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The most valuable metal for recycling in spent lithium-ion batteries is cobalt, not lithium. Metals such as lithium, nickel and manganese are simply by-products of recycled diamonds. The basic steps for the recovery of various lithium batteries are similar, including pretreatment (disassembly, sorting, etc.) and the recovery of drills and other metals. The pretreatment methods of various recycling technologies are basically the same, the difference lies in the different technical routes and methods of recycling cobalt and other metals.
Because lithium-ion batteries are composed of a variety of materials, they are fine assemblies. Due to its small size, large quantity and high dispersion of various materials, it is difficult to separate the cobalt-containing materials by mechanical methods, and only the cells of the battery can be treated as a whole. The Japanese scholar Kimura Shengzhi proposed the following method for recycling lithium-ion batteries: after recycling the waste battery, carry out discharge treatment, peel off the shell, and recover the metal material of the shell; mix the battery core with coke and limestone, and put it into the roasting furnace for reduction roasting; organic matter is burned and decomposed into carbon dioxide and other gases, lithium cobalt oxide is reduced to metal cobalt and lithium oxide, chlorine and phosphorus are fixed by sediment, aluminum is oxidized to slag, and most lithium oxide escapes as vapor, which is absorbed by water, metal copper, diamond, etc. form a carbon-containing alloy; the alloy formed by the lithium-ion battery after the above treatment will contain copper, cobalt, nickel and other metals. Further processing of this alloy can separate and extract higher-priced cobalt salts and nickel salts.
Sony Corporation and Sumitomo Metal Mining Corporation jointly developed a technology for recovering diamonds and other products from waste lithium-ion secondary batteries. The process is to first incinerate the battery to remove organic matter, then screen to remove iron and copper, heat the residual powder and dissolve it in acid, and use organic solvent to extract cobalt oxide, which can be used as a raw material for producing pigments and coatings.
The main components of the positive electrode material of the lithium ion secondary battery are Co2O3, NiO, Al2O3 and Al. Among them, NiO, Al2O3 and Al are easily soluble in medium and strong acids, while Co2O3 is only soluble in reducing dilute hydrochloric acid. The experimental results show that when the temperature is 80 ℃, the leaching effect of using dilute hydrochloric acid with a mass fraction of 20% as the leaching solution of the positive electrode material of lithium ion secondary battery is the best. It is reported that at a constant temperature of 80 ℃, the positive electrode material of the lithium ion secondary battery is added to 20% dilute hydrochloric acid, stirred continuously for more than 3 hours, and filtered to remove a very small amount of white insoluble residue; add an appropriate amount of ammonia water to the solution, adjust the pH value of the solution to 4, selectively deposit aluminum hydroxide, centrifugal sedimentation, liquid separation, and add an excessive amount of ammonia solution containing a certain amount of NH4Cl to the upper layer liquid; adjust the pH value of the solution to about 10 so that the metal ions and ammonia are fully complexed, and continuously feed pure oxygen into the solution for about 30 minutes; then, the solution was repeatedly passed through a weakly acidic cation exchange resin, and an ammonium sulfate solution with a concentration of 0.6 mol/L and a pH value of 10 was used as the eluent to selectively elute the nickel complex on the ion exchange resin. After repeated elution several times, the solution of sulfuric acid with a concentration of 2 mol/L was used as the eluent to elute the trivalent cobalt ammine complex. Finally, the cobalt complex was completely eluted with 5% H2SO4 solution, and the cation exchange resin was regenerated at the same time, and the two eluted collection solutions were adjusted to be alkaline, and add oxalate to recover cobalt, nickel and other metals in the eluent respectively. The process combines the complexation method with the ion exchange method, and realizes the separation and recovery of various metal elements in the positive electrode material of the lithium ion secondary battery. Among them, the recoveries of cobalt and nickel reached 84.9% and 89.1%, respectively. The process flow is simple, and it is a feasible recycling process.
