WO2024045028A1

WO2024045028A1 - Positive electrode material and preparation method therefor, positive electrode composite material and preparation method therefor, secondary battery, and electric device

Info

Publication number: WO2024045028A1
Application number: PCT/CN2022/116146
Authority: WO
Inventors: 魏冠杰; 古力; 孟阵; 赵延杰; 李星
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-08-31
Filing date: 2022-08-31
Publication date: 2024-03-07

Abstract

A positive electrode material, comprising positive electrode material particles and a coating layer located on the surfaces of the positive electrode material particles. The material of the coating layer comprises an antioxidant, and the antioxidant comprises one or more of a hindered phenol antioxidant and an amine antioxidant.

Description

Cathode materials and preparation methods thereof, positive electrode composite materials and preparation methods thereof, secondary batteries and electrical devices

Technical field

This application is in the technical field of secondary batteries, and more specifically relates to positive electrode materials and preparation methods thereof, positive electrode composite materials and preparation methods thereof, secondary batteries and electrical devices.

Background technique

The statements herein merely provide background information relevant to the present application and do not necessarily constitute prior art.

Due to the shortage of petrochemical energy and the deterioration of the natural environment, the share of new energy vehicles in the automobile market is gradually increasing, and there is the possibility of replacing oil vehicles in the future. Since a car is a high-power consumption device, the rate performance and cycle performance of the battery directly affect the user experience. Therefore, how to improve the rate performance and cycle performance of secondary batteries is a research hotspot in the field.

Contents of the invention

According to various embodiments of the present application, a cathode material and a preparation method thereof, a cathode composite material and a preparation method thereof, a secondary battery and an electrical device are provided.

A first aspect of the application provides a cathode material, including cathode material particles and a coating layer located on the surface of the cathode material particles. The material of the coating layer includes antioxidants, and the antioxidants include hindered phenols. One or more of antioxidants and amine antioxidants.

During long-term cycling, the positive electrode active material is prone to fragmentation, forming positive electrode material particles. The exposed fresh surfaces of these positive electrode material particles are highly oxidizing, which will continue to consume the electrolyte and reduce the rate performance and cycle performance of the battery. By selecting a suitable type of antioxidant to form a coating layer on the surface of the cathode material particles, the electrolyte consumption caused by the oxidation of the cathode material particles can be effectively improved without causing obvious negative effects on other battery performance, and can effectively increase the battery rate. performance and cycle performance.

In some embodiments, the hindered phenolic antioxidant includes 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-aminophenol, 2,6-di-tert-butyl-4-aminophenol, One or more of butyl-4-(dimethylaminomethyl)phenol, tert-butylhydroquinone and 2,5-di-tert-butylhydroquinone. The aforementioned hindered phenolic antioxidants not only have good antioxidant properties, but will not have a negative impact on other battery performance, and can form a good coating on the positive electrode material particles.

In some embodiments, the amine antioxidants include N,N'-di-sec-butyl-p-phenylenediamine, (3,5-di-tert-butyl-4-hydroxybenzyl)aniline, 2,2, 6,6-Tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1-octyloxy-2,2,6,6 -Tetramethyl-4-piperidinyl) sebacate, stearic acid (2,2,6,6-tetramethyl-4-piperidinol) ester and N,N'-bis(2,2 , one or more of 6,6-tetramethyl-4-piperidinyl)-1,3-benzenedicarboxamide. The aforementioned amine antioxidants not only have good antioxidant properties, but will not have a negative impact on other battery performance, and can form a good coating on the positive electrode material particles.

In some embodiments, the mass percentage of the antioxidant in the cathode material is 0.1% to 3%. The appropriate dosage of antioxidants can not only provide antioxidant properties, but also form a coating layer with appropriate coating density to avoid adverse effects on the transmission of lithium ions, and will not occupy too much of the mass of the cathode material, resulting in a decrease in battery energy density. .

In some embodiments, the material of the coating layer further includes a conductive agent;

Optionally, the conductive agent includes one or more of polypyrrole conductive agents, polyaniline conductive agents, and functional conductive carbon;

Further optionally, the functional conductive carbon includes one or more of carbon nanotubes, carbon black and graphite, and the surface of the functional conductive carbon is grafted with one or more of carboxyl, hydroxyl and amino groups.

The introduction of conductive agents containing carboxyl, hydroxyl or amino groups into the coating layer can, on the one hand, form hydrogen bonds with antioxidants and improve the binding force between antioxidants and cathode material particles; on the other hand, it can form hydrogen bonds between cathode particles. Form a conductive network to prevent the positive electrode material particles from being deactivated from electrical contact after cyclic breakage, affecting the battery's electrical performance. Especially conductive agents containing amino groups, because the amino nitrogen atoms contain lone pairs of electrons, have strong electronegativity and can absorb metal ions eluted from the cathode material, which is beneficial to improving the cycle performance of the battery.

In some embodiments, the mass percentage of the conductive agent in the cathode material is 0.5% to 10%. Appropriate conductive dosage can not only provide conductive performance and improve the binding force between antioxidants and cathode material particles, but also form a coating layer with appropriate coating density to avoid adverse effects on the transmission of lithium ions and not occupy too much of the cathode material. quality, resulting in a decrease in battery energy density.

In some embodiments, the cathode material is primary particles, and the Dv50 particle size of the cathode material ranges from 100 nm to 1 μm. Appropriate particle size can make it easier to prepare secondary particles with uniform particle size distribution from primary particles.

