Method for recovering negative electrode material, negative electrode material, secondary battery, battery pack, and electric device

Abstract

The invention provides a recycling method of a negative electrode material, the negative electrode material, a secondary battery, a battery pack and an electric device. The recycling method of the negative electrode material comprises the following steps: pretreating a negative electrode plate to be recycled, so that a current collector is separated from an active material covering the current collector, and a graphite waste material is obtained; the graphite waste is subjected to oxidation treatment and acid pickling, and impurity-removed graphite is obtained; wherein oxidation treatment comprises the steps that oxidizing gas is introduced into the reaction furnace, the graphite slag is oxidized in a high-temperature furnace at the temperature of 300-800 DEG C, and the introduction amount of the oxidizing gas per hour is 1-9 times of the volume of the reaction furnace; the impurity-removed graphite is subjected to coating carbonization, and the coating carbonization comprises the steps that the impurity-removed graphite is mixed with a carbon source, carbonization is carried out in an inert atmosphere at the temperature of 1100-1300 DEG C, and the regenerated negative electrode material is obtained. According to the method, impurities can be removed to a greater extent, graphite with a greater yield is obtained, and the negative electrode material obtained through coating and carbonization is moderate in specific surface area, large in gram volume and high in button electricity first efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of battery recycling, and in particular to a method for recycling negative electrode materials, negative electrode materials, secondary batteries, battery packs and electrical devices. Background Art

[0002] With the rapid development of the new energy vehicle industry, a large number of batteries are scrapped. Since waste batteries contain a variety of strategic resources such as graphite, if they are not recycled, a large amount of resources will be wasted. In addition, scrapped batteries are highly polluting. The surface material of the battery pole and the current collector are bonded together by a binder (PVDF), which has strong viscosity and complex impurity components, making it difficult to separate, recycle and reuse.

[0003] To this end, the present invention is proposed. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a method for recycling negative electrode materials and the obtained negative electrode materials, and to use the secondary batteries, battery packs and electrical devices composed of the negative electrode materials. The recycling method can remove impurities to a greater extent and obtain a higher yield of graphite, and the negative electrode materials obtained by coating and carbonization have moderate specific surface area, large gram capacity and high initial efficiency of charge withdrawal.

[0005] In order to achieve the above objectives, this application provides the following technical solutions.

[0006] The first aspect of the present application provides a method for recycling a negative electrode material, wherein the negative electrode material is a graphite system, and the recycling method comprises the following steps:

[0007] Pre-treating the negative electrode sheet to be recycled so as to separate the current collector from the active material covering the current collector to obtain graphite waste;

[0008] The graphite waste is subjected to oxidation treatment and pickling to obtain impurity-removed graphite; wherein the oxidation treatment comprises: introducing an oxidizing gas into a reaction furnace to oxidize the graphite slag in a high-temperature furnace at 300 to 800° C., and the amount of the oxidizing gas introduced per hour is 1 to 9 times the volume of the reaction furnace;

[0009] The de-impurified graphite is coated and carbonized, and the coating and carbonization comprises: mixing the de-impurified graphite with a carbon source, and carbonizing the mixture under an inert atmosphere at 1100-1300° C. to obtain a regenerated negative electrode material.

[0010] Therefore, the present application separates the graphite on the negative electrode plate through pretreatment, then oxidizes and pickles the graphite to remove organic impurities, metal impurities, etc., and finally converts the graphite into a regenerated negative electrode material with moderate specific surface area, large gram capacity and high initial efficiency through coating and carbonization. This not only solves the problem of recycling difficulty, but also improves the performance of the recycled materials.

[0011] In any embodiment, the oxidation treatment time is 1 to 4 hours. During this time period, organic impurities such as binders, dispersants, and some conductive agents in the graphite waste can be effectively removed.

[0012] In any embodiment, the oxidation in a high temperature furnace at 300-800°C includes: raising the temperature to 300-450°C at a heating rate of 3-5°C / min, keeping the temperature for 0.5-1.5h, and continuing to heat the temperature to 450-800°C at a heating rate of 5-10°C / min, and keeping the temperature for 0.5-2.5h.

[0013] By controlling the temperature rise process during oxidation, different types of impurities can be oxidized and removed in an orderly manner, so that organic impurities can be oxidized as completely as possible, and part of the conductive agent can be oxidized.

