CN116093276A

CN116093276A - Positive electrode material, preparation method, positive electrode plate, preparation method and application

Info

Publication number: CN116093276A
Application number: CN202211515930.1A
Authority: CN
Inventors: 朱翠翠; 张继君; 王少飞; 魏奕民
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-11-30
Filing date: 2022-11-30
Publication date: 2023-05-09

Abstract

The application provides a positive electrode material and a preparation method thereof, a positive electrode plate and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electric device. The positive electrode material comprises an active material and a solid electrolyte layer coated on the surface of the active material; the electrochemical window of the solid electrolyte layer is larger than the electrochemical window of the active material. In the positive electrode material, the electrochemical window of the positive electrode material is effectively improved through the introduction of the solid electrolyte layer, the irreversible change of crystal lattice of the positive electrode material in the lithium removal and intercalation process can be restrained, the positive electrode material keeps a stable structure, the stability of the positive electrode material under the high-voltage condition can be improved, and the performance of the battery under the high-voltage condition is improved.

Description

Positive electrode material, preparation method, positive electrode plate, preparation method and application

Technical Field

The application relates to the technical field of secondary batteries, in particular to a positive electrode material and a preparation method thereof, a positive electrode plate and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electric device.

Background

The secondary battery has the characteristics of high energy density, environmental friendliness and the like. With the increasing consumer demand, batteries with stable performance under high voltage conditions are becoming a popular resort. In the conventional secondary battery, the stability of the positive electrode material is poor under the high voltage condition, so that the use of the battery under the high voltage condition is restricted.

Disclosure of Invention

The application provides a positive electrode material, which comprises an active material and a solid electrolyte layer coated on the surface of the active material; the electrochemical window of the solid electrolyte layer is larger than the electrochemical window of the active material.

In the positive electrode material, the electrochemical window of the positive electrode material is effectively improved through the introduction of the solid electrolyte layer, the irreversible change of crystal lattice of the positive electrode material in the lithium removal and intercalation process can be restrained, the positive electrode material keeps a stable structure, the stability of the positive electrode material under the high-voltage condition can be improved, and the performance of the battery under the high-voltage condition is improved.

Drawings

Fig. 1 is a schematic view of a secondary battery according to an embodiment of the present application.

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

Fig. 3 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 4 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 5 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 4.

Fig. 6 is a schematic view of an electric device in which the secondary battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1. a battery pack; 2. an upper case; 3. a lower box body; 4. a battery module; 5. a secondary battery; 51. a housing; 52. an electrode assembly; 53. and a top cover assembly.

Detailed Description

Hereinafter, embodiments of a battery pack, a battery cell, a secondary battery, and an electric 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 a 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 this 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 and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.

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

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. 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.

Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may 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 both A and B are present.

Unless otherwise indicated, the terms "positive electrode sheet" and "positive electrode sheet" are used interchangeably in this application. The terms "negative electrode sheet" and "negative electrode sheet" have the same meaning and are used interchangeably. The terms "separator membrane" and "separator membrane" have the same meaning and are used interchangeably.

The application provides a positive electrode material. The positive electrode material comprises an active material and a solid electrolyte layer coated on the surface of the active material; the electrochemical window of the solid electrolyte layer is larger than the electrochemical window of the active material. In the cathode material, the electrochemical window of the cathode material is effectively improved through the introduction of the solid electrolyte layer, the irreversible change of crystal lattice of the cathode material in the lithium removal and intercalation process can be restrained, the cathode material can keep a stable structure, the stability of the cathode material under the high-voltage condition can be improved, and the performance of the battery under the high-voltage condition can be improved.

It can be understood that under the high voltage condition, the stability of the positive electrode material is effectively improved, and the voltage window for charging and discharging the battery comprising the positive electrode material is also effectively improved, so that the battery can be endowed with higher charging and discharging capacity, and a new direction is provided for the development of the high-capacity battery.

Meanwhile, during charge and discharge of the secondary battery, the positive electrode active material inevitably generates a certain amount of transition metal ions, such as when the lattice of the positive electrode material is irreversibly changed during delithiation, or when the electrolyte is included in the battery, the positive electrode material is easily subjected to H in the electrolyte ₂ Both O and HF may produce some amount of transition metal ions upon corrosion. Transition metal ions are easily migrated to the surface of the anode and reduced to metal, which is easily catalyzed by SEI film decomposition, consuming active lithium, and thus causing deterioration of electrical properties. In the cathode material, the solid electrolyte layer can reduce the content of transition metal ions through chemical reaction or adsorption reaction, for example, the transition metal ions are prevented from overflowing through complexation with the transition metal ions, so that the content of the transition metal ions in the battery is reduced, and the electrical performance of the secondary battery is improved.

It will be appreciated that the type of active material is not particularly limited in this application and may be selected from any known active materials. Alternatively, the active material in the present application may be selected from the positive electrode active materials listed below.

In one embodiment, the electrochemical window of the solid state electrolyte layer is greater than or equal to 5V. Therefore, the positive electrode material can be well protected under the high voltage condition, and the positive electrode material can still maintain good structural stability under the high voltage of 4.4V. Alternatively, the electrochemical window of the solid electrolyte layer is greater than or equal to 5.1V. Alternatively, the electrochemical window of the solid electrolyte layer is greater than or equal to 5.2V.

