Method for synergistically leaching lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode mixed waste

Abstract

The invention discloses a method for synergistically leaching lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode mixed waste, which comprises the following steps: mixing the two wastes according to a Fe / Co molar ratio of 1.4-1.8, reacting in 1.0-1.5 mol / L sulfuric acid at 20-40 DEG C for 80-100 minutes, leaching lithium and cobalt by using the self-oxidation-reduction action of the sulfuric acid, recovering valuable metals from a leaching solution, and recycling the valuable metals from the leaching solution. Leached residues are used as iron phosphate by-products; according to the method disclosed by the invention, by utilizing the inherent oxidation-reduction characteristic between lithium cobalt oxide and lithium iron phosphate, the spontaneous oxidation-reduction reaction is realized in the acid leaching process, and the situation that hydrogen peroxide and other oxidizing agents or reducing agents need to be additionally added in the traditional process is avoided, so that the reagent purchasing cost is directly saved, and the production efficiency is improved. And safety risks caused by storage and use of the unstable chemicals are also eliminated.

Description

Technical Field

[0001] This invention relates to the field of cathode waste recycling technology, and in particular to a method for the co-leaching of lithium and cobalt from mixed lithium cobalt oxide and lithium iron phosphate cathode waste. Background Technology

[0002] With the widespread use of lithium batteries, the number of expired lithium batteries has increased dramatically. Currently, the recycling and treatment of the two mainstream cathode materials, lithium cobalt oxide and lithium iron phosphate, usually adopts separate leaching processes. For lithium cobalt oxide cathode waste, acidic media and reducing agents such as hydrogen peroxide are commonly used to reduce the high-valence cobalt and dissolve the lithium. For lithium iron phosphate cathode waste, acidic conditions are usually supplemented with oxidizing agents such as hydrogen peroxide to selectively leach lithium and precipitate iron in the form of iron phosphate.

[0003] However, the use of redox reagents such as hydrogen peroxide in the above methods significantly increases the raw material cost and operational complexity of the recycling process. Furthermore, their storage and use pose certain safety risks. Since only lithium in lithium iron phosphate cathode materials has high recycling value, establishing a separate recycling production line is not economically viable, leading to low corporate willingness to recycle and a large amount of untreated lithium iron phosphate waste, resulting in a serious waste of lithium resources. At the same time, the two independent leaching systems also lead to duplication of equipment investment and energy consumption, making the overall process flow insufficiently integrated.

[0004] Therefore, in response to the problems mentioned above, this invention proposes a method for the synergistic leaching of lithium and cobalt from mixed waste of lithium cobalt oxide and lithium iron phosphate cathode. Summary of the Invention

[0005] To overcome the problems of high reagent costs, complex processes, and poor economic efficiency in recycling low-value lithium iron phosphate waste, which leads to resource waste in existing technologies, this invention proposes a method for the co-leaching of lithium and cobalt from mixed waste of lithium cobalt oxide and lithium iron phosphate cathode. This method utilizes the inherent redox properties of both materials under acidic conditions, thereby avoiding the need for additional redox reagents and achieving efficient co-leaching of lithium and cobalt. This simplifies the operation, reduces costs, and improves the overall resource recovery efficiency.

[0006] The technical solution of this invention is a method for co-leaching lithium and cobalt from mixed waste of lithium cobalt oxide and lithium iron phosphate cathodes, comprising the following steps: S1 provides lithium cobalt oxide cathode waste and lithium iron phosphate cathode waste. The waste comes from spent lithium-ion batteries and is processed through dismantling, separation, and crushing to obtain powdered materials with a particle size distribution of 1-10μm. The lithium cobalt oxide waste contains 5.5-6.5% lithium and 50-55% cobalt by mass, while the lithium iron phosphate waste contains 4.0-4.8% lithium, 33-36% iron, and 18-20% phosphorus by mass. S2, mix lithium iron phosphate cathode waste and lithium cobalt oxide cathode waste at a preferred molar ratio of iron to cobalt of 1.6 to obtain mixed waste; S3, prepare a sulfuric acid solution as a leaching agent, wherein the preferred sulfuric acid concentration is 1.25 mol / L, and the preferred amount of sulfuric acid used is 1.2 times the theoretical amount. The theoretical amount is calculated based on the auto-oxidation-reduction reaction formula, which is: ; S4. First, add sulfuric acid solution as a base liquid to the reaction vessel. Under a stirring speed preferably of 300 rpm, first add lithium iron phosphate cathode waste, then immediately add lithium cobalt oxide cathode waste. The addition of both is continuous without any time interval. The leaching reaction is carried out at a reaction temperature preferably of 32°C, and the reaction time is preferably 90 minutes, allowing lithium and cobalt to leach from the cathode waste into the solution, while iron is leached... Form sedimentation; S5. After the reaction is completed, the leachate and leachate residue are obtained by filtration or centrifugation. The leaching rates of lithium and cobalt in the leachate are over 94% and 91%, respectively. S6 recovers lithium and cobalt from the leachate through precipitation, solvent extraction or electrolysis. The main component of the leachate residue is iron phosphate, which is used as a by-product to prepare lithium-ion battery cathode materials or as a raw material for phosphate fertilizer.