According to reports, according to the characteristics of lithium-ion secondary battery waste, the waste lithium-ion secondary battery can be disassembled and sorted into plastic casings, copper-iron connectors, graphite negative electrodes and positive electrodes. The positive electrode waste adopts the alkaline leaching-acid-dissolving-purification-cobalt precipitation process to recover aluminum and cobalt from the positive electrode waste of lithium ion secondary batteries. Specifically, the cathode waste was first leached with 10% NaOH solution at 90 ℃, so that all cobalt remained in the alkali leaching residue, and the leaching rate of aluminum reached 94.84%. Aluminum hydroxide is recovered when the aluminum in the alkaline leaching solution is neutralized with H2SO4 to pH=7. The alkali leaching residue is leached in sulfuric acid and hydrogen peroxide system, and the leaching rate of the obtained cobalt reaches 99.30%. The pH value of the acid-dissolved solution was adjusted to 5.0 with NaOH and purified to remove impurities. The loss of the obtained cobalt was about 1.0%, and 87.81% of the aluminum in the solution was removed. The ammonium oxalate solution is added to the purified solution to precipitate cobalt, and the filter cake is dried and sieved to obtain the cobalt oxalate product (CoC2O4·2H2O). The cobalt deposition rate was 97.52%, and the recovery rate of cobalt in the whole process was 94.23%.
The recovery rate of cobalt in this process is 94.23% and that of aluminum is 94.89%. The product quality of cobalt oxalate meets the Q/GGH 01-89 standard, and the product quality of aluminum hydroxide meets the requirements of chemically pure reagents. The process flow is short, the equipment requirements are low, and the economic and social benefits are good, which is suitable for small and medium-sized enterprises.
According to reports, a 10mol/L industrial sulfuric acid solution was used as a leaching agent, which was placed in a 5L beaker with a waste lithium-ion battery, heated to 70 ℃, and leached for 1 h to dissolve all the reactants. The composition of the obtained solution is (g/L): Co 23.49; Ni 0.021; Li 1.62; Al 6.12; Cu 0.001; Fe 0.004. Neutralize the leaching solution with sodium carbonate, adjust the pH value to 2~3, heat it to 90℃, and stir with a blast to precipitate the iron and aluminum in the solution. The reaction is
At the same time, silicon can also be removed in the form of co-precipitation. The composition of the solution after hydrolysis is (g/L): Co 46.9; Ni 0.034; Li 2.62; Al 0.001; Cu 0.001; Fe 0.001. Then the solution obtained by removing impurities is directly electrodeposited, the current density is 235A/m2, the temperature of the electrolyte is 55~60℃, and the electrolytic anolyte is returned to the neutralization and impurity removal section to obtain electrolytic cobalt with a smooth surface. The process is simple and easy to deal with waste lithium batteries. The cobalt leaching rate can reach 100%, and the recovery rate is greater than 93%. The leaching solution can be directly electrolytically deposited cobalt after removing impurities by the hydrolysis method, and the process is simple. Spectral analysis of the obtained electrolytic cobalt shows that it meets the quality standard of 1A# electrolytic cobalt in GB 6517-86, and the current efficiency is 92.08%.
It has been reported that lithium cobalt oxide can be recovered from ultra-thin square spent lithium-ion batteries used in mobile phones by flotation. First, use a vertical high-speed rotary pulverizer to pulverize the waste lithium-ion battery for 30s, and sieve the pulverized product with a 10-mesh sieve. The material on the sieve is sorted by a pneumatic shaker, and the resin material and metal material (aluminum foil, copper foil, aluminum metal shell fragments, etc.) used as separators are separated. The material under the sieve is sieved with a 65-mesh vibrating sieve to separate out metal materials (aluminum foil, copper foil, and fragments of aluminum metal shell) and mixed powder (mixed powder containing lithium cobalt oxide and graphite). Then, the isolated black mixed powder was heat-treated at 773 K for 2 h to modify the surface of lithium cobalt oxide particles and graphite. Then, the lithium cobalt oxide and graphite are separated by flotation.