It can be understood that the electrochemical window is tested by adopting an electrochemical workstation linear volt-ampere test module, the material to be tested and the binder PVDF are mixed and dripped on the surface of the glassy carbon electrode in a mass ratio of 95:5 to be used as a working electrode, and 1M LiPF is used for testing ₆ The lithium sheet is used as a counter electrode for voltammetric curve test, the voltage range is 2.5-5V, the sweeping speed is 0.5mV/s, and the record oxidation potential is the electrochemical window. It is understood that when an electrochemical window of the solid electrolyte layer is to be measured, the material to be measured is a solid electrolyte. When an electrochemical window of the active material needs to be measured, the material to be measured is the active material.

In one embodiment, the solid electrolyte layer has a lithium ion conductivity of 0.8X10 or more ^-4 mS/cm. At this time, the lithium ions are facilitated to migrate rapidly inside the solid electrolyte layer, improving the cycle performance of the battery.

It can be appreciated that the ion conductivity measurement method: the alternating current impedance test adopts an electrochemical workstation impedance test module, a voltage disturbance mode PEIS, a disturbance voltage of 5mV and a frequency range of 200 kHZ-30 mHZ, the impedance test is carried out on the solid electrolyte sheet, and the ion conductivity of the electrolyte sheet is calculated.

Specifically, the solid electrolyte is an ion conductor and is not conductive to electrons, so before impedance testing, it is necessary to connect blocking Ag electrodes on both sides of the solid electrolyte sheet: polishing two sides of the sintered solid electrolyte to a certain thickness, coating silver paste to lead out Ag wires, and performing Ag burning treatment in a muffle furnace to enable the Ag electrode to be in close contact with the surface of the electrolyte. The resistance r=h/(ρs) is measured, and the ion conductivity σ is solved, where σ=1/ρ.

In one embodiment, the solid electrolyte layer has a thickness of 0.5nm to 5nm. The thickness of the solid electrolyte layer is in the range, so that the battery has low impedance, good cycle stability and good rate performance. Alternatively, the thickness of the solid electrolyte layer is 1nm to 4nm. Alternatively, the thickness of the solid electrolyte layer is 1nm to 3nm. Alternatively, the thickness of the solid electrolyte layer is 1nm to 2nm. Alternatively, the thickness of the solid electrolyte layer may be, but is not limited to, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, 5nm, or the like. It will be appreciated that the thickness of the solid electrolyte layer may be chosen to be in the range 0.5nm to 5nm.

In one embodiment, the solid electrolyte layer comprises a chemical composition of Li _a MX _a+3 Wherein a is more than or equal to 1 and less than or equal to 6; m is selected from cations of one or more of the following elements: al, ga, in, Y, zr, nb, sc, ti, mn and a La element; x is selected from anions containing one or more of the following elements: halogen, S, O and P.

Optionally, when X is an anion of halogen, the halogen element can migrate into the cathode material to form a transition layer, thereby reducing the migration energy of Li ions and stabilizing lattice oxygen, and further improving the lithium ion conductivity and structural stability of the cathode material.

In one embodiment, 2.ltoreq.a.ltoreq.4. Alternatively, a=3. In addition, a may represent an integer or a non-integer. As some alternative examples of a, a may be 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, etc. It will be appreciated that a may be chosen in other ways within the range of values 1 to 6.

In one embodiment, M is a +3 valent cation. For example, M includes Al ³⁺ 、Ga ³⁺ 、In ³⁺ 、Y ³⁺ 、Zr ³⁺ 、Nb ³ ⁺ 、Sc ³⁺ 、Ti ³⁺ 、Mn ³⁺ And +3 cation of La series element. Alternatively, M comprises Al ³⁺ 、Ga ³⁺ 、In ³⁺ 、Y ³⁺ 、Zr ³⁺ 、Nb ³⁺ 、Sc ³⁺ 、Ti ³⁺ 、Mn ³⁺ 、Er ³⁺ 、Tb ³⁺ 、Yb ³⁺ 、Lu ³⁺ 、La ³⁺ Ho ³⁺ One or more of the following. In addition, as an alternative example of X, X includes F ^- 、Cl ^- 、Br ^- 、I ^- 、S ^2- 、O ^2- PO (Positive and negative) ₄ ^- One or more of the following.

In one embodiment, the solid electrolyte layer includes Li ₃ InF ₆ 、Li ₃ YF ₆ 、Li ₃ ScF ₆ 、Li ₃ MnF ₆ 、Li ₃ ZrF ₆ 、Li ₃ YF ₆ 、Li ₃ InCl ₆ 、Li ₃ YCl ₆ 、Li ₃ ScCl ₆ 、Li ₃ MnCl ₆ 、Li ₃ ZrCl ₆ Li (lithium ion battery) ₃ YCl ₆ At least one of them.

The application also provides a preparation method of the positive electrode material. The preparation method of the positive electrode material comprises the following steps: forming a solid electrolyte layer on the surface of the active material; wherein the electrochemical window of the solid electrolyte layer > the electrochemical window of the active material. The atomic deposition method is a method based on ordered surface self-saturation chemical vapor deposition film, and can form a deposition layer with a thickness of a few atoms on the surface of the positive electrode material to realize uniform coating. The solid electrolyte layer with small thickness and good uniformity can be obtained by an atomic deposition method.

In one embodiment, a solid electrolyte layer is formed on the surface of the active material using atomic deposition. Optionally, forming the solid electrolyte layer on the surface of the active material includes the steps of: sequentially introducing a gas-phase Li source, a gas-phase X source and a gas-phase M source into the dispersed active material in a protective gas atmosphere to form a chemical composition of Li on the surface of the active material _a MX _a+3 Wherein 1.ltoreq.a.ltoreq.6, M is selected from cations of one or more of the following elements: al, ga, in, Y, zr, nb, sc, ti, mn and a La element; x is selected from anions containing one or more of the following elements: halogen, S, O and P. In this embodiment, a gas-phase Li source, a gas-phase X source, and a gas-phase M source are sequentially introduced into the dispersed active material, and when the gas-phase Li source, the gas-phase X source, and the gas-phase M source are in contact with the active material, chemisorption occurs on the surface of the active material and a surface reaction occurs, so that a solid state with small thickness and good uniformity can be formed on the surface of the active material An electrolyte layer.

