CN115842185A

CN115842185A - Method for recovering positive electrode material, positive electrode sheet, and secondary battery

Info

Publication number: CN115842185A
Application number: CN202210519411.6A
Authority: CN
Inventors: 陈祥斌; 史松君; 高凯; 来佑磊
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-05-13
Filing date: 2022-05-13
Publication date: 2023-03-24

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a recovery method of a positive electrode material, a positive electrode plate and a secondary battery. The recovery method comprises the following steps: crushing the positive pole piece containing the current collector layer, and removing the current collector layer to obtain positive pole particles; and cleaning the positive electrode particles by using an acid cleaning agent, and drying to obtain positive electrode powder. According to the method, the acid washing step of cleaning the anode particles by the acidic cleaning agent is added, the rock salt phase and the passivation film on the surfaces of the anode particles can be effectively removed, the layered structure of the anode material is exposed, and the lithium ion embedding in the subsequent lithium supplement roasting process is facilitated, so that the lithium supplement roasting temperature and time are reduced, the recovery efficiency is improved, the cost is saved, and the requirements of the aspects of simple process, less lithium loss and excellent performance of the recovered product can be simultaneously considered compared with the traditional technology.

Description

Method for recovering positive electrode material, positive electrode sheet, and secondary battery

Technical Field

The application relates to the technical field of lithium ion batteries, in particular to a recovery method of a positive electrode material, a positive electrode plate and a secondary battery.

Background

Lithium ion batteries are currently the most widely used secondary batteries due to their high energy density, high capacity and good cycling stability. With the development of electric vehicles and hybrid vehicles, the demand of lithium ion batteries is rapidly increasing, which directly leads to the soaring price of raw materials of lithium ion batteries, especially positive electrode metal materials such as nickel, cobalt, manganese ore and the like, and therefore, research on recovery processes of positive electrode materials containing metals is urgent due to sustainable development and cost considerations.

Disclosure of Invention

Accordingly, there is a need for a method for recovering a positive electrode material, a positive electrode sheet, and a secondary battery, which have a short recovery period, and which are environmentally friendly and inexpensive, and which have good positive electrode material performance, low lithium loss, and a low temperature for lithium supplement firing.

In a first aspect of the present application, there is provided a method for recovering a positive electrode material, comprising the steps of:

crushing the positive pole piece containing the current collector layer, and removing the current collector layer to prepare positive pole particles;

and cleaning the positive electrode particles by using an acid cleaning agent, and drying to obtain positive electrode powder.

According to the technical scheme, the rock salt phase and the passivation film on the surface of the positive electrode particles can be effectively removed by adding the acid washing step of cleaning the positive electrode particles by the acid cleaning agent, the layered structure of the positive electrode material is exposed, and the subsequent lithium ion embedding in the lithium supplement roasting process is facilitated, so that the lithium supplement roasting temperature and time are reduced, the recovery efficiency is improved, the cost is saved, and the requirements of the aspects of simple process, less lithium loss and excellent performance of the recovered product can be simultaneously met compared with the traditional technology.

In some embodiments, the concentration of hydrogen ions in the acidic cleaning agent is 0.05mol/L to 0.5mol/L; preferably, the concentration of hydrogen ions is 0.15mol/L to 0.35mol/L. The proper hydrogen ion concentration can control the acid washing reaction speed, and on the premise that the rock salt phase and the passivation film can be thoroughly removed, excessive lithium layers cannot be dissolved, so that unnecessary loss is caused.

In some embodiments, the amount of the acidic cleaning agent is 0.5L to 3L per 1kg of the positive electrode particles; preferably, the dosage of the acidic cleaning agent is 1L-2L for every 1kg of the positive electrode particles. The dosage ratio of the anode particles to the acidic cleaning agent is controlled within a proper range, so that the rock salt phase and the passive film can be removed more thoroughly without causing unnecessary loss.

In some embodiments, the disruption treatment is a mechanical disruption treatment.

In some embodiments, the temperature at which the positive electrode particles are dried is from 100 ℃ to 150 ℃. The drying temperature is controlled within a proper range, so that the anode particles can be effectively dried, excessive energy consumption is avoided, and the production cost is reduced.

In some embodiments, the overall particle size distribution of the cathode particles is controlled to range from 2 μm to 30 μm. The particle size distribution of the anode particles is controlled within a proper range, so that the rock salt phase and the passivation film can be removed more thoroughly by acid washing treatment, and the lithium can be better supplemented in the subsequent lithium supplementing roasting process.

In some embodiments, before the crushing treatment, any one of step a, step B and step C is further included;

step A: soaking the positive pole piece containing the current collector layer in a carbonate solvent, taking out and drying;

and B: roasting the positive pole piece containing the current collector layer for 4-8 h at the temperature of 300-500 ℃ in an oxygen-containing gas atmosphere;

and C: and soaking the positive pole piece containing the current collector layer in a carbonate solvent, taking out and drying, and then roasting for 4-8 h at 300-500 ℃ in an oxygen-containing gas atmosphere.

