Method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder

Abstract

The invention provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder, which comprises the following steps: (1) mixing waste ternary lithium battery powder and graphite to obtain a mixture, and carrying out reduction reaction on the mixture to obtain a material after reduction reaction; wherein the mass of the graphite in the mixture is 2-10 times of the theoretical mass of the graphite required for reducing the waste ternary lithium battery powder; (2) leaching the material after the reduction reaction and carrying out solid-liquid separation to obtain a Li-containing alkaline solution; and (3) carrying out evaporative crystallization on the Li-containing alkaline solution to obtain lithium hydroxide monohydrate. According to the method, graphite originally existing in the waste ternary lithium battery powder is adopted as a reducing agent, the effect of treating waste with waste is achieved, the addition amount of the graphite is increased, the graphite plays a role in reducing and preventing crystal grains from growing through a heat absorbent and an isolating agent at the same time, lithium can be leached with water under the condition of a smaller liquid-solid ratio, and the application prospect is wide.

Description

Technical Field

[0001] The invention relates to the technical field of separation and recovery, and in particular to a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. Background Art

[0002] Among the single materials of power lithium batteries, the positive electrode materials, electrolytes, aluminum alloy shells, diaphragms and negative electrode materials account for the largest cost, among which the cost of positive electrode materials for ternary batteries accounts for more than 40%. With the rise in the prices of materials such as cobalt, nickel, manganese and lithium in recent years, the proportion of positive electrode materials for ternary batteries in the cost of battery cells in the future will rise sharply. Waste batteries contain a variety of recyclable metal resources, including metals such as lithium, nickel, cobalt, manganese, aluminum, copper in positive electrode materials and graphite in negative electrode materials. The resources are rich in variety and abundance, and have extremely high recycling value. Among them, the metal elements such as nickel, cobalt, lithium and manganese in the positive electrode materials are recovered by physical and chemical means after the battery is disassembled. The processing process includes two parts: pretreatment and metal recovery. Among them, there are many technical paths for metal recovery supply and demand, and the process is relatively mature.

[0003] At present, in the process of selectively separating metallic lithium from ternary positive electrode materials for lithium batteries by pyrometallurgy, graphite is selected as a reducing agent to convert the ternary materials into lithium carbonate and a mixture of nickel, cobalt and manganese metals and their oxides at a temperature of about 700°C. The selective lithium extraction effect is significant, and the resulting lithium solution can be directly made into battery-grade lithium carbonate after impurities are removed (such as CN201710875966.3, a method for recovering lithium, nickel, cobalt and manganese from waste ternary positive electrode materials).

[0004] However, the medium-temperature pyrometallurgical lithium extraction process using graphite as a reducing agent has the following problems:

[0005] (1) The temperature is low and the reduction is not complete, which easily causes lithium coating and makes subsequent leaching difficult.

[0006] (2) The solubility of the reduced lithium carbonate is low, and a large liquid-to-solid ratio (the leaching liquid-to-solid ratio reaches 20-100 mL / g) water leaching is required, or a bicarbonate leaching process is used. If water leaching is used, the concentration of lithium in the leaching solution is only about 2 g / L, and a large amount of energy is consumed to evaporate the excess water, and the lithium recovery rate can only reach about 90%.

[0007] In summary, it is necessary to improve the current process of using graphite as a reducing agent to recover lithium from waste ternary lithium battery powder. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. By adding 2 to 10 times the theoretical amount of graphite, the reduction effect can be improved. The graphite also absorbs heat during the reduction process and acts as an isolation agent to isolate other elements such as lithium and nickel. Therefore, water can be used to achieve efficient recovery of lithium at a low liquid-to-solid ratio, and a high-purity lithium hydroxide product can be obtained through a post-process.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder, the method comprising the following steps:

[0011] (1) mixing waste ternary lithium battery powder and graphite to obtain a mixture, and subjecting the mixture to a reduction reaction to obtain a reduced reaction material; wherein the mass of the graphite in the mixture is 2 to 10 times the theoretical mass of graphite required to reduce the waste ternary lithium battery powder;

[0012] (2) leaching the material after the reduction reaction and performing solid-liquid separation to obtain a Li-containing alkaline solution;

[0013] (3) The alkaline solution containing Li is evaporated and crystallized to obtain lithium hydroxide monohydrate.

[0014] It is worth noting that the existing selective separation lithium battery ternary positive electrode materials have the problems of lithium carbonate being coated, low solubility, low lithium recovery rate, and high energy consumption caused by evaporation and crystallization of a large amount of water. The present invention adds 2 to 10 times the theoretical mass of graphite required, which has the following three advantages:

[0015] (1) The amount of graphite used as a reducing agent is larger than the theoretical amount, and the excess graphite is more likely to form a CO atmosphere during the reduction process, resulting in a better reduction effect. Compared with the case where only the theoretical amount of graphite is added, the reduction is more thorough, and it is beneficial to promote the decomposition of lithium carbonate into lithium oxide, thereby achieving low liquid-to-solid ratio water leaching of lithium and reducing the evaporation energy consumption of lithium extraction;

[0016] (2) In addition to the graphite used for reduction, there is at least 1 times more excess graphite, which can avoid the situation of local over-sintering caused by the heat of reduction and alloying during the reduction process, thus alleviating the problem of subsequent leaching difficulties caused by over-sintering;

[0017] (3) The addition of excess graphite can prevent the reduction products formed by elements such as Ni, Mn and Co from being united together, that is, graphite can act as an isolating agent, thereby alleviating the situation of Li being wrapped in the reduction products. The isolation effect of graphite greatly reduces the difficulty of subsequent leaching and improves the lithium leaching rate.

