Battery and electric device

Abstract

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

Description

Batteries and electrical devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311460053.7, filed on November 03, 2023, entitled “Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] Batteries have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes and power tools, etc.

[0005] As battery applications become increasingly widespread, the requirements for battery performance are becoming increasingly stringent. However, it is difficult for batteries to achieve both high energy density and high cycle performance.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its object is to provide a battery and an electric device.

[0008] In a first aspect, the present application proposes 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.

[0009] Among them, the energy density of the battery is ≥300Wh / Kg.

[0010] Therefore, the active material in the embodiment of the present application 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 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.

[0011] In some embodiments, the energy density of the battery is from 300 Wh / Kg to 500 Wh / Kg.

[0012] 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 Lix 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-mentioned positive electrode active material is relatively high, which significantly improves the energy density of the battery.

[0013] In some embodiments, the active material in the positive electrode plate includes single-crystal particles and polycrystalline particles. 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; and optionally, the volume average particle size Dv50 of the polycrystalline particles is 5μm to 10μm. By combining single-crystal particles with polycrystalline particles of different particle sizes, the compaction density of the positive electrode film layer can be increased, which helps further improve the energy density of the battery cell.

[0014] In some embodiments, the mass content of single crystal particles is 10% to 30% based on the total mass of the active material in the positive electrode sheet. When the mass content of single crystal particles is within this 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.

[0015] 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.

[0016] 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, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy; optionally, the mass content of the silicon-based material is ≥ 5% based on the total mass of the active material in the negative electrode plate, and can be 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.

[0017] In some embodiments, the compaction density of the negative electrode film 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.

[0018] In some embodiments, the mass content of the lyophilic polymer is ≤5% based on the total mass of the membrane layer; 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, thereby improving the liquid storage capacity of the membrane layer and the wettability of the electrolyte to the active material in the membrane layer, thereby facilitating the improvement of the cycle performance of the battery.

[0019] 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%;

[0020] The melting temperature of the fluorinated polymer is T m1 ℃, 0<T m1 ≤130;

[0021] Further optionally, the glass transition temperature of the fluorinated polymer is T g1 ℃, -30≤T g1 ≤40;

[0022] Further optionally, the fluorinated polymer comprises at least one of the compounds represented by formula (AI) to the compounds represented by formula (AIII),

[0023] 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;

[0024] In formula (AIII), R 15 Including single bonds, substituted or unsubstituted C1-C3 alkyl;

[0025] p is a positive integer selected from 1 to 3;

[0026] n is a positive integer selected from 1,000 to 30,000.

[0027] Therefore, fluoropolymers 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 active materials or negative active materials during the battery cell cycle, thereby improving cycle expansion and improving cycle performance.

[0028] In some embodiments, the lyophilic polymer includes an ether polymer, and 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 sweep 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;

[0029] Optionally, the glass transition temperature of the ether polymer is T g2 ℃, -20≤T g2 ≤35;

[0030] Further optionally, the ether polymer includes at least one of the compound represented by formula (BI) and the compound represented by formula (BII),

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

[0032] 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;

[0033] The polymerization degree n of the ether polymer is a positive integer selected from 1,500 to 25,000.

[0034] 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 cell.

[0035] In some embodiments, the lyophilic polymer includes an 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 sweep 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;

[0036] Optionally, the glass transition temperature of the ester polymer is T g3 ℃, -20≤T g3 ≤35;

[0037] Further optionally, the ester polymer includes at least one of the compounds represented by formula (CI) to the compounds represented by formula (CIII),

[0038] 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;

[0039] 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;

[0040] 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;

[0041] Optionally, R 36 、R 37 and R 38 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C4 alkyl group;

[0042] The polymerization degree n of the ester polymer is selected from a positive integer ranging from 800 to 20,000.

[0043] 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 cell.

[0044] In some embodiments, the lyophilic polymer includes an aldehyde-ketone polymer, and 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 sweep 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;

[0045] Optionally, the glass transition temperature of the aldehyde-ketone polymer is T g4 ℃, -20≤T g4 ≤35;

[0046] Further optionally, the aldehyde-ketone polymer comprises at least one of the compound represented by formula (DI) and the compound represented by formula (DII),

[0047] In formula (DI), R 41 Including single bonds, substituted or unsubstituted C1-C6 methylene; R 42 including hydrogen atoms, substituted or unsubstituted C1-C6 alkyl groups;

[0048] In formula (DII), R 43 to R 46Each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group;

[0049] 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;

[0050] The degree of polymerization n of the aldehyde-ketone polymer is selected from positive integers ranging from 500 to 15,000.

[0051] 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 cell.

[0052] In some embodiments, the molecular weight of the lyophilic polymer is 2.0×10 5 g / mol to 1.2×10 6 g / mol.

[0053] In a second aspect, the present application proposes an electrical device comprising the battery according to the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0055] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0056] FIG. 2 is an exploded schematic diagram of an embodiment of the battery cell of FIG. 1 .

[0057] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0058] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0059] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0060] FIG6 is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0061] The drawings are not necessarily drawn to scale.

[0062] The accompanying drawings are described as follows: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. battery cell; 51. housing; 52. electrode assembly; 53. cover plate; 6. electrical device. DETAILED DESCRIPTION

[0063] Below, the embodiments of the battery and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0064] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3,4 and 5 are listed, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0065] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0066] 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.

[0067] 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 indicates 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 further include step (c), which indicates 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.

[0068] In the embodiments of the present application, the terms "plurality" and "multiple" refer to two or more.

[0069] The term "alkyl" encompasses both straight and branched chain alkyl groups. For example, the alkyl group may be a C1 to C5 alkyl group, a C1 to C4 alkyl group, a C1 to C3 alkyl group, or a C1 to C2 alkyl group. In some embodiments, the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and the like. Additionally, the alkyl group may be optionally substituted. When substituted, the substituent includes a fluorine atom.

