DESC:FORM 2

THE PATENTS ACT, 1970

(39 of 1970)

&

THE PATENT RULES, 2003

COMPLETE SPECIFICATION

[See Section 10 and Rule 13]

TITLE:

“A METHOD FOR RECOVERING HIGH PURE GRAPHITE FROM WASTE LITHIUM-ION BATTERIES”

APPLICANT:

ATTERO RECYCLING PVT. LTD.
A company incorporated under the Indian Companies Act, 1956
having address at
173, Raipur Industrial Area, Bhagwanpur, Roorkee,
Haridwar Uttarakhand - 247661, India

PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to a method for recovering high pure graphite from spent lithium-ion batteries. More particularly, the present invention relates to the recycling of waste lithium-ion batteries that have been discarded and are used for recovering/producing high pure graphite.

BACKGROUND OF THE INVENTION
Lithium-ion battery is a type of rechargeable battery that comprises of the cells in which lithium ions move from negative electrode to positive electrode through an electrolyte. The positive electrode consists of an intercalated lithium compound material while the negative electrode consists of graphite material. Lithium-ion battery nowadays, is getting used in many products including electronic items, electric vehicles, small and large appliances, etc. The lithium-ion batteries that are used in these products gets charged easily and many times without any problem and is time efficient. The lithium-ion battery provides the advantage of extending lifetime, increasing energy density, improving safety, cost reduction and enhanced charging speed.
Lithium-ion battery is the most productive and safest battery to be used as compared to the other batteries, which are costly, and does not have the same energy efficiency as of lithium-ion battery. However, there are certain limitations of lithium-ion battery as they cause harm to the environment as it produces gas and heat on excessive usage, due to which the battery gets swelled up. The gas produced by the lithium-ion battery causes environmental pollution in large amount. Besides the advantages and disadvantages of utilizing lithium-ion battery, the recycling of waste lithium-ion battery for the process of recovering or producing high pure graphite is still remaining and is not explored commonly and evenly on a large scale.
Conventionally, the recycling/recovering of graphite from waste/spent lithium-ion batteries is achieved by several methods including thermal treatment of graphite without electrolyte recovery, while the another method includes utilization of a sub-critical carbon dioxide-assisted electrolyte extraction prior to thermal treatment. But these conventional methods of recycling/recovering graphite i.e., thermal treatment process for recovering graphite from spent lithium-ion batteries is not sustainable due to its energy-intensive nature and potential to damage soil properties. The thermal treatment process uses high temperature for the processing of waste materials that is mainly used for the waste treatment technology.
The method of recycling waste lithium-ion battery in order to produce graphite has been taken into account by many prior arts. Some of them includes:
WO2022006469A1 discloses about the method of reductive-acid leaching of spent battery electrodes to recover valuable materials. The process involves reductive-acid leaching with sulfur dioxide and sulfuric acid of the material in a single or a multi-step followed by practiced hydrometallurgical methods. This reductive-acid leaching process results in a lithium brine as a product. The resulting liquor from the lithium brine product is subjected to the precipitation and oxidation steps in order to remove other compounds such as lithium, cobalt and nickel which are then separated by the process of electrowinning from the resultant product i.e., lithium brine. The metallic components like Cu in the source material may not leach completely in reductive-acid leaching and needs an oxidizing environment.
WO2021018788A1 discloses about the process for the recovery of lithium and other metals from waste lithium-ion batteries. In this process, lithium is selectively leached out using an alkaline medium whereas, the Co/Ni is recovered as an alloy through pyro-metallurgical technique. The process specifically involves separating lithium from undesired impurities by extracting lithium as lithium hydroxide from the particulate material that is obtained from the lithium-ion batteries by shredding, discharging and reducing at elevated temperatures. The recovery of other metals such as nickel, manganese, and cobalt is achieved by smelting process.
EP3535803B1 discloses about the process, apparatus and system for recovering materials i.e., lithium and other metals from waste lithium-ion battery. The method describes the complete recycling of spent lithium-ion battery through mechanical and chemical process. However, the purity of each product separated from spent lithium ion batteries is not defined.
CN112779421A discloses about the method for recycling anode material of waste lithium-ion battery which describes that the anode material is pre-treated in the first step followed by smelting at 1400-1600ºC in order to recover metal alloy and slag. While, in the later stage, it has been disclosed that lithium is recovered from the slag with HCl and alkali reagent. During smelting of the electrode material at 1400-1600°C, lithium sublimates hence cannot be recovered.
WO2021018778A1 discloses about the process for recovery of lithium from waste lithium-ion batteries. The method is focused on the recovery of lithium only through hydrometallurgical technique. The method includes a particulate material such as Mn, Ni, Co, etc. which are treated with a polar solvent and an alkaline earth hydroxide. Then the solids are separated from the liquid by washing the solid residue with the polar solvent such as water that separates lithium in high purity and recovers valuable transition metals.
Yue Yang et al. Waste Management 85 (2019) 529–537 (10.1016/j.wasman.2019.01.008) in their review article describes about the complete recycling of different components of spent lithium-ion batteries through combined hydro-pyro techniques. By the following techniques, copper and lithium can be recovered and graphite can be regenerated, thereby serving as a sustainable approach for the utilization of anode material from spent lithium-ion battery. The process uses HCl for the purification of graphite whereas, the metallic copper and aluminium may not be completely removed from the impure graphite.
In the past, few other such methods were also there, however, these methods make the environment unhealthy as for the reductive-acid leaching process, oxidizing environment is needed. The pyrometallurgical technique used for recovery of metals is energy-intensive and needs further separation steps to recover metals. Further, the harsh acids used for graphite recovery may not recover the metals included in the subject matter completely.
Therefore, there exists a need to develop a method that recovers graphite with high purity even at moderate temperatures. In light of the above, there exists a need to explore new approaches for recovering these products that makes the work place safe and healthy. The present invention is an endeavor in this direction.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a method of recovering highly pure graphite.
Another object of the present invention is to provide a method of recovering highly pure graphite from waste/spent lithium-ion batteries.
Yet another object of the present invention is to provide a method of recovering highly pure and battery grade graphite from waste/spent lithium-ion batteries.
Yet another object of the present invention is to provide a commercially feasible method of recovering highly pure graphite from waste/spent lithium-ion batteries.
Still another object of the present invention is to provide a method which is clean, green and environment friendly.