[0018] Specifically, the mass of graphite in the mixture is 2 to 10 times the theoretical mass of graphite required to reduce waste ternary lithium battery powder, for example, it can be 2 times, 2.9 times, 3.8 times, 4.7 times, 5.6 times, 6.5 times, 7.4 times, 8.3 times, 9.2 times or 10 times, etc.

[0019] Preferably, the theoretical mass of the graphite in step (1) is determined according to the following reduction reaction: LiNi x Co y Mn 1-x-y O2+(0.5+x+y)C=0.5Li2O+xNi+yCo+(1-xy)MnO+(0.5+x+y)CO, wherein the value range of x is 0.33-0.80, and the value range of y is 0.10-0.33.

[0020] wherein x may be, for example, 0.33, 0.39, 0.44, 0.49, 0.54, 0.6, 0.65, 0.7, 0.75 or 0.80, etc.; and y may be, for example, 0.10, 0.13, 0.16, 0.18, 0.21, 0.23, 0.26, 0.28, 0.31 or 0.33, etc.

[0021] Preferably, the temperature of the reduction reaction is 900-1400°C, for example, it can be 900°C, 956°C, 1012°C, 1067°C, 1123°C, 1178°C, 1234°C, 1289°C, 1345°C or 1400°C.

[0022] The preferred reduction reaction temperature of the present invention is within the above range, which has a better reduction effect.

[0023] Preferably, the atmosphere for the reduction reaction in step (1) is a non-oxidizing atmosphere or a vacuum.

[0024] Preferably, the non-oxidizing atmosphere comprises any one of nitrogen, argon, helium or carbon monoxide or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of nitrogen and argon, a combination of helium and argon, a combination of nitrogen and helium, a combination of carbon monoxide and argon, and a combination of nitrogen and carbon monoxide.

[0025] Preferably, the reduction reaction time is 0.1 to 24 h, for example, it can be 0.1 h, 1 h, 4 h, 7 h, 9 h, 12 h, 14 h, 17 h, 19 h, 22 h or 24 h.

[0026] Preferably, the waste ternary lithium battery powder in step (1) is one of type 111, type 523, type 622 or type 811, or a combination of at least two of them, wherein typical but non-limiting combinations are a combination of type 111 and type 523, a combination of type 622 and type 523, a combination of type 111 and type 622, and a combination of type 811 and type 523.

[0027] Preferably, the material after the reduction reaction in step (1) includes nickel-cobalt-manganese particles.

[0028] Preferably, the occurrence form of nickel, cobalt and manganese in the nickel-cobalt-manganese-containing particles includes one or a combination of at least two of metallic nickel, metallic cobalt, nickel-cobalt alloy or manganese oxide, wherein typical but non-limiting combinations are a combination of metallic nickel and metallic cobalt, a combination of nickel-cobalt alloy and metallic cobalt, and a combination of metallic nickel and manganese oxide.

[0029] Preferably, the particle size of the nickel and cobalt metal particles in the material after the reduction reaction does not exceed 30 μm, for example, it can be 10 μm, 13 μm, 15 μm, 17 μm, 19 μm, 22 μm, 24 μm, 26 μm, 28 μm or 30 μm, etc.

[0030] Preferably, the leaching agent used in step (2) comprises water or LiOH solution.

[0031] Preferably, the liquid-to-solid ratio of the leaching is 1 to 100:1 mL / g, for example, it can be 1:1 mL / g, 2:1 mL / g, 3:1 mL / g, 4:1 mL / g, 5:1 mL / g, 6:1 mL / g, 7:1 mL / g, 8:1 mL / g, 9:1 mL / g, 10:1 mL / g, 12:1 mL / g, 23:1 mL / g, 34:1 mL / g, 45:1 mL / g, 56:1 mL / g, 67:1 mL / g, 78:1 mL / g, 89:1 mL / g or 100:1 mL / g, etc., preferably 1 to 10:1 mL / g.

[0032] The preferred leaching liquid-to-solid ratio of the present invention is low, which can greatly reduce the leaching agent used for leaching, and water can be directly used for leaching.

[0033] Preferably, the leaching temperature is 5-100°C, for example, it can be 5°C, 16°C, 27°C, 37°C, 48°C, 58°C, 69°C, 79°C, 90°C or 100°C.

[0034] Preferably, the leaching time is 0.1 to 24 h, for example, it can be 0.1 h, 1 h, 1.5 h, 1.6 h, 1.8 h, 2.0 h, 2.2 h, 2.3 h, 2.5 h, 3 h, 3.5 h, 4 h, 7 h, 9 h, 12 h, 14 h, 17 h, 19 h, 22 h or 24 h, etc., preferably 0.1 to 4 h.

[0035] Preferably, the leaching rotation speed is 200-1200 rpm, for example, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 600 rpm, 800 rpm or 1200 rpm.

[0036] Preferably, when the leaching medium is a LiOH solution, the concentration of LiOH in the LiOH solution does not exceed 18 g / L, for example, it can be 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L or 18 g / L, etc.

[0037] Preferably, the solid-liquid separation in step (2) also produces a lithium-dissolved residue.

[0038] Preferably, the residual lithium content in the lithium-dissolving residue is ≤0.3wt%, for example, it may be 0.01wt%, 0.02wt%, 0.1wt%, 0.15wt%, 0.18wt%, 0.2wt%, 0.23wt%, 0.25wt% or 0.3wt%.