[0070] The term "alkoxy" refers to a group in which an alkyl group is connected to an oxygen atom by a single bond. For example, the alkoxy group can be a C1 to C5 alkoxy group, a C1 to C3 alkoxy group, or a C1 to C2 alkoxy group. In some embodiments, the alkoxy group can include a methoxy group, an ethoxy group, or a propoxy group. In addition, the alkoxy group can be optionally substituted.

[0071] The term "halogen atom" refers to a fluorine atom, a chlorine atom, a bromine atom or the like.

[0072] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

[0073] The battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet includes a positive electrode film layer containing a positive electrode active material, which can provide active ions. The negative electrode sheet includes a negative electrode film layer containing a negative electrode active material. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrode sheets from short-circuiting, while allowing active ions to pass freely to form a loop. In order to increase the energy density of the battery, this can be achieved by selecting a high-energy-density positive electrode active material and / or negative electrode active material. Positive electrode active materials and / or negative electrode active materials that meet high energy density requirements usually have a higher specific capacity.

[0074] 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 removal of active ions from the active material, resulting in the electrolyte infiltrated in the electrode assembly being continuously squeezed out. The squeezed-out electrolyte may be difficult to absorb back, which may easily lead to liquid shortage in the electrode assembly, resulting in poor infiltration of high-capacity positive electrode active materials and / or aggravated concentration polarization, and worsening the cycle performance of the battery.

[0075] In view of the above problems, the 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 the battery cell with a high energy density, for example ≥300Wh / Kg. A lyophilic polymer is provided in the electrode plate. The lyophilic polymer has a high affinity for the electrolyte, 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, can reduce concentration polarization phenomenon, and improve the cycle performance of the battery.

[0076] Next, the technical solution of this application is described in detail.

[0077] battery cells

[0078] In a first aspect, embodiments of the present application provide a battery cell.

[0079] The battery cell includes an electrode plate, which includes a current collector and a membrane layer arranged on at least one side of the current collector, wherein the membrane layer includes an active material and a lyophilic polymer, wherein the energy density of the battery cell is ≥300Wh / Kg.

[0080] The electrode sheet may include at least one of a positive electrode sheet and a negative electrode sheet; for example, the electrode sheet includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material and a 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, the negative electrode film layer includes a negative electrode active material 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 material 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, the negative electrode film layer includes a negative electrode active material and a lyophilic polymer.

[0081] Active materials, such as positive electrode active materials and negative electrode active materials, can contribute to the energy density of battery cells. However, 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. The embodiment of the present application provides a lyophilic polymer in the film layer of the electrode plate. The lyophilic polymer can be evenly mixed with the active material particles during the preparation of 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 electrolyte's wetting performance on the film layer is improved, which can reduce the concentration polarization phenomenon and improve the cycle performance of the battery.

[0082] The energy density of a battery cell in the embodiments of this application is a term generally known in the art and specifically refers to the weight energy transferred during each charge / discharge cycle, typically expressed in units of Wh / Kg. When calculating energy density, the mass of the film layer in the electrode plate can be considered alone. Alternatively, the mass of the battery cell can be considered, meaning that in addition to the mass of the film layer, the mass of other components can also be considered. Other components are all components of the battery cell other than the film layer, such as the positive electrode current collector, negative electrode current collector, separator, electrolyte, electrode leads, insulating tape, and aluminum casing. When calculating energy density in the embodiments of this application, the mass of the battery cell is considered.

[0083] The energy density of the battery cell in the embodiment of the present application can be tested 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.

[0084] 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, such as 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, 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.

[0085] [Positive electrode]

[0086] In some embodiments, the electrode assembly includes a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer including 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, the negative electrode film layer including 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, the negative electrode film layer including a negative electrode active material, i.e., not including a lyophilic polymer.

[0087] In other embodiments, the electrode assembly includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, wherein 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 only the positive electrode active material, i.e., not include the lyophilic polymer.

[0088] 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 not only improve the electrolyte wetting performance of the positive electrode plate, but also improve the electrolyte wetting performance of 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 cycle expansion, and enhance cycle performance.

[0089] 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.

[0090] The specific capacity of the positive electrode active material is relatively high, and especially when 0.90≤a<1.0, the specific capacity of the positive electrode active material is further improved.

[0091] 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.

[0092] Illustratively, a can 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 above values.

[0093] 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.

[0094] 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.

[0095] For example, the positive electrode active material 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.

[0096] During the charge and discharge process, battery cells are accompanied by the deintercalation and deintercalation of active ions, such as Li, and their molar content varies when the battery cells are discharged to different states. The molar content of Li in the examples of positive electrode active materials in the embodiments of this application refers to the material's initial state, i.e., the state before the materials are added. When the positive electrode active material is used in a battery system, the molar content of Li may change after charge and discharge cycles.

[0097] In the examples of the positive electrode active materials in the embodiments of the present application, the molar content of oxygen O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate.

[0098] In the embodiment of the present application, the modified compound can be modified by doping or coating. Doping modification can be adding doping elements such as transition metals to the compound, and coating modification can be surface coating with materials such as carbon, that is, forming a carbon coating layer on the outer surface of the particle.

[0099] In some embodiments, the positive active material may include single crystal particles and polycrystalline particles.

[0100] A crystal is a solid composed of atoms or atomic groups arranged in a regular, repeating pattern in three-dimensional space. Single crystal particles have atoms arranged in the same orientation throughout the crystal, while polycrystalline particles are composed of multiple single crystals with different orientations. Single crystal particles can increase the compaction density of the positive electrode, while polycrystalline particles can achieve superior power performance. The combination of single and polycrystalline particles can achieve a positive electrode with both compaction density and power performance.

[0101] 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.