Before the crushing treatment, the anode plate is soaked, so that the residual electrolyte and additives on the surface of the plate can be removed, and HF and PF are prevented from being generated during roasting treatment ₅ And the like toxic substances; the anode plate is roasted before crushing treatment, so that the residual conductive carbon and the adhesive on the surface of the electrode plate can be removed,further improving the subsequent lithium supplement effect; the temperature and time of the roasting treatment are controlled within a proper range, so that the loss of lithium can be reduced as much as possible while the conductive carbon and the binder are effectively removed, sintering is avoided, and the treatment is difficult.

In some embodiments, the carbonate-based solvent includes one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, propylene 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, and 1, 4-butyrolactone.

In some embodiments, the soaking time is 4 to 30 hours. The soaking time is controlled within a proper range, and the electrolyte and additives remained on the surface of the pole piece can be effectively removed.

In some embodiments, the temperature of the anode plate comprising the current collector layer after soaking and drying is 80-150 ℃. The drying temperature after soaking is controlled within a proper range, so that the residual carbonate solvent after soaking and taking out can be thoroughly volatilized, and adverse effects on subsequent processes are avoided.

In some embodiments, the method further comprises the step of performing lithium supplement roasting on the positive electrode powder to obtain a roasted positive electrode material;

wherein the temperature of the lithium supplement roasting is 500-800 ℃, and the time of the lithium supplement roasting is 4-12 h; preferably, the temperature of the lithium supplement roasting is 600-700 ℃, and the time of the lithium supplement roasting is 4-8 h. The temperature and time of lithium supplement roasting are controlled within a proper range, nickel and lithium mixed discharge can be reduced when lithium supplement is effectively carried out, the influence on capacity exertion of a battery prepared by a recovered anode material in a follow-up mode is avoided, the resistance of the battery is prevented from being increased, and meanwhile, the influence on lithium ion transmission efficiency caused by the fact that the specific surface area is smaller due to excessive increase of primary particles is also prevented.

In some embodiments, the lithium supplement agent used in the lithium supplement firing includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium fluoride, lithium acetate, lithium formate, and lithium citrate.

In some embodiments, the gas atmosphere of the lithium replenishing calcination is an oxygen-containing gas atmosphere.

In some embodiments, the ratio of the amount of lithium element in the positive electrode powder to the amount of lithium element in the lithium supplement agent is 1 (0.1-0.18). The dosage range of the lithium supplement agent is particularly limited depending on the recovery process, the dosage of the lithium supplement agent is controlled within a proper range, and the lithium can be fully supplemented, so that excessive lithium is effectively prevented from being separated out on the particle surface, the pH value on the particle surface is higher, water is easily absorbed to generate gel, the coating use is influenced, the impedance is increased, and the cycle performance and the rate capability of the battery are reduced.

In some embodiments, after the lithium supplement roasting operation, the method further comprises the step of crushing and demagnetizing the roasted positive electrode material to obtain a regenerated positive electrode material.

In some embodiments, the regenerated cathode material is controlled to have an overall particle size distribution ranging from 2 μm to 30 μm. The particle size distribution of the regenerated anode material is controlled in a proper range, so that the specific surface area is proper when a battery is subsequently prepared, and the activity of the anode material is exerted to a greater extent.

In some embodiments, the positive electrode sheet comprising the current collector layer is disassembled after the lithium ion battery is discharged in the electrolyte solution. Put into the electrolyte solution with lithium ion battery, be equivalent to the short circuit environment, can make the battery fully discharge, eliminate on the one hand and disassemble the risk, on the other hand makes lithium ion can the at utmost to inlay back to the positive pole and is convenient for retrieve.

In some embodiments, the solute of the electrolyte solution comprises one or more of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, potassium sulfate, sodium carbonate, and potassium carbonate.

In some embodiments, in the positive electrode sheet including the current collector layer, the positive active material includes one or more of a binary positive electrode material, a ternary positive electrode material, and a quaternary positive electrode material. By adopting the recovery process, the anode material is not particularly limited, and the recovery process can be suitable for recovering various conventional binary, ternary and quaternary anode materials and has a wide application range.

In some embodiments, the binary positive electrode material comprises one or more of lithium nickel manganese oxide, lithium nickel cobalt oxide, lithium nickel aluminum oxide, lithium nickel magnesium oxide, and lithium nickel iron oxide.

In some embodiments, the ternary positive electrode material comprises one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel cobalt magnesium oxide, and lithium nickel cobalt ferrite.

In some embodiments, the quaternary positive electrode material comprises one or more of lithium nickel cobalt manganese aluminate, lithium nickel cobalt manganese magnesiate, and lithium nickel cobalt manganese ferrite.

In a second aspect of the present application, there is provided a positive electrode material obtained by the recycling method according to any one of the foregoing embodiments.

In a third aspect of the present application, a positive electrode sheet is provided, which includes the aforementioned positive electrode material.

In a fourth aspect of the present application, a secondary battery is provided, which includes the aforementioned positive electrode sheet.

Drawings

Fig. 1 is a view showing regenerated positive electrode material particles recovered in example 1;

fig. 2 is the regenerated positive electrode material particles recovered in comparative example 1;

fig. 3 is a schematic view of a secondary battery according to an embodiment of the present application.

Fig. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in fig. 3.

