Positive pole piece, battery and electric device

Abstract

The invention relates to a positive pole piece, a battery and an electric device. The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one side of the positive current collector, the positive film layer comprises a positive active material and a lyophilic polymer, and the coating weight of the positive film layer is greater than or equal to 300mg / 1540.25 mm < 2 >.

Description

Technical Field

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

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

[0003] As the application range of batteries becomes wider and wider, the requirements for battery performance are becoming increasingly stringent. However, it is difficult for batteries to improve cycle performance, power performance and energy density at the same time, and further improvements are needed. Summary of the invention

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

[0005] In the first aspect, the embodiment of the present application proposes 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, the positive electrode film layer includes a positive electrode active material and a lyophilic polymer, and the coating weight of the positive electrode film layer is ≥300mg / 1540.25mm 2 .

[0006] Therefore, according to the embodiment of the present application, the coating weight of the positive electrode film layer is relatively high, and the energy density of the battery cell is high; however, due to the high coating weight and thick coating thickness, the polarization phenomenon at the positive electrode film layer is aggravated, and the path for lithium ions to be embedded in or out of the positive electrode active material of the positive electrode film layer is long, the internal resistance is large, and the power performance and cycle life are poor. In the embodiment of the present application, a lyophilic polymer is also added to the positive electrode film layer. The lyophilic polymer and the electrolyte have a high affinity, which can increase the infiltration rate of the electrolyte to the positive electrode film layer, improve the polarization phenomenon and the interface side reaction of the positive electrode film layer, thereby improving the cycle life. Since the lyophilic polymer is configured to coat the electrolyte on the surface of the positive electrode active material particles, an effective liquid storage point is formed on the surface of the positive electrode active material particles, thereby accelerating the migration rate of lithium ions, thereby improving the power performance of the battery cell. Therefore, the embodiment of the present application can take into account the improvement of cycle performance, power performance and energy density.

[0007] In some embodiments, the coating weight of the positive electrode film layer is 300 mg / 1540.25 mm 2 Up to 500mg / 1540.25mm 2 .

[0008] In some embodiments, the positive electrode active material includes a lithium-containing phosphate; optionally, based on the total mass of the positive electrode active material, the mass content of the lithium-containing phosphate is ≥ 90%; further optionally, the coating weight of the positive electrode film layer is ≥ 400 mg / 1540.25 mm 2 ; Optional: 400mg / 1540.25mm 2 Up to 500mg / 1540.25mm 2 Lithium-containing phosphate is the main material of positive electrode active material. The coating weight of the positive electrode film layer is relatively high, and the energy density of the battery cell is high. The combination of lithium-containing phosphate and lithium-containing phosphate can improve the cycle life and power performance.

[0009] In some embodiments, the lithium-containing phosphate includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified compounds of each thereof.

[0010] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide; optionally, based on the total mass of the positive electrode active material, the mass content of the lithium-containing transition metal oxide is ≥ 90%. Further optionally, the coating weight of the positive electrode film layer is ≥ 300 mg / 1540.25 mm 2 ; Optional: 300mg / 1540.25mm 2 Up to 500mg / 1540.25mm 2 Lithium-containing transition metal oxides are the main materials of positive electrode active materials. The coating weight of the positive electrode film layer is relatively high, and the energy density of the battery cell is high. The combination of lithium-containing transition metal oxides and lithium-containing phosphates can improve the cycle life and power performance.

[0011] In some embodiments, the lithium transition metal oxide includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0012] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the lyophilic polymer is ≤5%; alternatively, the mass content of the lyophilic polymer is ≤1%. When the mass content of the lyophilic polymer is within the above range, the lyophilic polymer is combined with the positive electrode active material with a high coating weight, and the lyophilic polymer can form multiple liquid storage sites on the surface of the positive electrode active material particles, thereby improving the liquid storage capacity of the positive electrode film layer and improving the wettability of the electrolyte to the positive electrode active material in the positive electrode film layer, thereby facilitating the improvement of the cycle performance and power performance of the battery cell.

[0013] In some embodiments, the positive electrode film layer includes multiple sub-layers, and the coating weight of the multiple sub-layers decreases step by step from the positive electrode current collector to the positive electrode film layer. The multiple sub-layers adopt a differentiated coating weight method, which is conducive to improving the polarization phenomenon of the positive electrode film layer and improving the cycle performance of the battery cell.

[0014] In some embodiments, the multilayer sublayer includes a first layer and a second layer, the first layer is disposed on the surface of the positive electrode collector, the second layer is located on the side of the first layer away from the positive electrode collector, and the coating weight of the first layer is greater than the coating weight of the second layer.

[0015] In some embodiments, the mass content of the lyophilic polymer in the first layer is greater than the mass content of the lyophilic polymer in the second layer. When the mass content of the lyophilic polymer is within the above range, the lyophilic polymer can form multiple liquid storage sites on the surface of each layer of the positive electrode active material particles, improve the liquid storage capacity of each layer, and improve the wettability of the electrolyte to the positive electrode active material in the positive electrode film layer, thereby facilitating the improvement of the cycle performance and power performance of the battery cell.

[0016] In some embodiments, the lyophilic polymer comprises a fluorinated polymer having a crystallinity Xc as measured by differential scanning calorimetry. 1 %,0<Xc 1 ≤28.

[0017] The melting temperature of fluorinated polymer is T m1 ℃, 0<T m1 ≤130;

[0018] Further optionally, the glass transition temperature of the fluorinated polymer is T g1 ℃, -30≤T g1 ≤40;

[0019] Further optionally, the fluorinated polymer comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII),

[0020]

[0021] In formula (AI) and formula (AII), R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom;

[0022]

[0023] In formula (AIII), R 15 Including single bonds, substituted or unsubstituted C1-C3 alkyl;

[0024] p is a positive integer selected from 1 to 3;

[0025] n is a positive integer selected from 1,000 to 30,000.

[0026] Therefore, the fluorinated polymer of the embodiment of the present application has a relatively low crystallinity, melting temperature or glass transition temperature. The fluorinated polymer has a certain activity above the glass transition temperature. Under the action of external force, it can buffer external energy through chain segment movement, which is manifested as a certain flexibility. It can improve the problem of increased brittleness of the positive electrode sheet caused by thick coating, and can serve as a buffer for the charging and discharging process of the positive electrode active material during the cycle of the positive electrode sheet, thereby improving the cycle expansion and improving the cycle performance.

[0027] In some embodiments, the lyophilic polymer includes an ether polymer, and the ether polymer is made into a sheet structure; the sheet structure is m2 The elastic modulus G'-energy loss modulus G" curve was obtained by dynamic frequency scanning test at +20)℃. The slope of the elastic modulus G'-energy loss modulus G" curve is K 1 , 1<K 1 <∞,T m2 ℃ represents the melting temperature of the ether polymer; alternatively, 1<K 1 ≤100; further optionally, 1<K 1 ≤10;

[0028] Optionally, the glass transition temperature of the ether polymer is T g2 ℃, -20≤T g2 ≤35;

[0029] Further optionally, the ether polymer includes at least one of the compound represented by formula (BI) and the compound represented by formula (BII),

[0030]

[0031] In formula (BI), R 21 and R 22 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R 23 Including substituted or unsubstituted C1-C5 alkylene;

[0032]

[0033] In formula (BII), R24 To R 27 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group or an ether group, and R 24 To R 27 At least one of them contains a substituted or unsubstituted C1-C3 alkoxy group or an ether group;

[0034] The polymerization degree n of the ether polymer is selected from a positive integer ranging from 1,500 to 25,000.

[0035] Therefore, when the ether polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether polymer still maintains a certain molecular chain entanglement state, which can effectively store the electrolyte and improve the cycle performance of the battery monomer.

[0036] In some embodiments, the lyophilic polymer comprises an ester polymer, and the ester polymer is made into a sheet-like structure; the sheet-like structure is m3 The elastic modulus G'-energy loss modulus G" curve was obtained by dynamic frequency scanning test at +20)℃. The slope of the elastic modulus G'-energy loss modulus G" curve is K 2 , 1<K 2 <∞,T m3 ℃ represents the melting temperature of the ester polymer; alternatively, 1<K 2 ≤100; further optionally, 1<K 2 ≤10;

[0037] Optionally, the glass transition temperature of the ester polymer is T g3 ℃, -20≤T g3 ≤35;

[0038] Further optionally, the ester polymer includes at least one of the compounds represented by formula (CI) to the compounds represented by formula (CIII),

[0039]

[0040] In formula (CI), R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R 34 Including substituted or unsubstituted C1-C8 alkyl, or substituted or unsubstituted C1-C8 hydroxyalkyl;

[0041]

[0042] In formula (CII), R 35including substituted or unsubstituted C2-C6 methylene; optionally, R 35 Each independently comprises a substituted or unsubstituted C2-C4 methylene group;

[0043]

[0044] In formula (CIII), R 36 , R 37 and R 38 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R 39 Including substituted or unsubstituted C1-C8 alkyl;

[0045] Optionally, R 36 , R 37 and R 38 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C4 alkyl group;

[0046] The polymerization degree n of the ester polymer is selected from a positive integer ranging from 800 to 20,000.