[0014] In any embodiment, during the oxidation treatment, the flow rate of the oxidizing gas is 3 to 8 times the volume of the reactor / h. Further optimizing the flow rate of the oxidizing gas can control the specific surface area of ​​the recovered graphite, so as to prevent the specific surface area from being too small to cause difficulty in removing lithium, and also take into account a higher graphite yield.

[0015] In any embodiment, the mass ratio of the de-impurified graphite to the carbon source is 100:(1.5-10).

[0016] When the mass ratio is within this range, the amorphous carbon formed in the subsequent carbonization process can effectively repair the defects on the surface of the impurity-free graphite and reduce the consumption of active lithium in the first charge and discharge process.

[0017] In any embodiment, the carbon source includes asphalt. Asphalt as a carbon source can not only effectively repair the defects of the graphite surface, but also limit the specific surface area and prevent it from being too large.

[0018] In any embodiment, the softening point of the pitch is 90 to 280° C., preferably 120 to 250° C. The pitch with a softening point of 90 to 280° C. is more effective for surface repair of the recycled graphite surface.

[0019] In any embodiment, the carbonization in an inert atmosphere at 1100-1300° C. includes: first heating to 250-300° C. at 3-5° C. / min, keeping warm for 1-2 hours, then heating to 1100-1300° C. at 3-5° C. / min, and keeping warm for 2.5-3.5 hours.

[0020] In the staged heating process, the temperature is first raised to 250℃-300℃. Since the heating temperature is higher than the softening point of the asphalt material, the asphalt material is melted and softened by heat. Keeping it warm for 1h-3h can make it flow evenly and coat the surface of the recycled graphite. Then the temperature is raised to 1100-1300℃ and kept warm for 1.5-3.5h. At this time, the asphalt material undergoes a carbonization reaction, which can effectively repair the defects on the surface of the recycled graphite.

[0021] In any embodiment, the pretreatment is performed in at least one of the following ways:

[0022] Method 1: crush the negative electrode sheets to be recycled, and then separate the graphite waste by air separation;

[0023] Method 2: crush the negative electrode sheets to be recycled, then wash and filter them to collect the graphite waste.

[0024] The above two methods are used to separate the current collector and the active material of the graphite system more quickly and efficiently, and reduce the amount of solvent used.

[0025] The second aspect of the present application also provides a negative electrode material, which includes the regenerated negative electrode material obtained by the recovery method of the first aspect.

[0026] Therefore, the regenerated negative electrode material has a higher first charge efficiency and gram capacity when used in secondary batteries such as lithium batteries.

[0027] A third aspect of the present application provides a secondary battery, which includes a positive electrode sheet and a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet includes the negative electrode material described in the second aspect.

[0028] A fourth aspect of the present application provides a battery pack, comprising the secondary battery of the third aspect of the present application.

[0029] The fifth aspect of the present application provides an electrical device, comprising at least one selected from the secondary battery of the third aspect of the present application and the battery pack of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0031] Figure 2 yes Figure 5 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0032] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0033] Figure 4It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0034] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0035] Figure 6 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.

[0036] Description of reference numerals:

[0037] 1-battery pack; 2-upper box; 3-lower box; 4-battery module; 5-secondary battery; 51-housing; 52-electrode assembly; 53-cover plate. DETAILED DESCRIPTION

[0038] Below, the negative electrode material recovery method, negative electrode material, secondary battery, battery module, battery pack and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying 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.

[0039] "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 form a scope with any upper limit combination. 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.

[0040] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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).

[0045] In order to separate and recycle negative electrode materials such as graphite from scrapped batteries, oxidation methods can be used to remove organic impurities such as thickeners, binders, and dispersants in graphite. These organic impurities will be oxidized to generate gases and thus be removed. However, improper oxidation conditions will lead to many defects on the graphite surface, poor pore distribution uniformity, or excessively large and dense pores, which will lead to low initial efficiency of the material.

[0046] Based on this, the present application proposes a method for recycling negative electrode materials, which is mainly aimed at negative electrode materials of a graphite system.

