A method for recycling powder of battery pole pieces

Abstract

The present invention belongs to the technical field of lithium battery resource recycling, and in particular relates to a method for recycling powder of battery pole pieces. The present invention provides a method for recycling powder of battery pole pieces, comprising the following steps: disassembling a lithium battery to obtain a positive pole piece and a negative pole piece, combining the positive pole piece and the negative pole piece to obtain a pole piece group; infiltrating the pole piece group with a carbonate solution, and roasting the infiltrated pole piece group to obtain a roasting material and a roasting gas; and separating the roasting material to obtain a powder and a foil. The powder recycling method provided by the present invention can solve the problems of difficulty in separating powder from aluminum foil, low powder purity and recovery rate, and inability to completely recycle foil in the battery recycling process. While simplifying the battery recycling process, it is of great significance for the efficient recovery of lithium carbonate salt products.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery resource recovery, and in particular relates to a method for recovering powder of battery pole pieces. Background Art

[0002] With the development of the new energy industry, battery recycling technologies are constantly evolving. This includes cascade utilization, pretreatment processes, resource recovery, and material repair. Pretreatment primarily involves processing spent lithium batteries to produce a powder suitable for subsequent recycling. The impurity content in this powder directly impacts the complexity of the back-end process, as well as the recovery rate and purity of the lithium carbonate salt.

[0003] In battery electrodes, the foil materials primarily include aluminum foil and copper foil, with powder attached to the foil surface via an adhesive. Separating the powder from the aluminum foil is difficult. Existing methods for separating powder from aluminum foil include the following: directly crushing the electrode and then screening to obtain powder; crushing and calcining the electrode, followed by crushing and screening to obtain powder; or soaking and dissolving the electrode in an alkaline solution, utilizing aluminum's alkaline solubility to completely dissolve the aluminum foil, followed by filtration and drying to obtain the powder. Among the above three methods, directly crushing the electrode will lead to the generation of a large amount of tiny aluminum powder, and there is a binder between the powder and the aluminum foil. Mechanical crushing will cause a large amount of powder to remain on the aluminum foil, resulting in a high content of aluminum impurities in the peeled powder. It is necessary to increase the removal of aluminum impurities in the subsequent process, which is not conducive to the efficient recovery of subsequent lithium carbonate salts; although the binder can be decomposed by calcining the electrode after crushing it, a large amount of aluminum impurities will also be introduced; and using alkaline substances such as liquid alkali to dissolve the aluminum foil to obtain powder will consume a large amount of alkaline substances, increase production costs, and this process produces hydrogen and a large amount of heat due to the thermite reaction, which has a greater safety risk.

[0004] In view of the above, the existing recycling processes for waste lithium batteries are unable to simply, efficiently and cost-effectively separate the powder from the aluminum foil, and cannot effectively recover the intact aluminum foil and high-purity powder, resulting in a complex subsequent lithium carbonate salt recovery process with low purity and recovery rate. Therefore, there is an urgent need to design a new recycling process to optimize the pretreatment process for battery recycling and thus efficiently recover lithium carbonate salt. Summary of the Invention

[0005] In response to the above, the present invention provides a method for recovering powder of battery electrodes, aiming to solve the problems in the prior art, such as difficulty in peeling powder from aluminum foil, easy introduction of aluminum impurities into the recovered powder, resulting in low powder purity, and inability to completely recover the aluminum foil, which makes the process of further recovering lithium carbonate salt from the powder complicated and the recovery rate of lithium carbonate salt low.

[0006] The present invention first provides a method for recovering powder from a battery electrode, comprising the following steps:

[0007] S1. Disassemble the lithium battery to obtain the positive electrode sheet and the negative electrode sheet, and combine the positive electrode sheet and the negative electrode sheet to obtain an electrode sheet group;

[0008] S2. Infiltrating the electrode assembly with a carbonate solution, and calcining the infiltrated electrode assembly to obtain a calcined material and a calcined gas;

[0009] S3. Separate the calcined material to obtain powder and foil.

[0010] The powder recovery method provided in the present application is designed to combine a positive electrode sheet and a negative electrode sheet to obtain an electrode sheet group, and use a carbonate solution to infiltrate the electrode sheet group. By utilizing the slight solubility of the carbonate solution in aluminum, after the electrode sheet is infiltrated with the carbonate solution, fine cracks can be generated between the aluminum foil of the positive electrode sheet and the powder; the electrode sheet group after infiltration is calcined, so that after the carbonate solution is heated at high temperature, a large amount of carbon dioxide gas is generated in a short time, causing the fine cracks to further produce stress expansion, thereby promoting the separation of the powder and the aluminum foil, and obtaining calcined material and calcined gas.

[0011] At the same time, during the roasting process, the carbon dioxide obtained by the decomposition of the carbonate solution reacts with the carbon in the graphite of the negative electrode sheet to undergo a reduction reaction, so that the roasting gas contains carbon monoxide gas in addition to carbon dioxide, which helps to further reduce the lithium-containing oxide in the powder, thereby realizing the reduction roasting of the lithium element, so that the lithium element in the powder generates more active lithium oxide or lithium element, and further generates lithium carbonate under the action of carbon dioxide, which can improve the purity of the final lithium carbonate salt product; the roasted material can be subjected to simple powder stripping treatment such as grinding and screening to obtain powder and foil.

[0012] Since the electrode does not need to be crushed in the powder recovery method of the present invention, the mechanical crushing process that causes the crushed foil to carry powder and a small amount of crushed foil to mix with powder is avoided, the powder recovery rate and the purity of the obtained powder are greatly improved, and the recovered aluminum foil also tends to be complete.

[0013] In a preferred solution of the present application, a carbonate solution is used to infiltrate the electrode group, and the infiltration method is at least one of immersion and spraying.

[0014] In a preferred solution of the present application, the step of combining the positive electrode sheet and the negative electrode sheet to obtain the electrode sheet group is as follows: folding the positive electrode sheet and the negative electrode sheet to obtain the electrode sheet group.

