CN117143287B

CN117143287B - Sulfur-containing polymer, preparation method, negative electrode plate, secondary battery and electricity utilization device

Info

Publication number: CN117143287B
Application number: CN202311410427.4A
Authority: CN
Inventors: 吴凯; 孟阵; 魏冠杰; 赵延杰; 古力; 石鹏; 林江辉; 张帆; 宋育倩; 李星
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-10-27
Filing date: 2023-10-27
Publication date: 2024-04-09
Anticipated expiration: 2043-10-27
Also published as: CN117143287A

Abstract

The application provides a sulfur-containing polymer, a preparation method, a negative electrode plate, a secondary battery and an electric device. The side chains of the sulfur-containing polymer include polysulfide linkages containing at least three sulfur atoms. The sulfur-containing polymer can improve the stability and ion conductivity of the solid electrolyte membrane on the surface of the negative electrode, thereby reducing the internal resistance of the battery and improving the cycling stability of the battery.

Description

Sulfur-containing polymer, preparation method, negative electrode plate, secondary battery and electricity utilization device

Technical Field

The application relates to the technical field of secondary batteries, in particular to a sulfur-containing polymer, a preparation method, a negative electrode plate, a secondary battery and an electric device.

Background

In recent years, secondary batteries are widely used in energy storage power supply systems such as hydraulic power, thermal power, wind power and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace, and the like. With the popularization of secondary battery applications, higher demands are also being made on its cycle stability, service life, etc.

Improving the stability of a solid electrolyte film (SEI film) on the surface of a negative electrode is an effective means for improving the cycle stability of a secondary battery, however, film forming additives in the prior art have low film forming efficiency and poor effect.

Disclosure of Invention

The present application has been made in view of the above problems, and an object thereof is to provide a sulfur-containing polymer capable of improving the stability of an SEI film and the ionic conductivity, and further reducing the internal resistance of a battery and improving the cycle stability of the battery.

A first aspect of the present application provides a sulfur-containing polymer comprising polysulfide linkages in the side chains of the sulfur-containing polymer comprising at least three sulfur atoms.

In the secondary battery cycle process, polysulfide bonds in the side chains of the sulfur-containing polymer are reduced, so that the polysulfide bonds are broken, sulfide salts such as lithium sulfide are generated with active ions, the sulfide salts are easy to migrate to the surface of a negative electrode, inorganic components in the SEI film on the surface of the negative electrode are formed, the stability and the ionic conductivity of the SEI film are improved, the impedance of the battery is reduced, and the stability of the SEI film is improved. Meanwhile, the breaking of the polysulfide bond positioned on the side chain of the sulfur-containing polymer does not affect the main chain structure, so that the structure and the performance of the main chain of the sulfur-containing polymer are not affected, and the benefit can be further improved. In addition, the side chains of the sulfur-containing polymer comprise polysulfide bonds, so that the negative influence on a battery caused by adding the film forming agent in a small molecular form can be reduced, the adding amount is increased, and the formed SEI film is more compact.

In any embodiment, the polysulfide linkage comprises from 3 to 8 sulfur atoms.

The polysulfide bond containing 3-8 sulfur atoms can not only enable the sulfur-containing polymer to generate sulfur bond breakage in the circulating process to generate sulfide salt, but also reduce unstable decomposition of the sulfur-containing polymer caused by excessive sulfur, thereby comprehensively improving the circulating stability of the battery.

In any embodiment, the sulfur-containing polymer comprises structural units of formula I,

i is a kind of

Wherein R is ₁ 、R ₂ 、R ₃ Each independently comprises hydrogen, substituted or unsubstituted C _1-6 At least one of alkyl groups; r is R ₄ Comprises at least one of single bond, alkyl, ester, amino, amido, carbonyl, ketone and aromatic groups; r is R ₅ Comprises at least one of hydrogen, alkyl, ester, amino, amido, carbonyl, ketone and aromatic groups; x is more than or equal to 3 and less than or equal to 8.

The sulfur-containing polymer of the structural unit shown in the formula I can play a role of a film forming agent, generate an SEI film containing a large amount of sulfide salt, reduce the impedance of the secondary battery and improve the cycle stability of the secondary battery.

In any embodiment, the sulfur-containing polymer comprises structural units of formula II,

II (II)

Wherein m is more than or equal to 1 and less than 10 ⁷ 。

The sulfur-containing polymer comprising the structural unit shown in the formula II can provide certain binding force, so that the sulfur-containing polymer can also play a role of a binder, and the stability of the negative electrode plate in the circulating process is maintained.

In any embodiment, the ratio of the degree of polymerization m of the structural unit derived from butadiene in the structural unit of formula II to the degree of polymerization n of the structural unit of formula II in the sulfur-containing polymer is not less than 1, optionally 1 to 10.

The ratio of the polymerization degree m of the structural unit derived from butadiene in the structural unit shown in the formula II to the polymerization degree n of the structural unit shown in the formula II in the sulfur-containing polymer is not less than 1, so that the sulfur-containing polymer has a certain cohesive force. The ratio of the polymerization degree m of the structural unit derived from butadiene in the structural unit shown in the formula II to the polymerization degree n of the structural unit shown in the formula II in the sulfur-containing polymer is not more than 10, so that the sulfur-containing polymer has better dispersibility and can improve the uniformity and the processability of slurry.

