Negative pole piece and preparation method thereof, battery and power utilization device

Abstract

The invention discloses a negative pole piece and a preparation method thereof, a battery and an electric device, the negative pole piece comprises a polymer shown in formula I: # imgabs0 # R1, R2 and R3 independently comprise at least one of H atom, halogen, aryl, carboxyl and substituted or unsubstituted alkyl with 1-5 carbon atoms, q1 comprises at least one of a group shown in a formula II, a group containing boron atoms or halogen, and n is 5-100; # imgabs1 # R4, R5 and R6 each independently comprise at least one of an H atom, a group containing a boron atom, halogen, a carboxyl group, a hydroxyl group and an alkyl group with 1-3 carbon atoms, and at least one of R4, R5 and R6 comprises at least one of a group containing a boron atom, a nitro group, halogen, a carboxyl group, a hydroxyl group and an alkyl group with 1-3 carbon atoms. The negative pole piece can improve the cycle performance of the battery.

Description

Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to a negative electrode plate and a preparation method thereof, a battery and an electrical device. Background Art

[0002] In recent years, as the application scope of batteries has become more and more extensive, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. However, the SEI film (solid electrolyte interface) on the surface of the negative electrode of existing batteries has low toughness, which will cause the SEI film to continuously rupture and reorganize during the cycle process, increase the consumption of active metal ions, and reduce the cycle life of the battery. Summary of the invention

[0003] In view of the technical problems existing in the background technology, the present application provides a negative electrode plate, aiming to improve the cycle performance of a battery containing the negative electrode plate.

[0004] In order to achieve the above-mentioned object, one aspect of the present application provides a negative electrode plate, wherein the negative electrode plate comprises a polymer represented by formula I:

[0005]

[0006] wherein R1, R2 and R3 each independently include at least one of H atoms, halogen, aryl, carboxyl, substituted or unsubstituted hydrocarbon groups of 1 to 5 carbon atoms, Q1 includes at least one of the groups shown in formula II, groups containing boron atoms or halogen, and n is 5 to 100;

[0007]

[0008] In formula II, R4, R5 and R6 each independently include at least one of an H atom, a group containing a boron atom, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms, and at least one of R4, R5 and R6 includes at least one of a group containing a boron atom, a nitro group, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms.

[0009] The present application includes at least the following beneficial effects: the negative electrode plate of the present application includes the above-mentioned polymer, which can form a SEI film with higher toughness, reduce the consumption of active metal ions in the battery cycle process, and thus improve the cycle performance of the battery.

[0010] In some embodiments of the present application, the weight average molecular weight of the polymer represented by Formula I is 300-50000, and can be 300-5000. Thus, the cycle performance of the battery can be improved.

[0011] In some embodiments of the present application, the molecular weight of the polymer represented by Formula I is ≤1000, and can be selected as . . . , thereby improving the cycle performance of the battery.

[0012] In some embodiments of the present application, the group containing a boron atom includes at least one of -B(OH)2, -BF3, -BCl3, -BBr3 or -B(C6F5)3. Thus, the cycle performance of the battery can be improved.

[0013] In some embodiments of the present application, the halogen includes at least one of -F, -Cl, -Br or -I. Thus, the cycle performance of the battery can be improved.

[0014] In some embodiments of the present application, the substituent when the hydrocarbon group of 1 to 5 carbon atoms is substituted includes at least one of a carboxyl group, a hydroxyl group or an aryl group, thereby improving the cycle performance of the battery.

[0015] In some embodiments of the present application, the polymer represented by Formula I includes at least one of the substances represented by the following structural formulas:

[0016]

[0017]

[0018] n is 5-100.

[0019] Thereby, the cycle performance of the battery can be improved.

[0020] In some embodiments of the present application, the negative electrode plate further comprises a negative electrode active material, and the polymer represented by Formula I is coated on at least a portion of the surface of the negative electrode active material, thereby improving the cycle performance of the battery.

[0021] In some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the current collector, and the negative electrode active material layer includes a polymer represented by Formula I. Thus, the cycle performance of the battery can be improved.

[0022] In some embodiments of the present application, based on the total mass of the negative electrode active material layer, the mass proportion of the polymer represented by Formula I is 0.01%-4.5%, and optionally 0.5%-2%. Thus, the cycle performance of the battery can be improved.

[0023] In some embodiments of the present application, the negative electrode sheet includes: a negative electrode current collector, a negative electrode active material layer and a protective layer, wherein the negative electrode active material layer is formed on at least one side of the negative electrode current collector; the protective layer is formed on a side of the negative electrode active material layer away from the negative electrode current collector, and the protective layer includes a polymer represented by Formula I. Thus, the cycle performance of the battery can be improved.

[0024] In some embodiments of the present application, based on the total mass of the protective layer, the mass proportion of the polymer represented by Formula I is 0.01%-4.5%, and optionally 0.5%-2%. Thus, the cycle performance of the battery can be improved.

[0025] A second aspect of the present application provides a method for preparing a negative electrode sheet, comprising: forming a negative electrode sheet comprising a polymer represented by Formula I;

[0026]

[0027] wherein R1, R2 and R3 each independently include at least one of H atoms, halogen, aryl, carboxyl, substituted or unsubstituted hydrocarbon groups of 1 to 5 carbon atoms, Q1 includes at least one of the groups shown in formula II, groups containing boron atoms or halogen, and n is 5 to 100;

[0028]

[0029] In formula II, R4, R5 and R6 each independently include at least one of an H atom, a group containing a boron atom, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms, and at least one of R4, R5 and R6 includes at least one of a group containing a boron atom, a nitro group, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms.

[0030] Therefore, the negative electrode sheet prepared by the method of the present application can form a SEI film with high toughness on the negative electrode sheet, reducing the consumption of active metal ions during the battery cycle process, thereby improving the cycle performance of the battery.

[0031] In some embodiments of the present application, the method includes: forming a negative electrode active material layer including a monomer of a polymer represented by Formula I and a negative electrode active material on at least one side of a negative electrode current collector; polymerizing the monomer of the polymer represented by Formula I to obtain a negative electrode sheet. Thus, the cycle performance of the battery can be improved.

[0032] In some embodiments of the present application, the method includes: forming a negative electrode active material layer on at least one side of the negative electrode current collector; forming a protective layer on the negative electrode active material layer on a side away from the negative electrode current collector, wherein the protective layer includes a monomer of a polymer represented by Formula I; and polymerizing the monomer of the polymer represented by Formula I to obtain a negative electrode sheet. Thus, the cycle performance of the battery can be improved.

[0033] In some embodiments of the present application, the monomers of the polymer represented by Formula I are polymerized under the action of an electric field, and the voltage of the electric field is 1.6V-2.5V, and can be 1.6V-2.2V. In this way, the cycle performance of the battery can be improved.

[0034] In some embodiments of the present application, the electropolymerization potential of the monomer of the polymer represented by Formula I is 1.6V-2.5V, and can be 1.6V-2.2V. Thus, the cycle performance of the battery can be improved.

[0035] In some embodiments of the present application, the monomer of the polymer represented by Formula I includes at least one of the substances represented by the following structural formulas:

[0036]

[0037]

[0038] Thereby, the cycle performance of the battery can be improved.