Fig. 5 is a schematic diagram of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Description of reference numerals:

1 a secondary battery; 11 a housing; 12 an electrode assembly; and 13, covering the plate.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the application, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise. In the description of the present application, "a plurality" means at least one, e.g., one, two, etc., unless explicitly specified otherwise.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In the present application, the technical features described in the open manner include a closed technical solution including the listed features, and also include an open technical solution including the listed features.

In the present application, reference is made to numerical ranges which are considered to be continuous within the numerical ranges, unless otherwise specified, and which include the minimum and maximum values of the range, as well as each and every value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range-describing features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein.

The percentage contents referred to in the present application mean, unless otherwise specified, mass percentages for solid-liquid mixing and solid-solid phase mixing, and volume percentages for liquid-liquid phase mixing.

The percentage concentrations referred to in this application, unless otherwise specified, refer to the final concentrations. The final concentration refers to the ratio of the added component in the system after the component is added.

The temperature parameter in the present application is not particularly limited, and may be a constant temperature treatment or a treatment within a certain temperature range. The constant temperature process allows the temperature to fluctuate within the accuracy of the instrument control.

The "particles" or substances defining the particle size distribution referred to in this application do not necessarily have a spherical shape, but may have a random shape, and may be primary particles or secondary particles. The particle size of the random particles is the average of the maximum and minimum diameters.

At present, two main processes for recovering the cathode material are provided, namely a wet recovery method and a direct recovery method. The wet recovery process is to dissolve valuable metals such as nickel, cobalt, manganese, lithium and the like in the waste anode material by acid, then generate the metals into an anode material precursor by a coprecipitation method, and evaporate and crystallize the filtered solution to obtain lithium salt and recover the lithium salt; and roasting the precursor through lithium mixing to obtain the regenerated anode material. The direct recovery process is to supplement lithium to the waste anode material and then directly roast the waste anode material to obtain the regenerated anode material. The anode material obtained by wet recovery has high purity and wide application range, but the process is complicated and long in period, more metal loss is caused in the coprecipitation process, and a large amount of ammonia-alkali waste liquid is caused by coprecipitation to pollute the environment. The anode material obtained by the traditional direct recovery process has fewer working procedures, short period and high recovery rate of valuable metals, is suitable for large-scale recovery, but has poor purity compared with a fresh material, can undergo irreversible phase transition in the circulation process to generate an inactive rock salt phase NiO, and the surface of the anode material reacts with electrolyte to generate a passivation film (CEI film), wherein the rock salt phase and the passivation film are disordered structures, and supplementary lithium ions migrate to the interior of particles to be hindered, and on the other hand, the rock salt phase and the passivation film need high energy when regenerated into a hexagonal layered structure, so that the temperature and time required by roasting can be increased.

Therefore, aiming at the defects of complex wet recovery process, poor direct recovery purity, high lithium supplement roasting temperature and long time in the prior art, the application provides a recovery method of a cathode material, which comprises the following steps:

crushing the positive pole piece containing the current collector layer, and removing the current collector layer to obtain positive pole particles;

In the present application, the term "method for recovering a positive electrode material" refers to a method for recovering a positive electrode material by treating a positive electrode sheet to be recovered. The recovered object is the positive pole piece, the recovered product is the positive pole material, and the recovered product is taken as a discussion main body when discussing the traditional process.

According to the technical scheme, through increasing the acid washing step that acid cleaning agent washs anodal granule, can effectively get rid of the rock salt phase and the passive film on anodal granule surface, expose the lamellar structure of anodal material itself, be favorable to follow-up interpolation of lithium ion among the lithium roasting process of benefit to reduce benefit lithium roasting temperature and time, improve recovery efficiency, practice thrift the cost, and compare in the prior art can compromise direct recovery method simple process simultaneously, the lithium loss is few and wet recovery method retrieves the advantage that product property is good.

In some embodiments, the concentration of hydrogen ions in the acidic cleaning agent is 0.05mol/L to 0.5mol/L; preferably, the concentration of hydrogen ions is 0.15mol/L to 0.35mol/L. The concentration of hydrogen ions in the acidic cleaning agent may be, for example, 0.1mol/L, 0.15mol/L, 0.2mol/L, 0.25mol/L, 0.3mol/L, 0.35mol/L, 0.4mol/L, or 0.45mol/L. The proper hydrogen ion concentration can control the acid washing reaction speed, and on the premise that the rock salt phase and the passivation film can be thoroughly removed, excessive lithium layers cannot be dissolved, so that unnecessary loss is caused.

In some embodiments, the amount of the acidic cleaning agent is 0.5L to 3L per 1kg of the positive electrode particles; preferably, the amount of the acid cleaning agent is 1L to 2L per 1kg of the positive electrode particles. The amount of the acidic cleaning agent to be used per 1kg of the positive electrode particles may be 1.5L or 2.5L, for example. The dosage ratio of the anode particles to the acidic cleaning agent is controlled within a proper range, so that the rock salt phase and the passive film can be removed more thoroughly without causing unnecessary loss.

In some embodiments, the crushing treatment is a mechanical crushing treatment.

