Conductive binder and method for preparing the same, silicon negative electrode, lithium battery, and vehicle

Abstract

The application discloses a conductive binder and a preparation method thereof, a silicon negative electrode, a lithium battery and a vehicle. The conductive binder comprises a polymer A and a polymer B. The polymer A comprises a polymer chain segment containing a sulfonic acid group and a polymer chain segment containing a carboxyl group, and the polymer B is a conductive polymer. The structural formula of the polymer A is as follows: The conductive binder has good adhesion and conductivity, can construct a cross-linked three-dimensional network structure around silicon particles, effectively prevents the irreversible sliding of the silicon particles and the volume change of the buffer, thereby maintaining the electrical connection and integrity of the electrode, and prolonging the service life of the battery.

Description

Technical Field

[0001] This invention generally relates to the field of lithium battery technology, and specifically to a conductive binder and its preparation method, a silicon anode, a lithium battery, and a vehicle. Background Technology

[0002] As lithium-ion batteries are increasingly used in portable electronic products, power tools, and automotive power supplies, the market demand for high-energy-density lithium-ion batteries is becoming more and more urgent. One technical solution to significantly improve the energy density of lithium-ion batteries is to replace the existing graphite anode with a silicon anode.

[0003] Traditional silicon anodes consist of silicon active material, conductive agent, and binder. The binder holds the silicon active material to the current collector; the conductive agent ensures conductivity between the poorly conductive silicon active materials. However, silicon undergoes a significant volume change (300%) during charge and discharge. Existing conductive agents have weak interactions with the silicon active material, making them prone to separation. Furthermore, existing binders only provide adhesion and lack conductivity. When the silicon active material and conductive agent separate, the conductive pathway of the silicon anode is disrupted, leading to a rapid decline in battery capacity and cycle performance. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a conductive binder and its preparation method, a silicon anode, a lithium battery, and a vehicle. The conductive binder has good conductivity and good adhesion, and can adapt to the volume change of silicon, ensuring the integrity of the conductive path of the silicon anode, thereby extending the service life of the battery.

[0005] In a first aspect, the present invention provides a conductive adhesive comprising polymer A and polymer B; wherein polymer A comprises polymer segments containing sulfonic acid groups and polymer segments containing carboxyl groups, polymer B is a conductive polymer, and the structural formula of polymer A is as follows:

[0006]

[0007] R1, R2, and R3 are each independently hydrogen, halogen, or C1-C6 alkyl;

[0008] R4 and R5 are each independently methylene groups of C0-C6 and C6-C6, respectively. 12 aryl, C6-C 12 cycloalkyl groups, C2-C containing heteroatoms 10 alkyl, Any one of the following; wherein M and Q are each independently C1-C6 methylene, phenyl, cyclohexyl, or C2-C containing heteroatoms. 10any of the alkyl groups;

[0009] R6 is selected from -(CH2). p1 -OH, -(CH2) p2 -NH2, C0-C6 alkyl groups, C2-C containing heteroatoms 10 alkyl, Where Y is selected from hydrogen, -(CH2) q1 -OH, -(CH2) q2 -NH2, C1-C6 alkyl, phenyl, cyclohexyl, C2-C containing heteroatoms 10 The alkyl group, p1 and p2 are each independent integers from 0 to 6; q1 and q2 are each independent integers from 2 to 6;

[0010] R7 is selected from hydrogen or lithium atoms;

[0011] x, y, and z are the molar ratios of the corresponding chain segments to the whole polymer. Each of x, y, and z is an independent decimal between 0 and 1, and x + y + z equals 1.0.

[0012] Among them, C1-C6 alkyl groups, C0-C6 methylene groups, and C6-C 12 aryl, C6-C 12 cycloalkyl groups, C2-C containing heteroatoms 10 Alkyl groups, C1-C6 methylene groups, phenyl groups, cyclohexyl groups, and C2-C6 groups containing heteroatoms 10 The hydrogen atoms in the alkyl or C0-C6 alkyl groups can be replaced by substituents.

[0013] As an optional scheme, the molar ratio of polymer A to polymer B is 1:(0.05~0.6).

