Electrode tab, battery, and electric device

Abstract

The application relates to an electrode tab, a battery and an electric device. The electrode tab comprises a current collector and a film layer arranged on at least one side of the current collector, the film layer comprising an active material and a plurality of fluorinated polymers, wherein the crystallinity of one of the plurality of fluorinated polymers is denoted as X c1 %, the cold crystallization temperature of the one of the plurality of fluorinated polymers is denoted as T c1 °C, the crystallinity of another of the plurality of fluorinated polymers is denoted as X c2 %, the cold crystallization temperature of the another of the plurality of fluorinated polymers is denoted as T c2 °C, wherein the plurality of fluorinated polymers satisfy: 20%≤(X c2 ‑X c1 ) / X c1 <400%, 30%≤(T c2 ‑T c1 ) / T c1 <250%.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrode tab, a battery and an electric device. BACKGROUND

[0002] The battery has the characteristics of high capacity and long service life, and is widely used in electronic devices such as mobile phones, notebook computers, electric vehicles, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes and electric tools.

[0003] With the increasingly wide range of applications of the battery, the requirements for the performance of the battery are gradually stringent. However, the cycle life and storage life of the battery are still poor, and need to be further improved. SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and aims to provide an electrode tab, a battery and an electric device.

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

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

[0007] The crystallinity of another of the plurality of fluorinated polymers is denoted as X c2 %, and the cold crystallization temperature is denoted as T c2 ℃,

[0008] Wherein, the plurality of fluorinated polymers satisfies: 20%≤(X c2 -X c1 ) / X c1 <400%, 30%≤(T c2 -T c1 ) / T c1 <250%.

[0009] Therefore, in the embodiments of the present application, the crystallinity X c1 % of the first fluorinated polymer is relatively small, the cold crystallization temperature T c1 ℃ is relatively low, and the flexibility of the molecular chain is stronger, which is more conducive to the formation of in-situ gel of the first fluorinated polymer on the surface of the active material particles, and improves the solid-liquid interface performance; the first fluorinated polymer and the second fluorinated polymer have similar structures, and compared with the first fluorinated polymer, the crystallinity X c2 % of the second fluorinated polymer is relatively large, and the cold crystallization temperature T c2The higher the relative Tg is, the higher the energy requirement for releasing the intermolecular binding is, which is more conducive to increasing the cohesive energy density of the fluorinated polymer, reducing the swelling deformation, and improving the binding force between the active substances. Thus, the embodiments of the present application can effectively improve the cycle performance and storage performance of the battery cell by the cooperation of the plurality of fluorinated polymers.

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

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

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

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

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

[0015]

[0016] In formula (AI) and formula (AII), R 11 , R 12 , R 13 and R 14 each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13and R 14 at least one of R

[0017]

[0018] in formula (AIII), R 15 including a single bond, a substituted or unsubstituted C1-C3 alkyl group;

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

[0020] n is a positive integer selected from 1000 to 30000.

[0021] In some embodiments, the molecular weight of one of the plurality of fluorinated polymers is W1 g / mol, the molecular weight of another of the plurality of fluorinated polymers is W2 g / mol,

[0022] The plurality of fluorinated polymers satisfies: 0 < W 1 / W2 < 1; optionally, 2.0 x 10 5 ≤ W1 ≤ 1.0 x 10 6 ; 5.0 x 10 5 ≤ W2 ≤ 1.2 x 10 6 The first fluorinated polymer has a relatively small molecular weight and a stronger affinity for the solvent, but is at a higher risk of being dispersed by the solvent, which is not conducive to regulating its position distribution; the second fluorinated polymer has a relatively high molecular weight and a longer molecular segment, the probability of contact and entanglement between the molecular segments is increased, the intermolecular force is increased, which can improve the binding force between the active substances, and the interaction with the solvent molecules is significantly reduced, which is easy to regulate its dispersion position; the use of both can better improve the interface side reaction and the structural stability in the positive electrode sheet, thereby improving the cycle performance and storage performance of the battery cell.

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

[0024] In a second aspect, the present application provides a battery comprising the electrode sheet of any one of the embodiments of the first aspect of the present application.

[0025] In some embodiments, the electrode tab comprises a positive electrode tab, the positive electrode tab comprising 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 comprising a positive electrode active material, a first fluorinated polymer, and a second fluorinated polymer.

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

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

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

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

[0030] In some embodiments, the electrode tab comprises a negative electrode tab, the negative electrode tab comprising 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 comprising a negative electrode active material, a first fluorinated polymer, and a second fluorinated polymer.

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

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

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

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

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

[0036] In a third aspect, the present application provides a power-using device comprising the battery according to the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below only some of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the drawings.

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

[0039] Figure 2 is a schematic diagram of an embodiment of a battery cell of the present application. Figure 1

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

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

[0042] Figure 5 is a schematic diagram of an embodiment of a battery pack of the present application. Figure 4

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

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

[0045] The reference signs are explained as follows:

[0046] 1, battery pack; 2, upper case; 3, lower case; 4, battery module;

[0047] 5, battery cell; 51, housing; 52, electrode assembly;

[0048] 53, cover plate;

[0049] 6, electric device.DETAILED DESCRIPTION

[0050] Hereinafter, embodiments of the electrode sheet, battery and electric device of the present application are specifically disclosed with appropriate reference to the drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0051] ​​The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, i.e., every range that falls within the larger range. For example, a range of "60% to 100%" or "60% to 90%" is also intended to include ranges of "60% to 85%", "65% to 90%", "77% to 81%", "60% to 70%", "70% to 80%", "65% to 90%", "60% to 80%", "65% to 70%", "70% to 90%", "60% to 65%", "70% to 75%", "85% to 90%", "65% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%", "70% to 90%", "60% to 70%", "70% to 80%", "60% to 90%", "60% to 80%,

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

[0053] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0054] Unless otherwise specified, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0055] In the embodiments of the present application, the term "a plurality of" or "a plurality of" refers to two or more.