[0039] In some embodiments of the present application, the method comprises: coating the monomer of the polymer represented by formula I on the surface of the negative electrode active material to prepare a negative electrode sheet, thereby improving the cycle performance of the battery.

[0040] In some embodiments of the present application, at 25° C., the solubility of the monomer of the polymer represented by Formula I in 100 g of water is ≥ 0.01 g, and optionally, at 25° C., the solubility of the monomer of the polymer represented by Formula I in 100 g of water is ≥ 1 g. Thus, the cycle performance of the battery can be improved.

[0041] The third aspect of the present application provides a battery, the battery comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet obtained by the method described in the second aspect of the present application. Therefore, the battery of the present application has excellent cycle performance.

[0042] The fourth aspect of the present application provides an electric device, characterized in that the electric device comprises the battery described in the third aspect of the present application. Therefore, the electric device of the present application has excellent cycle performance.

[0043] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0045] Figure 1 It is a schematic diagram of a negative electrode sheet according to one embodiment of the present application.

[0046] Figure 2 It is a schematic diagram of a negative electrode sheet according to another embodiment of the present application.

[0047] Figure 3 is a schematic diagram of a battery according to one embodiment of the present application.

[0048] Figure 4 yes Figure 3 An exploded view of a battery according to an embodiment of the present application is shown.

[0049] Figure 5 is a schematic diagram of a battery module according to an embodiment of the present application.

[0050] Figure 6 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0051] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0052] Figure 8 Schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0053] Description of reference numerals:

[0054] 1 battery; 11 shell; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper box; 32 lower box; 20 negative electrode plate; 21 negative electrode current collector; 22 negative electrode active material layer; 23 protective layer. DETAILED DESCRIPTION

[0055] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0056] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0057] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0058] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0059] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0060] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0061] At present, from the perspective of market development, the application of secondary batteries is becoming more and more extensive. Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of secondary batteries, the market demand is also constantly expanding.

[0062] As the battery is charged for the first time, the additives and solvents in the electrolyte reach their respective decomposition potentials, and decompose in sequence on the surface of the negative active material of the negative electrode plate to generate corresponding inorganic carbonates and organic matter, thereby forming an SEI film on the surface of the negative electrode plate. During the battery charge and discharge process, the SEI film exists as a component that isolates the electrolyte from the negative electrode plate and conducts active metal ions, allowing the battery to perform charge and discharge cycles. However, due to the continuous expansion or contraction of the negative active material in the negative electrode plate, and the low toughness of the SEI film formed by these inorganic carbonates and organic matter, the SEI film will rupture during the cycle. As the cycle process continues, a new SEI film will continue to form on the surface of the negative electrode plate, that is, the SEI film will continue to rupture and reorganize during the cycle, increasing the consumption of active metal ions and reducing the cycle life of the battery.

[0063] The present application adds a polymer represented by formula I to the negative electrode plate. The polymer represented by formula I can combine with the negative electrode active material in the negative electrode plate to form a SEI film on the surface of the negative electrode active material. The SEI film has good affinity and binding properties with the negative electrode active material and has good toughness. It can slow down the damage to the SEI film caused by the expansion or contraction of the negative electrode active material during the battery cycle, reduce the continuous rupture and reorganization of the SEI film caused by the continuous expansion or contraction of the negative electrode active material in the negative electrode plate, reduce the consumption of active metal ions, and improve the cycle life of the battery. In addition, the group Q1 in the polymer can combine with and fix the anions in the electrolyte to achieve a high migration rate of active metal ions (such as lithium ions, sodium ions, etc.) and reduce the impedance of the battery.

[0064] The negative electrode plate disclosed in the embodiment of the present application is suitable for lithium-ion batteries and sodium-ion batteries, and the battery disclosed in the embodiment of the present application can be used in electrical equipment using the battery as a power source or various energy storage systems using the battery as an energy storage element. Electrical equipment may include but is not limited to mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0065] In a first aspect, the present application provides a negative electrode plate, wherein the negative electrode plate comprises a polymer represented by formula I:

[0066]

[0067] wherein R1, R2 and R3 each independently include at least one of H atoms, halogen, aryl, carboxyl, substituted or unsubstituted hydrocarbon groups of 1 to 5 carbon atoms, Q1 includes at least one of the groups shown in formula II, groups containing boron atoms or halogen, and n is 5 to 100;

[0068]

[0069] In formula II, R4, R5 and R6 each independently include at least one of an H atom, a group containing a boron atom, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms, and at least one of R4, R5 and R6 includes at least one of a group containing a boron atom, a nitro group, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms.

[0070] The present application includes at least the following beneficial effects: in the negative electrode sheet of the present application, on the one hand, the polymer shown in formula I can combine with the negative electrode active material in the negative electrode sheet to form a SEI film on the surface of the negative electrode active material, and the SEI film has good affinity and binding with the negative electrode active material, and has good toughness, which can slow down the damage of the SEI film caused by the expansion or contraction of the negative electrode active material during the battery cycle, reduce the continuous rupture and reorganization of the SEI film caused by the continuous expansion or contraction of the negative electrode active material in the negative electrode sheet, reduce the consumption of active metal ions, and improve the cycle life of the battery; on the other hand, the group Q1 in the polymer shown in formula I can combine and fix with the anion of the electron-rich group in the electrolyte, so that the corresponding active metal ions (such as lithium ions, sodium ions, etc.) can be quickly dissociated, and have an excellent ion migration rate, which can effectively alleviate the problem of low conductivity of active metal ions, thereby reducing the ion transfer impedance, reducing the impedance of the battery, reducing the polarization of the battery, reducing the loss of active metal ions, and extending the cycle life of the battery.

[0071] In the embodiments of the present application, aryl refers to any functional group or substituent derived from a simple aromatic ring, that is, a group containing a benzene ring, which may also contain other substituents.

[0072] It is understood that in the group shown in formula II, It represents the position connected to the polymer shown in formula I. When formula I includes the group shown in formula II, there are other substituents at the ortho, meta or para position on the benzene ring, which can improve the toughness of the polymer, increase the migration rate of active metal ions, and thus extend the cycle life of the battery.

[0073] It is understood that when one or more of R1, R2 and R3 is a substituted or unsubstituted hydrocarbon group, the number of carbon atoms on the main chain is 1-5, for example, the number of carbon atoms on the main chain can be 1-4, 1-3, 2-3, etc., and when there is a substituent, the substituent can also have multiple carbon atoms. Similarly, when one or more of R4, R5 and R6 is a substituted or unsubstituted hydrocarbon group, the number of carbon atoms on the main chain is 1-3, for example, the number of carbon atoms on the main chain can be 1-2, 2-3, etc., and when there is a substituent, the substituent can also have multiple carbon atoms.

[0074] In some embodiments of the present application, the weight average molecular weight of the polymer shown in Formula I is 300-50000, for example, the weight average molecular weight of the polymer shown in Formula I can be 300-50000, 500-49000, 800-45000, 1000-40000, 5000-35000, 10000-30000, 15000-25000, etc. Thus, by controlling the weight average molecular weight of the polymer shown in Formula I within the above range, the ion conductivity of the weight average molecular weight of the polymer shown in Formula I can be improved, the impedance of the battery can be reduced, and the cycle performance of the battery can be improved. In other embodiments of the present application, the weight average molecular weight of the polymer shown in Formula I is 300-5000.