[0047] Therefore, when the ester polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether polymer still maintains a certain molecular chain entanglement state, which can effectively store the electrolyte and improve the cycle performance of the battery monomer.

[0048] In some embodiments, the lyophilic polymer includes an aldehyde-ketone polymer, and the aldehyde-ketone polymer is made into a sheet-like structure; the sheet-like structure is m4 The elastic modulus G'-energy loss modulus G" curve was obtained by dynamic frequency scanning test at +20)℃. The slope of the elastic modulus G'-energy loss modulus G" curve is K 3 , 0.8≤K 3 <∞,T m4 ℃ represents the melting temperature of aldehyde-ketone polymer; alternatively, 0.8≤K 3 ≤100; further optionally, 0.8≤K 3 ≤10;

[0049] Optionally, the glass transition temperature of the aldehyde-ketone polymer is T g4 ℃, -20≤T g4 ≤35;

[0050] Further optionally, the aldehyde-ketone polymer comprises at least one of the compound represented by formula (DI) and the compound represented by formula (DII),

[0051]

[0052] In formula (DI), R41 Including single bonds, substituted or unsubstituted C1-C6 methylene; R 42 Including hydrogen atom, substituted or unsubstituted C1-C6 alkyl;

[0053]

[0054] In formula (DII), R 43 To R 46 Each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group;

[0055] r and s are each independently selected from integers from 0 to 5, and at least one of r and s is selected from a positive integer;

[0056] The degree of polymerization n of the aldehyde-ketone polymer is selected from a positive integer of 500 to 15,000.

[0057] Therefore, when the aldehyde-ketone polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether polymer still maintains a certain molecular chain entanglement state, which can effectively store the electrolyte and improve the cycle performance of the battery monomer.

[0058] In some embodiments, the molecular weight of the lyophilic polymer is 2.0×10 5 g / mol to 1.2×10 6 g / mol.

[0059] In a second aspect, the present application proposes a battery, comprising a positive electrode plate as in any embodiment of the first aspect of the present application.

[0060] In a third aspect, the present application proposes an electrical device, comprising a battery as in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0062] Figure 1 It is a schematic diagram of one embodiment of the positive electrode plate of the present application.

[0063] Figure 2 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0064] Figure 3 yes Figure 2 An exploded schematic diagram of an embodiment of a battery cell.

[0065] Figure 4 It is a schematic diagram of an embodiment of a battery module of the present application.

[0066] Figure 5 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0067] Figure 6 yes Figure 5 An exploded schematic diagram of an embodiment of a battery pack is shown.

[0068] Figure 7 It is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0069] The drawings are not necessarily drawn to scale.

[0070] The following are the descriptions of the reference numerals:

[0071] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module;

[0072] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0073] 53. Cover plate;

[0074] 6. Electrical devices;

[0075] 7. Positive electrode plate; 71. Positive electrode current collector; 721. First layer; 722. Second layer. DETAILED DESCRIPTION

[0076] Below, the embodiments of the positive electrode plate, battery and electric device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0077] "Scope" disclosed in the present application is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The scope defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following range can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this document, and "0 to 5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0078] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0079] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0080] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0081] In the embodiments of the present application, the terms "plurality" and "multiple" refer to two or more.

[0082] The term "alkyl" encompasses both straight and branched chain alkyl groups. For example, the alkyl group may be a C1 to C5 alkyl group, a C1 to C4 alkyl group, a C1 to C3 alkyl group, a C1 to C2 alkyl group. In some embodiments, the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, etc. In addition, the alkyl group may be optionally substituted. When substituted, the substituent includes a fluorine atom.

[0083] The term "alkoxy" refers to a group in which an alkyl group is connected to an oxygen atom by a single bond. For example, the alkoxy group can be a C1 to C5 alkoxy group, a C1 to C3 alkoxy group, a C1 to C2 alkoxy group. In some embodiments, the alkoxy group can include a methoxy group, an ethoxy group, a propoxy group. In addition, the alkoxy group can be optionally substituted.

[0084] The term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom or the like.

[0085] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D) or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

[0086] The battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. The positive electrode sheet includes a positive electrode film layer containing a positive electrode active material, and the positive electrode active material can provide active ions. The negative electrode sheet includes a negative electrode film layer containing a negative electrode active material. The separator is arranged between the positive electrode sheet and the negative electrode sheet, and mainly plays a role in preventing the positive electrode sheet and the negative electrode sheet from short-circuiting, and at the same time allows the active ions to pass freely to form a loop. In order to increase the energy density of the battery, it can be achieved by increasing the coating weight of the positive electrode film layer.

[0087] However, as the coating weight increases, the polarization phenomenon at the positive electrode film layer intensifies, and the power performance and cycle life deteriorate significantly, making it difficult to improve the cycle performance, power performance and energy density at the same time.

[0088] In view of the above problems, the embodiment of the present application proposes a positive electrode sheet, which 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 coating weight of the positive electrode film layer is relatively high, for example, ≥300mg / 1540.25mm 2 , so as to improve the energy density of the battery cell; the positive electrode film layer also includes a lyophilic polymer, which has a high affinity for the electrolyte, can improve the affinity between the positive electrode plate and the electrolyte, and store the electrolyte on the surface of the active material particles of the positive electrode plate, thereby improving the liquid storage capacity of the positive electrode plate. The wetting performance of the electrolyte on the film layer is significantly improved, which can reduce the concentration polarization phenomenon. When the positive electrode plate is used in the battery, it can significantly improve the power performance and cycle life of the battery.

[0089] Next, the technical solution of this application is described in detail.

[0090] Positive electrode

[0091] In the first aspect, the embodiment of the present application proposes 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, the positive electrode film layer includes a positive electrode active material and a lyophilic polymer, and the coating weight of the positive electrode film layer is ≥300mg / 1540.25mm 2 .

[0092] The coating weight of the positive electrode film layer is relatively high, and the energy density of the battery cell is high; however, due to the high coating weight and thick coating thickness, the polarization phenomenon at the positive electrode film layer is aggravated, and the path for lithium ions to embed or escape from the positive electrode active material of the positive electrode film layer is long, the internal resistance is large, and the power performance and cycle life are poor. In the embodiment of the present application, a lyophilic polymer is also added to the positive electrode film layer. The lyophilic polymer and the electrolyte have a high affinity, which can increase the infiltration rate of the electrolyte to the positive electrode film layer, improve the polarization phenomenon and the interfacial side reactions of the positive electrode film layer, and thus improve the cycle life. Since the lyophilic polymer is configured to coat the electrolyte on the surface of the positive electrode active material particles, thereby forming an effective liquid storage point on the surface of the positive electrode active material particles, the migration rate of lithium ions can be accelerated, thereby improving the power performance of the battery cell.

[0093] Therefore, the embodiments of the present application can improve cycle performance, power performance and energy density.

[0094] In the embodiments of the present application, the coating weight of the positive electrode film layer has a well-known meaning in the art and can be tested using equipment and methods known in the art. For example, take a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the positive electrode film layer on one side can be wiped off first), punch it into a small disc with an area of ​​S1, weigh it, and record it as M1. Then wipe off the positive electrode film layer of the weighed positive electrode sheet, weigh the weight of the positive electrode collector, and record it as M0. The coating weight of the positive active material layer = (the weight of the positive electrode sheet M1-the weight of the positive electrode collector M0) / S1.

[0095] In the embodiment of the present application, the coating weight of the positive electrode film layer is relatively high, for example, ≥300 mg / 1540.25 mm 2 ; Optional: 300mg / 1540.25mm 2 Up to 500mg / 1540.25mm 2 The coating weight of the positive electrode film can be 300mg / 1540.25mm 2 、310mg / 1540.25mm 2 、320mg / 1540.25mm 2 、330mg / 1540.25mm 2 、340mg / 1540.25mm 2 、350mg / 1540.25mm2 、360mg / 1540.25mm 2 、370mg / 1540.25mm 2 、380mg / 1540.25mm 2 、390mg / 1540.25mm 2 , 400mg / 1540.25mm 2 、410mg / 1540.25mm 2 、420mg / 1540.25mm 2 、430mg / 1540.25mm 2 、440mg / 1540.25mm 2 , 450mg / 1540.25mm 2 、460mg / 1540.25mm 2 、470mg / 1540.25mm 2 、480mg / 1540.25mm 2 、490mg / 1540.25mm 2 、500mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0096] In some embodiments, the positive electrode active material may include but is not limited to at least one of lithium-containing phosphates and lithium-containing transition metal oxides and their respective modified compounds. The modified compound may be modified by doping or coating. The doping modification may be adding doping elements such as transition metals to the compound. The coating modification may be surface coating with materials such as carbon, that is, forming a carbon coating layer on the outer surface of the particle.

[0097] In an embodiment of the present application, based on the total mass of the positive electrode active material, when the mass content of the lithium-containing phosphate is ≥90%, the lithium-containing phosphate is used as the main material of the positive electrode active material, and the positive electrode active material is defined in this article as a lithium-containing phosphate system; in this case, the mass content of the lithium-containing phosphate can reach 100%.

[0098] Examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, lithium nickel phosphate, lithium cobalt phosphate, and their respective modified compounds.