SUMMARY OF THE INVENTION
The present invention relates to recycling of waste/spent lithium-ion batteries that have been discarded in order to produce highly pure and battery grade graphite.
In an embodiment, the present invention provides a method for recovering highly pure graphite from waste lithium-ion batteries, comprising the steps of: a) leaching of an anode material (impure graphite obtained from spent lithium-ion battery) of the waste lithium-ion battery for 2-3 hours to remove metal values other than aluminum to obtain a filtrate and residue of leach liquor, b) leaching the traces of the aluminum from the residue of leach liquor obtained in step (a) for 2-3 hours to obtain a cake, c) washing and drying the cake obtained in step (b) with water at a predetermined temperature for 2-3 hour to obtain highly pure graphite, d) recycling the leach liquor obtained in step (a) multiple times to concentrate the leach liquor and to get enriched metal ions in the liquor, and e) precipitating the metal ions obtained from the enriched liquor in step (d) followed by washing of the cake for recovery of highly pure and battery grade graphite with percentage purity in range of 98-99%.
Further, re-dissoluting the washed cake obtained in step (e) with sulphuric acid followed by recovery of dissolved metal ions. The wash liquor containing the traces of aluminum to effluent treatment plant are sent for safe disposal.
The highly pure and battery grade graphite is recovered in a commercially feasible method from waste lithium-ion batteries and the method of recovery of graphite is a two-stage leaching process for the recovery of highly pure graphite from waste lithium-ion batteries. The dissolved metal ions include but are not limited to copper (Cu), cobalt (Co), nickel (Ni), lithium (Li) and manganese (Mn) which are recovered by the two-stage leaching process.
The present invention relates to method of recovery of the graphite and said method is clean, green and environment-friendly.

