An additive, a preparation method and use thereof, and a positive electrode sheet and a preparation method thereof

Abstract

The present application relates to an additive having the general structure I, wherein R 1 and R 2 are independently of each other hydrogen or C1-C 12 alkyl; R 3 and R 4 are independently of each other hydrogen, halogen or C1-C 12 alkyl; R 5 is hydrogen or C1-C 12 alkyl; R 6 is a 4-20 membered nitrogen-containing heterocyclyl group which is unsubstituted or substituted by a substituent, or a 5-20 membered nitrogen-containing heteroaryl group which is unsubstituted or substituted by a substituent, the substituent being halogen, hydroxyl, primary amino, secondary amino, C1-C 12 alkyl or C1-C 12 alkoxy; m is an integer from 1000 to 10000; n is an integer from 10 to 1000. In the additive of the present application, the group R 6 is a nitrogen-containing heterocyclyl group or a nitrogen-containing heteroaryl group, in which the nitrogen atom has a lone pair of electrons, which can form a strong adsorption to HF in the battery, thereby fixing the HF and avoiding its destruction of the passivation layer on the surface of the positive current collector, so that the corrosion of the positive current collector such as aluminum foil can be greatly alleviated, and the service life of the battery can be prolonged.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to an additive and its preparation method and use, a positive electrode sheet and its preparation method, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries have attracted much attention due to their high energy density, high capacity, good cycle stability, and excellent performance. However, after long-term use, the positive electrode current collector of lithium-ion batteries is prone to corrosion, which leads to battery capacity decay. In severe cases, it can even cause the electrode to break, puncture the separator, cause a short circuit, and result in a safety accident.

[0003] Therefore, there is an urgent need to develop an additive that can alleviate corrosion of the positive electrode current collector. Summary of the Invention

[0004] In view of the problems existing in the background art, this application provides an additive that can alleviate the corrosion of the positive current collector.

[0005] The additive provided in the first aspect of this application has the structure of general formula I:

[0006]

[0007] in,

[0008] R 1 and R 2 They are either hydrogen or C1-C independently of each other. 12 alkyl;

[0009] R 3 and R 4 They are independently hydrogen, halogen, or C1-C 12 alkyl;

[0010] R 5 It is hydrogen or C1-C 12 alkyl;

[0011] R 6 The substituent is a 4-20 member nitrogen-containing heterocyclic group that is either unsubstituted or substituted, or a 5-20 member nitrogen-containing heteroaryl group that is either unsubstituted or substituted, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, or C1-C. 12 Alkyl or C1-C 12 Alkoxy;

[0012] m is an integer between 1000 and 10000;

[0013] n is an integer from 10 to 1000.

[0014] In the technical solution of this application embodiment, the group R 6It is a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group, in which the nitrogen atom has a lone pair of electrons, which can form a strong adsorption of HF in the battery, thereby fixing HF and preventing it from damaging the passivation layer on the surface of the positive electrode current collector. This can greatly alleviate the corrosion of the positive electrode current collector, such as aluminum foil, and extend the battery's service life.

[0015] In addition, since HF in the battery can react with the positive electrode active material, causing loss of the positive electrode active material and a decrease in capacity, this additive can also improve the reversible capacity decay of the positive electrode active material and further extend the battery's service life.

[0016] In some embodiments, according to the first aspect, a first example of the first aspect is provided, wherein the 4-20 nucleotide nitrogen-containing heterocyclic group is a 4-nucleotide nitrogen-containing heterocyclic group, a 5-nucleotide nitrogen-containing heterocyclic group, or a 6-nucleotide nitrogen-containing heterocyclic group. The 5-20 nucleotide nitrogen-containing heteroaryl group is a 5-nucleotide nitrogen-containing heteroaryl group, a 6-nucleotide nitrogen-containing heteroaryl group, or a 5-14 nucleotide nitrogen-containing fused heteroaryl group.

[0017] In some embodiments, according to the first aspect, a second example of the first aspect is provided, wherein the 4-20 member nitrogen-containing heterocyclic group is azirropropyl, tetrahydropyrrolyl, pyrrolidone, or hexahydropyridinyl. The 5-20 member nitrogen-containing heteroaryl group is pyrrolyl, pyrazolyl, imidazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, tetrazolyl, pyridinyl, pyridinyl, pyridinyl, 1,3,5-triazinyl, quinolinyl, benzimidazolyl, or benzotriazolyl. These nitrogen-containing groups, due to their lone pair electrons, can combine with HF, thereby fixing HF and preventing damage to the passivation layer on the aluminum foil substrate surface by HF, greatly alleviating aluminum foil corrosion. Simultaneously, it also prevents HF from attacking the positive electrode material, reducing material loss in the positive electrode material, thus having a beneficial effect on the cell capacity retention rate.

[0018] In some embodiments, according to the first aspect, a third example of the first aspect is proposed, R 3 and R 4 Each is an independent halogen. In this design, by introducing halogen atoms, the adhesion properties of the additive can be improved, enabling it to adhere better to the surface of the positive electrode current collector, thereby fully exerting its corrosion inhibition effect.

[0019] In some embodiments, according to the first aspect, a fourth example of the first aspect is proposed, where m∶n=(10-1000)∶1. In this design, m represents the number of polymers of the unit that plays a bonding role (i.e., the unit containing F atoms), and n represents the number of polymers of the unit that can absorb HF (i.e., the unit containing nitrogen-containing heterocyclic groups). When the ratio of m to n is large, the additive has good adhesion to the electrode after being added to the undercoat, but its ability to absorb HF is weak, thus resulting in poor effects on inhibiting corrosion of the positive electrode current collector, reducing the loss of positive electrode active material by HF, and improving the cycle performance of the battery cell. When m / n is too small, the additive has poor adhesion to the electrode after being added to the undercoat and is easy to fall off, resulting in the inability to exert a corrosion inhibition effect. By controlling the ratio of the number of polymers of the two types of units in the molecular structure of the additive, the additive can exert its maximum corrosion inhibition effect.

