Electrode plate, battery and electric device

Abstract

The invention relates to an electrode plate, a battery and an electric device. The electrode pole piece comprises a current collector and a film layer arranged on at least one side of the current collector, the film layer comprises an active substance and multiple fluorinated polymers, the crystallinity of one of the multiple fluorinated polymers is marked as Xc < 1 >%, the cold crystallization temperature is marked as Tc < 1 > DEG C, the crystallinity of the other one of the multiple fluorinated polymers is marked as Xc < 2 >%, and the cold crystallization temperature is marked as Tc < 1 > DEG C. The cold crystallization temperature is recorded as Tc2 DEG C, and the various fluorinated polymers meet the following conditions: (Xc2-Xc1) / Xc1 is more than or equal to 20% and less than 400%, and (Tc2-Tc1) / Tc1 is more than or equal to 30% and less than 250%.

Description

Technical Field

[0001] The present application relates to an electrode plate, a battery and an electrical device. Background Art

[0002] Batteries have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes and electric tools, etc.

[0003] As battery applications become more and more extensive, the requirements for battery performance are becoming increasingly stringent. However, the cycle life and storage life of batteries are still poor and need to be further improved. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide an electrode plate, a battery and an electrical device.

[0005] In a first aspect, the present application proposes an electrode plate, the electrode plate comprising a current collector and a film layer disposed on at least one side of the current collector, the film layer comprising an active material and a plurality of fluorinated polymers,

[0006] The crystallinity of one of the fluorinated polymers is denoted as X. c1 %, and the cold crystallization temperature is recorded as T c1 ℃;

[0007] The crystallinity of another fluorinated polymer among the multiple fluorinated polymers is denoted as X. c2 %, and the cold crystallization temperature is recorded as T c2 ℃,

[0008] Among them, a variety of fluorinated polymers meet the following requirements: 20% ≤ (X c2 -X c1 ) / X c1 <400%,30%≤(T c2 -T c1 ) / T c1 <250%.

[0009] Therefore, the crystallinity X of the first fluorinated polymer in the embodiment of the present application is c1 % is relatively small, the cold crystallization temperature T c1 ℃ is relatively low, the flexibility of the molecular chain is stronger, which is more conducive to the first fluorinated polymer to form an in-situ gel on the surface of the active material particles and improve the solid-liquid interface performance; the first fluorinated polymer and the second fluorinated polymer have similar structures. Compared with the first fluorinated polymer, the crystallinity X of the second fluorinated polymer is c2 % is relatively large, the cold crystallization temperature T c2℃ is relatively high, and the higher the energy required to release the intermolecular constraints, the more conducive it is to improving its own cohesive energy density, reducing swelling and deformation, and enhancing the binding force between active substances; therefore, the embodiments of the present application can effectively improve the cycle performance and storage performance of battery monomers through the mutual cooperation of multiple fluorinated polymers.

[0010] In some embodiments, 40%≤(X c2 -X c1 ) / X c1 <400%; Optionally, X c2 -X c1 ≥10; further optionally, 10≤X c2 -X c1 ≤45. The embodiments of the present application can further improve the cycle performance and storage performance of the electrode plate when applied to a battery cell by further selecting the crystallinity and cold crystallization temperature of the fluorinated polymer.

[0011] In some embodiments, 0<X c1 ≤28; and / or 30≤X c2 ≤50.

[0012] In some embodiments, 35%≤(T c2 -T c1 ) / T c1 <250%; Optionally, T c2 -T c1 ≥25; further optionally, 25≤T c2 -T c1 ≤100.

[0013] In some embodiments, further optionally, 35<T c1 ≤100; and / or 115≤T c2 ≤140.

[0014] In some embodiments, each of the plurality of fluorinated polymers independently comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII),

[0015]

[0016] In formula (AI) and formula (AII), R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13and R 14 At least one of them contains a fluorine atom;

[0017]

[0018] In formula (AIII), R 15 Including single bonds, substituted or unsubstituted C1-C3 alkyl;

[0019] p is a positive integer selected from 1 to 3;

[0020] n is a positive integer selected from 1,000 to 30,000.

[0021] In some embodiments, one of the plurality of fluoropolymers has a molecular weight of W1 g / mol, another of the plurality of fluoropolymers has a molecular weight of W2 g / mol,

[0022] A variety of fluorinated polymers meet: 0<W 1 / W2<1; optionally, 2.0×10 5 ≤W1≤1.0×10 6 ; 5.0×10 5 ≤W2≤1.2×10 6 The first fluorinated polymer has a relatively small molecular weight and a stronger affinity with the solvent, but has a higher risk of being dispersed by the solvent, which is not conducive to regulating its position distribution; the second fluorinated polymer has a relatively high molecular weight, longer molecular segments, a higher probability of contact and entanglement between molecular segments, and an increased intermolecular force, which can enhance the binding force between active substances, and significantly reduce the interaction with solvent molecules, making it easier to regulate its dispersion position; the combination of the two is more conducive to improving both the interfacial side reactions and structural stability in the positive electrode sheet, thereby improving the cycle performance and storage performance of the battery cell.

[0023] In some embodiments, based on the total mass of the film layer, the total mass content of the multiple fluoropolymers is ≤5%; optionally, it is 0.05% to 5%; optionally, based on the total mass of the film layer, the mass content of the first fluoropolymer is ≤4%; optionally, based on the total mass of the film layer, the mass content of the second fluoropolymer is ≤4%. When the mass content of the multiple fluoropolymers is within the above range, the multiple fluoropolymers can effectively improve the interface performance and structural stability of the electrode plate. The mass content of the multiple fluoropolymers refers to the sum of the mass content of each fluoropolymer in the multiple fluoropolymers.

[0024] In a second aspect, the present application proposes a battery, comprising an electrode plate according to any embodiment of the first aspect of the present application.

[0025] In some embodiments, the electrode plate includes a positive electrode plate, the positive electrode plate includes a positive electrode collector and a positive electrode film layer disposed on at least one side of the positive electrode collector, and the positive electrode film layer includes a positive electrode active material, a first fluorinated polymer, and a second fluorinated polymer.

[0026] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the first fluorinated polymer and the total mass content of the second fluorinated polymer is 0.05% to 2.5%.

[0027] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the first fluorinated polymer is less than the mass content of the second fluorinated polymer.

[0028] In some embodiments, based on the total mass of the positive electrode film layer, the total mass content of the first fluorinated polymer is ≤2%; optionally 0.05% to 2%; optionally 0.05% to 1%.

[0029] In some embodiments, based on the total mass of the positive electrode film layer, the total mass content of the second fluorinated polymer is ≤2%; optionally 1% to 2%; optionally 1.2% to 2%.

[0030] In some embodiments, the electrode plate includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material, a first fluorinated polymer, and a second fluorinated polymer.

[0031] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer and the total mass content of the second fluorinated polymer is 0.05% to 5%.

