A method for preparing positive electrode active material

Abstract

The present application provides a method for preparing a positive electrode active material, a positive electrode active material, a positive electrode plate, a secondary battery and an electric device. The method for preparing a positive electrode active material comprises the following steps: discharging a waste nickel cobalt manganese oxide lithium secondary battery, drying and disassembling to obtain a positive electrode plate, and roasting to remove impurities; dissolving the obtained positive electrode plate with acid, filtering to obtain a mixed solution, adding a metal salt to adjust the molar ratio of the metal elements, causing a coprecipitation reaction in an alkaline solution, and filtering to obtain a nickel cobalt manganese aluminum oxide lithium precursor; recrystallizing the filtrate to obtain lithium hydroxide; and roasting the nickel cobalt manganese aluminum oxide lithium positive electrode active material after mixing the nickel cobalt manganese aluminum oxide lithium precursor with lithium hydroxide. The method for preparing a positive electrode active material provided by the present application eliminates the step of separating the active substance and the aluminum foil, simplifies the recycling method, and improves the recycling efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a method for preparing a positive electrode active material, a positive electrode active material, a positive electrode sheet, a secondary battery, and an electrical device. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have characteristics such as high specific energy, high working voltage, low self-discharge rate, small size, and light weight, and are widely used in products such as electric vehicles and electronic devices. Layered Li[Ni x Co y Mn 1-x-y O2 (0 < x < 1, 0 < y < 1, 0 < 1 - x - y < 1) has been widely studied as a positive electrode active material for secondary batteries. Due to its low cost and high capacity, it is considered to be one of the most promising positive electrode active materials to meet the requirements of electric vehicles (EVs) and hybrid electric vehicles. The rapid growth in the demand for secondary batteries is the direct cause of the soaring prices of raw materials such as nickel, cobalt, and manganese ores. Therefore, the recycling of waste nickel cobalt manganese oxide lithium batteries is extremely urgent.

[0003] The recycling process of lithium nickel cobalt manganese oxide is usually a mechanical crushing and separation method. However, in this process, the active substances are not completely separated, and foil debris is mixed into the active substances, resulting in additional impurity removal steps in the subsequent process. Therefore, the existing recycling process of lithium nickel cobalt manganese oxide still needs to be improved. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to simplify the recycling method of nickel cobalt manganese oxide lithium batteries and improve the recycling efficiency.

[0005] To achieve the above object, the present application provides a method for preparing a positive electrode active material, a positive electrode active material, a positive electrode sheet, a secondary battery, and an electrical device.

[0006] The first aspect of the present application provides a method for preparing a positive electrode active material, including the following steps:

[0007] (1) Discharging a waste nickel cobalt manganese oxide (NCM) secondary battery in a saturated aqueous solution of sodium chloride for 1 to 3 days, drying and disassembling to obtain a positive electrode sheet;

[0008] (2) Roasting the positive electrode sheet obtained in step (1) in a flowing air atmosphere to remove conductive carbon and binder;

[0009] (3) Placing the positive electrode sheet obtained in step (2) into a soaking tank, adding an acid solution and a reducing substance to the soaking tank and reacting until the positive electrode current collector is completely dissolved. After the reaction ends, filtering to obtain a mixed solution containing nickel, manganese, cobalt, aluminum, and lithium elements;

[0010] (4) adding nickel salt, cobalt salt and manganese salt to the mixed solution, adjusting the molar ratio of nickel, cobalt, manganese and aluminum elements to obtain a mixed salt solution, further coprecipitating in sodium hydroxide and ammonia water, filtering and obtaining a nickel cobalt manganese aluminum oxide (NCMA) precursor, wherein the nickel cobalt manganese aluminum oxide precursor satisfies (Ni t Co u Mn v Al w )(OH)2, where 0.5≤t<1, 0≤u≤0.5, 0≤v≤0.5, 0≤w≤0.3, and t+u+v+w=1;

[0011] (5) evaporating the solvent from the filtrate obtained in step (4) at 50° C.-80° C., recrystallizing, and drying to obtain lithium hydroxide powder;

[0012] (6) The nickel cobalt manganese aluminum oxide precursor and the lithium hydroxide powder are uniformly mixed in a molar ratio of 1:1.03-1:1.2, calcined in an oxygen atmosphere, crushed, sieved, and demagnetized to obtain a nickel cobalt manganese aluminum oxide positive electrode active material.

[0013] Therefore, the present application simplifies the recycling method by placing the calcined positive electrode sheet into a soaking tank to dissolve it with acid after calcining, thereby eliminating the step of separating the active substance and the aluminum foil, and fully recovering the aluminum element in the aluminum foil, thereby improving the recycling efficiency.

[0014] In any embodiment, the positive electrode active material of the waste nickel cobalt manganese oxide lithium secondary battery conforms to the general formula Li(Ni x Co y Mn z )O2, where 0.5≤x<1, 0≤y≤0.5, 0≤z≤0.5, and x+y+z=1, can provide nickel, manganese, cobalt, aluminum, and lithium elements to improve the recovery efficiency.

[0015] In any embodiment, the drying temperature is 50° C.-80° C., and the drying time is 8 h-12 h, which can prevent the sodium chloride solution from mixing into the reaction system, reduce the loss of aluminum foil, and improve the recovery efficiency.

