Electrode sheet, battery and electric device

Abstract

An electrode sheet, a battery and an electric device. The electrode sheet comprises a current collector and a film layer arranged on at least one side of the current collector, wherein the film layer comprises an active substance and multiple fluorinated polymers. The crystallinity of one of the multiple fluorinated polymers is denoted as Xc1%, and the cold crystallization temperature thereof is denoted as Tc1°C; the crystallinity of another fluorinated polymer of the multiple fluorinated polymers is denoted as Xc2%, and the cold crystallization temperature thereof is denoted as Tc2°C; and the multiple fluorinated polymers satisfy: 20%≤(Xc2-Xc1) / Xc1＜400%, and 30%≤(Tc2-Tc1) / Tc1＜250%.

Description

Electrode plates, batteries and electrical devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311460439.8, filed on November 3, 2023, entitled “Electrode Plate, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to an electrode plate, a battery and an electrical device. Background Art

[0004] 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 power tools, etc.

[0005] As battery applications become increasingly widespread, 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.

[0006] Summary of the Invention

[0007] 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.

[0008] In a first aspect, the present application proposes an electrode plate, which includes a current collector and a film layer disposed on at least one side of the current collector, wherein the film layer includes an active material and a plurality of fluorinated polymers.

[0009] The crystallinity of one of the fluoropolymers is denoted as X. c1 %, and the cold crystallization temperature is recorded as T c1 ℃;

[0010] The crystallinity of another fluoropolymer among the multiple fluoropolymers is denoted as X. c2 %, and the cold crystallization temperature is recorded as T c2 ℃,

[0011] 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%.

[0012] 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 fluoropolymer forming an in-situ gel on the surface of the active material particles and improving the solid-liquid interface performance; the first fluoropolymer and the second fluoropolymer have similar structures. Compared with the first fluoropolymer, the crystallinity X of the second fluoropolymer is c2 % is relatively large, the cold crystallization temperature T c2 ℃ is relatively high, and the energy required to release the intermolecular constraints is higher, which is more conducive to improving its own cohesive energy density, reducing swelling deformation, and enhancing the binding force between active substances; therefore, the embodiment of the present application can effectively improve the cycle performance and storage performance of battery cells through the mutual cooperation of multiple fluorinated polymers.

[0013] 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.

[0014] In some embodiments, 0<X c1 ≤28; and / or 30≤X c2 ≤50.

[0015] 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.

[0016] In some embodiments, further optionally, 35<T c1 ≤100; and / or 115≤T c2 ≤140.

[0017] In some embodiments, each fluoropolymer in the plurality of fluoropolymers independently comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII),

[0018] In formula (AI) and formula (AII), R 11 、R12 、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;

[0019] In formula (AIII), R 15 Including single bonds, substituted or unsubstituted C1-C3 alkyl;

[0020] p is a positive integer selected from 1 to 3;

[0021] n is a positive integer selected from 1,000 to 30,000.

[0022] 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,

[0023] A variety of fluorinated polymers meet the following requirements: 0<W 1 / W2<1; alternatively, 2.0×10 5 ≤W1≤1.0×10 6 ; 5.0×10 5 ≤W2≤1.2×10 6 The first fluoropolymer 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 fluoropolymer has a relatively high molecular weight and longer molecular segments, which increases the probability of contact and entanglement between molecular segments and increases the intermolecular force, which can enhance the binding force between active substances and significantly reduce the interaction with solvent molecules, making it easier to regulate their dispersion position; the use 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.

[0024] In some embodiments, the total mass content of the multiple fluoropolymers is ≤5% based on the total mass of the film layer; optionally, it is 0.05% to 5%; alternatively, the mass content of the first fluoropolymer is ≤4% based on the total mass of the film layer; alternatively, the mass content of the second fluoropolymer is ≤4% based on the total mass of the film layer. 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.

[0025] 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.

[0026] 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, a first fluorinated polymer, and a second fluorinated polymer.

[0027] 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%.

[0028] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the first fluoropolymer is less than the mass content of the second fluoropolymer.

[0029] 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%.

[0030] 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%.

[0031] 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.

[0032] 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%.

[0033] 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.

[0034] 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.

[0035] 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%.

[0036] 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%.