[0032] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is greater than the mass content of the second fluorinated polymer.

[0033] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is less than the mass content of the second fluorinated polymer.

[0034] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is ≤4%; optionally, it is 0.5% to 4%.

[0035] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the second fluorinated polymer is ≤4%; optionally, it is 0.4% to 2%.

[0036] In a third aspect, the present application proposes an electrical device, comprising a battery as in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0038] Figure 1 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0039] Figure 2 yes Figure 1 An exploded schematic diagram of an embodiment of a battery cell.

[0040] Figure 3 It is a schematic diagram of an embodiment of a battery module of the present application.

[0041] Figure 4 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0042] Figure 5 yes Figure 4 An exploded schematic diagram of an embodiment of a battery pack is shown.

[0043] Figure 6 It is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0044] The drawings are not necessarily drawn to scale.

[0045] The following are the descriptions of the reference numerals:

[0046] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module;

[0047] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0048] 53. Cover plate;

[0049] 6. Electrical equipment. DETAILED DESCRIPTION

[0050] Below, the embodiments of the electrode plates, batteries and electrical devices of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0051] "Scope" disclosed in the present application is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The scope defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 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 range can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" 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 to 5" means that all real numbers between "0 to 5" are listed in this document, and "0 to 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.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0053] 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.

[0054] 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.

[0055] In the embodiments of the present application, the terms "plurality" and "multiple" refer to two or more.

[0056] The term "alkyl" encompasses both straight and branched chain alkyl groups. For example, the alkyl group may be a C1 to C5 alkyl group, a C1 to C4 alkyl group, a C1 to C3 alkyl group, a C1 to C2 alkyl group. In some embodiments, the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, etc. In addition, the alkyl group may be optionally substituted. When substituted, the substituent includes a fluorine atom.

[0057] The term "alkoxy" refers to a group in which an alkyl group is connected to an oxygen atom by a single bond. For example, the alkoxy group can be a C1 to C5 alkoxy group, a C1 to C3 alkoxy group, a C1 to C2 alkoxy group. In some embodiments, the alkoxy group can include a methoxy group, an ethoxy group, a propoxy group. In addition, the alkoxy group can be optionally substituted.

[0058] The term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom or the like.

[0059] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D) or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

[0060] The battery includes an electrode assembly and an electrolyte. The electrode assembly includes electrode plates and a separator. The electrode plates include a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive electrode film layer containing a positive electrode active substance. The positive electrode active substance can provide active ions. The negative electrode plate includes a negative electrode film layer containing a negative electrode active substance. The separator is arranged between the positive electrode plate and the negative electrode plate. It mainly prevents the positive electrode plate and the negative electrode plate from short-circuiting, and allows the active ions to pass freely to form a loop.

[0061] There is a solid-liquid contact interface between the electrode plate and the electrolyte. During the battery's charge and discharge cycle, the electrode plate may expand in volume, causing the interface to be destroyed and a new interface to be formed. The formation of a new interface will lead to the continuous occurrence of interfacial side reactions, deteriorating the cycle performance and storage performance of the battery cell.

[0062] In view of the above problems, the embodiments of the present application improve the cycle performance and storage performance of the battery cell from the perspective of improving the interfacial performance of the solid-liquid contact interface. The embodiments of the present application propose an electrode plate, which includes a plurality of fluoropolymers, at least two of which are made of different materials, one of which can form an in-situ gel on the surface of the solid-phase active substance, that is, a stable solid-liquid interface is formed on the surface of the active substance, reducing the risk of side reactions at the solid-liquid interface; however, this fluoropolymer is not conducive to the bonding between the active substances, resulting in poor structural stability of the electrode plate, and another fluoropolymer among the plurality of fluoropolymers can enhance the bonding force between the active substances, play a role in supporting the plate, thereby improving the structural stability of the electrode plate, thereby improving the cycle performance and storage performance of the battery cell.

[0063] Next, the technical solution of this application is described in detail.

[0064] Electrode

[0065] In a first aspect, an embodiment of the present application proposes an electrode plate.

[0066] The electrode plate includes a current collector and a film layer disposed on at least one side of the current collector, the film layer includes an active material and a plurality of fluorinated polymers, and the crystallinity of one of the fluorinated polymers is denoted as X c1 %, and the cold crystallization temperature is recorded as T c1 ℃, the crystallinity of another fluorinated polymer among the multiple fluorinated polymers is recorded as X c2 %, and the cold crystallization temperature is recorded as T c2 ℃, among which, a variety of fluorinated polymers meet: 20% ≤ (X c2 -X c1 ) / X c1 <400%,30%≤(T c2 -T c1 ) / T c1 <250%.

[0067] The electrode sheet may include at least one of a positive electrode sheet and a negative electrode sheet; for example, the electrode sheet includes a positive electrode sheet, the positive electrode sheet includes a positive electrode collector and a positive electrode film layer disposed on at least one side of the positive electrode collector, and the positive electrode film layer includes a positive electrode active material and a plurality of fluorinated polymers. For another example, the electrode sheet includes a negative electrode sheet, the negative electrode sheet includes a negative electrode collector and a negative electrode film layer disposed on at least one side of the negative electrode collector, and the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers. For another example, the electrode sheet includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet includes a positive electrode collector and a positive electrode film layer disposed on at least one side of the positive electrode collector, the positive electrode film layer includes a positive electrode active material and a plurality of fluorinated polymers, the negative electrode sheet includes a negative electrode collector and a negative electrode film layer disposed on at least one side of the negative electrode collector, and the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers.

[0068] In the present application, each fluoropolymer in the plurality of fluoropolymers is a polymer including fluorine atoms. One of the plurality of fluoropolymers is defined as a first fluoropolymer, and another of the plurality of fluoropolymers is defined as a second fluoropolymer; when the plurality of fluoropolymers also includes a third fluoropolymer, the third fluoropolymer is defined as a third fluoropolymer, and so on. The more types of fluoropolymers there are, the more the cycle performance and storage performance of the battery cell can be improved by using a plurality of fluoropolymers in combination.

[0069] The first fluoropolymer has good affinity with the electrolyte in the battery cell, and can swell when the first fluoropolymer contacts the electrolyte. The solvent in the electrolyte can quickly diffuse between the molecular chains of the first fluoropolymer and be wrapped by the molecular chains, and can form an in-situ gel on the surface of the active material, and adhere to the surface of the active material to protect the active material, thereby closely connecting the active material and the electrolyte, improving the solid-liquid interface performance, and reducing the side reaction between the active material and the electrolyte. However, due to the poor solvent resistance of the first fluoropolymer, it is not conducive to closely bonding the active materials together, especially in the case of expansion and contraction of the active material in the late cycle, the binding force between the active materials is poor, so that the structural stability of the electrode plate is poor; the second fluoropolymer is also included in the embodiment of the present application, and the second fluoropolymer has good solvent resistance, and the second fluoropolymer itself has a high cohesive energy density, which can slow down its own swelling and deformation, and improve the binding force between the active materials, thereby improving the structural stability of the electrode plate, and improving the cycle performance and storage performance of the battery cell.