In some embodiments, the thickness of the coating layer is 2 nm ~ 100 nm; optionally, the thickness of the coating layer is 2 nm ~ 50 nm; further optionally, the thickness of the coating layer is 5 nm ~ 30 nm . The appropriate coating layer thickness will not hinder the transmission of lithium ions and affect battery performance while providing sufficient oxidation resistance and conductivity.

In some embodiments, the cathode material particles include LiCoO ₂ , _LiNia Co _b Mn _(1-ab) O ₂ , _LiNic Co _d Al _(1-cd) O ₂ , eLi ₂ MnO ₃ ·(1-e ) one or more of LiMO ₂ ;

Among them, a~e are independently selected from 0~1;

M includes one or more of Ni, Co and Mn.

Suitable types of cathode material particles are more suitable for various parameters such as the thickness of the coating layer in this application, thereby further improving the oxidation resistance and conductivity of the cathode material particles.

A second aspect of the application provides a method for preparing the cathode material described in one or more of the aforementioned embodiments, including the following steps:

The raw materials related to the cathode material described in one or more of the aforementioned embodiments are prepared, and each raw material is ball milled.

In some embodiments, the ball mill meets one or more of the following conditions (1) to (7):

(1) The ball milling medium includes one or more of zirconium balls, stainless steel balls and polyurethane balls;

(2) The diameter of the ball milling medium is 5mm~20mm;

(3) The ball milling medium includes large balls and small balls, the diameter of the large ball is 10mm~20mm, and the diameter of the small ball is 5mm~10mm; optionally, the mass percentage of the small ball in the ball milling medium The content is 10% to 30%, and the mass percentage of the large balls in the ball milling medium is 70% to 90%;

(4) The mass ratio of raw materials to ball milling media is (10~20):1;

(5) The ball mill is a wet ball mill, and the solvent used includes one of chloroform, acetone, toluene and benzene; optionally, the mass ratio of the raw material to the solvent is 1: (1-10);

(6) The rotation speed of the ball mill is 400rpm~600rpm;

(7) The ball milling time is 0.5h~2h.

Appropriate ball milling process parameters are more conducive to forming a coating layer that is uniform, suitable in thickness, and has good binding force with the cathode material particles, thereby improving the rate performance and cycle performance of the battery.

A third aspect of the application provides a cathode composite material, including the cathode material described in one or more of the aforementioned embodiments and a lithium-containing binder;

Optionally, the lithium-containing binder includes one or more of lithium carboxymethylcellulose, lithium polyacrylate, and lithium alginate.

Preparing the aforementioned positive electrode materials and lithium-containing binders into positive electrode composite materials can improve the dispersion during pulping, avoid agglomeration due to particles that are too small, and avoid the shedding of the coating layer caused by mechanical friction during pulping. , In addition, the compaction density of the pole piece can be increased. And because the binder contains lithium, it can further enhance the conductivity of lithium ions, thereby further improving the rate performance of the battery.

In some embodiments, in the cathode composite material, the mass percentage of the lithium-containing binder is 1% to 10%. The appropriate dosage of lithium-containing binder can provide sufficient adhesion while avoiding the decrease in battery energy density caused by excessive dosage.

In some embodiments, in the cathode composite material, the mass percentage of the cathode material is 90% to 99%.

In some embodiments, the positive electrode composite material is a secondary particle, and the Dv50 particle size of the positive electrode composite material ranges from 5 μm to 20 μm. Appropriate particle size can make the cathode composite material more dispersible during pulping and make the active material layer more uniform, which is beneficial to improving the electrical performance of the battery and reducing resistance.

The fourth aspect of this application provides a method for preparing the cathode composite material according to one or more of the aforementioned embodiments, including the following steps:

The positive electrode material, the lithium-containing binder and the solvent are mixed and spray granulated.

In some embodiments, the temperature of the spray granulation is 120°C to 140°C, and the discharge speed of the spray granulation is 5mL/min to 20mL/min. Appropriate spray granulation process parameters help to form a positive electrode composite material with uniform particle size distribution and uniform distribution of positive electrode materials.

A fifth aspect of the present application provides a secondary battery, including a positive electrode plate, a negative electrode plate and a separator, the isolation film being disposed between the positive electrode sheet and the negative electrode sheet;

Wherein, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes the positive electrode material described in one or more of the aforementioned embodiments and the aforementioned positive electrode material. One or more of the cathode composite materials described in one or more embodiments.

In some embodiments, the cathode active material layer further includes an auxiliary antioxidant, and the auxiliary antioxidant includes one or more of phosphite and thioester;

Optionally, the mass percentage of the auxiliary antioxidant in the positive active material layer is 0.01% to 2%.

The introduction of auxiliary antioxidants can further improve the antioxidant performance. The appropriate dosage of auxiliary antioxidants balances the contradiction between antioxidant properties and energy density.

A sixth aspect of the present application provides a battery module, which includes the aforementioned secondary battery.

A seventh aspect of the present application provides a battery pack, which includes the aforementioned battery module.

An eighth aspect of the present application provides an electrical device, which includes one or more of the aforementioned secondary batteries, battery modules, and battery packs.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the application will become apparent from the description, drawings and claims.

Description of drawings

To better describe and illustrate embodiments or examples of those inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the drawings should not be construed as limiting the scope of any of the disclosed inventions, the embodiments or examples presently described, or the best modes currently understood of these inventions.

FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

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

Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .

FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.