[0102] In some embodiments, the volume average particle size Dv50 of the single crystal particles is 2 μm to 5 μm, for example, 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.

[0103] In some embodiments, the volume average particle size Dv50 of the polycrystalline grains 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.

[0104] In the embodiments of the present application, the volume average particle size Dv50 of the particles has a meaning well known in the art. The volume average particle size Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution. It can be tested using equipment and methods well known in the art. After a fresh battery cell is fully discharged to 0% state of charge (SOC), the positive electrode sheet is disassembled, the positive current collector is removed, and the positive electrode film layer is retained. The positive electrode film layer is immersed in N-methylpyrrolidone (NMP) to wash out the binder in the positive electrode film layer, retaining the positive electrode active material. After the positive electrode active material is dried, the volume average particle size Dv50 of the particles is tested using a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016. In the embodiments of the present application, the fresh battery cell can be a battery cell that has just left the factory (not subjected to charge and discharge cycles after formation), or a battery cell that has been assembled on an electrical device and has been cycled for less than 10 cycles.

[0105] 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 combined with the polycrystalline particles to increase the compaction density of the positive electrode film layer, thereby increasing the energy density of the battery cell. For example, 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.

[0106] 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 combined 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. For example, 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.

[0107] The mass content of the single crystal particles and the mass content of the polycrystalline particles can be observed using a scanning electron microscope (SEM), and the distribution ratio of the single crystal particles and the polycrystalline particles can be quantitatively analyzed to obtain the mass content of each particle.

[0108] In some embodiments, the compaction density of the positive electrode film is ≥3.6 g / cm 3 , optional 3.6g / cm 3 Up to 3.8g / cm 3 , for example 3.6g / 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 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.

[0109] In the embodiment 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 pole piece (if it is a double-sided coated pole piece, 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 pole piece, weigh the weight of the positive electrode current 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 pole piece M1-the weight of the positive electrode current collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode pole piece H1-the thickness of the positive electrode current collector H0, 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.

[0110] In some embodiments, the mass content of the positive electrode active material is 80% to 99.9%, and optionally 92% to 99%, based on the total mass of the positive electrode film layer. When the mass content of the positive electrode active material is within the above range, it is beneficial to improve the energy density of the battery cell.

[0111] In some embodiments, the mass content of the lyophilic polymer is ≤5% based on the total mass of the positive electrode film layer, and can be optionally between 0.05% and 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, thereby enhancing the liquid storage capacity of the positive electrode film layer and improving the wettability of the electrolyte to the positive electrode active material in the positive electrode film layer, thereby improving the cycling performance of the battery cell.

[0112] For example, the mass content of the lyophilic polymer can be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.6%, 1.7%, 1.8%, 1.9%, 1.9%, 1.10%, 1.111%, 1.12%, 1.13 ... %, 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.

[0113] 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.

[0114] In the embodiments of the present application, the mass content of the polymer has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, it can be detected using thermogravimetric analysis (TGA) according to JYT014-1996. Specifically, based on the mass loss of the electrode during the heating process, a mass-temperature curve, i.e., a TG curve, is plotted. The corresponding weight loss is read according to the polymer decomposition temperature, which is the total mass of the polymer in the electrode. The mass content of the polymer and the coating weight are calculated from this. During the test, the following temperature ramp program can be used in a nitrogen atmosphere for detection: 5°C / min, RT ~ 500°C; 10°C / min, 500 ~ 600°C; constant temperature at 600°C for 10 minutes, then end.

[0115] 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 surface of the active material with electrolyte, forming an effective liquid storage point on the surface of the active material, thereby improving the liquid storage capacity of the electrode sheet. Specific types of lyophilic polymers are described below.

[0116] [Fluorinated polymers]

[0117] In some embodiments, the lyophilic polymer may include a fluorinated polymer.

[0118] In some embodiments, the crystallinity of the fluorinated polymer as measured by differential scanning calorimetry is X c1 %,0<X c1 ≤28.

[0119] In some embodiments, the melting temperature of the fluoropolymer is T m1 ℃, 0<T m1 ≤130.

[0120] In some embodiments, the glass transition temperature of the fluoropolymer is T g1 ℃, -30≤T g1 ≤40.

[0121] 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 crystal is determined by both intramolecular and intermolecular factors. The intermolecular force will affect the packing density between molecular chains. C1 It is used to characterize the degree of crystallinity in the material, which 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 perform temperature rise and fall treatment on the sample under a nitrogen atmosphere, with a heating rate of 10℃ / min from the intrinsic T g1 ℃ lower than the initial temperature of 20℃ and then heated to the 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.

[0122] Therefore, fluoropolymers 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 active materials or negative active materials during the battery cell cycle, thereby improving cycle expansion and improving cycle performance.

[0123] 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.

[0124] 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.

[0125] Illustratively, the glass transition temperature of the fluoropolymer 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.

[0126] In some embodiments, the fluorinated polymer includes at least one of the compounds represented by formula (AI) to the compounds represented by formula (AII),

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] Alternatively, when substituted, the substituent may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom. The halogen atom may include a fluorine atom, a bromine atom, and the like, and may be a fluorine atom.

[0133] In some embodiments, the fluorinated polymer comprises at least one compound of formula (AIII),

[0134] In formula (AIII), R 15 Includes single bonds, substituted or unsubstituted alkyl groups; when substituted, substituents include fluorine atoms.

[0135] 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.

[0136] Optionally, R 15 This includes single bonds, substituted or unsubstituted C1-C3 alkyl groups.

[0137] In some embodiments, p is a positive integer selected from 1 to 3, such as 1, 2 or 3.

[0138] 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.

[0139] 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),

[0140] 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),

[0141] 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),

[0142] Exemplarily, the fluorinated polymer includes one or more of polyperfluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propylene copolymer (FEP), perfluoroalkoxy polymer (PFA), perfluoropolyether (PFPE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE) and perfluoro(1-butenyl vinyl ether) polymer (CYTOP for short).

