CN115832277A

CN115832277A - Positive electrode slurry, positive electrode piece, battery cell, battery monomer, battery and power utilization device

Info

Publication number: CN115832277A
Application number: CN202210008414.3A
Authority: CN
Inventors: 许云鹏; 吴燕英; 王星会
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-01-05
Filing date: 2022-01-05
Publication date: 2023-03-21

Abstract

The application relates to positive electrode slurry, a positive electrode plate, an electric core, a single battery, a battery and an electric device. In the positive pole slurry, the positive pole active material comprises three nickel cobalt lithium manganate materials with Dv50 of 8-13 microns, 3.5-7 microns and 1-3 microns respectively, the compaction density of the positive pole active material can be improved through grading of the three nickel cobalt lithium manganate materials with different particle sizes, a specific lubricant added in the positive pole slurry can ensure higher compaction density and simultaneously ensure the integrity of particles of the positive pole active material, and the prepared positive pole piece is not easy to crack and fall off powder and has better electrochemical performance.

Description

Positive electrode slurry, positive electrode piece, battery cell, battery monomer, battery and power utilization device

Technical Field

The application relates to the technical field of batteries, in particular to positive electrode slurry, a positive electrode plate, an electric core, a single battery, a battery and an electric device.

Background

The lithium ion battery has the outstanding advantages of high energy density, excellent cycle life, high working voltage, lower self-discharge rate, environmental friendliness and the like, and becomes an ideal power supply in the fields of electric automobiles and energy storage. With the rapid development of the electric automobile and the energy storage field, the market puts higher requirements on the energy density of the lithium ion battery. Among them, nickel cobalt lithium manganate (NCM) has attracted much attention as a positive electrode active material due to its higher energy density.

The positive active material in the positive pole piece is an important component playing a role in lithium ion intercalation and deintercalation in the lithium ion battery, so the compaction density of the positive pole piece is closely related to the energy density of the lithium ion battery. However, the high compaction density that is sought after in a single step often has a negative effect on the electrochemical properties of the positive electrode active material.

Disclosure of Invention

In view of the above-mentioned needs, the present application provides a positive electrode slurry with a higher compacted density and better electrochemical performance, which can improve the energy density of a battery.

In addition, the positive pole piece, the battery core, the single battery, the battery and the electric device which adopt the positive pole slurry are also provided.

In one aspect, the present application provides a positive electrode slurry, including: a positive electrode active material and a lubricant;

the positive active material comprises a first nickel cobalt lithium manganate material, a second nickel cobalt lithium manganate material and a third nickel cobalt lithium manganate material;

the general formula of the positive electrode active material is formula I:

LiNi _x Co _y Mn _1-x-y O ₂ formula I;

wherein x is more than 0 and less than 1, and y is more than 0 and less than 1;

the Dv50 of the first nickel cobalt lithium manganate material is 8-13 μm; the Dv50 of the second nickel cobalt lithium manganate material is 3.5-7 μm; the Dv50 of the third nickel cobalt lithium manganate material is 1-3 μm; the lubricant is selected from at least one of tributyl citrate, stearic acid and acetyl triethyl citrate;

optionally, dv50 of the first lithium nickel cobalt manganese oxide material is 9 μm to 12 μm;

and/or the Dv50 of the second nickel cobalt lithium manganate material is 4-6 μm;

and/or the Dv50 of the third nickel cobalt lithium manganate material is 2-2.5 μm;

and/or the lubricant is tributyl citrate.

In the positive electrode slurry in the embodiment of the application, the positive electrode active material comprises three nickel cobalt lithium manganate materials with Dv50 of 8-13 μm, 3.5-7 μm and 1-3 μm respectively. The grading of the three nickel cobalt lithium manganate materials with different particle sizes can improve the compaction density of the positive active material, the specific lubricant added into the positive slurry can ensure the integrity of the particles of the positive active material while ensuring higher compaction density, and the prepared positive pole piece is not easy to crack and fall powder and has better electrochemical performance. The positive electrode slurry is used for preparing the positive electrode plate and the electrochemical device, and can improve the energy density of the electrochemical device.

