Battery and electric device

Abstract

The invention relates to a battery and an electric device, the battery comprises an electrode pole piece, the electrode pole piece comprises a current collector and a film layer arranged on at least one side of the current collector, the film layer comprises an active material and a lyophilic polymer, and the energy density of the battery is greater than or equal to 300Wh / Kg.

Description

Technical Field

[0001] The present application relates to 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 have both high energy density and cycle performance. Summary of the invention

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

[0005] In a first aspect, the present application provides a battery, wherein the battery comprises an electrode plate, wherein the electrode plate comprises a current collector and a film layer disposed on at least one side of the current collector, wherein the film layer comprises an active material and a lyophilic polymer,

[0006] Among them, the energy density of the battery is ≥300Wh / Kg.

[0007] Therefore, in the embodiment of the present application, the active material can contribute to the energy density of the battery cell and improve the energy density; the embodiment of the present application also arranges a lyophilic polymer in the film layer of the electrode plate. The lyophilic polymer can be evenly mixed with the active material particles when preparing the slurry to form a film layer. The lyophilic polymer has affinity for the electrolyte and can improve the affinity between the electrode plate and the electrolyte. The lyophilic polymer is configured to coat the electrolyte and can form effective liquid storage points on the surface of the active material particles, thereby improving the liquid storage capacity of the electrode plate. The wetting performance of the electrolyte on the film layer is improved, which can reduce concentration polarization and improve the cycle performance of the battery.

[0008] In some embodiments, the energy density of the battery is 300 Wh / Kg to 500 Wh / Kg.

[0009] In some embodiments, the electrode plate includes a positive electrode plate, and the active material in the positive electrode plate includes a molecular formula of Li x Ni a Co b M (1-a-b)O2 compound and modified compound thereof, wherein 0.60≤x≤1.20, 0.85≤a<1.00, 0<b≤0.10, and a+b<1.00, M includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, La and Nb; optionally, 0.90≤a<1.0; further optionally, the active material in the positive electrode sheet includes a molecular formula of LiNi 0.85 Co 0.10 M 0.05 O2、LiNi 0.92 Co 0.04 M 0.04 O2、LiNi 0.92 Co 0.05 M 0.03 O2、LiNi 0.92 Co 0.06 M 0.02 O2、LiNi 0.93 Co 0.03 M 0.04 O2 and LiNi 0.93 Co 0.025 M 0.045 At least one compound in O2. The specific capacity of the above positive electrode active material is relatively high, which significantly improves the energy density of the battery.

[0010] In some embodiments, the active material in the positive electrode sheet includes single crystal particles and polycrystalline particles, and the volume average particle size Dv50 of the single crystal particles is smaller than the volume average particle size Dv50 of the polycrystalline particles; optionally, the volume average particle size Dv50 of the single crystal particles is 2μm to 5μm; optionally, the volume average particle size Dv50 of the polycrystalline particles is 5μm to 10μm. By combining the different particle sizes of the single crystal particles and the polycrystalline particles, the compaction density of the positive electrode film layer can be improved, which is conducive to further improving the energy density of the battery cell.

[0011] In some embodiments, based on the total mass of active materials in the positive electrode sheet, the mass content of the single crystal particles is 10% to 30%. When the mass content of the single crystal particles is within the above range, they can be further combined with polycrystalline particles to increase the compaction density of the positive electrode film layer, thereby increasing the energy density of the battery cell.

[0012] In some embodiments, the compaction density of the film layer in the positive electrode sheet is ≥3.6 g / cm 3 , optional 3.6g / cm 3 Up to 3.8g / cm 3 When the compaction density of the positive electrode film layer is within the above range, the energy density of the battery cell can be significantly improved.

[0013] In some embodiments, the electrode plate includes a negative electrode plate, and the active material in the negative electrode plate includes at least a silicon-based material; optionally, the silicon-based material includes at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material; optionally, based on the total mass of the active material in the negative electrode plate, the mass content of the silicon-based material is ≥5%; optionally, it is 15% to 50%. When the mass content of the silicon-based material is within the above range, the energy density of the battery cell can be further improved.

[0014] In some embodiments, the compaction density of the negative electrode film layer is ≥1.5 g / cm 3 , optional 1.5g / cm 3 Up to 2.0g / cm 3 The compaction density of the negative electrode film layer is relatively high, which is beneficial to improving the energy density of the battery.

[0015] In some embodiments, based on the total mass of the film layer, the mass content of the lyophilic polymer is ≤5%; optionally 0.05% to 5%; and / or the coating weight of the lyophilic polymer is 0.5 mg / 1540.25 mm 2 Up to 5mg / 1540.25mm 2 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 active material particles, improve the liquid storage capacity of the membrane layer, and improve the wettability of the electrolyte to the active material in the membrane layer, thereby facilitating the improvement of the cycle performance of the battery.

[0016] In some embodiments, the lyophilic polymer comprises a fluorinated polymer, and the crystallinity of the fluorinated polymer measured by differential scanning calorimetry is Xc1, 0<Xc1≤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 14Each 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, fluorinated polymers have relatively low crystallinity, melting temperature or glass transition temperature. Fluorinated polymers have certain activity above the glass transition temperature. Under the action of external force, they can buffer external energy through chain segment movement, which is manifested as a certain flexibility. They can serve as a buffer for the charging and discharging process of positive or negative active materials during the cycle of battery cells, thereby improving cycle expansion and improving 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 K1, 1<K1<∞, T m2 ℃ represents the melting temperature of the ether polymer; optionally, 1<K1≤100; further optionally, 1<K1≤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 23Including substituted or unsubstituted C1-C5 alkylene;

[0032]

[0033] 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;

[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 entanglement state of the molecular chains 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 K2, 1<K2<∞, T m3 ℃ represents the melting temperature of the ester polymer; optionally, 1<K2≤100; further optionally, 1<K2≤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 35 including 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 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.

[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 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;

[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 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.

[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 an electrical device, comprising a battery as in the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] 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.

[0061] Figure 1 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0062] Figure 2 yes Figure 1 An exploded schematic diagram of an embodiment of a battery cell.

