FIELD OF THE INVENTION

The present invention relates to an improved process of recovering metals of value from spent Lithium batteries. More particularly, the invention provides a method for recovering cobalt and Nickel from spent lithium batteries. The method comprises eco-friendly yet efficient procedure for recovering valuable metals in highly purified and saleable form.

BACKGROUND OF THE INVENTION

Today, lithium batteries appear to be all over, as they provide energy for most compact electronics, hardware tools, electric vehicles, and the like. Lithium battery refers to a family of batteries with variable chemistries. In a broader sense, lithium batteries may be classified as lithium-metal batteries and lithium-ion/lithium-polymer batteries. The former one, are usually, non rechargeable kind of batteries that are commonly used in calculators, cameras, watches, etc. They are comprised of cells, containing highly reactive lithium metal. Whereas, the lithium-ion/lithium-polymer batteries are rechargeable batteries that are used in cell phones, laptops, electric vehicles, wireless devices and the like. The lithium-ion batteries comprise cells, containing lithium in ionic form. Lithium-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 polymer batteries are the rechargeable batteries, which can be used over a long period. They utilize a solid polymer composite such as polyacrylonitrile as a physical separator that minimize the risk for internal shorting that tend to cause fires and explosions. Accordingly, lithium 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, lithium batteries are also growing in popularity for military, battery electric vehicle and aerospace applications. For example, lithium 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 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 battery has been recognized as a battery system with a high potential for a developmental point of view.

Hence, the use of lithium batteries is witnessing tremendous market growth. Consequently, along with an increase in the use of lithium batteries, a system for recycling and regenerating waste lithium batteries should be developed to solve the problems of contamination and risks associated with the use of lithium 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.

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 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 a new battery. US 8616475 Bl discloses recovery of lithium ion batteries for recovery of copper, aluminum, carbon and cathode material from spent lithium ion batteries having lithium metal oxide cathode material. The cathode material which is recovered can be regenerated with lithium hydroxide and reused as cathode material. The main drawback of the invention is the use of chemicals such as kerosene, isobutyl carbinol and the metal values recovered lack in purity required for reuse in lithium batteries.

US 8882007 Bl discloses a process for recovering and regenerating lithium cathode material from lithium-ion batteries. The method includes the steps of isolating the cathode particles and then regenerating the cathode particles for use in the same type of battery, involves the wet crushing of the used batteries, then wet screening to remove the coarser electrode foils, plastic and separators from the slurry of the mixed fine electrode materials, comprising the lithium metal oxides and mixed oxides and carbon anode materials. For each processing run, only one cathode type of lithium-ion battery is processed in order to have only one type of lithium-ion cathode material in the slurry mix. The main drawback of the present invention is the high precision required to carry out the process such as wet crushing the batteries using either water or under the presence of nitrogen or both. Also, the heating temperature in the invention has to be precisely maintained such that it destroys the binder that may modify the surface of carbon and does not burn the anode carbon. The recovery and reuse of the cathode material would lessen pressure on supply of lithium cathode materials such as nickel and cobalt. In addition, the cathode materials require extremely high purity levels and must be almost entirely free of unwanted metal impurities such as iron, vanadium and sulphur. 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 present invention is to provide an improved method and process of recovering cobalt, nickel and other valuable metals from spent Lithium batteries. Yet another object of the present invention is to provide a process that recovers cobalt and nickel in their highly purified or saleable form.

Yet another object of the present invention is to provide a process for recovering other metals including manganese, aluminium, abundant in lithium batteries.

Yet another object of the present invention is to provide an approach that utilizes least amount of chemical reactants in the overall recovery process.

Yet another object of the present invention is to provide an approach that selectively adsorbs the metals to avoid contamination of other metals or impurities, for effective recovery of metal values in purified form.

Yet another object of the invention is to provide a method for recovering metals of value from Lithium 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 an improved method and process for recovery of valuable metals from spent lithium batteries in their highly purified and saleable form. In this method, the spent lithium batteries are taken and shredded in a wet environment. The shredded batteries are sent for wet screening to separate coarser particles containing copper, iron, aluminium, shredded plastic contents, and finer particles containing lithium, nickel, cobalt and manganese, etc.

The finer particles contain valuable materials like cobalt, nickel, and manganese wherein cobalt and nickel are recovered in saleable form using a selective adsorption technique. The finer particles obtained after wet screening are pass through a resin column filled with adsorbents or resins for selectively loading the particular type of metals.

The method of the present invention provides benefits including low processing costs, recovery of nickel and cobalt in pure and saleable form, thereby producing greater social and economical benefits.