[0039] Preferably, the lithium-dissolving residue is acid-dissolved with a sulfuric acid solution and subjected to solid-liquid separation to obtain a nickel-cobalt-manganese enriched solution and graphite.

[0040] Preferably, the nickel-cobalt-manganese enriched solution is used as the raw material for nickel-cobalt-manganese extraction.

[0041] Preferably, the graphite is returned to step (1) after drying and used as a reducing agent.

[0042] Preferably, the total amount of sulfuric acid in the sulfuric acid solution is 1.2 to 1.5 times the theoretical amount of sulfuric acid required, for example, it can be 1.2 times, 1.24 times, 1.27 times, 1.3 times, 1.34 times, 1.37 times, 1.4 times, 1.44 times, 1.47 times or 1.5 times, etc. The calculation method of the theoretical amount of sulfuric acid required is the amount of sulfuric acid required to convert nickel, cobalt and manganese in the lithium-dissolving residue into NiSO4, CoSO4 and MnSO4 respectively.

[0043] Preferably, the concentration of sulfuric acid in the sulfuric acid solution is 1-8 mol / L, for example, it can be 1 mol / L, 1.8 mol / L, 2.6 mol / L, 3.4 mol / L, 4.2 mol / L, 4.9 mol / L, 5.7 mol / L, 6.5 mol / L, 7.3 mol / L or 8 mol / L.

[0044] Preferably, the liquid-to-solid ratio of the acid solution is 2 to 100 mL / g, for example, 2 mL / g, 13 mL / g, 24 mL / g, 35 mL / g, 46 mL / g, 57 mL / g, 68 mL / g, 79 mL / g, 90 mL / g or 100 mL / g.

[0045] Preferably, the acid dissolution temperature is 30-100°C, for example, it can be 30°C, 38°C, 46°C, 54°C, 62°C, 69°C, 77°C, 85°C, 93°C or 100°C.

[0046] Preferably, the acid dissolution time is 0.5 to 24 h, for example, it can be 0.5 h, 1 h, 4 h, 7 h, 9 h, 12 h, 14 h, 17 h, 19 h, 22 h or 24 h.

[0047] Preferably, the pH value of the nickel-cobalt-manganese enriched solution obtained by acid dissolution is 0-2, for example, it can be 0, 0.3, 0.5, 0.7, 0.9, 1.2, 1.4, 1.6, 1.8 or 2.

[0048] Preferably, before the evaporation and crystallization in step (3), a calcium source is first added to carry out a conversion reaction to convert Li2CO3 in the Li-containing alkaline solution into LiOH.

[0049] Preferably, the molar amount of Ca in the calcium source is equal to the molar amount of CO3 in the Li-containing alkaline solution. 2- The molar ratio is 0.8 to 1:1, for example, 0.8:1, 0.82:1, 0.83:1, 0.84:1, 0.85:1, 0.86:1, 0.87:1, 0.88:1, 0.89:1, 0.9:1, 0.92:1, 0.95:1, 0.98 or 1:1, etc.

[0050] Preferably, the temperature of the conversion reaction is 10-100°C, for example, it can be 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C.

[0051] Preferably, the conversion reaction time is 0.5 to 12 h, for example, 0.5 h, 1 h, 4 h, 7 h, 9 h or 12 h.

[0052] Preferably, the conversion reaction is followed by solid-liquid separation to obtain a lithium-containing liquid phase.

[0053] Preferably, the calcium source is calcium hydroxide.

[0054] Preferably, the evaporative crystallization is carried out in a protective atmosphere.

[0055] Preferably, the protective atmosphere is any one of argon, nitrogen, oxygen or air depleted of CO2, or a combination of at least two of them, wherein typical but non-limiting combinations are a combination of argon and nitrogen, a combination of oxygen and nitrogen, a combination of argon and oxygen, and a combination of air depleted of CO2 and nitrogen.

[0056] Preferably, the purity of the lithium hydroxide monohydrate is ≥98.8wt%, for example, it may be 99.0wt%, 99.1wt%, 99.2wt%, 99.3wt%, 99.4wt%, 99.5wt%, 99.6wt%, 99.7wt% or 99.8wt%, etc.

[0057] Preferably, when the purity of the lithium hydroxide monohydrate obtained by the evaporative crystallization is less than 99wt%, the lithium hydroxide monohydrate is dissolved in water and then recrystallized, and the recrystallization mother liquor is returned to step (2) to be used for preparing the leaching agent of the material after the reduction reaction.

[0058] The present invention has no special limitation on the solid-liquid separation in the above process. Any device and method for solid-liquid separation known to those skilled in the art can be used, and can also be adjusted according to the actual process, such as filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0059] As a preferred technical solution of the present invention, the method comprises:

[0060] (1) Mixing waste ternary lithium battery powder (type 111, type 523, type 622 or type 811) and graphite to obtain a mixture, and subjecting the mixture to a reduction reaction at 900 to 1400° C. in a non-oxidizing atmosphere or in a vacuum for 0.1 to 24 hours to obtain a reduced reaction material; wherein the mass of the graphite in the mixture is 2 to 10 times the theoretical mass of graphite required to reduce the waste ternary lithium battery powder, and the theoretical mass of the graphite is determined according to the following reduction reaction:

[0061] LiNi x Co y Mn 1-x-y O2+(0.5+x+y)C=0.5Li2O+xNi+yCo+(1-xy)MnO+(0.5+x+y)CO;

[0062] (2) leaching the reduction reaction material at 5 to 100° C. with water or a LiOH solution having a concentration not exceeding 10 g / L according to a liquid-to-solid ratio of 1 to 10:1 mL / g for 0.1 to 4 h, and performing solid-liquid separation to obtain a Li-containing alkaline solution and a lithium-dissolved residue;