It is understood that forming the dispersed active material may be by purging the active material particles with a shielding gas to disperse the active material and thereby form the dispersed active material. It is understood that atomic deposition may be performed in a fluidized bed reactor to form a solid electrolyte layer on the surface of the active material.

Alternatively, the shielding gas may be one or more of nitrogen, helium, neon, argon, and xenon.

In one embodiment, the dispersed active material is sequentially fed with a gas-phase Li source, a gas-phase X source, and a gas-phase M source, and then sequentially fed with a gas-phase Li source, a gas-phase X source, and a gas-phase M source is repeated. By introducing the gas-phase Li source, the gas-phase X source and the gas-phase M source for a plurality of times, the thickness of the solid electrolyte layer on the surface of the active material can be accurately controlled. For example, a gas-phase Li source, a gas-phase X source and a gas-phase M source are sequentially introduced once, and can be used as one cycle number to form a solid electrolyte layer with the thickness of 0.1nm on the surface of the active material. And then carrying out one or more times of cycle number to obtain the solid electrolyte layer meeting the required thickness.

It will be appreciated that a protective gas may be used to clean the reaction environment prior to introduction of the gas phase Li source to better coat the surface of the active material with the solid electrolyte.

In one embodiment, the temperature of the shielding gas atmosphere is 150 ℃ to 250 ℃. It is understood that in the present embodiment, the temperature of the protective gas atmosphere indicates the reaction temperature at which atomic deposition is performed. Alternatively, the temperature of the shielding gas atmosphere may be, but is not limited to, 150 ℃, 180 ℃, 200 ℃, 220 ℃, 250 ℃, and the like. It will be appreciated that the temperature of the shielding gas atmosphere may also be chosen in other suitable ways within the range of 150 c to 250 c.

In one embodiment, the reaction system is purged with a shielding gas at the gap where the gas-phase Li source, the gas-phase X source, and the gas-phase M source are sequentially introduced. The reaction system is purged by the shielding gas after each gas-phase Li source is introduced, the reaction system is purged by the shielding gas after each gas-phase X source is introduced, and the reaction system is purged by the shielding gas after each gas-phase M source is introduced. Alternatively, the time for each purge is 10s to 20s. For example, the time of each purge may be, but is not limited to, 10s, 12s, 15s, 17s, 19s, 20s, etc. It will be appreciated that the time for each purge may be chosen to be in the range 10s to 20s.

In one embodiment, the ratio of the sample introduction pulses of the gas phase Li source, the gas phase X source and the gas phase M source is a (a+3): 1. It can be understood that the sample injection pulse represents the continuous sample injection time of the material for sequential sample injection every time of sample injection. By controlling the sample injection pulse of the gas-phase Li source, the gas-phase X source and the gas-phase M source, the Li in the solid electrolyte layer can be regulated _a MX _a+3 The concentration distribution of the solid electrolyte layer forms gradient coating, so that the coating of the solid electrolyte layer can be more accurately controlled, and the solid electrolyte with better uniformity is obtained. Optionally, the sample injection pulses of the gas phase Li source, the gas phase X source, and the gas phase M source are 3s, 6s, and 1s, respectively.

It is understood that the initial states of the Li source, the X source, and the M source are in a condensed state, and when a solid electrolyte layer is formed on the surface of an active material by an atomic deposition method, the Li source, the X source, and the M source in a condensed state are vaporized to form a gas-phase Li source, a gas-phase X source, and a gas-phase M source, respectively, and then react with the surface of the active material in a gaseous state.

Optionally, the Li source is selected from one or more of alkyl lithium, lithium carboxylate, lithium alkoxide, and lithium ester. Further alternatively, the Li source is selected from one or more of methyllithium, n-butyllithium, and lithium t-butoxide. Optionally, the X source is selected from one or more of a haloalkane, a halocarboxylic acid, a halohydrin, and a haloester. Further alternatively, the X source is selected from one or more of a fluoroalkane, a fluorocarboxylic acid, a fluoroalcohol, and a fluoroester. Further alternatively, the X source is selected from fluoroethylene carbonate. Alternatively, the M source is selected from one or more of a metal alkyl, a metal carboxylate, a metal alkoxide, a metal ester.

Alternatively, the Li source has a boiling point between 70℃and 300 ℃. The boiling point of the X source is between 70 ℃ and 300 ℃. The boiling point of the M source is between 70 ℃ and 300 ℃.

In one embodiment, the method for preparing a positive electrode material further includes: a calcination treatment is performed after forming a solid electrolyte layer on the surface of the active material. The calcination treatment can remove the organic source substances and reduce the interface contact resistance between the solid electrolyte layer and the active material, so as to promote the fusion of the solid electrolyte layer and the active material. It is understood that the calcination treatment is performed under a protective gas atmosphere. Optionally, the temperature of the calcination treatment is 150 ℃ to 300 ℃. For example, the temperature of the calcination treatment may be, but is not limited to, 150 ℃, 180 ℃, 200 ℃, 220 ℃, 250 ℃, 280 ℃, 300 ℃, and the like. It will be appreciated that the temperature of the calcination treatment may be selected in other suitable ways within the range of 150 c to 300 c. Optionally, the calcination treatment is carried out for a period of 4 to 20 hours. For example, the time of the calcination treatment may be, but is not limited to, 4 hours, 8 hours, 10 hours, 15 hours, 20 hours, etc. It will be appreciated that the time of the calcination treatment may be selected within the range of 4 to 20 hours. It will be appreciated that the calcination treatment may be carried out in a tube furnace or a box furnace.