In some embodiments, the molar ratio of nickel to cobalt to manganese in the first lithium nickel cobalt manganese oxide material, the second lithium nickel cobalt manganese oxide material and the third lithium nickel cobalt manganese oxide material is the same. The nickel cobalt lithium manganate material with the same element molar ratio is selected, so that more negative effects on the electrochemical performance of the positive pole piece due to respective defects of the positive pole active material when the positive pole active materials with different compositions are adopted can be avoided.

In some embodiments, the first lithium nickel cobalt manganate material is a secondary particle;

and/or the second lithium nickel cobalt manganese oxide material is of a single crystal structure;

and/or the third nickel cobalt lithium manganate material is of a single crystal structure.

In some embodiments, the mass ratio of the first lithium nickel cobalt manganese oxide material, the second lithium nickel cobalt manganese oxide material and the third lithium nickel cobalt manganese oxide material is (6-7.5): (0.5-3.5): (0.5-3.5);

optionally, the mass ratio of the first nickel cobalt lithium manganate material to the second nickel cobalt lithium manganate material to the third nickel cobalt lithium manganate material is (6.5-7): (1-2): (1-2). The grading of the nickel cobalt lithium manganate material is closely related to the compaction density of the positive active material. Within the mass ratio range, three nickel cobalt lithium manganate materials with different particle sizes are graded, and the positive active material has higher compaction density.

In some embodiments, the mass percentage of the positive active material is 93% to 98%;

and/or the mass percent of the lubricant is 0.1-1.5%.

In a second aspect, the present application further provides a positive electrode plate, including 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 comprises the positive electrode slurry in the embodiment.

In some embodiments, the coating weight of the positive electrode slurry is 300mg/1540.25mm ² ～450mg/1540.25mm ² ；

And/or the thickness of the positive electrode film layer is 130-210 μm.

In a third aspect, the present application further provides an electrical core, where the electrical core includes a positive electrode plate, a negative electrode plate, and an isolation film in the above embodiment, the positive electrode plate and the negative electrode plate are disposed opposite to each other, and the isolation film is located between the positive electrode plate and the negative electrode plate.

In a fourth aspect, the present application further provides a battery cell, including at least one battery cell in the above embodiments.

In a fifth aspect, the present application further provides a battery comprising: the battery cell in the above embodiment.

In a sixth aspect, the present application further provides an electric device, including the battery in the above embodiments.

The foregoing description is only an overview of the technical solutions of the present application, and the present application can be implemented according to the content of the description in order to make the technical means of the present application more clearly understood, and the following detailed description of the present application is given in order to make the above and other objects, features, and advantages of the present application more clearly understandable.

Drawings

Various additional advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Moreover, like reference numerals are used to refer to like elements throughout. In the drawings:

FIG. 1 is a SEM photograph of a first Ni-Co-Mn acid lithium material according to an embodiment of the present application;

FIG. 2 is a SEM photograph of a second Ni-Co lithium manganate material according to an embodiment of the present application;

FIG. 3 is a SEM photograph of a third Ni-Co lithium manganate material according to one embodiment of this application;

fig. 4 is an exploded view of a battery cell according to an embodiment of the present disclosure;

fig. 5 is an exploded view of a battery according to an embodiment of the present disclosure;

FIG. 6 is a schematic structural diagram of a vehicle according to an embodiment of the present application;

FIG. 7 is a scanning electron micrograph of a positive electrode sheet prepared in comparative example 1 of the present application;

FIG. 8 is a SEM photograph of the positive electrode plate prepared in example 2 of the present application;

fig. 9 is a direct current resistance at different SOCs of the lithium ion secondary batteries manufactured in example 2 of the present application and comparative example 2;

fig. 10 is a graph showing charging performance at different rates of the lithium ion secondary batteries manufactured in example 2 of the present application and comparative example 2;

fig. 11 is a graph showing capacity retention rates at different temperatures of the lithium ion secondary batteries prepared in example 2 of the present application and comparative example 2;

fig. 12 shows the discharge capacity retention rate at 500 cycles of the lithium ion secondary batteries prepared in example 2 of the present application and comparative example 2.

The reference numbers in the detailed description are as follows:

10. a battery cell; 11. an end cap; 12. a housing; 13. an electric core; 11a, electrode terminals; 100. a battery; 20. a box body; 201. a first portion; 202. a second portion; 1000. a vehicle; 200. a controller; 300. a motor.

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.

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.