[0014] As an alternative, the substituents are selected from halogens, hydroxyl groups, amino groups, carboxyl groups, carbonyl groups, cyano groups, sulfonic acid groups, C1-C6 alkoxy groups, C1-C6 alkyl groups, and C6 alkyl groups. 6- C 12 aryl or C6-C 12 cycloalkyl groups.

[0015] As an alternative, the halogen is selected from fluorine, chlorine, and bromine; the amino group is selected from C1-C6 primary amines, C1-C6 alkyl-substituted secondary or tertiary amines; the C1-C6 alkoxy group is selected from methoxy or ethoxy; the C1-C6 alkyl group is selected from methyl, ethyl, propyl, isopropyl, butyl, or tert-butyl; and the C6-C6 alkoxy group is selected from... 12 The aryl group is selected from phenyl, naphthyl, or biphenyl, C6-C 12 The cycloalkyl group is selected from cyclohexyl or bicyclohexyl.

[0016] As an alternative, 0.3≤x≤0.9, 0.1≤y≤0.3, 0<z≤0.4.

[0017] As an optional option, the molecular weight of the conductive adhesive is 1,000 to 1,000,000, preferably 50,000 to 500,000.

[0018] In a second aspect, the present invention provides a method for preparing a conductive adhesive according to the first aspect, comprising the following steps:

[0019] The monomers of polymer B are mixed evenly with polymer A in a solvent, an initiator is added to initiate polymerization, and the solvent is removed to obtain a conductive binder; wherein, the monomers of polymer B are selected from any one of aniline, pyrrole, 3,4-ethylenedioxythiophene or their derivatives.

[0020] As an optional solution, the solvent is any one of water, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, or dimethyl sulfoxide.

[0021] As an optional option, the initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl peroxide, benzophenone, benzoyl ketone, methyl o-benzoylbenzoate, potassium persulfate, ammonium persulfate, potassium dichromate, hydrogen peroxide, and ferric chloride.

[0022] Thirdly, the present invention provides a silicon anode for a lithium battery, comprising: a current collector and a silicon active material layer formed on the surface of the current collector, the silicon active material layer comprising the conductive binder of the first aspect.

[0023] Fourthly, the present invention provides a lithium battery, including the silicon anode of the lithium battery of the third aspect.

[0024] Fifthly, the present invention provides a vehicle including the lithium battery of the fourth aspect.

[0025] The conductive binder provided in this application contains sulfonic acid and carboxyl segments in polymer A, giving it excellent adhesion. Polymer B is a conductive polymer, which improves the conductivity of the binder. The sulfonic acid groups can form electrostatic interactions with polymer B, resulting in uniform dispersion of polymer B, which is beneficial for preparing silicon anodes. The carboxyl groups can form strong interactions with silicon active materials, giving the binder excellent adhesion. Polymer B improves the conductivity of the binder, and the electrostatic interactions and hydrogen bonds between polymer B and the sulfonic acid groups facilitate cross-linking of the binder. This allows for the construction of a cross-linked three-dimensional network structure around silicon particles, effectively preventing irreversible slippage of silicon particles, buffering volume changes, maintaining the electrical connection and integrity of the electrode, and extending the battery's lifespan. Detailed Implementation

[0026] The present application will now be described in further detail with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the embodiments.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0028] This invention provides a conductive adhesive comprising polymer A and polymer B; wherein polymer A comprises polymer segments containing sulfonic acid groups and polymer segments containing carboxyl groups, and polymer B is a conductive polymer. The structural formula of polymer A is as follows:

[0029]

[0030] R1, R2, and R3 are each independently hydrogen, halogen, or C1-C6 alkyl;

[0031] R4 and R5 are each independently methylene groups of C0-C6 and C6-C6, respectively. 12 aryl, C6-C 12 cycloalkyl groups, C2-C containing heteroatoms 10 alkyl, Any one of the following; wherein M and Q are each independently C1-C6 methylene, phenyl, cyclohexyl, or C2-C containing heteroatoms. 10 any of the alkyl groups;