[0037] In a third aspect, the present application proposes an electrical device comprising a battery as described in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. 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 creative work.

[0039] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0040] FIG. 2 is an exploded schematic diagram of an embodiment of the battery cell of FIG. 1 .

[0041] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0042] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0043] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0044] FIG6 is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0045] The drawings are not necessarily drawn to scale.

[0046] The accompanying drawings are described as follows: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. battery cell; 51. housing; 52. electrode assembly; 53. cover plate; 6. electrical device. DETAILED DESCRIPTION

[0047] Below, the embodiments of the electrode plate, battery and electrical device of the present application are described in detail 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 description 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.

[0048] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the 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, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this 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.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0050] 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.

[0051] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating 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), indicating 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.

[0052] In the embodiments of the present application, the terms "plurality" and "multiple" refer to two or more.

[0053] 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, or 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, and the like. Additionally, the alkyl group may be optionally substituted. When substituted, the substituent includes a fluorine atom.

[0054] 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, or a C1 to C2 alkoxy group. In some embodiments, the alkoxy group can include a methoxy group, an ethoxy group, or a propoxy group. In addition, the alkoxy group can be optionally substituted.

[0055] The term "halogen atom" refers to a fluorine atom, a chlorine atom, a bromine atom or the like.

[0056] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

[0057] 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 at the same time allows active ions to pass freely to form a loop.

[0058] 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.

[0059] 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, forming a stable solid-liquid interface 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.

[0060] Next, the technical solution of this application is described in detail.

[0061] Electrode plate

[0062] In a first aspect, an embodiment of the present application proposes an electrode plate.

[0063] The electrode plate includes a current collector and a film layer provided on at least one side of the current collector. The film layer includes an active material and a plurality of fluoropolymers. The crystallinity of one of the fluoropolymers is denoted as X. c1 %, and the cold crystallization temperature is recorded as T c1 ℃, the crystallinity of another fluoropolymer among the multiple fluoropolymers is recorded as X c2 %, and the cold crystallization temperature is recorded as T c2 ℃, among which, 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%.

[0064] 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 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 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 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 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 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 includes a positive electrode active material and a plurality of fluorinated polymers, 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, the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers.

[0065] In this application, each fluoropolymer in the plurality of fluoropolymers is a polymer containing fluorine atoms. One fluoropolymer in the plurality of fluoropolymers is defined as a first fluoropolymer, and another fluoropolymer in 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 greater the number of fluoropolymers, the more effective it is to combine multiple fluoropolymers to improve the cycling and storage performance of battery cells.

[0066] The first fluoropolymer has good affinity with the electrolyte in the battery cell. When the first fluoropolymer comes into contact with the electrolyte, it can swell. The solvent in the electrolyte can quickly diffuse between the molecular chains of the first fluoropolymer and be wrapped by the molecular chains, forming an in-situ gel on the surface of the active material and adhering 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 reactions 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 when the active materials expand and contract in the late cycle, the binding force between the active materials is poor, which makes the structural stability of the electrode plate worse. In the embodiment of the present application, a second fluoropolymer is also included. The second fluoropolymer has good solvent resistance and a high cohesive energy density. It can slow down its own swelling and deformation, 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.

[0067] 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 fluoropolymer forming an in-situ gel on the surface of the active material particles and improving the solid-liquid interface performance; the first fluoropolymer and the second fluoropolymer have similar structures. Compared with the first fluoropolymer, the crystallinity X of the second fluoropolymer is c2 % is relatively large, the cold crystallization temperature T c2 ℃ is relatively high, and the energy required to release the intermolecular constraints is higher, which is more conducive to improving its own cohesive energy density, reducing swelling deformation, and enhancing the binding force between active substances; therefore, the embodiment of the present application can effectively improve the cycle performance and storage performance of battery cells through the mutual cooperation of multiple fluorinated polymers.

[0068] 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. The intermolecular force 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 ℃ lower than the initial temperature of 20℃ and then heated to the 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 heat absorption and heat release during the cooling process is the actual cold crystallization temperature T c ℃, calculate the peak area corresponding to each peak in the cooling curve to obtain 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.

[0069] 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.

[0070] In the embodiment 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%, 700%, 710%, 710%, 720%, 730%, 740%, 750%, 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.