[0020] In some embodiments, according to the first aspect, a fifth example of the first aspect is proposed, where m is an integer from 5000 to 10000; n is an integer from 50 to 500; and m∶n=(50-500)∶1. In this design, the corrosion inhibition effect of the additive can be further improved by adjusting m, n and their ratio.

[0021] In some embodiments, according to the first aspect, a sixth example of the first aspect is proposed, R 1 and R 2 Each is independently hydrogen or C1-C6 alkyl;

[0022] R 3 and R 4 Each of them is independently hydrogen, halogen, or C1-C6 alkyl;

[0023] R 5 It is hydrogen or C1-C6 alkyl;

[0024] R 6 The substituent is a tetrahydropyrrolyl group, an unsubstituted or substituted pyrrolidone group, an unsubstituted or substituted pyridyl group, an unsubstituted or substituted hexahydropyridyl group, or an unsubstituted or substituted imidazolyl group, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, C1-C6 alkyl, or C1-C6 alkoxy group.

[0025] m is an integer between 1000 and 10000;

[0026] n is an integer from 10 to 1000;

[0027] m∶n=(10-1000)∶1.

[0028] In this design, by optimizing group R 1 R 2 R 3 R 4R 5 R 6 The addition of , m, and n can further enhance the corrosion inhibition effect of the additives.

[0029] In some embodiments, according to the first aspect, a seventh example of the first aspect is proposed, R 1 and R 2 Each is hydrogen, independent of the others;

[0030] R 3 and R 4 Each is independently represented by F;

[0031] R 5 It is hydrogen or C1-C6 alkyl;

[0032] R 6 It is an unsubstituted or substituted tetrahydropyrrolidinyl, an unsubstituted or substituted pyrrolidinyl or an unsubstituted or substituted pyridyl, wherein the substituent is a C1-C6 alkyl group;

[0033] m is an integer between 1000 and 10000;

[0034] n is an integer from 10 to 1000;

[0035] m∶n=(10-1000)∶1.

[0036] In this design, the optimized group R is used. 1 R 2 R 3 R 4 R 5 R 6 Substituents, m, and n can further enhance the corrosion inhibition effect of additives.

[0037] A second aspect of this application provides a method for preparing an additive of general formula I, comprising the following steps:

[0038] In the presence of an initiator, the compound of formula II undergoes a polymerization reaction with the compound of formula III to obtain the additive of general formula I:

[0039]

[0040] in,

[0041] R 1 and R 2 They are either hydrogen or C1-C independently of each other. 12 alkyl;

[0042] R 3 and R 4 They are independently hydrogen, halogen, or C1-C 12 alkyl;

[0043] R 5 It is hydrogen or C1-C 12 alkyl;

[0044] R 6 The substituent is a 4-20 member nitrogen-containing heterocyclic group that is either unsubstituted or substituted, or a 5-20 member nitrogen-containing heteroaryl group that is either unsubstituted or substituted, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, or C1-C. 12 Alkyl or C1-C 12 Alkoxy;

[0045] m is an integer between 1000 and 10000;

[0046] n is an integer from 10 to 1000.

[0047] In the technical solution of this application embodiment, the additive of this application can be easily prepared by causing the compound of formula II to undergo a polymerization reaction with the compound of formula III.

[0048] In some embodiments, according to the second aspect, a first example of the second aspect is provided, wherein the molar ratio of compound II to compound III is (10-1000):1.

[0049] In this design, by adjusting the molar ratio of compound II to compound III, the ratio of m to n can be controlled, thereby optimizing the adhesive properties and HF absorption capacity of the additive.

[0050] In some embodiments, according to the second aspect, a second example of the second aspect is provided, wherein after the polymerization reaction is completed, the resulting crude product is precipitated in icy diethyl ether. In this design, by precipitating the crude product in icy diethyl ether, the product can be purified, thereby improving the product purity.

[0051] The third aspect of this application provides the use of the additive described in the first aspect of this application for mitigating corrosion of the positive current collector.

[0052] A fourth aspect of this application provides a positive electrode sheet comprising the additives described in the first aspect of this application.

[0053] In the technical solution of this application embodiment, since the additive of the first aspect of this application is used, the corrosion of the positive current collector in the positive electrode sheet of this application can be greatly alleviated, and the battery life can be effectively extended.

[0054] The fifth aspect of this application provides a method for preparing a positive electrode sheet, comprising:

[0055] The additives, conductive agents, and solvents described in the first aspect of this application are mixed, coated onto the positive electrode current collector, and dried to obtain a base coating; and

[0056] A positive electrode material layer is formed on the base coating.

[0057] In the technical solution of this application embodiment, by forming a base coating containing the additives of this application on the positive electrode current collector, and then forming a positive electrode material layer on the base coating, the HF in the battery can be effectively absorbed and fixed, reducing its corrosion of the positive electrode current collector and the loss of the positive electrode active material, and extending the battery life.

[0058] The sixth aspect of this application provides a lithium-ion battery, including the positive electrode sheet described in the fourth aspect of this application or the positive electrode sheet obtained according to the preparation method described in the fifth aspect of this application.

[0059] In the technical solution of this application embodiment, since the additive of the first aspect of this application is used, the corrosion of the positive electrode current collector in the lithium-ion battery of this application can be greatly alleviated, and the battery life can be effectively extended.

[0060] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0061] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0062] Figure 1 An electronic image of the positive electrode obtained after disassembling a lithium-ion battery corresponding to the additive in Example 1 after cycling.

[0063] Figure 2 Electronic images of the positive electrode obtained after disassembling the lithium-ion battery prepared for Comparative Example 1 after cycling.

[0064] Figure 3 for Figure 2 Longitudinal section view at point A (circle A). Detailed Implementation

[0065] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of this application.

