to obtain a filtered Stage III graphite mixture and the alkali solution in the filtrate, wherein the filtered Stage III graphite mixture is carried forward in the surface modified graphite reactor (203-A) and the alkali solution is re-circulating to the alkali solution reactor (202-C); and
a calcination unit (203-C) is configured to receive the filtered Stage III graphite mixture from the surface modified graphite reactor (203-A) and a carbon source from carbon source reactor (203-B) followed by heating to obtain a battery grade graphite in a battery grade graphite reactor (203-D).
11. The system (200) as claimed in claim 10, wherein the calcination step has developed about 2.5 micron thick carbon coating layer.