[0075] It is understood that the “weight average molecular weight of the polymer represented by Formula I” has a well-known meaning in the art and can be determined by methods commonly used in the art, for example, by the following method:

[0076] After separating the coating layer in the negative electrode active material, the molecular weight distribution curve of the polymer can be obtained by gel permeation chromatography and gel permeation chromatography. The absolute molecular weight of the polymers of different components can be obtained by mass spectrometry analysis. The molecular weight distribution curve is calibrated with a polymer of known molecular weight to obtain the relative molecular weight of each component.

[0077] In some embodiments of the present application, the group containing a boron atom includes at least one of -B(OH)2, -BF3, -BCl3, -BBr3 or -B(C6F5)3. Thus, the group containing a boron atom is an electron-deficient group, which can combine and fix with anions in the electrolyte, release a large amount of cations, so that active metal ions (such as lithium ions, sodium ions, etc.) have a high migration rate, reduce the internal resistance of the battery containing it, and improve the cycle life of the battery.

[0078] In some embodiments of the present application, the halogen includes at least one of -F, -Cl, -Br or -I. Therefore, the halogen is an electron-deficient group that can combine and fix with anions in the electrolyte, thereby releasing a large amount of cations, which can make the active metal ions have a high migration rate, reduce the internal resistance of the battery containing it, and improve the cycle life of the battery.

[0079] It can be understood that in the embodiments of the present application, one or more of R1, R2 and R3 can be halogen, and one or more of R4, R5 and R6 can also be halogen. The selection of R1, R2 and R3, R4, R5 and R6 are independent of each other and do not interfere with each other. For example, R1 can include -Cl, R5 can include -Cl, and can also include -F.

[0080] In some embodiments of the present application, the substituents when the hydrocarbon group of 1 to 5 carbon atoms is substituted include at least one of a carboxyl group, a hydroxyl group or an aryl group. Thus, the above substituents can further improve the toughness of the coating layer and improve the cycle performance of the battery.

[0081] In some embodiments of the present application, the polymer represented by Formula I includes at least one of the substances represented by the following structural formulas:

[0082]

[0083]

[0084] n is 5-100.

[0085] It can be understood that in the polymers shown in the above structural formula, the values ​​of n are independent of each other, and n can be the same or different.

[0086] Therefore, when the above substances are used in the negative electrode plate, the polymer shown in Formula I can combine with the negative electrode active material in the negative electrode plate to form a SEI film on the surface of the negative electrode active material. The SEI film has good affinity and binding properties with the negative electrode active material and has good toughness. It can slow down the damage to the SEI film caused by the expansion or contraction of the negative electrode active material during the battery cycle, reduce the continuous rupture and reorganization of the SEI film caused by the continuous expansion or contraction of the negative electrode active material in the negative electrode plate, reduce the consumption of active metal ions, and improve the cycle life of the battery. In addition, the group Q1 can combine and fix with the anions in the electrolyte, release a large amount of cations, promote the high migration rate of the active metal ions, and make the battery have a low internal resistance.

[0087] It is to be understood that the above polymers are well-known substances in the art, and can be prepared by methods well-known in the art, or can be purchased.

[0088] In some embodiments of the present application, the negative electrode plate further includes a negative electrode active material, and the polymer shown in Formula I is coated on at least part of the surface of the negative electrode active material. As a result, it is beneficial for the polymer shown in Formula I to be specifically combined with the negative electrode active material in the negative electrode active material layer, and to form a layer of SEI film on the surface of the negative electrode active material. The SEI film has good affinity and binding properties with the negative electrode active material, and has good toughness, which can slow down the damage to the SEI film caused by the expansion or contraction of the negative electrode active material during the battery cycle, reduce the continuous rupture and reorganization of the SEI film caused by the continuous expansion or contraction of the negative electrode active material in the negative electrode plate, reduce the consumption of active metal ions, and improve the cycle life of the battery.

[0089] In some embodiments of this application, please refer to Figure 1 The negative electrode plate 20 includes a negative electrode current collector 21 and a negative electrode active material layer 22 disposed on at least one side of the current collector 21, and the negative electrode active material layer 22 includes a polymer shown in Formula I. Therefore, when the negative electrode plate 20 is used in a battery, the group Q1 in the polymer shown in Formula I can combine and fix with anions in the electrolyte, release a large amount of cations, so that the active metal ions have a high migration rate, and the battery has a low internal resistance. In addition, the polymer shown in Formula I can combine with the negative electrode active material in the negative electrode active material layer 22 to form a layer of SEI film on the surface of the negative electrode active material. The SEI film has good affinity and binding properties with the negative electrode active material, and has good toughness, which can slow down the damage of the SEI film caused by the expansion or contraction of the negative electrode active material during the battery cycle, reduce the continuous rupture and reorganization of the SEI film caused by the continuous expansion or contraction of the negative electrode active material in the negative electrode plate 20, reduce the consumption of active metal ions, and improve the cycle life of the battery.

[0090] As an example, the negative electrode current collector 21 has two surfaces facing each other in its own thickness direction, and the negative electrode active material layer 22 is provided on any one or both of the two facing surfaces of the negative electrode current collector 21 .

[0091] In some embodiments of the present application, based on the total mass of the negative electrode active material layer, the mass proportion of the polymer shown in Formula I is 0.01%-4.5%. For example, based on the total mass of the negative electrode active material layer, the mass proportion of the polymer shown in Formula I can be 0.01%-4.4%, 0.05%-4.2%, 0.1%-4%, 0.5%-3.5%, 0.8%-3.3%, 1%-3%, 1.5%-2.8%, 2%-2.5%, 2.3%-2.5%, etc. Therefore, the mass proportion of the polymer shown in Formula I is within the above range, which can promote the polymer shown in Formula I to form a high-toughness SEI film on the surface of the negative electrode sheet 20, thereby improving the cycle performance of the battery. In other embodiments of the present application, based on the total mass of the negative electrode active material layer, the mass proportion of the polymer shown in Formula I is 0.5%-2%.

[0092] In some embodiments of the present application, the negative electrode current collector 21 may be a metal foil or a composite negative electrode current collector. For example, as a metal foil, a copper foil may be used. The composite negative electrode current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite negative electrode current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0093] In some embodiments of the present application, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, or tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0094] In some embodiments of the present application, the negative electrode active material layer 22 may further optionally include a binder, which may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0095] In some embodiments of the present application, based on the total mass of the negative electrode active material layer 22, the content of the binder may be 1%-5%, for example, 1.5%-4.5%, 2%-4%, 2.5%-3.5%, 2.5%-3%, etc. Therefore, the negative electrode active material layer 22 of the present application includes the above-mentioned content of the binder, which can improve the stability of the negative electrode sheet 20, thereby improving the cycle performance of the battery.

[0096] In some embodiments of the present application, the negative electrode active material layer 22 may further optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene or carbon nanofibers.

[0097] In some embodiments of the present application, based on the total mass of the negative electrode active material layer 22, the content of the conductive agent may be 0.5%-5%, such as 0.5%-4.5%, 1%-4%, 1.5%-3.5%, 2%-3%, 2.5%-3%, etc. Therefore, the negative electrode active material layer 22 of the present application includes the conductive agent in the above content, which can improve the conductivity of the negative electrode sheet 20, thereby improving the cycle performance of the battery.

[0098] In some embodiments of the present application, the negative electrode active material layer 22 may further optionally include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)).