[0070] The crystallinity X of the first fluorinated polymer c1 % is relatively small, the cold crystallization temperature T c1 ℃ is relatively low, the flexibility of the molecular chain is stronger, which is more conducive to the first fluorinated polymer to form an in-situ gel on the surface of the active material particles and improve the solid-liquid interface performance; the first fluorinated polymer and the second fluorinated polymer have similar structures. Compared with the first fluorinated polymer, the crystallinity X of the second fluorinated polymer is c2 % is relatively large, the cold crystallization temperature T c2 ℃ is relatively high, and the higher the energy required to release the intermolecular constraints, the more conducive it is to improving its own cohesive energy density, reducing swelling and deformation, and enhancing the binding force between active substances; therefore, the embodiments of the present application can effectively improve the cycle performance and storage performance of battery monomers through the mutual cooperation of multiple fluorinated polymers.

[0071] Crystallization refers to the process in which atoms, ions or molecules in a material are arranged in a certain spatial order to form an orderly structure. The conformation of the polymer in the crystallization is determined by both intramolecular and intermolecular factors. Intermolecular forces will affect the packing density between molecular chains. C % is used to characterize the degree of crystallization in the material, and the cold crystallization temperature T c ℃ is the crystallization temperature of the material during the cooling process after melting. The above two parameters can be measured by differential scanning calorimetry (DSC). Specifically, the test steps are as follows: take 0.5g to 0.8g of sample, place the sample in a carrier crucible, and heat and cool the sample in a nitrogen atmosphere at a heating rate of 10℃ / min, from the intrinsic T g The initial temperature is 20℃ lower than the material's intrinsic T m℃, keep the temperature constant for 5 minutes, record the first heating curve; then cool down at a rate of 10℃ / min to a temperature lower than the intrinsic T g The temperature of the material is 20℃ lower than the cut-off temperature, and the cooling curve is recorded. The peak value or transition point of the material's endothermic and exothermic properties during the cooling process is the actual cold crystallization temperature T of the material. c ℃, calculate the peak area corresponding to each peak of the cooling curve to get the crystallization enthalpy, and the ratio of the crystallization enthalpy to the standard enthalpy is the crystallinity X C % etc. The crystallinity in the embodiments of the present application refers to the crystallinity measured by differential scanning calorimetry.

[0072] The embodiments of the present application can further improve the cycle performance and storage performance of the electrode plate when applied to a battery cell by further selecting the crystallinity and cold crystallization temperature of the fluorinated polymer.

[0073] In the implementation mode of the present application, 20%≤(X c2 -X c1 ) / X c1 <400%; optionally, 40%≤(X c2 -X c1 ) / X c1 <400%. For example, (X c2 -X c1 ) / X c1 It can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 220%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, 300%, 310%, 320%, 330%, 340%, 350%, 360%, 370%, 380%, 390%, 400%, 410%, 420%, 430%, 440%, 450%, 460%, 470%, 480%, 490%, 500%, 510%, 520%, 530%, 540%, 550%, 560%, 570%, 580%, 590%, 600%, 610%, 620%, 630%, 640%, 650%, 660%, 670%, 680%, 690%, 70 25%, 230%, 235%, 240%, 245%, 250%, 255%, 260%, 265%, 270%, 275%, 280%, 285%, 290%, 295%, 300%, 305%, 310%, 315%, 320%, 325%, 330%, 335%, 340%, 345%, 350%, 355%, 360%, 365%, 370%, 375%, 380%, 385%, 390%, 395% or a range consisting of any two of the above values.

[0074] In some embodiments, X c2 -X c1 ≥10; optionally, 10≤X c2 -X c1 ≤45. For example, X c2 -Xc1 The crystallinity of the second fluoropolymer may be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, or a range consisting of any two of the above values. In other words, the difference between the crystallinity of the second fluoropolymer and the crystallinity of the first fluoropolymer is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range consisting of any two of the above values.

[0075] In some embodiments, 0<X c1 ≤28. The crystallinity of the first fluorinated polymer measured by differential scanning calorimetry can be 5%, 10%, 15%, 20%, 25%, 28% or a range consisting of any two of the above values. c1 When % is less than 10%, the fluorinated polymer has almost no melting peak and the melting temperature may not be detected.

[0076] In some embodiments, 30≤X c2 ≤50. The crystallinity of the second fluorinated polymer measured by differential scanning calorimetry can be 30%, 35%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60% or a range consisting of any two of the above values. c2 When % is less than 10%, the fluorinated polymer has almost no melting peak and the melting temperature may not be detected.

[0077] In the implementation mode of the present application, 30%≤(T c2 -T c1 ) / T c1 <250%; optionally, 35%≤(T c2 -T c1 ) / T c1 <250%. For example, (T c2 -T c1 ) / T c1 The amount of the above-mentioned amount may be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 220%, 225%, 230%, 235%, 240%, 245%, 250% or a range consisting of any two of the above-mentioned values.

[0078] In some embodiments, T c2 -T c1 ≥25; further optionally, 25≤Tc2 -T c1 ≤100; for example, T c2 -T c1 The cold crystallization temperature of the second fluoropolymer may be 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or a range consisting of any two of the above values. In other words, the difference between the cold crystallization temperature of the second fluoropolymer and the cold crystallization temperature of the first fluoropolymer is 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or a range consisting of any two of the above values.

[0079] In some embodiments, 35 < T c1 ≤100. The cold crystallization temperature of the first fluorinated polymer may be 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 81°C, 85°C, 90°C, 95°C, 100°C or a range consisting of any two of the above values.

[0080] In some embodiments, 115≤T c2 ≤140. The cold crystallization temperature of the second fluorinated polymer may be 115°C, 118°C, 120°C, 122°C, 125°C, 128°C, 130°C, 132°C, 135°C, 138°C, 140°C or a range consisting of any two of the above values.

[0081] In some embodiments, the glass transition temperature of the first fluoropolymer is T g1 ℃, -30≤T g1 ≤40. Exemplarily, the glass transition temperature of the first fluorinated polymer may be -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or a range consisting of any two of the above values.

[0082] In some embodiments, the second fluorinated polymer has a glass transition temperature of T g1 ℃, -30≤T g1 ≤40. Illustratively, the glass transition temperature of the second fluorinated polymer may be -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or a range consisting of any two of the above values.

[0083] In some embodiments, each fluorinated polymer in the plurality of fluorinated polymers independently comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII).

[0084] When the plurality of fluoropolymers include a first fluoropolymer and a second fluoropolymer, the first fluoropolymer and the second fluoropolymer each independently include at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII), and the materials of the first fluoropolymer and the second fluoropolymer are different, and the materials can be specifically distinguished by different structural units and / or different degrees of polymerization.