Explanation of reference symbols:

1: Battery pack; 2: Upper box; 3: Lower box; 4: Battery module; 5: Secondary battery; 51: Shell; 52: Electrode assembly; 53: Cover; 6: Electrical device.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

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

How to improve the rate performance and cycle performance of secondary batteries has always been a research hotspot in the battery field. There are many factors that affect rate performance and cycle performance. For example, a large number of studies have found that the cathode active material is prone to fragmentation during long-term cycling, forming cathode material particles. The exposed fresh surfaces of these cathode material particles have strong oxidation properties. The electrolyte will continue to be consumed, adversely affecting the rate performance and cycle performance of the battery.

Based on the above background, the first aspect of this application provides a cathode material, including cathode material particles and a coating layer located on the surface of the cathode material particles. The material of the coating layer includes antioxidants. The antioxidants include hindered phenolic antioxidants. agent and one or more of amine antioxidants.

This application forms a coating layer on the surface of the cathode material particles by selecting appropriate types of antioxidants. The hydrogen atoms in these antioxidants can fall off from the antioxidant molecules during the cycle, combined with the free peroxide formed due to the oxidation reaction in the battery. radicals, thereby eliminating free radicals, inhibiting further oxidation reactions of peroxyl radicals, effectively improving the electrolyte consumption caused by the oxidation of the positive electrode material particles, and not causing obvious negative effects on other performance of the battery, which can effectively improve the performance of the battery. Rate performance and cycle performance.

In some embodiments, the hindered phenolic antioxidants include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-aminophenol, 2,6-di-tert-butyl -One or more of 4-(dimethylaminomethyl)phenol, tert-butylhydroquinone and 2,5-di-tert-butylhydroquinone. The aforementioned hindered phenolic antioxidants not only have good antioxidant properties, but will not have a negative impact on other battery performance, and can form a good coating on the positive electrode material particles.

In some embodiments, amine antioxidants include N,N'-di-sec-butyl-p-phenylenediamine, (3,5-di-tert-butyl-4-hydroxybenzyl)aniline, 2,2,6, 6-Tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1-octyloxy-2,2,6,6-tetrakis Methyl-4-piperidinyl) sebacate, stearic acid (2,2,6,6-tetramethyl-4-piperidinol) ester and N,N'-bis(2,2,6 , one or more of 6-tetramethyl-4-piperidinyl)-1,3-benzenedicarboxamide. The aforementioned amine antioxidants not only have good antioxidant properties, but will not have a negative impact on other battery performance, and can form a good coating on the positive electrode material particles.

In some embodiments, the mass percentage of antioxidant in the cathode material is 0.1% to 3%. The appropriate dosage of antioxidants can not only provide antioxidant properties, but also form a coating layer with appropriate coating density to avoid adverse effects on the transmission of lithium ions, and will not occupy too much of the mass of the cathode material, resulting in a decrease in battery energy density. .

Further optionally, the functional conductive carbon includes one or more of carbon nanotubes, carbon black and graphite, and the surface of the functional conductive carbon is grafted with one or more of carboxyl groups, hydroxyl groups and amino groups.

The introduction of conductive agents containing carboxyl, hydroxyl or amino groups into the coating layer can, on the one hand, form hydrogen bonds with antioxidants and improve the binding force between antioxidants and cathode material particles; on the other hand, it can form hydrogen bonds between cathode particles. Form a conductive network to prevent the positive electrode material particles from being detached from electrical contact and deactivated after cycle breakage, affecting the battery rate performance. Especially conductive agents containing amino groups, because the amino nitrogen atoms contain lone pairs of electrons, have strong electronegativity and can absorb metal ions eluted from the cathode material, which is beneficial to improving the cycle performance of the battery.

Preferably, the conductive agent includes one or more of polypyrrole conductive agents, polyaniline conductive agents, and carbon nanotubes; further preferably, the conductive agent includes one or more of polypyrrole conductive agents and polyaniline conductive agents. Kind or variety. Linear conductive agents such as polypyrrole, polyaniline and carbon nanotubes are conducive to forming a more comprehensive coating on the surface of the cathode material particles. Especially polypyrrole and polyaniline are more flexible and are more conducive to the coating layer. form.

In some embodiments, the weight average molecular weight range of the polypyrrole-based conductive agent and the polyaniline-based conductive agent is independently from 100,000 Da to 1,000,000 Da. Alternatively, the weight average molecular weight ranges of the polypyrrole conductive agent and the polyaniline conductive agent can be independently, for example, 200,000 Da, 300,000 Da, 400,000 Da, 500,000 Da, 600,000 Da, and 700,000 Da. , 800,000 Da or 900,000 Da. A suitable weight average molecular weight can make the conductive agent have a suitable size, which is more conducive to the formation of the coating layer, and makes it easier to form a coating layer with a suitable coating density.

In some embodiments, the diameter of the carbon nanotube ranges from 5 nm to 100 nm, and the length ranges from 20 μm to 80 μm. Alternatively, the diameter of the carbon nanotube can be, for example, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm or 95nm; carbon The length of the nanotubes can also be, for example, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm or 75 μm. Carbon nanotubes of appropriate size are more conducive to the formation of coating layers, and it is easier to form coating layers with suitable coating density.

In some embodiments, carbon black and graphite have Dv50 particle size ranges of 30 nm to 150 nm, respectively. Alternatively, the Dv50 particle size ranges of carbon black and graphite may also be independently, for example, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm or 40 nm. Carbon black or graphite with suitable particle size is more conducive to the formation of the coating layer, and it is easier to form a coating layer with suitable coating density.

In some embodiments, the mass percentage of the conductive agent in the cathode material is 0.5% to 10%. Alternatively, the mass percentage of the conductive agent may also be, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%. Appropriate conductive dosage can not only provide conductive properties and improve the binding force between antioxidants and cathode material particles, but also form a coating layer with appropriate coating density to avoid adverse effects on the transmission of lithium ions and not occupy too much of the cathode material. quality, resulting in a decrease in battery energy density.