The application of power batteries is becoming more extensive. The power battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles and the like, and a plurality of fields such as military equipment and aerospace. With the continuous expansion of the application field of the power battery, the market demand of the power battery is also continuously expanded, and higher requirements are put on the energy density of the battery.

The present inventors have noted that the compaction density of the positive electrode active material is closely related to the energy density of the battery. However, the attainment of a high compaction density generally also has a negative effect on the electrochemical properties of the positive electrode active material.

In view of the above, in order to improve the energy density of a battery, an embodiment of the present application provides a positive electrode paste including: a positive electrode active material and a lubricant.

The positive active material comprises a first nickel cobalt lithium manganate material, a second nickel cobalt lithium manganate material and a third nickel cobalt lithium manganate material. The general formula of the positive electrode active material is formula I:

LiNi _x Co _y Mn _1-x-y O ₂ formula I;

wherein x is more than 0 and less than 1, and y is more than 0 and less than 1.

The Dv50 of the first nickel cobalt lithium manganate material is 8-13 μm. The Dv50 of the second nickel cobalt lithium manganate material is 3.5-7 μm. The Dv50 of the third nickel cobalt lithium manganate material is 1-3 μm. It should be noted that Dv50 refers to the particle size corresponding to 50% of the volume distribution.

Furthermore, the Dv50 of the first nickel cobalt lithium manganate material is 9-12 μm. The Dv50 of the second nickel cobalt lithium manganate material is 4-6 μm. The Dv50 of the third nickel cobalt lithium manganate material is 2-2.5 μm.

Preferably, the Dv50 of the first lithium nickel cobalt manganate material is 10 μm. The Dv50 of the second lithium nickel cobalt manganate material was 4 μm. The Dv50 of the third lithium nickel cobalt manganate material was 2.5 μm. Through research, the three nickel cobalt lithium manganate materials with different median particle sizes are utilized to carry out grading, so that the compaction density of the positive active material can be obviously improved.

Wherein the lubricant is at least one selected from tributyl citrate, stearic acid and acetyl triethyl citrate. Further, the lubricant is tributyl citrate. Researches find that the tributyl citrate used as a lubricant in the anode slurry can effectively improve the flexibility of the anode piece, and the anode slurry is not easy to crack and fall off powder on the anode piece coated with the anode slurry.

Lithium nickel cobalt manganese oxide material (LiNi) _x Co _y Mn _1-x-y O ₂ Abbreviated as NCM) is a commonly used positive electrode material in lithium ion batteries, and has a high energy density. In the positive electrode slurry, the positive electrode active material comprises three nickel cobalt lithium manganate materials with Dv50 of 8-13 μm, 3.5-7 μm and 1-3 μm respectively. The grading of the nickel cobalt lithium manganate material with different particle sizes can improve the compaction density of the positive active material, the specific lubricant added into the positive slurry can ensure higher compaction density and the integrity of the particles of the positive active material, and the prepared positive pole piece is not easy to crack and fall powder, has better electrochemistry propertyCan be used.

In addition, the positive electrode slurry does not cause obvious negative effects on other electrochemical properties of the secondary battery under the condition of improving the compacted density of the pole piece and the discharge capacity of the secondary battery.

In some embodiments, the first, second, and third lithium nickel cobalt manganese oxide materials are each independently selected from LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (may be abbreviated as NCM 333) and LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (may also be abbreviated as NCM 523) and 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).

In some embodiments, the molar ratios of nickel, cobalt, and manganese in the first, second, and third nickel cobalt lithium manganate materials are the same. The nickel cobalt lithium manganate material with the same element composition is selected, so that more negative effects on the electrochemical performance of the positive pole piece due to respective defects of the positive pole active material can be avoided when the positive pole active material with different compositions is adopted.

In some embodiments, the lithium nickel cobalt manganese oxide material is prepared by a coprecipitation method, and the preparation process comprises the following steps:

(1) And (3) carrying out coprecipitation reaction according to the molar ratio of nickel, cobalt and manganese elements in the nickel-cobalt lithium manganate material to prepare ternary precursors with different particle sizes.

(2) And (2) mixing the ternary precursor prepared in the step (1) with a lithium source, carrying out ball milling, and then sintering to obtain the nickel cobalt lithium manganate material.

Wherein the lithium source is at least one selected from lithium carbonate, lithium hydroxide and lithium nitrate.

