FIELD OF THE INVENTION
The present invention relates to an improved process and method of recovering metals of value from used Lithium Ion batteries (hereinafter LIB’s). More particularly, the invention provides a method for separating and recovering electrode materials like cobalt and graphite along with copper, aluminium, lithium, and manganese etc. from used LIB’s having rich manganese content. The invention provides for a cost effective, economic and environmental friendly process for recovering metals of value.

BACKGROUND OF THE INVENTION
A lithium-ion battery, commonly referred to as Li-ion battery or LIB, is a member of a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging. Li-ion batteries use an intercalated lithium compound as one electrode material, compared to the metallic lithium used in a non-rechargeable lithium battery. The electrolyte, which allows for ionic movement, and the two electrodes are the constituent components of a lithium-ion cell.
Lithium-ion batteries are common in consumer electronics. They are one of the most popular types of rechargeable batteries for portable electronics, with a high energy density, no memory effect, and only a slow loss of charge when not in use. Beyond consumer electronics, LIBs are also growing in popularity for military, battery electric vehicle and aerospace applications. For example, lithium-ion batteries are becoming a common replacement for the lead acid batteries that have been used historically for golf carts and utility vehicles. Instead of heavy lead plates and acid electrolyte, the trend is to use lightweight lithium-ion battery packs that can provide the same voltage as lead-acid batteries, so no modification to the vehicle's drive system is required. Due to its merits, such as a high electrical energy density, a high working voltage, a long cyclic life and no memory effect, etc., the lithium ion battery has been recognized as a battery system with a high potential for development. Accordingly, the use of lithium ion batteries is witnessing tremendous market growth. Consequently, along with an increase in the use of lithium ion batteries, a system for recycling and regenerating waste lithium ion batteries should be developed to solve the problems of contamination and risks associated with the use of lithium ion batteries.
Currently, there are two major recycle processes being used for lithium ion batteries:
1) These batteries are fed into electric furnaces already containing molten steel with the contained anode reducing carbons along with the separators and with flux to enrich the forming stainless steel alloy in cobalt, nickel and/or manganese. The lithium is fluxed into the slag and may be recovered at high cost with several extra processing steps. This is known as Umicor process.
2) The batteries are processed through a hammer mill and the screened -25 mesh slurry filtered and packaged. This slurry contains about 30% metals from the cathode along with the carbon. This metal rich mixture is shipped to an electric smelter for utilization in making steels. The copper and Aluminium foils are separately recovered from the process.
Although the valuable cobalt and nickel is recovered along with the manganese for scrap metal prices, the full value of the lithium metal oxide cathode material is lost and usually with no recovery of the lithium metal oxide. It would be a major improvement in the recycling of strategic materials and would lower the cost of lithium batteries if the full value of the lithium metal oxide cathode material could be achieved by complete recovery and regeneration for direct reuse in a new lithium-ion battery. In addition, almost all of the lithium would also be recovered in the cathode material and remain as part of the lithium metal oxide cathode as it is regenerated and used in the new battery.
The recovery and reuse of the cathode material would lessen pressure on supply of lithium cathode materials such as nickel and cobalt.
A lithium ion battery contains large amount of cobalt content along with some other heavy metals. Being a heavy metal element, cobalt causes great harm the environment.
JP2010231925A discloses a method and a device for separately collecting a metal material resource and a manganese resource from a secondary battery, especially a manganese lithium-ion secondary battery, only by a dry process. The major drawback of the disclosed method is that it requires high temperature exposure and has limited nature of the recovery. Hence, there is need of a single versatile approach capable of recovering all valuable materials present of spent lithium ion batteries in their purest form.
CN101988156 discloses a method for recycling metal components from waste lithium ion batteries wherein metal components are recovered in a pH controlled environment. Further, the method includes use of organic solvents to maintain pH of the processing environment. The pH sensitive approaches requires special attention and works effective at a particular pH which leads to incomplete recovery of metals especially when pH gets deviated from a specified range. Such approaches are thereby, considered to be less effective due to incompleteness of process that also affects quality and quantity of the recovered metals.
CN 1601805A discloses a method for recycling and processing worn-out lithium ion battery to recover cobalt, copper and precious metal elements such as lithium. In this method, the battery components are first crushed and then metals are recovered using chemical approaches depending on the metal to be recovered. The method generates hydrogen fluoride that may immediately convert to hydrofluoric acid, which is highly corrosive and toxic and has serious health effects upon exposure. Further, the recovered metals possess low purity concerns.
Hence, it is desirable to effectively manage or utilize its abundance not only to protect pollution of the environment, but also to make full use of resources in the area of waste management. Accordingly, there is required an eco-friendly and cost effective method to recover metal of values in good quantity without compromising on the quality.
OBJECT OF THE INVENTION
Accordingly, the main object of the invention is to provide an improved process and method of separating and recovering electrode materials like cobalt and graphite from used LIB’s.
Yet another object of the present invention is to provide a method to recover graphite, copper, aluminium, lithium, and manganese etc. from used LIB’s rich in manganese content.
Yet another object of the present invention is to provide a simple to operate approach to recover electrode materials in pure form so that they can be reutilized again.
Yet another object of the present invention is to provide a method to recover metal values in their highly purified form.
Yet another object of the invention is to provide a hydrometallurgical method for recovering metals of value from used LiB’s with limited use of chemicals for removing minor impurities.
Yet another object of the invention is to provide a cost effective, economic and environmental friendly process for recovering metals of value.
Still another object of the invention is to provide an eco-friendly and cost effective method to recover metal of values in good quantity without compromising on the quality.