[0071] In some embodiments, X c2 -X c1 ≥10; optionally, 10≤X c2 -X c1 ≤45. For example, X c2 -Xc1 The crystallinity difference between the second fluoropolymer and the first fluoropolymer may be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, or a range consisting of any two of the aforementioned 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 aforementioned values.

[0072] 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.

[0073] 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.

[0074] In the embodiment 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 It can 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 values.

[0075] In some embodiments, T c2 -T c1≥25; further optionally, 25≤T c2 -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.

[0076] 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 foregoing values.

[0077] 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 foregoing values.

[0078] In some embodiments, the first fluoropolymer has a glass transition temperature of T g1 ℃, -30≤T g1 ≤40. Illustratively, 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 foregoing values.

[0079] In some embodiments, the second fluoropolymer 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 foregoing values.

[0080] In some embodiments, each fluoropolymer in the plurality of fluoropolymers independently comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII).

[0081] 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.

[0082] 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. Specifically, the materials can be distinguished by different structural units and / or different degrees of polymerization.

[0083] The compound represented by formula (AI) is as follows:

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 a fluorine atom.

[0090] 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),

[0091] The compound represented by formula (AII) is as follows:

[0092] 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.

[0093] 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.

[0094] Optionally, R 11 、R 12 、R 13 and R 14Each 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.

[0095] 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.

[0096] 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.

[0097] 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 a fluorine atom.

[0098] 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),

[0099] The compound represented by formula (AIII) is as follows:

[0100] In formula (AIII), R 15 Includes single bonds, substituted or unsubstituted alkyl groups; when substituted, substituents include fluorine atoms.

[0101] 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.

[0102] Optionally, R 15 This includes single bonds, substituted or unsubstituted C1-C3 alkyl groups.

[0103] In some embodiments, p is a positive integer selected from 1 to 3, such as 1, 2 or 3.

[0104] In some embodiments, the degree of polymerization n of the fluorinated polymer is selected from a positive integer from 1000 to 30000, such as 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.

[0105] 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),

[0106] 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 (CYTOP for short).

[0107] Optionally, the fluorinated polymer includes one or more of polyperfluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propylene copolymer (FEP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE).

[0108] The fluoropolymer 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. Alternatively, the fluoropolymer 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.

[0109] In the embodiments of the present application, the polymer may also be obtained by copolymerizing the above-mentioned 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.). Such small amounts of monomers have relatively poor lyophilic properties, and copolymerizing the above-mentioned fluoropolymer monomers with such monomers can improve the swelling ratio and compression modulus of the fluoropolymer.

[0110] In some embodiments, the molecular weight of the fluorinated polymer is 2×10 5 g / mol to 1.5×10 6 g / mol.

[0111] 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.

[0112] In some embodiments, the molecular weight of the first fluoropolymer is W1 g / mol, the molecular weight of the second fluoropolymer is W2 g / mol, and the plurality of fluoropolymers satisfy: 0<W 1 / W2<1. The molecular weight of the first fluoropolymer 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 fluoropolymer is relatively high, the molecular chain segments are longer, the probability of contact and entanglement between the molecular segments 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 use of the two together is more conducive to improving the interface side reactions and structural stability in the positive electrode sheet, 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.

[0113] 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, 8×105 g / mol, 1.0×10 6 g / mol or a range consisting of any two of the above values.

[0114] 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.

[0115] The relevant parameters of the fluorinated polymer according to the embodiment of the present application can be detected by the following methods:

[0116] 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 using a Thermo Nicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR), and then tested in accordance with the standard GB / T6040-2002. The test range is: ATR method 600-4000 cm -1 ; Repeatability: ±2cm -1 ; Resolution: better than 4cm -1 ; Transmission depth 0.2~0.6μm.

[0117] 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 spectrometer at a test temperature of 20° C., TMS as an internal standard, CDCl 3 as a solvent, and a proton resonance frequency of 400 MHz.

