CN116154178B

CN116154178B - Positive electrode plate, battery cell, battery and electricity utilization device

Info

Publication number: CN116154178B
Application number: CN202310437171.XA
Authority: CN
Inventors: 刘醒醒; 杨成龙; 高靖宇; 张海明
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-04-23
Filing date: 2023-04-23
Publication date: 2023-09-01
Anticipated expiration: 2043-04-23
Also published as: CN116154178A

Abstract

The invention relates to the technical field of secondary batteries, in particular to a positive electrode plate, a battery cell, a battery and an electric device. The positive pole piece comprises a current collector and a coating arranged on at least one side of the current collector, wherein the coating comprises a binder, and the binder comprises doped polyaniline. The doped polyaniline has cohesiveness and conductivity, imine nitrogen in the doped polyaniline can be coordinated with F and other anionic groups in the electrolyte, so that acidic substances such as HF and the like are removed from electrolyte decomposition, the migration of the acidic substances to a negative electrode is relieved, the integrity and stability of a negative electrode-electrolyte interface are improved, and the doped polyaniline is introduced into a coating, so that the performance of a secondary battery can be improved.

Description

Positive electrode plate, battery cell, battery and electricity utilization device

Technical Field

The invention relates to the technical field of secondary batteries, in particular to a positive electrode plate, a battery cell, a battery and an electric device.

Background

The secondary battery has been widely used in the fields of pure electric vehicles, hybrid electric vehicles, smart grids, and the like.

The secondary battery has a problem in that the performance of the battery is deteriorated during use.

Disclosure of Invention

The invention mainly aims to provide a positive electrode plate which aims to improve the performance of a battery.

In order to achieve the above purpose, the positive electrode plate provided by the invention comprises a current collector and a coating layer arranged on at least one side of the current collector, wherein the coating layer comprises a binder, and the binder comprises doped polyaniline.

The positive pole piece comprises a current collector and a coating arranged on at least one side of the current collector, wherein the coating comprises a binder, and the binder comprises doped polyaniline. The doped polyaniline has cohesiveness and conductivity, imine nitrogen in the doped polyaniline can be coordinated with F and other anionic groups in the electrolyte, so that acidic substances such as HF and the like are removed from electrolyte decomposition, the migration of the acidic substances to a negative electrode is relieved, the integrity and stability of a negative electrode-electrolyte interface are improved, and the doped polyaniline is introduced into a coating, so that the performance of a secondary battery can be improved.

Alternatively, the volume average particle diameter DV50 of the doped polyaniline has a range of values from 15 μm to 35 μm.

In order to solve the problems of easy agglomeration and difficult dispersion of doped polyaniline in the preparation of coating slurry, and the problems of adhesion of the doped polyaniline to the surface of a positive electrode material and extension of a diffusion path of lithium ions (for example, lithium ion batteries, and other types of secondary batteries), the volume average particle diameter DV50 of the doped polyaniline is selected to have a range of 15-35 mu m.

Alternatively, the volume average particle diameter DV50 of the doped polyaniline has a range of values from 20 μm to 30 μm.

In order to solve the problems of easy agglomeration and difficult dispersion of doped polyaniline in the preparation of coating slurry, and the problems of adhesion of doped polyaniline to the surface of a positive electrode material and extension of a diffusion path of lithium ions (for example, lithium ion batteries, and other types of secondary batteries), the volume average particle diameter DV50 of the doped polyaniline is selected to have a range of values of 20-30 μm.

Optionally, the range of values of the apparent density of the doped polyaniline is 0.2g/cm ³ To 0.6g/cm ³ . The apparent density is related to the particle size and porosity of the material, and is within this range, the doped polyaniline has a suitable size and porosity to facilitate the transport of lithium ions (for example, lithium ion batteries, but may be other types of secondary batteries) in the coating. Based on this, the apparent density of the polyaniline in a doped state was in the range of 0.2g/cm ³ To 0.6g/cm ³ 。

Optionally, the range of values of the apparent density of the doped polyaniline is 0.3g/cm ³ To 0.5g/cm ³ 。

In this range, the doped polyaniline has a suitable size and porosity to facilitate the transport of lithium ions (for example, lithium ion batteries, but other types of secondary batteries) in the coating. Based on this, the apparent density of the polyaniline in a doped state was in the range of 0.3g/cm ³ To 0.5g/cm ³ 。

Optionally, the molecular weight range value of the doped polyaniline is 40000 to 80000.

The molecular weight of the doped polyaniline is in the above range, and the cohesiveness of the doped polyaniline and the wettability of the cathode to the electrolyte can be improved.

Optionally, the molecular weight range of the doped polyaniline is 50000 to 60000.

The doped polyaniline in the application refers to doped polyaniline formed by proton doping of polyaniline. After the polyaniline is doped, the conductivity of the polyaniline is improved.

Optionally, the molar ratio of dopant to aniline in the doped polyaniline ranges from 25% to 45%.

The amount of the dopant in the doped polyaniline can control the conductivity of the doped polyaniline, and in particular, H is generated by decomposing doped protonic acid during the doping process of the polyaniline ⁺ And anions (e.g. Cl) ^- Sulfate, phosphate, etc.) into the backbone, and combine with the N atoms in the amine and imine groups to form polar and bipolar delocalization into P bonds throughout the molecular chain, thereby rendering the polyaniline more conductive. Considering that imine nitrogen in polyaniline can coordinate with F plasma groups in electrolyte, in order to make polyaniline have a certain amount of imine nitrogen to coordinate with F plasma groups in electrolyte, acidic substances such as HF and the like generated by decomposition of lithium salt and electrolyte are removed, migration of the acidic substances to a negative electrode is relieved, integrity and stability of a negative electrode-electrolyte interface are improved, and a range of a molar ratio of a dopant in doped polyaniline to aniline is 25-45%.

Optionally, the molar ratio of dopant to aniline in the doped polyaniline ranges from 32% to 40%.

In order to improve the conductivity of the doped polyaniline, the molar ratio of dopant to aniline in the doped polyaniline ranges from 32% to 40%.

Optionally, the doped polyaniline comprises an organic acid doped polyaniline and/or an inorganic acid doped polyaniline.

The conductivity of the doped polyaniline can be improved by doping polyaniline with organic acid or polyaniline with inorganic acid.

Optionally, the doped polyaniline comprises an inorganic acid doped polyaniline, and the inorganic acid doped polyaniline comprises a hydrochloric acid doped polyaniline.

In view of the relatively high price of organic acids, it is preferable to use inorganic acid doping, and inorganic acid doping polyaniline includes hydrochloric acid doping polyaniline.

Optionally, the thermal decomposition temperature of the doped polyaniline is greater than 350 ℃.