[0016] In any embodiment, the calcination temperature in the flowing air atmosphere is 400°C-600°C, and the calcination time is 3h-8h, which can fully carbonize impurities such as conductive carbon and binder, and further be removed by the flowing air, thereby reducing the loss of aluminum foil.

[0017] In any embodiment, the acid solution includes one or more of sulfuric acid, hydrochloric acid, nitric acid, citric acid, acetic acid, maleic acid, oxalic acid, lactic acid, aspartic acid, and ascorbic acid, and the reducing substance includes one or more of sulfite, bisulfite, and thiosulfate. By using the above-mentioned acid solution and reducing substance in combination, the positive electrode current collector can be dissolved, the leaching rate of metal ions is improved, especially the leaching rate of high-valent metal ions (such as trivalent metal ions or tetravalent metal ions), and the recovery efficiency is improved.

[0018] In any embodiment, the concentration of the acid solution in step (3) is 0.2 mol / L-2 mol / L, the solid-liquid ratio of the positive electrode plate to the acid solution is 10 g / L-100 g / L, and the mass ratio of the positive electrode plate to the reducing substance is 1-10, which can improve the leaching rate of high-valent metal ions and improve the recovery efficiency.

[0019] In any embodiment, the reaction temperature in step (3) is 25° C.-60° C., and the reaction time is 0.5 h-3 h, which can allow the positive electrode current collector, the positive electrode active material and the acid solution to react fully, thereby improving the recovery efficiency.

[0020] In any embodiment, the metal salt concentration of the mixed salt solution in step (4) is 0.5 mol / L-2 mol / L, the concentration of the sodium hydroxide is 2 mol / L-10 mol / L, and the mass fraction of the ammonia water is 5%-25%, which can make the metal salt fully contact with the alkali, increase the rate of the coprecipitation reaction, and thus improve the recovery efficiency.

[0021] In any embodiment, the temperature of the coprecipitation reaction in step (4) is 50°C-70°C, and the reaction time is 30h-200h, which can increase the coprecipitation reaction rate and thus improve the recovery efficiency.

[0022] In any embodiment, the nickel salt in step (4) includes one or more of nickel sulfate, nickel chloride, nickel nitrate, nickel acetate, and nickel oxalate; the cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt oxalate; and the manganese salt includes one or more of manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, and manganese oxalate, so that the metal salts can fully undergo a coprecipitation reaction in the alkaline solution, thereby improving the recovery efficiency.

[0023] In any embodiment, the temperature of the calcination process in step (6) is 700° C.-850° C., and the calcination time is 8 h-16 h, which can enable the NCMA precursor to fully react with lithium hydroxide in the presence of oxygen, thereby improving the recovery efficiency.

[0024] The second aspect of the present application also provides a positive electrode active material, which is prepared by any preparation method described in any one of the first aspects of the present application.

[0025] In any embodiment, the particle size D50 of the positive electrode active material is 5 μm - 20 μm. In the X-ray diffraction pattern of the positive electrode active material, the peak intensity I(003) of the (003) diffraction peak and the peak intensity I(104) of the (104) diffraction peak satisfy: 1.2 < I(003) / I(104). Applying the positive electrode active material prepared in this application to a secondary battery is beneficial to improving the cycling performance of the secondary battery.

[0026] The third aspect of this application provides a positive electrode plate, including the positive electrode active material of the second aspect of this application.

[0027] The fourth aspect of this application provides a secondary battery, including the positive electrode plate of the third aspect of this application.

[0028] The fifth aspect of this application provides an electrical device, including the secondary battery of the fourth aspect of this application.

[0029] Advantages of this application:

[0030] A preparation method of a positive electrode active material, a positive electrode active material, a positive electrode plate, a secondary battery, and an electrical device provided in this application. The preparation method of the positive electrode active material includes the following steps: After roasting the positive electrode plate, the aluminum foil and the positive electrode active material are dissolved together in acid, nickel salt, cobalt salt, and manganese salt are added to undergo a coprecipitation reaction in an alkaline solution, and the nickel cobalt manganese aluminum lithium precursor is obtained by filtration. The filtrate is recrystallized and dried to obtain lithium hydroxide. The nickel cobalt manganese aluminum lithium precursor and lithium hydroxide are mixed and roasted to finally obtain the nickel manganese cobalt aluminum lithium positive electrode active material. By omitting the step of separating the active substance from the aluminum foil, the recycling method can be simplified, and soaking the positive electrode plate in an acid solution and a reducing substance can further improve the recycling efficiency. Brief Description of the Drawings

[0031] Figure 1 It is a preparation flow chart of this application;

[0032] Figure 2 It is a scanning electron microscope image of the NCMA precursor prepared in Example 1 of this application;

[0033] Figure 3 It is a scanning electron microscope image of the NCMA positive electrode active material prepared in Example 1 of this application;

[0034] Figure 4 It is a scanning electron microscope image of the NCMA positive electrode active material prepared in Comparative Example 1 of this application;

[0035] Figure 5 It is a scanning electron microscope image of the NCMA positive electrode active material prepared in Comparative Example 2 of this application;

[0036] Figure 6 This is the X-ray diffraction spectrum of the NCMA positive electrode active material prepared in Example 1 of the present application;

[0037] Figure 7 This is an X-ray diffraction spectrum of the NCMA positive electrode active material prepared in Comparative Example 2 of the present application;

[0038] Figure 8 A comparison chart of the cycle performance of the secondary batteries prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present application at 25°C;