In some embodiments, the temperature at which the positive electrode particles are dried is from 100 ℃ to 150 ℃. The temperature at which the positive electrode particles are dried may also be, for example, 120 ℃, 130 ℃, or 140 ℃. The drying temperature is controlled within a proper range, so that the anode particles can be effectively dried, excessive energy consumption is avoided, and the production cost is reduced.

In some embodiments, the overall particle size distribution of the positive electrode particles is controlled to range from 2 μm to 30 μm. The overall particle size distribution range of the positive electrode particles may be, for example, 3 to 25 μm, 3 to 18 μm, 5 to 20 μm, or 8 to 15 μm. The particle size distribution of the anode particles is controlled in a proper range, so that rock salt phase and a passive film can be removed more thoroughly through acid washing treatment, and the method is favorable for better lithium supplement in subsequent lithium supplement roasting.

and B: roasting the positive pole piece containing the current collector layer for 4-8 h at the temperature of 300-500 ℃ in an oxygen-containing gas atmosphere; the calcination temperature may also be 350 ℃, 400 ℃ or 450 ℃, and the calcination time may also be 5h, 6h or 7h;

and C: soaking the positive pole piece containing the current collector layer in a carbonate solvent, taking out and drying, and then roasting for 4-8 h at 300-500 ℃ in an oxygen-containing gas atmosphere; the calcination temperature may also be 350 ℃, 400 ℃ or 450 ℃, and the calcination time may also be 5h, 6h or 7h; .

Before the crushing treatment, the anode plate is soaked, so that the residual electrolyte and additives on the surface of the electrode plate can be removed, and the method can be used for preventing the electrode plate from being brokenHF and PF are generated during baking-free treatment ₅ And the like toxic substances; the anode plate is roasted before crushing treatment, so that residual conductive carbon and binder on the surface of the plate can be removed, and the subsequent lithium supplement effect is further improved; the temperature and time of the roasting treatment are controlled within a proper range, so that the loss of lithium can be reduced as much as possible while the conductive carbon and the binder are effectively removed, sintering is avoided, and the treatment is difficult.

In some embodiments, the soaking time is 4 to 30 hours. The soaking time may also be, for example, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, or 28h. The soaking time is controlled within a proper range, and the electrolyte and additives remained on the surface of the pole piece can be effectively removed.

In some embodiments, the temperature for drying the positive electrode sheet comprising the current collector layer after soaking is 80 ℃ to 150 ℃. The drying temperature may be, for example, 90 ℃, 100 ℃,120 ℃, 130 ℃ or 140 ℃. The drying temperature after soaking is controlled within a proper range, so that the residual carbonate solvent after soaking and taking out can be thoroughly volatilized, and adverse effects on subsequent processes are avoided.

wherein the temperature of the lithium supplement roasting is 500-800 ℃, and the time of the lithium supplement roasting is 4-12 h; preferably, the temperature of the lithium supplement roasting is 600-700 ℃, and the time of the lithium supplement roasting is 4-8 h; further preferably, the temperature of the lithium supplement roasting is 600 ℃, and the time of the lithium supplement roasting is 6h. The temperature and time of lithium supplement roasting are controlled within a proper range, nickel and lithium mixed discharge can be reduced when lithium supplement is effectively carried out, the influence on capacity exertion of a battery prepared by a recovered anode material in a follow-up mode is avoided, the resistance of the battery is prevented from being increased, and meanwhile, the influence on lithium ion transmission efficiency caused by the fact that the specific surface area is smaller due to excessive increase of primary particles is also prevented.

In some embodiments, the gas atmosphere for the supplemental lithium firing is an oxygen-containing gas atmosphere.

In some embodiments, the ratio of the amount of lithium in the positive electrode powder to the amount of lithium in the lithium replenishing agent is 1 (0.1 to 0.18). The ratio of the amount of lithium element in the positive electrode powder material to the amount of lithium element in the lithium supplement agent may be 1. The dosage range of the lithium supplement agent is particularly limited depending on the recovery process, the dosage of the lithium supplement agent is controlled within a proper range, and the lithium can be fully supplemented, so that excessive lithium is effectively prevented from being separated out on the particle surface, the pH value on the particle surface is higher, water is easily absorbed to generate gel, the coating use is influenced, the impedance is increased, and the cycle performance and the rate capability of the battery are reduced.

In some embodiments, after the lithium supplement roasting operation, the method further comprises the step of crushing and demagnetizing the roasted positive electrode material to obtain the regenerated positive electrode material.

In some embodiments, the overall particle size distribution of the controlled regeneration cathode material ranges from 2 μm to 30 μm. The regenerated positive electrode material may have an overall particle size distribution range of, for example, 3 to 25 μm, 3 to 18 μm, 5 to 20 μm, or 8 to 15 μm. The particle size distribution of the regenerated anode material is controlled in a proper range, so that the specific surface area is proper during the subsequent preparation of the battery, and the activity of the anode material is exerted to a greater extent.

In some embodiments, the positive electrode sheet comprising the current collector layer is disassembled after the lithium ion battery is discharged in the electrolyte solution. The lithium ion battery is put into the electrolyte solution, which is equivalent to providing a short-circuit environment, so that the battery can be fully discharged, on one hand, the risk of disassembly is eliminated, and on the other hand, the lithium ion can be embedded into the anode to the maximum extent so as to be convenient for recovery.