In order to improve the stability of the doped polyaniline, the thermal decomposition temperature of the doped polyaniline is higher than 350 ℃ in consideration of heat generation in the working process of the battery, and the use safety of the battery can be improved by applying the doped polyaniline with high thermal decomposition temperature.

Optionally, the conductivity of the doped polyaniline ranges from 0.2S/cm to 0.6S/cm.

In order to improve the migration of lithium ions (for example, lithium ion batteries, and other types of secondary batteries) in the positive electrode sheet, the conductivity range of the doped polyaniline in the application is 0.2S/cm to 0.6S/cm.

Optionally, the conductivity of the doped polyaniline ranges from 0.3S/cm to 0.5S/cm.

In order to improve the migration of lithium ions (for example, lithium ion batteries, and other types of secondary batteries) in the positive electrode sheet, the conductivity range of the doped polyaniline in the application is 0.3S/cm to 0.5S/cm.

Optionally, the mass of the doped polyaniline accounts for 0% < W0 < 100% of the mass of the binder.

Optionally, the mass of the doped polyaniline accounts for 30-80% of the mass of the binder.

Optionally, the mass of the doped polyaniline accounts for 40-70% of the mass of the binder.

Optionally, the mass of the doped polyaniline accounts for 40-60% of the mass of the binder.

The doped polyaniline has adhesive property and conductive property, and can improve the performance of the battery, and the mass of the doped polyaniline can occupy the mass of the adhesive with the ratio of W0 being more than 0 percent and less than 100 percent. The mass of the doped polyaniline can account for 30 percent to 80 percent of the mass of the binder. The mass of the doped polyaniline can account for 40 percent to 70 percent of the mass of the binder. The mass of the doped polyaniline can occupy 40 percent to 60 percent of the mass of the binder. It is understood that, within a certain range, the battery performance is improved with increasing amounts of doped polyaniline, and the adhesion between the coating and the current collector is reduced with further increasing amounts of doped polyaniline.

Optionally, the doped polyaniline accounts for more than 0% of the coating mass, and less than 10%.

The doped polyaniline is introduced into the coating, so that the performance of the secondary battery can be improved, and the mass of the doped polyaniline accounts for more than 0% and less than 10% of the mass of the coating.

Optionally, the doped polyaniline accounts for 4 to 6 percent of the coating by mass.

The doped polyaniline is introduced into the coating, so that the performance of the secondary battery can be improved, and the mass of the doped polyaniline accounts for 4-6% of the mass of the coating.

Optionally, the coating comprises a positive electrode material comprising a lithium-containing transition metal oxide comprising

Considering the positive pole piece and electrolysisAnd for the nickel cobalt lithium manganate material with more nickel content, the active material crystal lattice is easier to release oxygen, so that the cell is inflated and deformed, and the cycle life is influenced. The high nickel material contains transition metal ions with high oxidability, and the electrolyte is decomposed on the surface of the positive electrode to form a positive electrode-electrolyte interface with complex surface chemistry. The high nickel material is exposed to an open container, O in the crystal lattice ₂ ^- With CO in air ₂ And H ₂ O reacts to generate CO ₃ ^2- Or OH (OH) ^- Producing Li ₂ CO ₃ And LiOH impurities, accelerate the electrolyte decomposition, resulting in a phase change of the positive electrode material from lamellar to spinel.

That is, the above problems are more remarkable in the positive electrode sheet comprising a high nickel material, for which the positive electrode material of the present application comprises a lithium-containing transition metal oxide comprisingFor the positive electrode plate comprising the high-nickel material, the doped polyaniline is used in the positive electrode plate comprising the high-nickel material, so that the doped polyaniline in the adhesive can ensure the basic adhesive performance and improve the performance of the battery. Specifically, the electrochemical performance and the interfacial electrochemical reaction of the positive electrode material are optimized; thereby improving the stability of the anode material and the electrochemical interface and improving the gas production and capacity attenuation of the battery.

Since lithium ions are consumed by the battery through processes such as formation and cycle, the content of lithium element 1+a in the positive electrode material may be less than 1. Meanwhile, if the positive pole piece and the negative pole piece are subjected to lithium supplementing, the situation that the content of lithium element 1+a in the positive pole material is larger than 1 can occur after the battery is subjected to processes such as formation, circulation and the like.

The oxygen element in the positive electrode material is lost due to the battery being subjected to a cycle or the like, and thus the oxygen element content 2-b in the positive electrode material may be measured to be less than 2.

Optionally, the coating includes at least two active layers, the at least two active layers are stacked on the same side of the current collector, at least one active layer is disposed close to the current collector, and at least another active layer is disposed on a side of at least one active layer facing away from the current collector;

and defining that the weight percentage of the doped polyaniline in at least one active layer to the binder is W1, and the weight percentage of the doped polyaniline in at least one other active layer to the binder is W2, wherein W1 is less than W2, and W1 is more than or equal to 0% and less than 100%.

The doped polyaniline has certain bonding capability, but has poor bonding capability compared with the common bonding agent of the secondary battery, and in order to ensure good bonding capability between the coating and the current collector and improve the interface stability of the anode and the electrolyte, the coating at least comprises two active layers, wherein the at least two active layers are arranged on the same side of the current collector layer by layer, at least one active layer is arranged close to the current collector, and at least one other active layer is arranged on the side of the at least one active layer away from the current collector layer; and defining that the mass percentage of the doped polyaniline in at least one active layer to the binder is W1, and the mass percentage of the doped polyaniline in at least one other active layer to the binder is W2, wherein W1 is more than or equal to W2, and W1 is more than or equal to 0% and less than or equal to 100%.

Optionally, 0% or less than or equal to W1% or less than or equal to 50%, and/or 40% or less than or equal to W2% or less than or equal to 60%.

In order to improve the comprehensive performance of the pole piece, the doped polyaniline in at least one active layer accounts for W1 in percentage by mass of the binder, the doped polyaniline in at least one other active layer accounts for W2 in percentage by mass of the binder, and the W1 is more than or equal to 0% and less than or equal to 50%, and/or the W2 is more than or equal to 40% and less than or equal to 60%.

The application also provides a battery cell, which comprises the positive pole piece.

The application also provides a battery, which comprises the battery cell.

The application also provides an electric device which comprises the battery cell or the battery.