[0066] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0067] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more (including two).

[0068] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are merely representative and should not be construed as exhaustive.

[0069] Lithium-ion batteries have attracted much attention due to their high energy density, high capacity, good cycle stability, and excellent performance. However, after long-term use, the positive electrode current collector of lithium-ion batteries is prone to corrosion, which leads to battery capacity decay and, in severe cases, even electrode breakage, puncture of the separator, short circuit, and safety accidents. Therefore, there is an urgent need to develop an additive that can mitigate the corrosion of the positive electrode current collector.

[0070] The inventors discovered that lithium salts in the electrolyte, such as LiTFSI or LiFSI, can be converted into HF through a series of reactions. HF can damage the passivation layer on the surface of the positive electrode current collector, thereby causing the positive electrode current collector to be corroded.

[0071] Through in-depth research, the inventors designed a polymer additive containing 4-20 nitrogen-containing heterocyclic groups. The nitrogen atoms in the additive have lone pairs of electrons, which can strongly adsorb HF in the battery, thereby fixing the HF and preventing it from damaging the passivation layer on the surface of the positive electrode current collector. This can greatly alleviate the corrosion of the positive electrode current collector, such as aluminum foil, and extend the battery's service life.

[0072] In addition, since HF in the battery can react with the positive electrode active material, causing loss of the positive electrode active material and a decrease in capacity, this additive can also improve the reversible capacity decay of the positive electrode active material and further extend the battery's service life.

[0073] Specifically, the first aspect of this application provides an additive having the structure of general formula I:

[0074]

[0075] in,

[0076] R 1 and R 2 They can be hydrogen or C1-C independently. 12 alkyl;

[0077] R 3 and R 4 They can be hydrogen, halogen, or C1-C independently. 12 alkyl;

[0078] R 5 It can be hydrogen or C1-C 12 alkyl;

[0079] R 6 The substituent is a 4-20 member nitrogen-containing heterocyclic group that is either unsubstituted or substituted, or a 5-20 member nitrogen-containing heteroaryl group that is either unsubstituted or substituted, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, or C1-C. 12 Alkyl or C1-C 12 Alkoxy;

[0080] M can be an integer from 1000 to 10000;

[0081] N can be an integer from 10 to 1000.

[0082] In some embodiments, according to the first aspect, a first example of the first aspect is provided, wherein the 4-20 nucleotide nitrogen-containing heterocyclic group may be a 4-nucleotide nitrogen-containing heterocyclic group, a 5-nucleotide nitrogen-containing heterocyclic group, or a 6-nucleotide nitrogen-containing heterocyclic group. The 5-20 nucleotide nitrogen-containing heteroaryl group may be a 5-nucleotide nitrogen-containing heteroaryl group, a 6-nucleotide nitrogen-containing heteroaryl group, or a 5-14 nucleotide nitrogen-containing fused heteroaryl group.

[0083] In some embodiments, according to the first aspect, a second example of the first aspect is provided, wherein the 4-20 member nitrogen-containing heterocyclic group is azirropropyl, tetrahydropyrrolyl, pyrrolidone, or hexahydropyridinyl. The 5-20 member nitrogen-containing heteroaryl group is pyrrolyl, pyrazolyl, imidazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, tetrazolyl, pyridinyl, pyridazinyl, pyrimidinyl, 1,3,5-triazinyl, quinolinyl, benzimidazolyl, or benzotriazolyl. These nitrogen-containing groups, due to their lone pair electrons, can combine with HF, thereby fixing HF and preventing damage to the passivation layer on the surface of the aluminum foil substrate by HF, greatly alleviating aluminum foil corrosion. Simultaneously, it also prevents HF from attacking the positive electrode material, reducing material loss in the positive electrode material, thus having a beneficial effect on the cell capacity retention rate.

[0084] Preferably, the 4-20 nitrogen-containing heterocyclic group can be tetrahydropyrrolidinyl, pyrrolidoneyl, or hexahydropyridinyl. More preferably, the 4-20 nitrogen-containing heterocyclic group can be tetrahydropyrrolidinyl or pyrrolidoneyl.

[0085] Preferably, the 5-20 nitrogen-containing heteroaryl group can be pyridyl or imidazolyl. More preferably, the 5-20 nitrogen-containing heteroaryl group can be pyridyl.

[0086] In some specific embodiments, the 4-20 member nitrogen-containing heterocyclic group may be one of the following structures:

[0087]

[0088] * indicates a site where it is linked to other groups.

[0089] In some specific embodiments, the 5-20 nitrogen-containing heteroaryl group may be one of the following structures:

[0090]

[0091] * indicates a site where it is linked to other groups.

[0092] Preferably, in the 4-20 member nitrogen-containing heterocyclic groups substituted with substituents and in the 5-20 member nitrogen-containing heteroaryl groups substituted with substituents, the substituents may be halogens, hydroxyl groups, primary amino groups, secondary amino groups, C1-C6 alkyl groups, or C1-C6 alkoxy groups. More preferably, the substituents may be C1-C6 alkyl groups.

[0093] In some embodiments, R 1 and R 2 They can be hydrogen or C1-C6 alkyl groups independently of each other.

[0094] In some embodiments, R 3 and R 4 They can be hydrogen, halogen, or C1-C6 alkyl, each independently of the other.

[0095] In some embodiments, according to the first aspect, a third example of the first aspect is proposed, R 3 and R 4 Each can be a halogen independently. In this design, by introducing halogen atoms, the adhesion properties of the additive can be improved, enabling it to adhere better to the surface of the positive electrode current collector, thereby fully exerting its corrosion inhibition effect.

[0096] Preferably, R 3 and R 4 Each atom can be F independently. Compared to other atoms (such as H) and groups, F atoms have stronger oxidation resistance, making the base coating less prone to aging and peeling after long-term cycling, thus improving the long-term reliability of the base coating and enabling it to perform better corrosion inhibition. Furthermore, R...3 and R 4 When all atoms are F atoms, the synthesis process of the additive is simple and the cost is low.

