Background of the invention

The use of lithium batteries in various devices such as electric vehicles , mobile phones , mobile computers , etc . , has been constantly increasing since they entered the market in the 1990s . The negative electrode material in lithium-ion batteries ( LIBs ) consists of carbon/graphite ( applied onto a current collector made of copper ) . The positive electrode material is in the form of a compound consisting of lithium and precious metals , chiefly the transition metals nickel , manganese and cobalt . That is , the cathode material generally has the formula Li _a MbO _c , where M stands for one or more transition metal s . The lithium metal oxide Li _a MbO _c is usually applied onto a current collector made of aluminum . The lithium metal oxides that are most widely used to prepare the positive electrodes for lithium-ion batteries include lithium cobalt oxide ( LiCoCh or LCO) , lithium manganese oxide ( LiMn2O4 or LMO) , lithium manganese nickel oxide ( Li2Mn3NiOs or LMNO) , lithium nickel manganese cobalt oxide ( LiNi _x Mn _y Co _z 02 or NMC ; x+y+ z=l ) and lithium nickel cobalt aluminum oxide ( LiNi _x Co _y Al _z 02 or NCA; x+y+ z=l ) . Another type of cathode material worth mentioning is LiFePCh ( LFP ) .

There is a need for ef ficient battery recycling methods to minimi ze environmental pollution due to inappropriate disposal of the batteries and, obviously, regain the valuable metals from the spent batteries in a readily usable form .

Hydrometallurgical methods are well-suited to recover metals from lithium batteries , e . g . , by dissolving the metals in an acidic leachate . Industrial processes include dismantling the cathode material from the battery, exposing it to thermal/mechanical treatments to obtain the cathode material in the form of a powder ( this powder is often known in the industry by the name "black mass") . Precious metals are then extracted from the black mass using an acid. But the recycler may receive spent batteries from various sources, i.e., with varied cathode chemistry resulting in inconsistent metal composition. Because the black mass treated by the recycler may be a blend obtained from different types of batteries, it will very likely contain all three cathode transition metals mentioned above: nickel, manganese, and cobalt. Therefore, a suitable form of the cathode metals that is targeted by recyclers, i.e., one that can be readily recovered and utilized as raw material by the battery industry, consists of a mixed metal oxide of the formula Ni _x Mn _y Co _z 02 with a suitably adjusted x:y:z molar ratio as described below, or the corresponding hydroxide or carbonate.

In fact, the compounds that are directly isolated from the leaching solution by a coprecipitation reaction are the hydroxide Ni _x Mn _y Co _z (OH) 2 or carbonate Ni _x Mn _y Co _z (CO3) . The industry refers to these products of the coprecipitation reaction as hydroxide and carbonate precursors, respectively (a suitably milled mixture of the precursor and a lithium compound is calcined at high temperature to produce the cathode material) . The description that follows focuses on ternary precursors (x^O , y^O , z^O ) , but the invention can be applied to, e.g., single metal or binary precursors (e.g., z=0) .

To qualify as a raw material in the manufacture of cathodes by the lithium-ion industry, the recycled hydroxide (or carbonate) precursor needs to be of high purity. That is, free of other metals that are found in lithium batteries, namely, free of aluminum, copper, and iron. One or more steps of eliminating these metals is (are) incorporated into recycling processes prior to precipitation of the precursor. Removal of the metal impurities can be achieved either by pre-leaching purification step(s) , post-leaching purification step(s) or both. A pre-leaching purification step consists of slurring the black mass in a basic solution. In this manner, lithium is recovered and metal impurities such as copper, aluminum, iron can also be removed. Cathode metals (Ni, Mn, and Co) are unaffected; they remain in the black mass, which proceeds to the leaching step.

A post-leaching purification step is accomplished by pH adjustment/ addition of a precipitation agent to the pregnant leach solution (PLS) to precipitate metal impurities from the PLS. The filtrate contains solubilized Li ⁺¹ , Ni ²⁺ , Mn ²⁺ and Co ²⁺ salts. Next, coprecipitation is induced, to give Ni _x Mn _y Co _z (OH) 2 or NixMn _y Co _z (CO3) precursors with appropriate, predetermined x : y : z ratio .

As shown below, the invention refers to the latter approach, i.e., recovery of valuable metals from a black mass by acid leaching, with one or more post-leaching purification step(s) to remove Al, Fe and Cu from the PLS before the coprecipitation of the NixMn _y Co _z (OH) 2 or NixMn _y Co _z (CO3) precursor takes place.