[0099] In other embodiments of this application, please refer to Figure 2The negative electrode sheet 20 may include a negative electrode collector 21, a negative electrode active material layer 22 and a protective layer 23, wherein the negative electrode active material layer 22 is formed on at least one side of the negative electrode collector 21, and the protective layer 23 is formed on a side of the negative electrode active material layer 22 away from the negative electrode collector 21, and the protective layer 23 includes a polymer shown in Formula I. Thus, when the negative electrode sheet 20 is used in a battery, the protective layer can be in direct contact with the electrolyte, and the group Q1 of the polymer shown in Formula I can be combined with and fixed to the anions in the electrolyte, releasing a large amount of cations, so that the active metal ions have a high migration rate, and the battery has a low internal resistance. In addition, the polymer shown in Formula I can be combined with the negative electrode active material in the negative electrode active material layer 22 to form a layer of SEI film on the surface of the negative electrode active material. The SEI film has good affinity and binding properties with the negative electrode active material, and has good toughness, which can slow down the damage of the SEI film caused by the expansion or contraction of the negative electrode active material during the battery cycle, reduce the continuous rupture and reorganization of the SEI film caused by the continuous expansion or contraction of the negative electrode active material in the negative electrode sheet 20, reduce the consumption of active metal ions, and improve the cycle life of the battery. In addition, by adding the polymer shown in Formula I to the protective layer 23, the etching of the polymer shown in Formula I on the negative electrode current collector 21 can be reduced, and the influence on the bonding performance of the negative electrode active material layer can be reduced, thereby reducing the deterioration of the processing performance of the negative electrode sheet 20.

[0100] In some embodiments of the present application, based on the total mass of the protective layer, the mass proportion of the polymer shown in Formula I is 0.01%-4.5%. For example, based on the total mass of the protective layer, the mass proportion of the polymer shown in Formula I can be 0.01%-4.4%, 0.05%-4.2%, 0.1%-4%, 0.5%-3.5%, 0.8%-3.3%, 1%-3%, 1.5%-2.8%, 2%-2.5%, 2.3%-2.5%, etc. Therefore, based on the total mass of the protective layer, the mass proportion of the polymer shown in Formula I is within the above range, which can promote the polymer shown in Formula I to form a high-toughness SEI film on the surface of the negative electrode plate 20, thereby improving the cycle performance of the battery. In other embodiments of the present application, based on the total mass of the protective layer, the mass proportion of the polymer shown in Formula I is 0.5%-2%.

[0101] In some embodiments of the present application, the protective layer 23 further includes a negative electrode active material, and based on the total mass of the protective layer 12, the content of the negative electrode active material is 90%-96%, such as 91%-95%, 92%-94%, 93%-94%, etc. Therefore, the protective layer 23 of the present application includes the negative electrode active material in the above content, which can improve the capacity and cycle life of the battery.

[0102] In some embodiments of the present application, the protective layer 23 may further include a binder, and based on the total mass of the protective layer 23, the content of the binder may be 1%-5%, for example, 1.5%-4.5%, 2%-4%, 2.5%-3.5%, 2.5%-3%, etc. Therefore, the protective layer 23 of the present application includes the above-mentioned content of the binder, which can improve the stability of the negative electrode sheet 20, thereby improving the cycle performance of the battery.

[0103] In some embodiments of the present application, the protective layer 23 may further include a conductive agent, and based on the total mass of the protective layer 23, the content of the conductive agent may be 0.5%-5%, such as 0.5%-4.5%, 1%-4%, 1.5%-3.5%, 2%-3%, 2.5%-3%, etc. Therefore, the protective layer 23 of the present application includes the conductive agent in the above content, which can improve the conductivity of the negative electrode sheet 20, thereby improving the cycle performance of the battery.

[0104] It should be noted that the specific types of the negative electrode active material, the conductive agent and the binder in the protective layer 23 of the present application are the same as those in the negative electrode active material layer 22 described above, and will not be described in detail here.

[0105] The second aspect of the present application provides a method for preparing the negative electrode sheet of the first aspect, the method comprising: forming a negative electrode sheet comprising a polymer represented by formula I;

[0106]

[0107] wherein R1, R2 and R3 each independently include at least one of H atoms, halogen, aryl, carboxyl, substituted or unsubstituted hydrocarbon groups of 1 to 5 carbon atoms, Q1 includes at least one of the groups shown in formula II, groups containing boron atoms or halogen, and n is 5 to 100;

[0108]

[0109] In formula II, R4, R5 and R6 each independently include at least one of an H atom, a group containing a boron atom, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms, and at least one of R4, R5 and R6 includes at least one of a group containing a boron atom, a nitro group, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms.

[0110] Therefore, in the negative electrode sheet prepared in the embodiment of the present application, the polymer shown in Formula I can combine with the negative electrode active material in the negative electrode sheet to form a SEI film on the surface of the negative electrode active material. The SEI film has good affinity and binding with the negative electrode active material, and has good toughness, which can slow down the damage to the SEI film caused by the expansion or contraction of the negative electrode active material during the battery cycle, reduce the continuous rupture and reorganization of the SEI film caused by the continuous expansion or contraction of the negative electrode active material in the negative electrode sheet, reduce the consumption of active metal ions, and improve the cycle life of the battery. In addition, the group Q1 in the polymer shown in Formula I can combine and fix with the anions in the electrolyte, releasing a large amount of cations, so that the active metal ions (such as lithium ions, sodium ions, etc.) have a high migration rate, thereby reducing the impedance of the battery containing it.

[0111] In some embodiments of the present application, the above method includes:

[0112] S100. forming a negative electrode active material layer including a monomer of a polymer represented by Formula I and a negative electrode active material on at least one side of the negative electrode current collector;

[0113] S200. Polymerize the monomers of the polymer represented by formula I to obtain a negative electrode plate.

[0114] As an example, the negative electrode active material layer, the conductive agent, the binder and the monomer of the polymer shown in Formula I are first mixed and stirred with a solvent to obtain a negative electrode slurry, and then the negative electrode slurry is coated on at least one side of the negative electrode current collector, and then the solvent is removed by drying to obtain a negative electrode active material layer including the monomer of the polymer shown in Formula I, and then the monomer of the polymer shown in Formula I is polymerized to obtain a negative electrode sheet.

[0115] In some other embodiments of the present application, the above method includes:

[0116] S101. Forming a negative electrode active material layer on at least one side of the negative electrode current collector;

[0117] S102. forming a protective layer on the negative electrode active material layer on a side away from the negative electrode current collector, wherein the protective layer comprises a monomer of the polymer represented by formula I;

[0118] S103. Polymerize the monomers of the polymer represented by formula I to obtain a negative electrode plate.

[0119] As an example, the negative electrode active material layer, the conductive agent, the adhesive and the solvent are first mixed and stirred to obtain a negative electrode slurry, and then the negative electrode slurry is coated on at least one side of the negative electrode current collector, and the solvent is removed by drying. Then, the monomer of the polymer shown in Formula I is mixed and stirred with the negative electrode active material, the conductive agent and the adhesive and the solvent to obtain a protective layer slurry, and the protective layer slurry is coated on the side of the negative electrode active material layer away from the negative electrode current collector. The solvent is removed by drying to obtain a protective layer including the monomer of the polymer shown in Formula I, and then the monomer of the polymer shown in Formula I is polymerized to obtain a negative electrode sheet.