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

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

[0058] The term "halogen atom" refers to a fluorine atom, a chlorine atom, a bromine atom, and the like.

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

[0060] The battery includes an electrode assembly and an electrolyte, the electrode assembly includes an electrode tab and a separator, the electrode tab includes a positive electrode tab and a negative electrode tab, the positive electrode tab includes a positive electrode film layer containing a positive electrode active material capable of providing active ions, the negative electrode tab includes a negative electrode film layer containing a negative electrode active material, and the separator is arranged between the positive electrode tab and the negative electrode tab, mainly to prevent the positive electrode tab and the negative electrode tab from short-circuiting, while allowing the active ions to pass freely to form a loop.

[0061] The electrode tab and the electrolyte have a solid-liquid contact interface, and during the cycle charging and discharging process of the battery, the electrode tab may expand in volume, causing the interface to be destroyed and a new interface to be formed, and the formation of the new interface will cause the continuous occurrence of interface side reactions, deteriorating the cycle performance and storage performance of the battery cell.

[0062] In view of the above problems, the embodiments of the present application improve the cycle performance and storage performance of the battery cell from the perspective of improving the interface performance of the solid-liquid contact interface. The embodiments of the present application propose an electrode tab, which includes a plurality of fluorinated polymers, at least two of which are different in material, one of which can form an in-situ gel on the surface of the solid-phase active material, i.e., a stable solid-liquid interface on the surface of the active material, reducing the risk of side reactions at the solid-liquid interface; but this kind of fluorinated polymer is not conducive to the combination of active materials, making the structural stability of the electrode tab poor, and the other fluorinated polymer in the plurality of fluorinated polymers can improve the bonding force between the active materials, supporting the electrode tab, thereby improving the structural stability of the electrode tab, thereby improving the cycle performance and storage performance of the battery cell.

[0063] Next, the technical solutions of the present application will be described in detail.

[0064] Electrode tab

[0065] In a first aspect, embodiments of the present application provide an electrode tab.

[0066] The electrode tab comprises a current collector and a film layer disposed on at least one side of the current collector, the film layer comprising an active material and a plurality of fluorinated polymers, wherein one of the plurality of fluorinated polymers has a crystallinity X c1 % and a cold crystallization temperature T c1 °C, and another of the plurality of fluorinated polymers has a crystallinity X c2 % and a cold crystallization temperature T c2 °C, wherein the plurality of fluorinated polymers satisfy: 20%≤(X c2 -X c1 ) / X c1 <400%, 30%≤(T c2 -T c1 ) / T c1 <250%.

[0067] The electrode tab can comprise at least one of a positive electrode tab and a negative electrode tab; for example, the electrode tab comprises a positive electrode tab, the positive electrode tab comprising 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 comprising a positive electrode active material and a plurality of fluorinated polymers. For another example, the electrode tab comprises a negative electrode tab, the negative electrode tab comprising 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 comprising a negative electrode active material and a plurality of fluorinated polymers. For yet another example, the electrode tab comprises a positive electrode tab and a negative electrode tab, the positive electrode tab comprising 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 comprising a positive electrode active material and a plurality of fluorinated polymers, the negative electrode tab comprising 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 comprising a negative electrode active material and a plurality of fluorinated polymers.

[0068] In the present application, each of the plurality of fluorinated polymers is a polymer comprising a fluorine atom. One of the plurality of fluorinated polymers is defined as a first fluorinated polymer, and another of the plurality of fluorinated polymers is defined as a second fluorinated polymer; when the plurality of fluorinated polymers further comprises a third fluorinated polymer, the third fluorinated polymer is defined as a third fluorinated polymer, and so on. The more the types of the plurality of fluorinated polymers, the better the cycle performance and storage performance of the battery cell can be improved by the cooperation of the plurality of fluorinated polymers.

[0069] The first fluorinated polymer has good affinity with the electrolyte in the battery cell. When the first fluorinated polymer comes into contact with the electrolyte, it swells. The solvent in the electrolyte can quickly diffuse into the molecular chains of the first fluorinated polymer and be encapsulated by the molecular chains, forming an in-situ gel on the surface of the active material. This gel adheres to the surface of the active material, providing protection and thus tightly bonding the active material and electrolyte, improving the solid-liquid interface performance and reducing side reactions between the active material and electrolyte. However, due to the poor solvent resistance of the first fluorinated polymer, it is not conducive to tightly bonding the active materials together, especially during the expansion and contraction of the active materials in the later stages of cycling. The weak bonding force between the active materials leads to poor structural stability of the electrode sheet. This application also includes a second fluorinated polymer. The second fluorinated polymer has better solvent resistance and a higher cohesive energy density, which can slow down its own swelling and deformation, improve the bonding force between the active materials, and thus improve the structural stability of the electrode sheet, enhancing the cycle performance and storage performance of the battery cell.

[0070] Crystallinity X of the first fluorinated polymer c1 The percentage is relatively small, and the cold crystallization temperature T c1 The relatively low temperature (℃) allows for greater flexibility of the molecular chains, which is more conducive to the formation of in-situ gels on the surface of active material particles by the primary fluorinated polymer, thus improving solid-liquid interface properties. The primary and secondary fluorinated polymers have similar structures, but the secondary fluorinated polymer exhibits higher crystallinity (X) compared to the primary fluorinated polymer. c2 The percentage is relatively large, and the cold crystallization temperature T c2 The higher the temperature, the higher the energy required to release the intermolecular bonds, which is more conducive to increasing its own cohesive energy density, reducing swelling and deformation, and enhancing the binding force between active materials. Therefore, the embodiments of this application can effectively improve the cycle performance and storage performance of battery cells through the synergy of various fluorinated polymers.