[0118] The polymer monomer type of the fluorinated polymer according to the embodiment of the present application (especially suitable for monomers with a relatively small proportion in the polymer) can be tested by pyrolysis-gas chromatography-mass spectrometry. The specific testing steps are as follows: accurately weigh 0.5 mg of sample and place it in a sample cup. After fixing it to the injection rod, place it in a pyrolyzer installed near the GC (gas chromatography) injection port. After the pyrolyzer temperature reaches the set temperature, press the injection button, and the sample cup will fall rapidly 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, they are detected by a flame ionization detector FID or a mass spectrometer MS to obtain a gas chromatogram or a total ion current diagram.

[0119] The molecular weight of the fluoropolymer in the embodiment of the present application has a well-known meaning in the art and can be measured using commonly used equipment and methods in the art. It can be tested by gel permeation chromatography (GPC) in accordance with GB / T21863-2008. The specific testing steps are as follows: take an appropriate amount of the sample to be tested (the sample concentration is sufficient to ensure 8%-12% shading), add 20 ml of deionized water, and simultaneously ultraviolet (53KHz / 120W) for 5 minutes to ensure that the sample is completely dispersed, and then measure the sample in accordance with GB / T19077-2016 / ISO 13320:2009 standard.

[0120] [Positive electrode]

[0121] In some embodiments, the electrode plate includes a positive electrode plate, which 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 multiple 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 multiple 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.

[0122] In other embodiments, the electrode assembly includes a negative electrode sheet, the negative electrode sheet including 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 including a negative electrode active material and multiple fluorinated polymers. In this case, the positive electrode film layer may include only the positive electrode active material, i.e., not include the fluorinated polymer.

[0123] Further research 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.

[0124] In some embodiments, the total mass content of the multiple fluoropolymers is ≤5% based on the total mass of the positive electrode film layer; optionally, it is 0.05% to 3%; or optionally, it is 0.05% to 2.5%. When the mass content of the multiple fluoropolymers is within the above ranges, the multiple fluoropolymers can effectively improve the interfacial properties and structural stability of the positive electrode sheet. The mass content of the multiple fluoropolymers refers to the sum of the mass contents of each fluoropolymer in the multiple fluoropolymers.

[0125] 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%, 1.10%, 1.111%, 1.12%, 1.93%, 1.94%, 1.95%, 1.96%, 1.97%, 1.98%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 1.99%, 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.

[0126] 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.

[0127] In some embodiments, 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%, 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.

[0128] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the second fluorinated polymer is ≤2%; optionally 1% to 2%; 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.

[0129] In the embodiments of the present application, the mass content of the polymer has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, it can be detected using thermogravimetric analysis (TGA) according to JYT014-1996. Specifically, based on the mass loss of the electrode during the heating process, a mass-temperature curve, i.e., a TG curve, is plotted. The corresponding weight loss is read according to the polymer decomposition temperature, which is the total mass of the polymer in the electrode. The mass content of the polymer and the coating weight are calculated from this. During the test, the following temperature ramp program can be used in a nitrogen atmosphere for detection: 5°C / min, RT ~ 500°C; 10°C / min, 500 ~ 600°C; constant temperature at 600°C for 10 minutes, then end.

[0130] The positive electrode film layer includes a positive electrode active material. The positive electrode active material can be a positive electrode active material commonly known in the art for use in battery cells. For example, the positive electrode active material includes a lithium-containing positive electrode active material, such as at least one of the following materials: a lithium-containing phosphate compound and a layered positive electrode active material.

[0131] For example, the general formula of the olivine-type 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.

[0132] For example, the layered positive electrode active material (layered positive electrode active material such as ternary, lithium nickelate / sodium, lithium cobaltate / sodium, lithium manganate / sodium, lithium-rich layered and rock salt phase layered materials) is generally formulated as: 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 structure 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.

[0133] During the charge and discharge process, battery cells are accompanied by the deintercalation and deintercalation of active ions, such as Li, and their molar content varies when the battery cells are discharged to different states. The molar content of Li in the examples of positive electrode active materials in the embodiments of this application refers to the material's initial state, i.e., the state before the materials are added. When the positive electrode active material is used in a battery system, the molar content of Li may change after charge and discharge cycles.

[0134] In the examples of the positive electrode active materials in the embodiments of the present application, the molar content of oxygen O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate.

[0135] In the embodiment of the present application, the modified compound can be modified by doping or coating. Doping modification can be adding doping elements such as transition metals to the compound, and coating modification can be surface coating with materials such as carbon, that is, forming a carbon coating layer on the outer surface of the particle.