[0143] Optionally, the fluorinated polymer includes one or more of polyperfluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propylene copolymer (FEP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE).

[0144] The fluoropolymer may be derived from one or more of the following monomers: fluorocycloethane, vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene. Alternatively, the fluoropolymer may be derived from at least two of the following monomers: fluorocycloethane, vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene.

[0145] In the embodiments of the present application, the polymer may also be obtained by copolymerizing the above-mentioned structural groups with a small amount of other types of structural groups (e.g., olefin compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid, etc.). Such small amounts of monomers have relatively poor lyophilic properties, and copolymerizing the above-mentioned fluorinated polymer monomers with such monomers can improve the swelling ratio and compression modulus of the lyophilic polymer.

[0146] In some embodiments, the molecular weight of the lyophilic polymer is 2×10 5 g / mol to 1.2×10 6 g / mol.

[0147] 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.

[0148] [Ether polymers]

[0149] In some embodiments, the lyophilic polymer comprises an ether polymer.

[0150] 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 sweep 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 polymers.

[0151] Specifically, the sheet structure is prepared 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 The sample is then removed from the press after 2 minutes of calendering and placed on another vulcanizing press of the same model for cold pressing at a pressure of 10 MPa. A polymer disc (sheet structure) of fixed size is obtained using a circular mold with a diameter of 25 mm. For example, the sheet structure can be a disc with a thickness of 1-2 mm and a diameter of 25 mm; alternatively, a sample can be prepared according to the sample standard required by the test equipment.

[0152] 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 frequency dependence, and the longest chain of the polymer plays a role in the viscoelastic behavior.

[0153] The specific steps of the dynamic frequency sweep test are as follows: The dynamic frequency sweep test was 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 was in the linear point-bounce region, the strain during the dynamic frequency sweep test was 2% and the test temperature was T m2 +20℃, test frequency sweep range: 500rad / s≤w 2 ≤0.05rad / s, so as to obtain data in the lowest possible frequency range.

[0154] The dynamic frequency sweep test can characterize the degree of entanglement of molecular chains during solid-phase melting (melt state). Compared with linear structures or short-chain branched structures, long-branched structures, network structures, and low-crosslinked structures have a high degree of entanglement, which will show deviation from linear terminal behavior. Ether polymers exhibit solid-phase behavior. When the ether polymers of the present application meet the above range, the molecular chain entanglement state can be further reduced, which is conducive to the diffusion of solvent molecules in the electrolyte between the molecular chains. In addition, the ether polymers still maintain a certain degree of molecular chain entanglement, which can effectively store electrolyte and improve the cycle performance of battery cells.

[0155] In some embodiments, 1<K1≤100; alternatively, 1<K1≤10. For example, K1 can be 1.01, 1.1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the above values.

[0156] In some embodiments, the glass transition temperature of the ether polymer is T g2 ℃, -20≤T g2 ≤35. For example, 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 foregoing values. Ether polymers exhibit a certain degree of mobility above the glass transition temperature. Under external forces, they can buffer external energy through chain segment movement, exhibiting a certain degree of flexibility. This allows them to act as a buffer during the charge and discharge process of the positive or negative active material during the battery cell cycle, thereby reducing cyclic expansion and improving cycle performance.

[0157] In some embodiments, the ether polymer includes a compound represented by formula (BI),

[0158] 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; R23 This includes single bonds, and substituted or unsubstituted methylene groups.

[0159] 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.

[0160] 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.

[0161] Optionally, R 23 It includes single bonds, substituted or unsubstituted C1-C10 methylene groups.

[0162] Optionally, R 23 It includes single bonds, substituted or unsubstituted C1-C5 methylene groups.

[0163] Illustratively, the ether polymer includes at least one of the compounds represented by formula (BI-1) to the compounds represented by formula (BI-8),

[0164] In some embodiments, the ether polymer includes a compound represented by formula (BII),

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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),

[0169] The above-mentioned polymers are only examples of the structural groups of the main molecular chain. 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 (such as olefin compounds, ester monomers, nitrile monomers such as acrylonitrile, amide monomers such as acrylamide, acrylic acid and other compounds).

[0170] 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.

[0171] In some embodiments, the degree of polymerization n of the ether polymer is selected from a positive integer between 1500 and 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.

[0172] Optionally, the polymerization degree n of the ether polymer is a positive integer selected from 3,000 to 18,000.

[0173] 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 can 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.

[0174] [Ester polymer]

[0175] In some embodiments, the lyophilic polymer comprises an ester polymer.

[0176] 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 sweep 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.

[0177] Specifically, the preparation process of the sheet structure is similar to that of the ether polymer, and will not be further described here. When the ester polymer of the present application meets the above range, it can further reduce the entanglement of the molecular chains, which facilitates the diffusion of solvent molecules in the electrolyte between the molecular chains. Furthermore, the ester polymer still maintains a certain degree of molecular chain entanglement, which can effectively store the electrolyte and improve the cycling performance of the battery cell.

[0178] In some embodiments, 1<K2≤100; alternatively, 1<K2≤10. For example, K2 can be 1.01, 1.1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the above values.

[0179] In some embodiments, the glass transition temperature of the ester polymer is T g3 ℃, -20≤T g3 ≤35; illustratively, the glass transition temperature of the ester polymer can be -20°C, -15°C, -10°C, -5°C, -0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, or a range consisting of any two of the foregoing values. Ester polymers exhibit a certain degree of mobility above the glass transition temperature. Under external forces, they can buffer external energy through chain segment movement, exhibiting a certain degree of flexibility. This allows them to act as a buffer during the charge and discharge process of the positive or negative active material during the cycling of battery cells, thereby reducing cyclic expansion and improving cycle performance.