[0097] In some embodiments, R 5 It can be hydrogen or C1-C6 alkyl.

[0098] In some embodiments, m can be an integer from 5000 to 10000, for example, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900, 6000, 6100, 6200, 6300, 6400, 6500, 6600, 6700, 6800, 6900, 7000, 7100, 720 0, 7300, 7400, 7500, 7600, 7700, 7800, 7900, 8000, 8100, 8200, 8300, 8400, 8500, 8600, 8700, 8800, 8900, 9000, 9100, 9200, 9300, 9400, 9500, 9600, 9700, 9800, 9900, or 10000.

[0099] In some embodiments, n can be an integer from 50 to 500, for example, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 or 500.

[0100] In some embodiments, according to the first aspect, a fourth example of the first aspect is proposed, where m∶n=(10-1000)∶1. Preferably, m∶n=(50-500)∶1. More preferably, m∶n=(50-200)∶1. In this design, m represents the number of polymerization units that play a bonding role (i.e., units containing F atoms), and n represents the number of polymerization units that can absorb HF (i.e., units containing nitrogen-containing heterocyclic groups). When the ratio of m to n is large, the additive has good adhesion to the electrode after being added to the undercoat, but its ability to absorb HF is weak, thus resulting in poor effects on inhibiting corrosion of the positive electrode current collector, reducing the loss of positive electrode active material by HF, and improving the cycle performance of the battery cell. When m / n is too small, the additive has poor adhesion to the electrode after being added to the undercoat and is easy to fall off, resulting in the inability to exert a corrosion inhibition effect. By controlling the ratio of the number of polymerization units of the two types in the molecular structure of the additive, the additive can exert the maximum corrosion inhibition effect.

[0101] In some embodiments, according to the first aspect, a fifth example of the first aspect is proposed, wherein m can be an integer from 5000 to 10000; n can be an integer from 50 to 500; and m∶n=(50-500)∶1. In this design, the corrosion inhibition effect of the additive can be further improved by adjusting m, n and their ratio.

[0102] In some specific embodiments, m can be an integer from 5000 to 10000; n can be an integer from 50 to 110; m∶n=(50-200)∶1.

[0103] In some embodiments, according to the first aspect, a sixth example of the first aspect is proposed, R 1 and R 2 Each can be hydrogen or C1-C6 alkyl;

[0104] R 3 and R 4 They can be hydrogen, halogen, or C1-C6 alkyl, each independently of the other;

[0105] R 5 It can be hydrogen or C1-C6 alkyl;

[0106] R 6 It can be an unsubstituted or substituted tetrahydropyrrolidinyl, an unsubstituted or substituted pyrrolidone, an unsubstituted or substituted pyridyl, an unsubstituted or substituted hexahydropyridyl, or an unsubstituted or substituted imidazolyl, and the substituent can be halogen, hydroxyl, primary amino, secondary amino, C1-C6 alkyl, or C1-C6 alkoxy.

[0107] m can be an integer from 1000 to 10000;

[0108] n can be an integer from 10 to 1000;

[0109] m∶n=(10-1000)∶1.

[0110] In this design, by optimizing group R 1 R 2 R 3 R 4 R 5 R 6 The addition of , m, and n can further enhance the corrosion inhibition effect of the additives.

[0111] In some embodiments, according to the first aspect, a seventh example of the first aspect is proposed, R 1 and R 2 They can be hydrogen independently of each other;

[0112] R 3 and R 4 Each can be F independently;

[0113] R 5 It can be hydrogen or C1-C6 alkyl;

[0114] R 6 It can be an unsubstituted or substituted tetrahydropyrrolidinyl, an unsubstituted or substituted pyrrolidinyl or an unsubstituted or substituted pyridyl, and the substituent can be a C1-C6 alkyl;

[0115] m can be an integer from 1000 to 10000;

[0116] n can be an integer from 10 to 1000;

[0117] m∶n=(10-1000)∶1.

[0118] In this design, the optimized group R is used. 1 R 2 R 3 R 4 R 5 R 6 Substituents, m, and n can further enhance the corrosion inhibition effect of additives.

[0119] A second aspect of this application provides a method for preparing an additive of general formula I, comprising the following steps:

[0120] In the presence of an initiator, the compound of formula II undergoes a polymerization reaction with the compound of formula III to obtain the additive of general formula I:

[0121]

[0122] in,

[0123] R 1 and R 2 They are either hydrogen or C1-C independently of each other. 12 alkyl;

[0124] R 3 and R 4 They are independently hydrogen, halogen, or C1-C 12 alkyl;

[0125] R 5 It is hydrogen or C1-C 12 alkyl;

[0126] R 6 The substituent is a 4-20 member nitrogen-containing heterocyclic group that is either unsubstituted or substituted, or a 5-20 member nitrogen-containing heteroaryl group that is either unsubstituted or substituted, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, or C1-C. 12 Alkyl or C1-C 12 Alkoxy;

[0127] m is an integer between 1000 and 10000;

[0128] n is an integer from 10 to 1000.

[0129] R here 1 R 2 R 3 R 4 R 5 R 6 The definitions of substituents, m, and n are as defined above.

[0130] In the technical solution of this application embodiment, the additive of this application can be easily prepared by causing the compound of formula II to undergo a polymerization reaction with the compound of formula III.

[0131] In some embodiments, according to the second aspect, a first example of the second aspect is provided, wherein the molar ratio of compound II to compound III is (10-1000):1, for example, it may be 10:1, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1, 550:1, 600:1, 650:1, 700:1, 750:1, 800:1, 850:1, 900:1, 950:1 or 1000:1, preferably (10-100):1.

[0132] In this design, by adjusting the molar ratio of compound II to compound III, the ratio of m to n can be controlled, thereby optimizing the adhesive properties and HF absorption capacity of the additive.