The application also provides a positive pole piece. The positive electrode plate comprises a current collector and an active layer positioned on at least one surface of the current collector; the active layer comprises the positive electrode material or the positive electrode material prepared by the preparation method of the positive electrode material.

In one embodiment, the positive electrode sheet further comprises a conductive layer, the conductive layer is located on the surface of the active layer, the conductive layer comprises a conductive polymer, a part of the conductive polymer in the conductive layer is filled in pores of the active layer, and the electronic conductivity of the conductive polymer is greater than that of the active layer. The conductive layer can form an electronic conductive network inside and on the surface of the active layer to improve the conductive performance of the positive electrode plate, and can protect the positive electrode material of the active layer, reduce the contact between the positive electrode material and the external environment, and be favorable for keeping the stability of the positive electrode material.

It can be appreciated that the active layer of the positive electrode sheet has a porosity for interacting with the electrolyte to promote wetting of the positive electrode sheet by the electrolyte. Optionally, the active layer has a porosity of 15% to 30%. Alternatively, the active layer has a porosity of 15%, 18%, 20%, 25%, 28%, 30%, etc. It is understood that the porosity of the active layer here means the porosity of the active layer before filling the conductive polymer.

It will be appreciated that the conductive layer may be located on the surface of the active layer, which may be referred to as a portion of the surface of the active layer, or may be located on the entire surface of the active layer.

In one embodiment, the mass ratio of the conductive polymer to the positive electrode material is 1 (3-8). Alternatively, the mass ratio of the conductive polymer to the positive electrode material may be, but is not limited to, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, etc. It will be appreciated that the mass ratio of the conductive polymer to the positive electrode material may be selected within the range of 1 (3-8) as well.

It will be appreciated that in conventional positive electrode sheets, in order to improve the conductivity of the positive electrode sheet, a certain amount of conductive agent is often added to the slurry of the positive electrode sheet. Through the use of conductive polymer in this application, can reduce the quantity of conductive agent in the traditional positive pole piece, improve the conductive properties of positive pole piece simultaneously.

In one embodiment, the conductive polymer has an electron conductivity of 0.1X10 ^-3 ～10×10 ^-3 S/cm. Alternatively, the conductive polymer has an electron conductivity of 0.1X10 ^-3 、0.5×10 ^-3 、1×10 ^-3 、2×10 ^-3 、5×10 ^-3 、8×10 ^-3 、10×10 ^-3 Etc.

In one embodiment, the active layer filled with the conductive polymer has a porosity of 10% to 25%. Alternatively, the active layer filled with the conductive polymer has a porosity of 10%, 12%, 15%, 18%, 20%, 22%, 25%, etc. In one embodiment, the portion of the conductive layer above the surface of the active layer has a thickness of 2 μm to 10 μm. Alternatively, the thickness of the portion of the conductive layer located above the surface of the active layer is 2 μm, 5 μm, 8 μm, 10 μm, or the like.

In one embodiment, the conductive polymer comprises at least one of polypyrrole, polyaniline, polythiophene, polyacetylene, and derivatives thereof. Optionally, the conductive polymer comprises poly 3, 4-ethylenedioxythiophene.

Alternatively, the weight average molecular weight of the conductive polymer is 2000 to 10000.

The application also provides a preparation method of the positive pole piece. The preparation method of the positive plate comprises the following steps: and transferring the slurry containing the positive electrode material or the positive electrode material prepared by the preparation method of the positive electrode material to at least one surface of a current collector, and solidifying to form an active layer on the corresponding surface of the current collector.

In one embodiment, the active layer further includes, after forming the active layer: the solution containing the conductive polymer monomer and the initiator is contacted with the surface of the active layer, and then the initiation treatment is carried out to polymerize the conductive polymer monomer into a conductive polymer, wherein the electron conductivity of the conductive polymer is greater than that of the active layer.

The conductive layer can be formed in situ on the surface of the active layer by contacting a solution comprising a conductive polymer monomer and an initiator with the surface of the active layer and then performing an initiation treatment to polymerize the conductive polymer monomer in situ into a conductive polymer. And when the solution contacts the surface of the active layer, the solution may infiltrate into the pores of the active layer, so that the conductive polymer induced to be filled in the pores of the active layer. At this time, the interface between the conductive polymer and the positive electrode material can be effectively improved, the interface impedance can be reduced, and the conductive polymer can increase the speed of oxidation-reduction reaction, alleviate the progress of interface polarization, and further improve the performance of the battery.

It is understood that the initiation treatment is a treatment with initiation conditions corresponding to the initiator. For example, the initiator may be a photoinitiator, and may be initiated by ultraviolet light irradiation, so as to polymerize the conductive polymer monomer into a conductive polymer.

In one embodiment, the conductive polymer monomer includes one or more of 3, 4-ethylenedioxythiophene, pyrrole, aniline, and acetylene.

In one embodiment, the mass ratio of initiator to conductive polymer monomer is 1 (8-15). Optionally, the mass ratio of initiator to polymer monomer is 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc.

In one embodiment, a functional aid is also included in the solution comprising the conductive polymer monomer and the initiator to improve the performance of the conductive polymer. Optionally, the functional auxiliary agent is urethane acrylate, the urethane acrylate has urethane bonds, and various hydrogen bonds can be formed among molecular chains, so that the initiation treatment is facilitated, the initiation reaction is more stable, and the obtained conductive polymer is more stable in performance.