[0039] Fig. 9 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0040] Fig.10 yes Fig. 9 An exploded view of a secondary battery according to an embodiment of the present application is shown;

[0041] Fig.11 is a schematic diagram of a battery module according to an embodiment of the present application;

[0042] Fig.12 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0043] Fig.13 yes Fig.12 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0044] Fig.14 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0045] Description of reference numerals:

[0046] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0047] Below, the preparation method of the positive electrode active material, the positive electrode active material, the secondary battery and the electric device of the present application, as well as the battery module and the battery pack containing the secondary battery of the present application are described in detail with appropriate reference to the drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0048] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0050] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0051] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0052] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0053] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0054] During the research process, the applicant found that the recovery of nickel-cobalt-manganese-oxide lithium from waste secondary batteries usually adopts mechanical crushing and separation, but the separation of active substances is incomplete under this process, and foil debris is mixed into the active substances, which leads to the subsequent increase of impurity removal steps. In order to simplify the recycling method of nickel-cobalt-manganese-oxide lithium batteries, improve the recycling efficiency, and reduce the degree of mixing of nickel and lithium in positive electrode active materials, the application provides a preparation method of positive electrode active materials, positive electrode active materials, positive electrode plates, secondary batteries and power devices.

[0055] In one embodiment of the present application, the present application proposes a method for preparing a positive electrode active material, referring to Figure 1 , including the following steps:

[0056] (1) discharging the waste nickel-cobalt-manganese-oxide lithium secondary battery in a saturated sodium chloride aqueous solution for 1 to 3 days, drying, and disassembling to obtain a positive electrode sheet;

[0057] (2) calcining the positive electrode sheet obtained in step (1) under a flowing air atmosphere to remove the conductive carbon and the binder;

[0058] (3) placing the positive electrode sheet obtained in step (2) into a soaking tank, adding an acid solution and a reducing substance into the soaking tank to react until the positive electrode current collector is completely dissolved, and filtering after the reaction to obtain a mixed solution containing nickel, manganese, cobalt, aluminum, and lithium elements;

[0059] (4) adding nickel salt, cobalt salt and manganese salt to the mixed solution, adjusting the molar ratio of nickel, cobalt, manganese and aluminum elements to obtain a mixed salt solution, further coprecipitating in sodium hydroxide and ammonia water, filtering to obtain a nickel cobalt manganese aluminum oxide lithium precursor, wherein the nickel cobalt manganese aluminum oxide lithium precursor satisfies (Ni t Co u Mn v Al w )(OH)2, where 0.5≤t<1, 0≤u≤0.5, 0≤v≤0.5, 0≤w≤0.3, and t+u+v+w=1;

[0060] (5) evaporating the solvent from the filtrate obtained in step (4) at 50° C.-80° C., recrystallizing, and drying to obtain lithium hydroxide powder;

[0061] (6) The nickel cobalt manganese aluminum oxide lithium precursor and lithium hydroxide powder are uniformly mixed in a molar ratio of 1:1.03-1:1.2, calcined in an oxygen atmosphere, crushed, sieved, and demagnetized to obtain the nickel cobalt manganese aluminum oxide lithium positive electrode active material.

[0062] Although the mechanism is not clear, the applicant unexpectedly discovered that: after the positive electrode is calcined, the positive electrode is placed in an immersion tank for acid dissolution, and a combination of an inorganic acid and a reducing agent is used to reduce the transition metal to a divalent state, thereby increasing the leaching rate of nickel, cobalt, manganese, and aluminum metals, eliminating the step of separating the active substance and the aluminum foil, simplifying the recovery method, and fully recovering the aluminum element in the aluminum foil, thereby improving the recovery efficiency. At the same time, the positive active material nickel-lithium mixed degree obtained by calcining the nickel-cobalt-manganese-aluminate lithium precursor obtained by coprecipitation and the lithium hydroxide powder is low, which is beneficial to improving the cycle performance of the secondary battery. In the present application, the immersion tank in the aforementioned step (3) and the device used for the coprecipitation reaction in the step (4) are not particularly limited, and the immersion tank and coprecipitation reaction device known in the art can be used.

[0063] In some embodiments, the positive electrode active material of the spent nickel cobalt manganese oxide lithium secondary battery conforms to the general formula Li(Ni x Co y Mn z )O2, wherein 0.5≤x<1, 0≤y≤0.5, 0≤z≤0.5, and x+y+z=1, by selecting waste secondary batteries that meet the above general formula, and the positive electrode collector in the positive electrode sheet of the waste secondary batteries is usually aluminum foil, nickel, cobalt, manganese, aluminum, and lithium elements can be provided, reducing the amount of subsequent metal salt added and improving the recycling efficiency.

[0064] In some embodiments, the drying temperature in step (1) is 50° C.-80° C., and the drying time is 8 h-12 h, which can prevent the sodium chloride solution from mixing into the reaction system, reduce the loss of high-valent metals, and improve the recovery efficiency.

[0065] In some embodiments, the temperature of the calcination in the flowing air atmosphere in step (2) is 400°C-600°C, and the calcination time is 3h-8h. By calcining the positive electrode sheet under the above conditions, impurities such as conductive carbon and binder can be fully carbonized, and the carbonized impurities are further removed by the flowing air. Compared with the method of directly using calcination and mechanical crushing and separation in the prior art, the loss of aluminum foil can be reduced and the recovery efficiency can be improved. Among them, impurities may include but are not limited to the residues of electrolyte and lithium salt after calcination.