[0007] Preferably, in step S6, lithium is recovered from the leachate by sodium carbonate precipitation and cobalt is recovered by oxalic acid precipitation, specifically including the following steps: A sodium carbonate solution with a concentration of 1.0-2.0 mol / L is slowly added to the leachate obtained by separation. The pH value at the end of the reaction is controlled to be 10-11. The reaction is stirred at a temperature of 50-70℃ for 30-60 minutes to form a white lithium carbonate precipitate that is insoluble in water. After the reaction is completed, solid-liquid separation is performed. The obtained solid is washed with deionized water and dried at 100-120℃ for 2-4 hours to obtain battery-grade lithium carbonate product. The pH of the mother liquor after lithium precipitation is adjusted to 2.0-3.0 with sulfuric acid. Then, an ammonium oxalate or oxalic acid solution with a concentration of 0.5-1.5 mol / L is added with stirring. The reaction temperature is controlled at 40-60℃ and the reaction time is 20-40 minutes to generate a pink cobalt oxalate precipitate. After the reaction is completed, solid-liquid separation is performed. The obtained solid is washed with deionized water and dried at 100-120℃ for 2-4 hours to obtain the cobalt oxalate product, which can be used as a precursor for the preparation of cobalt powder or cobalt oxide.

[0008] Preferably, the leaching residue in step S6, after washing and drying, is directly utilized as a by-product of ferric phosphate, specifically including the following steps: A1. The leaching residue obtained after liquid-solid separation is washed with hot deionized water at a temperature of 50-80℃ in a countercurrent or agitated manner. The washing liquid-solid ratio is (3-5):1L / kg. The washing is repeated 2-3 times until the washing liquid is neutral and the residual sulfate ion concentration is less than 100mg / L. A2. The washed filter cake is dried at 100-120℃ for 4-6 hours to obtain a grayish-white or light yellow powdery iron phosphate solid. A3, the obtained iron phosphate has a purity of not less than 95%, and can be directly used as a raw material for the regeneration and preparation of lithium iron phosphate cathode materials, or further purified and used as a chemical raw material and phosphate fertilizer.

[0009] Preferably, the lithium cobalt oxide and lithium iron phosphate cathode waste are mechanically crushed and classified, with the median particle size D50 controlled at 3-5 μm, and more than 98% of the particles having a particle size of less than 10 μm to ensure sufficient reaction surface area. The entire leaching reaction process is carried out in an open container or a container with a condenser reflux device under normal pressure. Besides the components inherent in the raw materials and the sulfuric acid leaching agent, no additional oxidizing or reducing agents (such as hydrogen peroxide, sodium sulfite, sodium thiosulfate, etc.) are added to the reaction system; the reaction relies entirely on the lithium cobalt oxide... Oxidizing properties and lithium iron phosphate The reaction proceeds through auto-oxidation-reduction interactions between the reducing properties of the components.

[0010] The beneficial effects of this invention are: 1. This invention utilizes lithium cobalt oxide... With lithium iron phosphate The inherent redox properties between them enable spontaneous redox reactions during acid leaching, avoiding the need for additional oxidants or reducing agents such as hydrogen peroxide in traditional processes. This not only directly saves on reagent procurement costs but also eliminates the safety risks associated with storing and using such unstable chemicals, making the entire recycling process more economical and safer.

[0011] 2. This invention combines lithium cobalt oxide and lithium iron phosphate waste, which originally required two separate devices for processing, into a single reaction system for synergistic treatment. This simplifies the complex multi-step leaching operation into a single step, thereby significantly simplifying the process flow, reducing the number of supporting equipment, reaction vessels, and control units required, thus lowering fixed asset investment and production line footprint, and improving the processing efficiency per unit of equipment.