SUMMARY OF THE INVENTION

The present invention relates to a process and method of recovering electrode materials like cobalt and graphite along with other valuable metals from used lithium-ion batteries having high manganese content. The valuable metals include lithium, manganese, copper, iron, aluminium etc. In this method, lithium ion battery used as a raw material that undergo through unit operations like shredding, sieving, filtration, precipitation, leaching, magnetic separation etc. The method of the present invention provide benefits including low processing costs, high recovery of copper and nickel-cobalt-manganese, thereby producing greater social and economical benefits.
In an embodiment of the present invention, the method of recovering metals of value from used Lithium Ion batteries comprises the following major steps of:

i) Wet shredding of batteries.
ii) Floatation followed by wet sieving for the separation of metals, electrolyte and plastic/polymer matrix.
iii) Filtration for the separation of mixed metal powder from lithium ion.
iv) Acid leaching of electrode powder material using sulphuric acid (pH 0.8-1.2) for recovery of graphite at 70-80 oC.
v) After graphite recovery, manganese is recovered as manganese dioxide using sodium hypochlorite solution (pH 1.2-1.8) at a temperature ranges from 40 to 60 ?C.
vi) The pH of the Manganese free solution obtained after step (v) is adjusted up to 4.5 using sodium hydroxide or caustic soda for Aluminum recovery.
vii) After Aluminium removal, the pH of the solution [obtained in step (vi)] is adjusted up to 5.5 using caustic soda or sodium hydroxide for copper recovery.
viii) The pH of the above copper free solution is adjusted to 8.5-9 using soda ash or sodium carbonate for precipitation of cobalt as cobalt carbonate. It is washed, dried and roasted to get cobalt oxide.
ix) Magnetic separation for removal of printed circuit boards (PCB) and steel for the copper and aluminum matrix.
x) Lithium recovery as lithium carbonate by precipitation of wash liquor of step (viii).

In an embodiment of the present invention, a simple to operate approach is provided to recover electrode materials in pure form so that they can be reutilized again. The process is thus unlike those generally used where chemicals are used to dissolve major element and then for separation of major element from other impurities. This makes the method of recovering metal values is environment friendly.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the system and method of the present invention may be obtained by reference to the following drawings:

Figure 1 elucidates the flow sheet of the process according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in detail 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.

Figure 1 elucidates the process and method for recovering metals of value from used Lithium ion batteries. The process majorly depends on separation and recovery of pure cobalt and other metals of value without compromising on the quality of the recovered products and by-products.

First of all, spent LIBs are feed into a shredder in presence of water above the battery level so that the water will act as a scrubbing agent as well as temperature controller. In the subsequent step, the contents are wet sieved for the separation of metals, electrolyte and plastic/polymer matrix. The contents are then sent for magnetic separation process for segregation of copper and aluminium. On the other hand, the particles (size < 600 µm) are sent for acid leaching process wherein graphite gets leached out. The graphite free solution is then undergoes series of steps for recovery of manganese, aluminium, copper, cobalt, and lithium.