[0063] Figure 3 It is a schematic diagram of an embodiment of a battery module of the present application.

[0064] Figure 4 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0065] Figure 5 yes Figure 4 An exploded schematic diagram of an embodiment of a battery pack is shown.

[0066] Figure 6 It is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0067] The drawings are not necessarily drawn to scale.

[0068] The following are the descriptions of the reference numerals:

[0069] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module;

[0070] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0071] 53. Cover plate;

[0072] 6. Electrical equipment. DETAILED DESCRIPTION

[0073] Hereinafter, the battery and the electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0074] "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.

[0075] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0076] 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.

[0077] 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.

[0078] In the embodiments of the present application, the terms "plurality" and "multiple" refer to two or more.

[0079] 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.

[0080] 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.

[0081] The term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom or the like.

[0082] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D) or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

[0083] 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 substance, and the positive electrode active substance can provide active ions. The negative electrode sheet includes a negative electrode film layer containing a negative electrode active substance. 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 improve the energy density of the battery, it can be achieved by selecting a positive electrode active substance and / or a negative electrode active substance with a high energy density. The specific capacity of the positive electrode active substance and / or the negative electrode active substance that meets the high energy density requirement is usually higher.

[0084] During the charge and discharge cycle of the battery cell, the volume of the electrode assembly may change (such as expansion and deformation) due to the embedding or extraction of active ions from the active material, causing the electrolyte infiltrated in the electrode assembly to be continuously squeezed out. It may be difficult to reabsorb the squeezed electrolyte, which may easily lead to liquid shortage in the electrode assembly, resulting in poor wetting of the high specific capacity positive electrode active material and / or aggravated concentration polarization phenomenon, thereby deteriorating the cycle performance of the battery.

[0085] In view of the above problems, an embodiment of the present application proposes a battery cell, which includes an electrode plate, and the electrode plate includes an active material. The active material can provide a high energy density for the battery cell, for example ≥300Wh / Kg. A lyophilic polymer is arranged in the electrode plate, and the lyophilic polymer has a high affinity for the electrolyte, which can improve the affinity between the electrode plate and the electrolyte, and store the electrolyte on the surface of the active material particles of the electrode plate, thereby improving the liquid storage capacity of the electrode plate. The electrolyte has good wetting performance on the membrane layer, which can reduce concentration polarization phenomenon and improve the cycle performance of the battery.

[0086] Next, the technical solution of this application is described in detail.

[0087] Battery Cell

[0088] In a first aspect, an embodiment of the present application provides a battery cell.

[0089] The battery cell comprises an electrode plate, the electrode plate comprises a current collector and a membrane layer arranged on at least one side of the current collector, the membrane layer comprises an active material and a lyophilic polymer, wherein the energy density of the battery cell is ≥300Wh / Kg.

[0090] The electrode sheet may include at least one of a positive electrode sheet and a negative electrode sheet; for example, the electrode sheet includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active substance and a lyophilic polymer. For another example, the electrode sheet includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active substance and a lyophilic polymer. For another example, the electrode sheet includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active substance and a lyophilic polymer, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active substance and a lyophilic polymer.

[0091] Active materials such as positive electrode active materials and negative electrode active materials can contribute to the energy density of battery cells, but it is difficult for active materials to meet the high energy density of battery cells while taking into account the cycle performance of battery cells. In the embodiment of the present application, a lyophilic polymer is arranged in the film layer of the electrode plate. The lyophilic polymer can be evenly mixed with the active material particles when preparing the slurry to form a film layer. The lyophilic polymer has an affinity for the electrolyte and can improve the affinity between the electrode plate and the electrolyte. The lyophilic polymer is configured to coat the electrolyte and can form an effective liquid storage point on the surface of the active material particles, thereby improving the liquid storage capacity of the electrode plate. The wetting performance of the electrolyte on the film layer is improved, which can reduce the concentration polarization phenomenon and improve the cycle performance of the battery.

[0092] 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.

[0093] The energy density of the battery cell in the implementation manner 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 with a 1C constant current to 4.25V, then charged with a constant voltage to 0.05C, and left to stand for 30 minutes; it is discharged with a 1C discharge to 2.8V, and the discharge capacity D0 and platform voltage U0 are recorded; the mass M0 of the battery cell is weighed, and the energy density of the battery cell is D0*U0 / M0.

[0094] The energy density of the battery cell in the embodiment of the present application is relatively high, for example ≥300Wh / Kg, and can be selected from 300Wh / Kg to 500Wh / Kg, for example 300Wh / Kg, 305Wh / Kg, 310Wh / Kg, 315Wh / Kg, 320Wh / Kg, 325Wh / Kg, 330Wh / Kg, 335Wh / Kg, 340Wh / Kg, 345Wh / Kg, 350Wh / Kg, 355Wh / Kg, 360Wh / Kg, 365Wh / Kg, 370Wh / Kg, 375Wh / Kg, 380Wh / Kg, 385Wh / Kg, 390Wh / Kg, Wh / Kg, 395Wh / Kg, 400Wh / Kg, 405Wh / Kg, 410Wh / Kg, 415Wh / Kg, 420Wh / Kg, 425Wh / Kg, 430Wh / Kg, 435Wh / Kg, 440Wh / Kg, 445Wh / Kg, 450Wh / Kg, 455Wh / Kg, 460Wh / Kg, 465Wh / Kg, 470Wh / Kg, 475Wh / Kg, 480Wh / Kg, 485Wh / Kg, 490Wh / Kg, 495Wh / Kg, 500Wh / Kg or a range consisting of any two of the above values.

[0095] [Positive electrode]

[0096] In some embodiments, the electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material and a lyophilic polymer. In this case, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material and a lyophilic polymer. Alternatively, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material, that is, does not contain a lyophilic polymer.

[0097] In other embodiments, the electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material and a lyophilic polymer. In this case, the positive electrode film layer may include a positive electrode active material, that is, does not include a lyophilic polymer.