[0015] In a preferred embodiment of the present application, the electrode assembly comprises at least one positive electrode sheet and one negative electrode sheet. The positive and negative electrode sheets are stacked and then folded. The folded electrode assembly has a width of 2 to 5 cm and a thickness of 5 to 10 cm. The positive and negative electrode sheets in the folded electrode assembly have creases. During firing, stress fracture occurs at the creases, promoting the separation of the powder from the aluminum foil. Furthermore, the positive and negative electrode sheets are stacked in a cross-stack arrangement to fully utilize the subsequently generated firing gases.

[0016] In a preferred embodiment of the present application, the carbonate solution includes at least one of sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate solution or ammonium bicarbonate solution.

[0017] In the preferred solution of the present application, in the step of baking the electrode group after the impregnation, the electrode group after the impregnation is aged before the baking so that the electrode group is fully impregnated and more fine cracks are generated between the aluminum foil and the powder; the electrode group after the aging treatment is compacted to remove the air and moisture in the electrode group, so that a large amount of gas can be generated in a short time during the baking treatment.

[0018] In a preferred embodiment of the present application, the aging temperature of the aging treatment is controlled at 25°C to 45°C, and the aging time is 2 to 6 hours, so that the carbonate solution and the aluminum foil fully react and more fine cracks are generated on the surface of the aluminum foil; and / or the calcination treatment is carried out in an air-tight environment, the calcination temperature is 600°C to 700°C, and the calcination time is 4 to 6 hours; and / or the components of the calcination gas include carbon dioxide and carbon monoxide.

[0019] In the preferred solution of the present application, the calcined material is subjected to a separation treatment, and the separation treatment includes at least one grinding treatment and at least one screening treatment; after the calcination treatment, since the binder in the electrode assembly is decomposed by high temperature and there are cracks between the aluminum foil and the powder, the powder of the calcined material falls off from the foil after grinding, and the powder and the foil are separated after screening to obtain a complete foil and a high-purity powder.

[0020] In the preferred solution of the present application, the calcined material is spread out and then separated to promote the full separation of the powder and the foil, while preventing the foil from breaking and deforming. The number of layers of the electrode in the calcined material is 10 to 20 layers. After screening, the oversize and undersize are obtained. The oversize includes the foil, and the undersize includes the powder.

[0021] In the preferred embodiment of the present application, the powder recovery method further comprises: post-processing the powder to obtain a lithium carbonate salt product; a high-purity lithium carbonate salt product can be obtained by post-processing the powder, and the recovery rate of the lithium carbonate salt product is high.

[0022] In the preferred embodiment of the present application, the post-processing includes: ball milling the powder, mixing the ball-milled powder with water, and then introducing a carbon source gas and / or a roasting gas to perform a carbonization reaction to obtain a mixed slurry containing lithium salt; the carbonization reaction converts the lithium element in the powder into highly soluble lithium bicarbonate, thereby separating the lithium element from other impurity elements; filtering the mixed slurry containing lithium salt to obtain a leaching residue and a filtrate; leaching the leaching residue to obtain a nickel, cobalt, manganese product or an iron phosphate product; and heating and stirring the filtrate and performing a filtration separation process to obtain a lithium carbonate salt product. Preferably, the carbon source gas is carbon dioxide.

[0023] In the preferred scheme of the present application, in the ball milling treatment, the material ball-milled to a powder particle size of less than 0.074 mm accounts for more than 75%, making the subsequent recovery of lithium carbonate salt more efficient; when the ball-milled powder is mixed with water, the mass ratio of powder to water is controlled to 1: (25~45); the temperature of the carbonization reaction is controlled to 25℃~40℃, and the reaction time is 1~3h; the temperature of the heating and stirring treatment is controlled at 80℃~90℃ to promote the precipitation of lithium carbonate crystals.

[0024] In the preferred solution of the present application, ball milling is carried out using at least one of steel balls, ceramic balls, and zirconium balls; and / or the material ball-milled to a powder particle size of less than 0.038 mm accounts for more than 75%. The small powder particle size is conducive to the subsequent carbonization reaction of the lithium element in the powder to recover a high-purity lithium carbonate salt product.

[0025] Compared with the prior art, the battery pole piece powder recovery method provided by the present invention has the following beneficial effects:

[0026] The powder recovery method provided by the present invention realizes the separation of foil and powder under the intact electrode. The present invention does not need to crush the electrode, avoids the generation of fine-particle aluminum, greatly reduces the impurity content in the powder, thereby improving the recovery rate and product purity of lithium carbonate salt, and the recovered foil is also more complete; the present invention simultaneously realizes the stripping of powder and the reduction roasting of lithium in the powder under the condition of one heat treatment, so that the recycling process of waste lithium batteries is simplified; the generated roasting gas can be used for the purification of lithium carbonate salt, saving the use of energy and auxiliary materials, and reducing production costs.

[0027] Other features and advantages of the present invention will be further described in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A schematic diagram of the steps of the powder recovery method exemplified by the present invention;

[0030] Figure 2 The figure is a schematic diagram of the process of the powder recovery method provided by the present invention. DETAILED DESCRIPTION

[0031] To make the above and other features and advantages of the present invention more clear, the present invention is further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explaining to those skilled in the art and are only exemplary and not restrictive.

[0032]

Overall Inventive Concept

[0033] The overall inventive concept of the present invention is to provide a method for recycling powder of battery pole pieces. The method is designed to solve the problems existing in the powder and aluminum foil separation process in the prior art. Considering that in the prior art lithium batteries, lithium-ion batteries other than lithium titanate all contain lithium in the positive electrode and graphite in the negative electrode, these lithium batteries usually need to crush the pole pieces as a whole when recycling, and use subsequent screening to separate the powder and aluminum foil, resulting in a large amount of aluminum impurities in the powder, which is not convenient for the subsequent recovery of lithium carbonate salts, or the aluminum foil is completely dissolved in an alkaline solution before the powder is recovered, making it impossible to completely recycle the foil. The present invention starts from the material properties of the foil itself, utilizes the slight solubility of aluminum foil when it comes into contact with carbonate solutions such as sodium bicarbonate or ammonium bicarbonate, and generates cracks between the aluminum foil and the powder through chemical reaction. The carbonate is roasted at high temperature to produce a large amount of gas, which promotes the expansion of the cracks and stress expansion to separate the powder from the foil, thereby avoiding the introduction of a large amount of aluminum foil into the powder, and at the same time, a complete foil can be separated.