[0066] In some embodiments, the acid solution in step (3) includes one or more of sulfuric acid, hydrochloric acid, nitric acid, citric acid, acetic acid, maleic acid, oxalic acid, lactic acid, aspartic acid, and ascorbic acid, and the reducing substance includes one or more of sulfite, bisulfite, and thiosulfate. By using the above acid solution and the reducing substance in combination, the positive electrode current collector can be completely dissolved, and the transition metal can be reduced to divalent, thereby increasing the solubility of the metal salt in the acid solution and improving the recovery efficiency. The sulfite in this application may include but is not limited to one or more of sodium sulfite and potassium sulfite, the bisulfite may include but is not limited to one or more of sodium bisulfite and potassium bisulfite, and the thiosulfate may include but is not limited to one or more of sodium thiosulfate and potassium thiosulfate.

[0067] In some embodiments, the concentration of the acid solution in step (3) is 0.2 mol / L-2 mol / L, the solid-liquid ratio of the positive electrode sheet to the acid solution is 10 g / L-100 g / L, and the mass ratio of the positive electrode sheet to the reducing substance is 1-10. By synergistically controlling the contents of the acid solution, the reducing substance and the positive electrode sheet to meet the above conditions, the leaching rate of high-valent metal ions in the positive electrode sheet can be further improved, thereby improving the recovery efficiency.

[0068] In some embodiments, the reaction temperature in step (3) is 25°C-60°C, and the reaction time is 0.5h-3h. By adjusting the reaction temperature and reaction time of the positive electrode plate, the acid solution and the reducing substance, the positive electrode current collector can be fully dissolved, the positive electrode active material and the acid solution can fully react, and the recovery efficiency can be improved.

[0069] In some embodiments, the metal salt concentration of the mixed salt solution in step (4) is 0.5 mol / L-2 mol / L, the concentration of sodium hydroxide is 2 mol / L-10 mol / L, and the mass fraction of ammonia water is 5%-25%. By selecting ammonia water with a mass fraction within the range of this application and controlling the concentrations of the metal salt and sodium hydroxide within the range of this application, the metal salt can be fully reacted in an alkaline environment, thereby increasing the rate of the coprecipitation reaction and thus improving the recovery efficiency.

[0070] In some embodiments, the temperature of the coprecipitation reaction in step (4) is 50°C-70°C, and the reaction time is 30h-200h. By controlling the temperature and time of the coprecipitation reaction, the coprecipitation reaction rate can be increased, thereby improving the recovery efficiency.

[0071] In some embodiments, in step (4), the nickel salt includes one or more of nickel sulfate, nickel chloride, nickel nitrate, nickel acetate, and nickel oxalate; the cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt oxalate; the manganese salt includes one or more of manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, and manganese oxalate. By selecting the above divalent metal salts, the solubility of the metal salts in the alkaline solution can be increased, the coprecipitation reaction rate can be increased, and thus the recovery efficiency can be improved.

[0072] In some embodiments, in step (6), the temperature of the calcination process is 700°C - 850°C, and the calcination time is 8h - 16h. By controlling the temperature and time of the calcination process within the above ranges, the NCMA precursor and lithium hydroxide can react fully under oxygen, and the recovery efficiency can be improved.

[0073] In one embodiment of the present application, a cathode active material is provided, which is prepared by any of the above embodiments. The cathode active material prepared by the preparation method of the present application has improved thermal stability and cycling stability due to the doping of aluminum element.

[0074] In one embodiment of the present application, the particle size D50 of the cathode active material is 5μm - 20μm. In the X-ray diffraction pattern of the cathode active material, the peak intensity I(003) of the (003) diffraction peak and the peak intensity I(104) of the (104) diffraction peak satisfy: 1.2 < I(003) / I(104). The cathode active material prepared by the preparation method provided in the first aspect of the present application has a low degree of nickel-lithium mixing. Further applying the cathode active material prepared by the present application to a secondary battery is beneficial to improving the cycling performance of the secondary battery.

[0075] In one embodiment of the present application, a cathode electrode sheet is provided, which includes a cathode current collector and a cathode film layer. Among them, the cathode film layer contains the cathode active material prepared by any of the above embodiments.

[0076] In addition, the secondary battery and the electrical device of the present application, as well as the battery module and the battery pack including the secondary battery of the present application, will be described below with appropriate reference to the drawings.

[0077] In one embodiment of the present application, a secondary battery is provided, which includes the cathode active material described in any of the above embodiments. The secondary battery provided by the present application includes a cathode active material prepared by recycling a waste lithium nickel cobalt manganese oxide secondary battery. The obtained secondary battery has good cycling performance and is basically consistent with the cycling performance of a secondary battery including the same newly prepared cathode active material. This shows that the preparation method of the cathode active material provided by the present application can effectively recycle metals such as nickel, cobalt, manganese, aluminum, and lithium in the waste lithium nickel cobalt manganese oxide secondary battery and has good practical value.

[0078] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0079] [Positive electrode]

[0080] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0081] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0082] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0083] In some embodiments, the positive electrode active material is a positive electrode active material prepared by the preparation method provided in the present application.

[0084] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0085] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0086] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0087] [Negative electrode]

[0088] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0089] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0090] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0092] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0093] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0094] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0095] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0096] [Electrolytes]

[0097] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The electrolyte used in the present application may be a liquid electrolyte.