[0032] R6 is selected from -(CH2). p1 -OH, -(CH2) p2 -NH2, C0-C6 alkyl groups, C2-C containing heteroatoms 10 alkyl, Where Y is selected from hydrogen, -(CH2) q1 -OH, -(CH2) q2 -NH2, C1-C6 alkyl, phenyl, cyclohexyl, C2-C containing heteroatoms 10 The alkyl group, p1 and p2 are each independent integers from 0 to 6; q1 and q2 are each independent integers from 2 to 6;

[0033] R7 is selected from hydrogen or lithium atoms;

[0034] x, y, and z are the molar ratios of the corresponding chain segments to the whole polymer. Each of x, y, and z is an independent decimal between 0 and 1, and x + y + z equals 1.0.

[0035] In this embodiment, the main active components of the conductive binder are polymer A and polymer B. The conductive binder may contain only polymer A and polymer B, or it may include other components in addition to polymer A and polymer B. For example, in the actual preparation process, lithium salts may be introduced into the conductive binder. There are no limitations on the specific other components.

[0036] Among them, C1-C6 alkyl groups, C0-C6 methylene groups, and C6-C 12 aryl, C6-C 12 cycloalkyl groups, C2-C containing heteroatoms 10 Alkyl groups, C1-C6 methylene groups, phenyl groups, cyclohexyl groups, and C2-C6 groups containing heteroatoms 10 The hydrogen atoms in the alkyl group or C0-C6 alkyl group may be replaced by substituents; wherein the heteroatom may be any element other than C, preferably oxygen, nitrogen or sulfur.

[0037] The R6 group is used to adjust the rigidity of polymer A, in order to solve the problem that polymers containing only sulfonic acid groups and carboxyl groups are too brittle and cannot adapt to the volume expansion of silicon, resulting in silicon particles falling off.

[0038] Controlling the values ​​of x, y, and z is beneficial for adjusting the content of carboxyl segments, sulfonic acid segments, and rigidity regulating groups in the conductive adhesive, thereby helping to control the adhesiveness and rigidity of the conductive adhesive.

[0039] It is understood that polymer A is mainly used to provide adhesion to the adhesive and to uniformly disperse polymer B. Polymer B can be any conductive polymer, such as polyaniline, polypyrrole, polythiophene and its derivatives, and is mainly used to provide conductivity to the adhesive. In this embodiment, the ratio between polymer B and polymer A is not limited.

[0040] The conductive binder of this embodiment is obtained by compounding polymer A and polymer B, which simultaneously contain sulfonic acid groups and carboxyl groups, so that the binder has both good conductivity and adhesion properties. When preparing the electrode sheet, no additional conductive agent or only a very small amount of conductive agent needs to be added. The sulfonic acid groups and carboxyl groups can both form electrostatic and hydrogen bonding interactions with polymer B, which helps polymer B to disperse uniformly; the carboxyl groups can form strong hydrogen bonding interactions with silicon active materials, thereby improving the adhesion performance of the binder; the R6 groups in polymers B and A not only help improve the tensile strength of the binder, but also help prevent the binder from swelling in the electrolyte.

[0041] The excellent adhesion and conductivity of the conductive binder in this embodiment help maintain the electrical connection of silicon particles, thereby improving the cycle life of the silicon anode. Furthermore, due to the electrostatic and hydrogen bonding between the sulfonic acid groups, carboxyl groups, and conductive polymer, the binder can build a cross-linked three-dimensional network structure around the silicon particles, effectively preventing irreversible slippage of the silicon particles and buffering volume changes, thereby maintaining the electrical connection and integrity of the electrode, which is beneficial to further extending the battery's lifespan.

[0042] The conductive binder in this embodiment exhibits excellent conductivity and adhesion due to the synergistic effect of polymers A and B. Furthermore, the electrostatic and hydrogen bonding interactions between the sulfonic acid groups, carboxyl groups, and the conductive polymers enhance the processability and uniformity of the conductive polymers during preparation, thereby improving the conductivity of the binder. Simultaneously, the electrostatic and hydrogen bonding interactions facilitate the crosslinking of the binder, enabling it to construct a crosslinked three-dimensional network structure around the silicon particles. This effectively prevents irreversible slippage of the silicon particles, buffers volume changes, maintains the electrical connection and integrity of the electrodes, and extends the battery's lifespan.