[0098] Further research has found that when both the positive electrode film layer and the negative electrode film layer include lyophilic polymers, the lyophilic polymers can improve the wetting performance of the electrolyte on the positive electrode plate, and can also improve the wetting performance of the electrolyte on the negative electrode plate, thereby effectively improving the cycle performance of the battery cell. Specifically, the lyophilic polymer can not only increase the wetting rate of the positive electrode film layer, improve the polarization effect and the interfacial side reactions of the positive electrode film layer, thereby improving the cycle life, but also reduce storage gas production. The lyophilic polymer can not only increase the wetting rate of the negative electrode film layer, improve the polarization effect and the interfacial side reactions of the negative electrode film layer, but also buffer the volume expansion of the negative electrode active material to a certain extent, improve the cycle expansion, and improve the cycle performance.

[0099] In some embodiments, the positive electrode active material includes a molecular formula of Li x Ni a Co b M (1-a-b) O2 compounds and modified compounds thereof, wherein 0.60≤x≤1.20, 0.85≤a<1.00, 0<b≤0.10, and a+b<1.00, and M includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, La and Nb.

[0100] The specific capacity of the positive electrode active material is relatively high, especially when 0.90≤a<1.0, the specific capacity of the positive electrode active material is further improved.

[0101] Illustratively, x can be 0.60, 0.62, 0.65, 0.70, 0.72, 0.75, 0.78, 0.80, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.05, 1.10, 1.12, 1.15, 1.18, 1.20, or a range consisting of any two of the above values.

[0102] Illustratively, a may be 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or a range consisting of any two of the foregoing values.

[0103] Illustratively, b may be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, or a range consisting of any two of the foregoing values.

[0104] Illustratively, a+b may be 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or a range consisting of any two of the above values.

[0105] Exemplarily, the positive electrode active material includes a LiNi 0.85 Co 0.10 M 0.05 O2、LiNi 0.92 Co 0.04 M 0.04 O2、LiNi 0.92 Co 0.05 M 0.03 O2、LiNi 0.92 Co 0.06 M 0.02 O2、LiNi 0.93 Co 0.03 M 0.04 O2 and LiNi 0.93 Co 0.025 M 0.045 At least one compound in O2.

[0106] 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.

[0107] 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.

[0108] In the embodiments of the present application, the modified compound may be modified by doping or coating. The doping modification may be the addition of doping elements such as transition metals to the compound, and the coating modification may be the surface coating with materials such as carbon, that is, forming a carbon coating layer on the outer surface of the particle.

[0109] In some embodiments, the positive active material may include single crystal particles and polycrystalline particles.

[0110] A crystal is a solid composed of atoms or groups of atoms arranged regularly and repeatedly in three-dimensional space. The atoms in the entire crystal of a single crystal particle are arranged in the same orientation, and the entire crystal of a polycrystalline particle is composed of multiple single crystals with different orientations. Single crystal particles can improve the compaction density of the positive electrode sheet, while polycrystalline particles can make the positive electrode sheet show better power performance. At the same time, adding single crystal particles and polycrystalline particles can make the positive electrode sheet take into account both compaction density and power performance.

[0111] In some embodiments, the volume average particle size Dv50 of the single crystal particles is smaller than the volume average particle size Dv50 of the polycrystalline particles. By combining the different particle sizes of the single crystal particles and the polycrystalline particles, the compaction density of the positive electrode film layer can be increased, which is conducive to further improving the energy density of the battery cell.

[0112] In some embodiments, the volume average particle size Dv50 of the single crystal particles is 2 μm to 5 μm, such as 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range consisting of any two of the above values.

[0113] In some embodiments, the volume average particle size Dv50 of the polycrystalline particles is 5 μm to 10 μm, for example 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or a range consisting of any two of the above values.

[0114] In the embodiment of the present application, the volume average particle size Dv50 of the particles has a well-known meaning in the art, and the volume average particle size Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution. It can be detected by using equipment and methods well-known in the art. After the fresh battery cell is fully discharged to 0% state of charge SOC, the positive electrode sheet is disassembled, the positive electrode current collector is removed to retain the positive electrode film layer, the positive electrode film layer is immersed in N-methylpyrrolidone NMP, the binder in the positive electrode film layer is washed out, and the positive electrode active material is retained. After the positive electrode active material is dried, the volume average particle size Dv50 of the particles is tested by Mastersizer2000E laser particle size analyzer according to the test standard GB / T 19077-2016. In the embodiment of the present application, the fresh battery cell can be a battery cell that has just left the factory (not charged and discharged for use after formation), or a battery cell that is assembled on an electrical device and has been used for less than 10 cycles.

[0115] In some embodiments, based on the total mass of the positive electrode active material, the mass content of the single crystal particles is 10% to 30%. When the mass content of the single crystal particles is within the above range, it can be further matched with polycrystalline particles to increase the compaction density of the positive electrode film layer, thereby increasing the energy density of the battery cell. Exemplarily, the mass content of the single crystal particles can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or a range consisting of any two of the above values.

[0116] In some embodiments, based on the total mass of the positive electrode active material, the mass content of the polycrystalline particles is 70% to 90%. When the mass content of the polycrystalline particles is within the above range, it can be further matched with the single crystal particles to increase the compaction density of the positive electrode film layer, thereby increasing the energy density of the battery cell. Exemplarily, the mass content of the polycrystalline particles can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90% or a range consisting of any two of the above values.

[0117] The mass content of single crystal particles and the mass content of polycrystalline particles can be observed using a scanning electron microscope (SEM), and the distribution ratio of single crystal particles and polycrystalline particles can be quantitatively analyzed to obtain the mass content of each particle.

[0118] In some embodiments, the compaction density of the positive electrode film layer is ≥3.6 g / cm 3 , optional 3.6g / cm 3 Up to 3.8g / cm 3 , for example 3.6 g / cm 3 、3.61g / cm 3 、3.62g / cm 3 、3.65g / cm 3 、3.68g / cm 3 、3.70g / cm 3 、3.72g / cm 3 、3.75g / cm 3 、3.78g / cm 3 、3.80g / cm 3 Or a range consisting of any two of the above values. When the compaction density of the positive electrode film layer is within the above range, the energy density of the battery cell can be significantly improved.