In some embodiments, a lithium ion battery is discharged with a sodium chloride solution. Preferably, the concentration of the sodium chloride solution is 0.1mol/L to 1mol/L, and may be, for example, 0.3mol/L, 0.5mol/L, 0.7mol/L, or 0.9mol/L. The proper electrolyte solution type and concentration can help the lithium ion battery to discharge better and make the lithium ion to be embedded into the positive electrode better.

As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g., liNiO) ₂ ) Lithium manganese oxides (e.g., liMnO) ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/3 Mn _1/3 O ₂ (may also be abbreviated as NCM) ₃₃₃ )、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (may also be abbreviated as NCM) ₅₂₃ )、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (may also be abbreviated as NCM) ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (may also be abbreviated as NCM) ₆₂₂ )、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (may also be abbreviated as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxides (e.g., liNi) _0.85 Co _0.15 Al _0.05 O ₂ ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) ₄ (may also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

In some embodiments, the binary positive electrode material comprises lithium nickel manganese oxide (e.g., liNi) _0.6 Mn _0.4 O ₂ May also be referred to simply as NM ₆₄ ) One or more of lithium nickel cobaltate, lithium nickel aluminate, lithium nickel magnesium oxide and lithium nickel ferrite.

In some embodiments, the ternary positive electrode material comprises lithium nickel cobalt manganese oxide (e.g., liNi) _0.6 Co _0.2 Mn _0.2 O ₂ May also be referred to as NCM for short ₆₂₂ ) One or more of lithium nickel cobalt aluminate, lithium nickel cobalt magnesium oxide and lithium nickel cobalt ferrite.

The secondary battery and the electric device according to the present invention will be described below with reference to the drawings as appropriate.

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

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. In the process of charging and discharging the battery, active ions are embedded and separated back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable ions to pass through.

Positive pole piece

The positive pole piece includes the anodal mass flow body and sets up the anodal rete on anodal mass flow body at least one surface, anodal rete includes the cathode material of this application second aspect.

As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.

In some embodiments, the positive electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum 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 base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the positive electrode film layer further optionally includes 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 fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the components for preparing the positive pole piece, such as the positive pole material, the conductive agent, the binder and any other components, in a solvent (such as N-methyl pyrrolidone) to form positive pole slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.

Negative pole piece

The negative pole piece includes the negative pole mass flow body and sets up the negative pole rete on the negative pole mass flow body at least one surface, the negative pole rete includes negative pole active material.

As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector.

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

In some embodiments, the negative active material may employ a negative active material for a battery known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate and the like. The silicon-based material can be at least one selected from the group consisting of elemental silicon, a silicon oxy compound, a silicon carbon compound, a silicon nitrogen compound and a silicon alloy. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material may also be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the anode film layer further optionally includes a binder. The binder may be at least one selected from 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).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the negative electrode film layer may also optionally include other adjuvants, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet can be prepared by: dispersing the above components for preparing a negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying, cold pressing and the like to obtain the negative electrode pole piece.

Electrolyte

The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The electrolyte is not particularly limited and may be selected as desired. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolytic solution. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may 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, sulfolane, dimethylsulfone, methylethylsulfone, and diethylsulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery, such as an additive for improving overcharge properties of the battery, an additive for improving high-temperature or low-temperature properties of the battery, and the like.

Isolation film

In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known separator having a porous structure and good chemical and mechanical stability may be used.

In some embodiments, the material of the isolation film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The outer package of the secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

The shape of the secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other shape. For example, fig. 3 is a secondary battery 1 of a square structure as an example.

In some embodiments, referring to fig. 4, the overpack may include a shell 11 and a cover 13. The housing 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity. The housing 11 has an opening communicating with the accommodating chamber, and a cover plate 13 can be provided to cover the opening to close the accommodating chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 12 through a winding process or a lamination process. An electrode assembly 12 is enclosed within the receiving cavity. The electrolyte is impregnated into the electrode assembly 12. The number of the electrode assemblies 12 included in the secondary battery 1 may be one or more, and those skilled in the art may select them according to specific practical needs.

In addition, this application still provides an electric installation, electric installation includes the secondary battery that this application provided. The secondary battery may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The electric device may include, but is not limited to, a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, and the like. The mobile device may be, for example, a mobile phone, a notebook computer, or the like; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, or the like, but is not limited thereto.

As the electricity-consuming device, a secondary battery may be selected according to its usage requirements.

Fig. 5 shows an electric device 2 as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle and the like.

As another example, the device may be a cell phone, a tablet, a laptop, etc.

The present application will be described in further detail with reference to specific examples and comparative examples. Experimental parameters not described in the following specific examples are preferably referred to the guidelines given in the present application, and may be referred to experimental manuals in the art or other experimental methods known in the art, or to experimental conditions recommended by the manufacturer. It is understood that the following examples are specific to the particular apparatus and materials used, and in other embodiments, are not limited thereto; the weight of the related components mentioned in the embodiments of the present specification may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the embodiments of the present specification as long as it is scaled up or down according to the embodiments of the present specification. Specifically, the weight described in the specification of the examples of the present application may be in units of mass known in the chemical and chemical fields, such as μ g, mg, g, and kg.