In some embodiments, the cathode material is primary particles, and the Dv50 particle size of the cathode material ranges from 100 nm to 1 μm. Alternatively, the Dv50 particle size of the cathode material may be, for example, 150 nm to 550 nm, or may also be 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm or 900 nm. Appropriate particle size can make it easier to prepare secondary particles with uniform particle size distribution from primary particles.

In this application, Dv50 refers to the particle size corresponding to when the cumulative volume distribution number of particles reaches 50% in the volume cumulative distribution curve of particle size. Its physical meaning is that the particle size is smaller (or larger) than the particle size value. The volume ratio is 50% each. As an example, Dv50 can be easily measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the United Kingdom, referring to the GB/T 19077-2016 particle size distribution laser diffraction method.

In some embodiments, the thickness of the cladding layer ranges from 2 nm to 100 nm; optionally, the thickness of the cladding layer ranges from 2 nm to 50 nm; further optionally, the thickness of the cladding layer ranges from 5 nm to 30 nm. The thickness of the cladding layer may also be, for example, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm or 95 nm. The appropriate coating layer thickness will not hinder the transmission of lithium ions and affect battery performance while providing sufficient oxidation resistance and conductivity.

In some embodiments, the cathode material particles include LiCoO ₂ , _LiNia Co _b Mn _(1-ab) O ₂ , _LiNic Co _d Al _(1-cd) O ₂ , eLi ₂ MnO ₃ ·(1-e)LiMO one or more of ₂ ;

Among them, a~e are independently selected from 0~1;

M includes one or more of Ni, Co and Mn.

For example, a to e can also be independently selected from 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9.

The second aspect of this application provides a method for preparing the cathode material of one or more of the aforementioned embodiments, including the following steps:

The raw materials related to the cathode material according to one or more of the aforementioned embodiments are prepared, and each raw material is ball milled.

In some embodiments, ball milling meets one or more of the following conditions (1) to (7):

(2) The diameter of the ball milling medium is 5mm to 20mm; the diameter of the ball milling medium can also be, for example, 10nm or 15nm;

(3) The ball milling medium includes large balls and small balls. The diameter of the large balls is 10mm ~ 20mm, and the diameter of the small balls is 5mm ~ 10mm; optionally, the mass percentage of the small balls in the ball milling medium is 10% ~ 30 %, the mass percentage of large balls in the ball milling medium is 70% to 90%; the mass percentage of small balls in the ball milling medium can also be, for example, 15%, 20% or 25%; the mass percentage of large balls in the ball milling medium The mass percentage can also be, for example, 75%, 80% or 85%;

(4) The mass ratio of raw materials to ball milling media is (10~20):1; the mass ratio of raw materials to ball milling media can also be, for example, 12:1, 14:1, 16:1 or 18:1;

(5) The ball mill is a wet ball mill, and the solvent used includes one of chloroform, acetone, toluene and benzene; optionally, the mass ratio of the raw material to the solvent is 1: (1 ~ 10); the mass ratio of the raw material to the solvent For example, it can also be 1:2, 1:4, 1:6 or 1:8;

(6) The rotation speed of the ball mill is 400rpm to 600rpm; the rotation speed of the ball mill can also be, for example, 450rpm, 500rpm or 550rpm;

(7) The ball milling time is 0.5h to 2h; the ball milling time can also be, for example, 1h or 1.5h.

A third aspect of the application provides a cathode composite material, including the cathode material of one or more of the aforementioned embodiments and a lithium-containing binder;

In some embodiments, in the positive electrode composite material, the mass percentage of the lithium-containing binder is 1% to 10%. Alternatively, the mass percentage of the lithium-containing binder may be, for example, 1.5% to 5%, or may also be 2%, 4%, 6% or 8%. The appropriate dosage of lithium-containing binder can provide sufficient adhesion while avoiding the decrease in battery energy density caused by excessive dosage.

In some embodiments, in the cathode composite material, the mass percentage of the cathode material is 90% to 99%. The mass percentage in the cathode material may also be, for example, 92%, 94%, 96% or 98%.

In some embodiments, the positive electrode composite material is a secondary particle, and the Dv50 particle size of the positive electrode composite material ranges from 5 μm to 20 μm. The Dv50 particle size of the positive electrode composite material may also be, for example, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, or 18 μm. Appropriate particle size can make the cathode composite material more dispersible during pulping and make the active material layer more uniform, which is beneficial to improving the electrical performance of the battery and reducing resistance.

The fourth aspect of this application provides a method for preparing the cathode composite material of one or more of the aforementioned embodiments, including the following steps:

Mix the positive electrode material, lithium-containing binder and solvent, and perform spray granulation.

In some embodiments, the temperature of spray granulation is 120°C to 140°C, and the discharge speed of spray granulation is 5mL/min to 20mL/min. Alternatively, the temperature of spray granulation can also be, for example, 125°C, 130°C, or 135°C; the discharge speed of spray granulation can also be, for example, 10 mL/min or 15 mL/min. Appropriate spray granulation process parameters help to form a positive electrode composite material with uniform particle size distribution and uniform distribution of positive electrode materials.

Wherein, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes the positive electrode material of one or more of the aforementioned embodiments and the positive electrode material of one or more of the aforementioned embodiments. One or more types of positive electrode composite materials.

