Polymer and application thereof

Abstract

The invention relates to a polymer and application thereof. The polymer comprises a structural unit shown in a formula I. The polymer provided by the invention comprises a flexible chain segment and a conductive polymer chain segment, and the main chain segment of the conductive polymer chain segment also contains a side group. The polymer provided by the invention is used for a binder, and the flexible chain segment of the polymer can endow the binder with certain flexibility, so that an electrode can ensure certain toughness, and pole piece cracking is avoided; a conductive polymer chain segment has electronic conductivity and rigidity, and a side group contains a polar group and can form a strong acting force with a hydroxyl group on the surface of a negative electrode material, so that the electric connection and integrity of an electrode are maintained, and meanwhile, a stable conductive network is formed. When the polymer provided by the invention is applied to a negative electrode of a lithium ion battery, the mechanical integrity of the electrode can be maintained, the impedance of the battery can be reduced, and the cycling stability of a negative electrode material can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery materials, and in particular relates to a polymer and an application thereof. Background Art

[0002] Binders only account for a relatively small proportion in the electrode structure of commercial lithium-ion batteries, but they play an important role. Their main function is to bind the active material, conductive carbon and current collector together to ensure good electrical contact between the active material, conductive carbon and current collector. Therefore, the performance of the binder plays a vital role in the electrochemical performance of the electrode.

[0003] At present, commercial water-based binders on the market can meet the commercialization needs of graphite-based negative electrode materials. However, when applied to high-capacity negative electrode materials, the large volume change of the negative electrode material will cause the pulverization of the active material and the collapse of the electrode structure, which will eventually cause the electrode material to fall off from the current collector, thereby losing electronic connection and electrochemical activity. Conventional water-based conductive binders that can improve the electrochemical stability of silicon-based negative electrodes are not conducive to the processing and stability of the electrode sheet due to the rigid structure of the polymer.

[0004] CN116759581A discloses a thiolated polyacrylic acid aqueous polymer binder for lithium ion battery silicon-based negative electrode and its preparation method and application. CN117659908A discloses a preparation method and application of a high molecular polymer aqueous binder. These aqueous binders generally have the problem that the flexibility of the binder, electrode processing performance and stability performance cannot be taken into account at the same time.

[0005] Therefore, how to improve the comprehensive performance of the binder so that it can maximize the flexibility of the binder while ensuring the electronic conductivity and adhesion of the binder, and improve the processability and stability of the electrode has become an important technical problem that needs to be solved urgently. Summary of the invention

[0006] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a polymer and its application, which has conductive properties and adhesion through the design of the polymer structure. When used as a battery binder, the processability and stability of the electrode can be improved, and it has excellent comprehensive performance.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a polymer comprising a structural unit as shown in Formula I:

[0009]

[0010] Among them, A1 represents a flexible segment, Represents a conductive polymer segment.

[0011] Ring A2 is selected from at least one of a C6-C30 aromatic ring and a C4-C20 heteroaromatic ring, and at least one ring A2 is a fluorene ring.

[0012] R is selected from at least one of a hydrogen atom, a C1-C20 straight-chain or branched-chain alkyl group substituted by R', -C(=O)OM1, a C1-C20 straight-chain or branched-chain alkoxy group substituted by R', and -M2-CO-NH-M3.

[0013] M2 is selected from any one of a methylene group and an ethylene group, which may or may not be substituted by R'.

[0014] M3 is selected from any one of a C1-C20 straight-chain alkyl group, which may or may not be substituted by R'; one or at least two non-adjacent -CH2- groups in the C1-C20 straight-chain alkyl group are each independently replaced by -O- or not.

[0015] In the present invention, one or at least two non-adjacent -CH2- groups in the C1-C20 straight-chain alkyl group are each independently replaced by -O- or not. Exemplarily, when one -CH2- in -CH2-CH2-CH3 is replaced by -O-, -O-CH2-CH3 or -CH2-O-CH3 is obtained.

[0016] R' is selected from at least one of -C(=O)OQ1, -OH, and -NH2.

[0017] M1 and Q1 are each independently selected from H, Li, or Na.

[0018] The polymer contains at least one -C(=O)OLi and / or at least one -C(=O)ONa; -C(=O)OLi and -C(=O)ONa may be R or a substituent R' of R.

[0019] In the present invention, when R appears, the number of R can be one or more (at least two), and R can be connected to any position where A2 can be connected.

[0020] The structures of J1 and J2 are each independently

[0021] R1 is selected from any one of a C6-C20 arylene group and a C4-C20 heteroarylene group.

[0022] R2 is selected from any one of a C1-C10 straight-chain alkylene group, which may or may not be substituted by R", and a C2-C10 straight-chain alkoxy group, which may or may not be substituted by R".

[0023] R" is each independently selected from a hydroxyl group or a carboxyl group.

[0024] R3 is selected from any one of -CO-NH-, -O-, -NH-.

[0025] z is 0 or 1. When z is 0, R1 and R3 are directly connected by a single bond.

[0026] m is selected from integers from 5 to 100, such as 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100, etc.

[0027] n is selected from integers from 2 to 30, such as 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.

[0028] In the polymer provided by the present invention, the conductive polymer segments and the flexible segments alternate. The conductive polymer segments are rigid segments, and the main chain of the conductive polymer segments has an electronic conduction function, and the side groups contain polar groups; when used as a battery binder, the polar groups contained in the side groups can provide adhesion ability and can form strong interactions with battery active materials. Relying on these strong interactions, a stable conductive network can be formed, ensuring the integrity of the electrode structure and the integrity of the electronic conduction network during the charge and discharge process of the battery, and enabling stable cycling of the negative electrode material; the flexible segments can improve the mechanical properties of the binder, avoid excessive brittleness of the electrode sheet, and improve the toughness and processability of the electrode sheet. Compared with the rigid pure conductive polymer binder, the polymer provided by the present invention solves the problem of poor toughness of the traditional conductive binder for electrode sheets.