[0180] In some embodiments, the ester polymer includes a compound represented by formula (CI),

[0181] In formula (CI), R 31 、R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted alkyl group; R 34 It includes a substituted or unsubstituted alkyl group, or a substituted or unsubstituted hydroxyalkyl group.

[0182] Optionally, R 31 、R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C10 alkyl group.

[0183] Optionally, R 31 、R 32 and R 33 Each independently includes a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group.

[0184] In some embodiments, R 34 It includes substituted or unsubstituted C1-C10 alkyl groups, or substituted or unsubstituted C1-C10 hydroxyalkyl groups.

[0185] In some embodiments, R 34 It includes substituted or unsubstituted C1-C8 alkyl groups, or substituted or unsubstituted C1-C8 hydroxyalkyl groups.

[0186] In some embodiments, R 31 This includes a hydrogen atom, or a substituted or unsubstituted methyl group.

[0187] In some embodiments, R 32 and R 33 Each independently includes a hydrogen atom.

[0188] Illustratively, the ester polymer includes at least one of the compounds represented by formula (CI-1) to the compounds represented by formula (CI-15),

[0189] In some embodiments, the ester polymer includes a compound represented by formula (CII),

[0190] In formula (CII), R 35 This includes substituted or unsubstituted methylene groups.

[0191] Optionally, R 35 This includes substituted or unsubstituted C1-C10 methylene groups.

[0192] Optionally, R 35 This includes substituted or unsubstituted C2-C6 methylene groups.

[0193] Optionally, R 35 This includes substituted or unsubstituted C2-C4 methylene groups.

[0194] Illustratively, the ester polymer includes at least one of the compounds represented by formula (CII-1) to the compounds represented by formula (CII-5),

[0195] In some embodiments, the ester polymer includes a compound represented by formula (CIII),

[0196] 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;

[0197] Optionally, R 36 、R 37 and R 38 Each independently includes a hydrogen atom, a substituted or unsubstituted C1-C4 alkyl group.

[0198] Illustratively, the ester polymer includes at least one of the compounds represented by formula (CIII-1) to the compounds represented by formula (CIII-5),

[0199] 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).

[0200] 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.

[0201] In some embodiments, the degree of polymerization n of the ester polymer is selected from a positive integer between 800 and 20,000, for example, 800, 1,000, 1,500, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000, or a range consisting of any two of the above values.

[0202] In some embodiments, the degree of polymerization n of the ester polymer is a positive integer selected from 1,000 to 15,000.

[0203] In some embodiments, the molecular weight of the lyophilic polymer is 2×10 5 g / mol to 1.2×10 6 g / mol.

[0204] 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.

[0205] [Aldehyde and Ketone Polymers]

[0206] In some embodiments, the lyophilic polymer comprises an aldehyde-ketone polymer.

[0207] 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 sweep 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 polymer.

[0208] Specifically, the preparation process of the sheet structure is similar to the preparation process of the ether polymer, which will not be repeated 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 conducive to the diffusion of solvent molecules in the electrolyte between the molecular chains; moreover, 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 cell.

[0209] In some embodiments, 0.8≤K3≤100; alternatively, 0.8≤K3≤10. For example, K3 can be 0.8, 0.85, 0.9, 1, 1.01, 1.1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the above values.

[0210] 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 foregoing values. Aldehyde-ketone polymers exhibit a certain degree of mobility above their glass transition temperature. Under external forces, they can buffer external energy through chain segment movement, exhibiting a certain degree of flexibility. This allows them to act as a buffer during the charge and discharge process of the positive or negative active material during the cycling of battery cells, thereby reducing cyclic expansion and improving cycling performance.

[0211] In some embodiments, the aldehyde-ketone polymer comprises a compound represented by formula (DI),

[0212] In formula (DI), R 41 Including single bonds, substituted or unsubstituted C1-C6 methylene; R 42 This includes a hydrogen atom, and a substituted or unsubstituted C1-C6 alkyl group.

[0213] Optionally, R 41It includes single bonds, substituted or unsubstituted C1-C2 methylene groups.

[0214] Optionally, R 42 This includes hydrogen atoms, and substituted or unsubstituted C1-C3 alkyl groups.

[0215] In the embodiments of the present application, a single bond indicates 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 R 41 The carbon atoms on both sides are connected by single bonds.

[0216] 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),

[0217] Illustratively, the aldehyde-ketone polymer includes a compound represented by formula (DII),

[0218] 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.

[0219] 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.

[0220] 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),

[0221] The above polymers are only examples of the 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.).

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

[0223] In some embodiments, the degree of polymerization n of the aldehyde-ketone polymer is selected from a positive integer between 500 and 15,000, such as 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.

[0224] Optionally, the degree of polymerization n of the aldehyde-ketone polymer is selected from a positive integer ranging from 500 to 10,000.

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

[0226] 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.

[0227] The relevant parameters of the lyophilic polymer according to the embodiment of the present application can be detected by the following methods:

[0228] 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 using a Thermo Nicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR), and then tested in accordance with the standard GB / T6040-2002. The test range is: ATR method 600-4000 cm -1 ; Repeatability: ±2cm -1 ; Resolution: better than 4cm -1 ; Transmission depth 0.2~0.6μm.

[0229] The structure of the lyophilic polymer according to the embodiment of the present application can be tested by nuclear magnetic resonance (NMR). Specifically, 1H NMR and 13C NMR are performed on a Varian Mercury Plus-400 NMR spectrometer at a test temperature of 20° C., TMS as an internal standard, CDCl 3 as a solvent, and a proton resonance frequency of 400 MHz.