[0085] When the plurality of fluoropolymers include a first fluoropolymer, a second fluoropolymer and a third fluoropolymer, the first fluoropolymer and the second fluoropolymer each independently include at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII), and the materials of the first fluoropolymer, the second fluoropolymer and the third fluoropolymer are different from each other, and the materials can be specifically distinguished by different structural units and / or different degrees of polymerization.

[0086] The compound represented by formula (AI) is as follows:

[0087]

[0088] In formula (AI), R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom.

[0089] Optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group.

[0090] Optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group.

[0091] Further optionally, R11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group or a perfluoromethoxy group.

[0092] In some embodiments, the degree of polymerization n of the fluorinated polymer is selected from a positive integer from 1000 to 30000, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or a range consisting of any two of the above values.

[0093] Alternatively, when substituted, the substituent may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom. The halogen atom may include a fluorine atom, a bromine atom, and the like, and may be optionally a fluorine atom.

[0094] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AI-1) to the compounds represented by formula (AI-11),

[0095]

[0096] The compound represented by formula (AII) is as follows:

[0097]

[0098] In formula (AII), R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom.

[0099] Optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group.

[0100] Optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group.

[0101] Further optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group or a perfluoromethoxy group.

[0102] In some embodiments, the degree of polymerization n of the fluorinated polymer is selected from a positive integer from 1000 to 30000, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or a range consisting of any two of the above values.

[0103] Alternatively, when substituted, the substituent may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom. The halogen atom may include a fluorine atom, a bromine atom, and the like, and may be optionally a fluorine atom.

[0104] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AII-1) to the compounds represented by formula (AII-5),

[0105]

[0106] The compound represented by formula (AIII) is as follows:

[0107]

[0108] In formula (AIII), R 15 Includes single bonds, substituted or unsubstituted alkyl groups; when substituted, substituents include fluorine atoms.

[0109] In some embodiments, when substituted, the substituent may include one or more of a nitrile group (—CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom.

[0110] Optionally, R 15 This includes single bonds, substituted or unsubstituted C1-C3 alkyl groups.

[0111] In some embodiments, p is selected from a positive integer of 1 to 3, such as 1, 2 or 3.

[0112] In some embodiments, the degree of polymerization n of the fluorinated polymer is selected from a positive integer from 1000 to 30000, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or a range consisting of any two of the above values.

[0113] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AIII-1) to the compounds represented by formula (AIII-3),

[0114]

[0115] Exemplarily, the fluorinated polymer includes one or more of polyperfluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroethylene propylene copolymer FEP, perfluoroalkoxy polymer PFA, perfluoropolyether PFPE, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE and perfluoro(1-butenyl vinyl ether) polymer (abbreviated as CYTOP).

[0116] Optionally, the fluorinated polymer includes one or more of polyperfluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propylene (FEP), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE).

[0117] The fluorinated polymer may be derived from one or more of the following monomers: fluorocycloethane, vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene and pentafluoropropylene, etc. Alternatively, the fluorinated polymer may be derived from at least two of the following monomers: fluorocycloethane, vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene and pentafluoropropylene.

[0118] In the embodiments of the present application, the polymer can also be obtained by copolymerizing the above structural groups with a small amount of other types of structural groups (e.g., olefin compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid, etc.). The lyophilic properties of such a small amount of monomers are relatively poor, and the above fluorinated polymer monomers are copolymerized with such monomers to improve the swelling rate and compression modulus of the fluorinated polymer.

[0119] In some embodiments, the molecular weight of the fluorinated polymer is 2×10 5 g / mol to 1.5×10 6 g / mol.

[0120] For example, the molecular weight of the fluorinated polymer may be 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol, 1.2×10 6 g / mol or a range consisting of any two of the above values.

[0121] In some embodiments, the molecular weight of the first fluorinated polymer is W1 g / mol, the molecular weight of the second fluorinated polymer is W2 g / mol, and the plurality of fluorinated polymers satisfy: 0<W 1 / W2<1. The molecular weight of the first fluorinated polymer is relatively small, and its affinity with the solvent is stronger, but the risk of being dispersed by the solvent is higher, which is not conducive to regulating its position distribution; the molecular weight of the second fluorinated polymer is relatively high, the molecular chain segments are longer, the probability of contact and entanglement between the molecular chains is increased, the intermolecular force is increased, and the binding force between the active substances can be improved, and the interaction with the solvent molecules will be significantly reduced, making it easy to regulate its dispersion position; the combination of the two is more conducive to improving the interface side reactions and structural stability in the positive electrode plate, thereby improving the cycle performance and storage performance of the battery cell. For example, W 1 / W2< can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95 or a range consisting of any two of the above values.

[0122] In some embodiments, 2.0×10 5 ≤W1≤1.0×10 6 For example, the molecular weight of the first fluorinated polymer may be 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1.0×10 6 g / mol or a range consisting of any two of the above values.

[0123] In some embodiments, 5.0×10 5 ≤W2≤1.5×10 6 For example, the molecular weight of the second fluorinated polymer may be 5×10 5 g / mol, 6×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol, 1.5×10 6 g / mol or a range consisting of any two of the above values.

[0124] The relevant parameters of the fluorinated polymer according to the embodiment of the present application can be detected by the following method:

[0125] The groups of the fluorinated polymers of the embodiments of the present application can be detected by infrared spectrophotometry IR. Specifically, the fluorinated polymers are tested by Thermo Nicolet Nexus 670 attenuated total reflection Fourier transform infrared spectrometer (FTIR-ATR), and then tested in accordance with standard GB / T6040-2002. The test range is: ATR method 600-4000cm -1 ; Repeatability: ±2cm -1 ; Resolution: better than 4cm -1 ; Transmission depth 0.2~0.6μm.

[0126] The structure of the fluorinated polymer according to the embodiment of the present application can be tested by nuclear magnetic resonance (NMR). Specifically, 1H NMR and 13C NMR are performed on a Varian Mercury Plus-400 NMR instrument at a test temperature of 20° C., TMS as an internal standard, CDCl3 as a solvent, and a proton resonance frequency of 400 MHz.

[0127] The polymer monomer type of the fluorinated polymer of the embodiment of the present application (especially suitable for monomers that account for a relatively small proportion in the polymer) can be tested by pyrolysis-gas chromatography-mass spectrometry, and the specific test steps are as follows: accurately weigh 0.5 mg of the sample and put it into the sample cup, fix it to the injection rod, and then put it into the pyrolyzer installed near the GC (gas chromatography) injection port. After the temperature of the pyrolyzer reaches the set temperature, press the injection button, and the sample cup quickly falls into the core of the pyrolysis furnace by free fall. In the inert gas N2 atmosphere, the volatile components are instantly vaporized and carried into the gas chromatography column by the carrier gas for separation. Finally, it is detected by a flame ionization detector FID or a mass spectrometer MS to obtain a gas chromatogram or a total ion flow diagram.