[0029] In the present invention, each of the C6-C30 can independently be C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, C20, C22, C24, C26, C28, etc.

[0030] Each of the C6-C20 can independently be C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, etc.

[0031] Each of the C4-C20 can independently be C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, etc.

[0032] Each of the C1-C20 can independently be C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C12, C14, C16, C18, etc.

[0033] Each of the C2-C10 can independently be C3, C4, C5, C6, C7, C8, C9, etc.

[0034] The C1-C10 can each independently be C2, C3, C4, C5, C6, C7, C8, C9, etc.

[0035] The C6-C30 (e.g., C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, C20, C22, C24, C26, C28) aromatic ring (aryl group), further preferably C6-C20 (e.g., C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, C20) aromatic ring (aryl group), exemplarily include but are not limited to: a benzene ring, a biphenyl ring, a terphenyl ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, an indene ring, a fluorene ring, a spirobifluorene ring, a benzofluorene ring, a fluoranthene ring, a triphenylene ring, a pyrene ring, a perylene ring, Ring, tetracene ring or triphenylene ring, etc.

[0036] The C6-C20 arylene group is a divalent group obtained by removing a hydrogen atom from the above C6-C20 (e.g., C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, etc.) aryl group.

[0037] The heteroatoms of the heteroaromatic ring (heteroaryl) in the present invention include but are not limited to O, S, N, P or B. The heteroaromatic ring (heteroaryl) may be a monocyclic heteroaromatic ring or a condensed heteroaromatic ring. The C4-C20 (e.g., C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, C20) heteroaromatic ring, and more preferably a C4-C15 (e.g., C6, C8, C9, C10, C12) heteroaromatic ring, exemplarily include but are not limited to: quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, cinnoline ring, o-phenanthroline ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, benzofuran ring, benzothiophene ring, indole ring, dibenzofuran ring, dibenzothiophene ring, carbazole ring, phenothiazine ring, phenoxazine ring, hydroacridine ring, etc.

[0038] The C4-C20 heteroarylene group is a divalent group obtained by removing a hydrogen atom from the above-mentioned C4-C20 (e.g., C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, etc.) heteroaryl group.

[0039] The C1-C20 straight or branched chain alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, n-octyl, n-heptyl, n-nonyl, n-decyl, and the like.

[0040] Specific examples of the C1-C20 straight or branched alkoxy group include monovalent groups obtained by connecting O to the above-mentioned straight or branched alkyl groups.

[0041] The C1-C10 linear alkylene group includes methylene, ethylene, n-propylene, n-butylene, n-pentylene, n-hexylene, n-octylene, n-heptylene, n-nonylene, n-decylene, etc.

[0042] Specific examples of the C2-C10 linear alkoxy group are divalent groups obtained by connecting the examples of the above-mentioned C2-C10 linear alkylene groups with O.

[0043] In the present invention, the group of "R' substituted or unsubstituted" may be substituted with one substituent R' or may be substituted with a plurality of substituents R'. When there are a plurality of (at least two) substituents R', they may be the same or different substituents; when the same expression is involved below, it has the same meaning.

[0044] In the present invention, the expression of the ring structure with a "-" drawn indicates that the connection site is at any position on the ring structure where bonding can occur.

[0045] In the present invention, the expression of Ca-Cb represents that the group has a carbon atom number of a-b. Without special instructions, the carbon atom number does not include the carbon atom number of the substituent.

[0046] In the present invention, "independently of each other" means that when the subject has a plurality of them, they may be the same or different from each other.

[0047] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved.

[0048] As a preferred technical solution, the flexible segment includes at least one of linear aliphatic segments of C6-C50.

[0049] The C6-C50 may independently be C6, C8, C9, C10, C12, C13, C14, C15, C16, C18, C20, C22, C24, C26, C28, C30, C35, C40, C45 or C48, etc.

[0050] Preferably, the flexible segment is a linear hydrocarbon compound segment and its derivative segment.

[0051] Preferably, the flexible segment includes at least one of C6-C50 linear alkylene groups substituted or unsubstituted with R'''; where * represents the connection site of the group; R''' is selected from at least one of hydroxyl, carboxyl, cyano or amino.

[0052] t is an integer selected from 2 to 24, and can be, for example, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, etc.

[0053] Preferably, the ring A2 is selected from at least one of C6-C20 (such as C9, C10, C12, C14, C16, C18, etc.) aromatic rings and C4-C15 (such as C5, C6, C9, C10, C12, C14, etc.) heteroaromatic rings, and at least one ring A2 is a fluorene ring.

[0054] Preferably, the ring A2 is a fluorene ring.

[0055] Preferably, R is selected from at least one of a hydrogen atom, a C1-C5 straight-chain or branched-chain alkyl group substituted by -C(=O)OL1, -C(=O)OL2, and -L3-CO-NH-L4.

[0056] L1 and L2 are each independently selected from H, Li, or Na.

[0057] L3 is selected from a methylene group or an ethylene group.

[0058] L4 is selected from any one of C1-C10 straight-chain alkyl groups substituted by -NH2; one or at least two non-adjacent -CH2- in the C1-C10 straight-chain alkyl group are each independently replaced by -O- or not.