[0034] In the general inventive concept of the present application, the electrode group consisting of the positive electrode and the negative electrode is first fully immersed in a carbonate solution. By utilizing the slight solubility of carbonate solutions such as sodium bicarbonate or ammonium bicarbonate in aluminum, the aluminum foil in the electrode and the carbonate are slightly dissolved, and at this time, fine cracks can be generated between the aluminum foil and the powder; after aging and compacting the soaked electrode group, it is further calcined to obtain a calcined material and a calcined gas, so that the carbonate can decompose to produce a large amount of carbon dioxide gas. The large amount of gas generated in a short time acts on the fine cracks, causing stress expansion in the fine cracks, thereby intensifying the separation of the powder and the foil; the calcined material can be subjected to simple separation treatments such as grinding and screening to obtain high-purity powder and complete copper and aluminum foil. The powder is post-treated to obtain a lithium carbonate salt product, wherein the powder recovery rate can reach more than 98.5%, and the purity of the lithium carbonate salt product obtained after the powder is post-treated can reach more than 99.2%.

[0035] As mentioned above, the roasting gas generated by the roasting process is mainly composed of carbon dioxide and carbon monoxide, wherein carbon monoxide is obtained by carbon reduction of carbon dioxide and carbon in the negative electrode graphite. The reduced carbon monoxide in the form of gas is more conducive to the further reduction of the lithium-containing oxide in the positive electrode sheet. During the roasting process, the lithium element is converted into more active lithium oxide or lithium element, and finally lithium carbonate is generated under the action of carbon dioxide, which is conducive to the subsequent purification of lithium carbonate salt. In the post-processing of the powder, this part of the roasting gas can be used as a carbon source gas to cause the lithium carbonate in the powder to mix with water to undergo a carbonization reaction to generate lithium bicarbonate with higher solubility. After filtering this part of the mixed slurry containing lithium salt, the impurity elements are filtered out in the form of leaching residue, while the lithium element is retained in the filtrate in the form of lithium bicarbonate to achieve the separation of lithium and other impurity elements; the lithium bicarbonate is further heated and decomposed to generate lithium carbonate with lower solubility, and a high-purity lithium carbonate salt product can be obtained after separation and filtration.

[0036] Based on the above general inventive concept, a powder recovery method is designed, which mainly includes the following steps:

[0037] S1. Disassemble the lithium battery to obtain the positive electrode sheet and the negative electrode sheet, and combine the positive electrode sheet and the negative electrode sheet to obtain an electrode sheet group;

[0038] S2. Infiltrating the electrode assembly with a carbonate solution, and calcining the infiltrated electrode assembly to obtain a calcined material and a calcined gas;

[0039] S3, separating the calcined material to obtain powder and foil;

[0040] S4. Post-processing the powder to obtain a lithium carbonate salt product.

[0041] It can be understood that the present invention makes full use of the characteristics of carbonate solubility and thermal decomposition of aluminum to achieve the separation of foil and pole powder under complete pole pieces. Since no crushing step is required, the production of fine aluminum particles such as aluminum powder and aluminum chips is avoided, the impurities in the recovered powder are greatly reduced, and the foil product is more complete and conducive to further separation; the foil separation and lithium reduction roasting are achieved under the conditions of one heat treatment, and the process of pretreatment and preferential lithium extraction is simplified; the generated carbon dioxide can be further used in lithium salt purification, saving energy and the use of auxiliary materials, and helping to reduce production costs.

[0042] In an optional solution of an embodiment of the present invention, when the positive electrode sheets and negative electrode sheets obtained by disassembling and recycling lithium batteries are combined, they can be cross-stacked and then folded before being combined, so that stress fracture occurs directly at the creases obtained by folding during baking, thereby improving the separation degree between the powder and the foil.

[0043] It should be noted that when combining the positive and negative electrode sheets, a single positive electrode sheet and a single negative electrode sheet can be cross-stacked and then folded to form a electrode sheet assembly, or multiple positive electrode sheets and multiple negative electrode sheets can be cross-stacked and then folded to form a electrode sheet assembly. The number of positive electrode sheets and negative electrode sheets in the electrode sheet assembly can be single or multiple. When multiple positive electrode sheets and multiple negative electrode sheets are cross-stacked, it is preferred to stack a single positive electrode sheet and a single negative electrode sheet one by one and then fold the entire assembly. The width of the electrode sheet assembly obtained after folding is maintained within the range of 2 to 5 cm, and the thickness is maintained within the range of 5 to 10 cm to ensure that the folds are fully formed and improve the peeling effect when the stress expansion is used to promote the subsequent peeling of the powder.

[0044] The details are described below through specific examples.

[0045] [Example 1]

[0046] Disassembling a nickel-cobalt-manganese lithium battery to obtain positive and negative electrode sheets, stacking the positive and negative electrode sheets one by one, and folding each stacked positive and negative electrode sheet into a strip with a width of 4 cm and a thickness of 10 cm to obtain an electrode sheet assembly containing both positive and negative electrode sheets. Folding the positive and negative electrode sheets facilitates stress fracture at the fold during subsequent calcination, promoting the separation of the powder from the aluminum foil.