[0047] Specifically, the method for recycling negative electrode materials comprises the following steps:

[0048] Pre-treating the negative electrode sheet to be recycled so as to separate the current collector from the active material covering the current collector to obtain graphite waste;

[0049] The graphite waste is subjected to oxidation treatment and pickling to obtain impurity-removed graphite; wherein the oxidation treatment comprises: introducing an oxidizing gas into a reaction furnace to oxidize the graphite slag in a high-temperature furnace at 300 to 800° C., and the amount of the oxidizing gas introduced per hour is 1 to 9 times the volume of the reaction furnace;

[0050] The de-impurified graphite is coated and carbonized, and the coating and carbonization comprises: mixing the de-impurified graphite with a carbon source, and carbonizing the mixture under an inert atmosphere at 1100-1300° C. to obtain a regenerated negative electrode material.

[0051] Among them, the negative electrode sheets to be recycled mainly refer to the sheets with graphite as the active material, which can be the negative electrodes in nickel batteries, lithium batteries and other batteries.

[0052] The graphite waste obtained by pretreatment refers to the active material separated from the current collector, which usually includes graphite, conductive agent, thickener, adhesive and other components, as well as metal and other impurities embedded in the negative electrode during use. Some negative electrodes may also include auxiliary materials such as dispersants. The main purpose of pretreatment is to physically separate the current collector and the covering layer, and the means include but are not limited to at least one or more combinations of solvent immersion, crushing, air separation, water washing, filtration and other means.

[0053] Oxidation treatment and pickling are two steps, which can be oxidized first and then pickled, or pickled first and then oxidized. The purpose of oxidation treatment is mainly to remove organic impurities in graphite waste, and the main purpose of pickling is to remove metal impurities. However, the types of impurities removed by these two steps are not limited to the above types. For example, pickling may also remove some organic impurities that are easily acid-decomposed.

[0054] Pickling refers to soaking the graphite waste in an acid solution for reaction, which may be appropriately heated and / or stirred. The acid solution includes but is not limited to sulfuric acid, hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid, etc.

[0055] The temperature in the oxidation treatment needs to be controlled within 300-800°C. If the temperature is too low, the organic impurities cannot be effectively oxidized into gas and removed. If it is too high, the graphite is oxidized, resulting in too low a yield, which greatly reduces the economic effect of the recovery. "Controlled at 300-800°C" includes but is not limited to controlling at 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, etc., or controlling within a range with a small fluctuation of the average value of the above values, such as ±10°C, ±20°C, ±30°C, etc., or using a step-by-step heating method, such as first heating to a relatively low temperature level, keeping the temperature for a period of time, and then continuing to heat to a higher temperature and keeping the temperature. The oxidation treatment needs to be carried out in an oxidizing atmosphere, and the hourly flow rate is controlled at 1 to 9 times the volume of the reactor. If the flow rate is too low, oxygen cannot effectively contact impurities, thereby reducing the impurity removal rate; if the flow rate is too high, on the one hand, graphite is lost, and on the other hand, it will cause many surface defects in the graphite microcrystalline structure, such as uneven pore distribution or excessive specific surface area, which will lead to poor electrical properties such as the first power reduction effect. "Controlled within 1 to 9 times" includes but is not limited to control within 1 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, etc., or control within a range with a small fluctuation of the average value of the above values, such as ±0.5 times, ±0.3 times, ±0.1 times, etc. The oxidizing gas can be air, oxygen, water vapor, etc.

[0056] The carbon source during coating carbonization can be at least one of polyethylene glycol, starch, glucose, sucrose, phenolic resin, asphalt, etc.

[0057] Therefore, the present application transforms graphite into a regenerated negative electrode material with moderate specific surface area, large gram capacity and high initial efficiency of charge withdrawal through the process of pretreatment, oxidation treatment, pickling and coating carbonization, which not only solves the problem of difficult negative electrode recycling, but also improves the performance of the recycled material.

[0058] In some embodiments, the oxidation treatment time is 1 to 4 hours, for example, 1 hour, 1 hour, 2 hours, 3 hours, and 4 hours. During this time period, organic impurities such as binders, dispersants, and some conductive agents in the graphite waste can be effectively removed. If the time is too long, the production efficiency will decrease, and the graphite will be oxidized and ablated, affecting the yield. If the time is too short, it is not conducive to the full removal of organic impurities and affects the electrical properties of the regenerated negative electrode material. The above oxidation treatment time refers to the total duration of the oxidation treatment.

[0059] In some embodiments, the oxidation in a high temperature furnace at 300-800°C includes: raising the temperature to 300-450°C at a heating rate of 3-5°C / min, keeping the temperature for 0.5-1.5h, and continuing to heat the temperature to 450-800°C at a heating rate of 5-10°C / min, and keeping the temperature for 0.5-2.5h.