[0059] Preferably, the conductive polymer segment includes at least one of the structures shown in Formula I-1 or a combination of at least one of the structures shown in Formula I-1 and at least one of the structures shown in Formula I-2, Formula I-3, Formula I-4, Formula I-5, and Formula I-6:

[0060]

[0061] Among them, the dotted line represents the connection site of the group.

[0062] R 11 、R 12 are each independently selected from any one of -CH2-CH2-C(=O)OZ1, -CH2-C(=O)OZ2, and -Z4-CO-NH-Z5.

[0063] Z1, Z2, and Z3 are each independently selected from H, Li, or Na.

[0064] Z4 is selected from a methylene group or an ethylene group.

[0065] Z5 is selected from any one of C1-C10 straight-chain alkyl groups substituted by -NH2; one or at least two non-adjacent -CH2- in the C1-C10 straight-chain alkyl group are each independently replaced by -O- or not.

[0066] The conductive polymer segment is a water-soluble polymer segment; the conductive polymer segment being a water-soluble polymer segment enables the dispersion of the polymer in water, ensures its adhesion when used as a binder, and at the same time enables the rapid transfer of electrons from the conductive network to the surface of the electrode active particles.

[0067] Preferably, the R1 is a phenylene group.

[0068] Preferably, the R2 is selected from any one of C1-C5 (such as C2, C3 or C4) linear alkylene groups.

[0069] Preferably, the R3 is -CO-NH-.

[0070] Preferably, the sum of the number-average molecular weights of the conductive polymer segments in the polymer is 6000-200000, for example, it can be 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 100000, 110000, 120000, 130000, 140000, 150000, 160000, 170000, 180000, 190000, etc.

[0071] Preferably, the number-average molecular weight of each conductive polymer segment in the polymer is independently 3000-20000, for example, it can be 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, etc.

[0072] In the present invention, each conductive polymer segment in the polymer means all the constituent segments in a repeating unit, and the same applies to the following "single conductive polymer segment".

[0073] Preferably, the mass ratio of the single conductive polymer segment to the single flexible segment in the polymer is (2-50):1, for example, it can be 2:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, etc.

[0074] The mass ratio of the conductive polymer segment to the flexible segment directly affects the properties of the polymer such as adhesion, electronic conductivity, and flexibility; generally speaking, as the proportion of the conductive polymer segment increases, its adhesion increases, conductivity increases, but flexibility decreases.

[0075] Preferably, the dispersity index of the polymer is 1.1 - 3, and can be, for example, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.5, 2.6, 2.8 or 3, etc.

[0076] Preferably, the polymer includes any one of the following polymers:

[0077]

[0078]

[0079] wherein, t1, t2, t3 represent the molar fractions of each unit, and t1 + t 21 + t3 = 1.

[0080] t1 is 0.02 - 0.3, and can be, for example, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28.

[0081] t2 is 0.7 - 0.98, and can be, for example, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, etc.

[0082] t3 is 0 - 0.28, and can be, for example, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, etc.

[0083] n is selected from integers of 2 - 15, and can be, for example, 3, 5, 7, 9, 10, 11, 12, 13, etc.

[0084] q is selected from integers of 2 - 24, and can be, for example, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, etc.

[0085] Ar is selected from any one of them; the dashed line represents the connection site of the group.

[0086] Preferably, the polymer includes any one of the following polymers:

[0087]

[0088]

[0089] wherein, the numerical values in each polymer represent the molar fractions of each unit.

[0090] m is selected from integers from 6 to 12, and can be, for example, 7, 8, 9, 10, or 11.

[0091] n is selected from integers from 2 to 8, and can be, for example, 3, 4, 5, 6, or 7.

[0092] Exemplarily, the method for preparing the polymer includes the following steps:

[0093] (1) A substance having the structure shown in Formula II reacts with a substance having the structure shown in Formula III to obtain a substance having the structure shown in Formula IV, and the reaction formula is as follows:

[0094]

[0095] Among them, U1 is selected from any one of Cl, Br, I, ; U2 is selected from -C(=O)-Cl or amino group; U3 and U4 are each independently selected from an amino group or -C(=O)-Cl; where -* represents the connection site of the group;

[0096] When U2 is -C(=O)-Cl and U3 and U4 are amino groups, U2 can react with U3 and U4 respectively to form -CO-NH-, that is, R3;

[0097] When U2 is an amino group and U3 and U4 are -C(=O)-Cl, U2 can react with U3 and U4 respectively to form -CO-NH-, that is, R3; at this time, the preparation method of the substance shown in Formula III is as follows:

[0098] Oxalyl chloride reacts with HOOC-A1-COOH in a second reaction to obtain the substance shown in Formula III;

[0099] R1, R2, A1, J1, and J2 have the same defined ranges as in Formula I;

[0100] (2) The substance having the structure shown in Formula IV, the substance having the structure shown in Formula V, and the substance having the structure shown in Formula VI obtained in step (1) react to obtain a substance having the structure shown in Formula VII, and the reaction formula is as follows:

[0101]

[0102] Among them, X1 and X2 are each independently selected from at least one of a hydrogen atom, a C1-C20 straight-chain or branched-chain alkyl group substituted by R', -C(=O)OY1, a C1-C20 straight-chain or branched-chain alkoxy group substituted by R', and -M2-CO-NH-M3, and X1 and X2 are not simultaneously hydrogen atoms; R' is selected from at least one of -C(=O)OT1, -OH, and -NH2; Y1 and T1 are each independently selected from at least one of a tert-butyl group, a methyl group, an ethyl group, and a propyl group;

[0103] U5 and U6 are each independently selected from Br or I;

[0104] X represents X1 or X2;

[0105] Ring A2, M2, M3, m, and n have the same defined ranges as in Formula I;

[0106] (3) The substance having the structure shown in Formula VII obtained in step (2) is treated with trifluoroacetic acid and then mixed with an alkali metal salt solution for dialysis to obtain the polymer.