[0099] In some embodiments, the lithium-containing phosphate comprises a molecular formula of L x A y Me a M b P 1-c X cY z Compounds and modified compounds thereof, wherein 0.5≤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; L includes one or more of Li and Na; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F. For example, lithium-containing phosphates include LiFePO 4 、LiMnPO 4 、LiFe 0.5 Mn 0.5 PO 4 、LiFe 0.6 Mn 0.4 PO 4 、LiFe 0.7 Mn 0.3 PO 4 、LiNiPO 4 and LiCoPO 4 One or more of .

[0100] In some embodiments, when the positive electrode active material is a lithium-containing phosphate system, the coating weight of the positive electrode film layer is ≥400 mg / 1540.25 mm 2 . Available as 400mg / 1540.25mm 2 Up to 500mg / 1540.25mm 2 .

[0101] When lithium-containing phosphate is used as the main material of the positive electrode active material, combined with a high coating weight, while improving the energy density of the battery cell, its cycle performance can also be significantly improved; and when the lithium-containing phosphate is used in combination with a lyophilic polymer, the lyophilic polymer can form liquid storage points on the surface of the lithium-containing phosphate material, effectively improving the wetting performance of the electrolyte on the lithium-containing phosphate material, thereby further improving the cycle performance and power performance of the battery cell.

[0102] In an embodiment of the present application, based on the total mass of the positive electrode active material, when the mass content of the lithium-containing transition metal oxide is ≥90%, the lithium-containing transition metal oxide is used as the main material of the positive electrode active material, and the positive electrode active material is defined in this article as a lithium-containing transition metal oxide system; in this case, the mass content of the lithium-containing transition metal oxide can reach 100%.

[0103] Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0104] In some embodiments, the lithium-containing transition metal oxide comprises a molecular formula of L x A y Ni a Co b Mn c M (1-a-b-c) Y z Compounds and modified compounds thereof, wherein 0.5≤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; L includes one or more of Li and Na; A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; and Y includes one or more of O and F. For example, lithium-containing transition metal oxides include LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O 2 At least one of .

[0105] The battery cell will be accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cell is different when it is discharged to different states. In the list of positive electrode active materials in the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles.

[0106] In the list of positive electrode active materials in the embodiments of the present application, the molar content of oxygen O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In reality, the molar content of oxygen O will fluctuate.

[0107] In some embodiments, when the positive electrode active material is a lithium-containing transition metal oxide system, the coating weight of the positive electrode film layer is ≥300 mg / 1540.25 mm 2 . Available as 300mg / 1540.25mm 2 Up to 400mg / 1540.25mm 2 .

[0108] When lithium-containing transition metal oxide is used as the main material of the positive electrode active material, it can improve the energy density of the battery cell with a high coating weight; when lithium-containing transition metal oxide and lyophilic polymer are used together, the lyophilic polymer can form liquid storage points on the surface of the lithium-containing transition metal oxide material, effectively improving the electrolyte's wetting performance on the lithium-containing transition metal oxide material, thereby further improving the cycle performance and power performance of the battery cell. The lyophilic polymer adheres to the surface of the lithium-containing transition metal oxide material, which can improve the structural stability of the lithium-containing transition metal oxide material to a certain extent, reduce the risk of structural collapse of the lithium-containing transition metal oxide, and further improve the cycle performance of the battery cell.

[0109] The positive electrode film layer is a layered structure, which can be a single-layer structure or a multi-layer structure. When the positive electrode film layer is a multi-layer structure, the positive electrode film layer can include multiple sub-layers, such as two sub-layers, three sub-layers, four sub-layers, five sub-layers, etc.; the type of positive electrode active material in each sub-layer of the multiple sub-layers can be the same or different; the mass content of the positive electrode active material in each sub-layer can be the same or different; the coating weight of each sub-layer can be the same or different.

[0110] In some embodiments, the coating weight of the multi-layer sub-layer decreases step by step in the direction from the positive electrode current collector to the positive electrode film layer, which can be understood as the coating weight of the sub-layer close to the positive electrode current collector is the largest, and the coating weight of the sub-layer farthest from the positive electrode current collector is the smallest. The step-by-step reduction can be linear or gradient reduction. For example, when the multi-layer sub-layer includes more than three sub-layers, the coating weight of the multi-layer sub-layer can satisfy a linear relationship or a gradient reduction relationship.

[0111] Multilayer sublayers can be arranged by multilayer coating, which helps to achieve thick coating; the multilayer sublayers adopt differentiated coating weights, especially the coating weight of the multilayer sublayers is gradually reduced, which can enable lithium ions to quickly migrate from the sublayer farthest from the positive electrode current collector to the sublayer closest to the positive electrode current collector, which is beneficial to improve the polarization phenomenon of the positive electrode film layer and enhance the cycle performance of the battery cell.

[0112] like Figure 1 As shown, exemplarily, the positive electrode sheet 7 includes a positive electrode current collector 71 and a positive electrode film layer disposed on both surfaces of the positive electrode current collector 71. The positive electrode film layer includes multiple sublayers, and the multiple sublayers include a first layer 721 and a second layer 722. The first layer 721 is disposed on the surface of the positive electrode current collector 71, and the second layer 722 is located on the side of the first layer 721 away from the positive electrode current collector 71. The coating weight of the first layer 721 is greater than the coating weight of the second layer 722; the first layer 721 and the second layer 722 are disposed in a double-layer coating form, which is helpful to achieve thick coating; the multi-layer sublayer adopts a differentiated coating weight method, and the coating weight of the first layer 721 is greater than the coating weight of the second layer 722, which is beneficial to improve the polarization phenomenon of the positive electrode film layer and enhance the cycle performance of the battery cell.

[0113] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the lyophilic polymer is greater than 0%, and the mass content of the lyophilic polymer is ≤5%; alternatively, the mass content of the lyophilic polymer is ≤1%. When the mass content of the lyophilic polymer is within the above range, the lyophilic polymer is combined with the positive electrode active material with a high coating weight, and the lyophilic polymer can form multiple liquid storage sites on the surface of the positive electrode active material particles, thereby improving the liquid storage capacity of the positive electrode film layer and improving the wettability of the electrolyte to the positive electrode active material in the positive electrode film layer, thereby facilitating the improvement of the cycle performance and power performance of the battery cell.

[0114] For example, the mass content of the lyophilic polymer may be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.6%, 1.7%, 1.8%, 1.9%, 1.10%, 1.20%, 1.31%, 1.32%, 1.33%, 1.34%, 1.35%, 1.36%, 1.37%, 1.38%, 1.39%, 1.40%, 1.41%, 1.42%, 1.43%, 1.44%, 1.45%, 1.46%, 1.47%, 1.48%, 1.49%, 1.50%, 1.51%, 1.52%, 1.53%, 1.54%, 1.55%, 1.56%, 1.57%, 1.58%, 1.59%, 1. %, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range consisting of any two of the above values.

[0115] In the embodiments of the present application, the mass content of the polymer has a well-known meaning in the art, and can be detected by using well-known equipment and methods in the art, for example, it can be detected by using thermogravimetric analysis test TGA according to JYT014-1996. Specifically, according to the mass loss of the pole piece during the heating process, a mass-temperature curve, i.e., a TG curve, is drawn. The corresponding weight loss mass is read according to the polymer decomposition temperature, which is the total mass of the polymer in the pole piece, and the mass content and coating weight of the polymer are calculated accordingly. During the test, the following temperature rise program can be used for detection in a nitrogen atmosphere: 5°C / min, RT~500°C; 10°C / min, 500~600°C; 600°C constant temperature for 10min, end.

[0116] When the positive electrode film layer includes multiple sublayers, the mass content of the lyophilic polymer in each sublayer is greater than 0%, and the mass content of the lyophilic polymer is ≤5%; it can be ≤1%; it can be further ≤0.5%. The mass content of the lyophilic polymer in the sublayer can increase accordingly with the increase of the coating weight of the sublayer. When the mass content of the lyophilic polymer is within the above range, the lyophilic polymer can form multiple liquid storage sites on the surface of the positive electrode active material particles in each layer, improve the liquid storage capacity of each layer, and improve the wettability of the electrolyte to the positive electrode active material in the positive electrode film layer, which is beneficial to improve the cycle performance and power performance of the battery cell.

[0117] Illustratively, the mass content of the lyophilic polymer in each sublayer can be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range consisting of any two of the above values.

[0118] In some embodiments, the lyophilic polymer may include at least one of a fluorinated polymer, an ether polymer, an ester polymer, and an aldehyde-ketone polymer. The lyophilic polymer is configured to coat the electrolyte on the surface of the active material, and can form an effective liquid storage point on the surface of the active material to improve the liquid storage capacity of the electrode plate. The specific types of lyophilic polymers are described below.

[0119] [Fluorinated polymers]

[0120] In some embodiments, the lyophilic polymer may include a fluorinated polymer.

[0121] In some embodiments, the fluorinated polymer has a crystallinity of X as measured by differential scanning calorimetry. c1 %,0<X c1 ≤28.

[0122] In some embodiments, the melting temperature of the fluorinated polymer is T m1 ℃, 0<T m1 ≤130.

[0123] In some embodiments, the glass transition temperature of the fluorinated polymer is T g1 ℃, -30≤T g1 ≤40.