[0071] Crystallization refers to the process by which atoms, ions, or molecules in a material arrange themselves in a specific spatial order to form an ordered structure. The conformation of polymers during crystallization is determined by both intramolecular and intermolecular factors. Intermolecular forces affect the packing density between molecular chains. Crystallinity X C % is used to characterize the degree of crystallinity in a material, and the cold crystallization temperature T is used to characterize the degree of crystallinity in a material. c ℃ is the crystallization temperature of the material during the cooling process after melting. Both parameters can be measured using differential scanning calorimetry (DSC). Specifically, the testing procedure is as follows: Take 0.5g to 0.8g of sample, place the sample in a crucible, and subject the sample to heating and cooling treatments under a nitrogen atmosphere at a heating rate of 10℃ / min, starting from the intrinsic temperature of the material at ℃. g The initial temperature is 20°C lower than the material's intrinsic temperature. m20°C, and record the first heating curve; then decrease to a cut-off temperature of 20°C lower than the intrinsic T g c C The crystallinity in the embodiments of the present application refers to the crystallinity measured by differential scanning calorimetry.

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

[0073] In the embodiments 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 may 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%, 225%, 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 between any two of the above values.

[0074] In some embodiments, X c2 -X c1 ≥10; optionally, 10≤X c2 -X c1 ≤45. For example, X c2 -X​​c1 The difference between the crystallinity of the second fluoropolymer and the crystallinity of the first fluoropolymer can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range defined by 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 can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range defined by any two of the aforementioned values.

[0075] In some embodiments, 0 < X c1 ≤ 28. The first fluoropolymer can have a crystallinity of 5%, 10%, 15%, 20%, 25%, 28%, or a range defined by any two of the aforementioned values, as measured by differential scanning calorimetry. X c1 When the crystallinity is < 10%, the fluoropolymer can have substantially no melting peak, and the melting temperature can not be detectable.

[0076] In some embodiments, 30 ≤ X c2 ≤ 50. The second fluoropolymer can have a crystallinity of 30%, 35%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, or a range defined by any two of the aforementioned values, as measured by differential scanning calorimetry. X c2 When the crystallinity is < 10%, the fluoropolymer can have substantially no melting peak, and the melting temperature can not be detectable.

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

[0078] In some embodiments, T c2 - T c1 ≥ 25; further alternatively, 25 ≤ Tc2 T < 100; for example, T < 90; for example, T < 80; for example, T < 70; for example, T < 60; for example, T < 50; for example, T < 40; for example, T < 30; for example, T < 20; for example, T < 10; for example, T < 5; for example, T < 2; for example, T < 1. c1 T < 100; for example, T < 90; for example, T < 80; for example, T < 70; for example, T < 60; for example, T < 50; for example, T < 40; for example, T < 30; for example, T < 20; for example, T < 10; for example, T < 5; for example, T < 2; for example, T < 1. c2 T < 100; for example, T < 90; for example, T < 80; for example, T < 70; for example, T < 60; for example, T < 50; for example, T < 40; for example, T < 30; for example, T < 20; for example, T < 10; for example, T < 5; for example, T < 2; for example, T < 1. c1 The second fluoropolymer can have a cold crystallization temperature of 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or a range defined by any two of the foregoing values. In other words, the second fluoropolymer can have a cold crystallization temperature that 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 defined by any two of the foregoing values, less than the cold crystallization temperature of the first fluoropolymer.

[0079] In some embodiments, 35 < T < 100. c1 The first fluoropolymer can have a cold crystallization temperature of 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 defined by any two of the foregoing values.

[0080] In some embodiments, 115 < T < 140. c2 The second fluoropolymer can have a cold crystallization temperature of 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 defined by any two of the foregoing values.

[0081] In some embodiments, the first fluoropolymer has a glass transition temperature of T g1 °C, -30 < T g1 < 40. For example, the first fluoropolymer can have a glass transition temperature of -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 defined by any two of the foregoing values.

[0082] In some embodiments, the second fluoropolymer has a glass transition temperature of T g1 °C, -30 < T g1 < 40. For example, the second fluoropolymer can have a glass transition temperature of -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 defined by any two of the foregoing values.

[0083] In some embodiments, each of the plurality of fluorinated polymers independently comprises at least one of a compound represented by Formula (AI) to a compound represented by Formula (AIII).

[0084] When the plurality of fluorinated polymers comprises a first fluorinated polymer and a second fluorinated polymer, the first fluorinated polymer and the second fluorinated polymer each independently comprise at least one of a compound represented by Formula (AI) to a compound represented by Formula (AIII), and the first fluorinated polymer and the second fluorinated polymer are different in material, which can be distinguished by different structural units and / or different degrees of polymerization.

[0085] When the plurality of fluorinated polymers comprises a first fluorinated polymer, a second fluorinated polymer, and a third fluorinated polymer, the first fluorinated polymer and the second fluorinated polymer each independently comprise at least one of a compound represented by Formula (AI) to a compound represented by Formula (AIII), and the first fluorinated polymer and the second fluorinated polymer and the third fluorinated polymer are different in material in pairs, which can be distinguished by different structural units and / or different degrees of polymerization.

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

[0087]

[0088] In Formula (AI), R 11 , R 12 , R 13 , and R 14 each independently comprise a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and at least one of R 11 , R 12 , R 13 , and R 14 contains a fluorine atom.

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

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

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

[0092] In some embodiments, the degree of polymerization n of the fluorinated polymer is selected from positive integers 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 between any two of the aforementioned values.

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

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

[0095]

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

[0097]

[0098] In Formula (AII), R 11 , R 12 , R 13 , and R 14 each independently include 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 include at least one fluorine atom.

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

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

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

[0102] In some embodiments, the degree of polymerization n of the fluoropolymer is selected from positive integers 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 between any two of the aforementioned values.

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

[0104] In some embodiments, the fluoropolymer includes at least one of a compound represented by Formula (AII-1) to a compound represented by Formula (AII-5),

[0105]

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

[0107]

[0108] In Formula (AIII), R 15 includes a single bond, a substituted or unsubstituted alkyl group; when substituted, the substituent group includes a fluorine atom.