[0047] The folded electrode assembly is placed upright and immersed in a saturated sodium bicarbonate solution pool for 5 minutes. The positive and negative electrodes soaked in the saturated sodium bicarbonate solution are transferred to a 40°C environment for aging for 4 hours to allow the sodium bicarbonate solution to fully infiltrate the electrodes, allowing the aluminum foil and powder to react and form fine cracks. The aged electrodes are compacted until there are no obvious gaps between the electrodes in the electrode assembly, and excess air and moisture between the positive and negative electrodes in the electrode assembly are removed. This allows a large amount of baking gas to be generated in a short period of time during baking, thereby accelerating the peeling of the powder and the aluminum foil.

[0048] The compacted electrode assembly is calcined in an airtight environment to obtain calcined material and calcined gas. The calcination temperature is 650°C and the calcination time is 4 hours. A large amount of calcined gas generated in a short period of time acts on the fine cracks between the powder and the aluminum foil, causing stress expansion in the cracks and intensifying the separation of the powder and the aluminum foil. At the same time, the calcined gas generated by the calcination process contains carbon dioxide generated by the high-temperature decomposition of sodium bicarbonate, and carbon monoxide generated by the reaction of carbon dioxide with graphite in the negative electrode. The carbon monoxide gas further reduces the lithium oxide in the positive electrode, and lithium carbonate is generated under the action of carbon dioxide. After the calcination process, the folded electrode assembly is opened, and the front of the electrode assembly is flattened in 10 layers. After the flattened electrode assembly is milled with a roller, it is sieved with a 40-mesh sieve to obtain powder and complete copper foil and aluminum foil.

[0049] The powder obtained by screening is ball-milled with zirconium balls, and the proportion of materials ground to less than 0.038 mm is more than 75%; the ball-milled powder is added to water to obtain a mixed solution, and the mass ratio of powder to water is 1:30; the roasting gas generated after the roasting treatment is continuously introduced into the mixed solution, and a carbonization reaction is carried out under stirring to obtain a mixed slurry, the carbonization reaction temperature is 30°C, and the reaction time is 3h; during the carbonization reaction, the lithium carbonate obtained in the powder by the action of the roasting gas reacts with carbon dioxide to generate lithium bicarbonate with high solubility; the mixed slurry after the carbonization reaction is filtered to obtain leaching residue and filtrate, the filtrate retains lithium bicarbonate, and the lithium element and impurity elements are separated. The leaching residue is further subjected to leaching extraction treatment to extract cobalt, nickel, manganese and other elements; the filtrate is heated and stirred to decompose the highly soluble lithium bicarbonate into low-solubility lithium carbonate, thereby obtaining precipitated lithium carbonate crystals, the temperature of the heating and stirring treatment is controlled at 90°C, and the filtrate is further filtered and separated, and washed with hot water to obtain a lithium carbonate salt product.

[0050] [Example 2]

[0051] The lithium iron phosphate battery is disassembled to obtain the positive and negative electrode sheets, which are stacked one on top of the other. The two stacked positive and negative electrode sheets are folded into a strip with a width of 2 cm, and the thickness of each strip is 8 cm, thereby obtaining a sheet assembly containing both the positive and negative electrode sheets. Folding the positive and negative electrode sheets facilitates stress fracture at the fold during subsequent calcination, thereby promoting the separation of the powder from the aluminum foil.

[0052] The folded electrode assembly is placed upright, and the treated electrode assembly is soaked in a mixed solution of saturated sodium bicarbonate and saturated ammonium bicarbonate in a mass ratio of 8:2, until the mixed solution completely covers the electrode assembly; the soaked mixed electrode assembly is transferred to a 25°C environment for aging for 5 hours, so that the sodium bicarbonate solution fully infiltrates the electrode, so that the aluminum foil and the powder react to form fine cracks; the aged electrode assembly is compacted until there are no obvious gaps between the electrode sheets in the electrode assembly, so as to remove excess air and moisture between the positive and negative electrode sheets in the electrode assembly, so that a large amount of baking gas can be generated in a short time during baking, thereby accelerating the peeling of the powder and the aluminum foil;

[0053] The compacted electrode group is calcined in an air-tight environment to obtain calcined materials and calcined gas. The calcination temperature is 600°C and the calcination time is 6 hours. A large amount of calcined gas generated in a short period of time acts on the fine cracks between the powder and the aluminum foil, causing stress expansion in the cracks and intensifying the separation of the powder and the aluminum foil. At the same time, the calcined gas generated by the calcination process contains carbon dioxide generated by the high-temperature decomposition of sodium bicarbonate, and carbon monoxide generated by the reaction of carbon dioxide with graphite in the negative electrode. The carbon monoxide gas further reduces the lithium oxide in the positive electrode to generate lithium carbonate under the action of carbon dioxide. After the calcination process, the folded electrode group is opened and the front of the electrode group is flattened to prevent the foil from breaking during grinding. The number of flattened layers is 10. After the flattened electrode group is milled with a roller, it is sieved with a 40-mesh sieve to obtain powder and complete copper foil and aluminum foil.

[0054] The powder obtained by screening is ball-milled with ceramic balls, and the proportion of materials ground to less than 0.074 mm is more than 75%; the ball-milled powder is added to water to obtain a mixed solution, and the mass ratio of powder to water is 1:30; the roasting gas generated after the roasting treatment is continuously introduced into the mixed solution, and a carbonization reaction is carried out under stirring to obtain a mixed slurry, the carbonization reaction temperature is 30°C, and the reaction time is 3h; during the carbonization reaction, the lithium carbonate obtained in the powder by the action of the roasting gas reacts with carbon dioxide to generate lithium bicarbonate with high solubility; the mixed slurry after the carbonization reaction is filtered to obtain leaching residue and filtrate, the filtrate retains lithium bicarbonate, and the lithium element and impurity elements are separated. The leaching residue is further subjected to leaching extraction treatment to extract iron phosphate in the material; the filtrate is heated and stirred to decompose the highly soluble lithium bicarbonate into low-solubility lithium carbonate, thereby obtaining precipitated lithium carbonate crystals, and the temperature of the heating and stirring treatment is controlled at 90°C. The filtrate is further filtered and separated, and washed with hot water to obtain a lithium carbonate salt product.