Some attempts to separate aluminum and iron from acidic PLS were reported in the literature. WO 2020/212363 describes a process for removal of aluminum and iron from PLS by the addition of phosphoric acid to the PLS after leaching of the black mass with H2SO4/H2O2, with adjustment of the pH of the leachate to precipitate iron phosphate (FePO4) and aluminum phosphate (AIPO4) , that can be separated from the PLS by filtration. The filtrate obtained is amenable to further recovery of the cathode metals, Ni, Mn, Co, and Li. In US 2022-0131204, it was reported that a sieved cathode powder can undergo acidic leaching with H2SO4/H2O2. It is said that adjustment of the pH of the PLS to a range between 3.0-7.0 by addition of sodium hydroxide will result in precipitation of iron, copper and aluminum as corresponding hydroxides Fe(OH)3, Cu(OH)2 and Al (OH) 3, whereas Mn ²⁺ , Co ²⁺ , Ni ²⁺ remain solubilized in the solution. Likewise, in US 11,316,208 and WO 2022/006469, NaOH was added to the PLS to adjust the pH to about 3 and remove Al, Fe and Cu as insoluble hydroxides. Addition of sodium carbonate to PLS produced by H2SO4/H2O2 or HCI/H2O2 leaching was also reported, with adjustment to pH >4.5 (KR 2017061206) or pH >3.5 (KR 2019/0079988) to separate metallic impurities by hydrolysis.

The invention

Our process involves acidic leaching (e.g., with hydrobromic acid) of electrode material (black mass) of lithium-ion battery, to dissolve lithium, nickel, manganese, cobalt, aluminum, iron and copper to form pregnant leach solution (PLS) ; post-leaching purification of the PLS to obtain essentially Al, Fe and Cu-free solution; and coprecipitation of the remaining transition metals in the form of Ni _x Mn _y Co _z (OH) 2 or Ni _x Mn _y Co _z (CO3) .

To this end, a few post-leaching purification steps are performed. The pH of the PLS is strongly acidic (i.e., below 1.0) . Al, Fe, and Cu (partially) are separable from the PLS in the form of their insoluble hydroxides and/or carbonates upon addition of sodium carbonate to raise the pH of the PLS to a mildly acidic pH (defined herein as > 1.5; e.g., > 2.0, e.g., from 2.0 to 4.0, e.g., 2.5 to 3.5, e.g., 2.7 to 3.3, such as pH«3) . The insoluble forms of Al, Fe and Cu (the latter in part) can then be separated by filtration or any other solid/liquid separation technique. The reminder of copper can be further removed by electrowinning. The loss of Li and the transition metals Ni, Mn, and Co from the mildly acidic PLS is minimal, as these metals do not form insoluble hydroxides/carbonates within the mildly acidic pH range (e.g., though lithium carbonate is sparingly soluble in water, it dissolves well in the mildly acidic media.) The essentially Al, Fe and Cu-free filtrate is suitable for the coprecipitation of the Ni _x Mn _y Co _z (OH) 2 or NixMn _y Co _z (C0 ₃ ) .

The invention is primarily directed to a method, comprising: obtaining a strongly acidic PLS that was produced by acid leaching of electrode material of lithium-ion batteries; adding a carbonate source to the strongly acidic PLS to create a mildly acidic PLS; separating insoluble forms of aluminum and/or iron and/or copper from the mildly acidic PLS; and optionally electrowinning of copper (if present) , to obtain a purified PLS for recovery of cathode metals.

The recovery of the cathode metals includes the steps of: if needed, adjusting the molar ratio of transition metals that are present in the purified PLS; and coprecipitating a mixed transition metal hydroxide or carbonate under an alkaline environment in the presence of a complexant.

The method according to the invention is now illustrated in reference to the block flow diagram of Figure 1.

The first block in Figure 1 indicates the isolation of an electrode material, i.e., the "black mass", from battery cells following several treatment stages, depending on the type of technology utilized by the recycler. The methods by which the black mass is collected are not part of this invention and need not be described in detail. For example, the black mass is recovered after A) discharged batteries are dismantled to remove auxiliary parts (plastic components, electronic components, cables, connectors) to recover the battery cells; and B) battery cells undergo a series of mechanical processing steps including crushing and grinding to obtain the electrode material in a particulate form. Other recycling technologies include A) disassembling the batteries to collect the electronic and plastic parts as above, B) pyrolysis of battery cells (known as vacuum thermal recycling) whereby batteries are deactivated and volatile organic electrolytes are removed due to evaporation and C) deactivated pyrolyzed cells undergo mechanical treatment (crushing, grinding and sorting) to collect a fine fraction consisting of the electrode powder. See Georgi-Maschler et al., Journal of Power Sources 207 p. 173-182 (2012) , describing methods to recover the precious metals from lithium-ion batteries. As mentioned above, the feedstock may include, alongside the cathode metals (e.g., LiCoCh, LiMn2O4, Li2Mn3NiOs, LiNiMnCoCh and LiNiCoAlCh) also the graphite anode material and aluminum and copper (the metals of which the current collector foils in the batteries are made of) . The terms "electrode material" and "black mass" are used interchangeably. The black mass may be fed directly to the leaching reactor or undergo a caustic (pre-leaching) treatment. A caustic pretreatment is not mandatory and is not shown in Figure 1; it is exemplified in the experimental section and discussed in reference to Figure 3.