[0133] In some embodiments, according to the second aspect, a second example of the second aspect is provided, wherein after the polymerization reaction is completed, the resulting crude product is precipitated in icy diethyl ether. In this design, by precipitating the crude product in icy diethyl ether, the product can be purified, thereby improving the product purity.

[0134] Preferably, the temperature of the icy ether can be from -10°C to 0°C.

[0135] In some specific embodiments, the polymerization reaction can be carried out under an inert gas atmosphere. The inert gas can be nitrogen or argon, etc. Conducting the polymerization reaction under an inert gas atmosphere can prevent the oxidation of free radicals.

[0136] In some specific embodiments, the initiator may be one or more selected from azobisisobutyronitrile, azobisisoheptanenitrile, diisopropyl peroxide dicarbonate, di-n-propyl peroxide dicarbonate, di-tert-butane peroxide, potassium persulfate, ammonium persulfate, succinyl peroxide, and di(2-ethylhexyl) peroxide. Preferably, the initiator may be azobisisobutyronitrile or azobisisoheptanenitrile.

[0137] In some specific embodiments, the polymerization reaction temperature can be 40-80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. The reaction time can be 2-24 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, or 24 hours.

[0138] In some specific embodiments, the solvent used in the polymerization reaction may be one or more of tetrahydrofuran, pyridine, N,N-dimethylformamide, and N-methylpyrrolidone. This application does not impose any particular limitation on the type of solvent, as long as it can dissolve compounds of formula II and formula III and does not participate in the polymerization reaction.

[0139] The third aspect of this application provides the use of the additive described in the first aspect of this application for mitigating corrosion of the positive current collector.

[0140] A fourth aspect of this application provides a positive electrode sheet comprising the additives described in the first aspect of this application.

[0141] In the technical solution of this application embodiment, since the additive of the first aspect of this application is used, the corrosion of the positive current collector in the positive electrode sheet of this application can be greatly alleviated, and the battery life can be effectively extended.

[0142] The fifth aspect of this application provides a method for preparing a positive electrode sheet, comprising:

[0143] The additives, conductive agents, and solvents described in the first aspect of this application are mixed, coated onto the positive electrode current collector, and dried to obtain a base coating; and

[0144] A positive electrode material layer is formed on the base coating.

[0145] In the technical solution of this application embodiment, by forming a base coating containing the additives of this application on the positive electrode current collector, and then forming a positive electrode material layer on the base coating, the HF in the battery can be effectively absorbed and fixed, reducing its corrosion of the positive electrode current collector and the loss of the positive electrode active material, and extending the battery life.

[0146] In some embodiments, according to the fifth aspect, a first example of the fifth aspect is provided, wherein the conductive agent may be well known to those skilled in the art, such as carbon nanotubes, conductive carbon black, etc.

[0147] In some embodiments, according to the fifth aspect, a second example of the fifth aspect is provided, wherein the mass ratio of the additive to the conductive agent may be 1:9 to 9:1, for example, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, preferably 1:1.5 to 1.5:1.

[0148] In some embodiments, according to the fifth aspect, a third example of the fifth aspect is proposed, wherein the solvent may be well known to those skilled in the art, such as N-methylpyrrolidone, N,N-dimethylformamide, pyridine, etc.

[0149] In some embodiments, according to the fifth aspect, a fourth example of the fifth aspect is proposed, wherein the positive current collector may be made of a material with good conductivity and mechanical strength, such as aluminum foil, but is not limited thereto.

[0150] In some embodiments, according to the fifth aspect, a fifth example of the fifth aspect is proposed, wherein an undercoating layer may be formed on both surfaces of the positive current collector.

[0151] In some embodiments, according to the fifth aspect, a sixth example of the fifth aspect is proposed, wherein in the step of preparing the primer layer, additives, binders, conductive agents, and solvents may be mixed. In particular, when R 3 R 4 When neither of the components is halogenated, the base coating preferably also includes a binder. The binder is well known to those skilled in the art and will not be described in detail here.

[0152] The method for forming the positive electrode material layer in this application is well known to those skilled in the art and will not be described in detail here.

[0153] To mitigate corrosion of the positive electrode current collector, existing technologies typically add one or more organosilicon compounds or choline ionic liquids to the electrolyte to inhibit the corrosion of the positive electrode current collector by HF. However, this method of mitigating corrosion by adding additives to the electrolyte can easily affect battery performance (such as cycle performance, rate performance, and low-temperature performance). In contrast, the additive in this application, when mixed with a conductive agent, is applied as a base coating to the surface of the positive electrode current collector, exerting a corrosion-inhibiting effect and therefore does not adversely affect battery performance.

[0154] The sixth aspect of this application provides a lithium-ion battery, including the positive electrode sheet described in the fourth aspect of this application or the positive electrode sheet obtained according to the preparation method described in the fifth aspect of this application.

[0155] In the technical solution of this application embodiment, since the additive of the first aspect of this application is used, the corrosion of the positive electrode current collector in the lithium-ion battery of this application can be greatly alleviated, and the battery life can be effectively extended.

[0156] Terminology Definitions and Explanations

[0157] The term "C1-C" 12 "alkyl" should be understood to preferably represent a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably C1-C6 alkyl. "C1-C6 alkyl" should be understood to preferably represent a straight-chain or branched saturated monovalent hydrocarbon group having 1, 2, 3, 4, 5, or 6 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-Methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl or isomers thereof. In particular, the group has 1, 2, 3 or 4 carbon atoms (“C1-C4 alkyl”), such as methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl; more particularly, the group has 1, 2 or 3 carbon atoms (“C1-C3 alkyl”), such as methyl, ethyl, n-propyl or isopropyl.

[0158] An alkoxy group refers to an alkyl group bonded through one oxygen atom. The term "C1-C" is also used. 12 "Alkoxy" should be understood to preferably mean a straight-chain or branched alkyloxy group having 1 to 12 carbon atoms, more preferably having 1 to 6 carbon atoms, and preferably a C1-C6 alkoxy group.