In an embodiment of the present invention, the method of recovering value metals from spent lithium batteries, said method comprises the steps of: a) shredding the lithium batteries in water using a shredder, with water level well above the level of the batteries being shredded to obtain a slurry and shredded plastic and polymer;

b) removing the plastic and polymer that floats on the water in step a); c) wet screening the slurry obtained in step a) through sieve of at least 600μηι size to separate coarse and fine particles; wherein coarse particles containing copper, aluminium, steel and printed circuit boards from screened slurry are retained by the sieve and fine particles containing cobalt, manganese, copper, nickel, aluminium and lithium are aggregated; d) leaching a part of fine particles from step c) in a leaching cell using water and sulphuric acid by maintaining a pH of 0.8-1.2 and filtering to collect leach liquor containing cobalt, manganese, copper, nickel, aluminium and lithium and dried residue containing graphite;

e) removing aluminium as aluminium hydroxide at a pH ranging from 4 to 5 maintained using caustic soda solution by agitating the leach liquor of step d) with a 30% (w/v) NaOH solution;

f) obtaining nickel and copper from aluminum free leach liquor by passing it through a selective resin column using sulphuric acid;

g) feeding the leach liquor from step f) into electrolytic cell for obtaining pure cobalt at cathode and electrolytic manganese dioxide at anode;

h) purifying nickel using sulphuric acid solution and precipitating said solution at pH 9-9.5 as nickel carbonate using soda ash solution and drying the precipitate thus obtained at 110° C for 2 hours; wherein the Co-Metal and Mn0 ₂ recovered in step i) has purity of 99.9% and 96.5%, respectively; and

the nickel carbonate obtained in step k) has a purity of 98.28%.

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 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 provides a novel method for recovery of high value metals from spent lithium batteries shred wherein different processes are carried out in a manner that such physical processes including wet shredding, washing, floatation to separate light materials like polymer /plastics, wet sieving and selective adsorption without any harmful chemical process helps in recovering cobalt, electrolytic manganese dioxide and nickel yield in a highly pure form.

Figure 1 elucidates the process and method for recovering metals of value from used Lithium batteries (LB's) without substantial use of chemical solutions. The process majorly depends of physical separation of the metals and selective adsorption or loading of metals by passing the metal rich liquor through a resin column. The process recovers valuable metals without compromising on the quality of the recovered products and by-products. The method of recovering value metals from spent lithium batteries, said method comprises the steps of: a) shredding the lithium batteries in water using a shredder, with water level well above the level of the batteries being shredded to obtain a slurry and shredded plastic and polymer;

b) removing the plastic and polymer that floats on the water in step a);

c) wet screening the slurry obtained in step a) through sieve of at least 600μπι size to separate coarse and fine particles; wherein coarse particles containing copper, aluminium, steel and printed circuit boards from screened slurry are retained by the sieve and fine particles containing cobalt, manganese, copper, nickel, aluminium and lithium are aggregated; d) leaching a part of fine particles from step c) in a leaching cell using water and sulphuric acid by maintaining a pH of 0.8-1.2 and filtering to collect leach liquor containing cobalt, manganese, copper, nickel, aluminium and lithium and dried residue containing graphite;

e) removing aluminium as aluminium hydroxide at a pH ranging from 4 to 5 maintained using caustic soda solution by agitating the leach liquor of step d) with a 30% (w/v) NaOH solution;

f) obtaining nickel and copper from aluminum free leach liquor by passing it through a selective resin column using sulphuric acid ;

g) feeding the leach liquor from step f) into electrolytic cell for obtaining pure cobalt at cathode and electrolytic manganese dioxide at anode;

h) purifying nickel using sulphuric acid solution and precipitating said solution at pH 9-9.5 as nickel carbonate using soda ash solution and drying the precipitate thus obtained at 110° C for 2 hours ;

wherein

the Co-Metal and Mn0 ₂ recovered in step i) has purity of 99.9% and 96.5%, respectively; and

the nickel carbonate obtained in step k) has a purity of 98.28%.

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 to obtain filtrate and residue.

Residue obtained after filtration is sent for leaching step using sulphuric acid at a pH ranging from 0.8 to 1.2. The aluminium content is removed from leach liquor by adjusting the pH to 4.5 using sodium hydroxide. The aluminium free liquor was purified by passing it through a column containing resins for selectively loading nickel and other impurities. The purified leach liquor was sent for electrolysis process for separation of cobalt and electrolytic manganese dioxide. The pure cobalt metal is obtained from the purified liquor by passing the current at a temperature ranging from 90-100 °C. In a separate step, nickel is stripped out from the resin by using an acid and soda ash treatment. The nickel is recovered as Nickel carbonate.