Example 1

(1) Discharging the waste NCM622 battery cell in NaCl solution (concentration: 0.3 mol/L) for 24h, disassembling, and separating the positive and negative electrode plates, the diaphragm and the electrolyte to obtain a waste positive electrode plate;

(2) Soaking the waste positive pole piece prepared in the step (1) in dimethyl carbonate for 24 hours to remove residual electrolyte and additives on the surface of the pole piece, filtering, and drying the soaked pole piece at 80 ℃;

(3) Roasting the pole piece prepared in the step (2) for 5 hours at 500 ℃ in an air atmosphere of 101.325kPa to remove impurities such as conductive carbon, adhesive and the like remained on the surface of the pole piece;

(4) Mechanically crushing the pole piece roasted in the step (3), separating an aluminum foil current collector, and sieving with a 200-mesh sieve to obtain positive electrode particles with the particle size of 3-18 microns;

(5) Cleaning the positive electrode particles prepared in the step (4) by using 0.1mol/L sulfuric acid aqueous solution, wherein 1L of sulfuric acid aqueous solution is used for every 1kg of positive electrode particles, drying the filtered positive electrode particles at 110 ℃ to obtain positive electrode powder, and detecting the loss amount of lithium in the positive electrode powder by using an ICP (inductively coupled plasma Spectroscopy) instrument;

(6) Mixing the positive electrode powder prepared in the step (5) with lithium hydroxide (the amount ratio of lithium element substances is 1; and naturally cooling after baking, mechanically crushing, sieving by a 200-mesh sieve, and demagnetizing to obtain the regenerated ternary positive electrode particles with the particle size of 3-18 microns.

Example 2

Substantially the same as in example 1 except that the aqueous sulfuric acid solution in the step (5) had a concentration of 0.3mol/L.

Example 3

Substantially in accordance with example 1, except that 2L of the aqueous sulfuric acid solution was used per 1kg of the positive electrode pellets in step (5).

Example 4

Substantially in accordance with example 1, except that the ratio of the amount of the substance of lithium element in the positive electrode powder to that of lithium element in the lithium hydroxide in step (6) is 1.

Example 5

Substantially the same as in example 1 except that the calcination temperature in step (6) was 800 ℃.

Example 6

Substantially the same as in example 1 except that the calcination time in step (6) was 10 hours.

Example 7

(1) Discharging the waste NM64 battery cell in NaCl solution (concentration: 0.3 mol/L) for 24h, disassembling, and separating the positive and negative pole pieces, the diaphragm and the electrolyte to obtain waste positive pole pieces;

(2) Soaking the waste positive pole piece prepared in the step (1) in ethylene carbonate for 12 hours to remove residual electrolyte and additives on the surface of the pole piece, filtering, and drying the soaked pole piece at 120 ℃;

(3) Roasting the pole piece prepared in the step (2) for 8 hours at 400 ℃ in an oxygen atmosphere of 101.325kPa to remove impurities such as conductive carbon, adhesive and the like remained on the surface of the pole piece;

(5) Cleaning the positive electrode particles prepared in the step (4) by using 0.5mol/L hydrochloric acid aqueous solution, wherein 0.5L hydrochloric acid aqueous solution is used for every 1kg of positive electrode particles, drying the filtered positive electrode particles at 100 ℃ to obtain positive electrode powder, and detecting the loss amount of lithium in the positive electrode powder by using an ICP (inductively coupled plasma Spectroscopy) instrument;

(6) Mixing the positive electrode powder prepared in the step (5) with lithium carbonate (the amount ratio of lithium element substances is 1; and naturally cooling after baking, mechanically crushing, sieving by a 200-mesh sieve, and demagnetizing to obtain the regenerated binary anode particles with the particle size of 3-18 microns.

Comparative example 1

Substantially the same as in example 1 except that the acid washing treatment of step (5) was not included.

Comparative example 2

Substantially in accordance with example 1, except that the soaking treatment and the drying treatment of step (2) are not included.

Comparative example 3

Fresh NCM622 positive active material.

Comparative example 4

Substantially in accordance with example 1, except that the calcination temperature in step (3) was 700 ℃.

Comparative example 5

Substantially the same as in example 1 except that the concentration of the aqueous sulfuric acid solution in the step (5) was 0.8mol/L.

Comparative example 6

Substantially the same as in example 1 except that the concentration of the aqueous sulfuric acid solution in the step (5) was 0.01mol/L.

Comparative example 7

Comparative example 8

Substantially in accordance with example 1, except that the calcination temperature in step (6) was 1000 ℃.

The positive electrode materials obtained in the above examples and comparative examples were subjected to characterization tests, and the positive electrode materials were respectively prepared into lithium ion batteries for performance tests.