[0128] The molecular weight of the fluorinated polymer in the embodiment of the present application is well known in the art, and can be measured using equipment and methods commonly used in the art. It can be tested by gel permeation chromatography GPC in accordance with GB / T21863-2008. The specific test steps are: take an appropriate amount of the sample to be tested (the sample concentration is guaranteed to be 8%-12% shading), add 20 ml of deionized water, and simultaneously ultraviolet for 5 minutes (53KHz / 120W) to ensure that the sample is completely dispersed, and then the sample is measured in accordance with GB / T19077-2016 / ISO 13320:2009 standard.

[0129] [Positive electrode]

[0130] In some embodiments, the electrode plate includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material and a plurality of fluorinated polymers. In this case, the negative electrode plate may include a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers. Alternatively, the negative electrode plate may include a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material, i.e., does not contain a fluorinated polymer.

[0131] In other embodiments, the electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers. In this case, the positive electrode film layer may include a positive electrode active material, that is, does not include a fluorinated polymer.

[0132] Further research has found that when both the positive electrode film layer and the negative electrode film layer include multiple fluorinated polymers, the multiple fluorinated polymers can not only improve the interface performance and structural stability of the positive electrode plate, but also improve the interface performance and structural stability of the negative electrode plate, thereby effectively improving the cycle performance and storage performance of the battery cell.

[0133] In some embodiments, based on the total mass of the positive electrode film layer, the total mass content of the multiple fluorinated polymers is ≤5%; optionally 0.05% to 3%; optionally 0.05% to 2.5%. When the mass content of the multiple fluorinated polymers is within the above range, the multiple fluorinated polymers can effectively improve the interface performance and structural stability of the positive electrode sheet. The mass content of the multiple fluorinated polymers refers to the sum of the mass content of each fluorinated polymer in the multiple fluorinated polymers.

[0134] For example, the total mass content of the plurality of fluorinated polymers may be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.6%, 1.7%, 1.8%, 1.9%, 1.9% or more. .3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range consisting of any two of the above values.

[0135] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the first fluorinated polymer is less than the mass content of the second fluorinated polymer; when multiple fluorinated polymers meet the above conditions, the interface performance and structural stability of the positive electrode plate can be further improved.

[0136] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the first fluorinated polymer is ≤2%; it can be selected from 0.05% to 2%; it can be selected from 0.05% to 1%, for example, 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.3 5%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0% or a range consisting of any two of the above values.

[0137] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the second fluorinated polymer is ≤2%; it can be optionally 1% to 2%; it can be optionally 1.2% to 2%, for example, 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35% , 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0% or a range consisting of any two of the above values.

[0138] In the embodiments of the present application, the mass content of the polymer has a well-known meaning in the art, and can be detected by using well-known equipment and methods in the art, for example, it can be detected by using thermogravimetric analysis test TGA according to JYT014-1996. Specifically, according to the mass loss of the pole piece during the heating process, a mass-temperature curve, i.e., a TG curve, is drawn. The corresponding weight loss mass is read according to the polymer decomposition temperature, which is the total mass of the polymer in the pole piece, and the mass content and coating weight of the polymer are calculated accordingly. During the test, the following temperature rise program can be used for detection in a nitrogen atmosphere: 5°C / min, RT~500°C; 10°C / min, 500~600°C; 600°C constant temperature for 10min, end.

[0139] The positive electrode film layer includes a positive electrode active material, and the positive electrode active material can be a positive electrode active material known in the art for battery cells. As an example, the positive electrode active material contains a lithium positive electrode active material, for example, it can include at least one of the following materials: a lithium-containing phosphate compound and a layered structure positive electrode active material.

[0140] For example, the general formula of the olivine phosphate active material (lithium-containing phosphate compound) is: Li x A y Me a M b P 1-c X c Y z , wherein 0≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0141] For example, the layered positive electrode active material (layered positive electrode active materials such as ternary, lithium nickel oxide / sodium, lithium cobalt oxide / sodium, lithium manganese oxide / sodium, lithium-rich layered and rock salt phase layered materials). The general formula of the layered positive electrode active material is: Li x A y Ni a Co b Mn c M (1-a-b-c) Y z, wherein 0≤x≤2.1, 0≤y≤2.1, and 0.9≤x+y≤2.1; 0≤a≤1, 0≤b≤1, 0≤c≤1, and 0.1≤a+b+c≤1; 1.8≤z≤3.5; A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; Y includes one or more of O and F. Optionally, y=0. Specifically, the layered positive electrode active material may include lithium cobalt oxide LCO, lithium nickel oxide LNO, lithium manganese oxide LMO, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NML33), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 One or more of O2 (NCM811) and NCA.

[0142] The battery cell will be accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cell is different when it is discharged to different states. In the list of positive electrode active materials in the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles.

[0143] In the list of positive electrode active materials in the embodiments of the present application, the molar content of oxygen O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In reality, the molar content of oxygen O will fluctuate.

[0144] In the embodiments of the present application, the modified compound may be modified by doping or coating. The doping modification may be the addition of doping elements such as transition metals to the compound, and the coating modification may be the surface coating with materials such as carbon, that is, forming a carbon coating layer on the outer surface of the particle.

[0145] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the positive electrode active material is 80% to 99.9%, and optionally 90% to 99%. When the mass content of the positive electrode active material is within the above range, it is beneficial to improve the energy density of the battery cell.

[0146] In some embodiments, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer may be disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0147] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, an aluminum foil or an aluminum alloy foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include a combination of one or more selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, and the polymer material base layer may include a combination of one or more selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0148] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application embodiment has no particular restrictions on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes a combination of one or more selected from superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the positive electrode conductive agent is less than 5%.

[0149] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, a variety of fluorinated polymers, optional conductive agents, optional binders and any other components in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this. Of course, the preparation of the positive electrode sheet is not limited to the above method, and the preparation method mentioned above can also be used.

[0150] [Negative electrode]

[0151] In some embodiments, the electrode plate includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers.

[0152] The negative electrode active material may adopt the negative electrode active material for battery cells known in the art. As an example, the negative electrode active material may include but is not limited to at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material. The tin-based material may include at least one of elemental tin, tin oxide and tin alloy material.

[0153] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the negative electrode active material is 80% to 99.9%, and optionally 90% to 99%. When the mass content of the negative electrode active material is within the above range, it is beneficial to improve the energy density of the battery cell.

[0154] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the multiple fluorinated polymers is ≤5%; it can be optionally 0.05% to 5%. When the mass content of the multiple fluorinated polymers is within the above range, the multiple fluorinated polymers can effectively improve the interface performance and structural stability of the negative electrode plate. The mass content of the multiple fluorinated polymers refers to the sum of the mass content of each fluorinated polymer in the multiple fluorinated polymers.