[0055] [Example 3]

[0056] Disassemble the nickel-cobalt-manganese lithium battery to obtain the positive and negative electrode sheets, stack the positive and negative electrode sheets one by one, and fold each sheet into a long strip with a width of 5 cm, with a thickness of 5 cm, to obtain a sheet assembly containing both the positive and negative electrode sheets. Folding the positive and negative electrode sheets facilitates stress fracture at the fold during subsequent baking, promoting the separation of the powder and the aluminum foil.

[0057] The folded electrode assembly is placed upright, and the treated electrode assembly is soaked in a saturated mixed solution of sodium bicarbonate and sodium carbonate in a mass ratio of 8:2, until the mixed solution completely covers the electrode assembly; the soaked mixed electrode assembly is transferred to a 40°C environment for aging for 6 hours, so that the sodium bicarbonate solution fully infiltrates the electrode, so that the aluminum foil and the powder react to form fine cracks; the aged electrode assembly is compacted until there are no obvious gaps between the electrode sheets in the electrode assembly, so as to remove excess air and moisture between the positive and negative electrode sheets in the electrode assembly, so that a large amount of baking gas can be generated in a short time during baking, thereby accelerating the peeling of the powder and the aluminum foil;

[0058] The compacted electrode group is calcined in an air-tight environment to obtain calcined materials and calcined gas. The calcination temperature is 620°C and the calcination time is 4 hours. A large amount of calcined gas generated in a short period of time acts on the fine cracks between the powder and the aluminum foil, causing stress expansion in the cracks and intensifying the separation of the powder and the aluminum foil. At the same time, the calcined gas generated by the calcination process contains carbon dioxide generated by the high-temperature decomposition of sodium bicarbonate, and carbon monoxide generated by the reaction of carbon dioxide with graphite in the negative electrode. The carbon monoxide gas further reduces the lithium oxide in the positive electrode to generate lithium carbonate under the action of carbon dioxide. After the calcination process, the folded electrode group is opened and the front of the electrode group is flattened to prevent the foil from breaking during grinding. The number of flattened layers is 15. After the flattened electrode group is milled with a roller, it is sieved with a 40-mesh sieve to obtain powder and complete copper foil and aluminum foil.

[0059] The powder obtained by screening is ball-milled with rubber balls, and the proportion of materials ground to less than 0.074 mm is more than 75%; the ball-milled powder is added to water to obtain a mixed solution, and the mass ratio of powder to water is 1:40; the roasting gas generated after the roasting treatment is continuously introduced into the mixed solution, and a carbonization reaction is carried out under stirring to obtain a mixed slurry, the carbonization reaction temperature is 25°C, and the reaction time is 2h; during the carbonization reaction, the lithium carbonate obtained in the powder by the action of the roasting gas reacts with carbon dioxide to generate lithium bicarbonate with high solubility; the mixed slurry after the carbonization reaction is filtered to obtain leaching residue and filtrate, the filtrate retains lithium bicarbonate, and the lithium element and impurity elements are separated. The leaching residue is further subjected to leaching extraction treatment to extract iron phosphate in the material; the filtrate is heated and stirred to decompose the highly soluble lithium bicarbonate into low-solubility lithium carbonate, thereby obtaining precipitated lithium carbonate crystals, and the temperature of the heating and stirring treatment is controlled at 80°C. The filtrate is further filtered and separated, and washed with hot water to obtain a lithium carbonate salt product.

[0060] [Example 4]

[0061] Disassembling a nickel-cobalt-manganese lithium battery to obtain positive and negative electrode sheets, stacking the positive and negative electrode sheets one by one, and folding each stacked positive and negative electrode sheet into a strip with a width of 3 cm, and a single folded strip with a thickness of 10 cm to obtain a electrode sheet assembly containing both positive and negative electrode sheets; folding the positive and negative electrode sheets facilitates stress fracture at the fold during subsequent baking, promoting the separation of the powder and the aluminum foil;

[0062] The folded electrode group is placed upright, and the treated electrode group is sprayed with a supersaturated mixed solution of sodium bicarbonate and sodium carbonate in a mass ratio of 9:1, until the mixed solution completely covers the electrode group; the sprayed mixed electrode group is transferred to a 45°C environment for aging for 2 hours, so that the sodium bicarbonate solution fully infiltrates the electrode, so that the aluminum foil and the powder react to form fine cracks; the aged electrode group is compacted until there are no obvious gaps between the electrode groups in the electrode group, so as to remove excess air and moisture between the positive and negative electrode groups in the electrode group, so that a large amount of baking gas can be generated in a short time during baking, thereby accelerating the peeling of the powder and the aluminum foil;

[0063] The compacted electrode group is calcined in an air-tight environment to obtain calcined materials and calcined gas. The calcination temperature is 700°C and the calcination time is 4 hours. A large amount of calcined gas generated in a short period of time acts on the fine cracks between the powder and the aluminum foil, causing stress expansion in the cracks and intensifying the separation of the powder and the aluminum foil. At the same time, the calcined gas generated by the calcination process contains carbon dioxide generated by the high-temperature decomposition of sodium bicarbonate, and carbon monoxide generated by the reaction of carbon dioxide with graphite in the negative electrode. The carbon monoxide gas further reduces the lithium oxide in the positive electrode to generate lithium carbonate under the action of carbon dioxide. After the calcination process, the folded electrode group is opened and the front of the electrode group is flattened to prevent the foil from breaking during grinding. The number of flattened layers is 20. After the flattened electrode group is milled with a roller, it is sieved with a 40-mesh sieve to obtain powder and complete copper foil and aluminum foil.