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

[0110] Optionally, R 15 comprises a single bond, substituted or unsubstituted C1-C3alkyl.

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

[0112] In some embodiments, the degree of polymerization n of the fluoropolymer 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 defined by any two of the aforementioned values.

[0113] In some embodiments, the fluoropolymer comprises at least one of a compound represented by Formula (AIII-1) to a compound represented by Formula (AIII-3),

[0114]

[0115] Exemplarily, the fluoropolymer comprises one or more of polytetrafluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroalkoxy polymer PFA, perfluoropolyether PFPE, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE, and perfluoro(1-butenyl vinyl ether) polymer (referred to as CYTOP).

[0116] Optionally, the fluoropolymer comprises one or more of polytetrafluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroalkoxy polymer PFA, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE.

[0117] The fluorinated polymer can be derived from one or more of the following monomers: fluorinated cycloethane, fluorinated ethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, and the like. Alternatively, the fluorinated polymer can be derived from at least two of the following monomers: fluorinated cycloethane, fluorinated ethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene.

[0118] In embodiments of the present application, the polymer can also be obtained by copolymerization of the above-mentioned structural groups with a small amount of other types of structural groups (e.g., olefinic compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid, and the like). The small amount of monomers has relatively poor lyophilicity, and copolymerization of the monomers of the fluorinated polymer with the small amount of monomers can improve the swelling rate and compression modulus of the fluorinated polymer.

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

[0120] For example, the fluorinated polymer can have a molecular weight of 2 x 10 5 g / mol, 5 x 10 5 g / mol, 8 x 10 5 g / mol, 1 x 10 6 g / mol, 1.2 x 10 6 g / mol, or a range defined by any two of the above values.

[0121] In some embodiments, the first fluorinated polymer has a molecular weight of W1 g / mol, the second fluorinated polymer has a molecular weight of W2 g / mol, and the plurality of fluorinated polymers satisfy: 0 < W 1 / W2 < 1. The first fluorinated polymer has a relatively small molecular weight and has a stronger affinity for the solvent, but has a higher risk of being dispersed by the solvent, which is not conducive to regulating the position distribution. The second fluorinated polymer has a relatively high molecular weight and a longer molecular chain segment, and the probability of contact and entanglement between the molecular chain segments is increased, the intermolecular force is increased, which can improve the binding force between the active substances, and the interaction with the solvent molecules is significantly reduced, which is easy to regulate the dispersion position. The combination of the two is more conducive to improving the interface side reaction and the 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 between any two of the foregoing.

[0122] In some embodiments, 2.0 x 10 5 ≤ W1≤ 1.0 x 10 6 For example, the first fluorinated polymer can have a molecular weight of 2 x 10 5 g / mol, 5 x 10 5 g / mol, 8 x 10 5 g / mol, 1.0 x 10 6 g / mol, or a range between any two of the foregoing.

[0123] In some embodiments, 5.0 x 10 5 ≤ W2≤ 1.5 x 10 6 For example, the second fluorinated polymer can have a molecular weight of 5 x 10 5 g / mol, 6 x 10 5 g / mol, 8 x 10 5 g / mol, 1 x 10 6 g / mol, 1.5 x 10 6 g / mol, or a range between any two of the foregoing.

[0124] The relevant parameters of the fluorinated polymer of the embodiments of the present application can be detected by the following methods:

[0125] The groups of the fluorinated polymer of the embodiments of the present application can be detected by infrared spectrophotometry IR. Specifically, the fluorinated polymer is tested by Thermo Nicolet Nexus 670 attenuated total reflection Fourier transform infrared spectrometer (FTIR-ATR), and then tested by referring to the standard GB / T 6040-2002, with a test range of 600-4000 cm -1 ; repeatability: ±2 cm -1 ; resolution: better than 4 cm -1 ; transmission depth 0.2-0.6 μm.

[0126] The structure of the fluorinated polymer of the embodiments 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 nuclear magnetic resonance instrument, with a test temperature of 20°C, TMS as an internal standard, CDCl3 as a solvent, and a proton resonance frequency of 400 MHz.

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

[0128] The molecular weight of the fluorinated polymer of the embodiments of the present application is the meaning known in the art, and can be measured by using the commonly used equipment and methods in the art. The gel permeation chromatography GPC can be used for testing according to GB / T21863-2008, and the specific testing steps are as follows: take an appropriate amount of the sample to be tested (the sample concentration is ensured to be 8%-12% obscuration), add 20 ml of deionized water, and simultaneously super 5 min (53 KHz / 120 W) to ensure that the sample is completely dispersed. Then, the sample is measured according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0129] [Positive electrode sheet]

[0130] In some embodiments, the electrode sheet includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material and a plurality of fluorinated polymers. In this case, the negative electrode sheet can include a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers. Alternatively, the negative electrode sheet can include a negative electrode current collector and a negative electrode film layer arranged 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 fluorinated polymers.

[0131] In other embodiments, the electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material and a plurality of fluorinated polymers. In this case, the positive electrode film layer can include a positive electrode active material, i.e., does not contain fluorinated polymers.

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

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

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

[0135] In some embodiments, the mass content of the first fluorinated polymer is less than the mass content of the second fluorinated polymer, based on the total mass of the positive electrode film layer. When the plurality of fluorinated polymers satisfy the above condition, the interface performance and structural stability of the positive electrode sheet can be further improved.

[0136] In some embodiments, the first fluorinated polymer has a mass content of ≤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%, 0.35%, 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 defined by any two of the aforementioned values, based on the total mass of the positive electrode film layer.

[0137] In some embodiments, the second fluorinated polymer has a mass content of ≤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 defined by any two of the aforementioned values, based on the total mass of the positive electrode film layer.