[0098] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0099] In some embodiments, the electrolyte salt can be selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0100] In some embodiments, the solvent can be selected from one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0101] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0102] [Isolation film]

[0103] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0104] In some embodiments, the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0105] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0106] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0107] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Fig. 9 The secondary battery 5 is a square structure as an example.

[0109] In some embodiments, reference Fig.10 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0110] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0111] Fig.11 4 is an example of a battery module. Fig.11In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0112] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0113] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0114] Fig.12 and Fig.13 1 is a battery pack 1 as an example. Fig.12 and Fig.13 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0115] In addition, the present application also provides an electrical device, which includes one or more of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

[0116] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0117] Fig.14 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0118] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0119] Example

[0120] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0121] Example 1

[0122] <Preparation of positive electrode active material>

[0123] (1) Waste NCM811(Li(Ni 0.8 Co 0.1 Mn 0.1 The )O2) secondary battery was discharged in a sodium chloride solution for 1 day, baked at 80°C for 8h, and disassembled to obtain the positive electrode sheet.

[0124] (2) The positive electrode sheet obtained in the first step is calcined at 500° C. for 5 h in a flowing air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0125] (3) The positive electrode obtained in the second step is placed in a soaking tank, and sulfuric acid solution and solid sodium thiosulfate are added to the soaking tank, wherein the concentration of sulfuric acid is 0.5 mol / L, the solid-liquid ratio of the positive electrode to the sulfuric acid solution is 20 g / L, the mass ratio of the positive electrode to the sodium thiosulfate is 2, the reaction temperature is 45°C, the reaction time is 1 hour, and after the reaction is completed, a mixed solution containing nickel, cobalt, manganese, aluminum, and lithium elements is obtained by filtering.

[0126] (4) adding nickel sulfate, cobalt sulfate and manganese sulfate to the mixed solution to obtain a mixed salt solution, wherein the ratio of nickel, cobalt, manganese and aluminum elements in the obtained mixed salt solution is Ni:Co:Mn:Al=80:5:10:5, placing the mixed salt solution in a continuous reactor, causing a coprecipitation reaction in sodium hydroxide and ammonia water, and filtering to obtain an NCMA precursor (Ni( 0.8 Co 0.05 Mn 0.1 Al 0.05 )(OH)2), wherein the mixed salt concentration is 1.5 mol / L, the sodium hydroxide concentration is 8 mol / L, the ammonia mass fraction is 25%, the reaction temperature is 55°C, and the reaction time is 48h. The scanning electron microscope image of the NCMA precursor prepared in Example 1 is as follows Figure 2 shown.

[0127] (5) The solvent is evaporated from the filtrate at 70° C., wet lithium hydroxide is obtained by recrystallization, and then dried to obtain lithium hydroxide powder.

[0128] (6) The NCMA precursor and lithium hydroxide powder were mixed evenly in a molar ratio of 1:1.05, calcined at 750 °C for 10 h in an oxygen atmosphere, crushed, sieved, and demagnetized to obtain the NCMA positive electrode active material (Li(Ni 0.8 Co 0.05 Mn 0.1 Al 0.05 )O2). The scanning electron microscope image of the NCMA positive electrode active material prepared in Example 1 is as follows Figure 3 shown.

[0129] <Preparation of positive electrode sheet>

[0130] The NCMA positive electrode active material, conductive agent carbon black, and binder polyvinylidene chloride (PVDF) prepared above are mixed in a weight ratio of 67.34:30:28.86, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and stirred under the action of a vacuum mixer until the system becomes a uniform positive electrode slurry. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 90°C to obtain a positive electrode sheet with a single-sided coating of positive electrode active material and a positive electrode film thickness of 110μm. After that, the above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet with a double-sided coating of positive electrode active material. After coating, the positive electrode sheet is cold pressed and cut into a size of 74mm×867mm for standby use.

[0131] <Preparation of negative electrode sheet>

[0132] The negative electrode active material graphite, the conductive agent carbon black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose are mixed in a weight ratio of 96.2:0.8:0.8:1.2, and then deionized water is added as a solvent to prepare a negative electrode slurry with a solid content of 70wt%, and stirred under the action of a vacuum mixer until the system becomes a uniform negative electrode slurry. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 8μm, and dried at 90°C to obtain a negative electrode sheet with a single-sided coating of negative electrode active material and a negative electrode film thickness of 130μm. After that, the above steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of negative electrode active material. After the coating is completed, the negative electrode sheet is cold pressed and cut into a specification of 76mm×851mm for standby use.

[0133] <Preparation of Electrolyte>

[0134] In an argon atmosphere glove box with a water content of <10ppm and an O2 content of <0.1ppm, organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 3:7 to form a base solvent, and LiPF6 is added to dissolve and stirred to form an electrolyte, wherein the mass percentage of LiPF6 is 12.5%, and the remainder is the base solvent.

[0135] <Isolation film>

[0136] A polyethylene (PE) porous polymer film is used as the isolation membrane.

[0137] <Preparation of Secondary Battery>

[0138] The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound, the tail is glued, and placed in an aluminum shell. The edge of the aluminum shell is sealed, and then placed in a vacuum oven at 85°C for 12 hours to remove moisture from the dry battery cell. Finally, the prepared electrolyte is injected into the vacuum-dried battery. After vacuum packaging, standing, formation, forming and other processes, the preparation of the secondary battery is completed.