[0159] The term "halogen" refers to F, Cl, Br, or I.

[0160] The term "4-20 nitrogen-containing heterocyclic group" refers to a saturated monovalent monocyclic or bicyclic hydrocarbon ring having 4-20 ring atoms and containing 1-5 N atoms, preferably 1-3 N atoms.

[0161] The term "5-20 nitrogen-containing heteroaryl" should be understood to include monovalent monocyclic, bicyclic or tricyclic aromatic ring systems that have 5-20 ring atoms and contain 1-5 N atoms, preferably 1-3 N atoms, for example, 5-membered nitrogen-containing heteroaryl, 6-membered nitrogen-containing heteroaryl or 5-14-membered nitrogen-containing fused heteroaryl.

[0162] The term "substituted" means that one or more hydrogen atoms on a specified atom are replaced by one of the listed groups, provided that the substitution does not exceed the normal valence of the specified atom in the present case and the substitution forms a stable compound. Combinations of substituents and / or variables are permitted only if such combinations form a stable compound.

[0163] The present invention will be further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0164] Additive preparation

[0165] Example 1: Preparation of Formula I-1

[0166]

[0167] Weigh 1 mol of vinylidene fluoride (CAS No. 75-38-7) and 0.02 mol of 4-vinylpyridine (CAS No. 100-43-6), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and the additive of formula I-1 can be obtained, where m is 5005, n is 98, and m∶n=51.

[0168] The values ​​of m and n were determined by calculating the peak areas of characteristic hydrogen atoms within different polymer units of the additive molecule using proton nuclear magnetic resonance spectroscopy. Specific characterization information is as follows:

[0169] The molecular structure of the additive was determined on a Bruker AVANCE|||400 NMR spectrometer at a test temperature of 25°C. Tetramethylsilane (TMS) was used as an internal standard, and deuterated chloroform (CDCl3) was used as the solvent.

[0170] Test procedure: Dissolve 5 mg of the additive sample in the above solvent, transfer it to an NMR tube, and inject 1 mL. After the test, the values ​​of m and n can be determined by calculating the peak areas of characteristic hydrogen atoms in different polymer units within the additive molecule.

[0171] Example 2: Preparation of Formula I-1

[0172]

[0173] Weigh 2 mol of vinylidene fluoride (CAS No. 75-38-7) and 0.01 mol of 4-vinylpyridine (CAS No. 100-43-6), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and obtain the additive of formula I-1, where m is 9879, n is 51, and m∶n=194.

[0174] The method for determining m and n is the same as in Example 1.

[0175] Example 3: Preparation of Formula I-1

[0176]

[0177] Weigh 1 mol of vinylidene fluoride (CAS No. 75-38-7) and 0.1 mol of 4-vinylpyridine (CAS No. 100-43-6), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and the additive of formula I-1 can be obtained, where m is 5012, n is 504, and m∶n=10.

[0178] The method for determining m and n is the same as in Example 1.

[0179] Example 4: Preparation of Formula I-1

[0180]

[0181] Weigh 2 mol of vinylidene fluoride (CAS No. 75-38-7) and 0.002 mol of 4-vinylpyridine (CAS No. 100-43-6), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and the additive of formula I-1 can be obtained, where m is 9976, n is 10, and m∶n=998.

[0182] The method for determining m and n is the same as in Example 1.

[0183] Example 5: Preparation of Formula I-2

[0184]

[0185] Weigh 1 mol of vinylidene fluoride and 0.02 mol of 2-vinyl-5-methylpyridine (CAS No. 107411-10-9), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and the additive of formula I-2 can be obtained, where m is 5123, n is 102, and m∶n=50.

[0186] The method for determining m and n is the same as in Example 1.

[0187] Example 6: Preparation of Formula I-3

[0188]

[0189] Weigh 1 mol of vinylidene fluoride and 0.02 mol of 5-ethyl-2-vinylpyridine (CAS No. 5408-74-2), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and the additive of formula I-3 can be obtained, where m is 5203, n is 104, and m∶n=50.

[0190] The method for determining m and n is the same as in Example 1.

[0191] Example 7: Preparation of Formula I-4

[0192]

[0193] Weigh 1 mol of vinylidene fluoride and 0.02 mol of 2-(but-1-en-1-yl)tetrahydropyrrole (CAS No. 617713-95-8), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and the additive of formula I-4 can be obtained, where m is 5119, n is 101, and m∶n=51.

[0194] The method for determining m and n is the same as in Example 1.

[0195] Example 8: Preparation of Formula I-5

[0196]

[0197] Weigh 1 mol of vinylidene fluoride and 0.02 mol of 5-vinyl-2-pyrrolidone (CAS No. 7529-16-0), dissolve them in 200 mL of tetrahydrofuran, evacuate (to avoid oxidation of free radicals), continuously pass N2 into a three-necked flask, add 0.05 g of azobisisobutyronitrile initiator, heat to 70 °C, stir and react for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and the additive of formula I-5 can be obtained, where m is 5007, n is 99, and m∶n=51.

[0198] The method for determining m and n is the same as in Example 1.

[0199] Comparative Example 1

[0200] Commercially available polyvinylidene fluoride (PVDF) was provided as an additive to compare with the additives in Examples 1-8.

[0201] Comparative Example 2

[0202]

[0203] The procedure was carried out according to the method described in Example 1, except that 4-vinylpyridine was replaced with 4-vinylbenzene. In the prepared additive of formula I-1, m is 5002, n is 101, and m∶n=50.

[0204] The method for determining m and n is the same as in Example 1.

[0205] Comparative Example 3

[0206]

[0207] The method described in Example 1 was followed, except that vinylidene fluoride was replaced with ethylene. In the prepared additive of formula I-1, m is 4997, n is 102, and m∶n=49.