[0138] In the embodiments of the present application, the mass content of the polymer is in the meaning known in the art and can be detected by using the devices and methods known in the art, for example, it can be detected by using thermogravimetric analysis test TGA according to JYT014-1996, specifically, a mass-temperature curve, i.e. TG curve, is drawn according to the mass loss of the electrode during temperature rising, and the total mass of the polymer in the electrode is read according to the decomposition temperature of the polymer, thereby calculating the mass content of the polymer and the coating weight. During the test, the following temperature rising procedure can be used for detection in nitrogen atmosphere: 5℃ / min, RT-500℃; 10℃ / min, 500-600℃; 600℃ constant temperature for 10 min, end.

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

[0140] As an 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, Mg; Me includes one or more of Mn, Fe, Co, 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, Ce; X includes one or more of S, Si, Cl, B, C, N; Y includes one or more of O, F. Specifically, the olivine-type phosphate active material includes one or more of LiFeP04, LiMnP04, LiNiP04, and LiCoP04.

[0141] As an example, the layered structure positive electrode active material (layered structure positive electrode active material such as ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium-rich layered, and rock salt phase layered materials). The general formula of the layered structure positive electrode active material is: Li x A y Ni a Co b Mn c M (1-a-b-c) Y zwherein 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 comprises one or more of Na, K, Mg; M comprises 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, Ce; Y comprises one or more of O, F. Optionally, y=0. Specifically, the layered structure positive electrode active material can comprise one or more of lithium cobaltate LCO, lithium nickelate LNO, lithium manganate 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 O2(NCM811), and NCA.

[0142] The battery cell will be accompanied by deintercalation and consumption of active ions such as Li during charging and discharging, and the molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of Li is the initial state of the material, i.e., the state before feeding, and the positive electrode active material is applied to the battery system, and after charging and discharging cycles, the molar content of Li can change.

[0143] In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate.

[0144] In the embodiments of the present application, the modified compound can be modified by doping or coating. The doping modification can add a doping element such as a transition metal in the compound, and the coating modification can use carbon and other materials to perform surface coating, i.e., forming a carbon coating layer on the outer surface of the particle.

[0145] 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 in the above range, it is beneficial to improve the energy density of the battery cell.

[0146] In some embodiments, the positive electrode current collector has two surfaces opposite in the thickness direction of the positive electrode current collector, and the positive electrode film layer can be disposed on either or both of the two opposite surfaces of the positive electrode current collector.

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

[0148] In some embodiments, the positive electrode film layer can further optionally include a positive electrode conductive agent. The embodiments of the present application do not have a particular limitation on the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes a combination of one or more selected from the group consisting of super-p, 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 content of the positive electrode conductive agent is 5% or less based on the total mass of the positive electrode film layer.

[0149] The positive electrode film layer is generally formed by coating a positive electrode slurry on a positive electrode current collector, drying, and cold-pressing. The positive electrode slurry is generally formed by dispersing and uniformly stirring a positive electrode active material, a plurality of fluorinated polymers, an optional conductive agent, an optional binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto. Of course, the preparation of the positive electrode sheet is not limited to the above method, and the preparation method described above can also be used.

[0150] [Negative electrode sheet]

[0151] In some embodiments, the electrode sheet includes a negative electrode sheet, and 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 including a negative electrode active material and a plurality of fluorinated polymers.

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

[0153] In some embodiments, the mass content of the negative 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 active material is within the above range, the energy density of the battery cell can be improved.

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

[0155] For example, the mass content of the plurality of fluorinated polymers can be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, or a range between any two of the above values.

[0156] In some embodiments, the mass content of the first fluorinated polymer is greater than the mass content of the second fluorinated polymer, based on the total mass of the negative electrode film layer, when the negative electrode slurry uses an aqueous solvent. When the plurality of fluorinated polymers satisfy the above condition, the interface performance and structural stability of the negative electrode sheet can be further improved.

[0157] In some embodiments, the first fluorinated polymer has a mass content of ≤ 4%, optionally 0.5% to 4%, further optionally 2% to 4%, for example, the first fluorinated polymer has a mass content of 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 defined by any two of the above values.

[0158] In some embodiments, the second fluorinated polymer has a mass content of ≤ 4%, optionally 0.4% to 4%, further optionally 0.4% to 2%, further optionally 0.4% to 1%, for example, the first fluorinated polymer has a mass content of 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 defined by any two of the above values.

[0159] In some embodiments, the first fluorinated polymer has a mass content greater than the mass content of the second fluorinated polymer, based on the total mass of the negative electrode film layer, when the negative electrode slurry uses an oily solvent, such as NMP. When the plurality of fluorinated polymers satisfy the above conditions, the interface performance and structural stability of the negative electrode sheet can be further improved.

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

[0161] In some embodiments, the second fluorinated polymer has a mass content of ≤4%, optionally 0.4% to 4%, further optionally 2% to 4%, based on the total mass of the negative electrode film layer.

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

[0163] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in the embodiments of the present application. As an example, the negative electrode conductive agent can comprise at least one of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the negative electrode conductive agent is ≤5%, based on the total mass of the negative electrode film layer.

[0164] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents. As an example, the other auxiliary agents can comprise a thickening agent, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like. In some embodiments, the mass percentage content of the other auxiliary agents is ≤2%, based on the total mass of the negative electrode film layer.

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

[0166] The negative electrode film layer is usually prepared by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually prepared by dispersing a negative electrode active material, a plurality of fluorinated polymers, an optional conductive agent, an optional binder, and other optional auxiliary agents in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto. Of course, the preparation of the negative electrode sheet is not limited to the above method, and the preparation method described above can also be adopted.

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

[0168] Battery cell

[0169] In a second aspect, embodiments of the present application provide a battery cell.

[0170] The battery cell comprising the electrode sheet as any of the embodiments of the first aspect of the present application can effectively improve the cycle performance and storage performance of the battery cell.

[0171] [Separator]

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

[0173] In some embodiments, the separator comprises a substrate.

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

[0175] The material of the substrate is not particularly limited in the embodiments of the present application, and any known substrate having good chemical stability and mechanical stability can be selected, such as at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate can be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of the layers can be the same or different.