[0060] There are many types of organic impurities in graphite waste, and the temperatures at which different impurities undergo oxidation reactions are different. By controlling the heating process within the above two stages, the following effects can be achieved: first, the organic impurities can be oxidized as completely as possible, and second, part of the conductive agent can be oxidized, thereby improving the electrical properties of graphite.

[0061] In some embodiments, during the oxidation treatment, the flow rate of the oxidizing gas is 3 to 8 times. Further optimizing the flow rate of the oxidizing gas can control the specific surface area of ​​the recovered graphite, so as to avoid making the specific surface area too small to cause difficulty in removing lithium, and can also take into account a higher graphite yield.

[0062] In some embodiments, oxidation treatment is first performed after pretreatment to remove impurities, and the ash content of the obtained material is ≤2.5% (by weight), or even ≤1.5% (by weight).

[0063] In some embodiments, acid washing is performed after oxidation treatment, and the impurity content of the material obtained by acid washing can be reduced to the following levels (weight ratio): Cu≤20ppm, Si≤100ppm, Fe≤100ppm, S≤200ppm.

[0064] In some embodiments, the mass ratio of the dedoped graphite to the carbon source is 100:(1.5-10), for example, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, 100:5, 100:5.5, 100:6, 100:6.5, 100:7, 100:7.5, 100:8, 100:8.5, 100:9, 100:10, etc.

[0065] When the mass ratio is within this range, the amorphous carbon formed in the subsequent carbonization process can effectively repair the defects of the graphite surface and reduce the consumption of active lithium in the first charge and discharge process. If the carbon source is too little, the defects of the graphite surface cannot be repaired well; if the carbon source is too much, too much amorphous carbon is formed, and the consumption of active ions in the formation of the SEI film increases, and the irreversible capacity loss of the secondary battery increases. In addition, when the mass ratio of the carbon source to the raw material is too large, a large amount of amorphous carbon will remain on the surface of the particles. At this time, the particles are more likely to agglomerate, which not only increases the depolymerization process, but also reduces the gram capacity and compaction density of the obtained carbon material.

[0066] In some embodiments, the carbon source includes asphalt. Asphalt as a carbon source can not only effectively repair the defects on the surface of the graphite, but also limit the specific surface area so that it is not too large.

[0067] In some embodiments, the softening point of the pitch is 90-280° C., for example, 120-250° C., 150-200° C., etc. Pitch with a softening point of 90-280° C. is more effective for surface repair of recycled graphite surfaces.

[0068] The softening point of asphalt refers to the temperature at which asphalt begins to soften, which can be obtained by referring to the standard test method for softening point of asphalt CB / T 4507-84 or ASTM D3104-14a (2018).

[0069] In some embodiments, the carbonization in an inert atmosphere at 1100-1300° C. includes: first heating to 250-300° C. at 3-5° C. / min, keeping warm for 1-2 hours, then heating to 1100-1300° C. at 3-5° C. / min, and keeping warm for 2.5-3.5 hours.

[0070] In the staged heating process, the temperature is first raised to 250°C-300°C. Since the heating temperature is higher than the softening point of the asphalt material, the asphalt material is melted and softened by heat at this time. Keeping it warm for 1h-3h can make it flow evenly and coat the surface of the recycled graphite; then the temperature is raised to 1100-1300°C and kept warm for 1.5-3.5h. At this time, the asphalt material undergoes a carbonization reaction, thereby effectively repairing the defects on the surface of the recycled graphite. In some embodiments, the pretreatment adopts at least one of the following methods:

[0071] Method 1: crush the negative electrode sheets to be recycled, and then separate the graphite waste by air separation;

[0072] Method 2: crush the negative electrode sheets to be recycled, then wash and filter them to collect the graphite waste.

[0073] The above two methods are faster and more efficient for separating the current collector and the graphite system active material, and do not require a large amount of solvent to soak the pole piece to dissolve the adhesive, thereby reducing the amount of solvent used.

[0074] In some embodiments, the volatile matter of the pretreated waste graphite is ≤10.0%, or even ≤5.0%, and the ash content is ≤2.0%, or even ≤1.0%, by weight.

[0075] The present application also provides a negative electrode material obtained by the above recycling method, which can be used to form a secondary battery, a battery module, a battery pack, an electrical device, etc.