[0155] Illustratively, the mass content of the various fluorinated polymers can be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1. 3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range consisting of any two of the above values.

[0156] When the negative electrode slurry adopts an aqueous solvent, in some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is greater than the mass content of the second fluorinated polymer; when multiple fluorinated polymers meet the above conditions, the interface performance and structural stability of the negative electrode plate can be further improved.

[0157] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is ≤4%; it can be optionally 0.5% to 4%, or optionally 2% to 4%. For example, the mass content of the first fluorinated polymer can be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%. , 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0% or a range consisting of any two of the above values.

[0158] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the second fluorinated polymer is ≤4%; it can be optionally 0.4% to 4%, further optionally 0.4% to 2%, and further optionally 0.4% to 1%. For example, the mass content of the first fluorinated polymer can be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0. .50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0% or a range consisting of any two of the above values.

[0159] In the case where the negative electrode slurry adopts an oily solvent such as, in some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is greater than the mass content of the second fluorinated polymer; when multiple fluorinated polymers meet the above conditions, the interface performance and structural stability of the negative electrode plate can be further improved.

[0160] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is ≤4%; optionally, it is 0.5% to 2%.

[0161] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the second fluorinated polymer is ≤4%; it can be optionally 0.4% to 4%, and further optionally 2% to 4%.

[0162] In some embodiments, the negative electrode current collector has two surfaces opposite to each other in the thickness direction thereof, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0163] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The embodiment of the present application has no particular restrictions on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the negative electrode conductive agent is ≤5%.

[0164] In some embodiments, the negative electrode film layer may further include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc. In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the other additives is ≤2%.

[0165] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0166] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, a variety of fluorinated polymers, optional conductive agents, optional binders, and other optional additives in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to this. Of course, the preparation of the negative electrode sheet is not limited to the above method, and the preparation method mentioned above can also be used.

[0167] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate of the present application also includes a protective layer covering the surface of the negative electrode film layer.

[0168] Battery Cell

[0169] In a second aspect, an embodiment of the present application provides a battery cell.

[0170] The battery cell includes an electrode plate as in any embodiment of the first aspect of the present application, which can effectively improve the cycle performance and storage performance of the battery cell.

[0171] [Isolation film]

[0172] In some embodiments, the battery cell includes a separator.

[0173] In some embodiments, the isolation film includes a substrate.

[0174] In some embodiments, a separator includes a substrate and a coating disposed on at least one surface of the substrate.

[0175] The embodiments of the present application have no particular restrictions on the material of the substrate, and any known substrate with good chemical stability and mechanical stability can be selected, such as at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The substrate can be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer can be the same or different.

[0176] In some embodiments, the coating layer may further include a heat-resistant filler. Further, the heat-resistant filler may include at least one of inorganic particles and organic particles.

[0177] In some embodiments, the decomposition temperature of the heat-resistant filler may be above 200° C., so that the heat-resistant filler may have the characteristics of good thermal stability and being difficult to decompose, thereby further improving the heat resistance of the isolation film.

[0178] The inorganic particles have the characteristics of high thermal stability and not easy to decompose. Optionally, the inorganic particles include at least one of inorganic particles with a dielectric constant of 5 or more, inorganic particles with ion conductivity but not storing ions, and inorganic particles capable of electrochemical reactions.

[0179] Optionally, inorganic particles having a dielectric constant of 5 or more include boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0<m<1, 0<n<1), Pb(Mg3Nb 2 / 3 )O3-PbTiO3 (abbreviated as PMN-PT), and at least one of their respective modified inorganic particles. Optionally, the modification method of each inorganic particle may be chemical modification and / or physical modification. Chemical modification methods include coupling agent modification (for example, using silane coupling agent, titanate coupling agent, etc.), surfactant modification, polymer grafting modification, etc. Physical modification methods may be mechanical force dispersion, ultrasonic dispersion, high energy treatment, etc. The modification treatment can reduce the agglomeration of inorganic particles, thereby enabling them to form a more stable and uniform spatial network structure with nanocellulose; in addition, by selecting coupling agents, surfactants or polymer-modified inorganic particles with specific functional groups, it is also helpful to improve the wetting properties of the coating to the electrolyte and improve the bonding strength between the coating and the substrate.

[0180] Optionally, inorganic particles having ion conductivity but not storing ions include Li3PO4, lithium titanium phosphate Li x1 Ti y1 (PO4)3, Lithium Aluminum Titanate Phosphate Li x2 Al y2 Ti z1 (PO4)3, (LiAlTiP) x3 O y3 Type glass, lanthanum lithium titanate Li x4 La y4 TiO3, Lithium Germanium Phosphate Thiophosphate x5 Ge y5 P z2 S w 、Lithium Nitride Li x6 N y6 、SiS2 glass Li x7 Si y7 S z3 and P2S5 glass Li x8 P y8 S z4At least one of 0<x1<2, 0<y1<3, 0<x2<2, 0<y2<1, 0<z1<3, 0<x3<4, 0<y3<13, 0<x4<2, 0<y4<3, 0<x5<4, 0<y5<1, 0<z2<1, 0<w<5, 0<x6<4, 0<y6<2, 0<x7<3, 0<y7<2, 0<z3<4, 0<x8<3, 0<y8<3, 0<z4<7. This can further improve the ion transport characteristics of the isolation membrane.

[0181] Organic particles have good thermal stability and are not easy to decompose, which can improve the heat resistance of the isolation membrane; at the same time, when the internal temperature of the battery cell reaches the melting point of the organic particles due to overcharge abuse, heat abuse, etc., the organic particles can also melt and be sucked into the micropores of the substrate due to capillary action to play a role in closing the pores and breaking the circuit, which is beneficial to ensure that the battery cell has high safety performance.

[0182] In some embodiments, the organic particles include, but are not limited to, at least one of polyethylene particles, polypropylene particles, polystyrene particles, melamine resin particles, phenolic resin particles, polyester particles (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, polyaryletherketone particles, and copolymers of butyl acrylate and ethyl methacrylate (e.g., cross-linked polymers of butyl acrylate and ethyl methacrylate).

[0183] In some embodiments, the coating further comprises a binder. The present application has no particular restrictions on the type of the binder, and any known material with good bonding properties can be selected. As an example, the binder comprises at least one of an aqueous solution type acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, sodium acrylate monomers or a copolymer with other comonomers), polyvinyl alcohol, isobutylene-maleic anhydride copolymer, and polyacrylamide.

[0184] Optionally, the content of binder in the coating is <30%, based on the mass of the coating.

[0185] [Electrolyte]

[0186] In some embodiments, the battery cells include an electrolyte.

[0187] During the charge and discharge process of the battery cell, active ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays a role in conducting active ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to actual needs.

[0188] The electrolyte includes electrolyte salt and solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual needs.

[0189] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0190] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0191] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature power performance.

[0192] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process and / or a lamination process.