[0208] The method for determining m and n is the same as in Example 1.

[0209] Comparative Example 4

[0210] The method described in Example 1 was followed, except that the amount of vinylidene fluoride used was 1 mol and the amount of 4-vinylpyridine used was 0.2 mol. In the prepared additive of formula I-1, m was 5000, n was 997, and m∶n=5.

[0211] The method for determining m and n is the same as in Example 1.

[0212] Comparative Example 5

[0213] The method described in Example 1 was followed, except that the amount of vinylidene fluoride used was 2 mol and the amount of 4-vinylpyridine used was 0.015 mol. In the prepared additive of formula I-1, m is 10102, n is 8, and m∶n=1263.

[0214] The method for determining m and n is the same as in Example 1.

[0215] Lithium-ion batteries were prepared using the additives from Examples 1-8 and Comparative Examples 1-5 according to the following general preparation method.

[0216] Lithium-ion battery manufacturing

[0217] 1. Pretreatment of the positive electrode substrate

[0218] The additives of Examples 1-8 and Comparative Examples 1-5 were dissolved in N-methylpyrrolidone (NMP) with SP conductive carbon black at a mass ratio of 50:50. After being stirred and dispersed evenly, the mixture was coated onto an aluminum foil substrate and dried for later use.

[0219] 2. Lithium-ion battery manufacturing

[0220] 1) Preparation of positive electrode sheet: Nickel-cobalt-manganese ternary positive electrode material, SP conductive carbon black and PVDF are added and mixed evenly in a mass ratio of 96:2.5:1.5. Then, NMP solvent is added to adjust the solid content to 70%-80%. After stirring evenly, a positive electrode slurry is obtained. Then, the positive electrode slurry is coated on the positive electrode sheet that has undergone the primer pretreatment (i.e., the positive electrode sheet obtained in step 1). After drying, cold pressing and slitting, the positive electrode sheet is made.

[0221] 2) Preparation of negative electrode sheet: Graphite and SP conductive carbon black are dry mixed at a mass ratio of 97:3, deionized water is added, the solid content is adjusted to 45%-55%, and the mixture is stirred evenly to obtain negative electrode slurry. Then, the negative electrode sheet is made by coating, drying, cold pressing and slitting.

[0222] 3) The positive and negative electrode sheets obtained in steps 1 and 2 are wound together with the separator to form a battery cell, and then packaged with an aluminum-plastic film to form a dry battery cell. After processes such as liquid injection, formation, and aging, a lithium-ion battery is prepared.

[0223] Electrode Testing

[0224] 1. Electrode adhesion test

[0225] Take the positive electrode sheets from each embodiment and comparative example, and cut them into test samples 100 mm long and 10 mm wide. Take a 25 mm wide stainless steel plate, apply double-sided tape (11 mm wide), and attach the positive electrode material side of the test sample to the double-sided tape on the stainless steel plate. Roll the surface back and forth three times with a 2000 g roller at a speed of 300 mm / min. Then, bend one end of the test sample 180 degrees and manually peel the positive electrode material layer and current collector 25 mm apart along the length direction. Fix the test sample on a testing machine (e.g., INSTRON 336), ensuring that the peeling surface is aligned with the force line of the testing machine (i.e., parallel to the direction of movement of the testing machine during peeling). The testing machine continuously peels at a speed of 30 mm / min to obtain the peeling force curve. The average value of the stable segment (i.e., the segment on the peel force curve where it no longer increases monotonically) is taken as the peel force F0. Then, the adhesion force between the negative electrode membrane and the current collector in the test sample is F = F0 / width of the test sample (the unit of F is N / m). The test results are shown in Table 1 below.

[0226] 2. Confirmation of electrode corrosion after cycling

[0227] The battery cell was disassembled after 500 cycles at 60℃ to check the surface corrosion of the positive electrode. The corrosion was categorized as severe / moderate / slight / no corrosion based on the size of the corrosion area. The test results are shown in Table 1 below. The surface corrosion of the positive electrode in Example 1 is shown below. Figure 1 As shown. The surface corrosion of the positive electrode in Comparative Example 1 is as follows. Figure 2 and 3 As shown.

[0228] Battery performance test

[0229] Battery cycle performance test

[0230] At 25°C, the battery was charged at a constant current of 1 / 3C to a voltage of 4.3V, then charged at a constant voltage of 4.3V to a current of 0.05C, left to rest for 5 minutes, and then discharged at 1 / 3C to a voltage of 2.8V. The resulting capacity was recorded as the initial capacity C0. The battery was then transferred to a 60°C high-temperature chamber, and the above charge-discharge steps were repeated for the same battery. The discharge capacity Cn of the battery after the nth cycle was recorded. The battery capacity retention rate after each cycle was Ph = Cn / C0 × 100%. The discharge capacity retention rate after the 500th cycle was measured for both the example and the comparative example. The test results are shown in Table 1 below.

[0231] Table 1

[0232]

[0233] A comparison of Examples 1-8 with Comparative Example 1 shows that the aluminum foil corrosion is significantly improved and the battery cycle capacity retention is also significantly enhanced after using the additives of this application. This can also be attributed to... Figure 1-3 Visually, no aluminum foil corrosion was observed in the positive electrode of Example 1, and the interface was good (e.g., Figure 1 (as shown); while the positive electrode of Comparative Example 1 was severely corroded, with a large amount of active material detaching from the surface (as shown). Figure 2-3 (As shown).

[0234] By comparing Example 1 and Comparative Example 2, it can be seen that group R 6 Nitrogen atoms in the solution are crucial for mitigating aluminum foil corrosion.

[0235] By comparing Example 1 and Comparative Example 3, it can be seen that group R 3 and R 4 When all are H, due to the lack of good oxidation resistance of F, the base coating is prone to aging and peeling after long-term cycling, thus failing to play a good corrosion inhibition role.