[0120] In some embodiments of the present application, the monomers of the polymer shown in Formula I are polymerized under the action of an electric field, and the voltage of the electric field is 1.6V-2.5V. Specifically, the voltage of the electric field can be 1.6V-2.4V, 1.7V-2.3V, 1.8V-2.2V, 1.9V-2.1V, 1.9V-2V, etc. In this way, the monomers of the polymer shown in Formula I can be polymerized during the charge and discharge cycle of the battery. Since within the electric field voltage range, the unsaturated double bonds in the monomers of the polymer shown in Formula I can be prioritized over the redox reaction of the electrolyte salt and the solvent, and through electrochemical in-situ polymerization under the action of the electric field, a high-toughness artificial SEI polymer layer is constructed on the surface of the negative electrode active material, reducing the occurrence of surface side reactions, improving the cycle performance of the battery containing it, and saving the preparation process of the negative electrode plate and the battery. In other embodiments of the present application, the voltage of the electric field is 1.6V-2.2V.

[0121] In some embodiments of the present application, the electropolymerization potential of the monomer of the polymer shown in Formula I is 1.6V-2.5V. Specifically, the electropolymerization potential of the monomer of the polymer shown in Formula I can be 1.6V-2.4V, 1.7V-2.3V, 1.8V-2.2V, 1.9V-2.1V, 1.9V-2V, etc. In this way, the current collector containing the negative electrode active material layer in step S100 can be assembled into a battery. In the charge and discharge cycle of the battery, since the electropolymerization potential of the monomer of the polymer shown in Formula I is 1.6V-2.5V, which is lower than the redox potential of the solvent and the electrolyte salt in the electrolyte, in the process of charging the battery, the unsaturated double bonds of the monomer of the polymer shown in Formula I can be prioritized over the redox reaction of the electrolyte salt and the solvent, and through electrochemical in-situ polymerization under the action of the electric field, a high-toughness artificial SEI polymer layer is constructed on the surface of the negative electrode active material, reducing the occurrence of surface side reactions, improving the cycle performance of the battery containing it, and saving the preparation process of the negative electrode plate and the battery. In other embodiments of the present application, the electropolymerization potential of the monomer of the polymer represented by Formula I is 1.6V-2.2V.

[0122] It is understood that "electropolymerization potential" has a well-known meaning in the art and can be measured by methods commonly used in the art, for example, by the following method:

[0123] Characterization by button cell:

[0124] Preparation of negative electrode sheet:

[0125] The negative electrode active material graphite, the monomer of the polymer shown in Formula I, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a proper amount of deionized water solvent system at a weight ratio of 95.5:1:0.7:1.8:1 to obtain a negative electrode slurry, and the negative electrode slurry is coated on the surface of one side of the copper foil and then dried and cold pressed to form a negative electrode active material layer on the surface of one side of the negative electrode current collector, and finally punched to obtain a negative electrode sheet;

[0126] Preparation of positive electrode:

[0127] The positive electrode active material (LiFePO4), conductive carbon (SP), and binder (polyvinylidene fluoride PVDF) are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2, and the mixture is fully stirred and mixed to prepare a positive electrode slurry. The positive electrode slurry is coated on one side of an aluminum foil, and then dried and cold pressed to form a positive electrode active material layer on the one side of the aluminum foil. Finally, the positive electrode sheet is obtained by punching.

[0128] Preparation of isolation membrane:

[0129] A polyethylene porous polymer film was used as the isolation membrane (thickness 7 μm);

[0130] Preparation of electrolyte

[0131] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) are mixed in a mass ratio of 1:1:1 to obtain a solvent, and fully dried electrolyte salt LiPF6 is dissolved in the above solvent. After mixing evenly, an electrolyte solution with a concentration of 1 mol / L is obtained.

[0132] Assembly: stack a single positive electrode sheet, a single separator, and a single negative electrode sheet in order (the side of the positive electrode sheet where the positive electrode active material layer is formed contacts the separator, and the side of the negative electrode sheet where the negative electrode active material layer is formed contacts the separator), place the separator between the positive and negative electrodes to play a role of isolation, add electrolyte, and obtain a CR2032 button-type full battery (capacity ≤5mAh) through pressure packaging (50MPa).

[0133] The button-type full battery as an experimental example was charged and discharged at a rate of 0.1C at 25°C, and the capacity (Q)-voltage (V) curve of the first cycle was recorded. The dQ / dV-V curve was obtained by differentiating it. At the same time, the button-type full battery of the control group (the monomer of the polymer shown in Formula I was not added to the negative electrode plate, wherein the negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) were in a weight ratio of 96.5:0.7:1.8:1, and the rest were the same as the above button-type full battery) was used to obtain the dQ / dV-V curve under the same conditions. By comparing the two curves, an additional peak can be seen from the dQ / dV-V curve of the button-type full battery of the experimental example. The peak is the characteristic peak of the small molecule additive, and the ordinate corresponding to the peak is the electropolymerization potential of the monomer of the polymer shown in Formula I.

[0134] In some embodiments of the present application, the monomer of the polymer represented by Formula I includes at least one of the substances represented by the following structural formulas:

[0135]

[0136] Therefore, during the charging process of the battery, the unsaturated double bonds of the above-mentioned monomers can take precedence over the redox reactions of the electrolyte salt and the solvent, and through electrochemical in-situ polymerization under the action of the electric field, a highly tough artificial SEI polymer layer is constructed on the surface of the negative electrode active material, thereby reducing the occurrence of surface side reactions, improving the cycle performance of the battery containing it, and saving the preparation process of the negative electrode sheet and the battery.

[0137] In addition, the above-mentioned monomers are abundant in source and low in cost; they are soluble in water and can be directly introduced into the existing aqueous anode slurry without the need for additional treatment or equipment, and are therefore industrially feasible.

[0138] In some embodiments of the present application, the preparation method comprises:

[0139] The monomer of the polymer shown in formula I is coated on the surface of the negative electrode active material to prepare a negative electrode plate.

[0140] Specifically, whether the monomer of the polymer represented by Formula I is polymerized and exists in the negative electrode active material layer or exists in the protective layer, the monomer of the polymer represented by Formula I can be polymerized and coated on the surface of the negative electrode active material before preparing the negative electrode plate. As an example, the monomer of the polymer represented by Formula I can be added to water to form a slurry, and then the negative electrode active material is immersed in the slurry, concentrated and dried, so as to obtain a negative electrode active material at least partially coated with the monomer of the polymer represented by Formula I.

[0141] It can be understood that after the above preparation method obtains the negative electrode active material with at least a portion of the surface coated with the monomer of the polymer represented by formula I, the method for preparing the negative electrode plate is similar to the above and will not be repeated here.

[0142] In some embodiments of the present application, at 25°C, the solubility of the monomer of the polymer shown in Formula I in 100g of water is ≥0.01g. For example, at 25°C, the solubility of the monomer of the polymer shown in Formula I in 100g of water can be 0.01g-150g, 0.1g-140g, 1g-130g, 10g-120g, 20g-100g, 30g-90g, 40g-80g, 50g-70g, 40g-60g, 50g-55g, etc. Within the above solubility range, the monomer of the polymer shown in Formula I is soluble in water and can be directly introduced into the existing aqueous anode slurry without pre-coating, additional treatment or modification of equipment in advance, and has industrial feasibility to form an SEI film containing the polymer shown in Formula I, reduce the internal resistance of the battery containing it, and improve the cycle life of the battery. In other embodiments of the present application, at 25°C, the solubility of the monomer of the polymer shown in Formula I in 100g of water is ≥1g.