[0107] Preferably, the mass ratio of the substance having the structure shown in Formula II to the substance having the structure shown in Formula III is (2 - 5):1, and for example, it can be 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0108] Preferably, the first reaction in step (1) is carried out in the presence of triethylamine.

[0109] Preferably, based on the mass of the substance having the structure shown in Formula III being 1 g, the volume of the triethylamine is 0.2 - 8 mL, and for example, it can be 0.5 mL, 1 mL, 1.5 mL, 2 mL, 2.5 mL, 3 mL, 3.5 mL, 4 mL, 4.5 mL, 5 mL, 5.5 mL, 6 mL, 6.5 mL, 7 mL, 7.5 mL, etc.

[0110] Preferably, the time of the first reaction in step (1) is 1 - 72 h, and for example, it can be 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 70 h, etc.

[0111] Preferably, the temperature of the first reaction in step (1) is 0 - 70 °C, and for example, it can be 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, etc.

[0112] Preferably, the temperature of the second reaction in step (1) is room temperature.

[0113] Preferably, the time of the second reaction in step (1) is 1 - 72 h, and for example, it can be 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 70 h, etc.

[0114] Preferably, the molar ratio of the oxalyl chloride to HOOC-A1-COOH is (2-5):1, and can be, for example, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0115] Preferably, the molar ratio of the substance having the structure shown in Formula IV, the substance having the structure shown in Formula V, and the substance having the structure shown in Formula VI is 1:(1.7-25):(0.7-24).

[0116] Preferably, the raw materials for the reaction in step (2) further include an alkaline solution, a chain transfer agent, and a catalyst.

[0117] Preferably, the alkaline solution includes any one or a combination of at least two of aqueous Na2CO3 solution, aqueous K2CO3 solution, aqueous Li2CO3 solution, aqueous Cs2CO3 solution, aqueous K3PO4 solution, aqueous NaOH solution, aqueous Ba(OH)2 solution, or aqueous CsF solution.

[0118] Preferably, the concentration of the alkaline solution is 0.5-4 mol / L.

[0119] Preferably, the catalyst includes any one or a combination of at least two of tetrakis(triphenylphosphine)palladium, [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium, palladium acetate, bis(triphenylphosphine)dichloropalladium, or 1,3-bis(diphenylphosphinopropane)nickel dichloride.

[0120] Preferably, the chain transfer agent includes methyltrioctylammonium chloride.

[0121] Preferably, the reaction time in step (2) is 6-72 h, and can be, for example, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 70 h, etc.

[0122] Preferably, the reaction temperature in step (2) is 70-120 °C, and can be, for example, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, etc.

[0123] Preferably, the treatment time in step (3) is 0.2-72 h, and can be, for example, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 70 h, etc.

[0124] Preferably, the treatment temperature in step (3) is 0-45 °C, and can be, for example, 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, etc.

[0125] Preferably, the alkali metal salt solution includes an aqueous solution of Li2CO3 and / or an aqueous solution of LiOH.

[0126] Preferably, the concentration of the alkali metal salt solution is 0.5 - 4 mol / L, and for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, etc.

[0127] Preferably, dialysis is stopped when the pH value of the solution stabilizes at neutral.

[0128] In a second aspect, the present invention provides a battery slurry, and the battery slurry includes the polymer as described in the first aspect.

[0129] When the battery slurry using the polymer provided by the present invention is used for an electrode, it can simultaneously ensure high adhesion and certain electronic conductivity, and the prepared electrode has certain toughness at the same time; and it can enable electrons to quickly reach the active particles from the conductive network, reduce the electron transfer impedance of the battery, and at the same time solve the problem of difficult processing caused by the inherent brittleness of the rigid polymer.

[0130] Preferably, the solvent of the battery slurry is water. The polymer provided by the present invention has water solubility, so water can be used as the solvent to prepare the battery slurry.

[0131] Preferably, the mass percentage content of the polymer as described in the first aspect in the battery slurry is 0.1 - 20%, and for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, etc.

[0132] The polymer provided by the present invention is easy to be controllably prepared, can be used as a novel conductive binder for lithium - ion batteries and sodium - ion batteries, and can replace the conductive additives and traditional binders in lithium - ion batteries or sodium - ion batteries. In addition, the polymer provided by the present invention is not limited to high - capacity negative electrode materials, and can also be used in the positive and negative electrode sheets of ordinary batteries.

[0133] In a third aspect, the present invention provides a battery electrode sheet, and the battery electrode sheet includes the polymer as described in the first aspect.

[0134] The battery electrode provided by the present invention can be a positive electrode or a negative electrode, depending on the specific active material used. Moreover, according to the active material employed, the battery electrode provided by the present invention can be a lithium-ion battery electrode or a sodium-ion battery electrode. For example, when it is a lithium-ion battery electrode, the electrode at least includes a lithium-ion battery active material and the polymer provided by the present invention, and may contain other types of conductive additives and auxiliary binders, etc. Among them, the auxiliary binders are, for example, polyacrylic acid, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber, and other common binders. In the lithium-ion battery electrode, the polymer provided by the present invention accounts for 0.1-20 wt% of the total mass of the battery electrode; again, for example, when it is a sodium-ion battery electrode, the electrode at least includes a sodium-ion battery active material and the polymer provided by the present invention, and may contain other conductive additives and auxiliary binders, etc. Among them, the auxiliary binders are, for example, polyacrylic acid, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber, and other common binders; in the sodium-ion battery electrode, the polymer provided by the present invention accounts for 0.1-20 wt% of the total mass of the battery electrode.