[0076] In some embodiments, the first charge efficiency of the negative electrode material obtained in the present application can reach more than 92%, and the specific surface area is 2m 2 / g or less.

[0077] In addition, the secondary battery, battery module, battery pack, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0078] In one embodiment of the present application, a secondary battery is provided.

[0079] 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.

[0080] [Positive electrode]

[0081] 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.

[0082] 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.

[0083] 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.).

[0084] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material in the positive electrode film layer may adopt a positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0085] In some embodiments, when the secondary battery is a sodium ion battery, the positive electrode active material may be a positive electrode active material for a sodium ion battery known in the art. As an example, the positive electrode active material may be used alone or in combination of two or more. Among them, the positive electrode active material may be selected from sodium iron composite oxide (NaFeO2), sodium cobalt composite oxide (NaCoO2), sodium chromium composite oxide (NaCrO2), sodium manganese composite oxide (NaMnO2), sodium nickel composite oxide (NaNiO2), sodium nickel titanium composite oxide (NaNi 1 / 2 Ti 1 / 2 O2), sodium nickel manganese composite oxide (NaNi 1 / 2 Mn 1 / 2 O2), sodium iron manganese composite oxide (Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2), sodium nickel cobalt manganese composite oxide (NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), sodium iron phosphate (NaFePO4), sodium manganese phosphate (NaMn PO4), sodium cobalt phosphate compounds (NaCoPO4), Prussian blue materials, polyanion materials (phosphates, fluorophosphates, pyrophosphates, sulfates), etc., but the present application is not limited to these materials. The present application can also use other traditionally known materials that can be used as positive electrode active materials for sodium ion batteries.

[0086] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0087] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] 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.

[0089] [Negative electrode]

[0090] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector. The negative electrode film layer may include a regenerated negative electrode material obtained by the recycling method of the present invention as a negative electrode active material.

[0091] 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.

[0092] 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.).

[0093] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one 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).

[0094] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0095] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0096] 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.

[0097] [Electrolytes]

[0098] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0099] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0100] In some embodiments, the electrolyte salt can be selected from at least one 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.

[0101] In some embodiments, the solvent can be selected from at least one 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.

[0102] 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.

[0103] [Isolation film]

[0104] 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.

[0105] In some embodiments, the material of the isolation membrane can be selected from at least one 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.

[0106] 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.

[0107] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0108] 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.

[0109] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 1 The secondary battery 5 is a square structure as an example.

[0110] In some embodiments, reference Figure 2 , 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.

[0111] 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.

[0112] Figure 3 4 is an example of a battery module. Figure 3 In 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.

[0113] 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.

[0114] 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.

[0115] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 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.

[0116] In addition, the present application also provides an electrical device, which includes at least one 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 thereto.

[0117] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0118] Figure 6The 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.

[0119] 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.

[0120] Example

[0121] 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.

[0122] Example 1

[0123] The steps for recycling the negative electrode sheets of the intermediate products (i.e. the sheets after cold pressing) in the production process of ternary lithium batteries are as follows.

[0124] The first step is preprocessing

[0125] The scrapped negative electrode plates are coarsely crushed by a hammer crusher, and then the crushed mixture is sent to the next hammer crusher for fine crushing, and then air separation, grading and vibration screening are carried out to obtain negative electrode material I with a Dv50 of 16μm. The separated current collector can also be collected and recycled.

[0126] The second step is oxidation treatment

[0127] The rotary kiln is heated to 600°C at a rate of 5°C / min, the furnace tube speed is 4r / min, and the air flow rate per hour is 4 times the volume of the rotary kiln. The negative electrode material I is added from the feed port, and the material enters the cavity at a uniform speed through the rotary feeder. After oxidizing in the cavity for 4 hours, the material falls into the discharge bag from the discharge port after cooling, and the negative electrode material II with organic impurities removed is obtained.

[0128] Step 3: Pickling

[0129] In the pickling tank, negative electrode material II and acid solution are fed simultaneously and stirred fully. After two picklings, the acid solution composition of the first pickling is a mixed solution of HF: HNO3: HCl = 13: 6: 14 (molar ratio), and the composition of the second pickling is a mixed solution of HNO3: HCl = 5: 2 (molar ratio). The above two pickling processes can be heated appropriately to accelerate the reaction. After the pickling is completed, the negative electrode material III with inorganic impurities removed is obtained by filter pressing, water washing, and drying.