[0063] (3) adding calcium hydroxide to the alkaline solution containing Li to convert Li2CO3 in the alkaline solution containing Li into LiOH, and then evaporating and crystallizing in a protective atmosphere (argon, nitrogen, oxygen or air removed from CO2) to obtain lithium hydroxide monohydrate;

[0064] According to the liquid-solid ratio of 2-100 mL / g, the lithium-dissolving residue is acid-dissolved with a sulfuric acid solution with a concentration of 1-8 mol / L at 30-100° C. for 0.5-24 h, and solid-liquid separation is performed to obtain a nickel-cobalt-manganese enriched solution with a pH value of 0-2 and graphite; wherein the total amount of sulfuric acid in the sulfuric acid solution is 1.2-1.5 times the theoretical amount of sulfuric acid required, and the theoretical amount of sulfuric acid required is calculated by the amount of sulfuric acid required to convert the nickel, cobalt and manganese in the lithium-dissolving residue into NiSO4, CoSO4 and MnSO4 respectively; the nickel-cobalt-manganese enriched solution is used as a raw material for nickel-cobalt-manganese extraction; and the graphite is returned to step (1) after drying and used as a reducing agent.

[0065] Compared with the prior art, the present invention has at least the following beneficial effects:

[0066] (1) The method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder provided by the present invention can solve the problems of lithium carbonate coating, poor water solubility of lithium carbonate, low lithium recovery rate, and high energy consumption of evaporation and crystallization existing in the existing medium-temperature reduction lithium extraction;

[0067] (2) The method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder provided by the present invention uses graphite carried by the lithium battery powder itself as a reducing agent, and the amount of graphite is deliberately 2 to 10 times the theoretical mass, which can not only provide a better CO atmosphere and a better reduction effect, but also play a role in spacing metals and absorbing heat, and can alleviate the problem of subsequent leaching difficulties caused by excessive sintering and reduction product wrapping, thereby improving the lithium leaching rate;

[0068] (3) The method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder provided by the present invention has the reduction products of nickel-cobalt metal, manganese oxide and lithium oxide, the reduction is thorough, the recovery rate of lithium oxide is high, and lithium oxide is very easy to react with water for reduction, and can be completely leached in a short time at a small liquid-to-solid ratio. The lithium concentration of the leachate is high, and the energy consumption of evaporation and crystallization is reduced; specifically, under preferred conditions, it can be achieved that the lithium leaching rate reaches 97.2% or more within 4 hours using water with a liquid-to-solid ratio of only 10:1 mL / g, the cobalt leaching rate reaches 99.2% or more, the nickel leaching rate reaches 98.9% or more, the manganese leaching rate reaches 99.5% or more, the recovery rate of graphite reaches 99.2%, and the purity of lithium hydroxide monohydrate is as high as 98.6wt% or more;

[0069] (4) The method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder provided by the present invention directly recovers lithium hydroxide monohydrate from the water leaching solution by evaporation and crystallization. The economic value is higher than that of recovering lithium carbonate with the same lithium content and the process flow is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a process flow chart of a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder in a specific embodiment of the present invention.

[0071] Figure 2 It is the phase equilibrium diagram of the ternary battery during the reduction reaction in Example 1 of the present invention.

[0072] Figure 3 This is a SEM image of lithium hydroxide monohydrate obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0073] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0074] As a specific embodiment of the present invention, a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder is provided. Figure 1 , the method comprising:

[0075] (1) Mixing waste ternary lithium battery powder (type 111, type 523, type 622 or type 811) and graphite to obtain a mixture, and subjecting the mixture to a reduction reaction at 900 to 1400° C. in a non-oxidizing atmosphere or in a vacuum for 0.1 to 24 hours to obtain a reduced reaction material; wherein the mass of the graphite in the mixture is 2 to 10 times the theoretical mass of the graphite required to reduce the waste ternary lithium battery powder, and the theoretical mass of the graphite is determined according to the following reduction reaction: LiNi x Co y Mn 1-x-y O2+(0.5+x+y)C=0.5Li2O+xNi+yCo+(1-xy)MnO+(0.5+x+y)CO, where x ranges from 0.33 to 0.80 and y ranges from 0.10 to 0.33;

[0076] (2) leaching the reduction reaction material at 5 to 100° C. with water or a LiOH solution having a concentration not exceeding 10 g / L according to a liquid-to-solid ratio of 1 to 10:1 mL / g for 0.1 to 4 h, and performing solid-liquid separation to obtain a Li-containing alkaline solution and a lithium-dissolved residue;

[0077] (3) adding calcium hydroxide to the alkaline solution containing Li to convert Li2CO3 in the alkaline solution containing Li into LiOH, and then evaporating and crystallizing in a protective atmosphere (argon, nitrogen, oxygen or air removed from CO2) to obtain lithium hydroxide monohydrate;

[0078] According to the liquid-solid ratio of 2-100 mL / g, the lithium-dissolving residue is acid-dissolved with a sulfuric acid solution with a concentration of 1-8 mol / L at 30-100° C. for 0.5-24 h, and solid-liquid separation is performed to obtain a nickel-cobalt-manganese enriched solution with a pH value of 0-2 and graphite; wherein the total amount of sulfuric acid in the sulfuric acid solution is 1.2-1.5 times the theoretical amount of sulfuric acid required, and the theoretical amount of sulfuric acid required is calculated by the amount of sulfuric acid required to convert the nickel, cobalt and manganese in the lithium-dissolving residue into NiSO4, CoSO4 and MnSO4 respectively; the nickel-cobalt-manganese enriched solution is used as a raw material for nickel-cobalt-manganese extraction; and the graphite is returned to step (1) after drying and used as a reducing agent.