The most preferred embodiment of the proposed invention is a process for recovering valuable metals from spent lithium ion batteries comprising the steps of:
a) shredding the lithium ion batteries into particles of a preferable size, in water, with water level well above the batteries being shredded to obtain a slurry along with shredded plastic and Teflon matrix and removing the plastic and Teflon matrix that floats on the water;
b) wet screening of the slurry through sieve of at least thirty mesh size to separate particles of varying sizes wherein the coarser particles including copper foils, aluminum casing and protection circuit modules are retained and a primary slurry containing mixture of metals including cobalt, manganese, lithium, copper and aluminum are aggregated;
c) filtering the primary slurry through a filter press to obtain a wash liquor and a residue containing cobalt, manganese, lithium, copper and aluminum and drying the residue to obtain a dry cake;
d) preparing a secondary slurry by mixing the dry cake with water followed by addition of sulphuric acid under agitation at a temperature ranging from 70-80 oC for 3-4 hours and filtering the secondary slurry through a filter press to obtain a graphite rich residue and a leach liquor;
e) treating the leach liquor with sodium hypochlorite solution under agitation at a pH range 1.0 - 2.0 and a temperature ranging from 40-60 oC for 4-5 hours and washing and filtering the leach liquor to obtain pure manganese and filtrate;
f) treating the filtrate with 30% sodium hydroxide solution under agitation at a pH range 4.0-5.0 for 1-2 hours to obtain a aluminum hydroxide precipitate and supernatant;
g) treating the supernatant with 30% sodium hydroxide solution under agitation at a pH range 5.2-5.7 for 1-2 hours to obtain copper hydroxide precipitate and supernatant;
h) treating the supernatant of with 30% sodium carbonate solution under agitation at a pH range 8.5-9.0 for 2 hours to obtain cobalt carbonate precipitate and supernatant;
i) washing and drying the cobalt carbonate precipitate followed by roasting at a temperature range 850-900 oC to obtain pure cobalt oxide;
j) treating the supernatant of with saturated solution of sodium carbonate under agitation at a temperature ranging from 90-100 oC for 4 hours to obtain lithium carbonate precipitate and filtrate;
k) washing and drying the lithium carbonate precipitate at a temperature ranging from 110-115 oC for 2 hours to obtain pure lithium carbonate.

The invention will now be illustrated by the following non-limiting examples.

Example 1: A batch (batch 1) of 100 Kg spent lithium ion batteries was taken and processed as per the process specified in the present invention. Initially, the batch was subjected to shredding section wherein the batteries were shredded in the wet environment. The plastic and polymeric contents of the shredded batteries were separated by floating it over a solvent wherein plastic and polymeric materials are removed. After separation, the remaining contents are sieved through a mesh less than 600µm and filtered.

Upon filtration, a residue or filter cake weighing about 47.2 Kg (dry weight) and filtrate (about 33.09 Kg) were obtained. The filtrate contains mixture of aluminum, copper and steel, and PCBs. The magnetic and non magnetic contents present in the mixture are then magnetically separated. The PCB weighing about 1.09 Kg was separated for gold recovery. The remaining mixture (about 32kg) was subjected to density separation by air to get aluminum (18.7 Kg) and copper (13 Kg) separately.

The filter cake (47.2 Kg) obtained upon filtration was taken for the leaching step. Chemical composition of the dried form of filter cake is shown in Table 1.

Table 1: Chemical composition of filter cake (dried form)

For leaching step, the filter cake (47.2 kg) was taken and slurry is made with distilled water (143 liters). About 24.3 liters of sulphuric acid was then slowly added to the slurry and agitated at a temperature of 70 ºC for 4 hours. The slurry was cooled and filtered. The filtrate and residue obtained upon filtration was collected. The filtrate (leach liquor) was kept for leaching step whereas the residue (rich in graphite) was dried to get about 12.4 kg of graphite. The analysis of the leach liquor (LA) and the residue are shown in Table 2.

Table 2: Chemical analysis of leach liquor (LA) and residue
Sample Co Mn Li Cu Al
Leach liquor, LA (g/l) 27.36 16.21 5.26 0.225 3.71
Residue (%) 0.16 0.05 0.01 1.52 4.77

About 140 liters of sodium hypochlorite solution was added to leach liquor (LA) and agitated at pH 1.5 and temperature 50 ºC for 5 hours which results in precipitation of manganese. The liquor (LA) was filtered; manganese rich cake is recovered and dried to obtain a dry mass (about 6.12 kg). The precipitation efficiency of more than 99% was observed in this step. The manganese free liquor (L1) or filtrate was kept for recovery of aluminium, copper, cobalt, and lithium in the succeeding steps.