The positive electrode plate comprises a current collector and a coating arranged on at least one side of the current collector, wherein the coating comprises a binder, and the binder comprises doped polyaniline. The doped polyaniline has cohesiveness and conductivity, imine nitrogen in the doped polyaniline can be coordinated with F and other anionic groups in the electrolyte, so that acidic substances such as HF and the like are removed from electrolyte decomposition, the migration of the acidic substances to a negative electrode is relieved, the integrity and stability of a negative electrode-electrolyte interface are improved, and the performance of a secondary battery can be improved by introducing the polyaniline into a coating.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic structural view of a positive electrode sheet according to an embodiment of the present application;

fig. 2 is a schematic view of a secondary battery according to an embodiment of the present application;

fig. 3 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 2;

fig. 4 is a schematic view of a battery module according to an embodiment of the present application;

fig. 5 is a schematic view of a battery pack according to an embodiment of the present application;

fig. 6 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 5;

fig. 7 is a schematic view of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

the achievement of the objects, functional features and advantages of the present application will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Hereinafter, embodiments of the positive electrode sheet, the electrode assembly, the battery cell, the battery and the power utilization device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The terms "comprising" and "including" as used herein mean open ended or closed ended, unless otherwise noted. For example, "comprising" and "including" may mean that other components not listed may also be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

In some cases, the decomposition of the active material and the electrolyte results in thickening of the negative electrode SEI film and degradation of the battery capacity. For example, liPF ₆ Acidic substances (e.g., HF) generated by the hydrolysis attack the positive electrode and gradually dissolve the positive electrode active material. Dissolution product migration to the negative side, altering negative surfacingChemical nature, and breaks the integrity of the negative electrode-electrolyte interface (SEI). For example, ni in high nickel material ²⁺ / ⁴⁺ The potential is high, the electrolyte is decomposed on the surface of the positive electrode of the high-nickel material, the high-nickel material is subjected to phase change, and the battery capacity is reduced.

In order to solve the problems, the application provides a positive electrode plate, which comprises a current collector and a coating arranged on at least one side of the current collector, wherein the coating comprises a binder, and the binder comprises doped polyaniline.

The current collector is a structure or a part for collecting current, and the secondary battery mainly comprises a metal foil, such as copper foil and aluminum foil. The current collector is used as a base material for attaching an anode or a cathode active material, and plays a role in collecting current generated by the active material and outputting large current. Generally, aluminum foil is used as a positive current collector, and copper foil is used as a negative current collector.

The adhesive is a material with adhesive property for bonding different substances together.

Polyaniline is a linear high molecular polymer with a long-range conjugated structure and is formed by an oxidized form containing benzene-quinone alternately and a continuous reduced form containing benzene-benzene, and has excellent cohesiveness and electrochemical performance.

The doped polyaniline is polyaniline doped with protons. After the polyaniline is doped, the conductivity of the polyaniline is improved.

The doped polyaniline has cohesiveness and conductivity, imine nitrogen in the doped polyaniline can be coordinated with F and other anionic groups in the electrolyte, so that acidic substances such as HF and the like are removed from electrolyte decomposition, the migration of the acidic substances to the negative electrode is relieved, the problem that the acidic substances (such as HF) attack the positive electrode and gradually dissolve the positive electrode active material is solved, the integrity and stability of a negative electrode-electrolyte interface are improved, and the polyaniline is introduced into a coating, so that the performance of the secondary battery can be improved.

In one embodiment, the volume average particle diameter DV50 of the doped polyaniline ranges from 15 μm to 35 μm.

In one embodiment, the volume average particle diameter DV50 of the doped polyaniline ranges from 20 μm to 30 μm.

DV50, wherein the particle size of 50% of the total volume of particles in the sample particles is larger than the value, and the particle size of 50% of the total volume of particles is smaller than the value; dv50 may represent the median particle diameter of the sample.

Volume average particle diameter DV50 test, equipment model: malvern 2000 (MasterSizer 2000) laser particle sizer, reference standard procedure: GB/T19077-2016/ISO 13320:2009, specific test procedure: taking a proper amount of a sample to be detected (the concentration of the sample is ensured to be 8-12% of the shading degree), adding 20ml of deionized water, simultaneously carrying out ultrasonic treatment for 5min (53 KHz/120W) to ensure that the sample is completely dispersed, and then measuring the sample according to the GB/T19077-2016/ISO 13320:2009 standard.

In order to solve the problems of easy agglomeration and difficult dispersion of doped polyaniline in the preparation of coating slurry, and the problems of improving the adhesion of the doped polyaniline to the surface of a positive electrode material and prolonging the diffusion path of lithium ions (for example, lithium ion batteries, and other types of secondary batteries can be adopted, of course), the volume average particle diameter DV50 of the doped polyaniline is selected to have a range of 15-35 mu m. The volume average particle diameter DV50 of the polyaniline in the doped state is selected to have a range of values from 20 μm to 30 μm.

The values of 15 μm to 35 μm described above include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, dot values in the examples and values of 15 μm, 17 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, 35 μm, etc., and range values between any two of the above dot values.

The values of 20 μm to 30 μm described above include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, dot values in the examples and range values between any two of the above-described dot values of 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, and the like.

In one embodiment, the range of values for the apparent density of the doped polyaniline is 0.2g/cm ³ To 0.6g/cm ³ . In one embodiment of the present invention, in one embodiment,the apparent density of the doped polyaniline has a range value of 0.3g/cm ³ To 0.5g/cm ³ 。

Apparent density refers to the ratio of the mass of a material to the apparent volume. The apparent volume is the real volume plus closed pore volume plus open pore volume.

The determination of apparent density, the mass of a sample is obtained by a conventional mass measurement method, the apparent volume of the sample is obtained by a conventional volume measurement method, and a calculation formula of the apparent density is that the apparent density=mass/apparent volume, and the apparent volume v2=sh×a, wherein: s-area, cm ² The method comprises the steps of carrying out a first treatment on the surface of the H-thickness, cm; a-number of samples, V2-apparent volume of sample, cm ³ 。

The apparent density is related to the particle size and porosity of the material, and is within this range, the doped polyaniline has a suitable size and porosity to facilitate the transport of lithium ions (for example, lithium ion batteries, but other types of secondary batteries are also possible) in the coating. Based on this, the apparent density of the polyaniline in a doped state was in the range of 0.2g/cm ³ To 0.6g/cm ³ . The apparent density of the doped polyaniline has a range value of 0.3g/cm ³ To 0.5g/cm ³ 。

0.2g/cm as described above ³ To 0.6g/cm ³ Wherein the values include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, the point values and 0.2g/cm in the examples ³ 、0.3g/cm ³ 、0.4g/cm ³ 、0.5g/cm ³ 、0.6g/cm ³ Etc., and range values between any two of the above-mentioned point values.

0.3g/cm as described above ³ To 0.5g/cm ³ Wherein the values include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, the point values and 0.3g/cm in the examples ³ 、0.35g/cm ³ 、0.4g/cm ³ 、0.45g/cm ³ 、0.5g/cm ³ Etc., and range values between any two of the above-mentioned point values.

In one embodiment, the molecular weight range of the doped polyaniline is 40000 to 80000.