Specifically, in the step (1), the raw materials of nickel, cobalt and manganese are soluble salts, and are dissolved in water. And (2) adding a precipitator into the step (1). The precipitant is at least one selected from sodium hydroxide, potassium hydroxide, ammonium bicarbonate and sodium carbonate.

In some embodiments, the first lithium nickel cobalt manganese oxide material is a secondary particle. The second nickel cobalt lithium manganate material is of a single crystal structure. The third nickel cobalt lithium manganate material is of a single crystal structure.

Referring to fig. 1 to fig. 3, fig. 1 is a scanning electron microscope photograph of a first lithium nickel cobalt manganese oxide material according to an embodiment of the present application; FIG. 2 is a SEM photograph of a second Ni-Co lithium manganate material according to an embodiment of the present application; fig. 3 is a scanning electron microscope photograph of a third nickel cobalt lithium manganate material according to an embodiment of the present application. As can be seen from fig. 1 to fig. 3, the first lithium nickel cobalt manganese oxide material is a secondary particle, and the second lithium nickel cobalt manganese oxide material and the third lithium nickel cobalt manganese oxide material are respectively of a single crystal structure.

The grading of the first nickel cobalt lithium manganate material, the second nickel cobalt lithium manganate material and the third nickel cobalt lithium manganate material is closely related to the compaction density of the positive electrode active material. In some embodiments, the mass ratio of the first lithium nickel cobalt manganese oxide material to the second lithium nickel cobalt manganese oxide material to the third lithium nickel cobalt manganese oxide material is (6-7.5): (0.5-3.5): (0.5-3.5). Preferably, the mass ratio of the first nickel cobalt lithium manganate material to the second nickel cobalt lithium manganate material to the third nickel cobalt lithium manganate material is (6.5-7): (1-2): (1-2). Within the mass ratio range, three nickel cobalt lithium manganate materials with different particle sizes are graded, and the positive active material has higher compaction density.

In some embodiments, the positive electrode paste further includes a conductive agent and a binder.

The conductive agent can improve the conductivity of the active layer and improve the charge-discharge performance of the positive pole piece. In some embodiments, the conductive agent may be selected from, but is not limited to, at least one of superconducting carbon, conductive graphite, acetylene black, carbon nanotubes, carbon black, graphene.

The binder in the positive electrode slurry is generally a hydrophobic binder so as to be dispersed in a hydrophobic organic solvent. In some embodiments, the binder may be selected from, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers, tetrafluoroethylene-hexafluoropropylene copolymers, and fluoroacrylate resins.

In some embodiments, the positive electrode slurry further comprises: a solvent. Generally, the solvent in the positive electrode slurry is selected from hydrophobic organic solvents.

In some embodiments, the mass percentage of the positive electrode active material is 93% to 98% relative to the total mass of the positive electrode slurry; and/or the mass percent of the conductive agent is 0.1-5%; and/or the mass percent of the lubricant is 0.1-1.5%; and/or the mass percent of the binder is 0.1-2%.

In some embodiments, the positive electrode active material is 93 to 98% by mass, the conductive agent is 0.1 to 5% by mass, the lubricant is 0.1 to 1.5% by mass, and the binder is 0.1 to 2% by mass, relative to the total mass of the positive electrode slurry.

In some embodiments, the positive electrode slurry further includes an auxiliary agent such as a dispersant.

In some embodiments, the positive electrode slurry may be prepared by: the components of the positive electrode slurry, such as the positive electrode active material, the conductive agent, the lubricant, the binder, and other components of the above-described examples, are dispersed with a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry.

In another embodiment of the present application, a positive electrode plate is further provided, which 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 the positive electrode slurry in the above embodiment.

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 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 (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 sheet can be prepared by: and coating the positive electrode slurry on the surface of the positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.

In some embodiments, the coating weight of the positive electrode slurry is 300mg/1540.25mm ² ～450mg/1540.25mm ² . By controlling the coating weight of the positive electrode slurry within the above range, a positive electrode sheet with appropriate compaction density and good electrochemical performance can be obtained.

In some embodiments, the thickness of the positive electrode film layer is 130 μm to 210 μm. The positive pole piece with the thickness of the positive pole film layer within the range has good electrochemical performance and flexibility.

This application another embodiment still provides an electricity core, includes: the positive pole piece, the negative pole piece and the isolating film in the embodiment are adopted; the positive pole piece and the negative pole piece are arranged oppositely, and the isolating film is positioned between the positive pole piece and the negative pole piece.