In any embodiment, the molar ratio of structural units of formula II to structural units of formula I in the sulfur-containing polymer is from 1 to 5, alternatively from 2 to 4.

The molar ratio of the structural unit shown in the formula II to the structural unit shown in the formula I of the sulfur-containing polymer is 1-5, so that the sulfur-containing polymer can reduce the impedance of a battery and improve the cycling stability of the battery. The molar ratio of the structural unit shown in the formula II to the structural unit shown in the formula I of the sulfur-containing polymer is 2-4, so that the adhesive force of the pole piece and the impedance of the battery can be balanced, and the cycling stability of the battery is further improved.

In any embodiment, the structural unit of formula I is of formula III,

formula III

Wherein Ra comprises hydrogen, C _1-4 Hydrocarbyl, phenolic, C _1-5 Ester group, amine group, C _1-5 Amide, carbonyl, C _1-5 At least one of ketone group, halogen, nitro group; x is more than or equal to 3 and less than or equal to 8.

The structural unit has good structural stability in the battery processing process, is not easy to decompose, and can break polysulfide bonds to generate sulfide salt in the circulating process, so that the stability and ionic conductivity of the SEI film are improved, the impedance of the secondary battery is reduced, and the circulating stability is improved.

In any embodiment, ra comprises hydrogen, C _1-4 At least one of alkyl groups, x is more than or equal to 3 and less than or equal to 5.

The sulfur-containing polymer in the above range has better structural stability and adhesion.

In any embodiment, the sulfur-containing polymer has a weight average molecular weight of 1X 10 ⁴ -1×10 ⁹ Alternatively 1X 10 ⁶ -1×10 ⁷ 。

In any embodiment, the sulfur-containing polymer comprises a structure represented by formula X,

x is a metal alloy

Wherein Ra comprises hydrogen, C _1-4 At least one of hydrocarbon radicals, m is more than or equal to 1 and less than 10 ⁷ ，1≤n＜10 ⁷ ，1≤p＜10 ⁷ ，3≤x≤8，1≤n/p≤5。

The sulfur-containing polymer can be used for combining the adhesive property and the film forming property, and is beneficial to realizing the reduction of the impedance of the secondary battery and the improvement of the cycle stability.

A second aspect of the present application provides the use of a sulfur-containing polymer as a binder for a secondary battery.

A third aspect of the present application provides a method for producing a sulfur-containing polymer, comprising polymerizing a polymerizable monomer with an unsaturated monomer containing a polysulfide linkage under polymerizable conditions to produce a sulfur-containing polymer comprising a polysulfide linkage of at least three sulfur atoms in a side chain of the sulfur-containing polymer.

The sulfur-containing polymer prepared by the preparation method can improve the stability and ion conductivity of the solid electrolyte membrane on the surface of the negative electrode, thereby reducing the internal resistance of the battery and improving the cycling stability of the battery.

In any embodiment, the unsaturated monomer comprising a polysulfide linkage comprises a monomer of formula IV,

IV (IV)

Wherein Ra comprises at least one of hydrogen, hydrocarbyl, phenolic, ester, amine, amide, carbonyl, ketone; x is more than or equal to 3 and less than or equal to 8.

The monomer can polymerize polysulfide bond into polymer through simple copolymerization, has simple reaction and is easy to popularize.

In any embodiment, the polymerizable monomers include styrene and butadiene.

The monomer can provide certain cohesive force and improve the cohesive property of the polymer.

In any embodiment, the polymerization reaction system further comprises an initiator and a chain transfer agent, optionally, the initiator comprises an azo initiator, and the chain transfer agent comprises a reversible addition-fragmentation chain transfer agent.

The reagent can realize controllable polymerization, so that the molecular weight distribution of the product is narrower and the consistency is higher.

In any embodiment, the method of making further comprises the steps of:

the monomer shown in the formula V and the acrylic chloride are subjected to a first reaction to prepare a monomer shown in the formula IV,

v (V)

In any embodiment, the reaction system of the first reaction further comprises a first pH adjuster comprising an organic amine.

In the first reaction, the monomer shown in the formula V reacts with the acryloyl chloride to generate the monomer shown in the formula IV and hydrogen chloride, and the addition of the organic amine can tie up the hydrogen chloride to play a role of a pH regulator.

In any embodiment, the method of making further comprises the steps of:

mixing monomer shown in formula VI, p-thiol phenol and S _x1 Cl ₂ A second reaction is carried out to prepare the monomer shown in the formula V,

VI (VI)

Wherein Ra comprises at least one of hydrogen, hydrocarbyl, phenolic, ester, amine, amide, carbonyl, ketone; x1 is more than or equal to 1 and less than or equal to 6.

In any embodiment, the reaction system of the second reaction further comprises a solvent and a second pH regulator, optionally, the second pH regulator comprises pyridine.

In the second reaction, a monomer of formula VI, p-thiol phenol and S _x1 Cl ₂ The reaction generates hydrogen chloride, and the second pH regulator can play a role in absorbing the hydrogen chloride and keep the pH value stable.