[0124] Crystallization refers to the process in which atoms, ions or molecules in a material are arranged in a certain spatial order to form an orderly structure. The conformation of the lyophilic polymer in the crystallization is determined by both intramolecular and intermolecular factors. Intermolecular forces will affect the packing density between molecular chains. Crystallinity X C1 It is used to characterize the degree of crystallinity in the material. It can be measured by differential scanning calorimetry (DSC). Specifically, the test steps are as follows: take 0.5g to 0.8g of sample, place the sample in a carrier crucible, and heat and reduce the sample in a nitrogen atmosphere at a heating rate of 10℃ / min from the intrinsic T g1 The initial temperature is 20℃ lower than the material's intrinsic T m1 The cut-off temperature of the process is 20℃ higher than that of the material. The actual glass transition temperature T of the material is determined according to the endothermic and exothermic peak or transition point of the material in the process. g1 ℃ and melting temperature T m1 ℃, etc.

[0125] Therefore, the fluorinated polymer has a relatively low crystallinity, melting temperature or glass transition temperature. The fluorinated polymer has a certain activity above the glass transition temperature. Under the action of external force, it can buffer external energy through chain segment movement, which is manifested as a certain flexibility. It can improve the problem of increased brittleness of the positive electrode sheet caused by thick coating, and can serve as a buffer for the charging and discharging process of the positive electrode active material during the cycle of the positive electrode sheet, thereby improving the cycle expansion and improving the cycle performance.

[0126] For example, the crystallinity of the fluorinated polymer measured by differential scanning calorimetry may be 5%, 10%, 15%, 20%, 25%, 28% or a range consisting of any two of the above values.

[0127] For example, the melting temperature of the fluorinated polymer may be 10° C., 20° C., 50° C., 70° C., 90° C., 100° C., 120° C., 130° C., or a range consisting of any two of the foregoing values.

[0128] Illustratively, the glass transition temperature of the fluorinated polymer can be -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or a range consisting of any two of the above values.

[0129] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AI) to the compounds represented by formula (AII),

[0130]

[0131] In formula (AI) and formula (AII), R 11 , R 12 , R13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom.

[0132] Optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group.

[0133] Optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group.

[0134] Further optionally, R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group or a perfluoromethoxy group.

[0135] In some embodiments, the degree of polymerization n of the fluorinated polymer is selected from a positive integer from 1000 to 30000, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or a range consisting of any two of the above values.

[0136] Alternatively, when substituted, the substituent may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom. The halogen atom may include a fluorine atom, a bromine atom, and the like, and may be optionally a fluorine atom.

[0137] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AIII),

[0138]

[0139] In formula (AIII), R 15 Includes single bonds, substituted or unsubstituted alkyl groups; when substituted, substituents include fluorine atoms.

[0140] In some embodiments, when substituted, the substituent may include one or more of a nitrile group (—CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom.

[0141] Optionally, R 15 This includes single bonds, substituted or unsubstituted C1-C3 alkyl groups.

[0142] In some embodiments, p is selected from a positive integer of 1 to 3, such as 1, 2 or 3.

[0143] In some embodiments, the degree of polymerization n of the fluorinated polymer is selected from a positive integer from 1000 to 30000, for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, or a range consisting of any two of the above values.

[0144] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AI-1) to the compounds represented by formula (AI-11),

[0145]

[0146] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AII-1) to the compounds represented by formula (AII-5),

[0147]

[0148] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AIII-1) to the compounds represented by formula (AIII-3),

[0149]

[0150]

[0151] Exemplarily, the fluorinated polymer includes one or more of polyperfluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroethylene propylene copolymer FEP, perfluoroalkoxy polymer PFA, perfluoropolyether PFPE, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE and perfluoro(1-butenyl vinyl ether) polymer (abbreviated as CYTOP).

[0152] Optionally, the fluorinated polymer includes one or more of polyperfluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propylene (FEP), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE).

[0153] The fluorinated polymer may be derived from one or more of the following monomers: fluorocycloethane, vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene and pentafluoropropylene, etc. Alternatively, the fluorinated polymer may be derived from at least two of the following monomers: fluorocycloethane, vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene and pentafluoropropylene.

[0154] In the embodiments of the present application, the polymer can also be obtained by copolymerizing the above structural groups with a small amount of other types of structural groups (e.g., olefin compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid, etc.). The lyophilic properties of such a small amount of monomers are relatively poor, and the above fluorinated polymer monomers are copolymerized with such monomers to improve the swelling rate and compression modulus of the lyophilic polymer.

[0155] In some embodiments, the molecular weight of the lyophilic polymer is 2×10 5 g / mol to 1.2×10 6 g / mol.

[0156] For example, the molecular weight of the lyophilic polymer may be 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol, 1.2×10 6 g / mol or a range consisting of any two of the above values.

[0157] [Ether polymer]

[0158] In some embodiments, the lyophilic polymer comprises an ether polymer.

[0159] In some embodiments, the ether polymer is made into a sheet structure; the sheet structure is (T m2 The elastic modulus G'-energy loss modulus G" curve was obtained by dynamic frequency scanning test at +20)℃. The slope of the elastic modulus G'-energy loss modulus G" curve is K 1 , 1<K 1 <∞,T m2 ℃ represents the melting temperature of ether polymer.

[0160] Specifically, the preparation process of the sheet structure is as follows: the ether polymer is vacuum dried at 80°C for 12 hours. The dried ether polymer is hot-pressed into a sheet by a flat vulcanizer, and the hot-pressing temperature is set to (T m2 +20)℃, calendering thickness of 1-2min, calendering time of 2min, pressure of 8MPa. After calendering for 2min, take out the sample and place it on another vulcanizer of the same model for cold pressing, with a cold pressing pressure of 10MPa. A polymer disc (sheet structure) of fixed size can be obtained by using a circular mold with a diameter of 25mm. For example, the sheet structure can be a disc with a thickness of 1-2mm and a diameter of 25mm; it can also be prepared according to the sample standard required by the test equipment.

[0161] According to the conclusions of classical linear viscoelasticity, for polymers, especially linear polymers, the elastic modulus G'-dissipation modulus G" in the terminal region of the elastic modulus G'-dissipation modulus G" curve (the interval approaching the maximum angular velocity) conforms to the frequency dependence, and the longest chain of the polymer plays a role in the viscoelastic behavior.

[0162] The specific steps of the dynamic frequency sweep test are as follows: The dynamic frequency sweep test is performed using a TA-AR2000EX rotational rheometer (TAinstruments, USA), with a parallel plate diameter of 25 mm and a thickness of 0.9 mm. To ensure that the test is in the linear point-bounce region, the strain is 2% during the dynamic frequency sweep test and the test temperature is T m2 +20℃, test frequency scanning range: 500rad / s≤w 2 ≤0.05rad / s, so as to obtain data in the lowest frequency area possible.

[0163] The dynamic frequency sweep test can characterize the degree of entanglement of the molecular chain under solid phase melting (melt state). Compared with the linear structure or short branched structure, the long branched structure, the mesh structure and the low cross-linked structure have a high degree of entanglement, which will show a deviation from the linear terminal behavior, and the ether polymer will show solid phase behavior. When the ether polymer of the present application meets the above range, the entanglement state of the molecular chain can be further reduced, which is conducive to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether polymer still maintains a certain molecular chain entanglement state, which can effectively store the electrolyte and improve the cycle performance of the battery monomer.

[0164] In some embodiments, 1<K 1 ≤100; optionally, 1<K 1 ≤10. For example, K 1 It can be 1.01, 1.1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000 or a range consisting of any two of the above values.

[0165] In some embodiments, the glass transition temperature of the ether polymer is T g2 ℃, -20≤T g2 ≤35. Exemplarily, the glass transition temperature of the ether polymer can be -20°C, -15°C, -10°C, -5°C, -0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or a range consisting of any two of the above values. Ether polymers have a certain activity above the glass transition temperature, and can buffer external energy through chain segment movement under the action of external force, which is manifested as a certain flexibility, can improve the problem of increased brittleness of the positive electrode sheet caused by thick coating, and can serve as a buffer for the charge and discharge process of the positive active material during the cycle of the positive electrode sheet, thereby improving cycle expansion and improving cycle performance.

[0166] In some embodiments, the ether polymer includes a compound represented by formula (BI),

[0167]

[0168] In formula (BI), R 21 and R 22 Each independently includes a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group; R 23 This includes single bonds, and substituted or unsubstituted methylene groups.

[0169] Optionally, R 21 and R 22 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C1-C10 alkoxy group.

[0170] Optionally, R 21 and R 22 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group.

[0171] Optionally, R 23 Includes single bonds, substituted or unsubstituted C1-C10 methylene groups.

[0172] Optionally, R 23 Includes single bonds, substituted or unsubstituted C1-C5 methylene.

[0173] Illustratively, the ether polymer includes at least one of the compounds represented by formula (BI-1) to the compounds represented by formula (BI-8),

[0174]

[0175]

[0176] In some embodiments, the ether polymer includes a compound represented by formula (BII),

[0177]

[0178] In formula (BII), R 24 To R 27 Each independently includes a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group or an ether group, and R 24 To R 27 At least one of them contains a substituted or unsubstituted alkoxy group or an ether group.

[0179] Optionally, R 24 To R 27 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group or an ether group.