The second block in Figure 1 indicates jointly a) the step of acid leaching of the black mass, b) post-leaching purification steps and c) the step of adjusting the molar ratio of the Ni : Mn: Co metals that are present in the solution in solubilized form.

Starting with step a) , i.e., the acid leaching of the black mass, mineral acids such as sulfuric acid, hydrochloric acid and hydrobromic acid can be used. H2SO4 is perhaps the most common leachate. However, to reach good leaching efficiency of the black mass, both H2SO4 and HC1 would need the help of hydrogen peroxide (H2O2) or other reducing agents to advance the dissolution of the cathode material. We have recently shown (WO 2020/031178 and WO 2021/161316) that the leachability of some transition metals, especially manganese, is greatly improved with the use of hydrobromic acid. The use of HBr instead of H2SO4 allows for fast and efficient extraction in 99% yield/one cycle. Usually, bromide is oxidizable by metal ions present in the cathode material of lithium-ion batteries. That is, cathode metals that exist in high oxidation states, e.g., the trivalent cations Co ³⁺ and Mn ³⁺ /Mn ⁴⁺ , transform into the corresponding readily soluble divalent cations by gaining an electron from the bromide that is oxidized to generate elemental bromine (the Br2 formed can be treated by the techniques described in WO 2021/161316, i.e., Br2 is absorbed in an aqueous solution in the presence of a reductant that converts elemental bromine to hydrobromic acid, which is returned to the leaching reactor) .

Therefore, the description that follows usually focuses on HBr leaching of the black mass. But PLS that was generated by the action of H2SO4/H2O2 or HCI/H2O2 on black mass can also benefit from the post-leaching purification steps according to the invention, to enable coprecipitation of the hydroxide precursor in a highly pure form. The conditions of the HBr leaching step are described in much detail in reference to Figures 2 and 3. To understand the block flow diagram of Figure 1, suffice to say that the PLS generated by the acid leaching step is subjected to one or more post-leaching purification steps.

The major post-leaching purification step is the separation of aluminum, iron and/or copper (partially) from the PLS in the form of the corresponding hydroxide and/or carbonate compounds. The PLS is strongly acidic: its pH lies in the range below 1. Selective precipitation of aluminum, iron and/or copper (partially) in the form of hydroxides and/or carbonates occurs over a fairly narrow pH window within the mildly acidic range that in the context of the present invention is defined as 1.5 < pH < 4. The pH of the PLS is raised to the mildly acidic range, for example, to about 2.7 - 3.3, e.g., 2.8 - 3.2, e.g., pH«3 by addition of a water-soluble carbonate source (e.g., sodium carbonate) . A water-soluble alkali carbonate (Na2COs; K2CO3) can be introduced into the leach reactor, or to another reactor that was charged with the PLS, in a solid form, or as an aqueous stream of a concentrated (e.g., >10% by weight) or nearly saturated alkali carbonate solution, by slow addition under pH control so as not to exceed the mildly acidic pH window.

That is, pH is maintained and controlled by addition of carbonate source and acid, e.g., sodium carbonate and HBr (when necessary) . It should be noted that the precipitation reaction is exothermic and accompanied by foaming that occurs due to carbon dioxide evolution. So, the rate of adding the Na2COs to the PLS should match the capability of the reactor to remove the evolved CO2 and maintain the mildly acidic pH. The slurry formed upon precipitation of hydroxides and/or carbonates at the desired pH is stirred for a few hours to complete impurities precipitation, the precipitate is separated from the mildly acidic PLS, e.g., by filtration or any other solid/liquid separation method and washed with water. The f iltrate/supernatant obtained is essentially free of Al and Fe impurities but may still contain remnant cupric ions.

The secondary post-leaching purification step is therefore the elimination of copper from the mildly acidic f iltrate/supernatant by electrowinning. An electrochemical flow cell that is well suited for this goal is schematically shown in Figure 4, which is also described in reference to the experimental work reported below. The electrochemical flow cell is configured to enable the circulation of catholyte and anolyte streams . The catholyte stream consists of the metals-bearing solution (mostly Li ⁺¹ , Ni ⁺² , Mn ²⁺ , Co ²⁺ and the one to be electrodeposited - Cu ²⁺ ) , that is circulated through the cathodic compartment, whereas the anolyte stream consists of bromide solution such as hydrobromic acid (1-48 wt.%) or sodium bromide (1-35 wt.%) . The anode and the cathode half cells are separated by a selective membrane or porous separator. On industrial scale, the electrodes may be spaced about 0.1-10 cm apart. The electrochemical cell is connected to a power supply. The catholyte and anolyte streams are pumped separately through their respective compartments, with constant electrical current or voltage being applied to the cell, to reduce the copper ions and electrodeposit metallic copper on the cathode side, while an oxidation reaction occurs on the anodic side, whereby bromide is oxidized to elemental bromine. For example, voltage of about - 1-1.3 can be applied or current densities in the range of 1 to 1000 mA/ cm ² . By measuring the voltage or current outputs, the duration of the process and its selectivity can be controlled such that it can be terminated when desired results are achieved. For successful electrowinning, a cathode possessing high surface area is used, e.g., made of porous material such as carbon felt or metal meshes. When the cathode is loaded, it is removed from the cell and treated to collect the copper. For example, the copper plating can be detached from the cathode by peeling, chemical treatment such as acid, and by inverting the electrochemical process. A fresh cathode is then placed in the cell. The used anolyte solution can be reused for next cycle of black mass leaching process.