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

[0177] In some embodiments, the heat-resistant filler can have a decomposition temperature of 200°C or higher, whereby the heat-resistant filler can have the characteristics of good thermal stability and not easy to decompose, and thus the heat resistance of the separator can be further improved.

[0178] The inorganic particles have the characteristics of high thermal stability and not easy to decompose. Optionally, the inorganic particles comprise at least one of inorganic particles having a dielectric constant of 5 or higher, inorganic particles having ionic conductivity but not storing ions, and inorganic particles capable of electrochemical reaction.

[0179] Optionally, inorganic particles with a dielectric constant of 5 or higher include boehmite, alumina, 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, hydropyrite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), and Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1), Pb (Mg3Nb) 2 / 3 The inorganic particles are selected from at least one of PbTiO3 (PMN-PT) and its modified inorganic particles. Optionally, the modification of each inorganic particle can be chemical and / or physical. Chemical modification methods include coupling agent modification (e.g., using silane coupling agents, titanate coupling agents, etc.), surfactant modification, polymer grafting modification, etc. Physical modification methods can include mechanical dispersion, ultrasonic dispersion, high-energy treatment, etc. Modification treatment can reduce the agglomeration of inorganic particles, thereby enabling them to form a more stable and uniform spatial network structure with nanocellulose. Furthermore, by selecting coupling agents, surfactants, or polymers with specific functional groups to modify the inorganic particles, it is also helpful to improve the coating's wetting properties to the electrolyte and enhance the adhesion strength between the coating and the substrate.

[0180] Optionally, inorganic particles that are ion-conductive but do not store ions include Li3PO4 and 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, lithium lanthanum 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 type glass Li x8 P y8 S z4at least one of 0 < x1 < 2, 0 < y1 < 3, 0 < x2 < 2, 0 < y2 < 1, 0 < z1 < 3, 0 < x3 < 4, 0 < y3 < 13, 0 < x4 < 2, 0 < y4 < 3, 0 < x5 < 4, 0 < y5 < 1, 0 < z2 < 1, 0 < w < 5, 0 < x6 < 4, 0 < y6 < 2, 0 < x7 < 3, 0 < y7 < 2, 0 < z3 < 4, 0 < x8 < 3, 0 < y8 < 3, and 0 < z4 < 7. In this way, the ion transport properties of the separator film can be further improved.

[0181] The organic particles have good thermal stability and are not prone to decomposition, thereby improving the heat resistance of the separator film. When the internal temperature of the battery cell reaches the melting point of the organic particles due to overcharge abuse, thermal abuse, or the like, the organic particles can melt and be absorbed into the micropores of the base material due to capillary action, thereby closing the pores and breaking the circuit, which is conducive to ensuring high safety performance of the battery cell.

[0182] In some embodiments, the organic particles include, but are not limited to, at least one of polyethylene particles, polypropylene particles, polystyrene particles, melamine resin particles, phenolic resin particles, polyester particles (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyimide particles, polyamide-imide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyether sulfone particles, polyether ether ketone particles, polyaryletherketone particles, and a copolymer of butyl acrylate and ethyl methacrylate (e.g., a cross-linked polymer of butyl acrylate and ethyl methacrylate).

[0183] In some embodiments, the coating further includes a binder. The type of binder is not particularly limited in the present application, and any known material having good adhesion can be used. As an example, the binder includes at least one of an aqueous solution type acrylic resin (e.g., acrylic acid, methacrylic acid, sodium acrylate monomer homopolymer, or copolymer with other comonomers), polyvinyl alcohol, isobutylene-maleic anhydride copolymer, and polyacrylamide.

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

[0185] [Electrolyte]

[0186] In some embodiments, the battery cell includes an electrolyte.

[0187] During the charging and discharging of the battery cell, active ions are embedded and extracted between the positive and negative electrode sheets, and the electrolyte plays a role in conducting the active ions between the positive and negative electrode sheets. The type of electrolyte is not particularly limited in the present application and can be selected according to actual needs.

[0188] The electrolyte includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected as desired.

[0189] As an example, the electrolyte salt can include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bisoxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0190] As an example, the solvent can include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0191] In some embodiments, an additive can be optionally included in the electrolyte. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and / or an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, etc.

[0192] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly through a roll-pressing process and / or a stacking process.

[0193] In some embodiments, the battery cell can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte described above.

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

[0195] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, Figure 1 is a square battery cell 5 as an example.

[0196] In some embodiments, as shown in Figure 1 and Figure 2 , the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with 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 separator film can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged 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 the needs.

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

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

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

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

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

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

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

[0204] Electric device

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

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

[0207] Embodiments

[0208] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not indicated in the embodiments, it is carried out according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by purchase.

[0209] Preparation of lithium ion battery

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

[0211] A plurality of fluorinated polymers, positive electrode active material lithium iron phosphate LiFePO4, and conductive agent carbon black were added into N-methyl pyrrolidone (NMP) in a mass ratio of 2.2:96.8:1 to be mixed to prepare a positive electrode slurry. The positive electrode slurry was coated on a current collector aluminum foil and dried at 85°C, followed by cold pressing, then edge cutting, sheet cutting, and striping, and dried at 85°C under vacuum for 4h to prepare the positive electrode sheet.

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

[0213] A plurality of fluorinated polymers, negative electrode active material artificial graphite, and conductive agent carbon black were added into water in a weight ratio of 2.4:97.3:0.3 to be mixed uniformly to prepare a negative electrode slurry. The negative electrode slurry was coated on a current collector copper foil and dried at 85°C, followed by cold pressing, edge cutting, sheet cutting, and striping, and dried at 120°C under vacuum for 12h to prepare the negative electrode sheet.