[0119] In the embodiments of the present application, the compaction density of the positive electrode film layer has a meaning well known in the art and can be tested using equipment and methods well known in the art. For example, take a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punch it into small discs with an area of ​​S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive electrode film layer of the weighed positive electrode sheet, weigh the weight of the positive electrode collector, record it as M0, and measure its thickness H0. The surface density of the positive electrode film layer = (the weight of the positive electrode sheet M1-the weight of the positive electrode collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode sheet H1-the thickness of the positive electrode collector H0, and the compaction density of the positive electrode film layer = the surface density of the positive electrode film layer / the thickness of the positive electrode film layer.

[0120] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the positive electrode active material is 80% to 99.9%, and optionally 92% to 99%. When the mass content of the positive electrode active material is within the above range, it is beneficial to improve the energy density of the battery cell.

[0121] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the lyophilic polymer is ≤5%; it can be optionally 0.05% to 5%. 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, improve the liquid storage capacity of the positive electrode film 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 of the battery cell.

[0122] 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.

[0123] In some embodiments, the coating weight of the lyophilic polymer is 0.5 mg / 1540.25 mm 2 Up to 5mg / 1540.25mm 2 , for example 0.5mg / 1540.25mm 2 、0.6mg / 1540.25mm 2 、0.7mg / 1540.25mm 2 , 0.8mg / 1540.25mm 2 、0.9mg / 1540.25mm 2 、1.0mg / 1540.25mm 2 、1.1mg / 1540.25mm 2 , 1.2mg / 1540.25mm 2 、1.3mg / 1540.25mm 2 、1.4mg / 1540.25mm 2 , 1.5mg / 1540.25mm 2 、1.6mg / 1540.25mm 2 、1.7mg / 1540.25mm 2 、1.8mg / 1540.25mm 2 、1.9mg / 1540.25mm 2 、2.0mg / 1540.25mm 2 , 2.1mg / 1540.25mm 2 , 2.2mg / 1540.25mm 2 , 2.3mg / 1540.25mm 2 , 2.4mg / 1540.25mm 2 , 2.5mg / 1540.25mm 2 , 2.6mg / 1540.25mm 2 , 2.7mg / 1540.25mm 2 , 2.8mg / 1540.25mm 2 、2.9mg / 1540.25mm 2 、3.0mg / 1540.25mm 2 、3.1mg / 1540.25mm 2 、3.2mg / 1540.25mm 2 、3.3mg / 1540.25mm 2 、3.4mg / 1540.25mm 2 、3.5mg / 1540.25mm 2 、3.6mg / 1540.25mm2 、3.7mg / 1540.25mm 2 、3.8mg / 1540.25mm 2 、3.9mg / 1540.25mm 2 4.0mg / 1540.25mm 2 4.1mg / 1540.25mm 2 4.2mg / 1540.25mm 2 4.3mg / 1540.25mm 2 4.4mg / 1540.25mm 2 4.5mg / 1540.25mm 2 4.6mg / 1540.25mm 2 4.7mg / 1540.25mm 2 4.8mg / 1540.25mm 2 , 4.9mg / 1540.25mm 2 、5.0mg / 1540.25mm 2 Or it is a range consisting of any two of the above values. The coating weight of the lyophilic polymer is the coating weight in the positive electrode film layer on a single side of the positive electrode sheet.

[0124] 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.

[0125] 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.

[0126] [Fluorinated polymers]

[0127] In some embodiments, the lyophilic polymer may include a fluorinated polymer.

[0128] In some embodiments, the fluorinated polymer has a crystallinity of X as measured by differential scanning calorimetry. c1 %,0<X c1 ≤28.

[0129] In some embodiments, the melting temperature of the fluorinated polymer is T m1 ℃, 0<T m1 ≤130.

[0130] In some embodiments, the glass transition temperature of the fluorinated polymer is T g1 ℃, -30≤T g1 ≤40.

[0131] 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.

[0132] Therefore, fluorinated polymers have relatively low crystallinity, melting temperature or glass transition temperature. Fluorinated polymers have certain activity above the glass transition temperature. Under the action of external force, they can buffer external energy through chain segment movement, which is manifested as a certain flexibility. They can serve as a buffer for the charging and discharging process of positive or negative active materials during the cycle of battery cells, thereby improving cycle expansion and improving cycle performance.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AI) to the compounds represented by formula (AII),

[0137]

[0138] 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 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AIII),

[0145]

[0146] In formula (AIII), R 15 Includes single bonds, substituted or unsubstituted alkyl groups; when substituted, substituents include fluorine atoms.

[0147] 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.

[0148] Optionally, R 15 This includes single bonds, substituted or unsubstituted C1-C3 alkyl groups.

[0149] In some embodiments, p is selected from a positive integer of 1 to 3, such as 1, 2 or 3.

[0150] 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.

[0151] 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),

[0152]

[0153] 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),

[0154]

[0155] 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),

[0156]

[0157] 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).

[0158] 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).

[0159] 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.

[0160] 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.

[0161] In some embodiments, the molecular weight of the lyophilic polymer is 2×10 5 g / mol to 1.2×10 6 g / mol.

[0162] 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.

[0163] [Ether polymer]

[0164] In some embodiments, the lyophilic polymer comprises an ether polymer.

[0165] 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 K1, 1<K1<∞, T m2 ℃ represents the melting temperature of ether polymer.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] In some embodiments, 1<K1≤100; optionally, 1<K1≤10. For example, K1 may 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.

[0171] 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. They can serve as a buffer for the charge and discharge process of the positive active material or the negative active material during the battery monomer cycle, thereby improving the cycle expansion and improving the cycle performance.

[0172] In some embodiments, the ether polymer includes a compound represented by formula (BI),

[0173]

[0174] 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.

[0175] 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.

[0176] 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.

[0177] Optionally, R 23 Includes single bonds, substituted or unsubstituted C1-C10 methylene groups.

[0178] Optionally, R 23 Includes single bonds, substituted or unsubstituted C1-C5 methylene.

[0179] Illustratively, the ether polymer includes at least one of the compounds represented by formula (BI-1) to the compounds represented by formula (BI-8),

[0180]

[0181] In some embodiments, the ether polymer includes a compound represented by formula (BII),

[0182]

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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),

[0187]

[0188] 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.).