In one embodiment, the molecular weight range of the doped polyaniline is 50000 to 60000.

The molecular weight, relative molecular mass, is the sum of the relative atomic masses (Ar) of the atoms in the formula, and is denoted by the symbol Mr, and the unit is 1.

The molecular weight of the doped polyaniline is measured and tested by a mass spectrometer.

The molecular weight of the doped polyaniline is in the above range, so that the cohesiveness of the polyaniline and the wettability of the cathode to the electrolyte can be improved.

Among 40000 to 80000 described above, the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, point values in the embodiment and 40000, 50000, 60000, 70000, 75000, 80000, and the like, and range values between any two of the above-described point values.

Among the above 50000 to 60000, the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the dot values in the embodiment, and the values of the range between 50000, 53000, 55000, 60000, and the like, and any two of the dot values described above.

It is understood that the intrinsic polyaniline means that the polyaniline is not doped with any substance. The doped polyaniline refers to a state in which polyaniline is doped with a compound. The doped polyaniline in the application refers to doped polyaniline formed by proton doping of polyaniline. After the polyaniline is doped, the conductivity of the polyaniline is improved.

It is understood that polyaniline is a linear high molecular polymer with long-range conjugated structure connected end to end, is composed of an oxidized form containing 'benzene-quinone' alternately and a continuous reduced form containing 'benzene-benzene', and has excellent cohesiveness and electrochemical performance.

In terms of conductivity, the electrical activity of polyaniline results from the delocalized pi-conjugated electron (P-electron conjugated) structure in the molecular chain: with the expansion of the P electron system in the molecular chain, the P bonding state and the P inverse bonding state respectively form a valence band and a conduction band,the delocalized P-electron conjugated structure is doped to form P-type and N-type conductivity. The doping process of polyaniline generates H by decomposition of doped protonic acid ⁺ And anions (e.g. Cl) ^- Sulfate, phosphate, etc.) into the backbone, and combine with the N atoms in the amine and imine groups to form polar and bipolar delocalization into P bonds throughout the molecular chain, thereby rendering the polyaniline more conductive. The doped polyaniline is affected by the preparation method, the doping agent, the solvent, the doping proportion and the like, and the conductivity difference is larger. When inorganic acid is doped, the conductivity can reach 0.1S/cm-24S/cm; when organic acid is doped, the conductivity can reach 200S/cm-400S/cm, but the cost is greatly increased.

O in the lattice when the high nickel positive electrode material is exposed to an open container ₂ ^- With CO in air ₂ And H ₂ O reacts to generate CO ₃ ^2- Or OH (OH) ^- Producing Li ₂ CO ₃ And LiOH impurities. On the one hand, the electrolyte decomposition is accelerated to generate HF and H ₂ Byproducts such as O; on the other hand, oxygen release from the positive electrode causes the positive electrode material to be converted from a layered structure to a spinel structure, and finally, the spinel is converted to a rock salt stone structure, resulting in rapid decay of the battery capacity.

On a stable interface, doping polyaniline is coated on the surface of the anode material, so that the interface electrochemical reaction of the anode material is optimized; the interface stability between the positive electrode and the electrolyte is improved, and the gas production caused by oxygen release of the positive electrode and side reaction of the positive electrode and the electrolyte is reduced. For the negative electrode, imine nitrogen in the doped polyaniline can be coordinated with F and other anionic groups in the electrolyte, so that acidic substances such as HF and the like generated by decomposition of lithium salt and electrolyte can be removed, migration of the acidic substances to the negative electrode is relieved, the integrity and stability of a negative electrode-electrolyte interface are improved, and gas production is reduced.

In the aspect of electrical performance, the doped polyaniline can promote electrolyte to permeate to the surface of an active material, so that the electrode material is deionized, the volume effect is reduced, delocalized pi conjugated electrons on the skeleton of the electrode material effectively improve the electronic conductivity of the adhesive skeleton, and the rate capability can be improved.

It will be appreciated thatThe doping process of polyaniline generates H by decomposing doped protonic acid ⁺ And anions (e.g. Cl) ^- Sulfate radical, phosphate radical, etc.) into the main chain, and combines with the N atoms in the amine and imine groups to form polar and bipolar ions delocalized into the P bond of the whole molecular chain, thereby leading the polyaniline to exhibit higher conductivity; on the other hand, the introduction of the protonic acid improves the conductivity and also improves the problem of poor polyaniline solubility caused by strong interaction between chains to a certain extent, the doped polyaniline is uniformly distributed among the positive electrode active particles to form a mosaic structure, and hydrophilic groups on the surface of the doped polyaniline can effectively improve the hydrophilicity of the electrode, so that the purpose of promoting the electrolyte to permeate into the surface of the positive electrode active material is achieved.

Meanwhile, the redox mechanism of doped polyaniline in the charge and discharge process is applied to realize deionization, enhance the ion conductivity of the electrode, reduce the polarization phenomenon in the charge process and improve the deionization performance, so that the migration rate of lithium ions (taking a lithium ion battery as an example, and of course, other types of secondary batteries) is improved, and the rate capability of the battery is improved; the doped polyaniline is distributed among the positive electrode active substances, and similar to a coating effect, the expansion and shrinkage, namely the volume effect, of the positive electrode material in the charge and discharge processes can be improved.

That is, for the positive electrode: o in the lattice when the high nickel positive electrode material is exposed to an open container ₂ ^- With CO in air ₂ And H ₂ O reacts to generate CO ₃ ^2- Or OH (OH) ^- Producing Li ₂ CO ₃ And LiOH and other by-products, which can deteriorate the decomposition of the electrolyte to HF, H ₂ Byproducts such as O; the oxygen release of the positive electrode is quickened, so that the positive electrode material is converted from a layered structure to a spinel structure, and finally, the spinel is converted to a rock salt stone structure, so that the battery capacity is quickly attenuated. The doped polyaniline is coated on the surface of the positive electrode material, so that the interface electrochemical reaction of the positive electrode material is optimized; the CEI stability of the interface between the positive electrode and the electrolyte is improved, and the gas production caused by oxygen release of the positive electrode and side reaction of the positive electrode and the electrolyte is reduced.

For electrolyte and negative electrodeIn terms of: the imine nitrogen in the doped polyaniline can coordinate with the F-like anionic groups in the electrolyte, thereby forming a complex with the lithium salt (such as LiPF ₆ ) Acidic substances such as HF and the like are removed in decomposition, migration of the acidic substances to the negative electrode is blocked, and the integrity and stability of a negative electrode-electrolyte interface (SEI) are improved.

In addition, the doped polyaniline can promote electrolyte to permeate to the surface of the active material, is favorable for deionizing the electrode material and reducing the volume effect, and the delocalized pi conjugated electrons on the skeleton of the polyaniline effectively improve the conductivity of the adhesive skeleton and optimize the rate capability.