The negative pole piece includes the negative current collector and sets up the negative pole rete on the negative current collector at least one surface, and the negative pole rete includes negative 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 may be selected from at least one of elemental silicon, silicon oxy-compounds, silicon-carbon compounds, silicon-nitrogen compounds, 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 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. As an example, the binder may be selected from at least one of Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

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 components for preparing the negative electrode plate, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (such as deionized water) to form 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.

The isolating film is mainly used for isolating the positive plate from the negative plate, preventing the short circuit of the negative and positive electrodes in the battery, enabling ions to pass through and having the function of keeping electrolyte. 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 fabricated into a cell by a winding process or a lamination process.

In another embodiment of the present application, there is also provided a battery cell including: the battery cell in at least one of the above embodiments. The single battery in the technical scheme of the embodiment includes at least one battery cell in the above embodiments, and the single battery has a higher energy density, and can meet higher use requirements.

Referring to fig. 4, fig. 4 is an exploded schematic view of a battery cell 10 according to some embodiments of the present disclosure. The battery cell 10 refers to the smallest unit constituting the battery 100. As shown in fig. 4, the battery cell 10 includes an end cap 11, a housing 12, and a battery core 13.

The end cap 11 refers to a member that covers an opening of the case 12 to insulate the internal environment of the battery cell 10 from the external environment. Without limitation, the shape of the end cap 11 may be adapted to the shape of the housing 12 to fit the housing 12. Alternatively, the end cap 11 may be made of a material (e.g., an aluminum alloy) having certain hardness and strength, so that the end cap 11 is not easily deformed when being extruded and collided, and the single battery 10 may have higher structural strength and improved safety performance. The end cap 11 may be provided with functional components such as the electrode terminal 11 a. The electrode terminal 11a may be used to electrically connect with the battery cell 13, so as to output or input electric energy of the battery cell 10. In some embodiments, the end cap 11 may further be provided with a pressure relief mechanism for relieving the internal pressure when the internal pressure or temperature of the battery cell 10 reaches a threshold value. The material of the end cap 11 may also be various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which is not limited in this embodiment. In some embodiments, insulation may also be provided on the inside of the end cap 11, which may be used to isolate the electrical connection components within the housing 12 from the end cap 11 to reduce the risk of short circuits. Illustratively, the insulator may be plastic, rubber, or the like.

The housing 12 is an assembly for engaging the end cap 11 to form an internal environment of the battery cell 10, wherein the formed internal environment can be used for accommodating the battery cell 13, an electrolyte (not shown in the figures), and other components. The housing 12 and the end cap 11 may be separate components, and an opening may be formed in the housing 12, and the opening may be covered by the end cap 11 to form the internal environment of the battery cell 10. Without limitation, the end cap 11 and the housing 12 may be integrated, and specifically, the end cap 11 and the housing 12 may form a common connecting surface before other components are inserted into the housing, and when it is necessary to enclose the inside of the housing 12, the end cap 11 covers the housing 12. The housing 12 may be of various shapes and sizes, such as rectangular parallelepiped, cylindrical, hexagonal prism, etc. Specifically, the shape of the casing 12 may be determined according to the specific shape and size of the battery cell 13. The material of the housing 12 may be various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present invention is not limited thereto.

The electrolyte includes an electrolyte salt and a solvent. In some embodiments, the electrolyte salt can 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 difluorooxalato 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, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive.

In another embodiment of the present application, there is also provided a battery 100 including: the battery cell 10 in the above embodiment.

Referring to fig. 5, fig. 5 is an exploded view of a battery 100 according to some embodiments of the present disclosure. The battery 100 includes a case 20 and a battery cell 10, and the battery cell 10 is accommodated in the case 20. The case 20 is used to provide a receiving space for the battery cell 10, and the case 20 may have various structures. In some embodiments, the case 20 may include a first portion 201 and a second portion 202, the first portion 201 and the second portion 202 cover each other, and the first portion 201 and the second portion 202 together define a receiving space for receiving the battery cell 10. The second part 202 may be a hollow structure with an open end, the first part 201 may be a plate-shaped structure, and the first part 201 covers the open side of the second part 202, so that the first part 201 and the second part 202 together define a receiving space; the first portion 201 and the second portion 202 may be both hollow structures with one side open, and the open side of the first portion 201 covers the open side of the second portion 202. Of course, the box 20 formed by the first portion 201 and the second portion 202 may have various shapes, such as a cylinder, a rectangular parallelepiped, and the like.