[0189] 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.

[0190] 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.

[0191] Optionally, the polymerization degree n of the ether polymer is selected from a positive integer ranging from 3,000 to 18,000.

[0192] 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.

[0193] [Ester polymer]

[0194] In some embodiments, the lyophilic polymer comprises an ester polymer.

[0195] 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 K2, 1<K1<∞, T m3 ℃ represents the melting temperature of ester polymer.

[0196] 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.

[0197] In some embodiments, 1<K2≤100; optionally, 1<K2≤10. For example, K2 may 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.

[0198] In some embodiments, the glass transition temperature of the ester polymer is T g3 ℃, -20≤T g3 ≤35; For example, 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. It can serve as a buffer for the charge and discharge process of the positive active material or the negative active material during the battery monomer cycle, thereby improving the cycle expansion and improving the cycle performance.

[0199] In some embodiments, the ester polymer includes a compound represented by formula (CI),

[0200]

[0201] In formula (CI), R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted alkyl group; R34 It includes a substituted or unsubstituted alkyl group, or a substituted or unsubstituted hydroxyalkyl group.

[0202] Optionally, R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C10 alkyl group.

[0203] Optionally, R 31 , R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group.

[0204] In some embodiments, R 34 Includes substituted or unsubstituted C1-C10 alkyl groups, or substituted or unsubstituted C1-C10 hydroxyalkyl groups.

[0205] In some embodiments, R 34 It includes substituted or unsubstituted C1-C8 alkyl groups, or substituted or unsubstituted C1-C8 hydroxyalkyl groups.

[0206] In some embodiments, R 31 This includes a hydrogen atom, or a substituted or unsubstituted methyl group.

[0207] In some embodiments, R 32 and R 33 Each independently includes a hydrogen atom.

[0208] Exemplarily, the ester polymer includes at least one of the compounds represented by formula (CI-1) to the compounds represented by formula (CI-15),

[0209]

[0210]

[0211] In some embodiments, the ester polymer includes a compound represented by formula (CII),

[0212]

[0213] In formula (CII), R 35 Substituted or unsubstituted methylene groups are included.

[0214] Optionally, R 35 This includes substituted or unsubstituted C1-C10 methylene groups.

[0215] Optionally, R 35 This includes substituted or unsubstituted C2-C6 methylene groups.

[0216] Optionally, R 35 This includes substituted or unsubstituted C2-C4 methylene groups.

[0217] Illustratively, the ester polymer includes at least one of the compounds represented by formula (CII-1) to the compounds represented by formula (CII-5),

[0218]

[0219] In some embodiments, the ester polymer includes a compound represented by formula (CIII),

[0220]

[0221] 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;

[0222] Optionally, R 36 , R 37 and R 38 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C4 alkyl group.

[0223] Illustratively, the ester polymer includes at least one of the compounds represented by formula (CIII-1) to the compounds represented by formula (CIII-5),

[0224]

[0225]

[0226] 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 (such as olefin compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid and other compounds, etc.).

[0227] 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.

[0228] 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.

[0229] In some embodiments, the degree of polymerization n of the ester polymer is a positive integer selected from 1,000 to 15,000.

[0230] In some embodiments, the molecular weight of the lyophilic polymer is 2×10 5 g / mol to 1.2×10 6 g / mol.

[0231] 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.

[0232] [Aldehyde and Ketone Polymers]

[0233] In some embodiments, the lyophilic polymer comprises an aldehyde-ketone polymer.

[0234] 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 K3, 0.8≤K3<∞, T m4 ℃ represents the melting temperature of aldehyde-ketone polymers.

[0235] 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.

[0236] In some embodiments, 0.8≤K3≤100; alternatively, 0.8≤K3≤10. For example, K3 may 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.

[0237] 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. It can serve as a buffer for the charge and discharge process of the positive electrode active material or the negative electrode active material during the battery monomer cycle, thereby improving the cycle expansion and improving the cycle performance.

[0238] In some embodiments, the aldehyde-ketone polymer comprises a compound represented by formula (DI),

[0239]

[0240] 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.

[0241] Optionally, R 41 Includes single bonds, substituted or unsubstituted C1-C2 methylene.

[0242] Optionally, R 42 This includes a hydrogen atom, and a substituted or unsubstituted C1-C3 alkyl group.

[0243] 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.

[0244] 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),

[0245]

[0246] Exemplarily, the aldehyde-ketone polymer includes a compound represented by formula (DII),

[0247]

[0248] 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 an integer from 0 to 5, and at least one of r and s is selected from a positive integer.

[0249] 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.

[0250] 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),

[0251]

[0252] 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.).

[0253] 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.

[0254] 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.

[0255] Optionally, the degree of polymerization n of the aldehyde-ketone polymer is selected from a positive integer ranging from 500 to 10,000.

[0256] In some embodiments, the molecular weight of the aldehyde-ketone polymer is 1.2×10 5 g / mol to 1.2×10 6g / mol.

[0257] For example, the molecular weight of the aldehyde-ketone polymer may be 1.2×10 5 g / mol, 2×10 5 g / 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.

[0258] The relevant parameters of the lyophilic polymer according to the embodiment of the present application can be detected by the following method:

[0259] 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.

[0260] The structure of the lyophilic polymer of 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 nuclear magnetic resonance instrument, the test temperature is 20° C., TMS is used as the internal standard, CDCl3 is used as the solvent, and the proton resonance frequency is 400 MHz.

[0261] The polymer monomer type of the lyophilic polymer of the embodiment of the present application (especially suitable for monomers that account for a relatively small proportion in the polymer) can be tested by pyrolysis-gas chromatography-mass spectrometry, and the specific test steps are as follows: accurately weigh 0.5 mg of the sample and put it into the sample cup, fix it on the injection rod, and then put it into the pyrolyzer installed near the GC (gas chromatography) injection port. After the temperature of the pyrolyzer reaches the set temperature, press the injection button, and the sample cup quickly falls into the core of the pyrolysis furnace by free fall. In the inert gas N2 atmosphere, the volatile components are instantly vaporized and carried into the gas chromatography column by the carrier gas for separation. Finally, they are detected by a flame ionization detector FID or a mass spectrometer MS to obtain a gas chromatogram or a total ion flow diagram.