[0079] Example 1

[0080] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder, the method comprising:

[0081] (1) Mixing waste ternary lithium battery powder (type 111) and graphite to obtain a mixture, and subjecting the mixture to a reduction reaction at 1000° C. in a non-oxidizing atmosphere (nitrogen) for 2 h to obtain a reduced reaction material; wherein the mass of graphite in the mixture is 3.5 times the theoretical mass of graphite required to reduce the waste ternary lithium battery powder, and the theoretical mass of the graphite is determined according to the following reduction reaction: LiNi x Co y Mn 1-x-y O2+(0.5+x+y)C=0.5Li2O+xNi+yCo+(1-xy)MnO+(0.5+x+y)CO, i.e., graphite reduces nickel, cobalt and manganese by carbon to 3.5 times the theoretical molar amount of lithium oxide, metallic nickel, metallic cobalt and manganese monoxide;

[0082] (2) leaching the reduction reaction material with water at 400 rpm and 25° C. at a liquid-to-solid ratio of 5:1 mL / g for 1 h, and filtering to obtain a Li-containing alkaline solution and a lithium-dissolved residue;

[0083] (3) adding calcium hydroxide to the alkaline solution containing Li to convert Li2CO3 in the alkaline solution containing Li into LiOH, wherein the molar amount of calcium in the calcium source is the molar amount of Ca and CO3 in the alkaline solution containing Li. 2- The molar ratio is 1:1, and the conversion reaction is carried out at 300 rpm for 1 hour in a water bath at 80°C. The lithium-containing liquid phase after precipitation and filtration of calcium carbonate is evaporated and crystallized in a protective atmosphere (nitrogen) to obtain lithium hydroxide monohydrate;

[0084] According to the liquid-to-solid ratio of 10mL / g, the lithium-dissolving residue is acid-dissolved with a sulfuric acid solution with a concentration of 2mol / L at 90°C for 2h, and filtered to obtain a nickel-cobalt-manganese enriched solution with a pH value of 1.6 and graphite; wherein the total amount of sulfuric acid in the sulfuric acid solution is 1.4 times the theoretical amount of sulfuric acid required, and the theoretical amount of sulfuric acid required is calculated by the amount of sulfuric acid required to convert the nickel, cobalt and manganese in the lithium-dissolving residue into NiSO4, CoSO4 and MnSO4 respectively; the nickel-cobalt-manganese enriched solution is used as a raw material for nickel-cobalt-manganese extraction; and the graphite is returned to step (1) after drying and used as a reducing agent.

[0085] The phase equilibrium diagram of the ternary battery during the reduction reaction in step (1) of this embodiment is as follows: Figure 2 As shown, from Figure 2 It can be seen that under the temperature conditions adopted in this embodiment, the conversion of lithium carbonate into lithium oxide can be achieved, which is beneficial to the subsequent leaching.

[0086] The SEM image of lithium hydroxide monohydrate obtained in this example is as follows Figure 3 As shown, from Figure 3 It can be seen that the crystallized lithium hydroxide monohydrate is in the shape of a rod.

[0087] Example 2

[0088] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder, the method comprising:

[0089] (1) Mixing waste ternary lithium battery powder (type 523) and graphite to obtain a mixture, and subjecting the mixture to a reduction reaction at 1100° C. in a non-oxidizing atmosphere (nitrogen) for 2 h to obtain a reduced reaction material; wherein the mass of graphite in the mixture is 10 times the theoretical mass of graphite required to reduce the waste ternary lithium battery powder, and the theoretical mass of the graphite is determined according to the following reduction reaction: LiNi x Co y Mn 1-x-y O2+(0.5+x+y)C=0.5Li2O+xNi+yCo+(1-xy)MnO+(0.5+x+y)CO, i.e., graphite reduces nickel, cobalt and manganese by carbon to 10 times the theoretical molar amount of lithium oxide, metallic nickel, metallic cobalt and manganese monoxide;

[0090] (2) leaching the reduction reaction material with water at 500 rpm and 20° C. at a liquid-to-solid ratio of 3:1 mL / g for 1.2 h, and filtering to obtain a Li-containing alkaline solution and a lithium-dissolved residue;

[0091] (3) adding calcium hydroxide to the alkaline solution containing Li to convert Li2CO3 in the alkaline solution containing Li into LiOH, wherein the molar amount of calcium in the calcium source is the molar amount of Ca and CO3 in the alkaline solution containing Li.2- The molar ratio is 0.8:1, and the conversion reaction is carried out at 400 rpm for 1.5 hours in a water bath at 75°C. The lithium-containing liquid phase after precipitation and filtration of calcium carbonate is evaporated and crystallized in a protective atmosphere (argon) to obtain lithium hydroxide monohydrate;

[0092] According to the liquid-to-solid ratio of 6 mL / g, the lithium-dissolving residue is acid-dissolved with a sulfuric acid solution with a concentration of 3 mol / L at 80°C for 3 h, and filtered to obtain a nickel-cobalt-manganese enriched solution with a pH value of 2 and graphite; wherein the total amount of sulfuric acid in the sulfuric acid solution is 1.5 times the theoretical amount of sulfuric acid required, and the theoretical amount of sulfuric acid required is calculated by the amount of sulfuric acid required to convert the nickel, cobalt and manganese in the lithium-dissolving residue into NiSO4, CoSO4 and MnSO4 respectively; the nickel-cobalt-manganese enriched solution is used as a raw material for nickel-cobalt-manganese extraction; and the graphite is returned to step (1) after drying and used as a reducing agent.