In the battery 100, the number of the battery cells 10 may be multiple, and the multiple battery cells 10 may be connected in series or in parallel or in series-parallel, where in series-parallel refers to that the multiple battery cells 10 are connected in series or in parallel. The plurality of single batteries 10 can be directly connected in series or in parallel or in series-parallel, and the whole formed by the plurality of single batteries 10 is accommodated in the box body 20; of course, the battery 100 may also be formed by connecting a plurality of battery cells 10 in series, in parallel, or in series-parallel to form a battery 100 module, and then connecting a plurality of battery 100 modules in series, in parallel, or in series-parallel to form a whole, and accommodating the whole in the case 20. The battery 100 may further include other structures, for example, the battery 100 may further include a bus member for achieving electrical connection between the plurality of battery cells 10.

In another embodiment of the present application, an electric device is also provided, which includes the battery 100 in the above embodiment. The powered device may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle 1000 (e.g., 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, etc.), an electric train, a ship, and a satellite, an energy storage system, etc., but is not limited thereto.

Referring to fig. 6, fig. 6 is a schematic structural diagram of a vehicle 1000 according to some embodiments of the present disclosure. The vehicle 1000 may be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile may be a pure electric automobile, a hybrid electric automobile, or an extended range automobile, etc. The battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom or the head or the tail of the vehicle 1000. The battery 100 may be used for power supply of the vehicle 1000, and for example, the battery 100 may serve as an operation power source of the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300, the controller 200 being configured to control the battery 100 to supply power to the motor 300, for example, for starting, navigation, and operational power requirements while the vehicle 1000 is traveling.

In some embodiments of the present application, the battery 100 may be used not only as an operating power source of the vehicle 1000, but also as a driving power source of the vehicle 1000, instead of or in part of fuel or natural gas, to provide driving power for the vehicle 1000.

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

The present application is further illustrated by the following specific examples.

Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples do not specify particular techniques or conditions, and are performed according to techniques or conditions described in literature in the art or according to the product specification. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Positive electrode active material:

in the embodiment, a first nickel cobalt lithium manganate material (A),The chemical compositions of the second nickel cobalt lithium manganate material (B) and the third nickel cobalt lithium manganate material (C) are LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM 811). Mixing a first nickel cobalt lithium manganate material (A), a second nickel cobalt lithium manganate material (B) and a third nickel cobalt lithium manganate material (C) with different Dv50 according to a certain mass ratio to obtain the positive active material.

Preparing a positive pole piece:

mixing the positive electrode active material with a conductive agent carbon black, a binder polyvinylidene fluoride (PVDF) and a lubricant according to a certain mass ratio, adding a solvent N-methyl pyrrolidone, and uniformly mixing and stirring to obtain positive electrode slurry. And uniformly coating the positive electrode slurry on the surface of the positive electrode current collector aluminum foil, drying at 85 ℃, and then carrying out cold pressing, slitting and cutting to obtain the positive electrode piece.

Specifically, in examples 1 to 5, 8 to 10 and comparative example 1, the mass ratio of the positive electrode active material, the conductive agent, the binder, and the lubricant was 96.7.

In example 6, the mass ratio of the positive electrode active material, the conductive agent, the binder, and the lubricant was 96.

In example 7, the mass ratio of the positive electrode active material, the conductive agent, the binder, and the lubricant was 96.9.

In comparative examples 2 and 3, the mass ratio of the positive electrode active material, the conductive agent, and the binder was 97.

Preparing a negative pole piece:

preparing a negative active material artificial graphite, a conductive agent carbon black Super P and a binder Styrene Butadiene Rubber (SBR) according to a mass ratio of 92:3: and 5, mixing, adding N-methyl pyrrolidone serving as a solvent, and stirring and uniformly mixing to obtain the cathode slurry. And uniformly coating the negative electrode slurry on the surface of a negative electrode current collector, drying at 80-90 ℃ after coating, and carrying out cold pressing, slitting and cutting to obtain the negative electrode piece.

