FIELD OF THE INVENTION

The present invention relates to an improved process and method of recovering metals of value from used Lithium batteries (hereinafter LiBs). More particularly, the invention provides a method for recovering cobalt, lithium, manganese along with other metals of value from used LiBs rich in manganese content. The method includes combination of chemical and physical processes for separation, limiting the use of chemical for removing minor impurities. 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 Umicore 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.

US Pat. No. 8616475 discloses a recovery process of copper, aluminium, carbon and cathode material from spent lithium ion batteries having lithium metal oxide cathode material. The main drawback of the disclosed method is its limited nature of recovery, and inefficiency to recover metals in their purest form. The method neglects other recoverable materials of spent lithium ion batteries including those present in protection circuit boards. Hence, a single versatile approach is needed to recover 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.

US 20130302226A1 discloses a method and apparatus for extracting useful elements like cobalt, nickel, manganese, lithium, and iron from spent lithium ion batteries to produce active cathode materials for new batteries. The disclosed method lacks in versatility to recover metallic contents of spent lithium ion batteries. Further, the disclosed method relates to mixed cathode chemistry and doesn't focus much on purity of separate cathode extraction in their purest form.

Further, a majority of the processes that are known in the art use harmful chemicals to recover the metals in high quantity. On the other hand, state of the art physical processes do not result into satisfactory recovery of metals, in quantitative as well as qualitative terms. Accordingly, there is required an eco- friendly and cost effective method to recover metal of values in good quantity without compromising on the quality. The recovery and reuse of the cathode material would lessen pressure on supply of lithium cathode materials such as nickel and cobalt.

The known processes in the art majorly use harmful chemicals to recover the metals in high quantity. On the other hand, state of the art physical processes do not result into satisfactory recovery of metals, in quantitative as well as qualitative terms.

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 recovering metals of value like nickel, cobalt, manganese, copper, iron, aluminium etc from used LiB.

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 present invention is to provide a method utilizing least amount of chemical reactants in the overall recovery process.

Yet another object of the present invention is to provide an In-Situ resource utilization approach to recover metal values in their highly purified form. Yet another object of the invention is to provide a method for recovering metals of value from Li Ion batteries which majorly includes physical processes for separation, limiting the use of chemical 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 method for recovery of valuable metals from used lithium batteries having high manganese content. The valuable metals include nickel, cobalt, manganese, copper, iron, aluminium etc. In this method, lithium ion battery is used as a raw material that undergoes through unit operations like shredding, sieving, washing, filtration, precipitation, leaching, electrolytic separation, density separation, magnetic separation to recover nickel, cobalt, manganese, copper, iron, aluminium and other valuable metals. The method of the present invention provides 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 batteries comprises the following major steps of: i) Wet shredding of batteries

ii) Floatation followed by wet sieving

iii) Filtration for the separation of mixed metal powder from lithium ion iv) Electrolytic process for dissolution of cobalt.

v) Removal of Aluminum from leach liquor. vi) Electrolytic process for Recovery of pure cobalt metal and Manganese dioxide.

vii) Magnetic separation for removal of PCBs, copper and aluminum matrix. viii) Lithium recovery as lithium carbonate by precipitation of wash liquor of step (iii)

In an embodiment of the present invention, maximum elements were separated by physical process instead of chemical process which gives the benefit of cost saving in chemical treatment of liquid and solid effluents. Chemicals are used to dissolve only minor impurities from electrolyte which lead to the process economically attractive. 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 without substantial use of chemical solutions. The process majorly depends of physical separation of the metals without compromising on the quality of the recovered products and by-products. The method of the present invention comprises the following steps of: i) Wet shredding of batteries.

ii) Floatation followed by wet sieving.

iii) Filtration for the separation of mixed metal powder from lithium ion. iv) Electrolytic process for dissolution of cobalt.

v) Removal of Aluminum from leach liquor.

vi) Electrolytic process for Recovery of pure cobalt metal and Manganese dioxide.

vii) Magnetic separation for removal of PCBs, copper and aluminum matrix. viii) Lithium recovery as lithium carbonate by precipitation of wash liquor of step (iii)

The lithium batteries are shredded and sieved in a wet environment. The contents that are found oversized, further sent for density separation step that causes separation of plastic and metallic contents depending upon their densities. On the other hand, the undersized particles are washed separately and filtered. The filtrate and residue obtained are treated separately for recovery of metal values.