[0262] 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.

[0263] 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.

[0264] 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).

[0265] 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%.

[0266] 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.

[0267] 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.

[0268] [Negative electrode]

[0269] 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 and a lyophilic polymer.

[0270] In some embodiments, the negative electrode active material includes a silicon-based material. The silicon-based material has a high theoretical capacity and can effectively improve the energy density of the battery cell.

[0271] In some embodiments, based on the total mass of the negative electrode active material, the mass content of the silicon-based material is ≥5%, and can be optionally 15% to 50%. When the mass content of the silicon-based material is within the above range, the energy density of the battery cell can be further improved.

[0272] Exemplarily, the mass content of the silicon-based material can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or a range consisting of any two of the above values.

[0273] In some embodiments, the silicon-based material may include at least one of elemental silicon, silicon oxide SiOx (0<x≤2), a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy material.

[0274] Elemental silicon can be made into nano-silicon, which can effectively alleviate the particle pulverization caused by volume expansion, shorten the diffusion distance of lithium ions, and improve the cycle performance of the negative electrode.

[0275] In silicon-carbon composite materials, silicon particles can be deposited in the porous structure of carbon particles, so that silicon and carbon are composited into one. Carbon can buffer the volume expansion of silicon and improve the cycle performance of the negative electrode.

[0276] Silicon alloy materials are a composite of silicon and metal elements, which can relieve the internal stress of the material during the process of lithium insertion and extraction, and improve the material's conductivity and other properties, thereby improving the comprehensive electrochemical performance of the negative electrode. The alloy elements can be titanium, copper, silver, tin, etc. For example, nano-silicon particles are used as cores, and metal is used as shells to cover at least part of the surface of nano-silicon particles.

[0277] In some embodiments, the negative electrode active material may further include a carbon-based material, and the carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon and hard carbon. The stability of the carbon-based material is relatively high, and the use of the carbon-based material in combination with the silicon-based material can improve the cycle stability and energy density of the negative electrode sheet.

[0278] In some embodiments, based on the total mass of the negative electrode active material, the mass content of the carbon-based material is ≤95%; it can be optionally 50% to 85%. For example, the mass content of the carbon-based material can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95% or a range consisting of any two of the above values.

[0279] In some embodiments, the negative electrode active material may further include at least one of a tin-based material and lithium titanate.

[0280] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the negative electrode active material is 80% to 99.9%, and optionally 90% to 99%. When the mass content of the negative electrode active material is within the above range, it is beneficial to improve the energy density of the battery cell.

[0281] In some embodiments, the compaction density of the negative electrode film layer is ≥1.5 g / cm 3 , optional 1.5g / cm 3 Up to 2.0g / cm 3 , for example 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 Or a range consisting of any two of the above values. When the compaction density of the negative electrode film layer is within the above range, the energy density of the battery cell can be significantly improved.

[0282] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the lyophilic polymer is ≤5%; it can be optionally 0.05% to 5%. 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 negative electrode active material particles, improve the liquid storage capacity of the negative electrode film layer, and improve the wettability of the electrolyte to the negative electrode active material in the negative electrode film layer, thereby facilitating the improvement of the cycle performance of the battery cell.

[0283] 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.

[0284] In some embodiments, the coating weight of the lyophilic polymer is 0.5 mg / 1540.25 mm 2 Up to 5mg / 1540.25mm 2 , for example 0.5mg / 1540.25mm 2 、0.6mg / 1540.25mm 2 、0.7mg / 1540.25mm 2 , 0.8mg / 1540.25mm 2 、0.9mg / 1540.25mm 2 、1.0mg / 1540.25mm 2 、1.1mg / 1540.25mm 2 , 1.2mg / 1540.25mm 2 、1.3mg / 1540.25mm 2 、1.4mg / 1540.25mm 2、1.5mg / 1540.25mm 2 、1.6mg / 1540.25mm 2 、1.7mg / 1540.25mm 2 、1.8mg / 1540.25mm 2 、1.9mg / 1540.25mm 2 、2.0mg / 1540.25mm 2 、2.1mg / 1540.25mm 2 、2.2mg / 1540.25mm 2 、2.3mg / 1540.25mm 2 、2.4mg / 1540.25mm 2 、2.5mg / 1540.25mm 2 、2.6mg / 1540.25mm 2 、2.7mg / 1540.25mm 2 、2.8mg / 1540.25mm 2 、2.9mg / 1540.25mm 2 、3.0mg / 1540.25mm 2 、3.1mg / 1540.25mm 2 、3.2mg / 1540.25mm 2 、3.3mg / 1540.25mm 2 、3.4mg / 1540.25mm 2 、3.5mg / 1540.25mm 2 、3.6mg / 1540.25mm 2 、3.7mg / 1540.25mm 2 、3.8mg / 1540.25mm 2 、3.9mg / 1540.25mm 2 、4.0mg / 1540.25mm 2 、4.1mg / 1540.25mm 2 、4.2mg / 1540.25mm 2 、4.3mg / 1540.25mm 2 、4.4mg / 1540.25mm 2 、4.5mg / 1540.25mm 2 、4.6mg / 1540.25mm 2 、4.7mg / 1540.25mm 2 、4.8mg / 1540.25mm 2, 4.9mg / 1540.25mm 2 、5.0mg / 1540.25mm 2 Or it is a range consisting of any two of the above values. The coating weight of the lyophilic polymer is the coating weight in the negative electrode film layer on a single side of the negative electrode sheet.

[0285] 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 an effective liquid storage point can be formed on the surface of the active material to improve the liquid storage capacity of the electrode plate.

[0286] The specific selection principles and types of fluorinated polymers, ether polymers, ester polymers, and aldehyde-ketone polymers are as described in the lyophilic polymer in the positive electrode film layer and will not be repeated here.

[0287] 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.

[0288] 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%.

[0289] 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%.

[0290] 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%.

[0291] 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).