Preparing an electrolyte:

preparing a basic electrolyte, wherein the basic electrolyte comprises dimethyl carbonate (DMC), ethyl Methyl Carbonate (EMC) and Ethylene Carbonate (EC), and the mass ratio of the dimethyl carbonate to the ethyl methyl carbonate to the ethylene carbonate is 2. Then, an electrolyte salt was added so that the concentration of lithium hexafluorophosphate in the electrolyte solution was 1mol/L.

Preparing a lithium ion secondary battery:

the positive electrode sheet, the negative electrode sheet and the separator were wound into a cell, and an electrolyte was injected into the cell, followed by packaging, molding, formation and the like to prepare the lithium ion secondary batteries of examples 1 to 11 and comparative example 1.

The compositions of the lithium ion secondary batteries of examples 1 to 11 and comparative examples 1 to 2 are shown in table 1.

TABLE 1

And (3) performance testing:

determination of compacted density:

when the lithium ion secondary battery is manufactured, cold pressing is carried out for 1 time under the same coating weight and the same rolling parameters, and the compacted density of the positive active material is calculated by measuring the thickness of the positive pole piece after the cold pressing. In the present embodiment, the coating weight is 300mg/1540.25mm ² 。

Flexibility test:

and folding the prepared positive pole piece for multiple times until the surface of the positive pole piece is cracked. The flexibility of the positive pole piece is represented by the number of folding times when cracks are generated, namely, the less the number of folding times is, the poorer the flexibility of the positive pole piece is; the more the folding times, the better the flexibility of the positive pole piece. In the embodiment of the application, the number of folding times of the positive pole piece is not more than 3, and the positive pole piece does not meet the use requirement.

And (3) energy density testing:

charging to 4.2V at 0.33C standard at normal temperature, charging to 0.05C at 4.2V constant voltage, standing for 10min, discharging to 2.8V at 0.33C, recording the discharge capacity, and calculating the energy density at discharge.

Energy density (Wh/L) = discharge capacity (Wh)/volume of lithium ion secondary battery (L)

See table 2 for the compaction density, pole piece flexibility and energy density of the samples of examples 1-11 and comparative example 1.

TABLE 2

As can be seen from the data in Table 2, the positive electrode slurries of examples 1 to 10 are graded by three NCM811 material grades with different median particle diameters, and the compacted density of the positive electrode active material of the secondary grade in comparative examples 1 to 2 is improved from 3.55mg/cm ³ Lifting to 3.6mg/cm ³ ～3.65mg/cm ³ And the energy density of the lithium ion secondary battery is improved by about 1 to 2 percent. Among them, the positive electrode sheet and the lithium ion secondary battery prepared in example 2 were the best in performance. Compared with comparative examples 1 to 3, the flexibility of the positive pole piece prepared in examples 1 to 10 is remarkably improved, and the positive pole piece is not easy to crack or fall off after being bent. In examples 1 to 8, the flexibility of the positive electrode plate using the tributyl citrate lubricant is improved more significantly. The amount of lubricant tributyl citrate in the positive electrode sheet of example 7 was small, the flexibility of the prepared positive electrode sheet was slightly poor, and cracks began to occur after folding 4 times. In examples 9 and 10, acetyl triethyl citrate and stearic acid were used as lubricants, and the flexibility of the positive electrode sheet was slightly inferior to those in examples 1 to 6 and 8.

Referring to fig. 7 and 8, fig. 7 is a scanning electron microscope photograph of the positive electrode plate prepared in comparative example 1 of the present application; fig. 8 is a scanning electron micrograph of the positive electrode sheet prepared in example 2 of the present application. As can be seen from fig. 7 and 8, compared to the positive electrode sheet of comparative example 1, the positive electrode active material on the positive electrode sheet prepared in example 2 is more dense and has a higher compacted density, and the particles of the positive electrode active material are complete and are not significantly broken.

In addition, in order to further study the electrochemical properties of the cathode active material of the present application, the electrochemical properties of the lithium ion secondary batteries prepared in example 2 and comparative example 2, such as direct current resistance, rate capability, high and low temperature performance, and cycle stability, were also tested.