Lithium obtained from the wash liquor was precipitated using saturated sodium carbonate solution, copper, aluminum and PCB were separated by magnetic separation followed by density separation.

Residue obtained after filtration is sent for electrolytic processing for cobalt leaching and separation of cobalt and manganese thereafter. In the final step of the electrolytic processing, manganese dioxide and cobalt are obtained in pure form.

The major steps of process are described in details as follows: i) Wet shredding of batteries: In this step, spent batteries are fed 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. The Shredder is designed in such a way to get size after shredding is of less than 10 mm. ii) Floatation followed by wet sieving: In this step from the shredder output slurry, plastic/Teflon matrix which floats over water is removed and then from the slurry particle of below 600 microns size is passed through a sieve. From above the sieve metals like copper foils, aluminum casing and PCBs are collected. iii) Filtration for the separation of mixed metal powder from lithium ion:

In this step slurry containing particles of size less than 600 microns was filtered through a filter press. The filtrate contains dissolved lithium ions. The cake contains cobalt ions with some metal impurities and organic matrix. iv) Electrolytic process for dissolution of cobalt: The cake obtained in step (iii) is taken in an electrolytic cell at the anode compartment. The electrolytic cell consists of Cathode made of SS-316 and Lead Anode separated by filter cloth. The electrolyte is a mixture of 10 % sulphuric acid in the first cycle. From the second cycle onwards, spent electrolyte, i.e. leach liquor is further processed to remove Aluminum. Final pH of the electrolyte was maintained as 1.2. Copper powder deposited was striped out from the cathode. v) Removal of Aluminum from leach liquor: The above leach liquor is purified by removing the traces of Aluminum by increasing the pH to 5.5 using sodium hydroxide. vi) Electrolytic process for Recovery of pure cobalt metal and Manganese dioxide: Purified leach liquor of step (v) is fed into cathode compartment of another cell. Anolyte of the cell is sucked out through a pump and fed into cell 1. (The acid generated by the deposition of cobalt at cathode and Manganese dioxide at the anode is used for leaching the metal content of the mixed metal powder of the battery). To deposit Mn as Mn0 ₂ , temperature of the cell is maintained above 95 degrees Centigrade. vii)Lithium recovery as lithium carbonate by precipitation of wash liquor of step (iii): In this step, the wash liquor obtained from step (iii) is treated with saturated solution of soda ash to increase the pH and maintain it between 11-11.5 at 90 to 100°C for 4hrs. viii)Removal and separation of PCBs, copper and aluminum matrix of Step

(ii): In this step, floating matrix of mixture of PCBs, Copper and Aluminum obtained from step (ii), is collected. Using density separation in water, plastic matter floats and is removed, denser particles comprise particles of PCBs, those containing copper, iron, and aluminum and are separated by using a magnetic separator. The magnetic part contains iron containing particles and gold containing particles of PCBs. The nonmagnetic part is rich in Copper and Aluminum. The non magnetic particles are again made to undergo density separation method for separating copper and aluminum.

In the most preferred embodiment, the present invention provides a process for recovering metals from spent Lithium batteries comprising the steps of: a) shredding the lithium batteries into particles of a preferable size, in water such that the water level is well above the level of the batteries to obtain a slurry of shredded particles and floating plastic and Teflon matrix;

b) removing the floating plastic and Teflon matrix of step a);

c) wet screening the slurry obtained in step a) through sieve of at least thirty mesh size to separate particles of varying sizes; wherein coarser pieces containing copper, aluminium and protection circuit modules are retained by the sieve and collected, and finer particles in the slurry, containing Lithium, Manganese and Cobalt are aggregated;

d) filtering the lithium, manganese and cobalt containing aggregate of step c) through a filter press to obtain a wash liquor containing lithium and a residue containing cobalt, manganese, metal impurities and organic matrix;

e) electrolysing the residue of step d) using concentrated sulphuric acid as electrolyte at preferred pH to obtain copper at cathode and a leach liquor;

f) treating the leach liquor obtained in step e) with sodium hydroxide solution to obtain a treated slurry;

g) filtering the treated slurry of step f) to obtain a metal compound cake and a filterate;

h) electrolysing the filterate of step g) to obtain a metal at cathode, a metal oxide at anode and an acid;

i) treating the wash liquor of step d) with saturated solution of soda ash at pH range of 11 to 11.5 and temperature ranging from 80 to 120 °C for 3-6 hours to obtain lithium carbonate precipitate and supernatant; and

j) separating magnetic and non-magnetic particles from the coarser pieces obtained in step c) using magnetic separation process.