[0139] Example 2

[0140] The process was the same as in Example 1 except that the reaction temperature was 25°C in step (3) of <Preparation of Positive Electrode Active Material>.

[0141] Example 3

[0142] The process was the same as in Example 1 except that the reaction time in step (3) of <Preparation of Positive Electrode Active Material> was 0.5 h.

[0143] Example 4

[0144] The process is the same as that of Example 1 except that in step (3) of <Preparation of Positive Electrode Active Material> the mass ratio of the positive electrode sheet to sodium thiosulfate is 5.

[0145] Example 5

[0146] The same procedures as in Example 1 were performed except that acetic acid was used as the acid solution in step (3) of <Preparation of Positive Electrode Active Material>.

[0147] Example 6

[0148] The process was the same as in Example 1 except that sodium sulfite was used as the reducing substance in step (3) of <Preparation of Positive Electrode Active Material>.

[0149] Example 7

[0150] The process was the same as in Example 1 except that the calcination temperature was 800° C. in step (6) of <Preparation of Positive Electrode Active Material>.

[0151] Example 8

[0152] The process was the same as in Example 1 except that the calcination time in step (6) of <Preparation of positive electrode active material> was 12 h.

[0153] Example 9

[0154] The method is the same as Example 1 except that nickel sulfate, cobalt sulfate and manganese sulfate are added in step (4) of <Preparation of Positive Electrode Active Material> to obtain a mixed salt solution, and the molar ratio of nickel, cobalt, manganese and aluminum elements is Ni:Co:Mn:Al=87:5:5:3.

[0155] Comparative Example 1

[0156] Except that the positive electrode active material is prepared according to the following preparation method, the rest is the same as Example 1:

[0157] (1) Nickel sulfate, cobalt sulfate, manganese sulfate, and aluminum sulfate were mixed in a molar ratio of Ni:Co:Mn:Al=80:5:10:5, placed in a continuous reactor, and coprecipitated in sodium hydroxide and ammonia water to obtain an NCMA precursor (Ni( 0.8 Co 0.05 Mn 0.1 Al 0.05 )(OH)2), wherein the mixed salt concentration is 1.5 mol / L, the sodium hydroxide concentration is 8 mol / L, the ammonia mass fraction is 25%, the reaction temperature is 55°C, and the reaction time is 48h.

[0158] (2) The solvent is evaporated from the filtrate at 70° C., wet lithium hydroxide is obtained by recrystallization, and then dried to obtain lithium hydroxide powder.

[0159] (3) NCMA precursor and lithium hydroxide were mixed evenly in a molar ratio of 1:1.05, calcined at 750 °C for 10 h in an oxygen atmosphere, crushed, sieved, and demagnetized to obtain NCMA positive electrode active material (Li(Ni 0.8 Co 0.05 Mn 0.1 Al 0.05 )O2).

[0160] The scanning electron microscope image of the NCMA positive electrode active material prepared in Comparative Example 1 is as follows: Figure 4 shown.

[0161] Comparative Example 2

[0162] Except that the positive electrode active material is prepared according to the following preparation method, the rest is the same as Example 1:

[0163] (1) Waste NCM811(Li(Ni 0.8 Co 0.1 Mn 0.1 The )O2) secondary battery was discharged in a sodium chloride solution for 1 day, baked at 80°C for 8h, disassembled to obtain a positive electrode sheet, and the positive electrode sheet was immersed in sodium hydroxide for 7h to obtain a black powder. The black powder was dried and sieved to obtain a positive electrode powder.

[0164] (2) The positive electrode powder obtained in the first step is calcined at 500° C. for 5 h in a flowing air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0165] (3) The positive electrode powder obtained in the second step is placed in a soaking tank, and an acetic acid solution is added to the soaking tank, wherein the concentration of the acetic acid is 1 mol / L, the solid-liquid ratio of the positive electrode powder to the acetic acid solution is 20 g / L, the reaction temperature is 45°C, the reaction time is 1 h, and after the reaction is completed, a mixed solution containing nickel, cobalt, manganese, and lithium elements is obtained by filtering.

[0166] (4) Add nickel acetate, cobalt acetate, manganese acetate and aluminum to the mixed solution prepared in the third step to adjust the molar ratio of nickel, cobalt, manganese and aluminum to Ni:Co:Mn:Al=80:5:10:5, and add lithium acetate to adjust the molar ratio of the above metal elements to lithium element to 1:1.05.

[0167] (5) The mixture obtained in the fourth step was kept at 120°C for 20 h, evaporated to dryness to obtain a precursor material, calcined at 750°C for 10 h in an oxygen atmosphere, crushed, sieved, and demagnetized to obtain a regenerated NCMA positive electrode active material (Li(Ni 0.8 Co 0.05 Mn 0.1 Al 0.05 )O2). The scanning electron microscope image of the NCMA positive electrode active material prepared in Comparative Example 2 is as follows Figure 5 shown.

[0168] Comparative Example 3

[0169] The process was the same as in Example 1 except that sodium thiosulfate was not added to the immersion tank in step (3) of <Preparation of Positive Electrode Active Material>.