[0136] In some embodiments, the mass content of the positive electrode active material is 80% to 99.9%, or optionally 90% to 99%, based on the total mass of the positive electrode film layer. 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.

[0137] 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 either or both of the two opposite surfaces of the positive electrode current collector.

[0138] 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, 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. 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).

[0139] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application embodiment does not particularly limit the type of positive electrode conductive agent. For example, the positive electrode conductive agent may include 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, the mass percentage of the positive electrode conductive agent is less than 5% based on the total mass of the positive electrode film layer.

[0140] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is usually formed by dispersing the positive electrode active material, various 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.

[0141] [Negative electrode]

[0142] 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.

[0143] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. For 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. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0144] In some embodiments, the mass content of the negative electrode active material is 80% to 99.9%, or optionally 90% to 99%, based on the total mass of the negative electrode film layer. 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.

[0145] In some embodiments, the mass content of the multiple fluoropolymers is ≤5% based on the total mass of the negative electrode film layer; optionally, it is 0.05% to 5%. When the mass content of the multiple fluoropolymers is within the above range, the multiple fluoropolymers can effectively improve the interfacial properties and structural stability of the negative electrode sheet. The mass content of the multiple fluoropolymers refers to the sum of the mass contents of each fluoropolymer in the multiple fluoropolymers.

[0146] For example, the 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%, 1.5%, 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.

[0147] 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.

[0148] 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.

[0149] 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%, 0.4 %, 5%, 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.

[0150] 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.

[0151] 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%.

[0152] 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%.

[0153] In some embodiments, the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0154] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present embodiments do not particularly limit the type of negative electrode conductive agent. For 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, the mass percentage of the negative electrode conductive agent based on the total mass of the negative electrode film layer is ≤5%.

[0155] In some embodiments, the negative electrode film layer may optionally include other additives. For example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like. In some embodiments, the weight percentage of the other additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0156] 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, 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, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a 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).

[0157] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, various fluorinated polymers, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them evenly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. Of course, the preparation of the negative electrode sheet is not limited to the above method; the preparation methods described above can also be used.

[0158] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application further 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 further includes a protective layer covering the surface of the negative electrode film layer.

[0159] battery cells

[0160] In a second aspect, an embodiment of the present application provides a battery cell.

[0161] The battery cell includes the electrode pole piece according to any embodiment of the first aspect of the present application, which can effectively improve the cycle performance and storage performance of the battery cell.

[0162] [Isolation film]

[0163] In some embodiments, the battery cell includes a separator.

[0164] In some embodiments, the separator includes a substrate.

[0165] In some embodiments, a separator includes a substrate and a coating disposed on at least one surface of the substrate.

[0166] The embodiments of the present application are not particularly limited to the material of the substrate. Any known substrate with good chemical and mechanical stability may be selected, such as at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate may 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 may be the same or different.

[0167] 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.

[0168] In some embodiments, the decomposition temperature of the heat-resistant filler may be above 200° C., so that the heat-resistant filler may have good thermal stability and be difficult to decompose, thereby further improving the heat resistance of the isolation membrane.

[0169] The inorganic particles have the characteristics of high thermal stability and non-decomposability. Optionally, the inorganic particles include at least one of inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ion conductivity but not storing ions, and inorganic particles capable of undergoing electrochemical reactions.

[0170] Alternatively, the 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 coating's wetting properties for the electrolyte and improve the bonding strength between the coating and the substrate.

[0171] Alternatively, inorganic particles having ion conductivity but not storing ions include Li3PO4, lithium titanium phosphate Li x1 Ti y1 (PO4)3, lithium aluminum titanium 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 thiophosphate Li x5 Ge y5 P z2 S w , lithium nitride Li x6 N y6 、SiS2 type glass Li x7 Si y7 S z3 and P2S5 glass Li x8 P y8 S z4 At least one of the following: 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 properties of the isolation membrane.

[0172] 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 absorbed 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.

[0173] 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).

[0174] In some embodiments, the coating further comprises a binder. The present application does not particularly limit the type of binder; any known material with good adhesive properties may be used. For example, the binder comprises at least one of an aqueous solution-based acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, or sodium acrylate, or a copolymer with other comonomers), polyvinyl alcohol, an isobutylene-maleic anhydride copolymer, and polyacrylamide.