BRIEF DESCRIPTION OF THE DRAWING
An understanding of the method of recovering graphite from waste lithium-ion batteries of the present invention may be obtained by reference to the following drawings:
Figure 1 illustrates the process flow for the production of high pure graphite from spent lithium-ion battery according to an embodiment of the present invention.
Figure 2 shows the SEM picture (left) and EDX (right) of the product indicating the formation of layered spherical graphite (size of 50 nm) mounting on the wall and the purity, respectively according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.
The present invention relates to the method for recovery of highly pure graphite from waste/spent lithium-ion batteries by recycling lithium-ion battery anode.
In a preferred embodiment, the present invention provides a method for recovering highly pure graphite from waste lithium-ion batteries, comprising the steps of: a) leaching the anode material (impure graphite obtained from spent lithium-ion battery) of the waste lithium-ion battery for 2-3 hours to remove metal values other than aluminum to obtain residue of leach liquor; b) leaching of traces of the aluminum from the residue of the leach liquor obtained in step (a) for 2-3 hours to obtain a cake; c) washing and drying of the cake obtained in step (b) at a predetermined temperature for 2-3 hours to obtain highly pure graphite; d) recycling the leach liquor obtained in step (a) multiple times to concentrate the leach liquor and to get enriched metal ions in the liquor; and e) precipitating the metal ions obtained from the enriched liquor in step (d) followed by washing of the cake for recovery of highly pure and battery grade graphite with percentage purity in a range of 98-99%.
Further, re-dissoluting the washed cake obtained in step (e) with sulphuric acid followed by recovery of dissolved metal ions. The wash liquor containing the traces of aluminum to effluent treatment plant are sent for safe disposal.
Here, the leaching of step (a) is carried out with nitric acid (30% w/v) at pulp density (30% w/v) to remove metal values other than aluminium and the metal values of step (a) other than aluminium are copper (Cu), cobalt (Co), nickel (Ni), lithium (Li), and manganese (Mn). The leaching of step (b) is carried out with sulphuric acid (15% w/v) and hydrogen peroxide (10% w/v) at pulp density (30% w/v) to obtain a cake.
The predetermined temperature of step (c) is 85-90°C and the metal ions are precipitated by using soda solution (25% w/v) at a pH in a range of 10-10.5.
The method recovers highly pure and battery grade graphite in a commercially feasible method from waste lithium-ion batteries; and the method is a two-stage leaching process for the recovery of highly pure graphite from waste lithium-ion batteries.
The dissolved metal ions of step (f) includes copper (Cu), cobalt (Co), nickel (Ni), lithium (Li) and manganese (Mn) which are recovered by the two-stage leaching process. Further, the method is clean, green and environment-friendly method.
Figure 1 shows the process flow for the production of high pure graphite from spent lithium-ion battery.
EXAMPLE 1
Leaching Test
Leached residue, hereinafter impure graphite1 containing (3.2% Cu, 2.1% Al, 20 0.05% Co, 0.04% Ni, 0.003% Li, 0.02% Mn, and 1.6% Fe) was leached in the nitric acid solution for 2-3 hours in a closed reactor at 300-400 rpm. The leaching behavior was tested for three different weights of raw material while maintaining the pulp density constant at 30%. The experimental results are shown in Table 1.
Table 1: Leaching behavior of impure graphite1 in nitric acid solution
Impure graphite1
wt., g Conc. HNO3, mL Pulp density, wt./vol.% Leach liquor volume, mL Metals in leach liquor, g/L
Cu Fe Al Co Ni Mn Li
100 30 30 400 8.1 3.51 0.52 0.12 0.10 0.05 0 .07
Leaching efficiency %
Cu Fe Al Co Ni Mn Li
99.9 87.5 9.5 99.6 99.7 99.8 99.6
Impure graphite1
wt., g Conc. HNO3, mL Pulp density, wt./vol.% Leach liquor volume, mL Metals in leach liquor, g/L
Cu Fe Al Co Ni Mn Li
500 150 30 2010 7.91 3.50 0.99 0.12 .09 .049 .069
Leaching efficiency %
Cu Fe Al Co Ni Mn Li
99.3 88.0 10.0 99.6 99.7 99.6 99.7
Impure graphite1
wt., g Conc. HNO3, mL Pulp density, wt./vol.% Leach liquor volume, mL Metals in leach liquor, g/L
Cu Fe Al Co Ni Mn Li
1000 300 30 4130 7.70 3.29 .50 .11 .09 .04 .07
Leaching efficiency %
Cu Fe Al Co Ni Mn Li
99.4 85.0 10.0 99.5 99.4 99.5 99.7
Leach liquor = leached solution + washing volume
EXAMPLE 2
Leaching behavior of impure graphite2
The un-leached aluminum and iron in the leached residue (impure graphite2) obtained after nitric acid treatment was further treated in sulphuric acid and an oxidising agent specifically hydrogen peroxide solution for 2-3 hours in a closed reactor at 300-400 rpm. The leaching behavior was tested for three different weights of raw material while maintaining the pulp density constant at 30%. The experimental results are shown in Table 2.
Table 2: Leaching behavior of impure graphite2 in H2SO4 acid and H2O2 reagent solutions
Impure graphite2
wt., g Conc. H2SO4, mL Conc.
H2O2, mL Pulp density, wt./vol.% Leach liquor volume, mL Metals in leach liquor, g/L
Cu Fe Al Co Ni Mn Li
93 15 10 30 450 BDL 0.45 3.73 BDL BDL BDL BDL
Leaching efficiency %
Cu Fe Al Co Ni Mn Li
NA 99.9 93.15 NA NA NA NA
Impure graphite2
wt., g Conc. H2SO4, mL Conc.
H2O2, mL Pulp density, wt./vol.% Leach liquor volume, mL Metals in leach liquor, g/L
Cu Fe Al Co Ni Mn Li
474.5 75 50 30 2570 NA 0.23 3.37 NA NA NA NA
Leaching efficiency %
Cu Fe Al Co Ni Mn Li
NA 99.9 93.1 NA NA NA NA
Impure graphite2
wt., g Conc. H2SO4, mL Conc.
H2O2, mL Pulp density, wt./vol.% Leach liquor volume, mL Metals in leach liquor, g/L
Cu Fe Al Co Ni Mn Li
929.6 150 100 30 4725 BDL 0.50 3.72 BDL, BDL, BDL, BDL
Leaching efficiency %
Cu Fe Al Co Ni Mn Li
NA 99.9 92.7 NA NA NA NA
Leach liquor = leached solution + washing volume
The treated graphite in the slurry was filtered, washed and dried at 85-90ºC for 2-3 hours and finally analyzed. The chemical analysis as well as the characterization of the dried sample is done and the chemical analysis of obtained graphite is presented in Table 3 and Figure 2.
Figure 2 shows the SEM picture (left) and EDX (right) of the product indicating the formation of layered spherical graphite (size of 50 nm) mounting on the wall and the purity, respectively.
Table 3
Chemical analysis of obtained graphite powder
Sample No. Elements, %
Fe Cu Ni Co Mn Li Al Purity
1. BDL BDL BDL BDL BDL BDL 0.13 99.87
2. BDL BDL BDL BDL BDL BDL 0.14 99.86
3. BDL BDL BDL BDL BDL BDL 0.11 99.89
BDL: Below detection limit
EXAMPLE 3
Precipitation Test
Bulk precipitation of the leach liquor obtained from the nitric acid leaching of the impure graphite1 was carried out by adding an exact stoichiometric amount of a precipitating reagent specifically soda. The precipitation was performed under a specific condition closed reactor at 200-350 rpm. The precipitation behavior was tasted with three different volumes of the obtained leach liquor. The experimental results are shown in Table 4.