[0180] Optionally, R 24 To R 27 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group or an ether group.

[0181] In some embodiments, the ether polymer includes at least one of the compounds represented by formula (BII-1) to the compounds represented by formula (BII-7),

[0182]

[0183] The above-mentioned polymers are only examples of the structural groups of the main molecular chains. In the embodiments of the present application, the polymers can also be obtained by copolymerizing the above-mentioned structural groups with a small amount of other types of structural groups (for example, olefin compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid and other compounds, etc.).

[0184] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom. The halogen atom may include at least one of a fluorine atom and a bromine atom; a fluorine atom may be selected.

[0185] In some embodiments, the degree of polymerization n of the ether polymer is selected from a positive integer from 1500 to 25000, for example, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000 or a range consisting of any two of the above values.

[0186] Optionally, the polymerization degree n of the ether polymer is selected from a positive integer ranging from 3,000 to 18,000.

[0187] In some embodiments, the molecular weight of the lyophilic polymer is 2×10 5 g / mol to 1.2×10 6 g / mol. For example, the molecular weight of the polymer may be 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol, 1.2×10 6 g / mol or a range consisting of any two of the above values.

[0188] [Ester polymer]

[0189] In some embodiments, the lyophilic polymer comprises an ester polymer.

[0190] In some embodiments, the ester polymer is made into a sheet structure; the sheet structure is (T m3 The elastic modulus G'-energy loss modulus G" curve was obtained by dynamic frequency scanning test at +20)℃. The slope of the elastic modulus G'-energy loss modulus G" curve is K 2 , 1<K 1 <∞,T m3℃ represents the melting temperature of ester polymer.

[0191] Specifically, the preparation process of the sheet structure is similar to the preparation process of the ether polymer, which will not be described in detail here. When the ester polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ester polymer still maintains a certain molecular chain entanglement state, which can effectively store the electrolyte and improve the cycle performance of the battery monomer.

[0192] In some embodiments, 1<K 2 ≤100; optionally, 1<K 2 ≤10. For example, K 2 It can be 1.01, 1.1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000 or a range consisting of any two of the above values.

[0193] In some embodiments, the glass transition temperature of the ester polymer is T g3 ℃, -20≤T g3 ≤35; illustratively, the glass transition temperature of the ester polymer can be -20°C, -15°C, -10°C, -5°C, -0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, or a range consisting of any two of the above values. The ester polymer has a certain activity above the glass transition temperature, and can buffer external energy through chain segment movement under the action of external force, which is manifested as a certain flexibility, can improve the problem of increased brittleness of the positive electrode sheet caused by thick coating, and can serve as a buffer for the charge and discharge process of the positive active material during the cycle of the positive electrode sheet, thereby improving the cycle expansion and improving the cycle performance.

[0194] In some embodiments, the ester polymer includes a compound represented by formula (CI),

[0195]

[0196] In formula (CI), R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted alkyl group; R 34 It includes a substituted or unsubstituted alkyl group, or a substituted or unsubstituted hydroxyalkyl group.

[0197] Optionally, R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C10 alkyl group.

[0198] Optionally, R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group.

[0199] In some embodiments, R 34 Includes substituted or unsubstituted C1-C10 alkyl groups, or substituted or unsubstituted C1-C10 hydroxyalkyl groups.

[0200] In some embodiments, R 34 It includes substituted or unsubstituted C1-C8 alkyl groups, or substituted or unsubstituted C1-C8 hydroxyalkyl groups.

[0201] In some embodiments, R 31 This includes a hydrogen atom, or a substituted or unsubstituted methyl group.

[0202] In some embodiments, R 32 and R 33 Each independently includes a hydrogen atom.

[0203] Exemplarily, the ester polymer includes at least one of the compounds represented by formula (CI-1) to the compounds represented by formula (CI-15),

[0204]

[0205]

[0206] In some embodiments, the ester polymer includes a compound represented by formula (CII),

[0207]

[0208] In formula (CII), R 35 Substituted or unsubstituted methylene groups are included.

[0209] Optionally, R 35 This includes substituted or unsubstituted C1-C10 methylene groups.

[0210] Optionally, R 35 This includes substituted or unsubstituted C2-C6 methylene groups.

[0211] Optionally, R 35 This includes substituted or unsubstituted C2-C4 methylene groups.

[0212] Illustratively, the ester polymer includes at least one of the compounds represented by formula (CII-1) to the compounds represented by formula (CII-5),

[0213]

[0214]

[0215] In some embodiments, the ester polymer includes a compound represented by formula (CIII),

[0216]

[0217] In formula (CIII), R 36 , R 37 and R 38 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R 39 Including substituted or unsubstituted C1-C8 alkyl;

[0218] Optionally, R 36 , R 37 and R 38 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C4 alkyl group.

[0219] Illustratively, the ester polymer includes at least one of the compounds represented by formula (CIII-1) to the compounds represented by formula (CIII-5),

[0220]

[0221] The above-mentioned polymers are only examples of the structural groups of the main molecular chains. In the embodiments of the present application, the lyophilic polymer can also be obtained by copolymerizing the above-mentioned structural groups with a small amount of other types of structural groups (for example, olefin compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid and other compounds, etc.).

[0222] When the above groups are substituted, the substituents may include one or more of a nitrile group (—CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom.

[0223] In some embodiments, the degree of polymerization n of the ester polymer is selected from a positive integer from 800 to 20,000, for example, 800, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000 or a range consisting of any two of the above values.

[0224] In some embodiments, the degree of polymerization n of the ester polymer is a positive integer selected from 1,000 to 15,000.

[0225] In some embodiments, the molecular weight of the lyophilic polymer is 2×10 5 g / mol to 1.2×10 6 g / mol.

[0226] For example, the molecular weight of the lyophilic polymer may be 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol, 1.2×10 6 g / mol or a range consisting of any two of the above values.

[0227] [Aldehyde and Ketone Polymers]

[0228] In some embodiments, the lyophilic polymer comprises an aldehyde-ketone polymer.

[0229] In some embodiments, the aldehyde-ketone polymer is made into a sheet structure; the sheet structure is (T m4 The elastic modulus G'-energy loss modulus G" curve was obtained by dynamic frequency scanning test at +20)℃. The slope of the elastic modulus G'-energy loss modulus G" curve is K 3 , 0.8≤K 3 <∞,T m4 ℃ represents the melting temperature of aldehyde-ketone polymers.

[0230] Specifically, the preparation process of the sheet structure is similar to the preparation process of the ether polymer, which will not be described in detail here. When the aldehyde-ketone polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the aldehyde-ketone polymer still maintains a certain molecular chain entanglement state, which can effectively store the electrolyte and improve the cycle performance of the battery monomer.

[0231] In some embodiments, 0.8≤K 3 ≤100; optionally, 0.8≤K 3 ≤10. For example, K 3 It can be 0.8, 0.85, 0.9, 1, 1.01, 1.1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000 or a range consisting of any two of the above values.

[0232] In some embodiments, the glass transition temperature of the aldehyde-ketone polymer is T g4 ℃, -20≤T g4≤35; illustratively, the glass transition temperature of the aldehyde-ketone polymer can be -20°C, -15°C, -10°C, -5°C, -0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or a range consisting of any two of the above values. The aldehyde-ketone polymer has a certain activity above the glass transition temperature, and can buffer external energy through chain segment movement under the action of external force, which is manifested as a certain flexibility, can improve the problem of increased brittleness of the positive electrode sheet caused by thick coating, and can serve as a buffer for the charge and discharge process of the positive active material during the cycle of the positive electrode sheet, thereby improving the cycle expansion and improving the cycle performance.

[0233] In some embodiments, the aldehyde-ketone polymer comprises a compound represented by formula (DI),

[0234]

[0235] In formula (DI), R 41 Including single bonds, substituted or unsubstituted C1-C6 methylene; R 42 Includes a hydrogen atom, and a substituted or unsubstituted C1-C6 alkyl group.

[0236] Optionally, R 41 Includes single bonds, substituted or unsubstituted C1-C2 methylene.

[0237] Optionally, R 42 This includes a hydrogen atom, and a substituted or unsubstituted C1-C3 alkyl group.

[0238] In the embodiments of the present application, a single bond means that the group does not exist, and the atoms on both sides of the group are connected by a single bond, for example, R 41 is a single bond, indicating that R 41 The carbon atoms on both sides are connected by single bonds.

[0239] Illustratively, the aldehyde-ketone polymer includes at least one of the compounds represented by formula (DI-1) to the compounds represented by formula (DI-6),

[0240]

[0241] Exemplarily, the aldehyde-ketone polymer includes a compound represented by formula (DII),

[0242]

[0243] In formula (DII), R 43 To R 46Each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s are each independently selected from an integer from 0 to 5, and at least one of r and s is selected from a positive integer.

[0244] Optionally, R 43 To R 46 Each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C2 hydroxyalkyl group, or a substituted or unsubstituted C1-C2 alkoxy group.

[0245] In some embodiments, the aldehyde-ketone polymer includes at least one of the compounds represented by formula (DII-1) to the compounds represented by formula (DII-4),

[0246]

[0247]

[0248] The above polymers are only examples of structural groups of the main molecular chain. In the embodiments of the present application, the polymers can also be obtained by copolymerizing the above structural groups with other types of structural groups (such as olefin compounds, enol compounds, acrylonitrile compounds, etc.).