A fourth aspect of the present application provides a negative electrode tab comprising a negative electrode film layer comprising a binder comprising the sulfur-containing polymer of any embodiment or the sulfur-containing polymer prepared by the method of any embodiment.

The sulfur-containing polymer is used as a binder, so that the binder and the film forming agent can be simultaneously exerted, the additive content of the auxiliary agent is reduced, and the load capacity of the negative electrode plate is improved.

In any embodiment, the binder is present in an amount of 0.1% to 50%, alternatively 1% to 5%, by mass based on the total mass of the negative electrode film layer.

A fifth aspect of the present application provides a secondary battery comprising the negative electrode tab of any of the embodiments.

A sixth aspect of the present application provides an electric device comprising the secondary battery of any of the embodiments.

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 one 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, upper box body; 3, lower box body; 4, a battery module; 5 a secondary battery; 51 a housing; 52 electrode assembly; 53 cover plates.

Detailed Description

Hereinafter, embodiments of the sulfur-containing polymer, the production method, the negative electrode tab, the secondary battery, and the electric device of the present application are specifically disclosed with reference to the 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 present).

In order to improve the cycle stability of the battery, a small-molecule film forming agent is often added to the electrolyte to improve the stability of the negative electrode SEI film. However, the film forming agent in the electrolyte has poor film forming uniformity on the surface of the negative electrode, and the components of the film forming agent tend to reduce the conductivity of active ions. In addition, because the film forming agent in the electrolyte has limited addition content, the formed SEI film is not compact.

[ Sulfur-containing Polymer ]

Based on this, the present application proposes a sulfur-containing polymer comprising polysulfide bonds containing at least three sulfur atoms in the side chains of the sulfur-containing polymer.

Herein, the sulfur-containing polymer means a polymer including elemental sulfur.

In this context, a polymer includes, on the one hand, an aggregate of chemically homogeneous macromolecules prepared by polymerization, but differing in terms of degree of polymerization, molar mass and chain length; on the other hand, derivatives of such macromolecular assemblies formed by polymerization reactions, i.e. polymers which can be obtained by reaction of functional groups in the macromolecules described above, for example by addition or substitution, and which can be chemically homogeneous or chemically heterogeneous, are also included.

The side chain in the polymer is opposite to the main chain, the main chain is a chain structure formed by connecting repeated structural units in a molecular chain through covalent bonds, the side chain is connected to the main chain through chemical bonds, and the main chain of the polymer cannot be broken due to the breaking of the chemical bonds in the side chain.

In this context, polysulfide bond refers to a chemical bond formed by the joining of at least two sulfur groups.

In this context, the polysulfide linkage containing at least three sulfur atoms has the structure: s- (S) _n S-, wherein n is 1 or more.

The reaction process mechanism is as follows:

wherein,is a sulfur-containing polymer backbone, R ₁ 、R ₂ Is an organic group, and n is an integer not less than 1.

In some embodiments, the polysulfide linkage comprises 3 to 8 sulfur atoms.

In some embodiments, the polysulfide linkage comprises 3, 4, 5, 6, 7, or 8 sulfur atoms.

The polysulfide bond containing 3-8 sulfur atoms can not only enable the sulfur-containing polymer to generate sulfur bond breakage in the circulation process to generate sulfide salt, but also reduce unstable decomposition of the sulfur-containing polymer caused by excessive sulfur and increase of battery impedance, comprehensively reduce the impedance of the battery and improve the circulation stability of the battery.

In some embodiments, the sulfur-containing polymer comprises structural units of formula I,

i is a kind of

In some embodiments, R ₄ Is a single bond, and sulfur is directly connected with carbon on the main chain.

Hydrocarbyl refers to the radical remaining after removal of one or more hydrogen atoms in the hydrocarbon molecule and includes, by way of example, but is not limited to, alkyl, alkylene, alkenyl, alkenylene, and the like. Alkylene means having the general formula-C _n H _2n -a divalent hydrocarbon group. The divalent hydrocarbon group may be unbranched or branched. Which includes, for example, 1, 2-ethylene, 1, 2-propylene, 1, 3-butylene, 1, 4-butylene, 2-methyl-1, 3-propylene, 1-dimethyl-1, 2-ethylene, 1,4-pentylene, 1, 5-pentylene, 2-methyl-1, 4-butylene, 2-dimethyl-1, 3-propylene, 1, 6-hexylene, 2-methyl-1, 5-pentylene, 3-methyl-1, 5-pentylene, 2, 3-dimethyl-1, 4-butylene, and the like. Alkenylene refers to a divalent hydrocarbon radical having at least one double bond in the backbone, which may be unbranched or branched. These include, for example, ethenylene, propenylene, 1-methylethenylene, 1-butenylene, 2-butenylene, 1-methylpropenylene, 2-methylpropenylene, 1-pentenylene, 2-pentenylene, 1-methyl-1-butenylene, 1-methyl-2-butenylene, 1-hexenylene, and the like.

An ester group refers to an organic group that includes a-COO-bond.

Amine group refers to an organic group comprising an-N-bond.

Amide groups refer to organic groups that include-CON-.

Carbonyl refers to an organic group comprising-CO-.

Keto refers to the-CO-organic group linking two C's.