[0143] It is understood that "the solubility of the monomer of the polymer represented by Formula I in 100 g of water at 25° C." is a definition known in the art and can be determined by methods known in the art, for example, by the following method:

[0144] Take several portions of the monomer of the polymer represented by formula I, prepare a series of solutions from unsaturated solution to saturated solution, stir and shake at 25°C until equilibrium, filter through a filter membrane, take the filtrate for analysis, determine the actual concentration Y of the small molecule in the solution, and plot the concentration X of the prepared solution. The turning point in the curve is the equilibrium solubility of the additive at 25°C.

[0145] In some embodiments of the present application, the negative electrode active material includes at least one of artificial graphite and natural graphite. When the monomer of the polymer shown in Formula I contains a benzene ring, it can strengthen the bond with graphite in the form of a Π=Π bond, thereby further enhancing the bonding force between the artificial SEI layer and the graphite, and can slow down the rupture / reorganization of the electrolyte-derived SEI caused by the volume expansion or contraction of the graphite during the cycle, reduce the loss of active metal ions, and extend the cycle life of the battery.

[0146] The third aspect of the present application provides a battery, the battery comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet obtained by the method described in the second aspect of the present application. Therefore, the battery of the embodiment of the present application has excellent cycle performance.

[0147] In some embodiments of the present application, the battery further includes an electrolyte, and the electrolyte plays a role of conducting ions between the positive electrode plate and the negative electrode plate. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0148] In some embodiments of the present application, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0149] In some embodiments of the present application, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0150] In some embodiments of the present application, when the battery is a lithium ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate or lithium tetrafluorooxalatophosphate.

[0151] In some embodiments of the present application, when the battery is a sodium ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0152] In some embodiments of the present application, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0153] Typically, a battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery charge and discharge process, active metal ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0154] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0155] In some embodiments, the material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0156] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0157] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0158] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite negative electrode current collector. For example, as the metal foil, aluminum foil may be used. The composite negative electrode current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.) on a substrate.

[0159] In some embodiments of the present application, the positive electrode active material may be a positive electrode active material for a battery known in the art.

[0160] As an example, when the positive electrode plate is used in a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or at least one of its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, or a composite material of lithium iron manganese phosphate and carbon.

[0161] As an example, when the positive electrode plate is used for a sodium ion battery, the positive electrode active material may be a positive electrode active material for a sodium ion battery known in the art. As an example, the positive electrode active material may include but is not limited to at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue analog.

[0162] Examples of the layered transition metal oxides include:

[0163] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 Including at least one of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn or Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0164] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M2 including at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn or Ba, where 0 < z ≤ 0.1;

[0165] Na a Li b Ni c Mn d Fe e O2, where 0.67 < a ≤ 1, 0 < b < 0.2, 0 < c < 0.3, 0.67 < d + e < 0.8, and b + c + d + e = 1.

[0166] As an example of the above polyanion compound, for example, the following can be listed:

[0167] A 1 f M 3 g (PO4) i O j X 1 3-j , where A 1 includes at least one of H, Li, Na, K or NH4, M 3 includes at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu or Zn, X 1 is at least one of F, Cl or Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0168] Na n M 4 PO4X 2 , where M 4 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, X 2 is at least one of F, Cl or Br, 0 < n ≤ 2;

[0169] Na p M 5 q (SO4)3, where M 5 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0170] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2 or 3.

[0171] As an example of the above Prussian blue analog, for example, the following can be listed:

[0172] A u M 6 v [M 7 (CN)6] w ·xH2O, wherein A includes H + , NH4 + , at least one of an alkali metal cation or an alkaline earth metal cation, M 6 and M 7 each independently includes at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A includes H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ or Ra 2+ at least one of, M 6 and M 7 each independently includes at least a cation of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn or W.

[0173] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li or Na will occur, and the molar content of Li or Na is different when the battery is discharged to different states. In the listing of the positive electrode material in this application, the molar content of Li or Na is the initial state of the material, that is, the state before feeding. When the positive electrode material is applied to the battery system, after charge and discharge cycling, the molar content of Li or Na will change.

[0174] In the listing of the positive electrode material in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will show fluctuations.

[0175] In some embodiments of this application, the positive electrode active material layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer or fluorinated acrylate resin.

[0176] In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0177] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0178] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0179] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0180] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0181] The present application has no particular limitation on the shape of the battery, which may be cylindrical, square or any other shape. For example, Figure 3 The battery cell 1 is a square structure as an example.

[0182] In some embodiments, reference Figure 4 The outer packaging may include a shell 11 and a cover plate 13. Among them, the shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0183] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0184] Figure 5 2 is an example of a battery module 2. Figure 5 In the battery module 2, the plurality of battery cells 1 may be arranged in sequence along the length direction of the battery module 2. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 1 may be fixed by fasteners.

[0185] Optionally, the battery module 2 may further include a housing having a receiving space, and the plurality of battery cells 1 are received in the receiving space.

[0186] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0187] Figure 6 and Figure 7 The battery pack 3 is used as an example. Figure 6 and Figure 7 The battery pack 1 may include a battery box and a plurality of battery modules 2 disposed in the battery box. The battery box includes an upper box body 31 and a lower box body 32. The upper box body 31 can cover the lower box body 32 and form a closed space for accommodating the battery modules 2. The plurality of battery modules 2 can be arranged in the battery box in any manner.

[0188] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0189] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0190] Figure 8 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0191] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery may be used as a power source.

[0192] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0193] The monomers of the polymers represented by formula I in Examples 1-44 and the monomers in Comparative Examples 2-4 were purchased from Aladdin.

[0194] Example 1

[0195] 1. Preparation of positive electrode sheet

[0196] Preparation of positive electrode

[0197] The positive electrode active material (LFP, etc.), conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) in a mass ratio of 96%:2%:2%, and the mixture is fully stirred and mixed to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the positive electrode current collector aluminum foil, and then dried at 100°C, cold pressed at 40T, and cut to obtain a positive electrode sheet.

[0198] 2. Preparation of negative electrode sheet

[0199] The negative electrode active material graphite, the monomer of the polymer shown in Formula I, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a proper amount of deionized water solvent system in a weight ratio of 95.5%:1%:0.7%:1.8%:1% to obtain a slurry, which is then coated on both sides of the Cu foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0200] 3. Preparation of electrolyte

[0201] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), EC (ethylene carbonate), EMC (ethyl methyl carbonate) and DMC (dimethyl carbonate) were mixed at a volume ratio of 1:1:1 to obtain a solvent, and the fully dried electrolyte salt LiPF6 was dissolved in the above solvent. After mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0202] 4. Isolation film

[0203] PE (polyethylene) porous polymer film is used as the isolation membrane.

[0204] 5. Preparation of secondary batteries

[0205] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then they are wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum packaging, standing, forming, and shaping processes, a lithium-ion battery is obtained.