[0214] (3) Preparation of the electrolyte:

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

[0216] (4) Preparation of the lithium ion battery:

[0217] A polyethylene film (PE) was used as a separator film. The above positive electrode sheet, the separator film, and the negative electrode sheet were stacked in sequence with the separator film between the positive electrode sheet and the negative electrode sheet to play a role of separation, and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer packaging shell, dried, and then injected with the electrolyte. After vacuum packaging, standing, formation, shaping, and other processes, the lithium ion battery was obtained.

[0218] Examples 2 to 6

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

[0220] Examples 7 to 9

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

[0222] Example 10

[0223] A lithium ion battery was prepared by using a method similar to that of Example 1, except that the preparation method of the negative electrode sheet of Example 10 was as follows:

[0224] Oil-based anode: A plurality of fluorinated polymers, negative electrode active material artificial graphite, and conductive agent carbon black were added to N-methyl pyrrolidone (NMP) in a weight ratio of 2.4:97.3:0.3, mixed uniformly, and negative electrode slurry was prepared. The negative electrode slurry was coated on a current collector copper foil and dried at 85°C, then cold-pressed, edged, cut, and striped, and then dried at 120°C under vacuum for 12h to prepare a negative electrode sheet.

[0225] Comparative Example 1

[0226] A lithium ion battery was prepared by using a method similar to that of Example 1, except that a plurality of fluorinated polymers were not used in Comparative Example 1,

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

[0228] A positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were added to N-methyl pyrrolidone (NMP) in a mass ratio of 97.5:0.7:1.8, mixed to prepare positive electrode slurry. The positive electrode slurry was coated on a current collector aluminum foil and dried at 85°C, then cold-pressed, then edged, cut, and striped, and then dried at 85°C under vacuum for 4h to prepare a positive electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) was 48%.

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

[0230] Water-based anode: A binder polyvinylidene fluoride, negative electrode active material artificial graphite, binder styrene-butadiene rubber, and conductive agent carbon black were added to water in a weight ratio of 0.4:97.3:2:0.3, mixed uniformly, and negative electrode slurry was prepared. The negative electrode slurry was coated on a current collector copper foil and dried at 85°C, then cold-pressed, edged, cut, and striped, and then dried at 120°C under vacuum for 12h to prepare a negative electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) was 48%.

[0231] Comparative Example 2

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

[0233] Comparative Example 3

[0234] A lithium ion battery was prepared by using a method similar to that of Comparative Example 1, except that the preparation method of the negative electrode sheet of Comparative Example 3 was as follows:

[0235] Oil anode: The binder polyvinylidene fluoride, negative active material artificial graphite, and conductive agent carbon black were added into N-methyl pyrrolidone (NMP) in a weight ratio of 2:97.3:0.7, mixed uniformly, and negative electrode slurry was prepared. The negative electrode slurry was coated on a current collector copper foil and dried at 85°C, then cold-pressed, trimmed, cut, and striped, and dried at 120°C under vacuum for 12h to prepare a negative electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) was 48%.

[0236] Test section

[0237] 1. Capacity retention rate test of lithium ion battery

[0238] The above lithium ion batteries prepared in the examples and comparative examples were charged at 1 / 3C constant current to 3.8V in a normal temperature environment, left for 5min, then discharged at 1 / 3C to 2.0V, and the obtained capacity was recorded as initial capacity C0. Then the above step was repeated for the same battery, and the discharge capacity Cn of the battery every 30D was recorded, then the capacity retention rate Pn of the battery after every 30D was Pn=Cn / C0*100%, and the capacity retention rate P1, P2, …, P6 was taken as the vertical coordinate and the corresponding storage time was taken as the horizontal coordinate to obtain a point graph of the capacity retention rate of the battery and the storage days. The battery capacity retention rate data in Table 4 was measured after 180D of storage under the above test conditions, i.e. the value of P6.

[0239] 2. DC impedance test of lithium ion battery

[0240] The above lithium ion batteries prepared in the examples and comparative examples were charged at 1 / 3C constant current to 3.8V at 25°C, left for 5min, then recorded the voltage V1. Then discharged at 1 / 3C for 30s, recorded the voltage V2, then (V2-V1) / 1 / 3C, and the internal resistance DCR1 of the battery after the first cycle was obtained. Then the above step was repeated for the same battery, and the internal resistance DCRn (n=1, 2, 3, …, 6) of the battery at the nth cycle was recorded, and the above DCR1, DCR2, DCR3, …, DCR6 were taken as the vertical coordinate and the corresponding cycle number was taken as the horizontal coordinate to obtain a curve graph of the storage days of the battery discharge DCIR.

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

[0242] Test results

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

[0244] Table 1

[0245]

[0246] Table 2

[0247]

[0248] Table 3

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

[0250] Table 4

[0251]

[0252] As can be seen from Table 4, the positive electrode tab and the negative electrode tab of Comparative Example 1 are not added with multiple fluorinated polymers, and during the cycle of the lithium ion battery, the electrode tab can be expanded in volume, which can cause the interface to be destroyed and form a new interface, and the formation of the new interface can cause the continuous occurrence of the interface side reaction, which can deteriorate the cycle performance and storage performance of the battery cell.

[0253] Although Comparative Examples 2 and 3 add polymers to the electrode tab, the polymers cannot effectively form in-situ gel on the surface of the active material, cannot effectively slow down the interface reaction, and the high impedance of the polymers themselves can deteriorate the battery dynamics performance.

[0254] The embodiments of the present application add multiple fluorinated polymers to at least one of the positive electrode tab and the negative electrode tab, the first fluorinated polymer can form in-situ gel on the surface of the solid-phase active material, i.e., form a stable solid-liquid interface on the surface of the active material, which can reduce the risk of side reactions occurring at the solid-liquid interface; however, the first fluorinated polymer is not conducive to the bonding between the active materials, which can make the structural stability of the electrode tab poor, the second fluorinated polymer can improve the bonding force between the active materials, which can play a supporting role for the electrode tab, thereby improving the structural stability of the electrode tab, and thus improving the cycle performance and storage performance of the battery cell.