An aryl group refers to an organic group derived from the removal of one or more hydrogen atoms from a monocyclic or polycyclic aromatic hydrocarbon, which includes, but is not limited to including, phenyl, naphthyl, benzyl, and the like.

The sulfur-containing polymer comprising the structural unit shown in the formula I can play a role of a film forming agent, generate an SEI film containing a large amount of sulfide salt, reduce the impedance of the secondary battery and improve the cycle stability of the secondary battery.

In some embodiments, the sulfur-containing polymer comprises structural units of formula II,

II (II)

Wherein m is more than or equal to 1 and less than 10 ⁷ 。

In some embodiments, m can be selected from 1, 10 ² 、10 ³ 、10 ⁴ 、10 ⁵ 、10 ⁶ 、10 ⁷ Or any numerical range therebetween.

In some embodiments, the ratio of the degree of polymerization m of the structural unit derived from butadiene in the structural unit of formula II to the degree of polymerization n of the structural unit of formula II in the sulfur-containing polymer is not less than 1, optionally 1 to 10.

In some embodiments, the ratio of the degree of polymerization m of the structural unit of formula II derived from butadiene to the degree of polymerization n of the structural unit of formula II in the sulfur-containing polymer can be selected to be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any number therebetween.

In some embodiments, the ratio of the polymerization degree m of the structural unit derived from butadiene in the structural unit shown in formula II to the polymerization degree n of the structural unit shown in formula II in the sulfur-containing polymer is not less than 1, so that the sulfur-containing polymer has a certain cohesive force, and in some embodiments, the ratio of the polymerization degree m of the structural unit derived from butadiene in the structural unit shown in formula II to the polymerization degree n of the structural unit shown in formula II in the sulfur-containing polymer is not more than 10, so that the sulfur-containing polymer has better dispersibility and can improve the uniformity and the processability of the slurry.

In some embodiments, the molar ratio of structural units of formula II to structural units of formula I in the sulfur-containing polymer is from 1 to 5, alternatively from 2 to 4.

In some embodiments, the molar ratio of the structural unit of formula II to the structural unit of formula I in the sulfur-containing polymer may be selected to be 1, 2, 3, 4, 5, or any number therebetween.

In some embodiments, the structural unit of formula I is of formula III,

formula III

C _1-4 Hydrocarbyl refers to hydrocarbyl groups comprising 1 to 4 carbon atoms. C (C) _1-5 The ester group means an ester group comprising 1 to 5 carbon atoms. C (C) _1-5 An amide group refers to an amide group comprising 1 to 5 carbon atoms. C (C) _1-5 Keto refers to a ketone group comprising 1 to 5 carbon atoms. Halogen includes any one of fluorine, chlorine, bromine and iodine.

In some embodiments, x may be selected from 3, 4, 5, 6, 7, 8, or any number therebetween.

In some embodiments, ra comprises hydrogen, C _1-4 At least one of alkyl groups, x is more than or equal to 3 and less than or equal to 5.

In some embodiments, ra comprises any of hydrogen, methyl, ethyl, propyl, isopropyl, 2-methyl-1-propyl, 2-methyl-2-propyl.

In some embodiments, the sulfur-containing polymer has a weight average molecular weight of 1×10 ⁴ -1×10 ⁹ Optionally 1X 10 ⁶ -1×10 ⁷ 。

In this application, the weight average molecular weight of the sulfur-containing polymer may be tested by methods known in the art, such as by gel chromatography, e.g., by Waters 2695 Isocric HPLC-type gel chromatograph (differential refractive detector 2141). A sample of 3.0% by mass polystyrene solution was used as a reference and a matched column (oiliness: styragel HT5 DMF 7.8X 300mm+Styragel HT4) was selected. Preparing 3.0% sulfur-containing polymer glue solution by using purified N-methyl pyrrolidone (NMP) solvent, and standing the prepared solution for one day for later use. During the test, tetrahydrofuran is firstly sucked by a syringe, and then the syringe is washed, and the test is repeated for several times. Then, 5ml of the test solution was aspirated, the air in the syringe was removed, and the needle tip was wiped dry. And finally, slowly injecting the sample solution into the sample inlet. And obtaining detection data of the weight average molecular weight after the indication is stable.

In some embodiments, the sulfur-containing polymer has a weight average molecular weight of 1×10 ⁴ 、1×10 ⁵ 、1×10 ⁶ 、1×10 ⁷ 、1×10 ⁸ 、1×10 ⁹ Or any numerical value therebetween.

In some embodiments, the sulfur-containing polymer comprises a structure represented by formula X,

x is a metal alloy

In some embodiments, n can be selected from 1, 10 ² 、10 ³ 、10 ⁴ 、10 ⁵ 、10 ⁶ 、10 ⁷ Or any numerical range therebetween.

In some embodiments, p can be selected from 1, 10 ² 、10 ³ 、10 ⁴ 、10 ⁵ 、10 ⁶ 、10 ⁷ Or any numerical range therebetween.

In some embodiments, n/p may be selected to be 1, 2, 3, 4, 5 or any number therebetween.

In some embodiments, the sulfur-containing polymer is a random copolymer.

In some embodiments, the sulfur-containing polymer is a block copolymer.