Table 4: Precipitation behavior of leach liquor with soda
L.L, Vol.
mL pH Filtrate vol.
mL Metals in the filtrate, g/L
Cu Fe Al Co Ni Mn Li
1000 10.4 900 0.01 0.03 0.05 0.01 BDL BDL 0.01
Precipitation efficiency %
Cu Fe Al Co Ni Mn Li
99.9 99.9 99.9 99.9 NA NA 99.9,
L.L, Vol.
mL pH Filtrate vol.
mL Metals infiltrate, g/L
Cu Fe Al Co Ni Mn Li
2000 10.5 1880 0.01 0.02 0.04 0.01 BDL BDL 0.01
Precipitation efficiency %
Cu Fe Al Co Ni Mn Li
99.9 99.9 99.9 99.9 NA NA 99.9
L.L, Vol.
mL pH Filtrate vol.
mL Metals infiltrate, g/L
Cu Fe Al Co Ni Mn Li
3000 10.4 2850 0.01 0.02 0.03 0.01 BDL BDL 0.01
Precipitation efficiency %
Cu Fe Al Co Ni Mn Li
99.9, 99.9 99.9 99.9 NA NA 99.9

The obtained precipitated mass and the filtrate in the above test were then sent to the existing process for further processing and to the ETP, respectively.