[0206] The preparation methods of the lithium-ion batteries of Examples 2-18 and Comparative Examples 1 and 2 are the same as that of Example 1, except that the preparation methods of the negative electrode plates are different, as shown in Table 1.

[0207] Embodiment 19

[0208] Preparation of negative electrode

[0209] The monomer of the polymer represented by formula I is dissolved in water to form a slurry, and then the negative electrode active material graphite is immersed in the slurry, and then concentrated and dried to obtain a negative electrode active material with the monomer of the polymer represented by formula I coated on the surface, and the mass ratio of graphite to the monomer of the polymer represented by formula I is 95.5:1;

[0210] The negative electrode active material whose surface is coated with the monomer of the polymer shown in Formula I, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a proper amount of deionized water solvent system in a weight ratio of 96.5%:0.7%:1.8%:1% to obtain a slurry, which is then coated on the double-side surfaces of the Cu foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0211] The remaining steps such as the preparation of the positive electrode sheet, electrolyte, isolation membrane and lithium-ion battery are the same as those in Example 1.

[0212] The preparation methods of the lithium-ion batteries of Examples 20-22 are the same as that of Example 19, except that the monomers of the polymers represented by Formula I are different, as shown in Table 1.

[0213] Table 1

[0214]

[0215]

[0216]

[0217] Embodiment 23

[0218] Preparation of negative electrode

[0219] The negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a proper amount of deionized water solvent system in a weight ratio of 95.5%:1.5%:2%:1% to obtain a slurry, which is then coated on both sides of the Cu foil, and a negative electrode active material layer is formed on both sides of the negative electrode current collector by drying and cold pressing (the thickness of the single-side negative electrode active material layer is 0.15 mm);

[0220] The negative electrode active material graphite, the monomer of the polymer shown in Formula I, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a proper amount of deionized water solvent system in a weight ratio of 95.5%:1%:0.7%:1.8%:1% to obtain a slurry, which is then coated on the double side surfaces of the negative electrode active material layer. A protective layer (with a thickness of 100 μm) is formed on the negative electrode active material layer through drying and cold pressing, and finally, a negative electrode sheet is obtained through striping and cutting processes.

[0221] The remaining steps such as the preparation of the positive electrode sheet, electrolyte, isolation membrane and lithium-ion battery are the same as those in Example 1.

[0222] The preparation methods of the lithium-ion batteries of Examples 24-40 and Comparative Examples 3-4 are the same as that of Example 23, except that the preparation methods of the negative electrode plates are different, as shown in Table 2.

[0223] Embodiment 41

[0224] Preparation of negative electrode

[0225] The negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a proper amount of deionized water solvent system in a weight ratio of 95.5%:1.5%:2%:1% to obtain a slurry, which is then coated on both sides of the Cu foil, and a negative electrode active material layer is formed on both sides of the negative electrode current collector by drying and cold pressing (the thickness of the single-side negative electrode active material layer is 0.15 mm);

[0226] The monomer of the polymer represented by formula I is dissolved in water to form a slurry, and then the negative electrode active material graphite is immersed in the slurry, and then concentrated and dried to obtain a negative electrode active material with the monomer of the polymer represented by formula I coated on the surface, and the mass ratio of graphite to the monomer of the polymer represented by formula I is 95.5:1;

[0227] A negative electrode active material having a surface coated with a monomer of a polymer represented by Formula I, a conductive agent acetylene black, a binder styrene-butadiene rubber (SBR), and a thickener sodium carboxymethyl cellulose (CMC) are stirred and mixed in a proper amount of deionized water solvent system in a weight ratio of 96.5%:0.7%:1.8%:1% to obtain a slurry, which is then coated on both sides of the negative electrode active material layer (with a thickness of 100 μm), and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0228] The remaining steps such as the preparation of the positive electrode sheet, electrolyte, isolation membrane and lithium-ion battery are the same as those in Example 1.

[0229] The preparation methods of the lithium-ion batteries of Examples 42-44 are the same as that of Example 41, except that the monomers of the polymers represented by Formula I are different, as shown in Table 2.

[0230] Table 2

[0231]

[0232]

[0233]

[0234]

[0235] The cycle performance and DC resistance of the lithium ion batteries obtained in Examples 1-44 and Comparative Examples 1-4 were characterized. The characterization results are shown in Table 3.

[0236] (1) Cycle performance test of lithium-ion batteries:

[0237] The ambient temperature was controlled at 25°C, the battery was charged to 4.25V at 1C, then charged to 0.05C at a constant voltage, left to stand for 10 minutes, and then discharged to 2.8V at 1C. The discharge capacity was recorded as C0. 300 cycles were performed according to the above charge and discharge process. The discharge capacity of the 300th cycle was C1, and the cycle capacity retention rate of the battery cell = C1 / C0*100%.

[0238] (2) DC resistance test of lithium-ion battery: DCR (mohm)

[0239] The ambient temperature was controlled at 25°C, the battery was charged to 4.25V at 1C, then charged to 0.05C at a constant voltage, left to stand for 30 minutes, then discharged at 1C for 0.5h, left to stand for 30 minutes, and the voltage V1 after standing was recorded, then discharged at 4C for 30s with a sampling interval of 0.1S, and the voltage V2 at the end of discharge was recorded, the battery DCR (DC internal resistance) = (V1-V2) / I, I = 4C.

[0240] (3) Electropolymerization potential test of the monomer of the polymer represented by formula I:

[0241] Characterization by button cell:

[0242] Preparation of negative electrode sheet:

[0243] The negative electrode active material graphite, the monomer of the polymer shown in Formula I, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a proper amount of deionized water solvent system at a weight ratio of 95.5:1:0.7:1.8:1 to obtain a negative electrode slurry, and the negative electrode slurry is coated on the surface of one side of the copper foil and then dried and cold pressed to form a negative electrode active material layer on the surface of one side of the negative electrode current collector, and finally punched to obtain a negative electrode sheet;

[0244] Preparation of positive electrode:

[0245] The positive electrode active material (LiFePO4), conductive carbon (SP), and binder (polyvinylidene fluoride PVDF) are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2, and the mixture is fully stirred and mixed to prepare a positive electrode slurry. The positive electrode slurry is coated on one side of an aluminum foil, and then dried and cold pressed to form a positive electrode active material layer on the one side of the aluminum foil. Finally, the positive electrode sheet is obtained by punching.

[0246] Preparation of isolation membrane:

[0247] A polyethylene porous polymer film was used as the isolation membrane (thickness 7 μm);

[0248] Preparation of electrolyte

[0249] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) are mixed in a mass ratio of 1:1:1 to obtain a solvent, and fully dried electrolyte salt LiPF6 is dissolved in the above solvent. After mixing evenly, an electrolyte solution with a concentration of 1 mol / L is obtained.

[0250] Assembly: stack a single positive electrode sheet, a single separator, and a single negative electrode sheet in order (the side of the positive electrode sheet where the positive electrode active material layer is formed contacts the separator, and the side of the negative electrode sheet where the negative electrode active material layer is formed contacts the separator), place the separator between the positive and negative electrodes to play a role of isolation, add electrolyte, and obtain a CR2032 button-type full battery (capacity ≤5mAh) through pressure packaging (50MPa).