It is understood that the solvent in the solution comprising the conductive polymer monomer and the initiator may be, but is not limited to, a siloxane.

In one embodiment, contacting the solution comprising the conductive polymer monomer and the initiator with the surface of the active layer may be transferring the solution onto the active layer of the positive electrode sheet. At this time, the inclusion solution fills part of the solution into the pores of the active layer by capillary action, and then, part of the conductive polymer fills the pores of the active layer by an initiation process.

The application also provides a secondary battery. The secondary battery comprises the positive electrode plate or the positive electrode plate prepared by the preparation method of the positive electrode plate.

The application also provides a battery module. The battery module includes the above secondary battery.

The application also provides a battery pack. The battery pack includes the secondary battery or the battery module.

The application also provides an electric device. The power utilization device includes at least one of the secondary battery, the battery module, and the battery pack.

The secondary battery will be described below with reference to the related drawings.

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 isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.

[ Positive electrode sheet ]

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, wherein the positive film layer comprises the positive active material of the first aspect of the application.

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 on a polymeric material substrate. Alternatively, the metallic material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel alloys, titanium alloys, silver, and silver alloys. Alternatively, the polymer material substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).

In some embodiments, when 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 thereof. Examples of the lithium transition metal oxide may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, modified compounds thereof, and the like. Alternatively, the lithium cobalt oxide comprises LiCoO ₂ . The lithium nickel oxide includes LiNiO ₂ . The lithium manganese oxide comprises LiMnO ₂ And LiMn ₂ O ₄ At least one of them. The lithium nickel cobalt manganese oxide comprises LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM ₃₃₃ )、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM ₅₂₃ )、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (NCM ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM ₆₂₂ ) LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM ₈₁₁ ) At least one of them. The lithium nickel cobalt aluminum oxide includes LiNi _0.85 Co _0.15 Al _0.05 O ₂ . Examples of the olivine structured lithium-containing phosphate may include, but are not limited to, at least one of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon. Optionally, the lithium iron phosphate comprises LiFePO ₄ (LFP). The lithium manganese phosphate comprises LiMnPO ₄ 。

In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material may employ a positive electrode active material for a sodium-ion battery, which is well known in the art. As an example, the positive electrode active material may be used alone, or two or more kinds may be combined. Wherein the positive electrode active material is selected from sodium-iron composite oxide, sodium-cobalt composite oxide, sodium-chromium composite oxide, sodium-manganese composite oxide, sodium-nickel-titanium composite oxide, sodium-nickel-manganese composite oxide, sodium-iron-manganese composite oxide, sodium-nickel-cobalt-manganese composite oxide, sodium-iron-phosphate compound, sodium-manganese-phosphate compound, sodium-cobalt-phosphate compound, prussian blue material, polyanion material, etcThe present application is not limited to these materials, and other conventionally known materials that can be used as a positive electrode active material of a sodium ion battery may be used. Alternatively, the sodium iron composite oxide includes NaFeO ₂ . The sodium cobalt composite oxide comprises NaCoO ₂ . The sodium-chromium composite oxide comprises NaCrO ₂ . The sodium-manganese composite oxide comprises NaMnO ₂ . The sodium-nickel composite oxide comprises NaNiO ₂ . The sodium nickel titanium composite oxide comprises NaNi _1/2 Ti _1/2 O ₂ . The sodium nickel manganese composite oxide comprises NaNi _1/2 Mn _1/2 O ₂ . The Na-Fe-Mn composite oxide comprises Na _2/3 Fe _1/3 Mn _2/3 O ₂ . The sodium nickel cobalt manganese composite oxide comprises NaNi _1/3 Co _1/3 Mn _1/3 O ₂ . The sodium iron phosphate compound comprises NaFePO ₄ . The sodium manganese phosphate compound comprises NaMnPO ₄ . Sodium cobalt phosphate compounds include NaCoPO ₄ . The polyanionic material includes at least one of phosphate, fluorophosphate, pyrophosphate, and sulfate.

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 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. Alternatively, the solvent comprises N-methylpyrrolidone.

[ negative electrode sheet ]

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. The negative electrode tab may be the negative electrode tab described above.

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 on a polymeric material substrate. Optionally, the metallic material comprises at least one of copper, copper alloy, nickel alloy, titanium alloy, silver, and silver alloy. The polymer material comprises at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and Polyethylene (PE).

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), carboxymethyl chitosan (CMCS), polyamideimide (PAI), polyethylenimine (PEI), polyimide (PI), and poly-t-butyl acrylate-triethoxyvinylsilane (TBATEVS).

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 also optionally include other adjuvants, such as thickening agents. Optionally, the thickener comprises sodium carboxymethylcellulose (CMC-Na).

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 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. Optionally, the solvent comprises deionized water.

[ electrolyte ]

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

In some embodiments, 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.

[ isolation Membrane ]

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

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

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte as 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. 1 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 2, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and 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 tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating 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. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be 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. 4 and 5 are battery packs 1 as an example. Referring to fig. 4 and 5, 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 power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, and the like. For example, mobile devices include cell phones, notebook computers, and the like. Electric vehicles include all-electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, 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. 6 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

Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

In the following examples and comparative examples, the weight average molecular weight of the poly 3, 4-ethylenedioxythiophene was 2000 to 10000, the weight average molecular weight of the polypyrrole was 2000 to 10000, the weight average molecular weight of the polyaniline was 2000 to 10000, and the weight average molecular weight of the polyacetylene was 2000 to 10000.

