Battery cell, battery, and electric apparatus

Abstract

A battery cell, a battery, and an electric apparatus. The battery cell comprises a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a positive current collector, and a positive active material layer located on at least one side of the positive current collector; the negative electrode sheet comprises a negative current collector, and two insulating coatings which are arranged on the surface of the negative current collector which is close to the positive electrode sheet, the distance between the two insulating coatings being greater than the width of the positive active material layer, and the two insulating coatings not being directly opposite to the positive active material layer; the negative electrode sheet also optionally comprises an interface modification layer which is arranged on the negative current collector and is located between the two insulating coatings; and the thickness of the insulating coatings is configured to be greater than the sum of the thickness of the optional interface modification layer and 1.1 times of the theoretical thickness of a metal deposition layer which is deposited during the charging of the battery cell, and be less than the sum of the theoretical thickness of the metal deposition layer deposited during the charging of the battery cell, the thickness of the positive active material layer, and the thickness of the optional interface modification layer.

Description

Battery cells, batteries and electrical devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202323160727.X, filed on November 22, 2023, entitled “Battery Cell, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] As energy and environmental issues become increasingly prominent, the new energy industry has received increasing attention. To further increase battery energy density, cathode-free batteries have been developed. However, the problem of dendrite growth at the cathode end of cathode-free batteries has become a key issue hindering their commercialization.

[0005] Summary of the Invention

[0006] The present application provides a battery cell, a battery and an electrical device, which can make the battery have high reliability, good cycle performance and good processing performance.

[0007] In a first aspect, the present application provides a battery cell, comprising a positive electrode plate and a negative electrode plate, the positive electrode plate comprising a positive electrode collector and a positive electrode active material layer located on at least one side of the positive electrode collector; the negative electrode plate comprising a negative electrode collector and two insulating coatings arranged on the surface of the negative electrode collector near the positive electrode plate, the distance between the two insulating coatings being greater than the width of the positive electrode active material layer, and the two insulating coatings not being directly opposite to the positive electrode active material layer; the negative electrode plate may also optionally comprise an interface modification layer arranged on the negative electrode collector and located between the two insulating coatings; the thickness of the insulating coating is configured to be greater than 1.1 times the theoretical thickness of the metal deposition layer deposited when the battery cell is charged and the sum of the thickness of the optional interface modification layer, and less than the sum of the theoretical thickness of the metal deposition layer deposited when the battery cell is charged, the thickness of the positive electrode active material layer and the thickness of the optional interface modification layer.

[0008] In the embodiment of the present application, the thickness of the insulating coating is configured to be greater than 1.1 times the theoretical thickness of the metal deposition layer deposited when the battery cell is charged and the thickness of the optional interface modification layer. Due to the poor electronic conductivity of the insulating coating, metal deposition on the insulating coating can be avoided as much as possible. The problem of short circuit in the battery caused by the growth of dendrites at the negative terminal bypassing the insulating coating can also be effectively reduced, thereby improving the reliability of the battery, reducing the irreversible loss of capacity due to dendrite breakage, and improving the cycle performance of the battery.

[0009] At the same time, the thickness of the insulating coating is also configured to be less than the sum of the theoretical thickness of the metal deposition layer deposited during battery cell charging, the thickness of the positive electrode active material layer, and the thickness of the optional interface modification layer. This is because if the insulating coating is too thick, it will not only increase the weight of the battery cell and reduce the energy density of the battery cell, but also cause bulging of the battery cell after assembly, affecting the processing performance of the battery cell. In addition, if the insulating coating is too thick, it will cause misalignment when the electrode sheets are stacked, increase the ion transmission path between the positive and negative electrodes, and further affect the cycle performance of the battery cell.

[0010] Therefore, the battery cell provided by the embodiment of the present application can have high reliability, good cycle performance and good processing performance.

[0011] In some embodiments, the thickness of the insulating coating is configured to be greater than 1.25 times the theoretical thickness of the metal deposition layer deposited when the battery cell is charged and the thickness of the optional interface modification layer, and less than the sum of the theoretical thickness of the metal deposition layer deposited when the battery cell is charged, the thickness of the positive electrode active material layer and the thickness of the optional interface modification layer.

[0012] This can further reduce the problem of short circuit in the battery caused by the growth of dendrites at the negative terminal bypassing the insulating coating, improve the reliability of the battery, and further reduce the irreversible loss of capacity due to dendrite breakage, thereby improving the cycle performance of the battery.