In an embodiment, the process of the present invention provides several advantages over the techniques available in the present state of the art, i.e., it doesn't utilize high temperature exposures, organic matrix get decomposed by electrolytic oxidation at the anode, nascent oxygen generated at the anode acts as an oxidizing agent for dissolution of cobalt contents in sulphuric acid medium. In this way, the generated nascent oxygen gets utilized as an oxidizing agent within the environment and thereby, setting an In-Situ resource utilization approach in metal recovery process. In addition, use of sulphuric acid as electrolyte is for initiating cycle of batch processing. The subsequent cycles, electrolyte of previous batches can be reused. The purity of the products obtained during the processes was analyzed by Microwave Plasma Atomic Emission Spectrometer (MP-AES). Purity of cobalt metal obtained was around 99% and that of Lithium carbonate was found to be 98%.

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

EXAMPLE 1

The process was tested on a 100 Kg batch of spent lithium ion batteries (mixed). Initially, shredding of the batteries was done using a shredder having twin shaft with water spraying and shearing type cutting facility. Wet shredding of the batteries followed by floatation lead to removal of 16.4 Kg of plastics and polymer materials. Thereafter, the contents are sieved through a mesh (less than 600μπι) followed by filtration. About 47.2 Kg of cake (dry wt.) and 33.09 Kg mixture of aluminum, copper and steel containing PCBs were collected.

The mixture containing aluminum, copper and steel containing PCBs was subjected to magnetic separation step, that results into removal of 1.09 Kg of PCBs for the gold recovery process. The remaining mixture (about 32 Kg of aluminium and copper) was separated via density separation step, wherein aluminum (18.7 Kg) and copper (13 Kg) are selectively separated. From the dry cake (47.2 Kg), electro-chemical leaching was carried out as continuous process by maintaining the pH 1-1.2. Table 1 presents the chemical composition of the dried powder.

Table 1: Chemical composition of dried powder

EXAMPLE 2

Electro-chemical leaching of the dry cake was carried out in a rectangular cell (capacity 54 L) containing anodes (5 nos. made of lead, 240 x 100 mm) and cathodes (4 nos. made of SS-316, 330 x 100 mm). Five numbers of anodes covered with bags made of polypropylene carrying each 2 kg of the dry cake and four numbers of cathodes were placed at alternate position with the help of copper hanger bars and kept inside the cell containing 35 L of water and 7.75 L of concentrated sulphuric acid. To the electrolytic cell, 50 Ampere current was passed for 3 h to leach the material. During the leaching, copper powder (0.5 Kg) was striped out from the cathode in the first cycle. The leach liquor composition is presented in the Table 2 below.

Table 2: Composition of leach liquor

EXAMPLE 3

The leach liquor was taken for the removal of the aluminum by using sodium hydroxide solution (40% w/v, 3 L) at a pH of 5.5 under agitation for 1 h. The aluminum hydroxide cake (1.2 Kg) was removed by filtering the above slurry followed by washing and drying. The above filtrate (42 Lt) was taken in another electrolytic cell (containing 5 numbers of lead anodes and 4 numbers SS-316 cathodes) for the recovery of Co and Mn. After passing 100 Ampere of current for 4 h at 90-100 °C, 0.336 Kg of Co and 0.168 Kg of MnO _z were stripped out from the cathodes and anodes, respectively. The acid generated at the anode due to the deposition of Mn0 ₂ at anode and cobalt at cathode was fed into the leaching cell. The composition of the feed and the spent electrolyte are presented below in the Table 3.

Table 3: Composition of feed and spent electrolyte

EXAMPLE 4

From the second cycle onwards, spent electrolyte was taken for leaching instead of water and sulphuric acid. The same procedure was followed for the removal of aluminum and the aluminum free solution was used in Co and Mn0 ₂ recovery by electrolytic method described above. After 4 cycles by maintaining the concentration of Co and Mn in the electrolyte, the total Co-Metal and Mn0 ₂ recovered were 1.34 Kg and 0.67 Kg, respectively. The purity of the Co-Metal and Mn0 ₂ recovered were 99.3% and 96.5%, respectively. The chemical analysis of Co-Metal and MnO _z (EMD) are presented in the Table 4.

Table 4: Chemical analysis of Co-Metal and MnO _:

BDL=below detection level.