[0230] The polymer monomer type of the lyophilic polymer in the embodiment of the present application (especially suitable for monomers with a relatively small proportion in the polymer) can be tested by pyrolysis-gas chromatography-mass spectrometry. The specific testing steps are as follows: accurately weigh 0.5 mg of sample and put it into the sample cup. After fixing it to the injection rod, it is loaded into the pyrolyzer installed near the GC (gas chromatography) injection port. After the pyrolyzer temperature reaches the set temperature, press the injection button, and the sample cup falls rapidly into the core of the pyrolysis furnace by free fall. In the inert gas N2 atmosphere, the volatile components are instantly vaporized and carried into the gas chromatography column by the carrier gas for separation. Finally, it is detected by a flame ionization detector FID or a mass spectrometer MS to obtain a gas chromatogram or a total ion current diagram.

[0231] The molecular weight of the lyophilic polymer in the embodiment of the present application has a well-known meaning in the art and can be measured using commonly used equipment and methods in the art. It can be tested by gel permeation chromatography (GPC) in accordance with GB / T21863-2008. The specific testing steps are as follows: take an appropriate amount of the sample to be tested (the sample concentration is sufficient to ensure 8%-12% shading), add 20 ml of deionized water, and simultaneously ultraviolet (53KHz / 120W) for 5 minutes to ensure that the sample is completely dispersed, and then measure the sample in accordance with GB / T19077-2016 / ISO 13320:2009 standard.

[0232] In some embodiments, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer may be disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0233] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil or an aluminum alloy foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include a combination of one or more selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. The polymer material base layer may include a combination of one or more selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0234] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application embodiment does not particularly limit the type of positive electrode conductive agent. For example, the positive electrode conductive agent may include a combination of one or more selected from superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is less than 5% based on the total mass of the positive electrode film layer.

[0235] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. The embodiments of the present application have 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 to the crystallinity of the fluorinated polymer in the embodiment of the present application, the crystallinity of the positive electrode binder is higher.

[0236] The positive electrode film layer is typically formed by coating the positive electrode slurry onto the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, lyophilic polymer, optional conductive agent, optional binder, and any other components in a solvent and stirring them evenly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP). Of course, the preparation of the positive electrode sheet is not limited to the above method; the preparation methods described above can also be used.

[0237] [Negative electrode]

[0238] In some embodiments, the electrode assembly includes a negative electrode plate, which 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.

[0239] In some embodiments, the negative electrode active material includes a silicon-based material. Silicon-based materials have a high theoretical capacity and can effectively increase the energy density of the battery cell.

[0240] In some embodiments, the mass content of the silicon-based material is ≥5% based on the total mass of the negative electrode active material, 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.

[0241] 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.

[0242] 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.

[0243] Elemental silicon can be made of 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.

[0244] 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.

[0245] Silicon alloy materials combine silicon and metal elements to form a single material. They can alleviate internal stress during lithium insertion and extraction, and enhance properties such as electrical conductivity, thereby improving the overall electrochemical performance of the negative electrode. Alloying elements can include titanium, copper, silver, tin, and others. For example, nanosilicon particles can serve as the core, while a metal shell can be applied to at least a portion of the surface of the nanosilicon particles.

[0246] In some embodiments, the negative electrode active material may further include a carbon-based material, including at least one of natural graphite, artificial graphite, soft carbon, and hard carbon. Carbon-based materials are relatively stable and, when used in combination with silicon-based materials, can improve the cycle stability and energy density of the negative electrode.

[0247] In some embodiments, based on the total mass of the negative electrode active material, the mass content of the carbon-based material is ≤95%; optionally, it is 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.

[0248] In some embodiments, the negative electrode active material may further include at least one of a tin-based material and lithium titanate.

[0249] In some embodiments, the mass content of the negative electrode active material is 80% to 99.9%, or optionally 90% to 99%, based on the total mass of the negative electrode film layer. When the mass content of the negative electrode active material is within the above range, it is beneficial to improve the energy density of the battery cell.

[0250] In some embodiments, the compaction density of the negative electrode film 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 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.

[0251] In some embodiments, the mass content of the lyophilic polymer is ≤5% based on the total mass of the negative electrode film layer, and 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, thereby enhancing the liquid storage capacity of the negative electrode film layer and improving the wettability of the electrolyte to the negative electrode active material in the negative electrode film layer, thereby improving the cycling performance of the battery cell.

[0252] For example, the mass content of the lyophilic polymer can be 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.55%, 0.58%, 0.60%, 0.70%, 0.80%, 0.90%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.6%, 1.7%, 1.8%, 1.9%, 1.9%, 1.10%, 1.111%, 1.12%, 1.13 ... %, 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.

[0253] 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.

[0254] 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 surface of the active material with electrolyte, thereby forming effective liquid storage points on the surface of the active material and improving the liquid storage capacity of the electrode sheet.

[0255] 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.

[0256] In some embodiments, the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0257] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present embodiments do not particularly limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent based on the total mass of the negative electrode film layer is ≤5%.

[0258] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application embodiment does not particularly limit 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, water-based 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, the mass percentage of the negative electrode binder based on the total mass of the negative electrode film layer is ≤5%.

[0259] In some embodiments, the negative electrode film layer may optionally include other additives. For example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like. In some embodiments, the weight percentage of the other additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0260] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0261] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, a lyophilic polymer, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them evenly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. Of course, the preparation of the negative electrode sheet is not limited to the above method; the preparation methods described above can also be used.

[0262] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0263] [Isolation film]

[0264] In some embodiments, the battery cell includes a separator.

[0265] In some embodiments, the separator includes a substrate.

[0266] In some embodiments, a separator includes a substrate and a coating disposed on at least one surface of the substrate.

[0267] The embodiments of the present application are not particularly limited to the material of the substrate. Any known substrate with good chemical and mechanical stability may be selected, such as at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate may be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer may be the same or different.

[0268] 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.

[0269] In some embodiments, the decomposition temperature of the heat-resistant filler may be above 200° C., so that the heat-resistant filler may have good thermal stability and be difficult to decompose, thereby further improving the heat resistance of the isolation membrane.