[0249] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom. The halogen atom may include at least one of a fluorine atom, a bromine atom, and a chlorine atom.

[0250] In some embodiments, the degree of polymerization n of the aldehyde-ketone polymer is selected from a positive integer of 500 to 15000, for example, 500, 800, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000 or a range consisting of any two of the above values.

[0251] Optionally, the degree of polymerization n of the aldehyde-ketone polymer is selected from a positive integer ranging from 500 to 10,000.

[0252] In some embodiments, the molecular weight of the aldehyde-ketone polymer is 1.2×10 5 g / mol to 1.2×10 6 g / mol.

[0253] For example, the molecular weight of the aldehyde-ketone polymer may be 1.2×10 5 g / mol, 2×10 5g / mol, 5×10 5 g / mol, 8×10 5 g / mol, 1×10 6 g / mol, 1.0×10 6 g / mol, 1.2×10 6 g / mol or a range consisting of any two of the above values.

[0254] In some embodiments, the lyophilic polymer may be a homopolymer or a copolymer. In addition to the monomers capable of forming fluorinated polymers, ether polymers, ester polymers and aldehyde-ketone polymers mentioned above, the monomers of the lyophilic polymer may also include olefin monomers and the like.

[0255] The relevant parameters of the lyophilic polymer according to the embodiment of the present application can be detected by the following method:

[0256] The groups of the lyophilic polymers of the embodiments of the present application can be detected by infrared spectrophotometry IR. Specifically, the lyophilic polymers are tested by a Thermo Nicolet Nexus 670 attenuated total reflection Fourier transform infrared spectrometer (FTIR-ATR), and then tested in accordance with the standard GB / T6040-2002. The test range is: ATR method 600-4000cm -1 ; Repeatability: ±2cm -1 ; Resolution: better than 4cm -1 ; Transmission depth 0.2~0.6μm.

[0257] The structure of the lyophilic polymer in the embodiment of the present application can be tested by nuclear magnetic resonance (NMR). Specifically, 1H NMR and 13C NMR are performed on a Varian Mercury Plus-400 NMR instrument at a test temperature of 20° C., TMS as an internal standard, and CDCl 3 As a solvent, the proton resonance frequency is 400 MHz.

[0258] The polymer monomer type of the lyophilic polymer of the embodiment of the present application (especially suitable for monomers with a small proportion in the polymer) can be tested by pyrolysis-gas chromatography-mass spectrometry. The specific test steps are as follows: accurately weigh 0.5 mg of sample and put it into the sample cup. After fixing it to the injection rod, put it into the pyrolyzer installed near the GC (gas chromatography) injection port. After the temperature of the pyrolyzer reaches the set temperature, press the injection button, and the sample cup quickly falls into the core of the pyrolysis furnace by free fall. In the inert gas N 2 In the atmosphere, the volatile components are instantly vaporized and carried into the gas chromatography column by the carrier gas for separation. Finally, they are detected by the flame ionization detector FID or the mass spectrometer MS to obtain a gas chromatogram or a total ion flow diagram.

[0259] The molecular weight of the lyophilic polymer in the embodiment of the present application is well known in the art, and can be measured using equipment and methods commonly used in the art. It can be tested by gel permeation chromatography GPC in accordance with GB / T21863-2008. The specific testing steps are: take an appropriate amount of the sample to be tested (the sample concentration is guaranteed to be 8%-12% shading), add 20 ml of deionized water, and simultaneously ultraviolet for 5 minutes (53KHz / 120W) to ensure that the sample is completely dispersed, and then the sample is measured in accordance with GB / T19077-2016 / ISO 13320:2009 standard.

[0260] In some embodiments, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer may be disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0261] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, an aluminum foil or an aluminum alloy foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include a combination of one or more selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, and the polymer material base layer may include a combination of one or more selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0262] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application embodiment has no particular restrictions on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes a combination of one or more selected from superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the positive electrode conductive agent is less than 5%.

[0263] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. The present application embodiment has no particular restrictions on the type of positive electrode binder. As an example, the positive electrode binder may include a combination of one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylic resin. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the positive electrode binder is less than 5%. Compared with the crystallinity of the fluorinated polymer in the embodiment of the present application, the crystallinity of the positive electrode binder is higher.

[0264] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, the lyophilic polymer, the optional conductive agent, the optional binder and any other components in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this. Of course, the preparation of the positive electrode sheet is not limited to the above method, and the preparation method mentioned above can also be used.

[0265] Battery Cell

[0266] In the second aspect, the embodiments of the present application further provide a battery cell, which includes a positive electrode sheet according to any embodiment of the first aspect of the present application, and can effectively improve the energy density, cycle performance and power performance of the battery cell.

[0267] [Negative electrode]

[0268] In some embodiments, the electrode assembly includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0269] The negative electrode active material may adopt the negative electrode active material for battery cells known in the art. As an example, the negative electrode active material may include but is not limited to at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material. The tin-based material may include at least one of elemental tin, tin oxide and tin alloy material.

[0270] In some embodiments, the negative electrode current collector has two surfaces opposite to each other in the thickness direction thereof, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0271] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The embodiment of the present application has no particular restrictions on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the negative electrode conductive agent is ≤5%.

[0272] In some embodiments, the negative electrode film layer may also optionally include a negative electrode binder. The embodiment of the present application has no particular restrictions on the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the negative electrode binder is ≤5%.

[0273] In some embodiments, the negative electrode film layer may further include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc. In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the other additives is ≤2%.

[0274] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0275] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to this. Of course, the preparation of the negative electrode sheet is not limited to the above method, and the preparation method mentioned above can also be used.

[0276] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate of the present application also includes a protective layer covering the surface of the negative electrode film layer.

[0277] [Isolation film]

[0278] In some embodiments, the battery cell includes a separator.

[0279] In some embodiments, the isolation film includes a substrate.

[0280] In some embodiments, a separator includes a substrate and a coating disposed on at least one surface of the substrate.

[0281] The embodiments of the present application have no particular restrictions on the material of the substrate, and any known substrate with good chemical stability and mechanical stability can be selected, such as at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The substrate can be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer can be the same or different.

[0282] In some embodiments, the coating layer may further include a heat-resistant filler. Further, the heat-resistant filler may include at least one of inorganic particles and organic particles.

[0283] In some embodiments, the decomposition temperature of the heat-resistant filler may be above 200° C., so that the heat-resistant filler may have the characteristics of good thermal stability and being difficult to decompose, thereby further improving the heat resistance of the isolation film.

[0284] The inorganic particles have the characteristics of high thermal stability and not easy to decompose. Optionally, the inorganic particles include at least one of inorganic particles with a dielectric constant of 5 or more, inorganic particles with ion conductivity but not storing ions, and inorganic particles capable of electrochemical reactions.

[0285] Alternatively, the inorganic particles having a dielectric constant of 5 or more include boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O 3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O 3 (abbreviated as PLZT, 0<m<1, 0<n<1), Pb(Mg 3 Nb 2 / 3 ) 3 -PbTiO 3(abbreviated as PMN-PT), and at least one of their respective modified inorganic particles. Optionally, each inorganic particle may be modified by chemical modification and / or physical modification. Chemical modification methods include coupling agent modification (for example, using silane coupling agent, titanate coupling agent, etc.), surfactant modification, polymer grafting modification, etc. Physical modification methods may be mechanical force dispersion, ultrasonic dispersion, high energy treatment, etc. The modification treatment can reduce the agglomeration of inorganic particles, thereby enabling them to form a more stable and uniform spatial network structure with nanocellulose; in addition, by selecting coupling agents, surfactants or polymer-modified inorganic particles with specific functional groups, it is also helpful to improve the coating's wetting properties for the electrolyte and improve the bonding strength between the coating and the substrate.

[0286] Alternatively, inorganic particles having ion conductivity but not storing ions include Li 3 PO 4 、Lithium Titanium Phosphate Li x1 Ti y1 (PO 4 ) 3 、Lithium Aluminum Titanium Phosphate Li x2 Al y2 Ti z1 (PO 4 ) 3 、(LiAlTiP) x3 O y3 Type glass, lanthanum titanate lithium Li x4 La y4 TiO 3 、Lithium germanium thiophosphate Li x5 Ge y5 P z2 S w 、Lithium Nitride Li x6 N y6 、SiS 2 Type Glass Li x7 Si y7 S z3 and P 2 S 5 Type Glass Li x8 P y8 S z4 At least one of 0<x1<2, 0<y1<3, 0<x2<2, 0<y2<1, 0<z1<3, 0<x3<4, 0<y3<13, 0<x4<2, 0<y4<3, 0<x5<4, 0<y5<1, 0<z2<1, 0<w<5, 0<x6<4, 0<y6<2, 0<x7<3, 0<y7<2, 0<z3<4, 0<x8<3, 0<y8<3, 0<z4<7. This can further improve the ion transport characteristics of the isolation membrane.