EXAMPLE 4
Experimental Analysis
Experiment 1:
In batch 1, 100 g of the anode material (leach residue obtained from the battery recycling plant) was agitated with 30 ml nitric acid and 300 ml water for 2 h. The slurry was filtered. The filtrate-1 (400 ml) and residue-1 (132.8 g) was collected. The residue-1 was further agitated with 15 ml of sulphuric acid and 10 ml of hydrogen peroxide for 2 hours. The slurry was filtered. Both filtrate-2 (450 ml) and residue-2 (128.5 g) was collected. The residue-2 was further washed with water and dried at 90oC for 2 hour to get pure graphite (90 g). Table 5 presents the chemical analysis of anode material.
Table 5: Chemical analysis of anode material

Experiment 2:
In batch 2, 500 g of the anode material (leach residue obtained from the battery recycling plant) was agitated with 150 ml of nitric acid and 1460 ml of water for 2 hours. The slurry was filtered. The filtrate-1 (1945 ml) and residue-1 (664.3 g) was collected. The residue-1 was further agitated with 75 ml of sulphuric acid and 50 ml of hydrogen peroxide for 2 h. The slurry was filtered. Both filtrate-2 (2225 ml) and residue-2 (631.2 g) were collected. The residue-2 was further washed with water and dried at 90oC for 2 hour to get pure graphite (442 g). The filtrate-1, filtrate-2, residue-1, and pure graphite obtained in batches 1 and 2 were analyzed by MP-AES (Microwave Plasma Atomic Spectrophotometer) and presented in Table 6.
Table 6: Chemical analysis of samples of batches 1& 2

Experiment 3:
In batch 3, 10 kg of the anode material (leach residue obtained from the battery recycling plant) was agitated with 3 L nitric acid and 30 L water for 2 h. The slurry was filtered. The filtrate-1 (40 L) and residue-1 (13.3 kg) were collected. The residue-1 was further agitated with 1.5 L of sulphuric acid and 1 L of hydrogen peroxide for 2 hours. The slurry was filtered. Both filtrate-2 (45 L) and residue-2 (12.9 kg) were collected. The residue-2 was further washed with water and dried at 90oC for 2 hour to get pure graphite (9.2 kg). The filtrate-1, filtrate-2, residue-1, and pure graphite obtained in batch 3 were analyzed by MP-AES (Microwave Plasma Atomic Spectrophotometer) and presented in Table 7.
Table 7: Chemical analysis of samples of batch 3

Therefore, the present invention provides a method for recovering highly pure and battery grade graphite by a clean, green and environmental friendly process.
Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

,CLAIMS:CLAIMS

We claim:
1. A method for recovering high pure graphite from waste lithium-ion batteries, comprising the steps of:
a) leaching the anode material which is impure graphite obtained from spent lithium-ion battery of the waste lithium-ion battery for 2-3 hours to remove metal values other than aluminum to obtain a filtrate and residue of leach liquor;
b) leaching of traces of the aluminum from the residue of the leach liquor obtained in step (a) for 2-3 hours to obtain a cake;
c) washing and drying of the cake obtained in step (b) with water at a predetermined temperature for 2-3 hour to obtain highly pure graphite;
d) recycling the leach liquor obtained in step (a) multiple times to concentrate the leach liquor and to get enriched metal ions in the liquor; and
e) precipitating the metal ions obtained from the enriched liquor in step (d) followed by washing of the cake for recovery of highly pure and battery grade graphite with percentage purity in a range of 98-99%.

2. The method for recovery as claimed in claim 1, wherein the leaching of step (a) is carried out with nitric acid (30% w/v) at pulp density (30% w/v) to remove metal values other than aluminium.

3. The method for recovery as claimed in claim 1, wherein said metal values other than aluminium of step (a) are copper (Cu), cobalt (Co), nickel (Ni), lithium (Li), and manganese (Mn).

4. The method for recovery as claimed in claim 1, wherein the leaching of step (b) is carried out with sulphuric acid (15% w/v) and hydrogen peroxide (10% w/v) at pulp density (30% w/v) to obtain a cake.

5. The method for recovery as claimed in claim 1, wherein the predetermined temperature of step (c) is 85-90°C.

6. The method for recovery as claimed in claim 1, wherein said metal ions are precipitated by using soda solution (25% w/v) at a pH in a range of 10-10.5.

7. The method for recovery as claimed in claim 1, wherein said process is clean, green and environmentally friendly.