[0292] 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, lyophilic polymer, 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 thereto. 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.

[0293] 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.

[0294] [Isolation film]

[0295] In some embodiments, the battery cell includes a separator.

[0296] In some embodiments, the isolation film includes a substrate.

[0297] In some embodiments, a separator includes a substrate and a coating disposed on at least one surface of the substrate.

[0298] 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.

[0299] 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.

[0300] 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.

[0301] 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.

[0302] Optionally, inorganic particles having a dielectric constant of 5 or more include boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0<m<1, 0<n<1), Pb(Mg3Nb 2 / 3 )O3-PbTiO3 (abbreviated as PMN-PT), and at least one of their respective modified inorganic particles. Optionally, the modification method of each inorganic particle may be chemical modification and / or physical modification. Chemical modification methods include coupling agent modification (for example, using silane coupling agent, titanate coupling agent, etc.), surfactant modification, polymer grafting modification, etc. Physical modification methods may be mechanical force dispersion, ultrasonic dispersion, high energy treatment, etc. The modification treatment can reduce the agglomeration of inorganic particles, thereby enabling them to form a more stable and uniform spatial network structure with nanocellulose; in addition, by selecting coupling agents, surfactants or polymer-modified inorganic particles with specific functional groups, it is also helpful to improve the wetting properties of the coating to the electrolyte and improve the bonding strength between the coating and the substrate.

[0303] Optionally, inorganic particles having ion conductivity but not storing ions include Li3PO4, lithium titanium phosphate Li x1 Ti y1 (PO4)3, Lithium Aluminum Titanate Phosphate Li x2 Al y2 Ti z1 (PO4)3, (LiAlTiP) x3 O y3 Type glass, lanthanum titanate lithium Li x4 La y4 TiO3, Lithium Germanium Phosphate Thiophosphate x5 Gey5 P z2 S w 、Lithium Nitride Li x6 N y6 、SiS2 glass Li x7 Si y7 S z3 and P2S5 glass Li x8 P y8 S 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.

[0304] 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.

[0305] 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).

[0306] 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.

[0307] Optionally, the content of binder in the coating is <30%, based on the mass of the coating.

[0308] [Electrolyte]

[0309] In some embodiments, the battery cells include an electrolyte.

[0310] 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.

[0311] 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.

[0312] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0313] 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).

[0314] 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.

[0315] 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.

[0316] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0317] 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).

[0318] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0319] In some embodiments, Figure 1 and Figure 2 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0320] 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.

[0321] 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.

[0322] Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0323] 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.

[0324] 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.

[0325] Both the battery module 4 and the battery pack can be used as specific examples of batteries in the embodiments of the present application.

[0326] Figure 4 and Figure 5 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0327] Electrical devices

[0328] In the second 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, and can also be used 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.

[0329] The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements. Figure 6 Schematic diagram of an electric device as an example. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack 1 or a battery module can be used. As another example, the electric device can be a mobile phone, a tablet computer, a laptop computer, etc. The electric device is usually required to be light and thin, and a battery cell can be used as a power source.

[0330] Example

[0331] 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.

[0332] Example 1 Preparation of lithium ion battery

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

[0334] The lyophilic polymer, positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are added to N-methylpyrrolidone (NMP) in a mass ratio of 0.2:97.8:1:1 and mixed to form a positive electrode slurry. 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 at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) is 48%.

[0335] (2) Preparation of negative electrode sheet:

[0336] The lyophilic polymer, negative electrode active material, conductive agent carbon black, adhesive styrene butadiene rubber (SBR), and thickener sodium hydroxymethyl cellulose (CMC) were added to deionized water in a mass ratio of 2:94.5:0.5:2:1 and mixed evenly to prepare negative electrode slurry. The negative electrode slurry was coated on the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut, and striped, and then dried at 120°C under vacuum conditions for 12 hours to prepare negative electrode sheets.

[0337] (3) Preparation of electrolyte:

[0338] The electrolyte includes an organic solvent and a lithium salt. The organic solvent includes ethylene carbonate EC and ethyl methyl carbonate (EMC) (volume ratio 3:7). The lithium salt includes 1 mol / L LiPF6.

[0339] (4) Preparation of lithium-ion batteries:

[0340] 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.

[0341] Example 2 to Example 6

[0342] 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.

[0343] Example 7 to Example 16

[0344] 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 16.

[0345] Example 17 to Example 20

[0346] 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 17 to 20.

[0347] Example 21 to Example 23

[0348] A lithium-ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that the grain structure of the positive electrode active material was adjusted in Examples 21 to 23.

[0349] Comparative Example 1

[0350] 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. The electrode preparation process is as follows:

[0351] (1) Preparation of positive electrode sheet:

[0352] The positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in a mass ratio of 97.5:2:0.5 and mixed to form a positive electrode slurry. The positive electrode slurry was coated on the current collector aluminum foil and dried at 85°C and then cold pressed. After trimming, cutting, and striping, it was dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet. The crystallinity of the binder polyvinylidene fluoride (PVDF) was 48%.

[0353] (2) Preparation of negative electrode sheet:

[0354] The negative electrode active material, conductive agent carbon black, adhesive styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were added to deionized water in a weight ratio of 94.9:2:0.5:2.6 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.

[0355] Comparative Example 2

[0356] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the type of polymer was adjusted in Comparative Example 2.

[0357] Test Section

[0358] 1. Lithium-ion battery capacity retention test

[0359] The lithium-ion battery prepared in the embodiment and comparative example is charged to 4.25V at 1C constant current in a 45°C environment, then charged to 0.05C at 4.25V constant voltage, left for 5 minutes, and then discharged to 2.8V at 1C. 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. The battery capacity retention rate after each cycle is Pn = Cn / C0*100%. The 1200 point values ​​of P1, P2...P1200 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.

[0360] In the test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 1200th cycle corresponds to n=1200. For example, the battery capacity retention rate data corresponding to Example 1 in Table 1 is the data measured after 1200 cycles under the above test conditions, that is, the value of P1200. The test process of Comparative Example 1 and other embodiments is the same as above.