[0135] Whether it is a positive electrode or a negative electrode of a lithium-ion battery or a sodium-ion battery, it can refer to the prior art. It only needs to replace the binder therein with the polymer provided by the present invention, or rather, replace the binder and part of the conductive additives in the battery electrode with the polymer provided by the present invention.

[0136] The binder or battery slurry using the polymer provided by the present invention can not only reduce the internal resistance of the battery, improve the cycling stability of the battery electrode, but also improve the toughness and processability of the battery electrode.

[0137] In the fourth aspect, the present invention provides a battery, and the battery includes the polymer as described in the first aspect or the battery electrode as described in the third aspect.

[0138] The battery provided by the present invention can be a lithium-ion battery or a sodium-ion battery. Whether it is a lithium-ion battery or a sodium-ion battery, it can refer to the prior art. It only needs to replace the binder in its battery electrode with the polymer provided by the present invention, or replace part of the binder and conductive additives in the battery electrode with the polymer provided by the present invention.

[0139] For example, when it is a lithium-ion battery, it is composed of a lithium-ion battery negative electrode, a positive electrode, a separator, an electrolyte, and a casing; among them, the negative electrode and / or the positive electrode of the lithium-ion battery is formed by coating and drying a battery slurry prepared by mixing the polymer provided by the present invention and an active material; again, for example, when it is a sodium-ion battery, it is composed of a sodium-ion battery negative electrode, a positive electrode, a separator, an electrolyte, and a casing; among them, the negative electrode and / or the positive electrode of the sodium-ion battery is formed by coating and drying a battery slurry prepared by mixing the polymer provided by the present invention and an active material.

[0140] The battery slurry or battery electrode using the polymer provided by the present invention can reduce the impedance of the battery, increase the cycling stability of the negative electrode material, and at the same time has a certain toughness, avoiding the cracking of the electrode.

[0141] Compared with the prior art, the present invention has the following beneficial effects:

[0142] (1) The polymer provided by the present invention has two parts: a rigid segment that conducts electrons and a flexible segment that does not conduct electricity. While having the ability of electronic conductivity, it also has a certain degree of flexibility; the side groups of the conductive polymer segment have polar groups, which can form strong interactions with the hydroxyl groups on the surface of the negative electrode material, thereby maintaining the electrical connection and integrity of the electrode, and at the same time forming a stable conductive network;

[0143] (2) Using the polymer provided by the present invention as a binder, the flexible segment can endow the binder with a certain degree of flexibility, enabling the electrode to ensure a certain toughness and avoiding the cracking of the electrode; when used for the negative electrode of a lithium-ion battery, it can reduce the impedance of the battery, increase the cycling stability of the negative electrode material, and can better cope with the stress of the negative electrode sheet and maintain the mechanical integrity of the electrode;

[0144] (3) The polymer provided by the present invention is easy to produce on a large scale and has water solubility, and can be used as a novel conductive binder for lithium-ion batteries and sodium-ion batteries;

[0145] (4) For the battery using the polymer provided by the present invention as a binder, after 100 charge-discharge cycles at a rate of 0.2C, the capacity retention rate is 75.2 - 82.1%. Specific Embodiments

[0146] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0147] The sources of some components in the examples and comparative examples are as follows:

[0148] (1) Polyethylene glycol dicarboxylic acid: purchased from Aladdin, product number: P136309, CAS number: 39927 - 08 - 7, with an average molecular weight of 600;

[0149] (2) Monomers M1 and M2: Reference A. Water-Soluble Conjugated Polymer with Pendant Disulfide Linkages to PEG Chains: A Highly Efficient Ratiometric Probe with Solubility-Induced Fluorescence Conversion for Thiol Detection [J]. Li J, et al. Macromolecules, 2015, 48(4). Synthesis;

[0150] Among them, the structure of monomer M1 is The structure of monomer M2 is

[0151] In the present invention, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer are determined by gel permeation chromatography (GPC), based on polystyrene calibration. The specific determination and calculation methods are well-known to those skilled in the art and will not be elaborated here; PDI = Mw / Mn.

[0152] In the following examples, the molar fractions of each unit in the polymer are calculated according to the feeding amounts.

[0153] Example 1

[0154] A polymer, the polymer comprising the following structural units:

[0155]

[0156] Among them, the numerical values 0.05 and 0.95 are the molar fractions of each unit respectively;

[0157] The preparation method of the polymer comprises the following steps:

[0158] (1) Add 2 g of 1,12-diaminododecane and 3 mL of anhydrous triethylamine to anhydrous DMF, add 4.8 g of p-bromobenzoyl chloride, react at 25 °C for 2 h, then remove the solvent to obtain B1, wash and dry for standby. The structure of B1 is as follows:

[0159]

[0160] (2) Add approximately 2 mmol of B1 to 500 mL of tetrahydrofuran. Subsequently, add 18 mmol of monomer M1 and 20 mmol of monomer M2 to the above-mentioned tetrahydrofuran dispersion for dissolution. Then, add 150 mL of 2 M aqueous Na2CO3 solution and 150 μL of the chain transfer agent methyltrioctylammonium chloride (Aliquant 336). Subject the resulting solution to three cycles of freeze-pump-thaw degassing, and then add 100 mg of tetrakis(triphenylphosphine)palladium under nitrogen protection. Heat the mixture under reflux at 90 °C for 72 h and then cool it to room temperature. Pour the resulting solution into methanol for precipitation and filtration. Dissolve the precipitate in dichloromethane, and then precipitate it again in methanol. Repeat this process three times to obtain the intermediate mid-P1. The reaction scheme is as follows:

[0161]

[0162] (3) Add 5 g of the intermediate mid-P1 obtained in step (2) to 150 g of a dichloromethane solution containing 20 wt% trifluoroacetic acid. Stir the mixture overnight at 25 °C. Subsequently, rotary evaporate to remove the excess solvent, wash three times with methanol, dissolve it in 100 mL of 1 M aqueous Li2CO3 solution, and dialyze until the pH value stabilizes at neutral to obtain the polymer with a number-average molecular weight of 39,000 and a dispersity index of 1.4. The reaction scheme is as follows:

[0163]

[0164] Example 2

[0165] A polymer, which comprises the following structural units:

[0166]

[0167] wherein the numerical values 0.05 and 0.95 are the molar fractions of each unit respectively;

[0168] The preparation method of the polymer comprises the following steps:

[0169] (1) Add 2 g of polyethylene glycol dicarboxylic acid to dichloromethane, add 1 g of oxalyl chloride, stir at room temperature for 2 h, and then remove the solvent. Redissolve 0.6 g of the resulting solid in anhydrous dichloromethane, add 2 mL of triethylamine, add 1.5 g of p-bromo phenethylamine under ice bath, and react at room temperature for 2 h. Obtain B2 by column chromatography for standby use. The structure of B2 is as follows:

[0170]

[0171] (2) Add approximately 2 mmol of B2 to 500 mL of tetrahydrofuran. Subsequently, add 18 mmol of monomer M1 and 20 mmol of monomer M2 to the above-mentioned tetrahydrofuran dispersion for dissolution. Then, add 150 mL of 2M aqueous Na2CO3 solution and 150 μL of chain transfer agent Aliquant 336. Freeze-dry the resulting solution three times to remove oxygen, and then add 100 mg of tetrakis(triphenylphosphine)palladium under nitrogen protection. Heat the mixture under reflux at 90 °C for 72 h and cool it to room temperature. Pour the resulting solution into methanol for precipitation and filtration, dissolve it in dichloromethane, and then precipitate it again in methanol. Repeat this process three times to obtain intermediate mid-P2. The reaction formula is as follows:

[0172]

[0173]

[0174] (3) Add 5 g of the intermediate mid-P2 obtained in step (2) to 150 g of a dichloromethane solution containing 20 wt% trifluoroacetic acid, and stir overnight at 25 °C. Subsequently, rotary evaporate to remove the excess solvent, wash three times with methanol, dissolve it in 100 mL of 1M aqueous Li2CO3 solution, and dialyze until the pH value stabilizes at neutral to obtain the polymer with a number-average molecular weight of 55,000 and a dispersity index of 1.6. The reaction formula is as follows:

[0175]

[0176] Example 3

[0177] A polymer, which comprises the following structural units:

[0178]

[0179] Among them, the numerical values 0.05, 0.85, and 0.1 are the molar fractions of each unit respectively;

[0180] The preparation method of the polymer comprises the following steps:

[0181] (1) This step is the same as step (1) of Example 2;

[0182] (2) Add approximately 2 mmol of B2 to 500 mL of tetrahydrofuran. Subsequently, add 14 mmol of monomer M1, 4 mmol of p-dibromobenzene, and 20 mmol of monomer M2 to the above-mentioned tetrahydrofuran dispersion for dissolution. Then, add 150 mL of 2 M aqueous Na2CO3 solution and 150 μL of chain transfer agent Aliquant 336. Freeze-dry the resulting solution three times to remove oxygen, and then add 100 mg of tetrakis(triphenylphosphine)palladium under nitrogen protection. Heat the mixture under reflux at 90 °C for 72 h, and then cool it to room temperature. Pour the resulting solution into methanol for precipitation and filtration, dissolve it in dichloromethane, and then precipitate it again in methanol. Repeat this process three times to obtain intermediate mid-P3. The reaction formula is as follows:

[0183]

[0184] (3) Add 5 g of the intermediate mid-P3 obtained in step (2) to 100 g of a dichloromethane solution containing 20 wt% trifluoroacetic acid, and stir overnight at 25 °C. Subsequently, rotary evaporate to remove the excess solvent, wash three times with methanol, dissolve it in 200 mL of 1 M aqueous Li2CO3 solution, and dialyze until the pH value stabilizes at neutral to obtain the polymer with a number-average molecular weight of 31,500 and a dispersity index of 2.4. The reaction formula is as follows:

[0185]

[0186]

[0187] Example 4

[0188] A polymer, the polymer comprising the following structural units:

[0189]

[0190] Among them, the numerical values 0.05, 0.85, and 0.1 are the molar fractions of each unit respectively;

[0191] The preparation method of the polymer comprises the following steps:

[0192] (1) This step is the same as step (1) of Example 2;

[0193] (2) Add about 2 mmol of B2 to 500 mL of tetrahydrofuran. Subsequently, add 14 mmol of monomer M1, 4 mmol of 2,7-dibromophenanthraquinone, and 20 mmol of monomer M2 to the above-mentioned tetrahydrofuran dispersion for dissolution. Then add 150 mL of 2M aqueous Na2CO3 solution and 150 μL of chain transfer agent Aliquant 336. Freeze-dry the resulting solution under vacuum three times to remove oxygen, and then add 100 mg of tetrakis(triphenylphosphine)palladium under nitrogen protection. Heat the mixture under reflux at 90 °C for 72 h, and then cool it to room temperature. Pour the resulting solution into methanol for precipitation and filtration, dissolve it in dichloromethane, and then precipitate it again in methanol. Repeat this process three times to obtain intermediate mid-P4. The reaction formula is as follows:

[0194]

[0195]

[0196] (3) Add 5 g of the intermediate mid-P4 obtained in step (2) to 120 g of a dichloromethane solution containing 20 wt% trifluoroacetic acid, and stir overnight at 35 °C. Then rotary evaporate to remove the excess solvent, wash it three times with methanol, dissolve it in 150 mL of 1M aqueous Li2CO3 solution, and dialyze until the pH value stabilizes at neutral to obtain the polymer. The number-average molecular weight is 39000, and the dispersity index is 2.6. The reaction formula is as follows:

[0197]

[0198] Example 5

[0199] A polymer, the polymer comprises the following structural units:

[0200]

[0201] Among them, the numerical values 0.1, 0.85, and 0.05 are the molar fractions of each unit respectively;

[0202] The preparation method of the polymer is only different from that of Example 4 in that the amount of B2 used in step (2) is 4 mmol, the amount of monomer M1 used is 14 mmol, the amount of 2,7-dibromophenanthraquinone used is 2 mmol, and the amount of monomer M2 used is 20 mmol. The other raw materials, process parameters, and steps are the same as those in Example 4. The number-average molecular weight of the polymer is 38000, and the dispersity index is 2.3.

[0203] Comparative Example 1

[0204] A polymer PF-COOLi, the polymer PF-COOLi comprises the following structural units:

[0205]

[0206] The preparation method of the polymer PF-COOLi comprises the following steps:

[0207] (1) 20 mmol of monomer M1 and 20 mmol of monomer M2 are added to 500 mL of a tetrahydrofuran dispersion for dissolution; subsequently, 150 mL of a 2M Na2CO3 aqueous solution is added, and 150 μL of a chain transfer agent Aliquant336 is added; the resulting solution is degassed by three cycles of freezing and evacuation, and then 100 mg of tetrakis(triphenylphosphine)palladium is added under nitrogen protection, and the mixture is heated under reflux at 90 °C for 72 h and then cooled to room temperature; the resulting solution is poured into methanol for precipitation and filtration, dissolved in dichloromethane, and then precipitated again in methanol, and the filtration process is repeated three times to obtain the intermediate PF-COOBu. The reaction formula is as follows:

[0208]

[0209] (2) 5 g of the intermediate PF-COOBu obtained in step (1) is added to 120 g of a dichloromethane solution containing 20 wt% trifluoroacetic acid, and the mixture is stirred overnight at 35 °C; subsequently, the excess solvent is removed by rotary evaporation, washed three times with methanol, dissolved in 150 mL of a 1M Li2CO3 aqueous solution, and dialyzed until the pH value is stable at neutral to obtain the polymer PF-COOLi with a number average molecular weight of 21,000 and a dispersity index of 1.6. The reaction formula is as follows:

[0210]

[0211] Performance testing

[0212] Preparation of the electrode sheet:

[0213] 60.0 mg of the polymers provided in Experimental Examples 1-5 and Comparative Example 1 are respectively dissolved in deionized water to prepare 5 wt% aqueous solutions, 140 mg of silicon nanoparticles (80-100 nm) are added thereto and stirred and mixed, and after high-speed mixing for 4 h, a negative electrode slurry is obtained, which is uniformly coated on a copper foil with a coating thickness of 200 μm. After air drying at room temperature for 24 h, it is placed in a forced-air drying oven and baked at 80 °C for 8 h, and then baked in a vacuum oven at 120 °C for 4 h. Then, the dried electrode sheets are rolled and cut to prepare electrode sheets A, B, C, D, E, and F;

[0214] Dissolve 30 mg of PAA (purchased from Aladdin, molecular weight 450,000, product number: P104272) in deionized water to prepare a 5 wt% aqueous solution. Add 30 mg of conductive carbon (Timcal Super P Li, a highly conductive carbon black) and 140 mg of silicon nanoparticles (80 - 100 nm) to it. After high-speed mixing for 4 h, a negative electrode slurry is obtained. Use a scraper to evenly coat it onto a copper foil with a coating thickness of 200 μm. After air-drying at room temperature for 24 h, place it in a forced-air drying oven and bake at 80 °C for 8 h. Subsequently, bake it in a vacuum oven at 120 °C for 4 h. Then roll and cut the dried electrode sheet to prepare electrode sheet G.

[0215] Button cell assembly: Assemble the above electrode sheets (A - G), Celgard 2500 separator, lithium sheet, and 1.2 mol / L LiPF6 electrolyte (the solvent is a 1:1 volume ratio of diethyl carbonate (DEC) and ethylene carbonate (EC), and fluoroethylene carbonate FEC is added as an additive at 10 wt% of the total mass of the electrolyte) into 2032 button cells respectively.

[0216] 2032 button cell test: The test temperature is 25 °C, and the voltage working range is 0.005 - 2 V. The battery is first activated for 5 cycles at a rate of 0.05 C, and then undergoes 100 charge-discharge cycles at a rate of 0.2 C. The test results are shown in Table 1:

[0217] Table 1

[0218]

[0219] From the test data in Table 1, it can be seen that when using the polymer provided by the present invention to replace the conductive additive and traditional binder in a lithium-ion battery, the conductive polymer segments not only provide a binding effect but also serve as a bridge for electron transport, ensuring the integrity of the conductive structure of the electrode material during charge and discharge. The flexible segments endow the binder with a certain degree of flexibility, enabling the electrode to have a certain toughness, effectively coping with the stress changes of the silicon negative electrode and reducing the performance degradation caused by the volume change of the silicon negative electrode. Therefore, when the polymer provided by the present invention is applied to the negative electrode of a lithium-ion battery, it can maintain the mechanical integrity of the electrode, reduce the impedance of the battery, increase the cycle stability of the negative electrode material, and has more excellent technical effects.