In some embodiments, the sulfur-containing polymer is used as a binder for the negative electrode of a secondary battery.

In some embodiments, the unsaturated monomer comprising a polysulfide linkage comprises a monomer of formula IV,

IV (IV)

In some embodiments, the polymerizable monomers include styrene and butadiene.

In some embodiments, the polymerization reaction system further comprises an initiator and a chain transfer agent, optionally the initiator comprises an azo initiator, and the chain transfer agent comprises a reversible addition-fragmentation chain transfer agent.

In some embodiments, the polymerization is a reversible addition-fragmentation chain transfer polymerization.

Herein, the term "reversible addition-fragmentation chain transfer polymerization" (RAFT polymerization) is a reversible deactivation radical polymerization, also referred to as "living"/controlled radical polymerization process. The main principle of RAFT polymerization is that by adding a reversible addition-fragmentation chain transfer agent (RAFT agent) as a chain transfer agent in free radical polymerization, free radicals which are easy to terminate are protected by a chain transfer mode, so that most of free radicals in the polymerization reaction are converted into dormant species of free radicals, and a dormant chain segment and a living chain segment exist simultaneously in the reaction process and are continuously and rapidly switched with each other through a dynamic reversible reaction, so that only a few polymer chains exist in the form of the living chain at any moment and are grown, and finally the growth probability of each polymer chain segment is approximately equal, and the characteristic of living polymerization is shown.

Controllable polymerization can be realized by adopting reversible addition-fragmentation chain transfer polymerization, so that the molecular weight distribution of the product is narrower and the consistency is higher.

In some embodiments, the method of making further comprises the steps of:

v (V)

In some embodiments, the reaction system of the first reaction further comprises a first pH adjuster comprising an organic amine.

In some embodiments, the method of making further comprises the steps of:

VI (VI)

In some embodiments, x1 may be selected from 1, 2, 3, 4, 5, 6.

In some embodiments, the reaction system of the second reaction further comprises a solvent and a second pH adjuster, optionally, the second pH adjuster comprises pyridine.

[ negative electrode sheet ]

A third aspect of the present application provides a negative electrode tab comprising a negative electrode film layer comprising a binder comprising the sulfur-containing polymer of any embodiment or the sulfur-containing polymer prepared by the preparation method of any embodiment.

In some embodiments, the binder is present in an amount of 0.1% to 50%, alternatively 1% to 5%, by mass based on the total mass of the negative electrode film layer.

In some embodiments, the mass content of the binder may be selected to be 0.1%, 1%, 5%, 10%, 20%, 30%, 40%, 50% or any value therebetween, based on the total mass of the negative electrode film layer.

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 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 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.

[ 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 a positive active material.

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, the positive electrode active material may employ a positive electrode active material for a 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.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

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.

[ 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.

A third aspect of the present application provides a secondary battery comprising the negative electrode tab of any of the embodiments.

In some embodiments, the secondary battery is a lithium secondary battery.

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. 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 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, etc., but is not limited thereto.

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.

1. Preparation method

Example 1:

synthesis of sulfur-containing polymers

A quantity of 20mmol of each of thiophenol and p-thiol phenol and 40mmol of pyridine were added to 100ml of diethyl ether under nitrogen atmosphere and dissolved at-78 ℃. Will additionally contain 20mmol of sulfur dichloride (S ₂ Cl ₂ ) 100mL of diethyl ether solution was added dropwise to the above solution. After 2h of reaction, 100mL of water was added, after which the organic phase was washed with water to colorless. With MgSO ₄ The organic phase is dried, filtered under vacuum and dried to give the compound of formula V, wherein x is 4 and Ra is hydrogen.V (V)

The above compound is used as reactant, and is taken10g of the mixture was added to a tetrahydrofuran solvent, and after stirring at 0℃for a while, 15g of acryloyl chloride and 1g of triethylamine were added thereto, and stirring was carried out for 10 hours to prepare a compound of formula IV wherein x was 4 and Ra was hydrogen. IV (IV)

10mmol of the compound of formula IV having a x of 4, 50g of RAFT chain transfer agent CPP (having a structure shown in formula XI), 50mmol of butadiene, 50mmol of styrene, and 0.1g of azobisisobutyronitrile AIBN were mixed and stirred at 70℃for 5 hours. And filtering and drying to obtain the sulfur-containing polymer shown in the formula XII, wherein the proportion of the monomers is controlled so that the polymerization degree m is 6, n is 80 and p is 20.XI (XI)XII (XII)

Preparation of negative electrode plate

Graphite, a conductive agent, sodium carboxymethylcellulose (CMC-Na), and the sulfur-containing polymer were mixed according to a ratio of 95:1:1: and 3, mixing, adding deionized water, stirring, and dispersing to prepare the negative electrode slurry. And then coating the negative electrode slurry on a copper foil, and after both sides are finished, drying, cold pressing, slitting and tabletting to prepare the negative electrode plate.

Preparation of positive electrode plate

Mixing 97wt% of lithium iron phosphate serving as a positive electrode active material, 1wt% of conductive carbon black serving as a conductive agent and 2wt% of polyvinylidene fluoride serving as a binder, adding N-methyl pyrrolidone, stirring and dispersing to obtain positive electrode slurry. And then coating the positive electrode slurry on an aluminum foil, and drying, cold pressing, cutting and preparing the positive electrode plate after the positive electrode slurry is finished.