After the removal of aluminum, iron, and copper, a purified PLS is obtained. The purified PLS contains the cathode metals, i.e., the transition metals nickel, manganese, and cobalt, and most probably also lithium (unless it has been completely removed by an alkaline (pre-leaching) pretreatment) , in the form of solubilized salts, e.g., bromide salts (if hydrobromic acid was used as a leachate) or sulfate salts (if sulfuric acid was used as a leachate or to recover HBr as explained below) . But before the purified PLS is treated to coprecipitate the solubilized transition metals Ni, Mn and Co, the molar ratio of these metals is usually adjusted. Step c) in the second block in the block flow diagram of Figure 1 refers to the adjustment of the molar ratio of the transition metals in the purified PLS.

The molar ratio Ni : Mn: Co in the PLS is influenced by the origin of the raw material (as mentioned above, the black mass may be a blend obtained from nickel-rich, manganese-rich and cobalt- rich batteries and its composition is often inconsistent) . The composition of the purified PLS may therefore need to be adjusted ("corrected") by addition of one or more water-soluble salts (e.g., one or more of NiBr2, MnBr2 and CoBr2,- or one or more of N1SO4, MnS04 and C0SO4) to arrive at a predetermined target Ni : Mn: Co ratio acceptable by the industry. One commercially acceptable ratio is 1:1:1. Old NMC cathodes mainly consisted of NMC 111, the next generation was 311, then 532 and now mainly 622 and 811. The current trend in the industry is to lower the amount of cobalt due to its high price and low abundancy. The purified PLS, with its adjusted composition, can now be treated to recover the cathode metals, i.e., to produce the hydroxide or carbonate precursor. In terms of the subscripts in Ni _x Mn _y Co _z (OH) 2 or NixMn _y Co _z (CO3) , where x+y+z=l, then preferably: x>l/3, e.g., 1/3 < x < 8/10;

1/10<y, e.g., 1/10 < y < 1/3; and 0<z<l/3, e.g., 1/10 < z < 2/10.

For example, in the experimental section reported below, precursor with x=0.5, y=0.3 and z=0.2 was prepared. The third block in Figure 1 indicates the coprecipitation reaction of the transition metals. Coprecipitation of Ni, Mn, and Co in the form of the hydroxide precursor can be achieved with the aid of alkali hydroxide base, usually sodium hydroxide or lithium hydroxide, at a strongly alkaline pH (>10) , in the presence of a complexing agent in the reaction medium, typically aqueous ammonia. It should be noted that ammonium hydroxide (or ammonium carbonate) can alone serve the two goals, i.e., creation of an alkaline environment and supply of the complexing agent (NH3) . The reaction is conducted at elevated temperature, say, from 40 to 60°C. The growth of the metal hydroxide particles occurs throughout the reaction time. The conditions for particle growth depend on the pH of the reaction, temperature, stirring and concentration of the precipitating reagent. The coprecipitation of the Ni, Mn, and Co in the form of the carbonate precursor is achieved with the aid of sodium or potassium carbonate to create a nearly neutral or slightly alkaline pH (7-8) , again with the aid of ammonium hydroxide as a complexing agent or using ammonium carbonate alone.

The coprecipitation reaction can be carried out in a semi-batch mode (for example, by concurrent feeding of separate streams of the purified PLS, aqueous alkali hydroxide (usually applied as 2 M to 6 M NaOH solution) and the aqueous complexant (usually applied as 0.2 M to 10 M NH4OH solution) to a stirred reactor that was previously charged with the base and complexant. The coprecipitation reaction can be aided by seeding (e.g., addition of seeds of the precursor) .

The coprecipitation reaction can also be carried out continuously. For example, using a single continuous stirred tank reactor (CSTR) or a cascade configuration (two or more CSTR's in series) . In a cascade configuration, feed solutions consisting of the PLS and the precipitation reagent (NH4OH or two individual streams of NH4OH and NaOH) are fed to the first reactor and the effluent from the first reactor flows to the second reactor such that crystal growth (an important factor influencing filterability of a crystalized product) occurs chiefly downstream to the solution feeding. Seed suspension can also be fed continuously to the first/second crystallizer.