In one embodiment, the molar ratio of dopant to aniline in the doped polyaniline ranges from 25% to 45%.

In one embodiment, the molar ratio of dopant to aniline in the doped polyaniline ranges from 32% to 40%.

Preparing doped polyaniline: 15g of aniline and 75mL of hydrochloric acid (1 mol/L) were added to a 500mL three-necked flask, a certain amount of ammonium persulfate was dissolved in 50mL of hydrochloric acid, and the mixture was slowly dropped in a dropping funnel for 30 minutes and reacted in a constant temperature water bath for about 6 hours. And (3) after the reaction is finished, washing the filtered product by (1 mol/L) hydrochloric acid, washing the product by ethanol and purified water in sequence, and drying in vacuum at 65 ℃ to obtain the polyaniline doped with the hydrochloric acid.

The amount of the dopant in the doped polyaniline can control the conductivity of the doped polyaniline, and in particular, H is generated by decomposing doped protonic acid during the doping process of the polyaniline ⁺ And anions (e.g. Cl) ^- Sulfate, phosphate, etc.) into the backbone, and combine with the N atoms in the amine and imine groups to form polar and bipolar delocalization into P bonds throughout the molecular chain, thereby rendering the polyaniline more conductive. Considering that imine nitrogen in polyaniline can coordinate with F plasma groups in electrolyte, in order to make a certain amount of imine nitrogen in polyaniline coordinate with F plasma groups in electrolyte, eliminating acidic substances such as HF and the like generated by decomposition of lithium salt and electrolyte, relieving migration of acidic substances to a negative electrode, improving the integrity and stability of a negative electrode-electrolyte interface, the range value of the mole ratio of doping agent to aniline in doped polyaniline is25% to 45%. The molar ratio of dopant to aniline in the heteromorphic polyaniline ranges from 32% to 40%.

The values of 25% to 45% above include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the dot values in the embodiments and the range values of 25%, 28%, 30%, 35%, 38%, 45%, etc., and between any two of the dot values above.

The above 32% to 40% values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, point values in the embodiments and 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc., and range values between any two of the above point values.

In one embodiment, the doped polyaniline comprises an organic acid doped polyaniline and/or an inorganic acid doped polyaniline.

In one embodiment, the doped polyaniline comprises an inorganic acid doped polyaniline and the inorganic acid doped polyaniline comprises a hydrochloric acid doped polyaniline.

The organic acid doped polyaniline or the inorganic acid doped polyaniline can improve the conductivity of the doped polyaniline, for example, the organic acid doped polyaniline or the inorganic acid doped polyaniline can be respectively used in the slurry preparation process, and the organic acid doped polyaniline and the inorganic acid doped polyaniline can be simultaneously used.

In view of the relatively high price of organic acids, inorganic acid doping may be preferably employed, for example, inorganic acid doped polyaniline includes hydrochloric acid doped polyaniline.

It will be appreciated that the primary role of the protic acid in the aniline polymerization process is to provide protons and to ensure that the polymerization system has sufficient acidity to allow the reaction to take place in a 1, 4-coupling fashion. Polymerization of aniline occurs in a 1, 4-coupling fashion under appropriate acidity conditions. The acid degree is too low, and the polymerization is carried out in a head-to-tail mode and a head-to-head mode, so that a large amount of azo byproducts are obtained. When the acidity is too high, substitution reaction on the aromatic ring occurs again, and the conductivity decreases.

Theoretically HCl, HBr, H ₂ SO ₄ 、HClO ₄ 、HNO ₃ 、CH ₃ COOH、HBF ₄ And p-toluenesulfonic acid, and the like, to obtain polyaniline in H ₂ SO ₄ ，HCl，HClO ₄ High conductivity polyaniline can be obtained in the system, and the polyaniline is prepared in HNO ₃ ，CH ₃ The polyaniline obtained in the COOH system is an insulator.

And use H ₂ SO ₄ ，HClO ₄ When non-volatile protonic acid is doped, the protonic acid can remain on the surface of polyaniline under vacuum drying, so that the quality of the product is affected.

The organic proton acid doped polyaniline has application prospect, such as dodecyl sulfonic acid, dodecyl benzene sulfonic acid, camphorsulfonic acid, naphthalene sulfonic acid, 2, 4-dinitronaphthol-7-sulfonic acid (NONSA) and the like serving as an acidic medium and a doping agent, and can obtain a functional proton acid doped polymer, but the organic acid has higher cost.

Hydrochloric acid doping can lead polyaniline to obtain higher conductivity, and because HCl is easy to volatilize, easy to dedoping and low in cost, the application is preferably hydrochloric acid doping.

In one embodiment, the thermal decomposition temperature of the doped polyaniline is greater than 350 ℃.

In one embodiment, the conductivity of the doped polyaniline ranges from 0.2S/cm to 0.6S/cm.

In one embodiment, the conductivity of the doped polyaniline ranges from 0.3S/cm to 0.5S/cm.

Conductivity, which may also be referred to as conductivity. The product of this quantity and the electric field strength E in the medium is equal to the conduction current density J.

The conductivity testing method adopts a powder resistivity tester to test: weighing a certain mass of sample, adjusting the depth of a feeding cavity, adding the sample into the feeding cavity, applying pressure, manually collecting data, and recording powder resistivity test results of different pressure points.

In order to improve the migration of lithium ions (for example, lithium ion batteries, but of course, other types of secondary batteries) in the positive electrode sheet, the conductivity range of the doped polyaniline in the application is 0.2S/cm to 0.6S/cm. The conductivity range of the doped polyaniline in the application is 0.3S/cm to 0.5S/cm.

Among the above 0.2S/cm to 0.6S/cm, the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the dot values in the embodiments and the range values between 0.2S/cm, 0.3S/cm, 0.4S/cm, 0.5S/cm, 0.6S/cm, and the like.

Among the above 0.3S/cm to 0.5S/cm, the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the dot values in the embodiments and the range values between 0.3S/cm, 0.354S/cm, 0.4S/cm, 0.5S/cm, and the like.

In one embodiment, the mass of the doped polyaniline is 0% < W0 < 100% of the mass of the binder.

In one embodiment, the mass of the doped polyaniline is 30% to 80% of the mass of the binder.

In one embodiment, the mass of the doped polyaniline is 40% to 70% W0% of the mass of the binder.

In one embodiment, the mass of the doped polyaniline is 40% to 60% W0% of the mass of the binder.