Preparation of electrolyte

In an argon atmosphere glove box (H ₂ O<0.1ppm，O ₂ <0.1 ppm), uniformly mixing organic solvent Ethylene Carbonate (EC)/methyl ethyl carbonate (EMC) according to a volume ratio of 3/7,adding 12.5% LiPF ₆ Lithium salt (LiPF) ₆ The mass percentage of the lithium salt in the electrolyte is 12.5 percent, and the electrolyte of the example 1 is obtained after the lithium salt is dissolved in the organic solvent and stirred uniformly.

Battery preparation

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, enabling the isolating film to be positioned in the middle of the positive electrode and the negative electrode to play a role in isolation, and winding and hot-pressing to obtain the bare cell. And placing the bare cell in an outer package, injecting the prepared electrolyte, and performing the procedures of packaging, liquid injection, formation, exhaust and the like to obtain the lithium ion battery.

Examples 2 to 4 are basically the same as the synthesis method of example 1, except that the types of sulfur dichloride charged during the synthesis of the sulfur-containing polymer are changed in examples 2 to 4, and the value of X in the polymer represented by formula X is further controlled, specifically:

the sulfur dichloride charged in example 2 was SCl ₂ X is 3;

the sulfur dichloride charged in example 3 was S ₃ Cl ₂ X is 5;

the sulfur dichloride charged in example 4 was S ₆ Cl ₂ X is 8.

Example 5 was prepared substantially the same as example 1 except that in example 5, the thiophenol was adjusted to 4-tolylthiophenol during the synthesis of the sulfur-containing polymer so that Ra was methyl.

Examples 6 to 9 are substantially identical to the preparation process of example 1, except that in examples 6 to 9 the amounts of butadiene and styrene are adjusted during the synthesis of the sulfur-containing polymer so that the molar ratio of polymerization degree of the structural units of formula II to formula III in formula X is varied, as shown in the table.

In example 6, 10mmol of the compound of formula IV with x of 4, 50g of RAFT chain transfer agent CPP, 13mmol of butadiene, 13mmol of styrene and 0.1g of azobisisobutyronitrile AIBN were mixed and stirred at 70℃for 5h. Filtering and drying to obtain a sulfur-containing polymer, wherein n/p is 1;

in example 7, butadiene and styrene were 25mmol and n/p was 2;

in example 8, butadiene and styrene were 35mmol and n/p was 3;

in example 9, butadiene and styrene were 60mmol and n/p was 5.

Examples 10-13 were prepared in substantially the same manner as in example 1, except that examples 10-13 controlled the polymerization time and thus the weight average molecular weight/polymerization degree of the sulfur-containing polymer.

In example 10, 10mmol of the compound of formula IV with x of 4, 50g of RAFT chain transfer agent CPP, 50mmol of butadiene, 50mmol of styrene and 0.1g of azobisisobutyronitrile AIBN were mixed and stirred at 70℃for 1h. Filtering and drying to obtain a polymer having a weight average molecular weight of 10 ⁴ Is a sulfur-containing polymer of (2).

In example 11, the sulfur-containing polymer has a weight average molecular weight of 10, which is stirred at 70℃for 3 hours ⁶ 。

In example 12, the sulfur-containing polymer has a weight average molecular weight of 10, which is stirred at 70℃for 7 hours ⁷ 。

In example 13, the sulfur-containing polymer was stirred at 70℃for 10 hours and had a weight average molecular weight of 10 ⁹ 。

Examples 14 to 17 were substantially the same as the preparation method of example 1, except that the addition amount of the sulfur-containing polymer was adjusted in examples 14 to 17, and the content of graphite was changed accordingly.

In example 14, graphite, a conductive agent, sodium carboxymethylcellulose (CMC-Na), and a sulfur-containing polymer in the negative electrode slurry were mixed according to 97.9:1:1: 0.1.

In example 15, graphite, a conductive agent, sodium carboxymethylcellulose (CMC-Na), and a sulfur-containing polymer in the negative electrode slurry were mixed according to 48:1:1: 50.

In example 16, graphite, a conductive agent, sodium carboxymethylcellulose (CMC-Na), and a sulfur-containing polymer in the negative electrode slurry were mixed according to 97:1:1: 1.

In example 17, graphite, a conductive agent, sodium carboxymethylcellulose (CMC-Na), and a sulfur-containing polymer in the negative electrode slurry were mixed according to 93:1:1:5, mixing.

The comparative example was prepared in substantially the same manner as in example 1 except that the sulfur-containing polymer was replaced with a styrene-butadiene emulsion.

2. Test method

1. Weight average molecular weight test

A Waters 2695 Isocric HPLC gel chromatograph (differential refractive detector 2141) was used. A sample of 3.0% by mass polystyrene solution was used as a reference and a matched column (oiliness: styragel HT5 DMF 7.8X 300mm+Styragel HT4) was selected. Preparing 3.0% sulfur-containing polymer glue solution by using purified N-methyl pyrrolidone (NMP) solvent, and standing the prepared solution for one day for later use. During the test, tetrahydrofuran is firstly sucked by a syringe, and then the syringe is washed, and the test is repeated for several times. Then, 5ml of the test solution was aspirated, the air in the syringe was removed, and the needle tip was wiped dry. And finally, slowly injecting the sample solution into the sample inlet. And obtaining detection data of the weight average molecular weight after the indication is stable.