[0012] 3. This invention successfully transforms low-profit lithium iron phosphate waste into a reducing agent necessary for the leaching process, turning it from waste to a valuable reactant. This allows for efficient recovery of lithium resources without the need for a separate recycling line, significantly increasing the resource value of this type of waste. It solves the problem of resource waste caused by its poor economic viability and encourages companies to recycle and process it.

[0013] 4. The leaching residue generated during the synergistic leaching process of this invention is mainly composed of iron phosphate. After simple washing and drying, it can be directly used as a by-product for the regeneration of lithium iron phosphate cathode materials or as a raw material for phosphate fertilizer. This realizes the resource recycling of solid waste, avoids the storage and disposal costs of hazardous waste residue, and makes the entire recycling process tend towards a clean production mode with no or little waste. Attached Figure Description

[0014] Figure 1 The diagram shown is a schematic representation of the method flow of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This invention provides an embodiment of a method for co-leaching lithium and cobalt from a mixed waste of lithium cobalt oxide and lithium iron phosphate cathodes: This invention utilizes lithium cobalt oxide ( Trivalent cobalt () The strong oxidizing properties of lithium iron phosphate (LiFePO4) Divalent iron () The reducing properties of sulfuric acid allow for the construction of a spontaneous redox system in a sulfuric acid medium, with the core reaction being: ; In this reaction, Restored to Thus, it is released from the stable oxide lattice and enters the solution. Oxidized to It combines with phosphate ions in the solution to form insoluble ferric phosphate (Fe2+). Lithium ions ( ) precipitation. Due to its ionic state and interlayer embedding characteristics, it is efficiently released under the dual effects of acidity and redox reactions that destroy its structure.

[0017] Please see Figure 1 The present invention includes the following steps: (1) The collected waste lithium cobalt oxide and lithium iron phosphate positive electrode sheets are heat-treated to remove the binder, and then crushed, sieved and physically sorted to obtain high purity lithium cobalt oxide and lithium iron phosphate active material powder. The median particle size D50 of the powder is controlled within the range of 1-10 μm to ensure that the subsequent reaction has sufficient specific surface area.

[0018] (2) Weigh and mix the lithium cobalt oxide cathode waste obtained from the above pretreatment with the lithium iron phosphate cathode waste, and control the molar ratio of iron to cobalt in the mixed waste to be between 1.4 and 1.8.

[0019] (3) Mix the uniformly mixed waste with sulfuric acid leaching agent in the reactor. The concentration of sulfuric acid solution is 1.0-1.5 mol / L. The actual amount used is 1.1-1.3 times the theoretically calculated amount. The leaching reaction is carried out at room temperature of 20-40℃ for 80-100 minutes. When adding materials, first add lithium iron phosphate waste, and then immediately add lithium cobalt oxide waste. Keep stirring throughout the reaction process to ensure full contact between solid and liquid. Utilize the self-oxidation and reduction effect between the two to achieve efficient leaching of lithium and cobalt while precipitating iron.

[0020] (4) After the leaching reaction is completed, the reaction slurry is immediately subjected to solid-liquid separation operation by filtration or centrifugation to obtain a leaching solution rich in lithium ions and cobalt ions and a leaching residue whose main component is iron phosphate. The leaching residue is washed to recover the valuable solution entrained, and the washing liquid is incorporated into the main leaching solution.

[0021] (5) Further processing of the separated leachate to recover valuable metals, such as using carbonate precipitation to recover high-purity lithium carbonate and using oxalate precipitation to recover cobalt oxalate. The separated leachate residue can be dried and used as a by-product iron phosphate to directly prepare lithium-ion battery cathode materials or as a raw material for phosphate fertilizer, thereby realizing the resource utilization of all components.

[0022] This invention provides Embodiment 1: Experimental materials: Lithium cobalt oxide ( The composition (mass fraction) of the positive electrode waste is Li 6.12%, Co 53.52%, with the remainder being impurities such as aluminum and copper. The median particle size D50 of the powder is 4.1 μm. Lithium iron phosphate (LiFePO4) The composition (mass fraction) of the positive electrode waste is Li 4.43%, Fe 34.58%, and P 19.35%. The median particle size D50 of the powder is 3.8 μm. The leaching agent is a sulfuric acid solution prepared from industrial-grade concentrated sulfuric acid and deionized water.