[0255] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the present application, and the embodiments can be changed, replaced and modified without departing from the spirit, principles and scope of the present application.

Claims

1. An electrode tab, comprising a current collector and a film layer disposed on at least one side of the current collector, the film layer comprising an active material and a plurality of fluorinated polymers, The crystallinity of one of the plurality of fluoropolymers is denoted as X c1 %, and the cold crystallization temperature is denoted as T c1 °C; The crystallinity of another one of the plurality of fluoropolymers is denoted as X c2 %, and the cold crystallization temperature is denoted as T c2 °C. wherein The plurality of fluoropolymers satisfy: 20% ≤ (X c2 - X c1 ) / X c1 < 400%, 30% ≤ (T c2 - T c1 ) / T c1 < 250%, a molecular weight of one of the plurality of fluorinated polymers is W1 g / mol, a molecular weight of another of the plurality of fluorinated polymers is W2 g / mol, The plurality of fluoropolymers satisfies: 0 < W 1 / W2 < 1; 2.0×10 5 ≤W1≤1.0×10 6 ； 5.0×10 5 ≤W2≤1.2×10 6 。 2. The electrode panel of claim 1, wherein, 40% < (X c2 - X c1 ) / X c1 < 400%.

3. The electrode panel of claim 2, wherein, X c2 X c1 ≥10.

4. The electrode panel of claim 3, wherein, 10≤X c2 - X c1 ≤ 45.

5. The electrode patch of claim 2, wherein, 0 < X c1 ≤ 28; and / or 30 ≤ X c2 ≤ 50.

6. The electrode panel of any one of claims 1 to 3, wherein, 35% < (T c2 - T c1 ) / T c1 < 250%.

7. The electrode panel of claim 6, wherein, T c2 -T c1 ≥25.

8. The electrode panel of claim 7, wherein, 25≤T c2 -T c1 ≤100.

9. The electrode patch of claim 6, wherein, 35 < T c1 ≤ 100; and / or 115 ≤ T c2 ≤ 140.

10. The electrode patch of claim 1, wherein, each of the plurality of fluorinated polymers independently comprises at least one of a compound represented by Formula (AI) to a compound represented by Formula (AIII), Formula (AI), Formula (AII), In formula (AI) and formula (AII), R 11 , R 12 , R 13 , and R 14 each independently include 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 at least one of R 11 , R 12 , R 13 , and R 14 includes a fluorine atom; formula (AIII), In formula (AIII), R 15 including a single bond, substituted or unsubstituted C1-C3alkyl; p is a positive integer selected from 1 to 3; n is a positive integer selected from 1000 to 30000.

11. The electrode patch of claim 1, wherein, a total mass content of the plurality of fluorinated polymers is ≤ 5% based on a total mass of the film layer.

12. The electrode panel of claim 11, wherein, a total mass content of the plurality of fluorinated polymers is 0.05% to 5% based on a total mass of the film layer.

13. The electrode panel of claim 11, wherein, a mass content of the first fluorinated polymer is ≤ 4% based on a total mass of the film layer.

14. The electrode patch of claim 11, wherein, a mass content of the second fluorinated polymer is ≤ 4% based on a total mass of the film layer. 15.A battery comprising the electrode tab according to any one of claims 1 to 14.

16. The battery of claim 15, wherein, the electrode tab comprises a positive electrode tab, the positive electrode tab comprising 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 comprising a positive electrode active material, a first fluorinated polymer and a second fluorinated polymer.

17. The battery of claim 16, wherein, a mass content of the first fluorinated polymer and a total mass content of the second fluorinated polymer are 0.05% to 2.5% based on a total mass of the positive electrode film layer.

18. The battery of claim 16, wherein, a mass content of the first fluorinated polymer is less than a mass content of the second fluorinated polymer based on a total mass of the positive electrode film layer.

19. The battery of claim 18, wherein, a mass content of the first fluorinated polymer is ≤ 2% based on a total mass of the positive electrode film layer.

20. The battery of claim 19, wherein, a mass content of the first fluorinated polymer is 0.05% to 2% based on a total mass of the positive electrode film layer.

21. The battery of claim 20, wherein, a mass content of the first fluorinated polymer is 0.05% to 1% based on a total mass of the positive electrode film layer.

22. The battery of claim 18, wherein, a mass content of the second fluorinated polymer is ≤ 2% based on a total mass of the positive electrode film layer.

23. The battery of claim 22, wherein, a mass content of the second fluorinated polymer is 1% to 2% based on a total mass of the positive electrode film layer.

24. The battery of claim 23, wherein, a mass content of the second fluorinated polymer is 1.2% to 2% based on a total mass of the positive electrode film layer.

25. The battery of claim 15, wherein, the electrode tab comprises a negative electrode tab, the negative electrode tab comprising 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 comprising a negative electrode active material, a first fluorinated polymer and a second fluorinated polymer.

26. The battery of claim 25, wherein, a mass content of the first fluorinated polymer and a total mass content of the second fluorinated polymer are 0.05% to 5% based on a total mass of the negative electrode film layer.

27. The battery of claim 26, wherein, a mass content of the first fluorinated polymer is greater than a mass content of the second fluorinated polymer based on a total mass of the negative electrode film layer; or a mass content of the first fluorinated polymer is less than a mass content of the second fluorinated polymer based on a total mass of the negative electrode film layer.

28. The battery of claim 27, wherein, a mass content of the first fluorinated polymer is ≤ 4% based on a total mass of the negative electrode film layer.

29. The battery of claim 28, wherein, a mass content of the first fluorinated polymer of 0.5% to 4% based on the total mass of the negative electrode film layer.

30. The battery of claim 27, wherein, a mass content of the second fluorinated polymer of ≤ 4% based on the total mass of the negative electrode film layer.

31. The battery of claim 30, wherein, a mass content of the second fluorinated polymer of 0.4% to 2% based on the total mass of the negative electrode film layer.

32. An electrical device comprising the battery of any one of claims 15 to 31.

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