[0270] The inorganic particles have the characteristics of high thermal stability and non-decomposability. Optionally, the inorganic particles include at least one of inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ion conductivity but not storing ions, and inorganic particles capable of undergoing electrochemical reactions.

[0271] Alternatively, the inorganic particles having a dielectric constant of 5 or more include boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0<m<1, 0<n<1), Pb(Mg3Nb 2 / 3)O3-PbTiO3 (abbreviated as PMN-PT), and at least one of their respective modified inorganic particles. Optionally, the modification method of each inorganic particle may be chemical modification and / or physical modification. Chemical modification methods include coupling agent modification (for example, using silane coupling agent, titanate coupling agent, etc.), surfactant modification, polymer grafting modification, etc. Physical modification methods may be mechanical force dispersion, ultrasonic dispersion, high energy treatment, etc. The modification treatment can reduce the agglomeration of inorganic particles, thereby enabling them to form a more stable and uniform spatial network structure with nanocellulose; in addition, by selecting coupling agents, surfactants or polymer-modified inorganic particles with specific functional groups, it is also helpful to improve the coating's wetting properties for the electrolyte and improve the bonding strength between the coating and the substrate.

[0272] Alternatively, inorganic particles having ion conductivity but not storing ions include Li3PO4, lithium titanium phosphate Li x1 Ti y1 (PO4)3, lithium aluminum titanium phosphate Li x2 Al y2 Ti z1 (PO4)3, (LiAlTiP) x3 O y3 Type glass, lanthanum lithium titanate Li x4 La y4 TiO3, lithium germanium thiophosphate Li x5 Ge y5 P z2 S w , lithium nitride Li x6 N y6 、SiS2 type glass Li x7 Si y7 S z3 and P2S5 glass Li x8 P y8 S z4 At least one of the following: 0<x1<2, 0<y1<3, 0<x2<2, 0<y2<1, 0<z1<3, 0<x3<4, 0<y3<13, 0<x4<2, 0<y4<3, 0<x5<4, 0<y5<1, 0<z2<1, 0<w<5, 0<x6<4, 0<y6<2, 0<x7<3, 0<y7<2, 0<z3<4, 0<x8<3, 0<y8<3, 0<z4<7. This can further improve the ion transport properties of the isolation membrane.

[0273] Organic particles have good thermal stability and are not easy to decompose, which can improve the heat resistance of the isolation membrane; at the same time, when the internal temperature of the battery cell reaches the melting point of the organic particles due to overcharge abuse, heat abuse, etc., the organic particles can also melt and be absorbed into the micropores of the substrate due to capillary action to play a role in closing the pores and breaking the circuit, which is beneficial to ensure that the battery cell has high safety performance.

[0274] 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).

[0275] In some embodiments, the coating further comprises a binder. The present application does not particularly limit the type of binder; any known material with good adhesive properties may be used. For example, the binder comprises at least one of an aqueous solution-based acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, or sodium acrylate, or a copolymer with other comonomers), polyvinyl alcohol, an isobutylene-maleic anhydride copolymer, and polyacrylamide.

[0276] Optionally, the binder content in the coating is <30%, based on the mass of the coating.

[0277] [Electrolyte]

[0278] In some embodiments, the battery cells include an electrolyte.

[0279] During the charge and discharge process of a battery cell, active ions are embedded and released back and forth between the positive and negative electrodes, and the electrolyte conducts the active ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and it can be selected according to actual needs.

[0280] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0281] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0282] 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).

[0283] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0284] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0285] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0286] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell can also be a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0287] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square or any other shape. FIG1 shows a battery cell 5 with a square structure as an example.

[0288] In some embodiments, as shown in Figures 1 and 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0289] The manufacturing method of the battery cell of the present application is well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be wound or laminated to form an electrode assembly. The electrode assembly is then placed in an outer packaging, dried, and then injected with electrolyte. The battery cell is then vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell.

[0290] 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.

[0291] Figure 3 is a schematic diagram of an exemplary battery module 4. As shown in Figure 3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0292] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0293] 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.

[0294] Both the battery module 4 and the battery pack can be used as specific examples of batteries in the embodiments of the present application.

[0295] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0296] Electrical devices

[0297] In a second aspect, the present application provides an electrical device, which includes at least one of the battery cells, battery modules and battery packs of the present application. The battery cells, battery modules and battery packs can be used as power sources for the electrical device, and can also be used as energy storage units for the electrical device. The electrical device may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. In some embodiments, the battery cell includes an injection hole for injecting electrolyte; when the battery cell is applied to the electrical device, the injection hole is located at the bottom of the battery cell in the vertical direction. Since the amount of free electrolyte in the battery cell is extremely small, or even no free electrolyte, when the injection hole is set at the bottom of the battery cell in the vertical direction, the reliability of the battery cell can also be improved, thereby improving the reliability of the electrical device.

[0298] The electric device can select a battery cell, battery module or battery pack according to its usage requirements. Figure 6 is a schematic diagram of an electric device as an example. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the electric device, a battery pack 1 or a battery module can be used. As another example, the electric device can be a mobile phone, a tablet computer, a laptop computer, etc. The electric device usually requires to be lightweight and thin, and a battery cell can be used as a power source.

[0299] Example

[0300] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0301] Example 1 Preparation of lithium-ion battery

[0302] (1) Preparation of positive electrode sheet:

[0303] The positive electrode slurry is prepared by mixing a lyophilic polymer, a positive electrode active material, carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder in a mass ratio of 0.2:97.8:1:1 in N-methylpyrrolidone (NMP). The slurry is then coated onto a current collector aluminum foil, dried at 85°C, and cold-pressed. The slurry is then trimmed, cut, and slit, and then dried at 85°C under vacuum for 4 hours to form the positive electrode sheet. The polyvinylidene fluoride (PVDF) binder has a crystallinity of 48%.