1. Characterization of relevant parameters of cathode material

(1) Volume average particle size distribution test

The equipment model is as follows: malvern 2000 (MasterSizer 2000) laser granulometer, reference standard procedure: GB/T19077-2016/ISO 13320, concrete test flow: taking a proper amount of a sample to be detected (the concentration of the sample can ensure 8-12% of light shading degree), adding 20ml of deionized water, simultaneously performing external super-5 min (53 kHz/120W) to ensure that the sample is completely dispersed, and then determining the sample according to GB/T19077-2016/ISO 13320.

(2) Topography testing

The positive electrode materials prepared in example 1 and comparative example 1 were tested by a ZEISS sigma 300 scanning electron microscope, and then by reference to standard JY/T010-1996, and the morphology of the sample was observed, and the results are shown in FIGS. 1 and 2, respectively, and it can be seen from comparison of FIGS. 1 and 2 that the positive electrode material of comparative example 1 without pickling had a rough surface, had a laminar deposit, and was a residual by-product and a rock salt phase layer. The surface of the sample of example 1 after acid washing is smooth, which shows that the acid washing can effectively remove the attachments on the particle surface and provide more channels for the insertion of the supplementary lithium ions.

2. Preparation of lithium ion battery

(1) Preparation of positive pole piece

The positive electrode material, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) in each example and comparative example were mixed at a weight ratio of 97:1.5:1.5, adding a solvent N-methyl pyrrolidone (NMP) in a mixing manner, and uniformly mixing to obtain anode slurry; and then uniformly coating the positive electrode slurry on a positive electrode current collector, and then drying, cold pressing and cutting to obtain the positive electrode piece.

(2) Preparation of lithium ion battery

And (2) stacking the positive pole piece prepared in the step (1), an isolation film and a negative pole piece in sequence to enable the isolation film to be positioned between the positive pole piece and the negative pole piece to play an isolation role, then winding to obtain a naked electric core, welding a tab for the naked electric core, packaging the naked electric core into an aluminum shell, baking at 100 ℃ to remove water, immediately injecting electrolyte and sealing to obtain the uncharged battery. And the uncharged battery sequentially undergoes the working procedures of standing, hot and cold pressing, formation, shaping, capacity testing and the like to obtain the lithium ion battery.

3. Battery performance testing

(1) Battery capacity retention rate test

Lithium ion batteries prepared from the positive electrode materials of the examples and the comparative examples were subjected to constant current charging at 45 ℃ at 1/3C to 4.3V, further subjected to constant voltage charging at 4.3V to a current of 0.05C, left for 5min, and then discharged at 1/3C to 2.8V, and the obtained capacity was recorded as initial capacity C0. When the above steps are repeated for the same battery and the discharge capacity Cn of the battery after the nth cycle is recorded, the battery capacity retention ratio Pn = Cn/C0 × 100% after each cycle.

In the test process, the first cycle corresponds to n =1, the second cycle corresponds to n =2, \8230, and the 200 th cycle corresponds to n =200. The battery capacity retention ratio data corresponding to example 1 in table 1 is data measured after 200 cycles under the above-described test conditions, i.e., the value of P200.

(2) Specific capacitance capacity test

At 25 ℃, lithium ion batteries prepared from the cathode materials of the examples and the comparative examples are charged to 4.3V at a constant current of 1/3C, then charged to a current of 0.05C at a constant voltage of 4.3V, left for 5min, and then discharged to 2.8V at 1/3C, and the obtained capacity is recorded as initial capacity C0, specific capacity = C0/(m × 97%), and m is the coating weight of the cathode active material of the battery core.

(3) Rate capability test

Lithium ion batteries prepared from the positive electrode materials of the examples and the comparative examples were charged at a constant current of 1/3C to 4.3V at 25 ℃, charged at a constant voltage of 4.3V to a current of 0.05C, left for 5min, discharged at 0.1C to 2.8V, and the average of the capacities obtained after 5 cycles was recorded as an initial capacity D0. Then, the battery was charged under the same conditions as described above, discharged at 1C and 2C, respectively, and the average of the capacities obtained after 5 cycles was taken as the initial capacity D1-2. The capacity retention ratio Qn per battery rate discharge is calculated according to the following formula:

Qn＝(Dn/D0)×100％。

the above characterization test results are shown in table 1:

TABLE 1

As can be seen from table 1, the positive electrode materials recovered in the embodiments of the present application all have higher specific capacity and good capacity retention rate, and particularly, in embodiment 2, the acid with a better concentration is used for cleaning, so that the baking temperature and time are more appropriate, various performances of the battery prepared can be greatly improved, and the performance of the battery is not much different from that of the battery prepared from a brand-new NCM622 positive electrode active material (comparative example 3).