[0130] Step 4: Carbonization

[0131] The negative electrode material III is mixed with asphalt with a Dv50 of 2.5 μm and a softening point of 90°C in a ratio of 100:8, and then carbonized in a carbonization furnace at 1300°C in an inert atmosphere for 4 hours to obtain a regenerated negative electrode material.

[0132] Examples 2 to 12

[0133] The difference from Example 1 is that the heating method or air flow rate of the oxidation treatment in the second step is different, and the rest is the same as Example 1.

[0134] Examples 13 to 23

[0135] The difference from Example 1 is that the type or amount of the carbon source mixed in the fourth step is different, and the rest is the same as Example 1.

[0136] Examples 24 to 25

[0137] The difference from Example 1 is that the coating carbonization conditions in the fourth step are different, and the rest are the same as Example 1.

[0138] Embodiment 26

[0139] The difference from Example 1 is that the source of the recycled negative electrode plates is different, which are the anode plates disassembled from ternary lithium batteries.

[0140] Comparative Example 1

[0141] The difference from Example 1 is that the second step is different, specifically:

[0142] The rotary kiln is heated to 600°C at the same rate, the furnace tube speed is 4r / min, and the nitrogen flow rate is 4 times the volume of the rotary kiln (per hour). The negative electrode material I is added from the feed port, and the material enters the cavity at a uniform speed through the rotary feeder. After heating treatment in the cavity, the material falls into the discharge bag from the discharge port after cooling, and the negative electrode material II is obtained.

[0143] The remaining steps are the same as in Example 1.

[0144] Comparative Example 2

[0145] The difference from Example 1 is that the oxidation temperature in the second step is different, and the oxidation treatment is carried out at a high temperature of 850° C., and the other conditions remain unchanged.

[0146] Comparative Example 3

[0147] The difference from Example 1 is that the oxidation temperature in the second step is different, and the oxidation treatment is carried out at a high temperature of 290° C., and the other conditions remain unchanged.

[0148] Comparative Example 4

[0149] The difference from Example 1 is that the air flow rate during the second step of oxidation is different, that is, the air is introduced at a flow rate of 0.9 times, and the other conditions remain unchanged.

[0150] Comparative Example 5

[0151] The difference from Example 1 is that the air flow rate during the second step of oxidation is different, that is, the air is introduced at a flow rate of 9.2 times, and the other conditions remain unchanged.

[0152] Comparative Example 6

[0153] The difference from Example 1 is that the temperature of the fourth step coating carbonization is different, that is, the carbonization is carried out at 1050° C., and the other conditions remain unchanged.

[0154] Comparative Example 7

[0155] The difference from Example 1 is that the temperature of the fourth step coating carbonization is different, that is, the carbonization is carried out at 1350° C., and the other conditions remain unchanged.

[0156] The relevant parameters of the recovery method of the above-mentioned embodiment and comparative example are shown in the following Table 1.

[0157] Table 1

[0158]

[0159]

[0160]

[0161]

[0162] Note: The phenolic resin in Table 1 refers to the phenolic resin with a residual carbon content of 65%, and the air flow rate (times / h) refers to the multiple of the air flow rate per hour relative to the volume of the rotary kiln.

[0163] In addition, the regenerated negative electrode materials obtained in the above examples and comparative examples were prepared into button cells and secondary batteries as described below, and performance tests were performed. The test results are shown in Table 2 below.

[0164] (1) Specific surface area of ​​recycled negative electrode material

[0165] The specific surface area of ​​carbon materials is a well-known meaning in the art and can be measured by instruments and methods known in the art. For example, it can be measured by nitrogen adsorption specific surface area analysis test method according to GB / T 19587-2017 and calculated by BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.

[0166] (2) Gram capacity of recycled negative electrode material

[0167] The prepared artificial graphite, conductive agent Super P, binder (PVDF) and solvent NMP (N-methylpyrrolidone) are mixed uniformly in a mass ratio of 91.6:1.8:6.6 to prepare a slurry; the prepared slurry is coated on a copper foil current collector, dried in an oven and set aside; a metal lithium sheet is used as a counter electrode; a polyethylene (PE) film is used as an isolation membrane; ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L; the above parts are assembled into a CR2430 button battery in an argon-protected glove box. After the button cell was left to stand for 12 hours, it was discharged at a constant current of 0.05C to 0.005V, left to stand for 10 minutes, and then discharged at a constant current of 50μA to 0.005V, left to stand for 10 minutes, and then discharged at a constant current of 10μA to 0.005V; then it was charged at a constant current of 0.1C to 2V, and the charging capacity was recorded. The ratio of the charging capacity to the mass of the regenerated negative electrode material is the gram capacity of the prepared regenerated negative electrode material.