[0175] Optionally, the binder content in the coating is <30%, based on the mass of the coating.

[0176] [Electrolyte]

[0177] In some embodiments, the battery cells include an electrolyte.

[0178] During the charge and discharge process of a battery cell, active ions are embedded and released back and forth between the positive and negative electrodes, and the electrolyte conducts the active ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and it can be selected according to actual needs.

[0179] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0180] 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 bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0181] 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).

[0182] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or 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.

[0183] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0184] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0185] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell can also be a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0186] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square or any other shape. FIG1 shows a battery cell 5 of a square structure as an example.

[0187] In some embodiments, as shown in Figures 1 and 2, the outer packaging 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 membrane can be formed into 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 impregnated 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.

[0188] The manufacturing method of the battery cell of the present application is well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be wound or laminated to form an electrode assembly. The electrode assembly is then placed in an outer packaging, dried, and then injected with electrolyte. The battery cell is then vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell.

[0189] 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.

[0190] Figure 3 is a schematic diagram of an exemplary battery module 4. As shown in Figure 3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0191] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0192] 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.

[0193] Both the battery module 4 and the battery pack can be used as specific examples of batteries in the embodiments of the present application.

[0194] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0195] Electrical devices

[0196] On the third aspect, the present application provides an electrical device, which includes at least one of the battery cells, battery modules and battery packs of the present application. The battery cells, battery modules and battery packs can be used as power sources for the electrical device, and can also be used as energy storage units for the electrical device. The electrical device may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. In some embodiments, the battery cell includes an injection hole for injecting 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 extremely 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.

[0197] The electric device can select a battery cell, battery module or battery pack according to its usage requirements. Figure 6 is a 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 high power and high energy density requirements of the electric device, 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 usually requires to be lightweight and thin, and a battery cell can be used as a power source.

[0198] Example

[0199] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0200] Example 1 Preparation of lithium-ion battery

[0201] (1) Preparation of positive electrode sheet:

[0202] A positive electrode slurry is prepared by mixing various fluorinated polymers, lithium iron phosphate (LiFePO4), a positive electrode active material, and carbon black (a conductive agent) in a mass ratio of 2.2:96.8:1 in N-methylpyrrolidone (NMP). The slurry is then coated onto a current collector aluminum foil, dried at 85°C, and cold-pressed. The slurry is then trimmed, cut, and slit, and then dried at 85°C under vacuum for 4 hours to form the positive electrode sheet.

[0203] (2) Preparation of negative electrode sheet:

[0204] Anode slurry was prepared by adding various fluorinated polymers, artificial graphite (anode active material), and carbon black (conductive agent) to water at a weight ratio of 2.4:97.3:0.3 and mixing them evenly. The slurry was then coated onto a current collector copper foil and dried at 85°C. The slurry was then cold-pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours to form the cathode sheet.

[0205] (3) Preparation of electrolyte:

[0206] 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), and the lithium salt includes 1 mol / L LiPF6.

[0207] (4) Preparation of lithium-ion batteries:

[0208] 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 placed 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, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a lithium-ion battery is obtained.

[0209] Example 2 to Example 6

[0210] Lithium-ion batteries were prepared using a method similar to that of Example 1. Unlike Example 1, the types of fluorinated polymers were adjusted in Examples 2 to 6.

[0211] Example 7 to Example 9

[0212] A lithium-ion battery was prepared using 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.

[0213] Example 10

[0214] A lithium-ion battery was prepared using a method similar to that of Example 1. Unlike Example 1, the negative electrode sheet of Example 10 was prepared as follows:

[0215] Oily anode: Various fluorinated polymers, artificial graphite (the negative electrode active material), and carbon black (the conductive agent) are mixed uniformly in N-methylpyrrolidone (NMP) at a weight ratio of 2.4:97.3:0.3 to form a negative electrode slurry. The slurry is then coated onto a current collector copper foil and dried at 85°C. The slurry is then cold-pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours to form the negative electrode sheet.

[0216] Comparative Example 1

[0217] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that multiple fluorinated polymers were not used in Comparative Example 1.