Example 1

(1) And (3) preparing a positive electrode material.

(1) LiFePO as positive electrode active material ₄ Placing the powder into a fluidized bed reactor, vacuumizing a reaction chamber, introducing argon gas for atmosphere purging, and controlling the gas flow rate to enable LiFePO ₄ The powder can be dispersed. LiFePO ₄ The electrochemical window of the powder is 2.5V-3.7V.

(2) To dispersed LiFePO under 200 ℃ argon atmosphere ₄ Sequentially introducing gas-phase lithium tert-butoxide, gas-phase fluoroethylene carbonate and gas-phase triethyl indium into the powder to complete one-time circulation, and obtaining the product in LiFePO ₄ The chemical composition of the surface of the powder is Li ₃ InF ₆ The thickness of the solid electrolyte layer formed in one cycle was 0.1nm. Wherein, the sample injection pulse of the gas phase tertiary butyl alcohol lithium, the gas phase fluoroethylene carbonate and the gas phase triethyl indium is respectively 3s, 6s and 1s. After each sample injection was completed, the reaction chamber was purged with argon for 15 seconds.

(3) And (5) performing multiple times of circulation to form a solid electrolyte layer with corresponding thickness. The thickness of the solid electrolyte layer in this example was 2nm, i.e., 20 cycles were performed.

(4) In LiFePO ₄ After forming a solid electrolyte layer on the surface of the powder, calcination treatment was performed under an argon atmosphere. The temperature of the calcination treatment is 260 ℃ and the time of the calcination treatment is 10 hours. After calcination, cooling was performed to obtain the positive electrode material in this example.

(2) And (3) preparing a positive electrode plate.

(1) The weight ratio of the positive electrode material to the binder polyvinylidene fluoride (PVDF) in the embodiment is 95:5, stirring and mixing uniformly to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector, and then drying, cold pressing and cutting to obtain a positive electrode plate preform with an active layer.

(2) Adding siloxane into 3, 4-ethylenedioxythiophene, and then adding polyurethane acrylate, wherein the mass ratio of the siloxane to the 3, 4-ethylenedioxythiophene to the polyurethane acrylate is 18:1:5. then adding a photoinitiator 2-hydroxy-2-methyl-phenyl acetone, wherein the mass ratio of the photoinitiator to 3, 4-ethylenedioxythiophene is 1:10. and pouring the solution on an active layer of the positive electrode plate preform, allowing the solution to permeate into pores of the active layer through capillary force, and then irradiating ultraviolet light for about 8s to solidify to form a conductive polymer, wherein part of the conductive polymer is positioned on the surface of the active layer, and part of the conductive polymer forms a conductive network in the pores of the active layer to obtain the positive electrode plate. Wherein the mass ratio of the conductive polymer to the positive electrode material is 1:18.

(2) And (3) preparing a negative electrode plate.

Artificial graphite as a cathode active material, carbon black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder according to the weight ratio of 96.0:2.0:2.0, dissolving in deionized water serving as a solvent, and uniformly mixing to prepare negative electrode slurry; and uniformly coating the negative electrode slurry on a negative electrode current collector copper foil once or a plurality of times, and drying, cold pressing and cutting to obtain a negative electrode plate.

(3) And (3) preparing an electrolyte.

In an argon atmosphere glove box, H in the glove box ₂ O<0.1ppm，O ₂ <0.1ppm, mixing organic solvent Ethylene Carbonate (EC)/methyl ethyl carbonate (EMC) uniformly according to volume ratio of 3/7, adding 12.5% LiPF ₆ And dissolving lithium salt in an organic solvent, and uniformly stirring to obtain the electrolyte.

(4) A polypropylene film was used as a separator.

(5) And (3) preparing a lithium ion battery.

And placing the negative electrode shell, the negative electrode plate, the isolating film and the positive electrode plate, the gasket, the elastic sheet and the positive electrode shell in sequence, dropwise adding 120uL of electrolyte in the placing process, compacting and standing for 2 hours to obtain the lithium ion battery.

Examples 2 to 23

Examples 2 to 23 are different from example 1 in the material and thickness of the solid electrolyte layer, the conductive polymer and the amount used, and the material and thickness of the solid electrolyte layer, the conductive polymer and the amount used in examples 2 to 23 are shown in table 1.

Wherein, in examples 2 and 3, the M source was yttrium tris (2, 6-tetramethyl-3, 5-heptanedionato) and scandium acetate, respectively.

In example 13, the positive electrode sheet (2) is: the concentration of ammonium persulfate solution is 0.63g/ml, and the solution is prepared by adding ethanol with the same volume and hydrochloric acid with one tenth of the volume, wherein the volume ratio of pyrrole to benzene is 1:3 as monomer solution, the volume ratio of the monomer solution to the initiating system solution is 4:1. and (3) adding an initiating system after uniformly stirring the monomer solution, pouring the monomer solution on an active layer of the positive electrode plate preform, and performing in-situ polymerization and solidification.

In example 14, the positive electrode sheet (2) is as follows: ammonium persulfate is taken as an oxidant, the molar ratio of the ammonium persulfate to the aniline monomer is 1.0, an ammonium persulfate initiation system solution is added into the aniline monomer solution, and the mixture is poured onto an active layer of the positive pole piece preform to perform in-situ polymerization and solidification. Wherein the ratio of the initiation system was the same as in example 13.

In example 15, the positive electrode sheet (2) is: catalytic synthesis using Ti (OBu) 4-Al Et3 system, nd (P) ₅₀₇ ) Mixing n-butanol, adding Al (C) ₂ H ₅ ) ₃ N-butanol: nd: al is 4:1: and 6, pouring hydrogenated gasoline serving as a solvent on an active layer of the positive electrode plate preform, and performing in-situ polymerization and solidification.