The precursor is filtered, washed and dried (lithium bromide remains in the solution and is recovered in the next step - see Figures 2 and 3 on lithium recovery) . Scanning Electron microscopy images shown below indicate that Ni _x Mn _y Co _z (OH) 2 compound (5:3:2) , which coprecipitated from metal bromide solution, consisted of largely spherical particles with flowerlike surface morphology created by thin sheets/plates arranged like petals, i.e., joined to form cells or channels which open onto the external surface of the spherical particles.

The fourth block in Figure 1 indicates the synthesis of the cathode material. A suitably milled mixture consisting of a lithium compound (e.g., hydroxide or carbonate) and the NixMn _y Co _z (OH) 2 or Ni _x Mn _y Co _z ( CO3 ) precursor prepared by the method of the invention enters a calcination furnace and is calcined at high temperature for several hours to produce the cathode material. It is also possible to fire the precursor to produce the oxide form, and then react the transition metal oxide and LiOH/Li2CO3 to afford the cathode material i.e., LiNi _x Mn _y Co _z 02.

Turning now to Figures 2 and 3, the block flow diagrams presented show the method of the invention using hydrobromic acid as the leachate. In Figures 2-3, dashed arrows indicate solid/liquid separation, with the downwardly directed arrow showing the solid phase or the filtrate that proceeds to the next step. The HBr leaching step of Figures 2 and 3 is now described in more detail. The leach solution consists of aqueous hydrobromic acid with HBr concentration varying in the range from 10 to ~48 wt.%, for example, from 15 to 48 wt.%, e.g. 15-35 wt . % . To perform the leaching step, the black mass and the hydrobromic acid are introduced into a leaching reactor and a slurry is formed. The solid can be first suspended in deionized water (about a 1:1 weight ratio) and then hydrobromic acid is gradually added to the slurry. A suitable solid/liquid ratio, namely, the proportion between the leachable solid electrode material and the aqueous hydrobromic acid leach solution added to the leaching reactor is usually from 10/90 to 30/70.

The cathode material dissolves gradually, usually with concomitant generation of elemental bromine. The dissolution time of the electrode material in the leach reactor increases with increasing solid/liquid ratio and decreases with increasing temperature and acid concentration. It is possible to achieve good leaching efficiencies for a variety of cathode materials during a reasonable time at room temperature but it is generally preferred to perform the leaching under heating, e.g., from 40 to 90 °C. For example, the temperature in the leaching reactor can be maintained at about 45 to 65 °C, i.e., around the boiling point of elemental bromine. At these temperatures, evolving bromine is removed more rapidly. For example, the hydrobromic acid leach solution could be first heated to about 35-45 °C, following which the slow addition of the black mass begins (or vice versa, acid is slowly added to the black mass/water slurry) . On a laboratory scale, the addition time of the black mass lasts not less than 10 minutes. On completion of the addition, the reaction mixture is heated to about 55-60 °C. Under these conditions, the leaching advances effectively and the formation of Br2 vapors is manageable. As pointed out earlier, the feedstock may be a mixture consisting of cathode and anode (carbon) . The latter remains as a solid residue in the leach solution. Cessation of the evolution of elemental bromine (with its characteristic red color) may indicate that the leaching reaction has reached completion or is about to end. But the progress of the leaching can also be determined by withdrawing samples from the leach solution to measure the concentration of the progressively dissolving metals and assess the leaching yield, for example, by inductively coupled plasma mass spectroscopy (ICP-MS) .

The PLS is optionally filtrated to remove insoluble matter (carbon, originated from the black mass) and is subjected to the post-leaching purification steps according to the invention, as previously described in detail in reference to Figure 1. These steps are also seen in Figures 2 and 3 and are briefly reiterated .

The first purification step consists of addition of Na2COs to increase the pH of the PLS to >1.5, e.g., >2, >2.5 (~3) , inducing the precipitation of Al, Fe and Cu (in part) as hydroxides/carbonates . The so-formed insoluble hydroxides/carbonates are separated from the PLS by filtration.

The second purification step consists of the electrowinning procedure. The filtrate collected after the first purification step is used as a catholyte stream circulated in an electrochemical flow cell to remove remnant copper from the PLS by electrodeposition onto the cathode surface.

Figures 2 and 3 also show the steps of "correcting" the composition of the purified PLS to adjust the molar ratio Ni:Mn:Co based on a predetermined target ratio; coprecipitation of the hydroxide precursor in a strongly alkaline environment

(NaOH/NFUOH) and its isolation by filtration.

The methods shown in the block flow diagrams in Figures 2 and 3 differ from one another with respect to lithium recovery. Lithium recovery can be achieved either by A) precipitation of lithium carbonate from the mother liquor obtained after coprecipitation and separation of the Ni _x Mn _y Co _z (OH) 2 or Ni _x Mn _y Co _z (CO3) precursor (see Figure 2) or B) by pre-leaching treatment of the black mass (see Figure 3) .