[0093] Example 3

[0094] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder, the method comprising:

[0095] (1) Mixing waste ternary lithium battery powder (622 type) and graphite to obtain a mixture, and subjecting the mixture to a reduction reaction at 1400° C. in a non-oxidizing atmosphere (argon) for 3 hours to obtain a reduced reaction material; wherein the mass of graphite in the mixture is twice the theoretical mass of graphite required to reduce the waste ternary lithium battery powder, and the theoretical mass of the graphite is determined according to the following reduction reaction: LiNi x Co y Mn 1-x-y O2+(0.5+x+y)C=0.5Li2O+xNi+yCo+(1-xy)MnO+(0.5+x+y)CO, that is, graphite reduces nickel, cobalt and manganese by carbon to twice the theoretical molar amount of lithium oxide, metallic nickel, metallic cobalt and manganese monoxide;

[0096] (2) leaching the reduction reaction material with water at 450 rpm and 25° C. at a liquid-to-solid ratio of 21:1 mL / g for 3 h, and filtering to obtain a Li-containing alkaline solution and a lithium-dissolved residue;

[0097] (3) adding calcium hydroxide to the alkaline solution containing Li to convert Li2CO3 in the alkaline solution containing Li into LiOH, wherein the molar amount of calcium in the calcium source is the molar amount of Ca and CO3 in the alkaline solution containing Li. 2- The molar ratio is 1:1, and the conversion reaction is carried out at 500 rpm for 0.8 h in a water bath at 80°C. The lithium-containing liquid phase after precipitation and filtration of calcium carbonate is evaporated and crystallized in a protective atmosphere (oxygen) to obtain lithium hydroxide monohydrate;

[0098] According to the liquid-to-solid ratio of 2mL / g, the lithium-dissolving residue is acid-dissolved with a sulfuric acid solution with a concentration of 8mol / L at 75°C for 5h, and filtered to obtain a nickel-cobalt-manganese enriched solution with a pH value of 0.5 and graphite; wherein the total amount of sulfuric acid in the sulfuric acid solution is 1.2 times the theoretical amount of sulfuric acid required, and the theoretical amount of sulfuric acid required is calculated by the amount of sulfuric acid required to convert the nickel, cobalt and manganese in the lithium-dissolving residue into NiSO4, CoSO4 and MnSO4 respectively; the nickel-cobalt-manganese enriched solution is used as a raw material for nickel-cobalt-manganese extraction; and the graphite is returned to step (1) after drying and used as a reducing agent.

[0099] The Li concentration in the Li-containing alkaline solution obtained in this embodiment is 10.96 g / L, CO3 2- The concentration is 0.002 mol / L, the lithium content in the lithium-dissolving residue is only 0.19 wt%, and the lithium leaching rate is 98.8%.

[0100] Example 4

[0101] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as that of Example 1 except that the liquid-to-solid ratio in step (2) is 50:1 mL / g, and will not be described again.

[0102] Example 5

[0103] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as that of Example 1 except that the liquid-to-solid ratio in step (2) is 0.5:1 mL / g, and will not be described again.

[0104] Example 6

[0105] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as Example 1 except that calcium hydroxide is not added in step (3) and a conversion reaction (double decomposition reaction) is not performed, and the details are not repeated here.

[0106] Example 7

[0107] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as Example 1 except that the lithium residue is dissolved with a sulfuric acid solution with a concentration of 10 mol / L, and will not be repeated here.

[0108] Example 8

[0109] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as Example 1 except that the lithium residue is dissolved with a sulfuric acid solution with a concentration of 0.5 mol / L, and will not be repeated here.

[0110] Example 9

[0111] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. Except that the temperature of the reduction reaction is 800° C., the rest of the method is the same as that of Example 1, and will not be repeated here.

[0112] Example 10

[0113] This embodiment provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. Except that the temperature of the reduction reaction is 1500° C., the rest of the method is the same as that of Example 1, and will not be repeated here.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as Example 1 except that 1.5 times the theoretical mass of graphite is added, and the details are not repeated here.

[0116] Comparative Example 2

[0117] This comparative example provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as Example 1 except that 1.0 times the theoretical mass of graphite is added, and the details are not repeated here.

[0118] Comparative Example 3

[0119] This comparative example provides a method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder. The method is the same as Example 1 except that 12 times the theoretical mass of graphite is added, and the details are not repeated here.

[0120] Test method: Inductively coupled plasma emission spectrometry was used to test the composition of waste ternary lithium battery powder, nickel-cobalt-manganese enriched solution and lithium-dissolved residue; acid-base titration was used to test the composition of lithium hydroxide monohydrate; direct carbon determination method and atomic absorption spectrometry were used to test the composition of graphite.

[0121] The compositions of the waste ternary lithium battery powder in Examples 1 to 3 are shown in Table 1 (wt %).

[0122] Table 1

[0123] Element Li Ni Co Mn Al Fe Example 1 6.6 25.7 6.2 11.1 0.2 / Example 2 6.7 35.1 7.2 7.0 0.5 0.5 Example 3 6.9 32.1 6.8 7.1 0.34 0.94

[0124] The compositions of the lithium-dissolving residues in Examples 1 to 3 are shown in Table 2 (wt %).