[0043] Furthermore, the molar ratio of polymer A to polymer B is 1:(0.05 to 0.6).

[0044] Furthermore, the substituents are selected from halogens, hydroxyl groups, amino groups, carboxyl groups, carbonyl groups, cyano groups, sulfonic acid groups, C1-C6 alkoxy groups, C1-C6 alkyl groups, and C6 alkyl groups. 6- C 12 aryl or C6-C 12 The cycloalkyl groups are used to improve the conductivity and adhesion of the conductive binder, facilitate adaptation to changes in silicon volume, and promote uniform lithium-ion distribution, thereby improving the performance of the silicon anode.

[0045] In a preferred embodiment, the halogen is selected from any one of fluorine, chlorine, and bromine; the amino group is selected from C1-C6 primary amines, C1-C6 alkyl-substituted secondary or tertiary amines; the C1-C6 alkoxy group is selected from methoxy or ethoxy; the C1-C6 alkyl group is selected from methyl, ethyl, propyl, isopropyl, butyl, or tert-butyl; and the C6-C6... 12 The aryl group is selected from phenyl, naphthyl, or biphenyl, C6-C 12 The cycloalkyl group is selected from cyclohexyl or bicyclohexyl.

[0046] Furthermore, 0.3 ≤ x ≤ 0.9, 0.1 ≤ y ≤ 0.3, and 0 < z ≤ 0.4. For example, x can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc.; y can be 0.1, 0.2, 0.3, etc.; and z can be 0.1, 0.2, 0.3, 0.4, etc. The range of values ​​for x, y, and z disclosed in this embodiment is beneficial for adjusting the content of carboxyl segments, sulfonic acid segments, and conductive polymer segments, so that the binder has optimal conductivity and adhesion.

[0047] Further, the molecular weight of the conductive adhesive is between 1,000 and 1,000,000. For example, the molecular weight of the conductive adhesive can be 1,000, 3,000, 5,000, 8,000, 10,000, 30,000, 50,000, 60,000, 80,000, 100,000, 2,000,000, 500,000, 700,000, 800,000, 1,000,000, etc. Preferably, the molecular weight of the conductive adhesive is between 50,000 and 500,000. The embodiments of the present invention do not limit the specific molecular weight.

[0048] In summary, the conductive binder of this application embodiment has good adhesion and conductivity. It is beneficial for conducting lithium ions and can bond tightly with silicon, constructing a cross-linked three-dimensional network structure around silicon particles. This effectively prevents irreversible slippage of silicon particles, buffers volume changes, thereby maintaining the electrical connection and integrity of the electrodes and extending the battery's lifespan.

[0049] Furthermore, by controlling the content of each functional group, the adhesive can achieve optimal adhesion and conductivity.

[0050] In a second aspect, the present invention provides a method for preparing a conductive adhesive according to the first aspect, comprising the following steps:

[0051] The monomers of polymer B and polymer A are mixed evenly in a solvent, an initiator is added to initiate polymerization, and the solvent is removed to obtain a conductive binder; wherein, the monomer of polymer B is selected from any one of aniline, pyrrole, 3,4-ethylenedioxythiophene or their derivatives.

[0052] It should be noted that polymer A is prepared by using monomeric compounds containing sulfonic acid groups (e.g., sulfonic acid groups). ), monomeric compounds containing carboxylic acids (e.g.: ) and monomers containing the R6 group (e.g.: It is obtained through a polymerization reaction, wherein the polymerization reaction method is applicable to any existing polymerization reaction method, and the embodiments of this application do not specifically limit it.

[0053] Polymers of aniline, pyrrole, and 3,4-ethylenedioxythiophene have good electrical conductivity, but their processability is poor and they are difficult to disperse uniformly in solvents. Through the electrostatic and hydrogen bonding between the sulfonic acid groups and carboxyl groups in polymer A and the conductive polymer, the conductive polymer can be uniformly dispersed in the solvent, thereby enhancing the processability of the conductive polymer and simultaneously enhancing the conductivity of polymer A.