To precipitate L12CO3 from the mother liquor of the precursor as shown in Figure 2, carbonate source is added to the mother liquor, usually sodium carbonate. The pH of the mother liquor is sufficiently alkaline (~10- 11, «10.5) to enable precipitation of lithium carbonate. Another way is by bubbling CO2 into the alkaline mother liquor of the precursor to form an insoluble lithium carbonate precipitate. It is worthy to note that lithium carbonate exhibits an abnormal solubility curve (solubility of lithium carbonate in water decreases with increasing temperature) , hence precipitation may take place at a temperature up to 100 °C. The precipitate is usually collected by filtration, washed and dried to obtain lithium carbonate with an acceptable purity.

To extract lithium directly from the black mass as shown in Figure 3, alkaline pretreatment is done. The alkaline solution used in the preliminary treatment of the black mass to separate lithium is preferably alkali hydroxide (e.g., sodium hydroxide) , and/or ammonium hydroxide solution. The concentration of the alkali hydroxide in the solution may vary in the range from 1 to 45% by weight, e.g., from 10 to 20% by weight. The concentration of ammonium hydroxide in the solution may vary in the range from 5 to 25% by weight, e.g., from 10 to 25% by weight. Lithium is separable from the black mass under strongly alkaline conditions, e.g., pH > 12.0, preferably pH > 12.5, more preferably pH > 13.0 and even pH > 13.5. Lithium is then isolated from the alkaline solution as lithium carbonate in the manner previously described in reference to Figure 2. However, lithium is usually not fully removed from the black mass by the alkaline pretreatment; removal rate is usually up to 70% of the total amount of lithium.

Figures 2 and 3 also differ from one another with respect to HBr recovery. HBr can be recovered either A) after lithium separation from the mother liquor of the precursor (see Figure 2) , or B) just after the leaching step (see Figure 3) . Briefly, hydrobromic acid can be recovered by distillation under reduced pressure from two aqueous solutions that are formed in the process, after H2SO4 is added to the chosen solution.

According to first approach (shown in Figure 2) , HBr is recovered after isolation of all cathode metals (i.e., in the form of the NMC precursor and L12CO3) . At this stage of the process, the solution consists of sodium bromide dissolved in water. Sulfuric acid is added to the sodium bromide solution (excess 0.6 mole: 1 mole of bromide) followed by evaporation of HBr (the HBr can be reused in the leaching step) . The distillation residue in that case is slightly acidic sodium sulfate solution.

According to the second approach (shown in Figure 3) , by addition of 0.55 moles of sulfuric acid (98%) to 1 mole of HBr, the HBr was distilled from the leaching reactor, achieving high recovery rates. The distillation residue, in this case, is a slightly acidic sulfuric acid & precious metal sulfates solution, which is amenable to the downstream purification steps of the invention. The HBr may be reused as a feed stream to the leach reactor. More details on recovery of aqueous hydrobromic acid with acceptable purity by distillation under reduced pressure of HBr/H2SO4 aqueous mixtures is found in our earlier publication WO 2021/161316.

Accordingly, additional aspects of the invention include:

A process for the preparation of recycled cathode precursor, comprising the steps of: a) leaching electrode material (black mass) of lithium-ion battery using hydrobromic acid, to dissolve lithium, nickel, manganese, cobalt, aluminum, iron and copper to form pregnant leach solution (PLS) ; b) precipitating aluminum and iron in the PLS in the form of hydroxides and/or carbonates by addition of alkali carbonate to the PLS to create a mildly acidic pH, and separating the precipitate to form an essentially Al, Fe-free PLS; c) purification of the Al, Fe-free PLS from copper by electrowinning, to obtain a purified PLS; d) coprecipitating nickel, manganese and cobalt in a predetermined ratio at alkaline pH, and isolating Ni _x Mn _y Co _z (OH) 2 or Ni _x Mn _y Co _z (CO3) precursor from its mother liquor, with x+y+z=l; e) recovery of lithium from the mother liquor.

Also provided is a process for preparing a recycled cathode precursor of the formula Ni _x Mn _y Co _z (OH) 2 or Ni _x Mn _y Co _z (CO3) , with x+y+z=l, comprising the steps: raising the pH of an acidic pregnant leach solution (PLS) that contains nickel bromide, manganese bromide and cobalt bromide to the alkaline range to coprecipitate, in the presence of a complexing agent, said precursor; and separating the precursor from its mother liquor (e.g., wherein the precursor consists of spherical particles exhibiting flowerlike surface morphology) . Conditions are as described above. In the drawings :

Figure 1 is a block flow diagram showing the maj or steps of recovering precious metals from lithium-ion spent batteries by acid leaching, including the post- leaching puri fication steps according to the invention .

Figure 2 is a block flow diagram illustrating one of the variants of the process that consists of HBr leaching of black mass , puri fication of PLS from Al , Fe and Cu impurities and recovery of lithium after precursor coprecipitation .

Figure 3 is a block flow diagram illustrating one of the variants of the process that consists of alkaline pretreatment of black mass to recover lithium.