In some embodiments, the cathode active material layer also includes an auxiliary antioxidant, and the auxiliary antioxidant includes one or more of phosphite and thioester;

Optionally, the mass percentage of the auxiliary antioxidant in the positive active material layer is 0.01% to 2%. Alternatively, the amount of auxiliary antioxidant can also be, for example, 0.5%, 1% or 1.5%.

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

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

Typically, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charging and discharging process of the battery, active ions are inserted and detached back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes. The isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.

Positive electrode piece

The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes a conventional positive electrode active material, the positive electrode material of the first aspect of the present application, and the positive electrode composite of the third aspect of the present application. one or more of the materials.

As an example, the positive electrode current collector has two surfaces facing each other in its own 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.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can 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 can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the conventional cathode active material may be a cathode active material known in the art for batteries. As an example, a conventional cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, 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 of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO ₂ ), lithium nickel oxides (such as LiNiO ₂ ), lithium manganese oxides (such as LiMnO ₂ , LiMn ₂ O ₄ ), 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 Mn _1/3 O ₂ (also referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (can also be abbreviated to NCM ₅₂₃ ), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (can also be abbreviated to NCM ₂₁₁ ), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (can also be abbreviated to NCM ₆₂₂ ), LiNi At least one of _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM ₈₁₁ ), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and its modified compounds. The olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.

In some embodiments, the positive electrode film layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

In some embodiments, the positive electrode film layer optionally further 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 can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.

Negative pole piece

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

As an example, the negative electrode current collector has two opposite surfaces in its own 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.

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 can 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 material. The composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the negative active material may be a negative active material known in the art for batteries. As an example, the negative 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 may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys. 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 traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.

In some embodiments, the negative electrode film layer optionally further includes a binder. The binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer optionally further 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 optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.

In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.

electrolyte

The electrolyte plays a role in conducting ions between the positive and negative electrodes. There is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs. For example, the electrolyte can be liquid, gel, or completely solid.

In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes electrolyte salts and solvents.

In some embodiments, the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.

In some embodiments, the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

In some embodiments, the electrolyte optionally further includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

Isolation film

In some embodiments, the secondary battery further includes a separator film. There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.

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 film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.

In some embodiments, the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer packaging. The outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.

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 bag, such as a bag-type soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, FIG. 1 shows a square-structured secondary battery 5 as an example.

In some embodiments, referring to FIG. 2 , the outer package may include a housing 51 and a cover 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity. The positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte soaks into 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.

In some embodiments, secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.

Figure 3 is a battery module 4 as an example. Referring to FIG. 3 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.

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

In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

Figures 4 and 5 show the battery pack 1 as an example. Referring to FIGS. 4 and 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 2 and a lower box 3 . The upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.

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 by the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device. The electrical devices may include mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc. , but not limited to this.

As the electric device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

FIG. 6 shows an electrical device 6 as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the electrical device, a battery pack or battery module can be used.

As another example, the device may be a mobile phone, a tablet, a laptop, etc. The device is usually required to be thin and light, and a secondary battery can be used as a power source.

The present application will be further described in detail below in conjunction with specific examples and comparative examples. For experimental parameters not specified in the following specific examples, priority is given to the guidelines given in the application documents. You can also refer to experimental manuals in the field or other experimental methods known in the field, or refer to the experimental conditions recommended by the manufacturer. It can be understood that the instruments and raw materials used in the following examples are relatively specific, and in other specific examples, they may not be limited thereto; the weight of relevant components mentioned in the examples of this application does not only refer to the specific content of each component. , can also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the relevant components is scaled up or down according to the embodiments of this application, it is within the scope disclosed in the embodiments of this application. Specifically, the weight described in the description of the embodiments of this application may be mass units well-known in the field of chemical engineering such as μg, mg, g, kg, etc.

Example 1

(1) Preparation of positive electrode pieces

a. Combine 0.4Li ₂ MnO ₃ ·0.6LiNi _0.5 Mn _0.5 O ₂ (recorded as lithium-rich material), 2,6-di-tert-butyl-4-methylphenol (BHT), polypyrrole (weight average molecular weight 300,000 Da) Prepare materials according to 97.5:0.5:2, use zirconium beads as ball milling media (large balls with a diameter of 15mm account for 80%, small balls with a diameter of 5mm account for 20%), and control the mass ratio of raw materials to ball milling media to 15:1. Dry ball milling at a rotation speed of 500rpm for 1 hour to obtain a positive electrode material with a Dv50 particle size of 300nm. In the positive electrode material, the thickness of the coating layer is 20nm;

b. Dissolve the cathode material prepared in step a into a lithium carboxymethylcellulose (CMC-Li) aqueous solution with a mass concentration of 2%, and stir at 800 rpm for 3 hours to obtain a premixed liquid (in the premixed liquid, the cathode The mass ratio of the material to lithium carboxymethyl cellulose is 100:3), then use nitrogen as the carrier gas, control the discharging speed to 10mL/min, and perform spray granulation at 120°C to obtain a positive electrode with a Dv50 particle size of 8 μm. composite materials;

c. Mix the cathode composite material prepared in step b, the conductive agent acetylene black, and the binder PVDF (polyvinylidene fluoride) in a weight ratio of 94:4:2, add the solvent N-methylpyrrolidone, and stir thoroughly. The positive electrode slurry is uniformly obtained, and then coated on both surfaces of the positive electrode current collector aluminum foil. After drying and cold pressing, the positive electrode sheet is obtained.