[0054] The molar ratio of the monomer of polymer B to the sulfonic acid group in polymer A is (2:1) to (1:2), preferably 1:1.

[0055] The addition of an initiator facilitates the polymerization of conductive polymer monomers, making the reaction easier to proceed.

[0056] For example,

[0057] 3,4-Ethylenedioxythiophene and polymer A were mixed uniformly in N,N-dimethylformamide. After adding potassium persulfate to initiate polymerization, the solvent was removed to obtain a conductive binder. The structural formula of polymer A is shown below.

[0058]

[0059] Further, the solvent is any one of water, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, or dimethyl sulfoxide.

[0060] Furthermore, the initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl peroxide, benzophenone, benzophenone, methyl o-benzoylbenzoate, potassium persulfate, ammonium persulfate, potassium dichromate, hydrogen peroxide, and ferric chloride.

[0061] Thirdly, the present invention provides a silicon anode for a lithium battery, comprising: a current collector and a silicon active material layer formed on the surface of the current collector, the silicon active material layer comprising the conductive binder of the first aspect. Those skilled in the art will understand that the silicon anode of this lithium battery possesses all the features and advantages of the conductive binder described above, which will not be elaborated further here.

[0062] In a specific embodiment, the silicon anode of the lithium battery is prepared through the following process:

[0063] The silicon-based active material, binder, and conductive agent are mixed together, and a dispersant is added and stirred thoroughly. The mixed slurry is then coated onto copper foil, dried, and cut into electrode sheets.

[0064] Among them, the mass percentage of the binder in the total mass of the silicon-based active material, the binder and the conductive additive is 2% to 30%; the mass percentage of the silicon-based active material is 60% to 97.5%; the mass percentage of the conductive additive is 0.5% to 10%;

[0065] The stirring method can be mortar grinding, blender grinding, ball milling, etc., preferably mortar grinding, and the grinding time is 5 min to 30 min;

[0066] The drying method can be air drying, vacuum drying or freeze drying, etc., preferably vacuum drying, the drying temperature is 80°C to 150°C, and the time is 4 h to 24 h;

[0067] The silicon-based active material includes nano-silicon, micro-silicon, porous silicon, amorphous silicon, silicon monoxide, silicon-carbon composite, silicon alloy;

[0068] The conductive additive is one or more of graphite, acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotube and Ketjen black;

[0069] The dispersant is one or more of water, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane and dimethyl sulfoxide.

[0070] In the fourth aspect, the present invention provides a lithium battery, including the silicon negative electrode of the lithium battery in the third aspect. Those skilled in the art can understand that this lithium battery has all the features and advantages of the aforementioned conductive binder, and will not be elaborated here. Generally speaking, the lithium battery of the embodiment of the present invention has a good cycle life.

[0071] In a specific embodiment,

[0072] The lithium battery further includes: a positive electrode, a separator and an electrolyte. Among them, the positive electrode includes a positive electrode current collector and an active material layer located on the positive electrode current collector. The active material layer includes a positive electrode active material, a binder and a conductive additive. The positive electrode active material can be selected from lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium manganese phosphate (LiMnPO4), lithium nickel phosphate (LiNiPO4), lithium manganate (LiMnO2), binary material LiNi x A (1-x) O2 (where A is selected from one of Co and Mn, 0 < x < 1), ternary material LiNimBnC (1-m-n) O2 (where B and C are independently selected from at least one of Co, Al and Mn, and B and C are different, 0 < m < 1, 0 < n < 1).

[0073] The separator can be any separator material used in existing lithium batteries, specifically polyethylene, polypropylene, polyvinylidene fluoride, and their multilayer composite membranes.