If the input amount of the lithium ion secondary battery sample is 100%, the equilibrium flow of each material is expressed as a percentage, and the yield of the mixed powder containing lithium cobalt oxide and graphite is 46.1%. After heat treatment and flotation operations, the recovered lithium cobalt oxide product was obtained in a yield of 26.8% relative to the spent battery feedstock. The grade of the lithium cobalt oxide obtained at this time was 93.0%, so the lithium cobalt oxide was 24.9% (26.8×93.0%). According to reports, each lithium-ion secondary battery with lithium cobalt oxide (LiCoO2, relative molecular mass 97.9) as the positive electrode active material usually contains 20% to 27% of lithium cobalt oxide. It can be calculated that each lithium-ion secondary battery contains about 1.4% to 1.9% lithium. Therefore, the metal of the recovered metal lithium (the relative atomic mass of Li is 69) is: the metal amount of lithium cobalt oxide × lithium atomic weight / molecular weight of lithium cobalt oxide = 24.9% × 69/97.9 = 17.5%.
Assuming that the lithium content in the lithium-ion secondary battery is 1.9%, the recovery rate of lithium per waste battery is about 92.1% (100%×1.75/1.9). The same can be done for cobalt (the relative atomic mass of Co is 58.9). According to the cobalt content of 12%~16% in each lithium-ion battery, the recovery ratio of cobalt recovered in this flotation test can be calculated.
Lithium cobalt oxide metal weight × cobalt atomic weight / lithium cobalt oxide relative molecular mass = 24.9% × 58.9/97.9 = 14.98%. Lithium-ion secondary batteries contain 12% to 16% of cobalt, and the recovery rate of cobalt can also be calculated to be more than 90% (100% × 14.98/16). The above results show that the flotation method is an effective method for comprehensive utilization of waste lithium-ion secondary batteries, and can recover the rare metals lithium and cobalt respectively from waste lithium-ion secondary batteries with a high recovery rate.
The conditions of this flotation test are: the amount of collector kerosene is 0.2kg/t, the amount of foaming agent MIBC is 0.14kg/t, the slurry solid concentration is 10%, and the flotation time is 10min, which can effectively separate lithium cobalt oxide-graphite mixed powder, the grade of lithium cobalt oxide in the obtained lithium cobalt oxide product is over 93%, and the recovery rate is over 92%.
In 2003, Wuhan University of Technology invented a new method of separating and recovering lithium from waste lithium-ion batteries using У-MnO2 ion sieves, which was granted an invention patent by the State Intellectual Property Office that year. The procedure for separating and recovering lithium from spent lithium-ion batteries with an ion sieve is as follows.
1. Static adsorption separation - elution method
Fully discharge the waste battery, remove the casing, soak the battery core in 4.0 mol/L excess hydrochloric acid at 70℃, and keep stirring to fully dissolve it. Adjust the pH value to about 12 with 2mol/L sodium hydroxide solution, then filter to remove the precipitate and insoluble matter, put the filtrate into a container with excess У-MnO2 ion sieve solid powder, and keep stirring to make the ion sieve appear suspended state. Measure the lithium ion concentration in the solution at any time until the lithium ion concentration in the solution is less than 1 mg/L. Filter and separate the system, wash the residual solution on the surface of the ion sieve, soak it in an excess of 1.0 mol/L hydrochloric acid, and keep stirring to keep it in a suspended state. Equilibrium is reached when the concentration of lithium ions in the eluent no longer changes. It is filtered and separated again, and the obtained filtrate is the solution containing lithium ions. Evaporate and crystallize to obtain lithium chloride solid.