In another 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. The metals are selectively adsorbed using suitable adsorbents or resins. The selective adsorption avoids contamination of other metals, impurities and provides desired metals in their purified form.

The purity of the cobalt metal and Nickel carbonate obtained was found to be 99.9%.

EXAMPLE 1

A BATCHWISE TESTING OF PROCESS FOR RECOVERING PURE COBALT AND NICKEL FROM SPENT LITHIUM BATTERIES

In a 100 kg batch of different types of spent lithium-metal batteries and lithium- ion/lithium-polymer batteries, the process was tested. Shredding of the batteries was carried out 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. Then, by sieving through a mesh less than 600μπι followed by filtration, 47.2 kg of dried cake of fine particles and 33.09 kg mixture of coarse particles containing aluminum, copper and steel containing PCBs were collected. Magnetic separation of the mixture of coarse particles containing aluminum, copper and steel containing PCBs lead to removal of 1.09 kg of PCBs for the gold recovery process. Density separation of the remaining 32 kg of aluminum and copper by air lead to separate aluminum (18.7 kg) and copper (13 kg) selectively. From the dry cake of fine particles (47.2 kg), 4.7 kg was taken for leaching with 14 L of water and 2.3 L of sulphuric acid in the first batch by maintaining the pH 0.8-1.2. Table 1 presents the chemical composition of the dried fine particles.

Table 1 Chemical composition of dried fine particles

The above slurry was filtered and both filtrate (leach liquor- 1 = 17 L) and the dried residue (graphite = 0.94 kg) were collected. The analysis of the leach liquor- 1 is presented in Table 2.

Table 2 Chemical analysis of leach liquor- 1

From the leach liquor-1, aluminum (Al) was removed as aluminum hydroxide (0.48 kg) at a pH of 4.5 by agitation with 30% (w/v) NaOH solution (1.5 L) for 1 h. The analysis of the aluminum free liquor (leach liquor-2) is given in Table 3.

Table 3 Chemical analysis of leach liquor-2

The aluminum free liquor was passed through a column containing 2 L of resin (Cu and Ni selective). For each cycle, 2 L of leach liquor was passed through the resin column for purification. After loading, nickel and copper were stripped out from the loaded resin by using sulphuric acid of concentrations 5% and 15%, respectively (10 L each). The resin after stripping was washed with water and the regenerated resin was reused for the next cycle. The overall leach liquor was purified in eight cycles. The purified leach liquor-3 and the strip solutions obtained after 8 cycles were presented in Table.4 wherein BDL is a quantity below detection limit.

Table 4 Analysis of solution after resin treatment

In the next step, the purified leach liquor-3 (17.8 L) was fed into electrolytic cell (containing 5 of lead anodes and 4 of SS-316 cathodes wherein cathode electrode is made of a SS316 stainless steel on which carbon nanotube (CNT) and iron phthalocyanine (FePc) are deposited sequentially) for the preparation of high pure cobalt from cathode and electrolytic manganese dioxide from the anode by passing current 50 Ampere at 90-100 °C. After 4 h of electrowinning process, 0.17 kg and 0.085 kg of Co-metal and Mn0 ₂ were recovered. 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 5.

Table 5 Composition of feed and spent electrolyte

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 removing Cu and Ni by resin followed by electrolytic separation of Co and Mn0 ₂ 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 0.66 kg and 0.33 kg, respectively. The purity of the Co-Metal and Mn0 ₂ recovered were 99.9% and 96.5%, respectively. The chemical analysis of Co-Metal and Mn0 ₂ (EMD) are presented in the Table 6.

Table 6 Chemical analysis of Co-Metal and Mn0 ₂

The Ni-strip solution (10 L) was purified using the resin by loading and stripping with the same procedure. Nickel from the purified solution was precipitated at pH 9-9.5 as nickel carbonate using soda ash solution. The precipitated mass obtained was dried at 110° C for 2 h. The purity of nickel carbonate was analyzed and found to be 98.28%. The chemical analysis of dried nickel carbonate is presented in the Table 7.

Table 7 Chemical analysis of nickel carbonate

Therefore using selective adsorption technique using resin column and carrying out the process in a cyclic manner highly pure metal values are recovered without using any harmful chemicals. The method is environment friendly with low processing costs and recovers nickel and cobalt in pure and saleable form, thereby producing greater social and economical benefits.

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 description. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.