[0074] The electrolyte comprises an organic solvent, a lithium salt, and additives. The organic solvent may be selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, dimethyl sulfide, diethyl sulfite, diethyl sulfite, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, and 1,4-dioxane. At least one of tetrahydrofuran, fluorinated cyclic organic esters, and sulfur-containing cyclic organic esters; the lithium salt is selected from at least one of organic lithium salts and inorganic lithium salts, such as LiPF6, LiBF, LiClO4, LiAsF6, LiBOB, LiDFOB, and LiTFOP; the additive may be selected from at least one of vinylene carbonate, fluorocarbonate, difluoroethylene carbonate, fluoroethylene carbonate, ethylene ethylene carbonate, vinyl sulfite, methanedisulfonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, and lithium tetrafluoro(oxalate) phosphate.

[0075] Fifthly, the present invention provides a vehicle comprising the lithium battery of the fourth aspect. For example, it may include a battery pack composed of multiple lithium batteries as described above. Thus, the vehicle possesses all the features and advantages of the lithium batteries described above, which will not be repeated here.

[0076] The present invention will be described below through specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present invention in any way.

[0077] Example 1

[0078] (1) Preparation of conductive binder:

[0079] Monomers containing sulfonic acid groups Monomers containing carboxyl groups and monomers containing R6 Mix them in a certain proportion, add azobisisobutyronitrile to initiate polymerization to obtain polymer A. The structural formula of polymer A is:

[0080]

[0081] Polymer A and 3,4-ethylenedioxythiophene were mixed evenly in N,N-dimethylformamide. Potassium persulfate was added to initiate polymerization. After removing N,N-dimethylformamide, a conductive binder was obtained. The molar ratio of 3,4-ethylenedioxythiophene to the sulfonic acid groups in polymer A was 1:1.

[0082] (2) Half-cell preparation

[0083] Nano-silicon powder, carbon black (Super-P), and conductive binder I were dispersed in water at a mass ratio of 90:2:8 and ground evenly in a mortar. The slurry was then coated onto copper foil using a coating machine to a thickness of 100 μm. After drying at room temperature, the slurry was cut into 13 mm diameter discs using a slicing machine. The discs were then dried in a vacuum drying oven at 80 °C for 12 h and removed when the temperature dropped to room temperature after drying to obtain the nano-silicon anode.

[0084] The nano-silicon anode was transferred to a glove box filled with argon gas (O2 ≤ 0.5 ppm, H2O ≤ 0.5 ppm). The nano-silicon anode sheets were weighed one by one in the glove box, and the mass was recorded. A lithium metal sheet was used as the counter electrode, and a 1 mol / L LiPF6EC / DMC / DEC (v / v / v = 1 / 1 / 1) solution was used as the electrolyte. A CR2025 coin cell was assembled in the glove box.

[0085] Example 2

[0086] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0087]

[0088] Example 3

[0089] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0090]

[0091] Example 4

[0092] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0093]

[0094] Example 5

[0095] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0096]

[0097] Example 6

[0098] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0099]

[0100] Example 7

[0101] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0102]

[0103] Example 8

[0104] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0105]

[0106] Example 9

[0107] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0108]

[0109] Example 10

[0110] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0111]

[0112] Example 11

[0113] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0114]

[0115] Example 12

[0116] The difference between this embodiment and Embodiment 1 is that the structural formula of polymer A is:

[0117]

[0118] Example 13

[0119] The difference between this embodiment and Example 1 is that the molar ratio of 3,4-ethylenedioxythiophene to the sulfonic acid groups in polymer A is 2:1.

[0120] Example 14

[0121] The difference between this embodiment and Example 1 is that the molar ratio of 3,4-ethylenedioxythiophene to the sulfonic acid groups in polymer A is 1:2.

[0122] Example 15

[0123] The difference between this embodiment and Embodiment 1 is that polymer A is used. The aniline and N,N-dimethylformamide were mixed evenly, and potassium persulfate was added to initiate polymerization. The N,N-dimethylformamide was then removed to obtain a conductive binder. The molar ratio of aniline to sulfonic acid groups in polymer A was 1:1.

[0124] Example 16

[0125] The difference between this embodiment and Embodiment 1 is that polymer A is used. The polymer A is mixed thoroughly with pyrrole in N,N-dimethylformamide, and then potassium persulfate is added to initiate polymerization. The N,N-dimethylformamide is then removed to obtain a conductive binder. The molar ratio of aniline to sulfonic acid groups in polymer A is 1:1.