[0251] The button-type full battery as an experimental example was charged and discharged at a rate of 0.1C at 25°C, and the capacity (Q)-voltage (V) curve of the first cycle was recorded. The dQ / dV-V curve was obtained by differentiating it. At the same time, the button-type full battery of the control group (the monomer of the polymer shown in Formula I was not added to the negative electrode plate, wherein the negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) were in a weight ratio of 96.5:0.7:1.8:1, and the rest were the same as the above button-type full battery) was used to obtain the dQ / dV-V curve under the same conditions. By comparing the two curves, an additional peak can be seen from the dQ / dV-V curve of the button-type full battery of the experimental example. The peak is the characteristic peak of the small molecule additive, and the ordinate corresponding to the peak is the electropolymerization potential of the monomer of the polymer shown in Formula I.

[0252] The test results are shown in Table 3.

[0253] Table 3

[0254]

[0255]

[0256] Conclusion: Compared with Comparative Example 1-2, the negative electrode active material layer of the negative electrode plate of Example 1-22 contains the polymer shown in Formula I, while the negative electrode plate of Comparative Example 1 does not contain the polymer shown in Formula I, and other polymers are added to the negative electrode plate of Comparative Example 2. It can be seen from Table 3 that the cycle performance of the lithium ion battery of Example 1-22 is better than that of Comparative Example 1-2, and the DC resistance of the lithium ion battery of Example 1-22 is lower than that of Comparative Example 1-2, indicating that by containing the polymer shown in Formula I of the embodiment of the present application in the negative electrode active material layer, the cycle performance of the lithium ion battery can be improved and the branch current internal resistance of the lithium ion battery can be reduced.

[0257] Compared with Comparative Examples 3-4, the protective layer of the negative electrode sheet of Examples 23-44 contains the polymer shown in Formula I, while the negative electrode sheet of Comparative Example 3 does not contain the polymer shown in Formula I, and other polymers are added to the protective layer of the negative electrode sheet of Comparative Example 4. It can be seen from Table 3 that the cycle performance of the lithium ion battery of Examples 23-44 is better than that of Comparative Examples 3-4, and the DC resistance of the lithium ion battery of Examples 23-44 is lower than that of Comparative Examples 3-4, indicating that by adding the polymer shown in Formula I of the embodiments of the present application to the protective layer of the negative electrode sheet, the cycle performance of the lithium ion battery can be improved and the branch current internal resistance of the lithium ion battery can be reduced.

[0258] In summary, the negative electrode sheet of the present application contains the polymer represented by formula I, which can improve the cycle performance of the lithium-ion battery and reduce the branch current internal resistance of the lithium-ion battery.

[0259] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode plate, characterized in that: Including polymers represented by formula I: wherein R1, R2 and R3 each independently include at least one of H atoms, halogen, aryl, carboxyl, substituted or unsubstituted hydrocarbon groups of 1 to 5 carbon atoms, Q1 includes at least one of the groups shown in formula II, groups containing boron atoms or halogen, and n is 5 to 100; In formula II, R4, R5 and R6 each independently include at least one of an H atom, a group containing a boron atom, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms, and at least one of R4, R5 and R6 includes at least one of a group containing a boron atom, a nitro group, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms.

2. The negative electrode sheet according to claim 1, characterized in that: The weight average molecular weight of the polymer represented by formula I is 300-50,000, and can be optionally 300-5,000.

3. The negative electrode sheet according to claim 1 or 2, characterized in that: The boron atom-containing group includes at least one of -B(OH)2, -BF3, -BCl3, -BBr3 or -B(C6F5)3.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The halogen includes at least one of -F, -Cl, -Br or -I.

5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that: The substituent when the hydrocarbon group of 1 to 5 carbon atoms is substituted includes at least one of a carboxyl group, a hydroxyl group or an aryl group.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The polymer represented by formula I includes at least one of the substances represented by the following structural formulas: n is 5-100.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The negative electrode plate also includes a negative electrode active material, and the polymer shown in Formula I is coated on at least a portion of the surface of the negative electrode active material.

8. The negative electrode sheet according to any one of claims 1 to 7, characterized in that: The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the current collector, and the negative electrode active material layer includes a polymer shown in Formula I.

9. The negative electrode sheet according to claim 8, characterized in that: Based on the total mass of the negative electrode active material layer, the mass proportion of the polymer represented by Formula I is 0.01%-4.5%, and can be optionally 0.5%-2%.

10. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The negative electrode plate comprises: Anode current collector; a negative electrode active material layer formed on at least one side of the negative electrode current collector; A protective layer is formed on a side of the negative electrode active material layer away from the negative electrode current collector, and the protective layer comprises a polymer represented by Formula I.

11. The negative electrode sheet according to claim 10, characterized in that: Based on the total mass of the protective layer, the mass proportion of the polymer represented by Formula I is 0.01%-4.5%, and can be optionally 0.5%-2%.

12. A method for preparing a negative electrode sheet, characterized in that: include: forming a negative electrode sheet comprising a polymer represented by Formula I; wherein R1, R2 and R3 each independently include at least one of H atoms, halogen, aryl, carboxyl, substituted or unsubstituted hydrocarbon groups of 1 to 5 carbon atoms, Q1 includes at least one of the groups shown in formula II, groups containing boron atoms or halogen, and n is 5 to 100; In formula II, R4, R5 and R6 each independently include at least one of an H atom, a group containing a boron atom, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms, and at least one of R4, R5 and R6 includes at least one of a group containing a boron atom, a nitro group, a halogen, a carboxyl group, a hydroxyl group, and a hydrocarbon group having 1 to 3 carbon atoms.

13. The method according to claim 12, characterized in that include: forming a negative electrode active material layer including a monomer of a polymer represented by Formula I and a negative electrode active material on at least one side of the negative electrode current collector; The monomers of the polymer represented by formula I are polymerized to obtain a negative electrode plate.

14. The method according to claim 12, characterized in that include: forming a negative electrode active material layer on at least one side of the negative electrode current collector; forming a protective layer on the negative electrode active material layer at a side away from the negative electrode current collector, wherein the protective layer comprises a monomer of the polymer represented by formula I; The monomers of the polymer represented by formula I are polymerized to obtain a negative electrode plate.

15. The method according to claim 13 or 14, wherein the monomers of the polymer represented by formula I are polymerized under the action of an electric field, wherein the voltage of the electric field is 1.6V-2.5V, and can be optionally 1.6V-2.2V.

16. The method according to any one of claims 13 to 15, characterized in that The electropolymerization potential of the monomer of the polymer represented by formula I is 1.6V-2.5V, and can be optionally 1.6V-2.2V.

17. The method according to any one of claims 13 to 16, characterized in that The monomer of the polymer represented by formula I includes at least one of the substances represented by the following structural formulas:

18. The method according to any one of claims 12 to 17, characterized in that: include: The monomer of the polymer shown in formula I is coated on the surface of the negative electrode active material to prepare a negative electrode plate.

19. The method according to any one of claims 12 to 18, characterized in that: At 25°C, the solubility of the monomer of the polymer represented by formula I in 100g of water is ≥0.01g. Optionally, at 25°C, the solubility of the monomer of the polymer represented by formula I in 100g of water is ≥1g.

20. A battery, characterized in that: A negative electrode sheet comprising the negative electrode sheet according to any one of claims 1 to 11 or a negative electrode sheet obtained by the method according to any one of claims 12 to 19.

21. An electrical equipment, characterized in that: Comprising the battery of claim 20.

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