[0220] The applicant declares that the present invention uses the above embodiments to illustrate the polymer of the present invention and its application, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A polymer, characterized in that, The polymer comprises a structural unit represented by Formula I: Among them, A1 represents a flexible chain segment, represents a conductive polymer chain segment; Ring A2 is selected from at least one of a C6-C30 aromatic ring and a C4-C20 heteroaromatic ring, and at least one ring A2 is a fluorene ring; R is selected from at least one of a hydrogen atom, a C1-C20 linear or branched alkyl group substituted by R', -C(=O)OM1, a C1-C20 linear or branched alkoxy group substituted by R', -M2-CO-NH-M3; M2 is selected from any one of a methylene group and an ethylene group, which may or may not be substituted by R'; M3 is selected from any one of a C1-C20 linear alkyl group, which may or may not be substituted by R'; one or at least two non-adjacent -CH2- groups in the C1-C20 linear alkyl group are independently replaced by -O- or not; R' is selected from at least one of -C(=O)OQ1, -OH, -NH2; M1 and Q1 are independently selected from H, Li or Na; The polymer contains at least one -C(=O)OLi and / or at least one -C(=O)ONa; The structures of J1 and J2 are each independently R1 is selected from any one of a C6-C20 arylene group and a C4-C20 heteroarylene group; R2 is selected from any one of a C1-C10 linear alkylene group, which may or may not be substituted by R", and a C2-C10 linear alkoxy group, which may or may not be substituted by R"; R" is independently selected from a hydroxyl group or a carboxyl group; R3 is selected from any one of -CO-NH-, -O-, -NH-; z is 0 or 1; m is an integer selected from 5 to 100; n is an integer selected from 2 to 30.

2. The polymer according to claim 1, wherein The flexible chain segment comprises at least one of a C6-C50 linear aliphatic chain segment; Preferably, the flexible chain segment includes at least one of a C6-C50 linear alkylene group which is substituted or unsubstituted by R”'; Wherein, * represents the connection site of the group; t is an integer selected from 2 to 24; R''' is selected from at least one of a hydroxyl group, a carboxyl group, a cyano group or an amino group.

3. The polymer according to claim 1 or 2, characterized in that, Ring A2 is selected from at least one of a C6-C20 aromatic ring and a C4-C15 heteroaromatic ring, and at least one ring A2 is a fluorene ring; Preferably, the ring A2 is a fluorene ring; Preferably, R is selected from at least one of a hydrogen atom, a C1-C5 linear or branched alkyl group substituted by -C(=O)OL1, -C(=O)OL2, -L3-CO-NH-L4; L1 and L2 are independently selected from H, Li or Na; L3 is selected from a methylene group or an ethylene group; L4 is selected from any one of a C1-C10 linear alkyl group substituted by -NH2; one or at least two non-adjacent -CH2- groups in the C1-C10 linear alkyl group are independently replaced by -O- or not.

4. The polymer according to any one of claims 1-3, characterized in that The conductive polymer chain segment comprises at least one of the structures represented by Formula I-1 or a combination of at least one of the structures represented by Formula I-1 and at least one of the structures represented by Formula I-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6: Wherein, the dotted line represents the connection site of the group; R 11 、R 12 each independently selected from any one of -CH2-CH2-C(=O)OZ1, -CH2-C(=O)OZ2, -Z4-CO-NH-Z5; Z1, Z2, Z3 are independently selected from H, Li or Na; Z4 is selected from a methylene group or an ethylene group; Z5 is selected from any one of a C1-C10 linear alkyl group substituted by -NH2; one or at least two non-adjacent -CH2- groups in the C1-C10 linear alkyl group are independently replaced by -O- or not.

5. The polymer according to any one of claims 1-4, characterized in that, The R1 is a phenylene group; Preferably, R2 is selected from any one of C1-C5 linear alkylene groups; Preferably, R3 is -CO-NH-.

6. The polymer according to any one of claims 1-5, characterized in that, The sum of the number-average molecular weights of the conductive polymer segments in the polymer is 6,000-200,000; Preferably, the number-average molecular weight of each conductive polymer segment in the polymer is independently 3,000-20,000; Preferably, the mass ratio of a single conductive polymer segment to a single flexible segment in the polymer is (2-50):1; Preferably, the dispersity index of the polymer is 1.1-3; Preferably, the polymer includes any one of the following polymers: Wherein, t1, t2, and t3 represent the molar fractions of each unit, and t1 + t2 + t3 = 1; t1 is 0.02-0.3; t2 is 0.7-0.98; t3 is 0-0.28; n is an integer selected from 2-15; q is an integer selected from 2-24; Ar is selected from any one of; the dashed line represents the connection site of the group; Preferably, the polymer includes any one of the following polymers: Wherein, the values in each polymer represent the molar fractions of each unit; m is an integer selected from 6-12, and n is an integer selected from 2-8.

7. A battery paste, characterized in that, The battery slurry includes the polymer according to any one of claims 1-6.

8. The battery paste according to claim 7, wherein The solvent of the battery slurry is water; Preferably, the mass percentage content of the polymer according to any one of claims 1-6 in the battery slurry is 0.1-20%.

9. A battery electrode plate, characterized in that, The battery electrode sheet includes the polymer according to any one of claims 1-6.

10. A battery, characterized in that, The battery includes the polymer according to any one of claims 1-6 or the battery electrode sheet according to claim 9.

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