Referring to fig. 9 to 12, fig. 9 shows the dc resistances of the lithium ion secondary batteries prepared in example 2 of the present application and comparative example 2 at different SOCs, and it can be seen that in the lithium ion secondary battery of example 2, 0.3% wt of tributyl citrate, a lubricant, was added to the positive electrode slurry, and the resistance deterioration of the battery was 1.5% or less, which had no significant effect on the battery resistance. Fig. 10 shows the charging performance of the lithium ion secondary batteries prepared in example 2 and comparative example 2 of the present application at different rates, and it can be seen that there is no significant difference in the charging performance of the lithium ion secondary batteries prepared in example 2 and comparative example 2. Fig. 11 shows capacity retention rates of the lithium ion secondary batteries prepared in example 2 and comparative example 2 of the present application at different temperatures, and it can be seen that there is no significant difference in the high and low temperature capacity retention rates of the lithium ion secondary batteries prepared in example 2 and comparative example 2. Fig. 12 shows the discharge capacity retention rates of the lithium ion secondary batteries prepared in example 2 and comparative example 2 of the present application at 500 cycles, and it can be seen that the capacity retention rates of the lithium ion secondary batteries prepared in example 2 and comparative example 2 are close to each other. Therefore, the lithium ion secondary battery prepared in example 2 adopts the nickel cobalt lithium manganate material of tertiary gradation as the positive electrode active material, and tributyl citrate is also added to the positive electrode slurry as the lubricant, compared with the lithium ion secondary battery composed of the conventional secondary gradation positive electrode material prepared in comparative example 2, the lithium ion secondary battery has the same level of performance in terms of discharge rate, high and low temperature performance and cycle performance, and the DCR weakening caused by adding the lubricant is within 1.5%.

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 embodiments of the present application, so as to facilitate the specific and detailed understanding of the technical solutions of the present application, but the present invention should not be construed as being limited to the scope of the invention. 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. It should be understood that the technical solutions provided by the present application and obtained by logical analysis, reasoning or limited experiments by those skilled in the art are all within the scope of the appended claims. Therefore, the protection scope of the present patent application shall be subject to the content of the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A positive electrode slurry, characterized by comprising: a positive electrode active material and a lubricant;

the general formula of the positive electrode active material is formula I:

LiNi _x Co _y Mn _1-x-y O ₂ formula I;

wherein x is more than 0 and less than 1, and y is more than 0 and less than 1;

and/or the Dv50 of the third nickel cobalt lithium manganate material is 2 μm to 2.5 μm;

and/or the lubricant is tributyl citrate.

2. The positive electrode slurry of claim 1, wherein the molar ratio of nickel to cobalt to manganese in the first, second and third nickel cobalt lithium manganate materials is the same.

3. The positive electrode slurry according to claim 1, wherein the first lithium nickel cobalt manganese oxide material is a secondary particle;

and/or the second nickel cobalt lithium manganate material is of a single crystal structure;

4. The cathode slurry according to any one of claims 1 to 3, wherein the mass ratio of the first lithium nickel cobalt manganese oxide material to the second lithium nickel cobalt manganese oxide material to the third lithium nickel cobalt manganese oxide material is (6-7.5): (0.5-3.5): (0.5 to 3.5);

optionally, the mass ratio of the first nickel cobalt lithium manganate material to the second nickel cobalt lithium manganate material to the third nickel cobalt lithium manganate material is (6.5-7): (1-2): (1-2).

5. The positive electrode slurry according to any one of claims 1 to 3, wherein the mass percentage of the positive electrode active material is 93% to 98% with respect to the total mass of the positive electrode slurry;

and/or the mass percent of the lubricant is 0.1-1.5%.

6. The positive pole piece is characterized by comprising a positive pole current collector and a positive pole film layer arranged on at least one surface of the positive pole current collector;

the raw material for preparing the positive electrode film layer comprises the positive electrode slurry as defined in any one of claims 1 to 5.

7. The positive electrode sheet according to claim 6, wherein the coating weight of the positive electrode slurry is 300mg/1540.25mm ² ～450mg/1540.25mm ² ；

And/or the thickness of the positive electrode film layer is 130-210 μm.

8. An electric core, characterized in that the electric core comprises the positive electrode plate, the negative electrode plate and the separator of claim 6 or 7, wherein the positive electrode plate and the negative electrode plate are disposed opposite to each other, and the separator is located between the positive electrode plate and the negative electrode plate.

9. A battery cell comprising at least one cell according to claim 8.

10. A battery, comprising: the battery cell of claim 9.

11. An electric device comprising the battery of claim 10.