The mass ratio of the doped polyaniline to the binder is the mass ratio, and in the preparation process of the binder, the mass ratio of the A component and the polyaniline component in the binder is recorded to be m1 and m2 respectively, and the mass ratio of the polyaniline to the binder is m2: (m1+m2), it is understood that the a component may be a component having a binder function, for example, polyvinylidene fluoride.

The doped polyaniline has adhesive property and conductive property, and can improve the performance of the battery, and the mass of the doped polyaniline can occupy the mass of the adhesive with the ratio of W0 being more than 0 percent and less than 100 percent. The mass of the doped polyaniline can account for 30 percent to 80 percent of the mass of the binder. The mass of the doped polyaniline can account for 40 percent to 70 percent of the mass of the binder. It is understood that, within a certain range, the battery performance is improved with increasing amounts of doped polyaniline, and the adhesion between the coating and the current collector is reduced with further increasing amounts of doped polyaniline.

In the above 0% < W0 < 100%, values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, specific examples include, but are not limited to, point values in the examples and values of 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, etc., and ranges between any two of the above point values.

The above 30% or less and 80% of W0 or less, the values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the dot values in the examples and the range values between any two of the dot values described above, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, and the like.

Among the above 40% or less and 70% or less W0% or less, values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, point values in the examples and values of 40%, 42%, 43%, 45%, 48%, 50%, 52%, 53%, 55%, 58%, 60%, 62%, 63%, 65%, 68%, 70%, etc., and range values between any two of the above-mentioned point values.

Among the above 40% or less and the W0% or less and 60%, values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, point values in the examples and 40%, 42%, 43%, 45%, 48%, 50%, 52%, 53%, 55%, 58%, 60%, etc., and range values between any two of the above-mentioned point values.

In one embodiment, the doped polyaniline has a mass fraction of more than 0% and less than 10% of the coating mass.

In one embodiment, the doped polyaniline has a mass fraction of 4% to 6% of the coating mass.

The doped polyaniline is introduced into the coating, so that the performance of the secondary battery can be improved, and the mass of the doped polyaniline accounts for more than 0% and less than 10% of the mass of the coating. The mass of the doped polyaniline accounts for 4 to 6 percent of the mass of the coating.

Above greater than 0%, less than 10%, values include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, the point values in the examples and the range values between 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc., and any two of the point values described above.

The values of 4% to 6% above include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the dot values in the embodiments and 4%, 4.5%, 5%, 5.5%, 6%, etc., and the range values between any two of the dot values described above.

In order to ensure that the battery has better quick charge capacity, the unit area weight of the pole piece is defined as M, and the positive electrode meets 350g/mm ² ≤M≤600g/mm ² The negative electrode satisfies 170g/mm ² ≤M≤292g/mm ² 。

In one embodiment, the coating further comprises a conductive agent, wherein the mass parts of the positive electrode material, the conductive agent and the binder are respectively 85-92 parts, 1.5-6 parts and 1.5-5 parts.

The conductive agent is used for ensuring good charge and discharge performance of the electrode, a certain amount of conductive substances are generally added during the manufacture of the electrode plate, and micro-current collection is performed between active substances and between the active substances and the current collector, so that the contact resistance of the electrode is reduced to accelerate the movement rate of electrons, and meanwhile, the migration rate of lithium ions (for example, a lithium ion battery is taken as an example, and other types of secondary batteries can be used as a matter of course) in the electrode material is effectively improved, so that the charge and discharge efficiency of the electrode is improved.

In order to ensure that the coating has higher capacity, proper conductivity and bonding performance, the mass parts of the anode material, the conductive agent and the bonding agent in the coating are respectively 85-92 parts, 1.5-6 parts and 1.5-5 parts. It is understood that the amount of the conductive agent may be appropriately reduced in consideration of the conductivity of the doped polyaniline, and for this reason, the lower limit of the mass percentage of the conductive agent is 1.5 parts.

In one embodiment, the coating comprises a positive electrode material comprising a lithium-containing transition metal oxide comprising

Considering the adverse reaction of the interface of the positive electrode plate and the electrolyte, for the nickel cobalt lithium manganate material with more nickel content, the active material crystal lattice releases oxygen more easily, so that the cell expands and deforms, and the cycle life is influenced. The high nickel material contains transition metal ions with high oxidability, and the electrolyte is decomposed on the surface of the positive electrode to form a positive electrode-electrolyte interface with complex surface chemistry. The high nickel material is exposed to an open container, O in the crystal lattice ₂ ^- With CO in air ₂ And H ₂ O reacts to generate CO ₃ ^2- Or OH (OH) ^- Producing Li ₂ CO ³ And LiOH impurities, which accelerate the electrolyte to decompose to form HF, resulting in a phase change of the positive electrode material from lamellar to spinel. Ni in high nickel material ²⁺ / ⁴⁺ The potential is high, and electrolyte is decomposed on the surface of the positive electrode of the high-nickel material, so that a thicker SEI film is formed on the negative electrode.

That is, the above problems are more remarkable in the positive electrode sheet of the high nickel material, and for this purpose, the positive electrode material of the present application comprises a lithium-containing transition metal oxide comprisingFor the positive electrode plate comprising the high-nickel material, polyaniline is used in the positive electrode plate comprising the high-nickel material, so that the polyaniline in the adhesive can ensure the basic adhesive performance and improve the electricityPool performance. Specifically, the electrochemical performance and the interfacial electrochemical reaction of the positive electrode material are optimized; thereby improving the stability of the anode material and the electrochemical interface and improving the gas production and capacity attenuation of the battery.

In addition, the doped polyaniline can promote electrolyte to permeate to the surface of the active material, is favorable for deionizing the electrode material and reducing the volume effect, and delocalized pi conjugated electrons on the skeleton of the polyaniline effectively improve the electron conductivity of the adhesive skeleton, so that the rate capability is improved.

In one embodiment, the coating comprises at least two active layers, wherein the at least two active layers are arranged on the same side of the current collector layer by layer, at least one active layer is arranged close to the current collector, and at least one other active layer is arranged on one side of the at least one active layer, which is away from the current collector; the doped polyaniline in at least one active layer is defined as W1 in percentage by mass, and the doped polyaniline in at least one other active layer is defined as W2 in percentage by mass, so that W1 is less than W2, and W1 is more than or equal to 0% and less than 100%.

The at least two active layers may be two active layers, three active layers, four active layers, five active layers, or the like, and are not particularly limited.

At least two active layers are stacked on the same side of the current collector, as shown in fig. 1, which is a schematic structural diagram of the positive electrode sheet 100, and the two active layers are sequentially stacked on the same side of the current collector, for example, one active layer 20 is disposed on the surface of the current collector 10, and the other active layer 30 is disposed on a side of the active layer 20 facing away from the current collector 10. When the active layer has three layers, the three active layers are sequentially stacked on the same side of the current collector.