[0170] Performance parameter test:

[0171] Average particle size test of positive electrode active material (D50):

[0172] Add 0.02g of the material to be tested into a 50ml clean beaker, then add 20ml of deionized water, and then add a few drops of 1% surfactant, disperse the positive electrode active material powder into the aqueous solution at room temperature, ultrasonicate it in a 120W ultrasonic cleaner for 5 minutes, and use MasterSizer 2000 to test the particle size distribution from the small particle size side. D50 is the cumulative 50% diameter of the volume reference distribution obtained by the laser scattering particle size analyzer.

[0173] Particle morphology test:

[0174] The positive electrode active material is made into a pole piece sample and tested using a ZEISS sigma 300 scanning electron microscope with a working distance of 5mm to 30mm, an objective lens aperture of 100μm to 200μm, and an acceleration voltage of 2kV to 20kV. The focused electron beam of the instrument is used to excite the sample surface to generate secondary electrons, backscattered electrons, characteristic X-rays and other secondary information, which is collected and detected for microscopic morphology analysis of the sample surface.

[0175] Particle crystallinity test:

[0176] Place the positive electrode active material powder in the circular groove of the washed glass slide, so that the surface of the sample to be tested is spread flat and there is no sample spilled around. Use XD-3 X-ray diffraction analyzer (XRD) (produced by Beijing Puxi General Instrument Co., Ltd.) to test, use the excitation source (CuKα (λ=1.5406)) to excite and scan the sample, and collect the XRD test data of the sample. Among them, the tube voltage is 40kV, the tube current is 40mA, the scanning speed is 1° / min, the step width is 0.02°, and the scanning range is 10°-80°.

[0177] Metal leaching rate test:

[0178] Dismantle the waste secondary battery to obtain the positive electrode sheet, take 2g of the dismantled positive electrode sheet, add aqua regia (the volume ratio of concentrated hydrochloric acid and concentrated nitric acid is 3:1), heat and digest, filter to obtain a filtrate, and use an inductively coupled plasma spectrometer (Agilent ICP-S5800) to determine the mass fraction of transition metals nickel, cobalt, manganese and aluminum to be A. Take the dismantled positive electrode sheet with a mass of M0, add an acid solution and a reducing substance to dissolve, and then filter (wherein, the amount of acid solution and reducing substance added is the content in each embodiment and comparative example), and obtain a filter residue with a mass of M1. Take a small amount of the filter residue and digest it with aqua regia, and measure the mass fraction of transition metals nickel, cobalt, manganese and aluminum by an inductively coupled plasma spectrometer to be B, then the metal leaching rate μ is:

[0179] μ=[1-(M1×B / M0×A)]×100%.

[0180] Secondary battery capacity retention test:

[0181] At 25°C, charge the secondary battery at a constant current of 0.3C to 4.3V, then charge at a constant voltage of 4.3V to a current of 0.05C, let stand for 5 minutes, and then discharge at 0.3C to 2.8V. The test capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery, and record the discharge capacity C0 of the battery after the 400th cycle. n , the capacity retention rate Pn after cycling is:

[0182] Pn=C n / C0×100%.

[0183] The relevant preparation parameters of the above-mentioned Examples 1 to 9 and Comparative Examples 1 to 3 are shown in Table 1 below;

[0184] The performance parameters of the above-mentioned Examples 1 to 9 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0185] Table 1

[0186]

[0187]

[0188] Note: In Table 1, “ / ” indicates that there is no corresponding preparation parameter.

[0189] Table 2

[0190]

[0191] Note: In Table 2, “ / ” indicates that there is no corresponding performance parameter.

[0192] It can be seen from Examples 1 to 9 and Comparative Example 3 that by immersing the positive electrode plate in an immersion tank containing both an acid solution and a reducing substance, the metal leaching rate is higher and the recovery efficiency is better. The positive electrode active material prepared by the preparation method provided in this application has a lower production cost.

[0193] The type of acid solution, the type of reducing substance, the mass ratio of the positive electrode sheet to the reducing substance, the reaction temperature in the immersion tank, the reaction time in the immersion tank, the calcination temperature in step (6), and the calcination time in step (6) usually also affect the performance of the prepared positive electrode active material, and thus affect the performance of the secondary battery. By regulating the above parameters within the scope of this application, the obtained positive electrode active material is applied to a secondary battery, and the secondary battery has good cycle performance.

[0194] In addition, the scanning electron microscope image of the NCMA positive electrode active material prepared in Example 1 (as shown in FIG. Figure 3 As shown), the scanning electron microscope image of the NCMA positive electrode active material prepared in Comparative Example 1 (as shown Figure 4) and the scanning electron microscope image of the NCMA positive electrode active material prepared in Comparative Example 2 (as shown Figure 5 As shown in the figure, it can be seen from the comparison that the positive electrode active material prepared in the present application has no obvious defects on the surface; the NCMA positive electrode active material prepared in Example 1, the NCMA positive electrode active material prepared in Comparative Example 1 and the NCMA positive electrode active material prepared in Comparative Example 2 are applied to secondary batteries, and their cycle performance is tested to obtain a cycle performance comparison diagram (as shown in the figure Figure 8 shown), from Figure 8 As can be seen from Table 2, the cycle performance of the secondary battery prepared in Example 1 of the present application is basically consistent with the cycle performance of the secondary battery prepared in Comparative Example 1, which shows that the preparation method of the positive electrode active material provided by the present application can effectively recycle metals such as nickel, cobalt, manganese, aluminum, and lithium in waste nickel-cobalt-manganese lithium secondary batteries, and has good practical value. Figure 8 As can be seen from Table 2, the cycle performance of the secondary battery prepared in Example 1 is better than that of the secondary battery prepared in Comparative Example 2. The inventors speculate that this is because the I(003) / I(104) value of the positive electrode active material prepared in Example 1 is higher than that of the positive electrode active material prepared in Comparative Example 2 (e.g. Figure 6 and Figure 7 As shown), that is, the degree of nickel-lithium mixing is lower, so the secondary battery prepared in the embodiment of the present application has better cycle performance. It can be seen from Example 1 to Example 9 in Table 2 that the positive electrode active material prepared by the preparation method of the present application is applied to a secondary battery, and its I(003) / I(104) value is within the scope of the present application, the degree of nickel-lithium mixing is low, and the obtained secondary battery has good cycle performance.