[0064] The powder obtained by screening is ball-milled with silica gel balls, and the proportion of materials ground to less than 0.074 mm is more than 75%; the ball-milled powder is added to water to obtain a mixed solution, and the mass ratio of powder to water is 1:45; the roasting gas generated after the roasting treatment is continuously introduced into the mixed solution, and a carbonization reaction is carried out under stirring to obtain a mixed slurry, the carbonization reaction temperature is 40°C, and the reaction time is 1 hour; during the carbonization reaction, the lithium carbonate obtained in the powder by the action of the roasting gas reacts with carbon dioxide to generate lithium bicarbonate with high solubility; the mixed slurry after the carbonization reaction is filtered to obtain leaching residue and filtrate, the filtrate retains lithium bicarbonate, and the lithium element and impurity elements are separated. The leaching residue is further subjected to leaching extraction treatment to extract iron phosphate in the material; the filtrate is heated and stirred to decompose the highly soluble lithium bicarbonate into low-solubility lithium carbonate, thereby obtaining precipitated lithium carbonate crystals, and the temperature of the heating and stirring treatment is controlled at 85°C. The filtrate is further filtered and separated, and washed with hot water to obtain a lithium carbonate salt product.

[0065] [Comparative Example 1]

[0066] Disassemble the nickel-cobalt-manganese lithium battery to obtain the positive electrode sheet and the negative electrode sheet, crush the positive electrode sheet and the negative electrode sheet into 0.07mm-0.15mm pieces to obtain electrode sheet scraps;

[0067] The electrode pieces were calcined in an airtight environment to obtain calcined materials and calcined gas. The calcination temperature was 650°C and the calcination time was 4 hours. After calcination, the electrode pieces were flattened on the front side in 10 layers. The flattened electrode pieces were milled with a roller and sieved with a 40-mesh sieve to obtain powder.

[0068] The powder obtained by screening is ball-milled with zirconium balls, and the proportion of materials ground to less than 0.038 mm is more than 75%; the ball-milled powder is added to water to obtain a mixed solution, and the mass ratio of powder to water is 1:30; the roasting gas generated after the roasting treatment is continuously introduced into the mixed solution, and a carbonization reaction is carried out under stirring to obtain a mixed slurry, the carbonization reaction temperature is 30°C, and the reaction time is 3h; the mixed slurry after the carbonization reaction is filtered to obtain leaching residue and filtrate, lithium bicarbonate is retained in the filtrate, and the separation of lithium element and impurity elements is achieved. The leaching residue is further subjected to leaching extraction treatment to extract cobalt, nickel, manganese and other elements; the filtrate is heated and stirred to decompose the highly soluble lithium bicarbonate into low-solubility lithium carbonate, thereby obtaining precipitated lithium carbonate crystals, and the temperature of the heating and stirring treatment is controlled at 90°C. The filtrate is further filtered and separated, and washed with hot water to obtain a lithium carbonate salt product.

[0069] [Comparative Example 2]

[0070] Disassembling a nickel-cobalt-manganese lithium battery to obtain positive and negative electrode sheets, stacking the positive and negative electrode sheets one by one, and folding each stacked positive and negative electrode sheet into a strip with a width of 4 cm and a thickness of 10 cm to obtain an electrode sheet assembly containing both positive and negative electrode sheets. Folding the positive and negative electrode sheets facilitates stress fracture at the fold during subsequent calcination, promoting the separation of the powder from the aluminum foil.

[0071] The folded electrode group is placed upright and the treated electrode group is soaked in water for 5 minutes. The soaked positive and negative electrodes are transferred to a 40°C environment for aging for 4 hours to allow the water to fully infiltrate the electrodes and form fine cracks between the aluminum foil and the powder. The aged electrodes are compacted until there are no obvious gaps between the electrodes in the electrode group, and excess air and moisture between the positive and negative electrodes in the electrode group are removed, so that a large amount of baking gas can be generated in a short time during baking, thereby accelerating the peeling of the powder and the aluminum foil.

[0072] The compacted electrode assembly is calcined in an airtight environment to obtain calcined material and calcined gas. The calcination temperature is 650°C and the calcination time is 4 hours. A large amount of calcined gas generated in a short period of time acts on the fine cracks between the powder and the aluminum foil, causing stress expansion in the cracks and intensifying the separation of the powder and the aluminum foil. At the same time, the calcined gas generated by the calcination process contains carbon dioxide generated by the high-temperature decomposition of sodium bicarbonate, and carbon monoxide generated by the reaction of carbon dioxide with graphite in the negative electrode. The carbon monoxide gas further reduces the lithium oxide in the positive electrode, and lithium carbonate is generated under the action of carbon dioxide. After the calcination process, the folded electrode assembly is opened, and the front of the electrode assembly is flattened in 10 layers. After the flattened electrode assembly is milled with a roller, it is sieved with a 40-mesh sieve to obtain powder and complete copper foil and aluminum foil.

[0073] The powder obtained by screening is ball-milled with zirconium balls, and the proportion of materials ground to less than 0.038 mm is more than 75%; the ball-milled powder is added to water to obtain a mixed solution, and the mass ratio of powder to water is 1:30; the roasting gas generated after the roasting treatment is continuously introduced into the mixed solution, and a carbonization reaction is carried out under stirring to obtain a mixed slurry, the carbonization reaction temperature is 30°C, and the reaction time is 3h; during the carbonization reaction, the lithium carbonate obtained in the powder by the action of the roasting gas reacts with carbon dioxide to generate lithium bicarbonate with high solubility; the mixed slurry after the carbonization reaction is filtered to obtain leaching residue and filtrate, the filtrate retains lithium bicarbonate, and the lithium element and impurity elements are separated. The leaching residue is further subjected to leaching extraction treatment to extract cobalt, nickel, manganese and other elements; the filtrate is heated and stirred to decompose the highly soluble lithium bicarbonate into low-solubility lithium carbonate, thereby obtaining precipitated lithium carbonate crystals, the temperature of the heating and stirring treatment is controlled at 90°C, and the filtrate is further filtered and separated, and washed with hot water to obtain a lithium carbonate salt product.