Comparative example 1

Compared with example 1, the comparative example is different in that the positive electrode sheet is prepared by the following steps:

the positive electrode material, a binder polyvinylidene fluoride (PVDF) and a conductive polymer poly-3, 4-ethylenedioxythiophene are mixed according to the weight ratio of 90:5:5, mixing, dispersing in NMP, stirring and mixing uniformly to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector, and then drying, cold pressing and cutting to obtain a positive electrode plate.

Comparative example 2

The present comparative example is different from example 1 in that the positive electrode material is an active material whose surface does not form a solid electrolyte layer.

Comparative example 3

The present comparative example is different from example 1 in that the positive electrode sheet does not incorporate a conductive polymer.

Comparative example 4

The present comparative example is different from example 1 in that the positive electrode material is an active material whose surface does not form a solid electrolyte layer, and the positive electrode sheet does not incorporate a conductive polymer.

Comparative example 5

The present comparative example is different from example 1 in that the thickness of the solid electrolyte layer is 0.2nm.

Comparative example 6

The present comparative example is different from example 1 in that the thickness of the solid electrolyte layer is 10nm.

Comparative example 7

The present comparative example is different from example 1 in that the mass ratio of the conductive polymer to the positive electrode material is 1:2.

Comparative example 8

The present comparative example is different from example 1 in that the mass ratio of the conductive polymer to the positive electrode material is 1:9.

Test case

Battery capacity retention test: the batteries corresponding to the examples and comparative examples were charged to 4.5V at a constant current of 1/3C, charged to 0.05C at a constant voltage of 4.5V, left for 5min, discharged to 2.8V at 1/3C, and the resulting capacity was designated as initial capacity C ₀ . Repeating the above steps, and simultaneously recording the discharge capacity C of the battery after the nth cycle _n Battery capacity retention rate P after each cycle _n ＝C _n /C ₀ *100%. Capacity retention of the cell after 100 test cycles, i.e. P ₁₀₀ Is a value of (2). The test results are shown in Table 1.

Testing the alternating current impedance of the battery: the positive electrode sheet, the separator and the electrolyte 120uL in the examples and the comparative examples are assembled into a symmetrical battery of positive electrode, and the symmetrical battery is kept stand in an incubator at 25 ℃ for 2 hours to ensure the infiltration of the electrolyte. The alternating current impedance test adopts an electrochemical workstation impedance test module, a voltage disturbance mode PEIS, a disturbance voltage of 5mV, a frequency range of 200 kHZ-30 mHZ, a voltage range of 0-5V and voltage protection of 0-5V, and impedance spectrum is drawn by using the negative number of the imaginary part of impedance as an ordinate and the real part as an abscissa.

Impedance test data fitting: the impedance data of the examples and the comparative examples are subjected to data fitting by adopting Z-fit software, and a fitting circuit is selected as R _s +C ₁ /R _SEI +C ₂ /R _ct +W, where R is _s Is ohmic impedance, is mainly related to the conductivity of the positive electrode material, R _ct Is charge transfer impedance, and mainly reflects the deintercalation rate of lithium ions in the anode material. The judgment basis of fitting requires: error less than 5%, and the intersection point with the real part should be fitted to obtain R _s Deviation of (2)<5%. Fitting results meeting the above requirements can be selectively accepted, and R in the fitting results is selected _ct And R is R _s Extracted and recorded in table 1.

Porosity test: the archimedes principle-gas expansion displacement method is adopted, small molecular inert gas is used as a medium, and an ideal gas state equation is adopted: pv=nrt calculates the volume of gas displaced by the sample in the test chamber, thus accurately measuring the true volume of the sample, porosity= (V1-V2)/V1 x 100%, V1: apparent volume of sample, V2: real volume of sample. Wherein the small molecular inert gas is He or N ₂ . The true volume of the sample contains the volume of closed cells.

Electron conductivity test: the overall resistivity of the pole piece is directly measured by adopting a two-probe method, wherein the conductivity=l/(r×a), L is the thickness, R is the resistance, and a is the contact area.

TABLE 1

As can be seen from table 1, the incorporation of the solid electrolyte layer and/or the conductive polymer can provide a battery with a higher capacity retention rate.

Specifically, as can be seen from example 1 and comparative examples 2 to 6, the battery corresponding to the positive electrode material having the solid electrolyte layer of a suitable thickness has a higher capacity retention rate. As can be seen from example 1 and comparative examples 7 to 8, the appropriate amount of the conductive polymer is advantageous in improving the capacity retention rate of the battery.

The conductive polymer in example 1 was cured in situ in the positive electrode sheet, and the conductive polymer in comparative example 1 was directly added to the positive electrode slurry. As can be seen from example 1 and comparative example 1, the in-situ cured battery obtained has a higher capacity retention rate.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. A positive electrode material characterized by comprising an active material and a solid electrolyte layer coated on the surface of the active material; the electrochemical window of the solid electrolyte layer is larger than the electrochemical window of the active material.