[0195] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a positive electrode active material, characterized in that: The following steps are involved: (1) discharging the waste nickel-cobalt-manganese-oxide lithium secondary battery in a saturated sodium chloride aqueous solution for 1 to 3 days, drying, and disassembling to obtain a positive electrode sheet; (2) calcining the positive electrode sheet obtained in step (1) in a flowing air atmosphere to remove the conductive carbon and the binder; (3) placing the positive electrode sheet obtained in step (2) into a soaking tank, adding an acid solution and a reducing substance into the soaking tank to react until the positive electrode current collector is completely dissolved, and filtering after the reaction to obtain a mixed solution containing nickel, manganese, cobalt, aluminum, and lithium elements; (4) adding nickel salt, cobalt salt and manganese salt to the mixed solution, adjusting the molar ratio of nickel, cobalt, manganese and aluminum elements to obtain a mixed salt solution, and causing a coprecipitation reaction in sodium hydroxide and ammonia water, wherein the coprecipitation reaction temperature is 50° C.-70° C. and the reaction time is 30 h-200 h; filtering to obtain a nickel cobalt manganese aluminum oxide lithium precursor, wherein the nickel cobalt manganese aluminum oxide lithium precursor satisfies (Ni t Co u Mn v Al w )(OH)2, where 0.5≤t<1, 0<u≤0.5, 0<v≤0.5, 0<w≤0.3, and t+u+v+w=1; (5) evaporating the solvent from the filtrate obtained in step (4) at 50° C.-80° C., recrystallizing, and drying to obtain lithium hydroxide powder; (6) The nickel cobalt manganese aluminum oxide precursor and the lithium hydroxide powder are uniformly mixed in a molar ratio of 1:1.03-1:1.2, calcined in an oxygen atmosphere, crushed, sieved, and demagnetized to obtain a nickel cobalt manganese aluminum oxide positive electrode active material.

2. The preparation method according to claim 1, characterized in that: The positive electrode active material of the waste nickel cobalt manganese oxide lithium secondary battery conforms to the general formula Li(Ni x Co y Mn z )O2, where 0.5≤x<1, 0<y≤0.5, 0<z≤0.5, and x+y+z=1.

3. The preparation method according to claim 1, characterized in that: The calcination temperature in the flowing air atmosphere in step (2) is 400° C.-600° C., and the calcination time is 3 h-8 h.

4. The preparation method according to claim 1, characterized in that: The acid solution in step (3) includes one or more of sulfuric acid, hydrochloric acid, nitric acid, citric acid, acetic acid, maleic acid, oxalic acid, lactic acid, aspartic acid, and ascorbic acid, and the reducing substance includes one or more of sulfite, bisulfite, and thiosulfate.

5. The preparation method according to claim 1, characterized in that: The concentration of the acid solution in step (3) is 0.2 mol / L-2 mol / L, the solid-liquid ratio of the positive electrode sheet to the acid solution is 10 g / L-100 g / L, and the mass ratio of the positive electrode sheet to the reducing substance is 1-10.

6. The preparation method according to claim 1, characterized in that: The reaction temperature in step (3) is 25°C-60°C, and the reaction time is 0.5h-3h.

7. The preparation method according to claim 1, characterized in that: The metal salt concentration of the mixed salt solution in step (4) is 0.5 mol / L-2 mol / L, the concentration of the sodium hydroxide is 2 mol / L-10 mol / L, and the mass fraction of the ammonia water is 5%-25%.

8. The preparation method according to claim 1, characterized in that: The nickel salt in step (4) includes one or more of nickel sulfate, nickel chloride, nickel nitrate, nickel acetate, and nickel oxalate; the cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt oxalate; and the manganese salt includes one or more of manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, and manganese oxalate.

9. The preparation method according to claim 1, characterized in that: The temperature of the calcination process in step (6) is 700° C.-850° C., and the calcination time is 8 h-16 h.

10. A positive electrode active material, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 9.

11. The positive electrode active material according to claim 10, characterized in that The particle size D50 of the positive electrode active material is 5 μm-20 μm. In the X-ray diffraction spectrum of the positive electrode active material, the peak intensity I(003) of the diffraction peak (003) and the peak intensity I(104) of the diffraction peak (104) satisfy the following relationship: 1.2 <I(003) / I(104)。 12. A positive electrode sheet, characterized in that: The invention comprises the positive electrode active material according to any one of claims 10 to 11.

13. A secondary battery, characterized in that: Including the positive electrode sheet as described in claim 12.

14. An electrical device, characterized in that: Includes the secondary battery as claimed in claim 13.

Images