[0193] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0194] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0195] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0196] In some embodiments, Figure 1 and Figure 2 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 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 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0197] The preparation method of the battery cell of the present application is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and the battery cell is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0198] In some embodiments of the present application, the battery cells according to the present application can be assembled into a battery module. The number of battery cells contained in the battery module can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module.

[0199] Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0200] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0201] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0202] Both the battery module 4 and the battery pack can be used as specific examples of batteries in the embodiments of the present application.

[0203] Figure 4 and Figure 5FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0204] Electrical devices

[0205] In a third aspect, the present application provides an electrical device, which includes at least one of the battery cell, battery module and battery pack of the present application. The battery cell, battery module and battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc. In some embodiments, the battery cell includes an injection hole, which is used to inject an electrolyte; when the battery cell is applied to the electrical device, the injection hole is located at the bottom of the battery cell in the vertical direction. Since the amount of free electrolyte in the battery cell is very small, or even no free electrolyte, when the injection hole is set at the bottom of the battery cell in the vertical direction, the reliability of the battery cell can also be improved, thereby improving the reliability of the electrical device.

[0206] The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements. Figure 6 Schematic diagram of an electric device as an example. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack 1 or a battery module can be used. As another example, the electric device can be a mobile phone, a tablet computer, a laptop computer, etc. The electric device is usually required to be light and thin, and a battery cell can be used as a power source.

[0207] Example

[0208] 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.

[0209] Example 1 Preparation of lithium ion battery

[0210] (1) Preparation of positive electrode sheet:

[0211] A variety of fluorinated polymers, positive electrode active material lithium iron phosphate LiFePO4, and conductive agent carbon black were added to N-methylpyrrolidone (NMP) at a mass ratio of 2.2:96.8:1 to mix and prepare positive electrode slurry. The positive electrode slurry was coated on the current collector aluminum foil and dried at 85°C and then cold pressed. After trimming, cutting, and striping, it was dried at 85°C under vacuum conditions for 4 hours to prepare positive electrode sheets.

[0212] (2) Preparation of negative electrode sheet:

[0213] A variety of fluorinated polymers, artificial graphite as the negative electrode active material, and carbon black as the conductive agent are added to water in a weight ratio of 2.4:97.3:0.3 and mixed evenly to form a negative electrode slurry. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C, then cold pressed, trimmed, cut, and striped, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet.

[0214] (3) Preparation of electrolyte:

[0215] The electrolyte includes an organic solvent and a lithium salt. The organic solvent includes ethylene carbonate EC and ethyl methyl carbonate (EMC) (volume ratio 3:7). The lithium salt includes 1 mol / L LiPF6.

[0216] (4) Preparation of lithium-ion batteries:

[0217] Using polyethylene film (PE) as a separator, the positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer packaging shell, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0218] Example 2 to Example 6

[0219] A lithium-ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the types of fluorinated polymers were adjusted in Examples 2 to 6.

[0220] Example 7 to Example 9

[0221] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the amount of the fluorinated polymer used was adjusted in Examples 7 to 10.

[0222] Example 10

[0223] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that the preparation method of the negative electrode sheet of Example 10 is as follows:

[0224] Oily anode: Add various fluorinated polymers, artificial graphite as the negative electrode active material, and carbon black as the conductive agent in a weight ratio of 2.4:97.3:0.3 to N-methylpyrrolidone (NMP) and mix them evenly to make negative electrode slurry. Coat the negative electrode slurry on the current collector copper foil and dry it at 85°C, then cold press, trim, cut, and strip, and dry it at 120°C under vacuum conditions for 12 hours to make negative electrode sheets.

[0225] Comparative Example 1

[0226] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that multiple fluorinated polymers were not used in Comparative Example 1.

[0227] (1) Preparation of positive electrode sheet:

[0228] The positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in a mass ratio of 97.5:0.7:1.8 and mixed to form a positive electrode slurry. The positive electrode slurry was coated on the current collector aluminum foil and dried at 85°C and then cold pressed. After trimming, cutting, and striping, it was dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) was 48%.

[0229] (2) Preparation of negative electrode sheet:

[0230] Aqueous anode: Add binder polyvinylidene fluoride, negative electrode active material artificial graphite, binder styrene butadiene rubber, and conductive agent carbon black into water at a weight ratio of 0.4:97.3:2:0.3 and mix evenly to make negative electrode slurry. Coat the negative electrode slurry on the current collector copper foil and dry it at 85°C, then cold press, trim, cut, and strip, and dry it at 120°C vacuum conditions for 12 hours to make negative electrode sheets. The crystallinity of the binder polyvinylidene fluoride (PVDF) is 48%.

[0231] Comparative Example 2

[0232] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the type of polymer was adjusted in Comparative Example 2.

[0233] Comparative Example 3

[0234] A lithium-ion battery was prepared by a method similar to that of Comparative Example 1. The difference from Comparative Example 1 is that the preparation method of the negative electrode sheet of Comparative Example 3 is as follows:

[0235] Oily anode: Add the binder polyvinylidene fluoride, the negative electrode active material artificial graphite, and the conductive agent carbon black to N-methylpyrrolidone (NMP) in a weight ratio of 2:97.3:0.7 and mix evenly to make a negative electrode slurry. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C, then cold pressed, trimmed, cut, and striped, and dried at 120°C vacuum conditions for 12 hours to make a negative electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) is 48%.

[0236] Test Section

[0237] 1. Lithium-ion battery capacity retention test

[0238] The lithium-ion batteries prepared in the examples and comparative examples are charged to 3.8V at a constant current of 1 / 3C at room temperature, left for 5 minutes, and then discharged to 2.0V at 1 / 3C. The obtained capacity is recorded as the initial capacity C0. Then transfer to a 60°C environment for storage. Repeat the above steps for the same battery, and record the discharge capacity Cn of the battery every 30D at the same time. Then, after every 30D, the battery capacity retention rate Pn = Cn / C0*100%. The 6 point values ​​of P1, P2...P6 are used as the vertical coordinates, and the corresponding storage time is used as the horizontal coordinates to obtain a dot graph of the battery capacity retention rate and the number of storage days. The battery capacity retention rate data in Table 4 are the data measured after 180D of storage under the above test conditions, that is, the value of P6.

[0239] 2. Lithium-ion battery DC impedance test

[0240] The lithium-ion batteries prepared in the examples and comparative examples are charged to 3.8V at 1 / 3C constant current at 25°C, left for 5 minutes, and the voltage V1 is recorded. Then, they are discharged at 1 / 3C for 30 seconds, and the voltage V2 is recorded. The internal resistance DCR1 of the battery after the first cycle is obtained by (V2-V1) / 1 / 3C. Then, the battery is transferred to a 60°C environment for storage. Repeat the above steps for the same battery, and record the internal resistance DCRn (n=1, 2, 3...6) of the nth battery at the same time. The six point values ​​of DCR1, DCR2, DCR3...DCR6 are used as the vertical coordinates, and the corresponding number of cycles are used as the horizontal coordinates to obtain a curve of the storage days of the battery discharge DCIR.