(2) Preparation of negative electrode pieces

Mix artificial graphite, conductive agent acetylene black, binder SBR (styrene-butadiene rubber latex), and binder CMC (sodium carboxymethyl cellulose) in a weight ratio of 95:1.5:3.1:0.4, and add solvent deionized water , stir thoroughly and mix evenly to obtain a negative electrode slurry, which is then coated on both surfaces of the negative electrode current collector copper foil, dried and cold pressed to obtain a negative electrode piece.

(3) Preparation of electrolyte

In an argon atmosphere glove box with a water content of <10ppm, mix EC (ethylene carbonate), PC (polycarbonate), and DMC (dimethyl carbonate) in a weight ratio of EC:PC:DMC=3:3:3 Mix, then add LiPF ₆ , VC, DTD and PS, stir evenly to obtain an electrolyte, in which the concentration of LiPF ₆ lithium ion battery electrolyte is 1 mol/L, and the mass percentages of VC, DTD and PS are 3% respectively. , 1%, 1%.

(4) Preparation of isolation film

Polyethylene porous membrane is used as the isolation membrane.

(5) Preparation of lithium-ion secondary batteries

Stack the positive electrode piece prepared in step (1), the isolation film in step (4), and the negative electrode piece prepared in step (2) in order, so that the isolation film is between the positive and negative electrodes to play an isolation role. A bare battery core is obtained; the bare battery core is placed in an outer package, the electrolyte prepared in step (3) is injected and packaged for formation to obtain a lithium ion secondary battery.

Example 2

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 94.5:3.5:2, and the resulting positive electrode The Dv50 particle size of the material is 390nm, and the thickness of the coating layer is 60nm.

Example 3

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 95:3:2, and the resulting positive electrode The Dv50 particle size of the material is 360nm, and the thickness of the coating layer is 40nm.

Example 4

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 97.9:0.1:2, and the resulting positive electrode The Dv50 particle size of the material is 280nm, and the thickness of the coating layer is 7nm.

Example 5

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 97.5:0.5:2, and the resulting positive electrode The Dv50 particle size of the material is 100nm, and the thickness of the coating layer is 15nm.

Example 6

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 97.5:0.5:2, and the resulting positive electrode The Dv50 particle size of the material is 1000nm, and the thickness of the coating layer is 25nm.

Example 7

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 97.95:0.05:2, and the resulting positive electrode The Dv50 particle size of the material is 270nm, and the thickness of the coating layer is 4nm.

Example 8

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 87.5:0.5:12, and the resulting positive electrode The Dv50 particle size of the material is 450nm, and the thickness of the coating layer is 110nm.

Example 9

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 89.5:0.5:10, and the resulting positive electrode The Dv50 particle size of the material is 430nm, and the thickness of the coating layer is 100nm.

Example 10

Basically the same as Example 1, except that in step (1)a, the mass ratio of lithium-rich material, 2,6-di-tert-butyl-4-methylphenol, and polypyrrole is 99.4:0.5:0.1, and the resulting positive electrode The Dv50 particle size of the material is 260nm, and the thickness of the coating layer is 2nm.

Example 11

It is basically the same as Example 1, except that in step (1)a, polypyrrole is replaced by an equal amount of carbon nanotubes (diameter 50 nm, length 30 μm), and amino groups are grafted on the surface of the carbon nanotubes.

Example 12

It is basically the same as Example 1, except that in step (1)a, the polypyrrole is replaced by an equal amount of carbon black (Dv50 particle size 80 nm), and the surface of the carbon black is grafted with amino groups.

Example 13

It is basically the same as Example 1, except that in step (1)a, polypyrrole is not included, and the mass ratio of the lithium-rich material and 2,6-di-tert-butyl-4-methylphenol is 99.5:0.5.

Example 14

Basically consistent with Example 1, the difference is that in step (1) b, in the premix, the mass ratio of the cathode material to carboxymethylcellulose lithium is 85:15.

Example 15

It is basically the same as Example 1, except that in step (1) b, in the premix, the mass ratio of the cathode material to lithium carboxymethyl cellulose is 90:10.

Example 16

It is basically the same as Example 1, except that in step (1) b, in the premix, the mass ratio of the cathode material to lithium carboxymethyl cellulose is 99:1.

Example 17

It is basically the same as Example 1, except that in step (1)b, the temperature of spray granulation is 100°C, and the Dv50 particle size of the obtained cathode composite material is 22 μm.

Example 18

It is basically the same as Example 1, except that in step (1)b, the temperature of spray granulation is 160°C.

Example 19

It is basically the same as Example 1, except that in step (1)b, the discharge speed of spray granulation is 2 mL/min, and the Dv50 particle size of the obtained cathode composite material is 3 μm.

Example 20

It is basically the same as Example 1, except that in step (1)b, the discharge speed of spray granulation is 25 mL/min, and the Dv50 particle size of the obtained cathode composite material is 23 μm.

Example 21

It is basically the same as Example 1, except that LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (denoted as high nickel material) is used instead of lithium-rich material. The Dv50 particle size of the obtained cathode material is 190 nm, and the thickness of the coating layer is 20 nm.

Example 22

It is basically the same as Example 1, except that step (1)a is as follows:

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (recorded as high nickel material), N,N'-di-sec-butyl-p-phenylenediamine (antioxidant 44PD), polyaniline (weight average molecular weight 500,000 Da) according to 97.5: 0.5:2 preparation, using zirconium beads with a diameter of 15mm as the ball milling medium, controlling the mass ratio of raw materials to ball milling media to 10:1, using acetone (the amount of acetone is 5 times the mass of the raw materials) as the solvent, at a rotation speed of 400rpm After wet ball milling for 2 hours, a positive electrode material with a Dv50 particle size of 200 nm was obtained. In the positive electrode material, the thickness of the coating layer was 25 nm.