2. Infrared testing method

And mixing the synthesized sulfur-containing polymer with KBr, tabletting, and testing by adopting an FTIR650 Fourier infrared spectrometer to obtain an infrared spectrogram curve of the sulfur-containing polymer.

3. Adhesive strength of pole piece

Coating the negative electrode slurry on the surface of a current collector (such as a current collector), drying and cold pressing the negative electrode slurry into a pole piece (compacting 2.3 g/cc), and cutting the prepared pole piece into a test sample with the size of 20X 100mm for later use; the surface of the pole piece, which needs to be tested, is glued by double-sided adhesive, and is compacted by a compression roller, so that the pole piece is completely attached to the pole piece; the other surface of the double faced adhesive tape of the sample is adhered to the surface of stainless steel, one end of the sample is reversely bent, and the bending angle is 180 degrees; and (3) testing by adopting a high-speed rail tensile machine, fixing one end of the stainless steel on a clamp below the tensile machine, fixing the bent tail end of the sample on the clamp above, adjusting the angle of the sample, ensuring that the upper end and the lower end are positioned at vertical positions, then stretching the sample at a speed of 50mm/min until the sample is completely peeled off from a substrate, recording displacement and acting force in the process, taking the force in the process of stress balance as the adhesive force of a pole piece, and taking the adhesive length of the force divided by the style as the adhesive strength.

4. Battery DC impedance test

The corresponding battery of example 1 was charged to 4.25V at a constant current of 1/3C at 25C, then charged to 0.05C at a constant voltage of 4.25V, and after 5min of rest, voltage V1 was recorded. Then discharging for 30s at 1/3C, and recording the voltage V2, and obtaining the internal resistance DCR1 of the battery after the first circulation at (V2-V1)/1/3C. The above procedure was repeated for the same battery, and the internal resistance DCRn (n=1, 2, 3 … … 100) of the battery after the nth cycle was recorded at the same time. Taking the internal resistance DCR3 of the battery after the 3 rd cycle as the internal resistance of the battery.

5. Battery cycle capacity retention rate

The battery was charged to 4.25V at a constant current of 1/3C, then charged to 0.05C at a constant voltage of 4.25V, left for 5min, then discharged to 2.8V 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 ratio Pn=Cn/C0×100% after each cycle, and recording the battery cycle capacity retention ratio after 200 cycles.

3. Analysis of test results for examples and comparative examples

Batteries of each example and comparative example were prepared separately according to the above-described methods, and each performance parameter was measured, and the results are shown in table 1 below.

TABLE 1

The IR results for sulfur-containing polymers show that they appear to be in the 500-400cm range ^-1 S-S characteristic peak at wave band, 700-600cm ^-1 C-S characteristic peaks at the band; 1742cm ^-1 -c=o-characteristic peak at band; 1241cm ^-1 Characteristic peak of-C-C (O) -O-at wavelength band of 2247cm ^-1 -C-N-characteristic peak at band of wavelengths, 1062.6cm ^-1 -c=s-characteristic peak at band, 3000-3200cm ^-1 -OH characteristic peak at band, 759cm ^-1 、659cm ^-1 Characteristic peaks of benzene rings at the wavelength bands indicate successful synthesis of sulfur-containing polymers containing polysulfide linkages.

As can be seen from the comparison of examples and comparative examples, the sulfur-containing polymer of the structure of formula XII can simultaneously function as a binder and a film forming agent, and lithium sulfide is formed by breaking sulfur-sulfur chemical bonds, so that the stability and ionic conductivity of the solid electrolyte membrane are improved, the battery impedance is reduced, and the battery cycle stability is improved.

As can be seen from comparison of examples and comparative examples, the inclusion of 3 to 8 sulfur atoms in the polysulfide linkage of the sulfur-containing polymer can improve the cycle stability of the battery and reduce the battery resistance.

As can be seen from the comparison of examples and comparative examples, the molar ratio of the structural unit represented by formula II to the structural unit represented by formula III in the sulfur-containing polymer is 1 to 5, which can improve the cycle stability of the battery and reduce the impedance of the battery.

As can be seen from examples 6-9, the molar ratio of the structural unit shown in formula II to the structural unit shown in formula III in the sulfur-containing polymer is 2-4, which can further balance the adhesive force of the pole piece and the battery impedance, and optimize the cycle stability of the battery.

As can be seen from a comparison of examples and comparative examples, the sulfur-containing polymer has a weight average molecular weight of 10 ⁴ -10 ⁹ The cycling stability of the battery can be improved, and the impedance of the battery can be reduced.

As can be seen from examples 10-13, the sulfur-containing polymer has a weight average molecular weight of 10 ⁶ -10 ⁷ The adhesive force of the pole piece is further improved, the impedance of the battery is further reduced, and the cycling stability of the battery is further optimized.