[0361] 2. Lithium-ion battery DC impedance test

[0362] The lithium-ion battery prepared in the embodiment and comparative example is charged at 45°C at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V to a current of 0.05C. After standing for 5 minutes, the voltage V1 is recorded. Then, it is discharged at 1 / 3C for 30s, and the voltage V2 is recorded. Then (V2-V1) / 1 / 3C is used to obtain the internal resistance DCR1 of the battery after the first cycle. Repeat the above steps for the same battery, and simultaneously record the internal resistance DCRn (n=1, 2, 3...1200) of the battery after the nth cycle. The 1200 point values ​​of DCR1, DCR2, DCR3...DCR1200 are used as the ordinate, and the corresponding number of cycles is used as the abscissa, to obtain the curve of the battery discharge DCIR and the number of cycles corresponding to the polymers in the embodiment and comparative example.

[0363] In this test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 1200th cycle corresponds to n=1200. For example, the battery internal resistance increase ratio of Example 1 in Table 1 = (DCRn-DCR1) / DCR1*100%, and the test process of Comparative Example 1 and other embodiments is the same as above. The data in Table 1 are measured after 1200 cycles under the above test conditions.

[0364] Test Results

[0365] The test results are shown in Tables 1 to 4.

[0366] Table 1

[0367]

[0368] 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%.

[0369] Table 2

[0370]

[0371]

[0372] Table 3

[0373]

[0374]

[0375] In Table 2 and Table 3, 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.

[0376] The amount of the lyophilic polymer added to the positive electrode plate is 0%, indicating that no lyophilic polymer is added to the positive electrode film layer.

[0377] The lyophilic polymer content of the negative electrode plate is 2%, which means that the mass content of the lyophilic polymer is 2% based on the total mass of the negative electrode film layer.

[0378] The amount of the lyophilic polymer added to the negative electrode plate is 0%, indicating that no lyophilic polymer is added to the negative electrode film layer.

[0379] The negative electrode active material includes 88% artificial graphite+12% SiOx, which means that based on the total mass of the negative electrode active material, the mass content of artificial graphite is 88%, and the mass content of silicon oxide SiOx (0<x≤2) is 12%.

[0380] Table 4

[0381]

[0382] It can be seen from Table 4 that the positive electrode plate and the negative electrode plate of Comparative Example 1 do not have a lyophilic polymer added. During the cycle of the lithium-ion battery, due to the volume change of the lithium-ion battery, the electrolyte in the electrode assembly may be squeezed out, causing a liquid shortage problem, thereby causing poor wetting of the electrode plate and deteriorating the cycle performance of the lithium-ion battery.

[0383] Although a polymer is added to the electrode in Comparative Example 2, the polymer has poor lyophilicity, which not only has low liquid retention efficiency, but also has high impedance that deteriorates the battery kinetic performance.

[0384] The embodiment of the present application adds a lyophilic polymer to at least one of the positive electrode plate and the negative electrode plate. The lyophilic polymer has a strong affinity with the electrolyte and can store the electrolyte on the surface of the active material particles of the electrode plate, thereby improving the liquid storage capacity of the electrode plate. The electrolyte has good wetting performance on the membrane layer, which can reduce concentration polarization and improve the cycle performance of the battery.

[0385] 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 battery, comprising an electrode plate, wherein the electrode plate comprises a current collector and a film layer disposed on at least one side of the current collector, wherein the film layer comprises an active material and a lyophilic polymer, in, The energy density of the battery is ≥300Wh / Kg.

2. The battery according to claim 1, wherein The energy density of the battery is 300Wh / Kg to 500Wh / Kg.

3. The battery according to claim 1 or 2, wherein: The electrode plate includes a positive electrode plate, and the active material in the positive electrode plate includes a molecular formula of Li x Ni a Co b M (1-a-b) O2 compounds and modified compounds thereof, wherein 0.60≤x≤1.20, 0.85≤a<1.00, 0<b≤0.10, and a+b<1.00, and M includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, La and Nb; Optionally, 0.90≤a<1.0; Further optionally, the active material in the positive electrode plate includes a molecular formula of LiNi 0.85 Co 0.10 M 0.05 O2、LiNi 0.92 Co 0.04 M 0.04 O2、LiNi 0.92 Co 0.05 M 0.03 O2、LiNi 0.92 Co 0.06 M 0.02 O2、LiNi 0.93 Co 0.03 M 0.04 O2 and LiNi 0.93 Co 0.025 M 0.045 At least one compound in O2.

4. The battery according to claim 3, wherein The active material in the positive electrode plate includes single crystal particles and polycrystalline particles, and the volume average particle size Dv50 of the single crystal particles is smaller than the volume average particle size Dv50 of the polycrystalline particles; Optionally, The volume average particle size Dv50 of the single crystal particles is 2 μm to 5 μm; Optionally, The volume average particle size Dv50 of the polycrystalline particles is 5 μm to 10 μm; Optionally, Based on the total mass of active materials in the positive electrode sheet, the mass content of the single crystal particles is 10% to 30%.

5. The battery according to any one of claims 3 to 4, wherein The compaction density of the film layer in the positive electrode sheet is ≥3.6g / cm 3 , optional 3.6g / cm 3 Up to 3.8g / cm 3 .

6. The battery according to any one of claims 1 to 5, wherein The electrode plate includes a negative electrode plate, and the active material in the negative electrode plate includes at least a silicon-based material; Optionally, the silicon-based material includes at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material; Optionally, based on the total mass of the active material in the negative electrode plate, the mass content of the silicon-based material is ≥5%; optionally, 15% to 50%; Optionally, the compaction density of the negative electrode film layer is ≥1.5 g / cm 3 , optional 1.5g / cm 3 Up to 2.0g / cm 3 .

7. The battery according to any one of claims 1 to 6, wherein Based on the total mass of the film layer, the mass content of the lyophilic polymer is ≤5%; optionally 0.05% to 5%; and / or The coating weight of the lyophilic polymer is 0.5 mg / 1540.25 mm 2 Up to 5mg / 1540.25mm 2 .

8. The battery 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 battery 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 battery 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 battery 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 battery 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. An electrical device comprising the battery according to any one of claims 1 to 12.

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