Step (1)c is as follows:

Mix the cathode composite material prepared in step b, phosphite, conductive agent acetylene black, and binder PVDF (polyvinylidene fluoride) in a weight ratio of 94:2:2:2, and add the solvent N-methylpyrrolidone. , stir thoroughly and mix evenly to obtain a positive electrode slurry, which is then coated on both surfaces of the positive electrode current collector aluminum foil, dried and cold-pressed to obtain a positive electrode piece.

Comparative example 1

It is basically the same as Example 1, except that in step (1)a, 2,6-di-tert-butyl-4-methylphenol (BHT) is replaced by FeS of equal mass.

Comparative example 2

Basically the same as Example 1, the difference is that in step (1)a, there is no 2,6-di-tert-butyl-4-methylphenol (BHT), 0.4Li ₂ MnO ₃ ·0.6LiNi _0.5 Mn _0.5 O ₂ (described as lithium-rich material) and polypyrrole mass ratio is 98:2.

Comparative example 3

Basically the same as Example 1, the difference is that step (1)a is not included, and the cathode material in step (1)b is replaced with 0.4Li ₂ MnO ₃ ·0.6LiNi _0.5 Mn _0.5 O ₂ with a Dv50 particle size of 280nm (note as lithium-rich materials).

Characterization test:

The secondary batteries prepared in the above examples and comparative examples were subjected to the following tests, and the test results are listed in Table 1.

(1) Capacity test

At 25°C, charge the secondary battery with a constant current of 0.33C rate to 4.55V, then charge with a constant voltage until the current is 0.05C, let it stand for 5 minutes, and then discharge it with a constant current of 0.33C rate to 2V, record the discharge at this time Capacity is 0.33C discharge capacity.

(2) Rate performance test

At 25°C, the secondary batteries of each example and comparative example were charged to 4.55V at a constant current rate of 0.1C, then charged at a constant voltage until the current was 0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.1C to 2V, record the discharge capacity at this time, which is the 0.1C discharge capacity; let it stand for 30 minutes, then charge the secondary battery with a constant current at a rate of 0.1C to 4.55V, then charge with a constant voltage until the current is 0.05C, and let it stand for 5 minutes. Then discharge at a constant current of 1C to 2V, and record the discharge capacity at this time, which is the 1C discharge capacity.

The rate performance of the battery is 1C/0.1C (%) = 1C discharge capacity/0.1C discharge capacity × 100%.

(3)Cycle performance test

At 25°C, charge to 4.55V with a constant current of 1C, then charge with a constant voltage of 4.55V until the current drops to 0.05C, and then discharge to 2.5V with a constant current of 1C to obtain the first-week discharge specific capacity (Cd1); Charge and discharge are repeated in this way until the 500th cycle, and the discharge specific capacity after 500 cycles is obtained as Cdn.

Capacity retention rate=discharge specific capacity after 500 cycles (Cdn)/discharge specific capacity in the first cycle (Cd1).

In the above battery performance test process, the upper limit charging voltage of lithium-rich materials is 4.55V, and the upper limit charging voltage of high-nickel materials is 4.25V.

Table 1

Analyzing the data in Table 1, compared with Example 1, in Comparative Example 1, the hindered phenolic antioxidant was replaced by FeS, which can also be used as an antioxidant daily. However, since the antioxidant performance of FeS is based on its reducibility, therefore, When used as a cathode material, charging will cause most ferrous ions to be oxidized into ferric ions and lose their antioxidant properties. The performance is equivalent to Comparative Example 2 without antioxidants. Therefore, not all antioxidants are suitable for the solution of this application. . In Comparative Example 3, the polypyrrole conductive agent was removed, and the rate performance was significantly lower than that in Comparative Example 2.

Compared with Example 1, the amount of BHT used in Examples 2 and 3 is larger, which blocks the transmission of lithium ions, and the rate performance is reduced to a certain extent; the amount of BHT used in Examples 4 and 7 is small, which cannot provide sufficient antioxidant. effect, so the cycle performance is reduced; Examples 5 and 6 show that the Dv50 particle size will also have a certain impact on battery performance, and the appropriate particle size can further balance the various properties of the battery; in Examples 8 and 9, polypyrrole It is too much, accounting for the proportion of active materials, and the gram capacity is reduced, and it blocks the transmission of lithium ions, and the rate performance is reduced; in Example 10, there is too little polypyrrole, the rate performance is reduced, and BHT cannot be fixed on the primary particles, and the cycle The performance has also declined; in Example 11, carbon nanotubes are used instead of polypyrrole. Although carbon nanotubes are also linear, their flexibility is worse than polypyrrole, so the coating ability is not as good as polypyrrole, resulting in the surface of the primary particles The antioxidant is unevenly distributed and the cycle performance is reduced; in Example 12, carbon black is used instead of polypyrrole. Since the carbon black is not linear, the performance is further reduced compared to the carbon nanotube-coated Example 11; Implementation In Example 13, there is no polypyrrole conductive agent, and BHT cannot effectively adhere to the surface of the primary particles during the cycle, and the rate performance and cycle performance are further reduced; in Examples 14 and 15, there is more CMC-Li, accounting for the proportion of active materials, grams The capacity is reduced, and the package is too thick to block lithium ion transmission, and the rate performance is reduced; in Example 16, there is less CMC-Li, resulting in a slight decrease in the rate performance; the temperature is too low in Example 17 and the material is discharged in Example 20 If the speed is too fast, the secondary particles will bond into large particles, causing the rate performance to decrease; in Example 18, the temperature is too high, which destroys the structure of the antioxidant to a certain extent, resulting in a decrease in cycle performance; in Example 19, the discharging speed is too low , the secondary particles are small, the retained active area is large, and the cycle performance is reduced. Examples 21 and 22 show that the technical solution of the present application can also be applied to high-nickel cathode materials.