[0236] By comparing Examples 1, 3, and 4 with Comparative Examples 4-5, it can be seen that when the ratio of m to n is not within the range of this application, the anti-corrosion effect is poor.

[0237] Comparing Examples 1-4, it can be seen that when the ratio of m to n is small (Example 3), the electrode adhesion is low. Although the corrosion prevention effect is also very good, the low adhesion easily leads to the shedding of active material, resulting in a slightly lower capacity retention rate. When the ratio of m to n is large (Example 4), although the electrode adhesion is high, the corrosion prevention effect is poor due to the small proportion of HF-absorbing structural units. Slight corrosion still occurs, and the capacity retention rate is also low.

[0238] Comparing Examples 5-8, it can be seen that by expanding the structural composition to a certain extent, the synthesized additives also have corresponding anti-corrosion effects, indicating that this is a class of similar structures with general functions, not limited to a single structure.

[0239] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An additive, characterized in that, It has a structure with general formula I: in, R 1 and R 2 They are either hydrogen or C1-C independently of each other. 12 alkyl; R 3 and R 4 They are independently hydrogen, halogen, or C1-C 12 alkyl; R 5 It is hydrogen or C1-C 12 alkyl; R 6 The substituent is a 4-20 member nitrogen-containing heterocyclic group that is either unsubstituted or substituted, or a 5-20 member nitrogen-containing heteroaryl group that is either unsubstituted or substituted, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, or C1-C. 12 Alkyl or C1-C 12 Alkoxy; m is an integer between 1000 and 10000; n is an integer from 10 to 1000.

2. The additive according to claim 1, characterized in that, The 4-20 member nitrogen-containing heterocyclic group is a 4-membered nitrogen-containing heterocyclic group, a 5-membered nitrogen-containing heterocyclic group, or a 6-membered nitrogen-containing heterocyclic group; The 5-20 nitrogen-containing heteroaryl group is a 5-nitrogen-containing heteroaryl group, a 6-nitrogen-containing heteroaryl group, or a 5-14 nitrogen-containing fused heteroaryl group.

3. The additive according to claim 2, characterized in that, The 4-20 nitrogen-containing heterocyclic group is azacyclopropane, tetrahydropyrrolyl, pyrrolidone, or hexahydropyridyl; The 5-20 nitrogen-containing heteroaryl groups are pyrrole, pyrazolyl, imidazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, tetrazolyl, pyridinyl, pyridazinyl, pyrimidinyl, 1,3,5-triazinyl, quinolinyl, benzimidazolyl, or benzotriazolyl.

4. The additive according to any one of claims 1-3, characterized in that, R 3 and R 4 They are halogens, independent of each other.

5. The additive according to claim 4, characterized in that, m∶n=(10-1000)∶1.

6. The additive according to claim 5, characterized in that, m is an integer between 5000 and 10000; n is an integer between 50 and 500; m∶n=(50-500)∶1.

7. The additive according to any one of claims 1-3, characterized in that, R 1 and R 2 Each is independently hydrogen or C1-C6 alkyl; R 3 and R 4 Each of them is independently hydrogen, halogen, or C1-C6 alkyl; R 5 It is hydrogen or C1-C6 alkyl; R 6 The substituent is an unsubstituted or substituted tetrahydropyrrolidinyl, an unsubstituted or substituted pyrrolidone, an unsubstituted or substituted pyridyl, an unsubstituted or substituted hexahydropyridyl, or an unsubstituted or substituted imidazolyl, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, C1-C6 alkyl, or C1-C6 alkoxy. m is an integer between 1000 and 10000; n is an integer from 10 to 1000; m∶n=(10-1000)∶1.

8. The additive according to any one of claims 1-3, characterized in that, R 1 and R 2 Each is hydrogen independently; R 3 and R 4 Each is independently represented by F; R 5 It is hydrogen or C1-C6 alkyl; R 6 The substituent is an unsubstituted or substituted tetrahydropyrrolidinyl, an unsubstituted or substituted pyrrolidinyl or an unsubstituted or substituted pyridyl, wherein the substituent is a C1-C6 alkyl group; m is an integer between 1000 and 10000; n is an integer from 10 to 1000; m∶n=(10-1000)∶1.

9. A method for preparing an additive of general formula I, characterized in that, Includes the following steps: In the presence of an initiator, the compound of formula II undergoes a polymerization reaction with the compound of formula III to obtain the additive of general formula I: in, R 1 and R 2 They are either hydrogen or C1-C independently of each other. 12 alkyl; R 3 and R 4 They are independently hydrogen, halogen, or C1-C 12 alkyl; R 5 It is hydrogen or C1-C 12 alkyl; R 6 The substituent is a 4-20 member nitrogen-containing heterocyclic group that is either unsubstituted or substituted, or a 5-20 member nitrogen-containing heteroaryl group that is either unsubstituted or substituted, wherein the substituent is a halogen, hydroxyl, primary amino, secondary amino, or C1-C. 12 Alkyl or C1-C 12 Alkoxy; m is an integer between 1000 and 10000; n is an integer from 10 to 1000.

10. The preparation method according to claim 9, characterized in that, The molar ratio of compound II to compound III is (10-1000):

1.

11. The preparation method according to claim 9 or 10, characterized in that, After the polymerization reaction is completed, the crude product is precipitated in ice-cold ether.

12. Use of the additive according to any one of claims 1-8 for mitigating corrosion of the positive current collector.

13. A positive electrode plate, characterized in that, The additives included in any one of claims 1-8.

14. A method for preparing a positive electrode sheet, characterized in that, include: The additive, conductive agent and solvent described in any one of claims 1-8 are mixed and coated onto the positive electrode current collector. After drying, a base coating is obtained. as well as A positive electrode material layer is formed on the base coating.

15. A lithium-ion battery, characterized in that, This includes the positive electrode sheet as described in claim 13 or the positive electrode sheet obtained by the preparation method according to claim 14.

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