[0125] Table 2

[0126] Element Li Ni Co Mn Al Fe Example 1 0.24 22.1 5.3 9.5 0.14 / Example 2 0.19 29.4 6.4 5.8 0.4 0.5 Example 3 0.21 25.4 5.4 5.8 0.42 0.16

[0127] The composition of graphite in Examples 1 to 3 is shown in Table 3 (wt %).

[0128] Table 3

[0129] Element C Ni Co Mn Al Fe Example 1 99.4 0.04 0.02 0.01 0.01 / Example 2 98.9 0.06 0.02 0.05 0.01 0.07 Example 3 99.1 0.05 0.04 0.02 0.01 0.07

[0130] The compositions of the nickel-cobalt-manganese enriched solutions in Examples 1 to 3 are shown in Table 4 (wt%).

[0131] Table 4

[0132]

[0133]

[0134] The compositions of lithium hydroxide monohydrate in Examples 1 to 3 are shown in Table 5 (wt %).

[0135] Table 5

[0136] Element <![CDATA[LiOH·H2O]]> Al Na Ca Fe Ni Example 1 99.5 0.05 0.02 0.03 0.01 0.02 Example 2 99.2 0.08 0.02 0.01 0.02 0.02 Example 3 99.4 0.06 0.01 0.03 0.02 0.02

[0137] The purity of lithium hydroxide monohydrate, the purity of graphite, the leaching rates of nickel, cobalt, manganese and lithium, the recovery rate of graphite, the liquid-to-solid ratio of the leaching in step (2) and the particle size of the material after the reduction reaction in step (1) in the above embodiments and comparative examples were detected and statistically analyzed, and the results are shown in Table 6.

[0138] Table 6

[0139]

[0140] From Table 1 we can see that:

[0141] (1) It can be seen from Examples 1 to 3 that the method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder provided by the present invention can directly recycle and prepare lithium hydroxide monohydrate, and efficiently recycle nickel, cobalt and manganese. It can use water and only use water with a liquid-to-solid ratio of less than 10:1 mL / g to achieve a lithium leaching rate of more than 97.2%, a cobalt leaching rate of more than 99.2%, a nickel leaching rate of more than 98.9%, and a manganese leaching rate of more than 99.5% in a short time. The recovery rate of graphite reaches more than 99.2%, and the purity of lithium hydroxide monohydrate is as high as more than 98.6wt%, with high resource utilization rate.

[0142] (2) Combining Example 1 with Examples 4 to 5, it can be seen that the liquid-to-solid ratio of water-leached lithium will not affect the subsequent acid leaching efficiency of nickel, cobalt and manganese, but will affect the leaching efficiency of lithium and the purity of lithium hydroxide monohydrate. In Example 4, when the liquid-to-solid ratio is 50:1 mL / g, the purity of lithium hydroxide monohydrate is 96.2%, and in Example 5, when the liquid-to-solid ratio is 0.5 mL / g, the leaching efficiency of lithium is 90.2%. This shows that the present invention limits the liquid-to-solid ratio of water-leached lithium to a specific range, and can achieve a higher recovery efficiency of lithium hydroxide monohydrate with higher purity.

[0143] (3) It can be seen from Example 1 and Example 6 that the purity of the prepared lithium hydroxide monohydrate will be affected if the lithium carbonate in the water leaching solution is not converted by adding calcium hydroxide. The purity of the lithium hydroxide monohydrate in Example 6 is only 91.2%, while the purity of the lithium hydroxide monohydrate in Example 1 is as high as 98.6wt%. This shows that the calcium hydroxide conversion step defined in the present invention can further improve the purity of the lithium hydroxide monohydrate.

[0144] (4) It can be seen from Example 1 and Examples 7 to 8 that the concentration of sulfuric acid in the leached water residue will affect the subsequent recovery of nickel, cobalt, manganese and graphite. As shown in Example 7, when the sulfuric acid concentration is as high as 10 mol / L, the graphite residue will be destroyed, and a large amount of acid will remain, and the recovery rate of graphite is only 92.4%; as shown in Example 8, when the sulfuric acid concentration is as low as 0.5 mol / L, the nickel-cobalt alloy is difficult to be leached with weak acid, and the nickel-cobalt leaching rate is less than 90%; this shows that the present invention limits the sulfuric acid concentration within a specific range to ensure a high leaching rate of nickel, cobalt and manganese and a high graphite recovery efficiency.

[0145] (5) Combining Example 1 with Examples 9 to 10, it can be seen that the temperature of the reduction reaction will affect the subsequent water leaching of lithium and the acid leaching efficiency of nickel, cobalt and manganese. From Example 9, it can be seen that when the reduction temperature is 800°C, lithium carbonate does not decompose, and the water leaching efficiency of lithium is 56.4%. From Example 10, it can be seen that when the reduction temperature is 1500°C, nickel, cobalt and manganese are sintered, the alloy particles grow, and the leaching rates of nickel, cobalt and manganese are 79.6%, 80.1% and 85.4%, respectively, which are lower than those in Example 1, and the energy consumption is significantly increased compared with that in Example 1. This shows that the present invention limits the reduction temperature within a specific range, which can further ensure a high leaching rate of lithium, nickel, cobalt and manganese.