[0287] Organic particles have good thermal stability and are not easy to decompose, which can improve the heat resistance of the isolation membrane; at the same time, when the internal temperature of the battery cell reaches the melting point of the organic particles due to overcharge abuse, heat abuse, etc., the organic particles can also melt and be sucked into the micropores of the substrate due to capillary action to play a role in closing the pores and breaking the circuit, which is beneficial to ensure that the battery cell has high safety performance.

[0288] In some embodiments, the organic particles include, but are not limited to, at least one of polyethylene particles, polypropylene particles, polystyrene particles, melamine resin particles, phenolic resin particles, polyester particles (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, polyaryletherketone particles, and copolymers of butyl acrylate and ethyl methacrylate (e.g., cross-linked polymers of butyl acrylate and ethyl methacrylate).

[0289] In some embodiments, the coating further comprises a binder. The present application has no particular restrictions on the type of the binder, and any known material with good bonding properties can be selected. As an example, the binder comprises at least one of an aqueous solution type acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, sodium acrylate monomers or a copolymer with other comonomers), polyvinyl alcohol, isobutylene-maleic anhydride copolymer, and polyacrylamide.

[0290] Optionally, the content of binder in the coating is <30%, based on the mass of the coating.

[0291] [Electrolyte]

[0292] In some embodiments, the battery cells include an electrolyte.

[0293] During the charge and discharge process of the battery cell, active ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays a role in conducting active ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to actual needs.

[0294] The electrolyte includes electrolyte salt and solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual needs.

[0295] As an example, the electrolyte salt may include, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), at least one of lithium difluorobis(oxalate) phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0296] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0297] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature power performance.

[0298] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process and / or a lamination process.

[0299] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0300] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0301] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. Figure 2 The battery cell 5 is a square structure as an example.

[0302] In some embodiments, Figure 2 and Figure 3 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0303] The preparation method of the battery cell of the present application is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and the battery cell is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0304] In some embodiments of the present application, the battery cells according to the present application can be assembled into a battery module. The number of battery cells contained in the battery module can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module.

[0305] Figure 4 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 4 As shown, in the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0306] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0307] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0308] Both the battery module 4 and the battery pack can be used as specific examples of batteries in the embodiments of the present application.

[0309] Figure 5 and Figure 6 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 5 and Figure 6As shown, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0310] Electrical devices

[0311] In a third aspect, the present application provides an electrical device, which includes at least one of the battery cell, battery module and battery pack of the present application. The battery cell, battery module and battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc. In some embodiments, the battery cell includes an injection hole, which is used to inject an electrolyte; when the battery cell is applied to the electrical device, the injection hole is located at the bottom of the battery cell in the vertical direction. Since the amount of free electrolyte in the battery cell is very small, or even no free electrolyte, when the injection hole is set at the bottom of the battery cell in the vertical direction, the reliability of the battery cell can also be improved, thereby improving the reliability of the electrical device.

[0312] The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements. Figure 7 Schematic diagram of an electric device as an example. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack 1 or a battery module can be used. As another example, the electric device can be a mobile phone, a tablet computer, a laptop computer, etc. The electric device is usually required to be light and thin, and a battery cell can be used as a power source.

[0313] Example

[0314] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0315] Example 1 Preparation of lithium ion battery

[0316] (1) Preparation of positive electrode sheet:

[0317] The lyophilic polymer, the positive electrode active material, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) were added into N-methylpyrrolidone (NMP) in a mass ratio of 0.2:97.3:2:0.5 and mixed to prepare a positive electrode slurry.

[0318] The positive electrode slurry was coated on the current collector aluminum foil and dried at 85°C, then cold pressed, trimmed, cut, and striped, and then dried at 85°C under vacuum for 4 hours to form a positive electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) was 48%.

[0319] (2) Preparation of negative electrode sheet:

[0320] The negative electrode active material artificial graphite, conductive agent carbon black, adhesive styrene butadiene rubber (SBR), and thickener sodium hydroxymethyl cellulose (CMC) were added to deionized water at a weight ratio of 95:3:1:1 and mixed evenly to form a negative electrode slurry. The negative electrode slurry was coated on the current collector copper foil and dried at 85°C, then cold pressed, trimmed, cut, and striped, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet.

[0321] (3) Preparation of electrolyte:

[0322] The electrolyte includes a non-aqueous organic solvent and a lithium salt. The non-aqueous organic solvent includes ethylene carbonate EC and ethyl methyl carbonate (EMC) (volume ratio 3:7). The lithium salt includes 1 mol / L LiPF 6 .

[0323] (4) Preparation of lithium-ion batteries:

[0324] Using polyethylene film (PE) as a separator, the positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer packaging shell, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0325] Example 2 to Example 6

[0326] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the types of lyophilic polymers were adjusted in Examples 2 to 6.

[0327] Example 7 to Example 10

[0328] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the amount of the lyophilic polymer used was adjusted in Examples 7 to 10.

[0329] Example 11 to Example 15

[0330] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that the types of active materials were adjusted in Examples 11 to 15.

[0331] Comparative Example 1 and Comparative Example 3

[0332] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that no lyophilic polymer was used in Comparative Example 1.

[0333] (1) Preparation of positive electrode sheet:

[0334] The positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are added to N-methylpyrrolidone (NMP) and mixed to form a positive electrode slurry. The mass ratio of positive electrode active material, conductive carbon black, and PVDF in the positive electrode slurry is 97.5:2:0.5. The positive electrode slurry is coated on the current collector aluminum foil and dried at 85°C and then cold pressed. After trimming, cutting, and striping, it is dried under vacuum conditions at 85°C for 4 hours to form a positive electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) is 48%.

[0335] Comparative Example 2 and Comparative Example 4

[0336] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the types of polymers were adjusted in Comparative Examples 2 and 4.

[0337] Example 16 and Example 17

[0338] A lithium-ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the positive electrode film layers of Examples 16 and 17 were double-layer coated.

[0339] Test Section

[0340] 1. Lithium-ion battery capacity retention test

[0341] The lithium-ion battery prepared in the embodiment and comparative example is charged to V1 at a constant current of 0.5C at room temperature, left for 30 minutes, and then discharged to V2 at 0.5C. The obtained capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery, and record the discharge capacity Cn of the battery after the nth cycle at the same time. Then, the battery capacity retention rate after each cycle is Pn=Cn / C0*100%. The 2000 point values ​​of P1, P2...P2000 are used as the vertical coordinates, and the corresponding number of cycles is used as the horizontal coordinates to obtain a dot graph of the battery capacity retention rate and the number of cycles. Among them, V1 is the upper limit of the battery voltage, and V2 is the lower limit of the battery use.

[0342] In the test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 2000th cycle corresponds to n=2000. For example, the battery capacity retention rate data corresponding to Example 1 in Table 1 is the data measured after 2000 cycles under the above test conditions, that is, the value of P2000. The test process of Comparative Example 1 and other embodiments is the same as above.

[0343] Among them, the determination of V1 and V2 in the above test process is determined by the type of positive electrode active material in the battery:

[0344] The positive electrode active material is LiFePO 4 V1 = 2.0V, V2 = 3.65V;

[0345] The positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.9 Co 0.05 Mn 0.05 O 2 V1 = 2.8V, V2 = 4.25V;

[0346] The positive electrode active material is LiMn 0.5 Fe 0.5 PO 4 、LiMn 0.4 Fe 0.6 PO 4 V1=2.0V, V2=4.1V.

[0347] 2. Energy density of battery cells

[0348] The energy density of the battery cell in the embodiments of the present application is a well-known meaning in the art, which specifically refers to the weight energy transferred during each cycle of charge / discharge, usually expressed in units of Wh / Kg; when calculating the energy density, only the mass of the film layer in the electrode plate can be considered; the mass of the battery cell can also be considered, that is, in addition to the mass of the film layer, the mass of other components is also considered. Other components are all components in the battery cell except the film layer, for example, other components may include positive current collector, negative current collector, separator, electrolyte, electrode lead, insulating tape and aluminum casing, etc. When calculating the energy density in the embodiments of the present application, the mass of the battery cell is considered.

[0349] The energy density of the battery cell in the embodiment of the present application can be tested by using equipment and methods known in the art. For example, after the battery cell is shipped, it is charged to V1 at 1 / 3C constant current, then charged to 0.05C at constant voltage, and left to stand for 30 minutes; discharged to V2 at 1 / 3C, and the discharge capacity D0 is recorded; the mass M0 of the battery cell is weighed, and the energy density of the battery cell is D0 / M0. Among them, V1 is the upper limit of the battery voltage, and V2 is the lower limit of the battery use, and the specific values ​​are the same as above.

[0350] Test Results

[0351] The test results are shown in Table 1.

[0352] Table 1

[0353]

[0354] In Table 1, 85% vinylidene fluoride + 15% perfluoropropylene in the monomer means that, based on the total mass of the monomer, the mass content of vinylidene fluoride is 85%, and the mass content of perfluoropropylene is 15%.

[0355] A crystallinity of " / " indicates that the polymer may be in an amorphous state without obvious crystallinity.

[0356] A melting temperature of “ / ” indicates that the polymer may be in an amorphous state and has no obvious melting temperature.

[0357] Table 2

[0358]

[0359] In Table 2, the lyophilic polymer content of the positive electrode sheet is 0.2%, which means that the mass content of the lyophilic polymer is 0.2% based on the total mass of the positive electrode film layer.