[0126] Comparative Example 1

[0127] The difference between this comparative example and Example 1 is that the electrode binder is PAA (polyacrylic acid).

[0128] Comparative Example 2

[0129] The difference between this comparative example and Example 1 is that the electrode binder has the following structural formula: it does not contain 3,4-ethylenedioxythiophene polymer.

[0130]

[0131] Comparative Example 3

[0132] The difference between this comparative example and Example 1 is that polymer A is PAA (polyacrylic acid).

[0133] Comparative Example 4

[0134] The difference between this comparative example and Example 1 is that the structural formula of polymer A is:

[0135]

[0136] The value of i is chosen to make the molecular weight of the polymer range from 50,000 to 500,000.

[0137] Comparative Example 5

[0138] The difference between this comparative example and Example 1 is that the structural formula of polymer A is:

[0139]

[0140] The value of j is chosen such that the molecular weight of the polymer is between 50,000 and 500,000.

[0141] Comparative Example 6

[0142] The difference between this comparative example and Example 1 is that the structural formula of polymer A is:

[0143]

[0144] Comparative Example 7

[0145] The difference between this comparative example and Example 1 is that the structural formula of polymer A is:

[0146]

[0147] Comparative Example 8

[0148] The difference between this comparative example and Example 1 is that the structural formula of polymer A is:

[0149]

[0150] The lithium batteries prepared in the above examples and comparative examples were subjected to the following performance tests to characterize the electrochemical performance of the conductive binder.

[0151] Ten batteries each from the examples and comparative examples were taken and subjected to constant current charge-discharge cycle tests at 25±1℃ using a LAND CT2001C secondary battery performance testing device. The test conditions were: discharge cut-off voltage of 0.01V, charge cut-off voltage of 1.5V, first charge-discharge cycled 3 times at a current density of 100mA / g, and then charge-discharge cycled at a current density of 500mA / g. The test results are shown in Table 1.

[0152] Table 1. Performance test results of the half-cells prepared in Examples 1-16 and Comparative Examples 1-8

[0153]

[0154]

[0155] From the results shown in Table 1, we can obtain:

[0156] Based on the test results of Examples 1-16 and Comparative Example 1, it can be concluded that the half-cells prepared in Examples 1-16 are superior to the half-cells prepared in Comparative Example 1 in terms of battery capacity and cycle performance. This indicates that the conductive binder prepared in the embodiments of the present invention is beneficial to improving the performance of lithium batteries compared with traditional binders.

[0157] Based on the test results of Examples 1-5, it can be concluded that the half-cells of Examples 1-5 all have high capacity and excellent cycle performance. Therefore, the range of molar ratios of carboxyl segments, sulfonic acid segments and rigidity regulating groups in polymer A of this application is beneficial to the conductive binder having good bonding performance, ion conduction performance and rigidity.

[0158] Based on the test results of Examples 1 and 6-12, it can be concluded that different R groups have little impact on the performance of the polymer, and the polymer structures disclosed in the embodiments of this application can effectively improve the performance of the battery.

[0159] Based on the test results of Examples 1 and 13-14, it can be concluded that the half-cells prepared using the specified values ​​of polymers A and B in this application all exhibit high capacity and good cycle performance. Combined with the half-cell test results of Comparative Example 2, the half-cell test results of Examples 1 and 13-14 are superior to those of Comparative Example 2. Since the conductive binder in Comparative Example 2 does not contain a conductive polymer, it is evident that the synergistic effect of polymers A and B improves the adhesion, conductivity, and mechanical strength of the conductive binder, thereby enhancing battery performance.

[0160] Based on the test results of Examples 1 and 15-16, it can be concluded that different conductive polymers have little impact on the performance of the binder. The half-cells prepared with the conductive binders disclosed in the embodiments of this application all have high capacity and good cycle performance.