[0146] (6) It can be seen from Example 1 and Comparative Examples 1 to 3 that the content of reduced graphite will affect the subsequent water leaching of lithium and the acid leaching efficiency of nickel, cobalt and manganese. From Comparative Examples 1 to 2, it can be seen that the graphite content is insufficient, the local heat release during the reduction process causes nickel, cobalt and manganese to sinter, the lithium is coated, the leaching efficiency is reduced, the nickel, cobalt and manganese are alloyed and the particles are large, and the sulfuric acid leaching rate is reduced. The leaching rate of lithium is 75.4% and 87.6% when the graphite content is 1 times and 1.5 times the theoretical value, respectively, and the leaching rates of nickel, cobalt and manganese are 77.5%, 72.8%, 76.2% and 81.8%, 80.2%, 82.6% respectively. From Comparative Example 3, it can be seen that the graphite content is too high, and due to entrainment, the efficiency of water leaching of lithium is 94.6%. This shows that the present invention limits the reduced graphite content within a specific range to ensure a high leaching rate of lithium, nickel, cobalt and manganese.

[0147] The present invention illustrates the detailed features of the present invention through the above embodiments, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent replacement of the technical features selected by the present invention, addition of auxiliary technical features, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing lithium hydroxide monohydrate from waste ternary lithium battery powder, characterized in that: The method comprises the following steps: (1) mixing waste ternary lithium battery powder and graphite to obtain a mixture, and subjecting the mixture to a reduction reaction to obtain a reduced reaction material; wherein the mass of the graphite in the mixture is 2 to 10 times the theoretical mass of graphite required to reduce the waste ternary lithium battery powder; (2) leaching the material after the reduction reaction and performing solid-liquid separation to obtain a Li-containing alkaline solution; (3) The alkaline solution containing Li is evaporated and crystallized to obtain lithium hydroxide monohydrate.

2. The method according to claim 1, characterized in that The theoretical mass of the graphite in step (1) is determined according to the following reduction reaction: LiNi x Co y Mn 1-x-y O2+(0.5+x+y)C=0.5Li2O+xNi+yCo+(1-xy)MnO+(0.5+x+y)CO: Preferably, the temperature of the reduction reaction is 900-1400°C.

3. The method according to claim 1 or 2, characterized in that: The atmosphere of the reduction reaction in step (1) is a non-oxidizing atmosphere or a vacuum; Preferably, the non-oxidizing atmosphere comprises any one of nitrogen, argon, helium or carbon monoxide, or a combination of at least two thereof; Preferably, the reduction reaction time is 0.1 to 24 hours.

4. The method according to any one of claims 1 to 3, characterized in that: The waste ternary lithium battery powder in step (1) is one of type 111, type 523, type 622 or type 811, or a combination of at least two of them.

5. The method according to any one of claims 1 to 4, characterized in that: The material after the reduction reaction in step (1) includes nickel-cobalt-manganese particles; Preferably, the nickel, cobalt and manganese in the nickel-cobalt-manganese-containing particles include one or a combination of at least two of metallic nickel, metallic cobalt, a nickel-cobalt alloy or manganese oxide; Preferably, the particle size of nickel-cobalt metal particles in the material after the reduction reaction does not exceed 30 μm.

6. The method according to any one of claims 1 to 5, characterized in that: The leaching agent used in step (2) includes water or LiOH solution; Preferably, the liquid-to-solid ratio of the leaching is 1 to 100:1 mL / g, preferably 1 to 10:1 mL / g; Preferably, the leaching temperature is 5 to 100°C; Preferably, the leaching time is 0.1 to 24 hours, preferably 0.1 to 4 hours; Preferably, when the leaching medium is a LiOH solution, the concentration of LiOH in the LiOH solution does not exceed 18 g / L.

7. The method according to any one of claims 1 to 6, characterized in that: The solid-liquid separation in step (2) also produces a lithium-dissolved residue; Preferably, the residual lithium content in the lithium-dissolving residue is ≤0.3wt%.

8. The method according to any one of claims 1 to 7, characterized in that: The lithium-dissolving residue is acid-dissolved in a sulfuric acid solution, and solid-liquid separated to obtain a nickel-cobalt-manganese enriched solution and graphite; Preferably, the nickel-cobalt-manganese enriched solution is used as the raw material for nickel-cobalt-manganese extraction; Preferably, the graphite is returned to step (1) after drying and used as a reducing agent.

9. The method according to claim 8, characterized in that The total amount of sulfuric acid in the sulfuric acid solution is 1.2 to 1.5 times the theoretical amount of sulfuric acid required, and the method for calculating the theoretical amount of sulfuric acid required is the amount of sulfuric acid required to convert nickel, cobalt and manganese in the lithium-dissolving residue into NiSO4, CoSO4 and MnSO4 respectively; Preferably, the concentration of sulfuric acid in the sulfuric acid solution is 1 to 8 mol / L; Preferably, the liquid-to-solid ratio of the acid solution is 2 to 100 mL / g; Preferably, the acid dissolving temperature is 30 to 100°C; Preferably, the acid dissolution time is 0.5 to 24 hours; Preferably, the pH value of the nickel-cobalt-manganese enriched solution obtained by acid dissolution is 0-2.

10. The method according to any one of claims 1 to 9, characterized in that: Before the evaporation and crystallization in step (3), a calcium source is first added to carry out a conversion reaction to convert Li2CO3 in the Li-containing alkaline solution into LiOH; Preferably, the molar amount of Ca in the calcium source is equal to the molar amount of CO3 in the Li-containing alkaline solution. 2- The molar ratio is 0.8 to 1:1; Preferably, the calcium source is calcium hydroxide; Preferably, the evaporative crystallization is carried out in a protective atmosphere; Preferably, the protective atmosphere is any one of argon, nitrogen, oxygen or air depleted of CO2, or a combination of at least two thereof; Preferably, the purity of the lithium hydroxide monohydrate is ≥99wt%.

Images