[0023] Experimental steps: (1) According to the reaction formula Calculate the theoretical sulfuric acid consumption by weighing 5.00g. Waste and 11.73g Waste (Fe / Co molar ratio = 1.6).

[0024] (2) Based on 1.2 times the theoretical amount of sulfuric acid (1 times the amount), prepare 250 mL of 1.25 mol / L sulfuric acid solution with deionized water and place it in the reactor.

[0025] (3) Turn on the stirrer, set the speed to 300 rpm, and at room temperature (controlled at 32±1℃), first stir... All waste materials were added to the sulfuric acid solution, and then immediately added... Waste material, start timing.

[0026] (4) The reaction lasts for 90 minutes, and the temperature is kept constant and stirred during the reaction.

[0027] (5) After the reaction is complete, vacuum filtration is performed immediately to separate the leachate from the leach residue. The leach residue is washed three times with hot water at 50°C, and the washing liquid is combined with the leachate and the volume is adjusted.

[0028] (6) Take a portion of the leachate, dilute it appropriately, and determine the concentrations of Li, Co and Fe using ICP-OES.

[0029] (7) The leaching residue was dried at 105°C for 4 hours and then kept for analysis.

[0030] result: The leaching rate is calculated using the following formula: ; In the formula, Leaching rates of elements Li, Co, and Fe (%) C represents the mass concentration (g / L) of the elements Li, Co, and Fe in the leachate. V is the volume of the leachate (L); m is the mass of the waste cathode powder (g); w represents the mass fraction (%) of Li, Co, and Fe elements in the waste cathode powder.

[0031] (1) The concentration of Li in the leachate was 1.85 g / L and the volume was 0.32 L. The total mass of the mixed waste was 16.73 g and the weighted average lithium content was 5.01%. The calculated η(Li) = (1.85 × 0.32) / (16.73 × 5.01%) × 100% = 94.33%.

[0032] (2) The Co concentration was measured to be 9.12 g / L using the above formula. The cobalt in the mixed waste originated from The mass is 5.00g × 53.52% = 2.676g. The calculated η(Co) is (9.12 × 0.32) / 2.676 × 100% = 91.12%.

[0033] (3) The Fe concentration was measured to be 0.98 g / L using the above formula. The iron in the mixed waste originated from The mass is 11.73g × 34.58% = 4.056g. The calculated η(Fe) is (0.98 × 0.32) / 4.056 × 100% = 49.85%.

[0034] The above results show that the leaching rates of lithium and cobalt both exceeded 91%, proving that the autoreduction reaction was thorough and efficient. The leaching rate of iron was effectively suppressed to below 50%, indicating that most of the iron had been converted into... Introduced into the slag, it facilitates subsequent metal separation. Meanwhile, this system does not use... This saves on reagent costs and reduces safety risks. The reaction occurs at room temperature, resulting in extremely low energy consumption.

[0035] This invention provides Embodiment 2: This embodiment was used to investigate the effect of sulfuric acid concentration on leaching effect. The sulfuric acid amount was 1 times the theoretical amount. Lithium iron phosphate and lithium cobalt oxide cathode waste were added to the sulfuric acid bottom solution in sequence. The Fe to Co molar ratio in the mixed waste was 1.2. The reaction temperature was 40℃ and the reaction time was 120 min. The effect of sulfuric acid concentration on the leaching rate of Li, Co and Fe was investigated.

[0036]