[0168] (3) Power-off initial test

[0169] Use the same method as point (2) above to test the discharge capacity and charge capacity. The charge capacity and discharge capacity are the first effect of the deduction.

[0170] Table 2: Performance test results of examples and comparative examples

[0171]

[0172]

[0173] According to the above results, the specific capacity and the first efficiency of the graphite treated with a reducing atmosphere are low. At the same time, the oxidation treatment temperature and air flow rate have a great influence on the specific surface area of ​​the material. If the temperature is too high or the air flow rate is too large, the specific surface area will be too large. If the temperature is too low or the air flow rate is too low, the specific surface area will be too small. The use of step-by-step temperature increase oxidation or step-by-step temperature increase carbonization is conducive to further improving the electrical properties of graphite.

[0174] 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 recovering negative electrode materials, characterized in that: The negative electrode material is a graphite system, and the recovery method comprises the following steps: Pre-treating the negative electrode sheet to be recycled so as to separate the current collector from the active material covering the current collector to obtain graphite waste; The graphite waste is subjected to oxidation treatment and pickling to obtain impurity-removed graphite; wherein the oxidation treatment comprises: introducing an oxidizing gas into a reaction furnace to oxidize the graphite slag in a high-temperature furnace at 300 to 800° C., and the amount of the oxidizing gas introduced per hour is 1 to 9 times the volume of the reaction furnace; The de-impurified graphite is coated and carbonized, and the coating and carbonization comprises: mixing the de-impurified graphite with a carbon source, and carbonizing the mixture under an inert atmosphere at 1100-1300° C. to obtain a regenerated negative electrode material.

2. The recycling method according to claim 1, characterized in that: The oxidation treatment time is 1 to 4 hours.

3. The recycling method according to claim 1, characterized in that: The oxidation in a high temperature furnace at 300-800°C includes: raising the temperature to 300-450°C at a heating rate of 3-5°C / min, keeping the temperature for 0.5-1.5h, and continuing to heat up to 450-800°C at a heating rate of 5-10°C / min, and keeping the temperature for 0.5-2.5h.

4. The recycling method according to any one of claims 1 to 3, characterized in that: During the oxidation treatment process, the hourly introduction rate of the oxidizing gas is 3 to 8 times the volume of the reactor.

5. The recycling method according to claim 1, characterized in that: The mass ratio of the de-impurified graphite to the carbon source is 100:(1.5-10).

6. The recycling method according to claim 1 or 5, characterized in that: The carbon source includes pitch.

7. The recycling method according to claim 6, characterized in that: The softening point of the asphalt is 90 to 280°C, preferably 120 to 250°C.

8. The recycling method according to claim 1, characterized in that: The carbonization in an inert atmosphere at 1100-1300° C. includes: firstly heating to 250-300° C. at 3-5° C. / min, keeping the temperature for 1-2 hours, then heating to 1100-1300° C. at 3-5° C. / min, and keeping the temperature for 2.5-3.5 hours.

9. The recycling method according to claim 1, characterized in that: The pretreatment adopts at least one of the following methods: Method 1: crush the negative electrode sheets to be recycled, and then separate the graphite waste by air separation; Method 2: crush the negative electrode sheets to be recycled, then wash and filter them to collect the graphite waste.

10. The recycling method according to claim 1, characterized in that: The particle size Dv50 of the graphite waste is 10 to 18 μm.

11. A negative electrode material, characterized in that: The invention comprises a regenerated negative electrode material obtained by the recovery method according to any one of claims 1 to 10.

12. A secondary battery, characterized in that: It comprises a positive electrode sheet and a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet comprises the negative electrode material according to claim 11.

13. A battery pack, characterized in that: Comprising the secondary battery as claimed in claim 12.

14. An electrical device, characterized in that: The battery comprises at least one selected from the secondary battery of claim 12 or the battery pack of claim 13.

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