[0360] The amount of the lyophilic polymer added to the positive electrode plate is 0.00%, indicating that no lyophilic polymer is added to the positive electrode film layer.

[0361] As can be seen from Table 2, the positive electrode sheets of Comparative Examples 1 and 3 do not have a lyophilic polymer added. During the cycle of the lithium-ion battery, due to the thick coating of the positive electrode sheets in the lithium-ion battery, the positive electrode film layer is poorly infiltrated, and polarization and other problems are easily generated, which deteriorates the cycle performance and power performance of the lithium-ion battery.

[0362] Although polymers are added to the electrodes in Comparative Examples 2 and 4, the polymers have poor lyophilicity, which not only results in low liquid retention efficiency, but also has high impedance which deteriorates the battery kinetics performance.

[0363] In the embodiment of the present application, a lyophilic polymer is added to the positive electrode sheet, and the lyophilic polymer has a high affinity with the electrolyte, which can increase the electrolyte infiltration rate of the positive electrode film layer, improve the polarization phenomenon and the interface side reaction of the positive electrode film layer, and thus improve the cycle life. Since the lyophilic polymer is configured to coat the electrolyte on the surface of the positive electrode active material particles, an effective liquid storage point is formed on the surface of the positive electrode active material particles, which can accelerate the migration rate of lithium ions, thereby improving the power performance of the battery cell.

[0364] Table 3

[0365]

[0366] In Table 3, Examples 16 and 17 both use lyophilic polymer A in the positive electrode film layer.

[0367] The positive electrode active material of Example 16 includes LiFePO 4 .

[0368] In Example 17, the positive electrode active material includes LiNi 0.8 Co 0.1 Mn 0.1 O 2 .

[0369] As shown in Tables 2 and 3, compared with the single-layer coating of Example 1, Examples 16 and 17 use double-layer coating, and the positive electrode film layer includes a first layer and a second layer, which is more conducive to thick coating to form a higher coating weight. The coating weight of the first layer and the second layer is different, and the difference in the mass content of the lyophilic polymer makes the electrolyte infiltration effect in each layer better, which is conducive to improving the cycle performance and power performance of the lithium-ion battery.

[0370] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions and modifications may be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material and a lyophilic polymer, and the coating weight of the positive electrode film layer is ≥300 mg / 1540.25 mm 2 ; Optionally, the coating weight of the positive electrode film layer is 300 mg / 1540.25 mm 2 Up to 500mg / 1540.25mm 2 .

2. The positive electrode sheet according to claim 1, wherein: The positive electrode active material includes a lithium-containing phosphate; Optionally, based on the total mass of the positive electrode active material, the mass content of the lithium-containing phosphate is ≥ 90%; Further optionally, the coating weight of the positive electrode film layer is ≥400mg / 1540.25mm 2 ; Optional: 400mg / 1540.25mm 2 Up to 500mg / 1540.25mm 2 .

3. The positive electrode sheet according to claim 2, wherein: The lithium-containing phosphate includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate and modified compounds of each of them.

4. The positive electrode sheet according to claim 1, wherein: The positive electrode active material includes a lithium-containing transition metal oxide; Optionally, based on the total mass of the positive electrode active material, the mass content of the lithium-containing transition metal oxide is ≥ 90%; Further optionally, the coating weight of the positive electrode film layer is ≥300 mg / 1540.25 mm 2 ; Optional: 300mg / 1540.25mm 2 Up to 500mg / 1540.25mm 2 .

5. The positive electrode sheet according to claim 4, wherein: The lithium transition metal oxide includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their respective modified compounds.

6. The positive electrode sheet according to any one of claims 1 to 5, wherein: Based on the total mass of the positive electrode film layer, the mass content of the lyophilic polymer is ≤5%; Optionally, the mass content of the lyophilic polymer is ≤1%.

7. The positive electrode sheet according to any one of claims 1 to 6, wherein: The positive electrode film layer comprises multiple sub-layers, and the coating weight of the multiple sub-layers decreases step by step in the direction from the positive electrode current collector to the positive electrode film layer; Optionally, the multilayer sublayer includes a first layer and a second layer, the first layer is disposed on the surface of the positive electrode current collector, the second layer is located on a side of the first layer away from the positive electrode current collector, and the coating weight of the first layer is greater than the coating weight of the second layer; Further optionally, the mass content of the lyophilic polymer in the first layer is greater than the mass content of the lyophilic polymer in the second layer.

8. The positive electrode sheet according to any one of claims 1 to 7, wherein: The lyophilic polymer comprises a fluorinated polymer, and the crystallinity of the fluorinated polymer measured by differential scanning calorimetry is Xc1%, 0<Xc1≤28; The melting temperature of the fluorinated polymer is T m1 ℃, 0<T m1 ≤130; Further optionally, the glass transition temperature of the fluorinated polymer is T g1 ℃, -30≤T g1 ≤40; Further optionally, the fluorinated polymer comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII), In formula (AI) and formula (AII), R 11 , R 12 , R 13 and R 14 Each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom; In formula (AIII), R 15 Including single bonds, substituted or unsubstituted C1-C3 alkyl; p is a positive integer selected from 1 to 3; n is a positive integer selected from 1,000 to 30,000.

9. The positive electrode sheet according to any one of claims 1 to 8, wherein: The lyophilic polymer includes an ether polymer, and the ether polymer is made into a sheet structure; the sheet structure is m2 The elastic modulus G'-energy loss modulus G" curve is obtained by dynamic frequency scanning test at +20)℃, and the slope of the elastic modulus G'-energy loss modulus G" curve is K1, 1<K1<∞, T m2 ℃ represents the melting temperature of the ether polymer; optionally, 1<K1≤100; further optionally, 1<K1≤10; Optionally, the glass transition temperature of the ether polymer is T g2 ℃, -20≤T g2 ≤35; Further optionally, the ether polymer includes at least one of the compound represented by formula (BI) and the compound represented by formula (BII), In formula (BI), R 21 and R 22 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R 23 Including substituted or unsubstituted C1-C5 alkylene; In formula (BII), R 24 To R 27 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group or an ether group, and R 24 To R 27 At least one of them contains a substituted or unsubstituted C1-C3 alkoxy group or an ether group; The polymerization degree n of the ether polymer is selected from a positive integer ranging from 1500 to 25000.

10. The positive electrode sheet according to any one of claims 1 to 9, wherein: The lyophilic polymer includes the ester polymer, and the ester polymer is made into a sheet structure; the sheet structure is (T m3 The elastic modulus G'-energy loss modulus G" curve was obtained by dynamic frequency scanning test at 20 °C. The slope of the elastic modulus G'-energy loss modulus G" curve is K2, 1<K2<∞, T m3 ℃ represents the melting temperature of the ester polymer; optionally, 1<K2≤100; further optionally, 1<K2≤10; Optionally, the glass transition temperature of the ester polymer is T g3 ℃, -20≤T g3 ≤35; Further optionally, the ester polymer includes at least one of the compounds represented by formula (CI) to the compounds represented by formula (CIII), In formula (CI), R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R 34 Including substituted or unsubstituted C1-C8 alkyl, or substituted or unsubstituted C1-C8 hydroxyalkyl; In formula (CII), R 35 including substituted or unsubstituted C2-C6 methylene; optionally, R 35 Each independently comprises a substituted or unsubstituted C2-C4 methylene group; In formula (CIII), R 36 , R 37 and R 38 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R 39 Including substituted or unsubstituted C1-C8 alkyl; Optionally, R 36 , R 37 and R 38 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C4 alkyl group; The polymerization degree n of the ester polymer is selected from a positive integer ranging from 800 to 20,000.

11. The positive electrode sheet according to any one of claims 1 to 10, wherein: The lyophilic polymer includes an aldehyde-ketone polymer, and the aldehyde-ketone polymer is made into a sheet structure; the sheet structure is m4 The elastic modulus G'-energy loss modulus G" curve is obtained by dynamic frequency scanning test at 20 ° C. The slope of the elastic modulus G'-energy loss modulus G" curve is K3, 0.8≤K3<∞, T m4 ℃ represents the melting temperature of the aldehyde-ketone polymer; Optionally, 0.8≤K3≤100; further optionally, 0.8≤K3≤10; Optionally, the glass transition temperature of the aldehyde-ketone polymer is T g4 ℃, -20≤T g4 ≤35; Further optionally, the aldehyde-ketone polymer comprises at least one of the compound represented by formula (DI) and the compound represented by formula (DII), In formula (DI), R 41 Including single bonds, substituted or unsubstituted C1-C6 methylene; R 42 Including hydrogen atom, substituted or unsubstituted C1-C6 alkyl; In formula (DII), R 43 To R 46 Each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s are each independently selected from integers from 0 to 5, and at least one of r and s is selected from a positive integer; The polymerization degree n of the aldehyde-ketone polymer is selected from a positive integer ranging from 500 to 15,000.

12. The positive electrode sheet according to any one of claims 1 to 11, wherein: The molecular weight of the lyophilic polymer is 2.0×10 5 g / mol to 1.2×10 6 g / mol.

13. A battery comprising the positive electrode sheet according to any one of claims 1 to 12.

14. An electrical device comprising the battery according to claim 13.

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