Compared with the embodiment 1, the comparative example 1 without acid washing treatment can cause the surface of the positive electrode material to remain by-products and rock salt phases, and the specific capacity and the capacity retention rate are both obviously reduced; comparative example 2, which did not undergo soaking and drying, resulted in HF and PF being generated during calcination ₅ And the like, and the performance of the recycled anode material is also adversely affected, so that the specific capacity and capacity retention rate of the prepared battery are reduced; in comparative example 4, the higher calcination temperature in step (3) results in higher lithium loss rate, so that the performance of the prepared battery is reduced compared with that of example 1 under the condition of using the same amount of the lithium supplement agent as that of example 1, and if the calcination temperature is continuously increased to be higher than 900 ℃, particles are sintered, are not easy to sieve, and have higher lithium loss; in comparative example 5, too high acid concentration resulted in too large loss of lithium, which was a significant performance degradation compared to example 1; in comparative example 6, the pickling concentration was too low to achieve the technical effect well, and the performance was only slightly improved compared to comparative example 1 without pickling; in comparative example 7, excessive lithium supplement agent can cause excessive residual lithium, so that the surface pH of the particles is too high and water is easily absorbed, gel is generated in the mixing and stirring process of battery core preparation, the coating use is affected, the impedance is increased, and the cycle and rate performance of the battery are reduced; in comparative example 8, too high a firing temperature in step (6) resulted in lithiumThe source loss increases, and the lithium source is taken away the part along with the air current after melting, and the higher the temperature, the loss is bigger, and can cause the nickel lithium to arrange the increase thoughtlessly, influences battery capacity performance, and resistance increase, simultaneously, still can lead to once granule increase, and the specific surface reduces, influences lithium ion transmission efficiency, and the performance deteriorates seriously.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several implementation modes of the present application, and the description thereof is specific and detailed, but not construed as limiting the scope of the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the patent is subject to the appended claims, and the description and the drawings can be used for explaining the contents of the claims.

Claims

1. A method for recovering a positive electrode material, comprising the steps of:

2. The recovery method according to claim 1, wherein the concentration of hydrogen ions in the acidic cleaning agent is 0.05 to 0.5mol/L;

preferably, the concentration of hydrogen ions is 0.15mol/L to 0.35mol/L.

3. The recovery method according to claim 2, wherein the amount of the acidic cleaning agent used is 0.5 to 3L per 1kg of the positive electrode particles;

preferably, the dosage of the acidic cleaning agent is 1L-2L for every 1kg of the positive electrode particles.

4. The recycling method according to claim 1, wherein the crushing treatment is a mechanical crushing treatment; and/or

The drying temperature of the positive electrode particles is 100-150 ℃; and/or

The overall particle size distribution range of the positive electrode particles is controlled to be 2-30 mu m.

5. The recycling method according to claim 1, further comprising any one of step a, step B and step C before the crushing treatment;

6. The recycling method according to claim 5, wherein the carbonate-based solvent includes one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, propylene 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, and 1, 4-butyrolactone; and/or

The soaking time is 4-30 h; and/or

The temperature of the anode pole piece containing the current collector layer after soaking and drying is 80-150 ℃.

7. The recycling method according to any one of claims 1 to 6, further comprising a step of subjecting the positive electrode powder to lithium supplement firing to obtain a fired positive electrode material;

wherein the temperature of the lithium supplement roasting is 500-800 ℃, and the time of the lithium supplement roasting is 4-12 h; preferably, the temperature of the lithium supplement roasting is 600-700 ℃, and the time of the lithium supplement roasting is 4-8 h; and/or

The lithium supplement agent adopted by the lithium supplement roasting comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium fluoride, lithium acetate, lithium formate and lithium citrate; and/or

The gas atmosphere of the lithium supplement roasting is oxygen-containing gas atmosphere.

8. The recovery method according to claim 7, wherein the ratio of the amount of the lithium element in the positive electrode powder to the amount of the lithium element in the lithium replenishing agent is 1 (0.1 to 0.18).

9. The recycling method according to claim 7, further comprising a step of subjecting the baked positive electrode material to crushing treatment and demagnetizing treatment after the lithium replenishing baking operation to obtain a regenerated positive electrode material.

10. The recovery method according to claim 9, wherein the overall particle size distribution of the regenerated positive electrode material is controlled to be in a range of 2 μm to 30 μm.

11. The recovery method according to any one of claims 1 to 6 and 8 to 10, wherein the positive electrode sheet comprising the current collector layer is obtained by disassembling a lithium ion battery after discharging in an electrolyte solution.

12. A recovery method according to claim 11, wherein the solute of the electrolyte solution includes one or more of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, potassium sulfate, sodium carbonate and potassium carbonate.

13. The recycling method according to any one of claims 1 to 6, 8 to 10 and 12, wherein the positive electrode active material in the positive electrode sheet including the current collector layer comprises one or more of a binary positive electrode material, a ternary positive electrode material and a quaternary positive electrode material.

14. The recycling method according to claim 13, wherein the binary positive electrode material comprises one or more of lithium nickel manganese oxide, lithium nickel cobalt oxide, lithium nickel aluminum oxide, lithium nickel magnesium oxide, and lithium nickel iron oxide; and/or

The ternary positive electrode material comprises one or more of nickel cobalt lithium manganate, nickel cobalt lithium aluminate, nickel cobalt lithium magnesium and nickel cobalt lithium iron; and/or

The quaternary positive electrode material comprises one or more of nickel cobalt manganese lithium aluminate, nickel cobalt manganese lithium magnesiate and nickel cobalt manganese lithium ferrite.

15. A positive electrode material obtained by the recovery method according to any one of claims 1 to 14.

16. A positive electrode sheet comprising the positive electrode material according to claim 15.

17. A secondary battery comprising the positive electrode sheet according to claim 16.