2. The positive electrode material of claim 1, wherein the solid state electrolyte layer satisfies one or more of the following characteristics:

(1) The electrochemical window of the solid electrolyte layer is more than or equal to 5V;

(2) The thickness of the solid electrolyte layer is 0.5 nm-5 nm;

optionally, the thickness of the solid electrolyte layer is 1 nm-2 nm;

(3) The lithium ion conductivity of the solid electrolyte layer is more than or equal to 0.8X10 ^-4 S/cm；

(4) The solid electrolyte layer comprises a chemical composition of Li _a MX _a+3 Wherein 1.ltoreq.a.ltoreq.6, M is selected from cations of one or more of the following elements: al, ga, in, Y, zr, nb, sc, ti, mn and a La element; x is selected from anions containing one or more of the following elements: halogen, S, O and P;

alternatively, M is a +3 valent cation;

alternatively, M comprises Al ³⁺ 、Ga ³⁺ 、In ³⁺ 、Y ³⁺ 、Zr ³⁺ 、Nb ³⁺ 、Sc ³⁺ 、Ti ³⁺ 、Mn ³⁺ 、Er ³⁺ 、Tb ³⁺ 、Yb ³⁺ 、Lu ³⁺ 、La ³⁺ Ho ³⁺ One or more of the following;

alternatively, X comprises F ^- 、Cl ^- 、Br ^- 、I ^- 、S ^2- 、O ^2- PO (Positive and negative) ₄ ^- One or more of the following;

optionally, the solid electrolyte layer comprises Li ₃ InF ₆ 、Li ₃ YF ₆ 、Li ₃ ScF ₆ 、Li ₃ MnF ₆ 、Li ₃ ZrF ₆ 、Li ₃ YF ₆ 、Li ₃ InCl ₆ 、Li ₃ YCl ₆ 、Li ₃ ScCl ₆ 、Li ₃ MnCl ₆ 、Li ₃ ZrCl ₆ Li (lithium ion battery) ₃ YCl ₆ At least one of them.

3. The preparation method of the positive electrode material is characterized by comprising the following steps:

forming a solid electrolyte layer on the surface of the active material; wherein the electrochemical window of the solid electrolyte layer > the electrochemical window of the active material.

4. The method for producing a positive electrode material according to claim 3, wherein a solid electrolyte layer is formed on the surface of the active material by an atomic deposition method;

optionally, forming the solid electrolyte layer on the surface of the active material includes the steps of:

sequentially introducing a gas-phase Li source, a gas-phase X source and a gas-phase M source into the dispersed active material in a protective gas atmosphere, and forming a chemical composition of Li on the surface of the active material _a MX _a+3 Wherein 1.ltoreq.a.ltoreq.6, M is selected from cations of one or more of the following elements: al, ga, in, Y, zr, nb, sc, ti, mn and a La element; x is selected from anions containing one or more of the following elements: halogen, S, O and P.

5. The method for producing a positive electrode material according to claim 4, wherein forming a solid electrolyte layer on the surface of the active material satisfies one or more of the following characteristics:

(1) The temperature of the protective gas atmosphere is 150-250 ℃;

(2) Sequentially introducing gaps of a gas-phase Li source, a gas-phase X source and a gas-phase M source, and purging a reaction system through protective gas;

optionally, the time of each purging is 10-20 s;

(3) The ratio of the sample injection pulses of the gas-phase Li source, the gas-phase X source and the gas-phase M source is a (a+3): 1.

6. The method for producing a positive electrode material according to any one of claims 3 to 5, characterized by further comprising:

performing calcination treatment after forming a solid electrolyte layer on the surface of the active material;

optionally, the temperature of the calcination treatment is 150-300 ℃;

optionally, the calcination treatment is performed for 4 to 20 hours.

7. A positive electrode sheet comprising a current collector and an active layer on at least one surface of the current collector; the active layer includes the positive electrode material according to any one of claims 1 to 2 or the positive electrode material prepared by the method for preparing a positive electrode material according to any one of claims 3 to 6.

8. The positive electrode tab of claim 7 further comprising a conductive layer comprising a conductive polymer, the conductive layer being located on a surface of the active layer and a portion of the conductive polymer in the conductive layer filling the pores of the active layer, the conductive polymer having an electronic conductivity greater than an electronic conductivity of the active layer.

9. The positive electrode sheet of claim 8, wherein the positive electrode sheet meets one or more of the following characteristics:

(1) The mass ratio of the conductive polymer to the positive electrode material is 1 (3-8);

(2) The electron conductivity of the conductive polymer is 0.1X10 ^-3 ～10×10 ^-3 S/cm；

(3) The porosity of the active layer filled with the conductive polymer is 10% -25%;

(4) The thickness of the portion of the conductive layer located above the surface of the active layer is 2 μm to 10 μm;

(5) The conductive polymer includes at least one of polypyrrole, polyaniline, polythiophene, polyacetylene, and derivatives thereof.

10. The preparation method of the positive plate is characterized by comprising the following steps:

a slurry containing the positive electrode material according to any one of claims 1 to 2 or the positive electrode material prepared by the method for preparing a positive electrode material according to any one of claims 3 to 6 is transferred to at least one surface of a current collector and cured, and an active layer is formed on the corresponding surface of the current collector.

11. The method of manufacturing a positive electrode sheet according to claim 10, further comprising, after forming the active layer:

and contacting a solution containing a conductive polymer monomer and an initiator with the surface of the active layer, and then performing an initiation treatment to polymerize the conductive polymer monomer into a conductive polymer, wherein the electron conductivity of the conductive polymer is greater than that of the active layer.

12. A secondary battery comprising the positive electrode sheet according to any one of claims 7 to 9 or the positive electrode sheet produced by the method for producing a positive electrode sheet according to any one of claims 10 to 11.

13. A battery module comprising the secondary battery according to claim 12.

14. A battery pack comprising the secondary battery according to claim 12 or the battery module according to claim 13.

15. An electric device comprising at least one of the secondary battery according to claim 12, the battery module according to claim 13, and the battery pack according to claim 14.