The technical features of the above-described embodiments can be combined in any way. To simplify the description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, All should be considered to be within the scope of this manual.

The above-described embodiments only express several implementation modes of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

A positive electrode material, including positive electrode material particles and a coating layer located on the surface of the positive electrode material particles. The material of the coating layer includes antioxidants. The antioxidants include hindered phenolic antioxidants and amine antioxidants. of one or more.
The cathode material according to claim 1, wherein the hindered phenolic antioxidant includes 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-amino One or more of phenol, 2,6-di-tert-butyl-4-(dimethylaminomethyl)phenol, tert-butylhydroquinone and 2,5-di-tert-butylhydroquinone.
The cathode material according to any one of claims 1 to 2, characterized in that the amine antioxidant includes N,N'-di-sec-butyl-p-phenylenediamine, (3,5-di-tert-butyl- 4-Hydroxybenzyl)aniline, 2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis( 1-Octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, stearic acid (2,2,6,6-tetramethyl-4-piperidinol ) ester and one or more of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-benzenedicarboxamide.
The cathode material according to any one of claims 1 to 3, wherein the mass percentage of the antioxidant in the cathode material is 0.1% to 3%.
The cathode material according to any one of claims 1 to 4, wherein the coating layer further includes a conductive agent;

Optionally, the conductive agent includes one or more of polypyrrole conductive agents, polyaniline conductive agents, and functional conductive carbon;

Further optionally, the functional conductive carbon includes one or more of carbon nanotubes, carbon black and graphite, and the surface of the functional conductive carbon is grafted with one or more of carboxyl, hydroxyl and amino groups.
The cathode material according to claim 5, wherein the mass percentage of the conductive agent in the cathode material is 0.5% to 10%.
The cathode material according to any one of claims 1 to 6, characterized in that the cathode material is primary particles, and the Dv50 particle size range of the cathode material is 100 nm to 1 μm.
The cathode material according to any one of claims 1 to 7, wherein the coating layer has a thickness of 2 nm to 100 nm; optionally, the coating layer has a thickness of 2 nm to 60 nm.
The cathode material according to any one of claims 1 to 8, characterized in that the cathode material particles include LiCoO 2 , LiNia Co b Mn (1-ab) O 2 , LiNic Co d Al (1-cd ) O 2 , one or more of eLi 2 MnO 3 ·(1-e)LiMO 2 ;

Among them, a~e are independently selected from 0~1;

M includes one or more of Ni, Co and Mn.
A preparation method of cathode material, including the following steps:

Raw materials related to the cathode material according to any one of claims 1 to 9 are prepared, and each raw material is ball milled.
The preparation method according to claim 10, characterized in that the ball milling meets one or more of the following conditions (1) to (7):

(1) The ball milling medium includes one or more of zirconium balls, stainless steel balls and polyurethane balls;

(2) The diameter of the ball milling medium is 5mm ~ 20mm;

(3) The ball milling medium includes large balls and small balls, the diameter of the large ball is 10mm~20mm, and the diameter of the small ball is 5mm~10mm; optionally, the mass percentage of the small ball in the ball milling medium The content is 10% to 30%, and the mass percentage of the large balls in the ball milling medium is 70% to 90%;

(4) The mass ratio of raw materials to ball milling media is (10~20):1;

(5) The ball mill is a wet ball mill, and the solvent used includes one of chloroform, acetone, toluene and benzene; optionally, the mass ratio of the raw material to the solvent is 1: (1-10);

(6) The rotation speed of the ball mill is 400rpm~600rpm;

(7) The ball milling time is 0.5h~2h.
A positive electrode composite material, including the positive electrode material according to any one of claims 1 to 9 and a lithium-containing binder;

Optionally, the lithium-containing binder includes one or more of lithium carboxymethylcellulose, lithium polyacrylate, and lithium alginate.
The positive electrode composite material according to claim 12, wherein the mass percentage of the lithium-containing binder in the positive electrode composite material is 1% to 10%.
The positive electrode composite material according to any one of claims 12 to 13, characterized in that, in the positive electrode composite material, the mass percentage of the positive electrode material is 90% to 99%.
The positive electrode composite material according to any one of claims 12 to 14, characterized in that the positive electrode composite material is secondary particles, and the Dv50 particle size range of the positive electrode composite material is 5 μm to 20 μm.
The preparation method of the positive electrode composite material according to any one of claims 12 to 15, including the following steps:

The positive electrode material, the lithium-containing binder and the solvent are mixed and spray granulated.
The preparation method according to claim 16, characterized in that the temperature of the spray granulation is 120°C to 140°C, and the discharge speed of the spray granulation is 5mL/min to 20mL/min.
A secondary battery, including a positive electrode plate, a negative electrode plate and a separator, the isolation film being disposed between the positive electrode sheet and the negative electrode sheet;

Wherein, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode material according to any one of claims 1 to 9 and the One or more of the cathode composite materials described in any one of claims 12 to 15.
The secondary battery according to claim 18, wherein the positive active material layer further includes an auxiliary antioxidant, and the auxiliary antioxidant includes one or more of phosphite and thioester;

Optionally, the mass percentage of the auxiliary antioxidant in the positive active material layer is 0.01% to 2%.
An electrical device, characterized by including the secondary battery according to any one of claims 18 to 19.