At least one active layer is arranged close to the current collector, at least one other active layer is arranged on one side, away from the current collector, of the at least one active layer, and at least one active layer is arranged close to the current collector and at least one other active layer is arranged far away from the current collector as at least two active layers are arranged on the current collector in a stacked mode.

The weight percentage of the doped polyaniline in the active layer to the binder is W1, which means that the binder in the active layer consists of an A component and the doped polyaniline, the weight of the A component is a, the weight of the doped polyaniline is b, and W1=b/(a+b) ×100%.

The doped polyaniline has certain bonding capability, but has poor bonding capability compared with the common bonding agent of the secondary battery, and in order to ensure good bonding capability between the coating and the current collector and improve the interface stability of the anode and the electrolyte, the coating at least comprises two active layers, at least two active layers are arranged on the same side of the current collector, at least one active layer is arranged close to the current collector, and at least one other active layer is arranged on one side of the at least one active layer away from the current collector; the method comprises the steps of defining that the doped polyaniline in at least one active layer accounts for W1 in percentage by mass of the binder, and the doped polyaniline in at least one other active layer accounts for W2 in percentage by mass of the binder, so that W1 is smaller than W2.

That is, the amount of doped polyaniline in the active layer near the current collector is less than the amount of doped polyaniline in the active layer far from the current collector, for example, as shown in fig. 1, one active layer 20 is near the current collector, and the doped polyaniline in the layer accounts for less mass percent of the binder than the doped polyaniline in the other active layer 30. So that a proper amount of doped polyaniline is in the active layer at or near the interface to improve the stability of the interface between the active layer and the electrolyte. The amount of doped polyaniline in an active layer 20 near the current collector is reduced, so that the amount of other components having a binding effect in the binder is increased, and the adhesion between an active layer 20 and the current collector is improved.

In the above-mentioned 0% +.W1 < 100%, values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, specific examples include, but are not limited to, the dot values in the examples and 0%, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc., and the range values between any two of the above-mentioned dot values.

In one embodiment, 0% or less than or equal to W1% or less than or equal to 50%, and/or 40% or less than or equal to W2% or less than or equal to 60%.

In order to improve the comprehensive performance of the pole piece, the weight percentage of the doped polyaniline in at least one active layer to the binder is W1, the weight percentage of the doped polyaniline in at least one other active layer to the binder is W2, and the W1 is more than or equal to 0% and less than or equal to 50%, and/or the W2 is more than or equal to 40% and less than or equal to 60%.

Within the above range, the active layer can ensure good adhesion with the current collector, and can improve the interface stability between the coating and the electrolyte.

Among the above 0% or less and the W1% or less and 50%, values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the dot values in the examples and 0%, 1%, 10%, 20%, 30%, 40%, 45%, 50%, etc., and the range values between any two of the above dot values.

Among the above 40% or less and the W2% or less and 60%, values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, point values in the embodiments and 40%, 45%, 50%, 55%, 60%, etc., and range values between any two of the above-mentioned point values.

In consideration of the difference in the amount of doped polyaniline added between adjacent active layers, an interface exists between adjacent active layers, and in order to enable the active layers close to the current collector side to effectively exert capacity, the thickness of the active layers close to the current collector side is greater than that of the active layers far from the current collector. For example, as shown in FIG. 1, the active layers are two, and the ratio of the thickness of one active layer 20 to the thickness of the other active layer is 3:2.

In an embodiment, the application further provides a battery cell, which comprises the positive electrode plate.

In an embodiment, the application further provides a battery, which comprises the battery cell.

In an embodiment, the application further provides an electric device, which comprises the battery.

The battery (secondary battery, battery module, battery pack) and the electric device according to the present application will be described below with reference to the drawings.

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

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The diaphragm is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and can enable ions to pass through. The separator is the improved separator of the present application described above.

The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector.

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

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

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

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

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

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode 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 may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material 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 polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the anode active material may employ an anode active material for a battery, which is well 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 at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from 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 optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

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

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The application is not particularly limited in the kind of electrolyte, and may be selected according to the need.

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

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one 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, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

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

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

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

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

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

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

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 2 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 3, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

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

Fig. 4 is a battery module 4 as an example. Referring to fig. 4, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 5 and 6 are battery packs 1 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

In addition, the application also provides an electric device which comprises at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The power utilization device may include, but is not limited to, mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, and the like.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 7 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples

Example 1

And (3) baking the doped polyaniline and the powder for 8 hours at 100 ℃ in a flowing air atmosphere to remove the water.

Preparation of positive electrode plate

Taking NCM811 as an anode active material, dissolving the anode active material, conductive agent carbon black Super P, binder polyvinylidene fluoride (PVDF) and doped polyaniline in a solvent N-methylpyrrolidone (NMP) according to a proportion (87 wt%, 3 wt%, 90 wt% and 10 wt%), and stirring for 200min to uniformly disperse to obtain anode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and cutting to obtain the positive electrode plate. The doped polyaniline is hydrochloric acid doped polyaniline, and the molar ratio of the hydrochloric acid dopant to the aniline is 30%.

Preparation of negative electrode plate

Active substances of artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC-Na) are mixed according to the weight ratio of 95 percent: 1.5%:2%:1.5 percent of the solution is dissolved in deionized water, and the negative electrode slurry is prepared after uniform mixing; and coating the negative electrode slurry on a negative electrode current collector copper foil, and drying, cold pressing and slitting to obtain a negative electrode plate.

Preparation of lithium ion batteries

Sequentially winding the positive electrode plate, the isolating film and the negative electrode plate to obtain a bare cell, wherein the isolating film plays a role in isolating between the positive electrode plate and the negative electrode plate, vacuum baking for 24 hours after shaping to remove water, injecting electrolyte and sealing to obtain an uncharged cell; and sequentially performing procedures such as standing, formation, capacity test and the like to obtain the lithium ion battery product.

Battery capacity retention test

Taking example 1 as an example, the battery capacity retention test procedure is as follows: the corresponding battery of example 1 was charged to 4.4V at a constant current of 1/3C, then charged to 0.05C at a constant voltage of 4.4V, left to stand for 10min, then discharged to 2.5V at 1/3C, and the resulting capacity was designated as initial capacity C0. Repeating the above steps for the same battery, and recording the discharge capacity Cn of the battery after the nth cycle, wherein the battery capacity retention rate pn=cn/c0 is 100% after each cycle.

Storage gas production volume test

Before storage, the battery cell is adjusted to be in a full charge state at 25 ℃, the battery cell is charged to 4.4V by a constant current of 1/3C, and then is charged to 0.05C by a constant voltage of 4.4V, and the battery cell is placed for 10min. Testing the initial volume V0, discharging once every 5d, standing for 2h, cooling to room temperature, testing the volume of the battery cell, and charging into the furnace; stopping storing when the volume of the battery expands to 50% of the original volume or is stored for 120 days; the drainage method detects the volume change of the battery.