[0241] In Table 4, the battery internal resistance increase ratio = (DCRn-DCR1) / DCR1*100%. The data in Table 4 are measured after storage for 180D under the above test conditions.

[0242] Test Results

[0243] The test results are shown in Tables 1 to 4.

[0244] Table 1

[0245]

[0246] Table 2

[0247]

[0248] Table 3

[0249] The first fluorinated polymer Second fluorinated polymer <![CDATA[X c2 -X c1 ]]> <![CDATA[(X c2 -X c1 ) / X c1 ]]> <![CDATA[T c2 -T c1 ]]> <![CDATA[(T c2 -T c1 ) / T c1 ]]> Polymer A1 Polymer B1 10 40％ 35 39％ Polymer A2 Polymer B2 20 100％ 50 63％ Polymer A3 Polymer B3 40 400％ 75 125％ Polymer A4 Polymer B1 15 75％ 85 213％ Polymer A5 Polymer B2 22 122％ 80 160％ Polymer A1 Polymer B3 25 100％ 45 50％ Comparative polymer A6 Comparative polymer B4 / / / /

[0250] Table 4

[0251]

[0252] It can be seen from Table 4 that the positive electrode and negative electrode sheets of Comparative Example 1 do not contain multiple fluorinated polymers. During the cycle of the lithium-ion battery, the electrode sheets may expand in volume, resulting in the destruction of the interface and the formation of a new interface. The formation of a new interface will lead to the continuous occurrence of interfacial side reactions, thereby deteriorating the cycle performance and storage performance of the battery cell.

[0253] Although polymers are added to the pole pieces in Comparative Examples 2 and 3, the polymers cannot effectively form in-situ gels on the surface of the active material, cannot effectively slow down the interfacial reaction, and their own high impedance will deteriorate the battery kinetic performance.

[0254] In the embodiment of the present application, a plurality of fluorinated polymers are added to at least one of the positive electrode plate and the negative electrode plate. The first fluorinated polymer can form an in-situ gel on the surface of the solid-phase active substance, that is, a stable solid-liquid interface is formed on the surface of the active substance, thereby reducing the risk of side reactions at the solid-liquid interface. However, the first fluorinated polymer is not conducive to the bonding between the active substances, resulting in poor structural stability of the electrode plate. The second fluorinated polymer can enhance the bonding force between the active substances and play a role in supporting the electrode plate, thereby improving the structural stability of the electrode plate, thereby improving the cycle performance and storage performance of the battery cell.

[0255] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions and modifications may be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrode plate, comprising a current collector and a film layer disposed on at least one side of the current collector, wherein the film layer comprises an active material and a plurality of fluorinated polymers, The crystallinity of one of the plurality of fluoropolymers is denoted as X. c1 %, and the cold crystallization temperature is recorded as T c1 ℃; The crystallinity of another fluoropolymer in the plurality of fluoropolymers is denoted as X. c2 %, and the cold crystallization temperature is recorded as T c2 ℃, in, The plurality of fluorinated polymers satisfy: 20%≤(X c2 -X c1 ) / X c1 <400%,30%≤(T c2 -T c1 ) / T c1 <250%.

2. The electrode plate according to claim 1, wherein: 40%≤(X c2 -X c1 ) / X c1 <400%; Optionally, X c2 -X c1 ≥10; further optionally, 10≤X c2 -X c1 ≤45.

3. The electrode plate according to claim 2, wherein: 0<X c1 ≤28; and / or 30≤X c2 ≤50.

4. The electrode sheet according to any one of claims 1 to 3, wherein: 35%≤(T c2 -T c1 ) / T c1 <250%; Optionally, T c2 -T c1 ≥25; further optionally, 25≤T c2 -T c1 ≤100.

5. The electrode plate according to claim 4, wherein: Further optionally, 35<T c1 ≤100; and / or 115≤T c2 ≤140.

6. The electrode sheet according to any one of claims 1 to 5, wherein: Each of the plurality of fluoropolymers independently comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII), In formula (AI) and formula (AII), R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom; In formula (AIII), R 15 Including single bonds, substituted or unsubstituted C1-C3 alkyl; p is a positive integer selected from 1 to 3; n is a positive integer selected from 1,000 to 30,000.

7. The electrode sheet according to any one of claims 1 to 6, wherein: The molecular weight of one of the plurality of fluoropolymers is W1 g / mol, The molecular weight of another fluoropolymer among the plurality of fluoropolymers is W2 g / mol, The plurality of fluorinated polymers satisfy: 0<W 1 / W2<1; Alternatively, 2.0×10 5 ≤W1≤1.0×10 6 ; 5.0×10 5 ≤W2≤1.2×10 6 。 8. The electrode sheet according to any one of claims 1 to 7, wherein: Based on the total mass of the film layer, the total mass content of the plurality of fluorinated polymers is ≤5%; optionally 0.05% to 5%; Optionally, Based on the total mass of the film layer, the mass content of the first fluorinated polymer is ≤4%; Optionally, Based on the total mass of the film layer, the mass content of the second fluorinated polymer is ≤4%.

9. A battery comprising the electrode sheet according to any one of claims 1 to 8.

10. The battery according to claim 9, wherein The electrode plate comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, a first fluorinated polymer and a second fluorinated polymer; Optionally, Based on the total mass of the positive electrode film layer, the mass content of the first fluorinated polymer and the total mass content of the second fluorinated polymer are 0.05% to 2.5%; Optionally, Based on the total mass of the positive electrode film layer, the mass content of the first fluorinated polymer is less than the mass content of the second fluorinated polymer; Further optionally, Based on the total mass of the positive electrode film layer, the mass content of the first fluorinated polymer is ≤2%; optionally 0.05% to 2%; optionally 0.05% to 1%; Further optionally, Based on the total mass of the positive electrode film layer, the mass content of the second fluorinated polymer is ≤2%; it can be optionally 1% to 2%; it can be optionally 1.2% to 2%.

11. The battery according to claim 9 or 10, wherein: The electrode plate comprises a negative electrode plate, the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprises a negative electrode active material, a first fluorinated polymer and a second fluorinated polymer; Optionally, Based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer and the total mass content of the second fluorinated polymer are 0.05% to 5%; Optionally, Based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is greater than the mass content of the second fluorinated polymer; or Based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is less than the mass content of the second fluorinated polymer Further optionally, Based on the total mass of the negative electrode film layer, the mass content of the first fluorinated polymer is ≤4%; optionally 0.5% to 4%; Optionally, Based on the total mass of the negative electrode film layer, the mass content of the second fluorinated polymer is ≤4%; it can be optionally 0.4% to 2%.

12. An electrical device comprising the battery according to any one of claims 9 to 11.

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