[0074] [Comparative Example 3]

[0075] Disassemble the nickel-cobalt-manganese lithium battery to obtain the positive and negative electrodes. Stack the entire positive and negative electrodes one by one, with the two stacked positive and negative electrodes as one. Place the stacked electrode group upright and soak the treated electrode group in a saturated sodium bicarbonate solution pool for 5 minutes. Transfer the positive and negative electrodes soaked in saturated sodium bicarbonate solution to a 40°C environment for aging for 4 hours to allow the sodium bicarbonate solution to fully infiltrate the electrodes, allowing the aluminum foil and powder to react and form fine cracks. Compact the aged electrodes until there are no obvious gaps between the electrodes in the electrode group. Exclude excess air and moisture between the positive and negative electrodes in the electrode group, so that a large amount of baking gas can be generated in a short time during baking, thereby accelerating the peeling of the powder and the aluminum foil.

[0076] The compacted electrode assembly is calcined in an airtight environment to obtain calcined material and calcined gas. The calcination temperature is 650°C and the calcination time is 4 hours. A large amount of calcined gas generated in a short period of time acts on the fine cracks between the powder and the aluminum foil, causing stress expansion in the cracks and intensifying the separation of the powder and the aluminum foil. At the same time, the calcined gas generated by the calcination process contains carbon dioxide generated by the high-temperature decomposition of sodium bicarbonate, and carbon monoxide generated by the reaction of carbon dioxide with graphite in the negative electrode. The carbon monoxide gas further reduces the lithium oxide in the positive electrode, and lithium carbonate is generated under the action of carbon dioxide. After the calcination process, the folded electrode assembly is opened, and the front of the electrode assembly is flattened in 10 layers. After the flattened electrode assembly is milled with a roller, it is sieved with a 40-mesh sieve to obtain powder and complete copper foil and aluminum foil.

[0077] The powder obtained by screening is ball-milled with zirconium balls, and the proportion of materials ground to less than 0.038 mm is more than 75%; the ball-milled powder is added to water to obtain a mixed solution, and the mass ratio of powder to water is 1:30; the roasting gas generated after the roasting treatment is continuously introduced into the mixed solution, and a carbonization reaction is carried out under stirring to obtain a mixed slurry, the carbonization reaction temperature is 30°C, and the reaction time is 3h; during the carbonization reaction, the lithium carbonate obtained in the powder by the action of the roasting gas reacts with carbon dioxide to generate lithium bicarbonate with high solubility; the mixed slurry after the carbonization reaction is filtered to obtain leaching residue and filtrate, the filtrate retains lithium bicarbonate, and the lithium element and impurity elements are separated. The leaching residue is further subjected to leaching extraction treatment to extract cobalt, nickel, manganese and other elements; the filtrate is heated and stirred to decompose the highly soluble lithium bicarbonate into low-solubility lithium carbonate, thereby obtaining precipitated lithium carbonate crystals, the temperature of the heating and stirring treatment is controlled at 90°C, and the filtrate is further filtered and separated, and washed with hot water to obtain a lithium carbonate salt product.

[0078] The impurity content of the powders after ball milling in Examples 1 to 4 and Comparative Examples 1 to 3 was tested and the recovery rate was calculated. The results are shown in the following Appendix 1. The components of the lithium carbonate products obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were tested. The results are shown in the following Appendix 2. The lithium content of the leaching residues and filtrates in Examples 1 to 4 and Comparative Examples 1 to 3 was determined. The results are shown in the following Appendix 3.

[0079] Appendix 1 Powder recovery rate and element content statistics

[0080]

[0081] Note: The unit of Co, Ni, Li, Fe, Cu, Al and F in Appendix 1 is %.

[0082] Appendix 2 Statistical table of component content (%) of lithium carbonate products

[0083]

[0084] Appendix 3 Statistical table of lithium content determination of leaching residue and filtrate

[0085]

[0086] Through the above Appendix 1 to 3, it can be concluded that: in Appendix 1, the recovery rate of the powder products recovered in Examples 1 to 4 is all above 97.5%, and the content of metal impurities such as Cu and Al introduced by the foil in the powder is kept below 0.13%. The purity of the powder products obtained in Examples 1 to 4 is kept at a high level, and the impurity content is low, which is conducive to the subsequent recovery of lithium carbonate products; in Appendix 2, since the foil does not need to be crushed in the present invention, the aluminum foil is separated completely, the powder purity is high, and the lithium element generates highly soluble lithium bicarbonate during the carbonization treatment, which achieves a high degree of separation of lithium element and impurity elements. 1 to 4 further recovered the lithium carbonate component in the lithium carbonate salt product obtained from the powder as high as 99% or more, the total impurity content is less than 1%, and the recovered lithium carbonate salt product has high purity; in Appendix 3, the lithium content in the filtrate produced in Examples 1 to 4 is 9.2 g / L to 10.2 g / L, the lithium content in the filtrate is low, and the lithium content in the leached residue is less than 0.1%, and the lithium content in the leached residue is also low, thereby verifying that a large amount of lithium in the lithium batteries of Examples 1 to 4 is recovered in the form of lithium carbonate salt products, the recovery rate of lithium element is high, and the recovered lithium carbonate salt product has high purity;

[0087] In Comparative Example 1 provided by the present invention, the electrode is crushed. Compared with Examples 1 to 4, the recovery rate of the recovered powder in Comparative Example 1 is lower, and the content of metal impurities such as Cu and Al introduced by the foil is higher. After the electrode is crushed, a large amount of fine-particle aluminum is produced, resulting in a high content of aluminum impurities in the powder, and the complete foil cannot be recovered. The lithium carbonate in the lithium carbonate salt obtained by subsequent treatment of the powder is lower than that in Examples 1 to 4. A large amount of lithium element exists in the leaching residue, which is not conducive to the efficient recovery of the lithium carbonate salt product.