Examples 2 to 16, on the basis of example 1, the variables were changed: the amounts of the hydrochloric acid doped polyaniline, the kinds of the dopants, DV50, the molar ratio of the dopants to the aniline, resulted in examples 2 to 16. Wherein, in example 7, the dopant was changed to HClO based on example 11 ₄ 。

Comparative example 1, no doped polyaniline was added on the basis of example 1.

Comparative example 2, an eigenstate polyaniline, which means undoped polyaniline, was added on the basis of example 1.

Table 1 list of experimental data

Example 17

Preparation of positive electrode plate

Preparation of first cathode slurry

The NCM811 is taken as an anode active material, the anode material, the conductive agent carbon black Super P and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methyl pyrrolidone (NMP) according to the proportion (87 wt%, 3 wt% and 10 wt%) and stirred for 200min to be uniformly dispersed, and then the first anode slurry is obtained.

Preparation of a second Positive electrode slurry

The NCM811 is taken as an anode active material, the anode material, the conductive agent carbon black Super P, the binder polyvinylidene fluoride (PVDF) and the doped polyaniline are dissolved in a solvent N-methylpyrrolidone (NMP) according to a proportion (87 wt%, 3 wt%, 7 wt% and 3 wt%) and are stirred for 200min to be uniformly dispersed, so that a second anode slurry is obtained. The doped polyaniline is hydrochloric acid doped polyaniline, and the mole ratio of the doping agent to the aniline is 30%.

And sequentially and uniformly coating the first positive electrode slurry and the second positive electrode slurry on the positive electrode current collector to obtain two active layers, and then drying, cold pressing and cutting to obtain the positive electrode plate.

The preparation of the negative electrode sheet and the preparation of the lithium ion battery were the same as in example 1.

Examples 18 to 20, on the basis of example 17, the variables were changed: the duty cycle of the polyaniline in the doped state in the second coating layer resulted in examples 18 to 20.

Table 2 list of experimental data

As can be seen from the data in table 1, the addition of the doped polyaniline to the binder gave better cell performance. As can be seen from table 2, the active layer is composed of a plurality of layers, and the active layer (first coating layer) close to the current collector is not added with the doped polyaniline, so that good adhesion between the coating layer and the current collector can be ensured, while the active layer (second coating layer) far from the current collector is added with the doped polyaniline, and in a proper range, the performance of the battery is improved. The foregoing description of the preferred embodiments of the present invention should not be construed as limiting the scope of the invention, but rather as utilizing equivalent structural changes made in the description of the invention and the accompanying drawings, or as directly/indirectly employed in other related technical fields, are included in the scope of the invention.

Claims

1. The positive electrode plate is characterized by comprising a current collector and a coating arranged on at least one side of the current collector, wherein the coating comprises a binder, and the binder comprises doped polyaniline;

The molar ratio of the dopant to the aniline in the doped polyaniline ranges from 25% to 45%;

the conductivity range value of the doped polyaniline is 0.2S/cm to 0.6S/cm;

the mass of the doped polyaniline accounts for 3 to 6 percent of the mass of the coating;

the doped polyaniline comprises organic acid doped polyaniline and/or inorganic acid doped polyaniline.

2. The positive electrode sheet according to claim 1, wherein the volume average particle diameter DV50 of the doped polyaniline has a value in the range of 15 μm to 35 μm.

3. The positive electrode sheet according to claim 2, wherein the volume average particle diameter DV50 of the doped polyaniline has a value in the range of 20 μm to 30 μm.

4. A positive electrode sheet according to any one of claims 1 to 3, wherein the range of values of apparent density of the doped polyaniline is 0.2g/cm ³ To 0.6g/cm ³ 。

5. The positive electrode sheet according to claim 4, wherein the range of values of the apparent density of the doped polyaniline is 0.3g/cm ³ To 0.5g/cm ³ 。

6. The positive electrode sheet according to any one of claims 1 to 3, 5, wherein the molecular weight range of the doped polyaniline is 40000 to 80000.

7. The positive electrode sheet of claim 6, wherein the doped polyaniline has a molecular weight range from 50000 to 60000.

8. The positive electrode sheet of any one of claims 1 to 3, 5, 7, wherein the molar ratio of dopant to aniline in the doped polyaniline ranges from 32% to 40%.

9. The positive electrode sheet of claim 1, wherein the doped polyaniline comprises an inorganic acid-doped polyaniline, and wherein the inorganic acid-doped polyaniline comprises a hydrochloric acid-doped polyaniline.

10. The positive electrode sheet of any one of claims 1 to 3, 5, 7, 9, wherein the doped polyaniline has a thermal decomposition temperature greater than 350 ℃.

11. The positive electrode sheet of claim 1, wherein the doped polyaniline has a conductivity in the range of 0.3S/cm to 0.5S/cm.

12. The positive electrode sheet according to any one of claims 1 to 3, 5, 7, 9, 11, wherein the mass of the doped polyaniline is 0% < W0 < 100% of the mass of the binder.

13. The positive electrode sheet according to claim 12, wherein the mass of the doped polyaniline is 30% or more and 80% or less of the mass of the binder.

14. The positive electrode sheet according to claim 13, wherein the mass of the doped polyaniline is 40% or more and 70% or less than the mass of the binder.

15. The positive electrode sheet according to claim 14, wherein the mass of the doped polyaniline is 40% or less and 60% or less based on the mass of the binder.

16. The positive electrode sheet of any one of claims 1 to 3, 5, 7, 9, 11, 13 to 15, wherein the coating comprises a positive electrode material comprising a lithium-containing transition metal oxide comprising

17. The positive electrode sheet of any one of claims 1 to 3, 5, 7, 9, 11, 13 to 15, wherein the coating comprises at least two active layers, the at least two active layers being disposed one upon the other on the same side of the current collector, at least one of the active layers being disposed adjacent to the current collector, at least one other of the active layers being disposed on a side of the at least one active layer facing away from the current collector;

and defining that the mass percentage of the doped polyaniline in at least one active layer to the binder is W1, and the mass percentage of the doped polyaniline in at least one other active layer to the binder is W2, wherein W1 is more than or equal to W2, and W1 is more than or equal to 0% and less than or equal to 100%.

18. The positive electrode sheet of claim 17, wherein 0% or less W1% or less than 50%, and/or 40% or less W2% or less than 60%.

19. A battery cell comprising the positive electrode sheet according to any one of claims 1 to 18.

20. A battery comprising the cell of claim 19.

21. An electrical device comprising the battery cell of claim 19 or the battery of claim 20.