[0161] Based on the test results of Example 1 and Comparative Examples 3-8, it can be concluded that the half-cell prepared in Example 1 is superior to the half-cells prepared in Comparative Examples 3-8 in terms of both battery capacity and cycle performance. Specifically, polymer A in Example 1 contains three chain segments, polymer A in Comparative Examples 3-5 contains only one chain segment, and Comparative Examples 6-8 contains only two chain segments. Therefore, it can be seen that the binder disclosed in this application improves battery performance due to the synergistic effect of the carboxyl chain segment, sulfonic acid chain segment, and rigid regulating group in polymer A. This results in the conductive binder possessing excellent bonding performance, conductivity, and flexibility, enabling it to bond tightly with silicon, improving the stability of silicon particles, and adapting to volume changes in silicon particles, thus improving the stability of the silicon anode during charge and discharge. Furthermore, the good bonding and conductivity ensure that the silicon anode remains electrically connected, preventing the formation of "dead silicon" and thereby improving the cycle life of the silicon anode.

[0162] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A conductive adhesive, characterized in that, The conductive binder comprises polymer A and polymer B; wherein polymer A comprises polymer segments containing sulfonic acid groups and polymer segments containing carboxyl groups, and polymer B is a conductive polymer. The structural formula of polymer A is as follows: R1, R2 and R3 are each independently hydrogen, halogen or C1-C6 alkyl; R4 and R5 are each independently methylene groups of C0-C6 and C6-C6, respectively. 12 aryl, C6-C 12 cycloalkyl groups, C2-C containing heteroatoms 10 alkyl, , , , Any one of the following; wherein M and Q are each independently C1-C6 methylene, phenyl, cyclohexyl, or C2-C containing heteroatoms. 10 any of the alkyl groups; R6 is selected from or ; R7 is selected from hydrogen or lithium atoms; x, y, and z are the molar ratios of the corresponding chain segments to the whole polymer. Each of x, y, and z is an independent decimal between 0 and 1, and x + y + z equals 1.

0. Wherein, the C1-C6 alkyl group, the C0-C6 methylene group, and the C6-C 12 aryl, the C6-C 12 cycloalkyl groups, the C2-C groups containing heteroatoms 10 Alkyl group, the C1-C6 methylene group, the phenyl group, the cyclohexyl group, the C2-C6 group containing heteroatoms 10 The hydrogen atom in the alkyl group or the C0-C6 alkyl group may be replaced by a substituent selected from halogen, hydroxyl, amino, carboxyl, cyano, C1-C6 alkoxy or C1-C6 alkyl.

2. The conductive adhesive according to claim 1, characterized in that, The molar ratio of polymer A to polymer B is 1:(0.05~0.6).

3. The conductive adhesive according to claim 1, characterized in that, 0.3≤x≤0.9, 0.1≤y≤0.3, 0<z≤0.

4.

4. The conductive adhesive according to any one of claims 1-3, characterized in that, The molecular weight of the conductive adhesive is 1,000 to 1,000,000.

5. The conductive adhesive according to claim 4, characterized in that, The molecular weight of the conductive adhesive is 50,000 to 500,000.

6. A method for preparing a conductive adhesive as described in any one of claims 1-5, characterized in that, The process includes the following: The monomer of polymer B is mixed evenly with polymer A in a solvent, an initiator is added to initiate polymerization, and the solvent is removed to obtain the conductive binder; wherein, the monomer of polymer B is selected from any one of aniline, pyrrole, 3,4-ethylenedioxythiophene or their derivatives.

7. The method according to claim 6, characterized in that, The solvent is any one of water, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, or dimethyl sulfoxide.

8. The method according to claim 6, characterized in that, The initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl peroxide, benzophenone, benzoyl benzoate, methyl o-benzoylbenzoate, potassium persulfate, ammonium persulfate, potassium dichromate, hydrogen peroxide, and ferric chloride.

9. A silicon anode for a lithium battery, comprising: A current collector and a silicon active material layer formed on the surface of the current collector, characterized in that the silicon active material layer comprises the conductive binder according to any one of claims 1-5.

10. A lithium battery, characterized in that, Including the silicon anode of the lithium battery as described in claim 9.

11. A vehicle, characterized in that, Including the lithium battery of claim 10.

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