[0088] The difference between Comparative Example 2 provided by the present invention and Examples 1 to 4 is that the electrode group is not infiltrated with a carbonate solution, but is infiltrated with water. The recovery rate of the powder is lower than that of Examples 1 to 4, and the Al impurity content in the powder is higher; the carbonate solution can promote the peeling of the electrode and the powder, reduce the powder residue on the electrode, and improve the powder recovery rate. Since Comparative Example 2 does not use a carbonate solution to infiltrate the electrode group, there is a lot of powder residue on the electrode, the powder recovery rate is low, and the lithium carbonate component content in the lithium carbonate salt is further lower.

[0089] Compared with Examples 1 to 4, the comparative example 3 provided by the present invention does not fold the electrode sheets but only stacks them together, so that the electrode group has no creases. During roasting, the stress expansion generated by the gas is not applied to the creases, resulting in poor powder peeling effect. The recovery rate of the powder in comparative example 3 is lower than that in Examples 1 to 4, only 96.40%, which reduces the recovery rate of lithium carbonate in the subsequently recovered lithium carbonate salt.

[0090] In embodiments 1 to 4 of the present invention, nickel-cobalt-manganese lithium batteries or lithium iron phosphate batteries are used as waste batteries to perform powder recovery and lithium carbonate recovery. The recovered powder has high purity and recovery rate, and a complete foil can be obtained. The lithium oxide is reduced simultaneously through a single roasting, and the powder and foil are separated, thereby optimizing the subsequent recovery process of the lithium carbonate product from the powder. The lithium element is lost at low loss during the recovery process, and the recovered lithium carbonate has high purity.

[0091] It should be noted that the "lithium battery" in the present invention can be a nickel-cobalt-manganese ternary lithium battery, a lithium iron phosphate battery or a lithium cobalt oxide battery, or a lithium ion battery such as a lithium manganese oxide battery or a nickel-cobalt-aluminum oxide battery. The nickel-cobalt-manganese battery and lithium iron phosphate battery provided in the embodiments of this application are only examples and do not limit the type of lithium battery.

[0092] In summary, the powder recovery method provided by the embodiment of the present invention realizes the separation of aluminum foil and powder under the complete electrode, and the present invention does not need to crush the electrode, avoids the generation of fine-particle aluminum, greatly reduces the impurity content in the powder, thereby improving the recovery rate and product purity of lithium carbonate salt, and the recovered aluminum foil is more complete; the present invention realizes the stripping of powder and the reduction roasting of lithium in the powder at the same time under the condition of one heat treatment, so that the recycling process of waste lithium batteries is simplified; the generated roasting gas can be used in the purification of lithium carbonate salt, saving the use of energy auxiliary materials and reducing production costs.

[0093] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for recycling powder of battery pole pieces, characterized in that: The following steps are involved: Disassembling the lithium battery to obtain a positive electrode sheet and a negative electrode sheet, and combining the positive electrode sheet and the negative electrode sheet to obtain an electrode sheet group; Infiltrating the electrode assembly with a carbonate solution, and calcining the infiltrated electrode assembly to obtain a calcined material and a calcined gas; Separating the calcined material to obtain powder and foil; Wherein, the calcination treatment is carried out in an air-tight environment, the calcination temperature is 600° C. to 700° C.; and / or the components of the calcination gas include carbon dioxide and carbon monoxide.

2. The powder recovery method according to claim 1, characterized in that: The combination is: The positive electrode sheet and the negative electrode sheet are folded to obtain the electrode sheet group.

3. The powder recovery method according to claim 2, characterized in that: In the electrode assembly, the positive electrode sheet and the negative electrode sheet are stacked and then folded. The electrode assembly after folding has a width of 2 to 5 cm and a thickness of 5 to 10 cm.

4. The powder recovery method according to claim 3, characterized in that: The positive electrode sheet and the negative electrode sheet are stacked in a cross-stacked manner.

5. The powder recovery method according to claim 1, characterized in that: The carbonate solution includes at least one of sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate solution or ammonium bicarbonate solution.

6. The powder recovery method according to claim 1, characterized in that: In the step of baking the electrode assembly after soaking, Before the calcination, the electrode assembly after the infiltration is subjected to an aging treatment; The electrode assembly after the aging treatment is compacted.

7. The powder recovery method according to claim 6, characterized in that: The aging temperature of the aging treatment is controlled to be 25°C to 45°C, and the aging time is 2 to 6 hours; and / or The calcination time of the calcination treatment is 4 to 6 hours.

8. The powder recovery method according to claim 1, characterized in that: The calcined material is separated and processed. The separation process includes at least one grinding process and at least one screening process; The calcined material is flattened and then subjected to the separation process, wherein the number of flattened layers of the electrode pieces in the calcined material is 10 to 20 layers; After the screening process, an oversize material and an undersize material are obtained, wherein the oversize material includes the foil material, and the undersize material includes the powder.

9. The powder recovery method according to claim 1, characterized in that: Also includes: The powder is post-processed to obtain a lithium carbonate salt product.

10. The powder recovery method according to claim 9, characterized in that: The post-processing includes: ball-milling the powder to obtain a ball-milled powder, mixing the ball-milled powder with water, and then introducing a carbon source gas and / or the roasting gas to perform a carbonization reaction to obtain a mixed slurry containing a lithium salt; filtering the mixed slurry containing the lithium salt to obtain leaching residue and filtrate; The filtrate is subjected to heating, stirring, filtering and separation treatments to obtain a lithium carbonate salt product.

11. The powder recovery method according to claim 10, characterized in that: The carbon source gas is carbon dioxide.

12. The powder recovery method according to claim 10, characterized in that: During the ball milling process, the proportion of the material ball-milled to a powder particle size of 0.074 mm or less is more than 75%; and / or When the ball-milled powder is mixed with water, the mass ratio of the powder to water is controlled to be 1:(25-45); and / or The temperature of the carbonization reaction is controlled to be 25° C. to 40° C., and the reaction time of the carbonization reaction is 1 to 3 hours; and / or The temperature of the heating and stirring treatment is controlled at 80°C to 90°C.

Images