[0218] (1) Preparation of positive electrode sheet:

[0219] The positive electrode slurry is prepared by mixing the positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 97.5:0.7:1.8 in N-methylpyrrolidone (NMP). The slurry is then coated onto a current collector aluminum foil, dried at 85°C, and cold-pressed. The slurry is then trimmed, cut, and slit, and then dried at 85°C under vacuum for 4 hours to form the positive electrode sheet. The binder polyvinylidene fluoride (PVDF) has a crystallinity of 48%.

[0220] (2) Preparation of negative electrode sheet:

[0221] Water-based anode: Add polyvinylidene fluoride (PVDF) as a binder, artificial graphite (anode active material), styrene-butadiene rubber (SBR) as a binder, and carbon black (conductive agent) in a weight ratio of 0.4:97.3:2:0.3 to water and mix thoroughly to create a negative electrode slurry. The slurry is then coated onto a current collector copper foil and dried at 85°C. The slurry is then cold-pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours to form the negative electrode sheet. The polyvinylidene fluoride (PVDF) binder has a crystallinity of 48%.

[0222] Comparative Example 2

[0223] A lithium-ion battery was prepared using 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.

[0224] Comparative Example 3

[0225] A lithium-ion battery was prepared using a method similar to that of Comparative Example 1. Unlike Comparative Example 1, the preparation method of the negative electrode sheet of Comparative Example 3 is as follows:

[0226] Oil-based anode: The binder polyvinylidene fluoride (PVDF), the negative electrode active material artificial graphite, and the conductive agent carbon black are mixed uniformly in N-methylpyrrolidone (NMP) at a weight ratio of 2:97.3:0.7 to form the negative electrode slurry. The slurry is coated on the current collector copper foil and dried at 85°C. The slurry is then cold-pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours to form the negative electrode sheet. The binder polyvinylidene fluoride (PVDF) has a crystallinity of 48%.

[0227] Test section

[0228] 1. Lithium-ion battery capacity retention test

[0229] The lithium-ion batteries prepared in the examples and comparative examples were 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 was recorded as the initial capacity C0. Then the batteries were transferred 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. The battery capacity retention rate after every 30D is 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.

[0230] 2. Lithium-ion battery DC impedance test

[0231] The lithium-ion batteries prepared in the examples and comparative examples were charged to 3.8V at a constant current of 1 / 3C at 25°C. After standing for 5 minutes, the voltage V1 was recorded. The batteries were then discharged at 1 / 3C for 30 seconds, and the voltage V2 was recorded. The internal resistance DCR1 of the battery after the first cycle was obtained by (V2-V1) / 1 / 3C. The batteries were then transferred to a 60°C environment for storage. The above steps were repeated for the same battery, and the internal resistance DCRn of the n-th battery (n=1, 2, 3...6) was recorded at the same time. The six point values ​​of DCR1, DCR2, DCR3...DCR6 were used as the vertical coordinates, and the corresponding number of cycles was used as the horizontal coordinates to obtain a curve chart of the storage days of the battery discharge DCIR.

[0232] 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.

[0233] Test results

[0234] The test results are shown in Tables 1 to 4.

[0235] Table 1

[0236] Table 2

[0237] Table 3

[0238] Table 4

[0239] As can be seen from Table 4, 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 the new interface will lead to the continuous occurrence of interfacial side reactions, thereby deteriorating the cycle performance and storage performance of the battery cell.

[0240] Although polymers were added to the electrodes in Comparative Examples 2 and 3, the polymers were unable to effectively form in-situ gels on the surface of the active material, could not effectively slow down the interfacial reaction, and their own high impedance would deteriorate the battery kinetics performance.

[0241] In the embodiment of the present application, multiple fluoropolymers are added to at least one of the positive electrode plate and the negative electrode plate. The first fluoropolymer can form an in-situ gel on the surface of the solid-phase active material, that is, a stable solid-liquid interface is formed on the surface of the active material, thereby reducing the risk of side reactions at the solid-liquid interface; however, the first fluoropolymer is not conducive to the bonding between the active materials, resulting in poor structural stability of the electrode plate. The second fluoropolymer can enhance the bonding force between the active materials, 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.

[0242] Although illustrative embodiments have been shown 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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