Aluminium recovery: The manganese free liquor (L1) was taken for the recovery of aluminum. About 13.26 Liters of 30% NaOH solution was added to (L1) and agitated at pH 4.5 for one hour. Aluminium was precipitated as aluminium hydroxide (2.6 kg), filtered and recovered. The filtrate or aluminium free liquor (L2) was kept for copper recovery.

Copper recovery: The Aluminium free liquor (L2) contain trace amount of copper (151 ppm) which was recovered as copper hydroxide (0.07 Kg) by adding 30% (w/v) of NaOH solution (0.21 Lt) at a pH of 5.5 for 1 h under agitation.

Cobalt recovery: In the subsequent step, cobalt was recovered as cobalt carbonate from the copper free liquor (360 Lt) by agitating it with 40.6 Lt of sodium carbonate solution (30% w/v) at a pH of 8.5 for 2 hours. More than 99% precipitation efficiency was observed and 13.62 Kg of CoCO3 (purity 96.1%) was collected. The chemical analysis of the cobalt carbonate is presented in Table 3.

Table 3: Chemical analysis of cobalt carbonate

The dried cobalt carbonate was roasted at 900 ºC for 2 hours to get cobalt oxide. The cobalt oxide obtained (8.58 Kg) was analyzed and the purity was found to be of 95.1%. The chemical analysis of the cobalt oxide is shown in Table 4.

Table 4: Chemical analysis of cobalt oxide

The Cobalt free filtrate (350 Lt) containing 3.31 g/L of lithium was agitated by adding saturated solution of sodium carbonate (27.9 Lt) at 90 ºC for 4 hours. The precipitated lithium carbonate in the slurry was cooled to room temperature, filtered, washed and dried at 110 ºC for 2 hours to get 6.83 Kg of lithium carbonate (purity 99.7%). The chemical analysis of the lithium carbonate is shown in Table 5.

Table 5: Chemical analysis of lithium carbonate

Example 2: In another 100 Kg batch (batch no. 2) of the same spent lithium ion batteries, the process was tested. The batteries were shredded in wet environment followed by floatation which leads to removal of about 15.2 Kg of plastics and polymer materials. The contents are then sieved through a mesh less than 600 µm followed by filtration. Upon filtration, residue of filter cake weighing about 48.3 Kg (dried form) and filtrate (about 32.2 Kg) containing mixture of aluminum, copper and steel containing PCBs were separated.

The filtrate was magnetically separated that results in removal of about 1.09 Kg of PCBs for the gold recovery process. The remaining mixture (about 31.2 Kg) was proceeded for density separation (by air) to get aluminum (18.8 Kg) and copper (13 Kg).
The dry cake (47.2 Kg) obtained upon filtration was taken for the leaching step. Table 1(a) presents the chemical composition of the dry cake.

Table 1(a): Chemical composition of dry cake.

Slurry was formed by mixing dry cake with 150 liters of water to dry cake obtained upon filtration in the previous step. To this slurry, about 24.7 liters of sulphuric acid was slowly added and agitated at a temperature of 70 ºC for 4 hours. The slurry was cooled and filtered and both filtrate (leach liquor, LB = 252 Lt) and graphite rich residue (about 12.7 Kg of graphite) were collected. The analysis of the leach liquor, LB is shown in Table 2(a).

Table 2(a): Chemical analysis of leach liquor (LB) and residue.
Sample Co Mn Li Cu Al
Leach liquor, LB (g/l) 27.29 16.50 5.46 0.205 3.76
Residue (%) 0.15 0.04 BDL 1.07 4.3

In the same manner, manganese (Mn) was removed from the leach liquor, LB at a pH of 1.5 and temperature 50 ºC for 5 hours by agitating it with sodium hypochlorite solution (145 Lt). More than 99% precipitation efficiency was observed and 6.12 Kg of manganese cake (dried form) was collected.

In the next step, aluminum (Al) was removed as aluminum hydroxide (2.4 Kg) from the manganese free liquor (359 Lt) at a pH of 4.5 by adding 30% (w/v) NaOH solution (13.82 Lt) for 1 h under agitation. The Al-free liquor containing traces amount of copper (141 ppm) was recovered as copper hydroxide (0.077 Kg) by adding 30% (w/v) of NaOH solution (0.2 Lt) at a pH of 5.5 for 1 h under agitation.

In the subsequent step, cobalt was recovered as cobalt carbonate from the Cu-free liquor (368.2 Lt) by agitating with 42.34 Lt of sodium carbonate solutions (30% w/v) at a pH of 8.5 for 2 h. More than 99% precipitation efficiency was observed and 14.02 Kg of CoCO3 (purity 96.2%) was collected. The chemical analysis of the cobalt carbonate is presented in Table 3a.