[0304] (2) Preparation of negative electrode sheet:

[0305] The lyophilic polymer, negative electrode active material, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were mixed uniformly in deionized water at a mass ratio of 2:94.5:0.5:2:1 to form a negative electrode slurry. The negative electrode slurry was coated on the current collector copper foil and dried at 85°C. After cold pressing, trimming, cutting, and slitting, it was dried at 120°C under vacuum for 12 hours to form the negative electrode sheet.

[0306] (3) Preparation of electrolyte:

[0307] The electrolyte includes an organic solvent and a lithium salt. The organic solvent includes ethylene carbonate EC and ethyl methyl carbonate (EMC) (volume ratio 3:7), and the lithium salt includes 1 mol / L LiPF6.

[0308] (4) Preparation of lithium-ion batteries:

[0309] Using polyethylene film (PE) as a separator, the positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a lithium-ion battery is obtained.

[0310] Example 2 to Example 6

[0311] A lithium-ion battery was prepared using 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.

[0312] Example 7 to Example 16

[0313] A lithium-ion battery was prepared using a method similar to that of Example 1. Unlike Example 1, the amount of the lyophilic polymer used in Examples 7 to 16 was adjusted.

[0314] Example 17 to Example 20

[0315] Lithium-ion batteries were prepared using a method similar to that of Example 1. Unlike Example 1, the types of active materials were adjusted in Examples 17 to 20.

[0316] Example 21 to Example 23

[0317] Lithium-ion batteries were prepared using a method similar to that of Example 1. Unlike Example 1, the grain structure of the positive electrode active material was adjusted in Examples 21 to 23.

[0318] Comparative Example 1

[0319] A lithium-ion battery was prepared using a method similar to that of Example 1. Unlike Example 1, no lyophilic polymer was used in Comparative Example 1. The electrode preparation process was as follows:

[0320] (1) Preparation of positive electrode sheet:

[0321] The positive electrode slurry is prepared by mixing the positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 97.5:2:0.5 in N-methylpyrrolidone (NMP). The slurry is then coated onto a current collector aluminum foil, dried at 85°C, and cold-pressed. The slurry is then trimmed, cut, and slit, and then dried at 85°C under vacuum for 4 hours to form the positive electrode sheet. The binder polyvinylidene fluoride (PVDF) has a crystallinity of 48%.

[0322] (2) Preparation of negative electrode sheet:

[0323] The negative electrode active material, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were added to deionized water at 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. After cold pressing, trimming, cutting, and slitting, it was dried under vacuum at 120°C for 12 hours to form the negative electrode sheet.

[0324] Comparative Example 2

[0325] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the type of polymer was adjusted in Comparative Example 2.

[0326] Test section

[0327] 1. Lithium-ion battery capacity retention test

[0328] The lithium-ion batteries prepared in the examples and comparative examples were charged at a constant current of 1C to 4.25V at 45°C, then charged at a constant voltage of 4.25V to a current of 0.05C, left for 5 minutes, and then discharged at 1C to 2.8V. The resulting capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle was recorded. The battery capacity retention rate after each cycle is Pn = Cn / C0*100%. The 1200 point values ​​P1, P2...P1200 are used as the vertical axis, and the corresponding number of cycles is used as the horizontal axis to obtain a dot plot of the battery capacity retention rate versus the number of cycles.

[0329] During this test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and so on, and the 1200th cycle corresponds to n=1200. For example, the battery capacity retention data corresponding to Example 1 in Table 1 is the data measured after 1200 cycles under the above test conditions, namely the value of P1200. The testing process for Comparative Example 1 and other examples is the same as above.

[0330] 2. Lithium-ion battery DC impedance test

[0331] The lithium-ion batteries prepared in the Examples and Comparative Examples were charged at 45°C at a constant current of 1 / 3C to 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C. After 5 minutes of rest, the voltage V1 was recorded. The batteries were then discharged at 1 / 3C for 30 seconds, and the voltage V2 was recorded. The internal resistance DCR1 of the battery after the first cycle was calculated as (V2-V1) / 1 / 3C. The above steps were repeated for the same battery, and the internal resistance DCRn of the battery after the nth cycle (n=1, 2, 3, ..., 1200) was simultaneously recorded. The 1200 points (DCR1, DCR2, DCR3, ..., DCR1200) were plotted as the ordinate, and the corresponding cycle number as the abscissa, to produce a graph of the discharge DCIR versus cycle number for the polymers in the Examples and Comparative Examples.

[0332] During this test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and so on, and the 1200th cycle corresponds to n=1200. For example, the internal resistance increase ratio of the battery in Example 1 in Table 1 = (DCRn - DCR1) / DCR1 * 100%. The testing procedures for Comparative Example 1 and the other examples are the same as above. The data in Table 1 were measured after 1200 cycles under the above test conditions.

[0333] Test results

[0334] The test results are shown in Tables 1 to 4.

[0335] Table 1

[0336] 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%.

[0337] Table 2

[0338] Table 3

[0339] 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.

[0340] The amount of the lyophilic polymer added to the positive electrode sheet is 0%, indicating that no lyophilic polymer is added to the positive electrode film layer.

[0341] 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.

[0342] 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.

[0343] 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%.

[0344] Table 4

[0345] As can be seen from Table 4, the positive and negative electrode sheets of Comparative Example 1 do not contain a lyophilic polymer. 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 sheets and deteriorating the cycle performance of the lithium-ion battery.

[0346] Although a polymer is added to the electrode in Comparative Example 2, the polymer has poor lyophilicity, resulting in low liquid retention efficiency and high impedance that deteriorates the battery kinetics.

[0347] 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 the concentration polarization phenomenon and improve the cycle performance of the battery.

[0348] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. 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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