[0037] The table above shows that the leaching rate of Li gradually increases with increasing sulfuric acid concentration, but the change becomes insignificant after 1.25 mol / L. Compared to Co and Fe, Li has a higher leaching rate. This is because lithium ions are embedded between the layered structures of the cathode material. During charging and discharging, lithium ions can be extracted and inserted, remaining in a free state, and therefore are more easily leached by sulfuric acid. The leaching of Co and Fe, on the other hand, requires more disruption of the material's molecular structure. When the sulfuric acid concentration is below 0.75 mol / L, increasing the sulfuric acid concentration results in a slower increase in the leaching rates of Co and Fe. When the sulfuric acid concentration increases from 0.75 mol / L to 1.25 mol / L, the leaching rate of Co increases rapidly, while the leaching rate of Fe decreases. During the leaching process, sulfuric acid plays a role in acid dissolution and providing an acidic environment for the oxidation reaction. When the sulfuric acid concentration is below 0.75 mol / L, mixed leaching is mainly acid dissolution, and the redox reaction between Co and Fe is not ideal. The leaching rate of Co is lower than that of Fe, indicating that acid dissolution of lithium iron phosphate occurs more readily. When the sulfuric acid concentration is higher than 0.75 mol / L, With a sufficiently acidic environment, the oxidation-reduction reaction between Co and Fe gradually occurs. quilt restore and As more solution enters, the leaching rate of Co increases rapidly. Correspondingly... Oxidized form Precipitation, therefore in solution As the sulfuric acid concentration decreases, the leaching rate of Fe decreases. Redox reactions promote the structural breakdown and decomposition of lithium cobalt oxide and lithium iron phosphate. When the sulfuric acid concentration exceeds 1.25 mol / L, the leaching rates of Li and Co remain relatively stable, while the leaching rate of Fe may decrease. A small amount of dissolution occurred, resulting in a slight increase. Taking all factors into account, 1.25 mol / L was chosen as the optimal concentration of sulfuric acid.

[0038] This invention provides embodiment 3: This embodiment investigates the effect of sulfuric acid dosage on leaching efficiency. Under the conditions of 1.25 mol / L sulfuric acid concentration, lithium iron phosphate and lithium cobalt oxide cathode waste were sequentially added to the sulfuric acid bottom solution, the Fe to Co molar ratio in the mixed waste was 1.2, the reaction temperature was 40℃, and the reaction time was 120 min, the mixed acid leaching was carried out to examine the effect of sulfuric acid dosage on the leaching rates of Li, Co and Fe.

[0039] Ratio of sulfuric acid usage to theoretical amount Lithium (Li) leaching rate Cobalt (Co) leaching rate Iron (Fe) leaching rate 0.6 51.42 22.32 32.53 0.8 65.71 34.72 49.37 1.0 84.52 59.62 42.46 1.2 92.23 72.15 38.64 1.4 94.35 73.54 40.08 The table above shows that the leaching rate of Li gradually increases with increasing sulfuric acid dosage. After reaching the theoretical dosage, further increases in sulfuric acid dosage result in only a small increase in the leaching rate of Li. Under the same conditions, the leaching rate of Li is higher than that of Co and Fe, which is determined by the form in which Li exists in the material. When the sulfuric acid dosage is less than 0.8 times the theoretical dosage, the leaching rates of Co and Fe increase with increasing sulfuric acid dosage. Due to insufficient total sulfuric acid, the redox reaction motive force between Co and Fe is insufficient, and the leaching of Co and Fe in the cathode waste is mainly acid-soluble. Lithium iron phosphate is more acid-soluble than lithium cobalt oxide, so the leaching rate of Fe is higher than that of Co. When the sulfuric acid dosage increases from 0.8 times to 1.2 times the theoretical dosage, the leaching rate of Co increases rapidly while the leaching rate of Fe decreases, indicating that the redox reaction has sufficient motive force with the increase in total sulfuric acid dosage. When the sulfuric acid dosage is more than 1.2 times the theoretical dosage, the leaching rate of Co remains basically stable, while the leaching rate of Fe increases slightly. Taking all factors into consideration, the optimal amount of sulfuric acid is selected as 1.2 times the theoretical amount.

[0040] This invention provides embodiment 4: This embodiment investigates the effect of the Fe to Co molar ratio on leaching efficiency. Under conditions of 1.2 times the theoretical sulfuric acid dosage, a sulfuric acid concentration of 1.25 mol / L, and sequential addition of lithium iron phosphate and lithium cobalt oxide cathode waste to the sulfuric acid base solution at a reaction temperature of 40°C and a reaction time of 120 min, mixed acid leaching was performed. The effect of the Fe to Co molar ratio in the mixed waste on the leaching rates of Li, Co, and Fe was examined. The waste material is 5.00g, which is obtained by changing... The amount of waste added resulted in Fe / Co molar ratios of 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0, respectively.