Figure 4 is an illustration of copper removal from PLS by electrowinning .

Figure 5 shows voltage ( left ordinate ) and copper concentration ( right ordinate ) versus time plots recorded during copper electrowinning from the PLS .

Figure 6 is a SEM image of the NisMn3Co2 ( OH) 2 particles obtained by coprecipitation from mixed transition metal bromide solution . Figure 7 is a SEM image of the NisMn3Co2 ( CO3 ) particles obtained by coprecipitation from mixed transition metal bromide solution .

Examples

Materials

Methods and Instrumentation

Inductively coupled plasma (ICP) was used to determine initial and final metal concentration; the ICP instrument was Agilent Technologies ICP-OES 5110.

The current and voltage data for the electrowinning process were recorded by computer software (EC Lab 11.01) that was connected to the potentiostat Biologic VSP with VMP 3B -10.

Atomic adsorption was analyzed by VARIAN AA 780 FS .

Preparation 1 A caustic pretreatment of the black mass

Black mass (100g) was slurried in NaOH 10% solution (2><900g) at 60 °C for 3-4h. The solid was separated by filtration, washed with water and dried. Another option is to perform the second slurry in a 12.5% solution of ammonium hydroxide.

Example 1

Removal of Al and Fe from PLS by addition of sodium carbonate

[PLS was prepared by the methods described in WO 2020/031178 and WO 2021/161316] . Anhydrous sodium carbonate was added to the PLS solution and iron and aluminum were removed by precipitation. The reaction of Na2COs is exothermic and its addition was controlled. The desired pH is 2.8-3.2 maximizing iron and copper precipitation and minimizing the formation of insoluble forms of nickel, manganese, cobalt and lithium. pH was maintained and controlled by the addition of sodium carbonate and HBr when necessary. After reaching the desired pH, the slurry was stirred for a few hours, then the precipitate was filtered and washed with water and the filtrate was used in the next step. Example 2

Removal of copper from Al and Fe-free PLS by electrowinning

The experimental set-up is shown in Figure 4 . An electrochemical flow cell , through which catholyte and anolyte streams can be circulated, was used . The electrodes positioned in the cell were made of a porous carbon felt ( Sigracell GFA3EA) with a lateral area of 3 x 3 . 5 cm ² separated by a porous poly-ethylene membrane ( Daramic ) to allow ion exchange between the cathodic/anodic compartments .

250 g of the filtrate collected in Example 1 was circulated by a peristaltic pump (WATSON MARLOW 323D) at a flow rate of 20 ml/min through the cathodic side o f an electrochemical flow cell ( catholyte ) . 250 gr of 32 % HBr solution ( anolyte ) was circulated by a second peristaltic pump (WATSON MARLOW 323D) at the same rate through the anodic side of the cell .

An electrical current of 0 . 1 A ( current density of 8 mA/ cm ² ) was generated by a potentiostat and supplied to the electrochemical cell . The current and voltage data were recorded by computer software that was connected to the potentiostat . During the operation of the cell , sample al iquots were taken periodically from the catholyte and anolyte solutions and analyzed by atomic adsorption (Vraian AA 780 FS ) to determine the changes in the concentration of copper concentration with the passage of time . Figure 5 shows voltage ( left ordinate ) and copper concentration ( right ordinate ) versus time plots . The results indicate a dramatic voltage that marks the end of copper deposition onto the cathode surface .

In addition, the initial and final concentrations of copper, manganese , cobalt , nickel and lithium were determined by ICR (Agilent Technologies ICP-OES 5110 ) . The results are tabulated in Table 1. The results show that the selectivity of the process towards copper removal is very high (despite the initial low concentration of copper as compared to the other metals) . The concentration of copper was reduced from 1100 ppm down to 31 ppm at the end of the experiment (99.7% removal rate) while the other metals cations (Li ⁺ , Mn ²⁺ , Ni ²⁺ and Co ²⁺ ) did not undergo electrodeposition and remained in the catholyte (the very small change observed was due to self-migration to the anodic side) .

Table 1

Example 3

Coprecipitation of NisMn3Co2 (OH) 2 (semi -batch process)

A 2L-reactor equipped with a mechanical stirrer was filled with IM aqueous NH4OH solution (700g) . The pH was adjusted to 10.5 by addition of 5M aqueous NaOH solution. The solution was maintained at 50-60 °C by circulating hot water through the jacket of the reactor under stirring at 800-1500 rpm.

A feed solution was prepared by dissolving NiBr2 ’3H2O, MnBr2 ’4H2O, and CoBr2 -PbO in water at concentrations of 5M, 3M and 2M, respectively. The bromide feed solution was added to the reactor by a peristaltic pump at a constant rate (~1 ml/min) . Concurrently with the feed of the bromides to the reactor, 5M aqueous NaOH solution and 10M aqueous NH4OH solution ( complexant ) were fed to the reactor by two separate streams over 8 . 5h at the same flow rate .