2. Dynamic adsorption separation - elution method
Adsorption-elution takes place in an exchange column. The exchange column is made of glass or plastic, with a diameter of 1.2 cm and a capacity of 50 mL. The bubbles are removed with distilled water in advance. Fully discharge the waste battery, remove the outer casing, soak the remaining part in 3.0 mol/L excess hydrochloric acid at 80℃, and continuously stir to dissolve it. The pH value of the system was adjusted to about 11 with 3.0 mol/L sodium hydroxide solution, and the precipitate and insoluble matter were separated by filtration to obtain a solution containing lithium ions. The solution was transferred to an exchange column with a layer of glass sand core at the bottom and filled with excess У-MnO2 ion sieve, and the flow rate was controlled to be 1~5mL/min. When the ion sieve is saturated with adsorption, the residual liquid in the column is washed with distilled water, and then 0.5mol/L hydrochloric acid is added from the upper end of the column for washing until the pH value of the effluent is the same as the pH value of 0.5mol/L hydrochloric acid. The effluent at this time is the desired solution containing lithium ions. Add precipitant Na2CO3 to this solution, heat and concentrate to obtain Li2CO3 precipitation, filter, separate and dry to obtain solid Li2CO3.
According to reports, the cobalt and lithium in the waste lithium-ion secondary battery can be recovered by the full wet process, and the cobalt and lithium can be removed and separated by the solvent extraction method, so that the cobalt recovery rate is as high as 99%. The main elements cobalt, aluminum and lithium in the waste battery do not produce secondary pollution. In order to avoid the excessive load of aluminum removal in subsequent extraction, the cathode waste was first dissolved with 10% NaOH, and the aluminum foil as the current collector was put into the solution in the form of NaAlO2. LiCoO2 is insoluble in alkali, and will all enter into alkali leaching residue, while NaAlO2 will all enter into alkali leaching solution. The NaAlO2 in the alkaline leaching solution is neutralized with sulfuric acid to precipitate aluminum in the form of aluminum hydroxide. According to reports, the aluminum hydroxide product obtained by precipitation can reach the standard of chemically pure reagent. The alkali leaching residue was acid leached by H2SO4+H2O2 system. The concentration of sulfuric acid was 2.0 mol/L, the amount of hydrogen peroxide was 3 mL/g per gram of raw material, the leaching temperature was 80 ℃, the leaching time was 90 min, and the solid-liquid ratio was about 1/8 to 1/10. The reaction that takes place is
2LiCoO2+3H2SO4+H2O2=2CoSO4+O2 +Li2SO4+4H2O
The filtrate after acid leaching also contains impurities such as Fe2+, Ca2+, Mn2+, Zn2+ and some Al3+. When extracting cobalt and lithium with P507 (2,2-diethylhexyl phosphonic acid monoester), calcium, manganese and aluminum will be simultaneously extracted under the pH conditions of the extraction cobalt operation. Therefore, use 25% P204 (D2-EHPA), the diluent is industrial kerosene, the saponification rate is 75%, the extraction equilibrium pH value is 2.5~3.0, the ratio is 1, and the secondary countercurrent extraction is used to remove impurities, so that impurities such as Al, Fe, Zn, Mn, Ca enter the organic phase, and Co, Li, Ni, etc. remain in the water phase. Then, the solution after impurity removal and purification is used to separate cobalt and lithium with the extraction solution of 1.0mol/L P507, kerosene as diluent, 75% saponification rate, extraction equilibrium pH value of 5.5~6.0, and ratio of 2. A small amount of lithium entering the cobalt-rich organic phase can be washed and removed with CoSO4+H2SO4 solution first, and then back-extracted with 2mol/L H2SO4, the ratio of back-extraction is 3~4, and the concentration of cobalt in the back-extraction solution is about 110g/L, The pH is about 1.
The high-purity CoSO4 solution obtained after back-extraction can be directly used in the production of battery raw materials or electroplating. The P507 raffinate used to separate cobalt and lithium is precipitated with saturated Na2CO3 solution, and the selected precipitation temperature is greater than 95℃ to obtain Li2CO3 precipitation. After the filter cake was washed twice with hot water, the crystallization mother liquor and SO42- were removed, and then dried.
The recovery rate of cobalt in this process reaches more than 99%, and the impurity content in the product cobalt sulfate is: Al 3.5mg/L; Fe 0.5mg/L; Zn 0.6mg/L; Mn 2.3mg/L; Ca<0.1mg/L. Lithium carbonate can meet the requirements of zero-grade products, and the primary lithium deposition rate is 76.5%.