[0041] Fe / Co molar ratio Lithium (Li) leaching rate Cobalt (Co) leaching rate Iron (Fe) leaching rate 1.0 93.85 82.54 41.23 1.2 94.01 86.79 44.67 1.4 94.20 89.45 47.12 1.6 94.33 91.12 49.85 1.8 94.28 91.08 55.94 2.0 94.25 90.95 62.15 The table above shows that as the Fe / Co molar ratio increases, the leaching rate of Li remains relatively stable at around 94%, indicating complete leaching and minimal impact on lithium leaching. The leaching rate of cobalt increases significantly with the Fe / Co molar ratio, rising from 82.54% at 1.0 to 91.12% at 1.6. This is because increasing the Fe / Co molar ratio... The amount of (reducing agent) used is for reducing... It provided more electrons, which promoted Structural damage and cobalt leaching. When the Fe / Co molar ratio exceeds 1.6, the cobalt leaching rate tends to stabilize, indicating that the reducing agent is sufficient. Excessive amounts... In an acidic environment, simple acid dissolution occurs, producing substances that cannot be completely oxidized. This leads to a sharp increase in the iron leaching rate, which not only increases the burden on subsequent iron removal solutions but also wastes reducing agents.

[0042] This invention provides a comparative example 1: This comparative example demonstrates the advantages of the present invention by using existing processes for treating two types of waste.

[0043] (1) Pickling alone (with) ): Conditions: Weigh out 5.00g Add 1.25 mol / L sulfuric acid solution to the waste material (the amount used is 1.2 times the theoretical amount in Example 1), and add 7.5 mL of 30% sulfuric acid solution. As a reducing agent. React at room temperature (32°C) for 90 minutes.

[0044] Results: The leaching rate of Li was 64.05%, and the leaching rate of Co was 37.53%.

[0045] Pickling alone (with) ): Conditions: Weigh out 11.73g Add 1.25 mol / L sulfuric acid solution to the waste material (same amount as in Example 1), and add 7.5 mL of 30% sulfuric acid solution. As an oxidizing agent, the reaction was carried out at room temperature (32°C) for 90 minutes.

[0046] Results: The leaching rate of Li was 80.47%, and the leaching rate of Fe was 69.78%.

[0047] This comparative example assumes no synergistic effect. Acid leaching alone is extremely ineffective because it lacks sufficient reducing power. Reduced to soluble form Despite joining However, its reduction efficiency at room temperature may not be sufficient to completely destroy the stable [structure / structure]. structure.

[0048] When acid leaching is performed alone, the lithium leaching rate is acceptable, but the iron leaching rate is very high, failing to achieve selective lithium leaching and requiring a complex iron removal step afterwards. This comparative example demonstrates that traditional separate treatment processes are not only complex and consume a lot of reagents, but also have a leaching effect far inferior to the synergistic process of this invention.

[0049] This invention provides a comparative example 2: This comparative example uses the exact same materials, sulfuric acid concentration and dosage, temperature and time as Example 1. The only difference is that... Waste replacement with stoichiometry and The mixture (making its Co content equal to 5.00g) (The waste is the same), the cobalt in this mixture is in a mixed state of +2 and +3 valence, and does not possess... It has a strong oxidizing lattice structure.

[0050] Results: The Li leaching rate was 71.25% (mainly from...). Acid solubility and The reaction); the Co leaching rate was 48.90% (mainly due to...). middle Acid solubility, (Not effectively reduced); Fe leaching rate was 66.54% ( (Normal acid solubility, no oxidizing agent to cause precipitation).

[0051] Therefore, when the system does not exist Provided strong oxidizing properties At that time, the autoreduction reaction could not occur. The results were significantly worse than in Example 1, with extremely low Co leaching and substantial Fe dissolution. This demonstrates that the high Co leaching rate and low Fe leaching rate of the present invention do not originate from simple physical mixing and acid dissolution, but rather depend on… and Specific and efficient auto-oxidation-reduction reactions between them.

[0052] The specific comparison results are shown in the table below:

[0053] This invention provides an embodiment 5: The utilization of leaching residue is explained below: The leaching residue obtained in Example 1 was washed with hot water and dried, and then subjected to X-ray diffraction (XRD) analysis. The results showed that its main phase was ferric phosphate (Fe2PO4). The leaching residue contained a small amount of amorphous carbon. Chemical composition analysis of the leaching residue revealed... The content reaches 95.2%. This product meets the primary raw material standards for recycled lithium iron phosphate raw materials of some enterprises and can be sold directly or used for the regeneration preparation of self-produced lithium iron phosphate cathode materials. This realizes the transformation of hazardous waste into high value-added products.