As can be seen from the comparison of examples and comparative examples, the mass content of the binder sulfur-containing polymer of 0.1% to 50% based on the total mass of the negative electrode film layer can improve the cycle stability of the battery and reduce the battery resistance.

It can be seen from examples 14 to 17 that the mass content of the binder sulfur-containing polymer of 1 to 5% based on the total mass of the negative electrode film layer can further balance the adhesive force of the electrode sheet and the battery impedance, and optimize the cycle stability of the battery.

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 sulfur-containing polymer, characterized in that the side chain of the sulfur-containing polymer comprises polysulfide bonds containing at least three sulfur atoms, and the sulfur-containing polymer also comprises structural units shown in a formula II,

II (II)

Wherein m is more than or equal to 1 and less than 10 ⁷ 。

2. The sulfur-containing polymer of claim 1 wherein the polysulfide linkage comprises from 3 to 8 sulfur atoms.

3. The sulfur-containing polymer of claim 1, wherein the sulfur-containing polymer comprises structural units of formula I,

i is a kind of

4. The sulfur-containing polymer according to claim 1, wherein the ratio of the polymerization degree m of the structural unit derived from butadiene in the structural unit represented by formula II to the polymerization degree n of the structural unit represented by formula II in the sulfur-containing polymer is not less than 1.

5. The sulfur-containing polymer according to claim 1, wherein the ratio of the polymerization degree m of the structural unit derived from butadiene in the structural unit represented by formula II to the polymerization degree n of the structural unit represented by formula II in the sulfur-containing polymer is 1 to 10.

6. A sulfur-containing polymer according to claim 3, wherein the molar ratio of the structural unit represented by formula II to the structural unit represented by formula I in the sulfur-containing polymer is 1 to 5.

7. A sulfur-containing polymer according to claim 3, wherein the molar ratio of the structural unit represented by formula II to the structural unit represented by formula I in the sulfur-containing polymer is 2 to 4.

8. A sulfur-containing polymer as defined in claim 3 wherein said structural unit of formula I has a structure of formula III,

formula III

9. The sulfur-containing polymer of claim 8, wherein the polymer comprises a sulfur-containing polymer,

ra comprises hydrogen, C _1-4 At least one of alkyl groups, x is more than or equal to 3 and less than or equal to 5.

10. The sulfur-containing polymer of claim 1, wherein the sulfur-containing polymer has a weight average molecular weight of 1 x 10 ⁴ -1×10 ⁹ 。

11. The sulfur-containing polymer of claim 1 wherein the sulfur-containing polymer comprisesThe sulfur polymer has a weight average molecular weight of 1X 10 ⁶ -1×10 ⁷ 。

12. The sulfur-containing polymer of claim 1, wherein the sulfur-containing polymer comprises a structure of formula X,

X is a metal alloy

13. Use of the sulfur-containing polymer as defined in any one of claims 1 to 12 as a binder for secondary batteries.

14. A process for preparing a sulfur-containing polymer, comprising:

polymerizing a polymerizable monomer with an unsaturated monomer containing a polysulfide linkage under polymerizable conditions to produce a sulfur-containing polymer comprising a polysulfide linkage of at least three sulfur atoms in a side chain of the sulfur-containing polymer.

15. The method of claim 14, wherein the process comprises,

the unsaturated monomer containing polysulfide bond contains a monomer shown in a formula IV,

IV (IV)

16. The method of claim 14, wherein the process comprises,

the polymerizable monomers include styrene and butadiene.

17. The method of claim 14, wherein the process comprises,

the reaction system of the polymerization reaction also comprises an initiator and a chain transfer agent.

18. The method of claim 17, wherein the process comprises,

The initiator includes azo initiators.

19. The method of claim 17, wherein the process comprises,

the chain transfer agent comprises a reversible addition-fragmentation chain transfer agent.

20. The method of manufacturing according to claim 15, further comprising the steps of:

the monomer shown in the formula V and the acrylic chloride are subjected to a first reaction to prepare the monomer shown in the formula IV,

v (V)

21. The method according to claim 20, wherein,

the reaction system of the first reaction further comprises a first pH adjuster, the first pH adjuster comprising an organic amine.

22. The method of manufacturing according to claim 20, further comprising the steps of:

mixing monomer shown in formula VI, p-thiol phenol and S _x1 Cl ₂ Carrying out a second reaction to prepare the monomer shown in the formula V,

VI (VI)

23. The method of claim 22, wherein the process comprises,

The reaction system of the second reaction also comprises a solvent and a second pH regulator.

24. The method of claim 23, wherein the process comprises,

the second pH regulator comprises tizite.

25. A negative electrode sheet comprising a negative electrode film layer comprising a binder comprising the sulfur-containing polymer of any one of claims 1-12 or the sulfur-containing polymer prepared by the method of any one of claims 14-24.

26. The negative electrode tab of claim 25, wherein the binder is present in an amount of 0.1-50% by mass based on the total mass of the negative electrode film layer.

27. The negative electrode tab of claim 25, wherein the binder is present in an amount of 1-5% by mass based on the total mass of the negative electrode film layer.

28. A secondary battery comprising the negative electrode tab of any one of claims 25 to 27.

29. An electric device comprising the secondary battery according to claim 28.