Precipitation occurred in the reactor . The suspension was maintained under stirring for an additional 16h under N2 atmosphere to promote particle si ze growth . The solid was separated by filtration, washed, and dried at 80 ° C for 12- 18h to obtain NisMn3Co2 ( OH) 2 precursor consisting of spherical particles with flower-like surface morphology as indicated by the SEM image appended as Figure 6 .

Example 4 Coprecipitation of NisMn3Co2 (OH) 2 (continuous-flow process)

A continuous stirred-tank reactor with external j acket ( CSTR1 ) was filled with IM aqueous NH4OH ( 700g ) which was basi fied with 5M NaOH to pH 10 . 5 . The solution was maintained at 50- 60 ° C by circulating hot water through the j acket of the reactor under stirring at 800- 1500 rpm .

A feed solution was prepared by dissolving NiBr2 ’ 3H2O, MnBr2 ’ 4H2O, and CoBr2 -H2O in water at concentrations of 5M, 3M and 2M, respectively . The bromide feed solution was supplied to CSTR1 by a peristaltic pump at a constant rate ( 1 ml/min) . Concurrently with the feed of the bromides to the reactor, 5M aqueous NaOH solution and 10M aqueous NH4OH solution ( complexant ) were fed to the reactor by two separate streams over 8 . 5h at the same flow rate .

A few minutes after the feed of the reactants to CSTR1 was initiated, the reaction mass started to flow from CSTR1 to a second stirred-tank reactor ( CSTR2 ) that was previously charged with 700 g of IM aqueous NH4OH (at a flow rate of 1 ml/min, using peristatic pump) . Precipitation of the product took place in CSTR2. The mixture at CSTR2 was allowed to stir for an extra 16h. In this period, particle growth occurs. Finally, the product was filtered, washed, and dried at 80°C for 12-18 h to obtain NisMn3Co2 (OH) 2 precursor consisting of spherical particles.

Example 5 Preparation of NisMn3Co2 (OH) 2 (continuous-flow process with seeding)

A continuous stirred-tank reactor with external jacket (CSTR1) was filled with IM aqueous NH4OH (700g) which was basified with 5M NaOH to pH 10.5. The solution was maintained at 50-60 °C by circulating hot water through the jacket of the reactor under stirring at 800-1500 rpm. Seeds of NisMn3Co2 (OH) 2 were added to CSTR1 at concentration of 0.1% w/w.

A feed solution was prepared by dissolving NiBr2 ’3H2O, MnBr2 ’4H2O, and CoBr2 -H2O in water at concentrations of 5M, 3M and 2M, respectively. The bromide feed solution was supplied to CSTR1 by a peristaltic pump at a constant rate (1 ml/min) . Concurrently with the feed of the bromides to the reactor, 5M aqueous NaOH solution and 10M aqueous NH4OH solution (complexant) were fed to the reactor by two separate streams over 8.5h at the same flow rate .

A few minutes after the feed of the reactants to CSTR1 was initiated, the reaction mass has started to flow from CSTR1 to a second stirred-tank reactor (CSTR2) that was previously charged with 700 g of IM NH4OH (at a flow rate of 1 ml/min, using peristatic pump) . The mixture at CSTR2 was allowed to stir for an extra 16h. In this period, particle growth occurs. Finally, the product was filtered, washed, and dried at 80°C for 12-18 h to obtain the NisMn3Co2 (OH) 2 precursor consisting of spherical particles.

Example 6 Preparation of NisMn3Co2 (CO3) (semi -batch process)

A 2L-reactor equipped with a mechanical stirrer was filled with 800g water. The pH was adjusted to 7.5-8 by addition of 2M Na2CO3/0.24M NH4OH solution. The solution was maintained at 40- 45°C by circulating hot water through the jacket of the reactor under stirring at 800-1500 rpm.

A feed solution was prepared by dissolving NiBr2 ’3H2O, MnBr2 ’4H2O, and CoBr2 -H2O in water at concentrations of 5M, 3M and 2M, respectively. The bromides feed solution was added to the reactor by a peristaltic pump at a constant rate (1 ml/min) . Concurrently with the feed of the bromide, the 2M Na2CO3/0.24M NH4OH solution was added to the reactor over 8.5h at the same rate.

Precipitation occurred in the reactor. The suspension was maintained under stirring for an additional 16h under N2 atmosphere to promote particle growth. The solid was separated by filtration, washed, and dried at 80 °C for 12-18h to obtain NisMn3Co2 (CO3) precursor; see SEM image appended as Figure 7.

Example 7

Lithium recovery from the mother liquor of NisMn3Co2 (OH) 2

A filtrate collected after the separation of the NisMn3Co2 (OH) 2 was stripped with nitrogen to remove ammonia followed by addition of NaOH. After bubbling of CO2 through the filtrate, a precipitate was formed. The precipitate was separated by filtration and dried to obtain solid lithium carbonate (L12CO3) .