[0054] The utilization of the leachate is explained below: (1) Heat the leachate to 60°C, and slowly add 1.5 mol / L of [agent / concentrate] while stirring. The solution was adjusted to pH 10.5. After stirring for 40 minutes, a large amount of white precipitate formed. After filtration, washing, and drying, lithium carbonate (lithium carbonate) was obtained. Solid. Titration analysis showed a purity of 99.3%, meeting the relevant standards for battery-grade lithium carbonate. Lithium precipitation recovery exceeded 98%.

[0055] (2) Adjust the pH of the mother liquor after lithium precipitation to 2.5 using sulfuric acid. At 50°C, slowly add 1.0 mol / L oxalic acid (… A solution of cobalt oxalate was stirred for 30 minutes to produce a pink color. Precipitation occurred. After filtration, washing, and drying, cobalt oxalate was obtained. Analysis showed that... With a purity exceeding 99%, it can be used as a precursor for the preparation of cobalt oxide or metallic cobalt. The cobalt precipitation recovery rate exceeds 99%.

[0056] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. Process for the synergic leaching of lithium and cobalt from lithium cobaltate and lithium iron phosphate positive electrode mixed scrap, characterized in that, The method comprises the following steps: S1, providing lithium cobaltate positive electrode waste and lithium iron phosphate positive electrode waste, wherein the waste is derived from waste lithium ion batteries, and is subjected to disassembly, separation and crushing treatment to obtain a powder material, wherein the lithium cobaltate waste has a lithium mass fraction of 5.5-6.5% and a cobalt mass fraction of 50-55%, and the lithium iron phosphate waste has a lithium mass fraction of 4.0-4.8%, an iron mass fraction of 33-36% and a phosphorus mass fraction of 18-20%; S2, mixing the lithium cobaltate positive electrode waste and the lithium iron phosphate positive electrode waste at a molar ratio of iron to cobalt of 1.4-1.8 to obtain mixed waste; S3, preparing a sulfuric acid solution as a leaching agent, wherein the sulfuric acid concentration is 1.0-1.5 mol / L, and the sulfuric acid dosage is 1.1-1.3 times the theoretical amount, the theoretical amount being calculated based on the following formula for the oxidation-reduction reaction: ； S4, in the reaction vessel, first add sulfuric acid solution as the bottom liquid, under the condition of stirring speed of 200-400 rpm, first add lithium iron phosphate positive electrode waste, then immediately add lithium cobaltate positive electrode waste, the two processes are continuous, without time interval, under the reaction temperature of 20-40℃, carry out leaching reaction, reaction time is 80-100 minutes, make lithium and cobalt leach from the positive electrode waste into the solution, at the same time, iron precipitates in the form of ​ S5, after the reaction is completed, the leaching solution and the leaching residue are obtained by filtration or centrifugal separation, wherein the leaching rates of lithium and cobalt in the leaching solution are above 94% and 91%, respectively; S6, recovering lithium and cobalt from the leaching solution by precipitation, solvent extraction or electrolysis, wherein the main component of the leaching residue is iron phosphate, which is used as a by-product to prepare a lithium ion battery positive electrode material or as a phosphate fertilizer raw material.

2. The process for synergic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode mixed scrap according to claim 1, characterized in that: The molar ratio of iron to cobalt in step S2 is 1.

6.

3. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap according to claim 1, characterized by: The sulfuric acid concentration in step S3 is 1.25 mol / L.

4. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap of claim 1, wherein: The sulfuric acid dosage in step S3 is 1.2 times the theoretical amount.

5. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap of claim 1, wherein: The reaction temperature in step S4 is room temperature 32℃.

6. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap of claim 1, wherein: The reaction time in step S4 is 90 minutes.

7. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap of claim 1, wherein: The stirring speed in step S4 is 300 rpm.

8. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap of claim 1, wherein: In step S6, lithium is recovered from the leaching solution by a sodium carbonate precipitation method, and cobalt is recovered by an oxalic acid precipitation method.

9. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap of claim 1, wherein: After the leaching residue in step S6 is washed and dried, it is directly used as an iron phosphate by-product.

10. The process for synergistic leaching of lithium and cobalt from lithium cobalt oxide and lithium iron phosphate positive electrode hybrid scrap of claim 1, wherein: In step S1, the particle size distribution of the waste powder is 1-10 μm, and the leaching reaction is carried out under normal pressure and without additional oxidation-reduction reagents.

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