Table 3a: Chemical analysis of cobalt carbonate

The dried cobalt carbonate was roasted at 900 ºC for 2 h to get cobalt oxide. The cobalt oxide obtained (8.58 Kg) was analyzed and the purity was found to be of 96%. Table 4a presents the chemical analysis of the cobalt oxide.
Table 4a: Chemical analysis of cobalt oxide

The Co-free filtrate (340 Lt) containing 3.31 g/L of lithium was agitated by adding saturated solution of sodium carbonate (27.9 Lt) at 90 ºC for 4 h. The precipitated lithium carbonate in the slurry was cooled to room temperature, filtered, washed and dried at 110 oC for 2 h to get 6.83 Kg of lithium carbonate (purity 99.7%). The chemical analysis of the lithium carbonate is presented in Table 5a.

Table 5a: Chemical analysis of Lithium carbonate

CLAIMS
We claim:
1. A process for recovering valuable metals from spent lithium ion batteries comprising the steps of:
a) shredding the lithium ion batteries into particles of a preferable size, in water, with water level well above the batteries being shredded to obtain a slurry along with shredded plastic and Teflon matrix;
b) removing the plastic and Teflon matrix that floats on the water in step a);
c) wet screening of the slurry obtained in step a) through sieve of at least thirty mesh size to separate particles of varying sizes, wherein the coarser particles including copper foils, aluminum casing and protection circuit modules are retained and a primary slurry containing mixture of metals including cobalt, manganese, lithium, copper and aluminum are aggregated;
d) filtering the primary slurry obtained in step c) through a filter press to obtain a wash liquor and a residue containing cobalt, manganese, lithium, copper and aluminum;
e) drying the residue of step d) to obtain a dry cake;
f) preparing a secondary slurry by mixing the dry cake of step e) with water followed by addition of sulphuric acid under agitation at a temperature ranging from 70-80 ºC for 3-4 hours;
g) filtering the secondary slurry of step f) through a filter press to obtain a graphite rich residue and a leach liquor;
h) treating the leach liquor of step g) with sodium hypochlorite solution under agitation at a pH range 1.0-2.0 and a temperature ranging from 40-60ºC for 4-5 hours;
i) washing and filtering the leach liquor of step h) to obtain pure manganese dioxide and filtrate;
j) treating the filtrate of step i) with 30% sodium hydroxide solution under agitation at a pH range 4.0-5.0 for 1-2 hours to obtain a aluminum hydroxide precipitate and filtrate;
k) treating the filtrate obtained in step j) with 30% sodium hydroxide solution under agitation at a pH range 5.2-5.7 for 1-2 hours to obtain copper hydroxide precipitate and filtrate;
l) treating the filtrate obtained in step k) with 30% sodium carbonate solution under agitation at a pH range 8.5-9.0 for 2 hours to obtain cobalt carbonate precipitate and filtrate;
m) washing and drying the cobalt carbonate precipitate followed by roasting at a temperature range 850-900 ºC to obtain pure cobalt oxide;
n) treating the filtrate obtained in step l) with saturated solution of sodium carbonate under agitation at a temperature ranging from 90-100ºC for 4 hours to obtain lithium carbonate precipitate and filtrate; and
o) washing and drying the lithium carbonate precipitate at a temperature ranging from 110-115 ºC for 2 hours to obtain pure lithium carbonate.

2. The process for recovering metals of value as claimed in claim 1, wherein the preferable size of particles obtained through shredding is 600 micron.

3. The process for recovering metals of value as claimed in claim 1, wherein the coarser pieces of step c) are processed using magnetic separator to segregate magnetic part comprising protection circuit module from non magnetic part comprising copper and aluminum.

4. The process for recovering metals of value as claimed in claim 1, wherein the cobalt oxide obtained in step m) has purity of 96.1% with cobalt content of more than 72%.

5. The process for recovering metals of value as claimed in claim 1, wherein the cobalt oxide obtained in step m) has metal impurity level below 2%.

6. The process for recovering metals of value as claimed in claim 1, wherein the lithium carbonate obtained in step o) has purity of 99.7% with lithium content of more than 18.5%.

7. The process for recovering metals of value as claimed in claim 1, wherein the lithium carbonate obtained in step o) has metal impurity level below 0.3%.