[0013] In some embodiments, the capacity per unit area of ​​the positive electrode active material layer is recorded as M mAh / cm 2 The theoretical gram capacity of the metal deposited when the battery cell is charged is recorded as C a mAh / g, the theoretical density of the metal deposited when the battery cell is charged is recorded as ρ a g / cm 3 , then the theoretical thickness of the metal deposition layer deposited when the battery cell is charged is (10000×M) / (C a ×ρ a ), unit is μm.

[0014] In some embodiments, the density of the insulating coating is greater than or equal to 20%, and can be optionally 50%-80%. This can reduce the continued growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuit problems in the battery and ensuring high reliability and good cycle performance.

[0015] In some embodiments, inorganic insulating fillers are dispersed in the insulating coating.

[0016] In some embodiments, the volume distribution particle size Dv50 of the inorganic insulating filler is less than or equal to 2 μm, and can be selected from 0.001 μm to 0.5 μm. When the volume distribution particle size Dv50 of the inorganic insulating filler is within the above range, it is conducive to the close packing of the inorganic insulating filler and can also increase the density of the insulating coating, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery's charge and discharge process, thereby reducing the internal short circuit problem of the battery and also ensuring high reliability and good cycle performance of the battery.

[0017] In some embodiments, the thickness of the insulating coating is denoted as H0 μm, the volume distribution particle size Dv50 of the inorganic insulating filler is denoted as D0 μm, and H0 / D0 ≥ 5. This improves the density and uniformity of the insulating coating, thereby reducing the continued growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuit problems in the battery and ensuring high reliability and good cycle performance.

[0018] In some embodiments, the tap density of the inorganic insulating filler is 0.8 g / cm 3 -2.0g / cm 3 , optional 0.95g / cm 3 -1.40g / cm 3 When the tap density of the inorganic insulating filler is within the above range, the density of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0019] In some embodiments, the specific surface area of ​​the inorganic insulating filler is 3m 2 / g-25m 2 / g, optional 7m 2 / g-20m 2 When the specific surface area of ​​the inorganic insulating filler is within the above range, the density of the insulating coating can be increased, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0020] In some embodiments, the surface density of the insulating coating is 0.06 mg / cm 2 -13.0mg / cm 2 , optional 0.10mg / cm 2 -3.50mg / cm 2When the surface density of the insulating coating is within the above range, the density and uniformity of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during battery charging and discharging, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0021] In some embodiments, the two insulating coatings are respectively a first insulating coating and a second insulating coating. The first insulating coating is located on the negative electrode tab side of the negative electrode plate. The width of the first insulating coating is denoted as W1, and the width of the second insulating coating is denoted as W2. W1 is greater than or equal to 0.5 mm, W2 is greater than or equal to 0.5 mm, and W1 / W2 is greater than or equal to 0.5, and can be selected from 1 to 3. The current density distribution in the negative electrode tab region is generally large and the temperature in the negative electrode tab region is higher. As a result, the metal deposition growth is looser and dendrites are more likely to form in the negative electrode tab region. By adjusting W1 / W2 within the above range, the battery performance can be further improved and the internal short circuit problem of the battery can be further reduced.

[0022] In some embodiments, W1 is 0.5 mm-20 mm, optionally 1 mm-15 mm.

[0023] In some embodiments, W2 is 0.5 mm-10 mm, optionally 1 mm-5 mm.

[0024] In some embodiments, the insulating coating includes a first sublayer and a second sublayer positioned between the first sublayer and the negative electrode current collector. The first sublayer is free of inorganic insulating fillers, while the second sublayer is dispersed with inorganic insulating fillers. This allows for better adhesion between the insulating coating and the separator, further reducing the growth of dendrites at the negative electrode end along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuits in the battery and ensuring high reliability and good cycle performance.

[0025] In some embodiments, the insulating coating includes a first sublayer and a second sublayer positioned between the first sublayer and the negative electrode current collector. An inorganic insulating filler is dispersed in the first sublayer, and an inorganic insulating filler is dispersed in the second sublayer. The weight content of the inorganic insulating filler in the first sublayer is less than the weight content of the inorganic insulating filler in the second sublayer. This improves adhesion between the insulating coating and the separator, further reduces the growth of dendrites at the negative electrode end along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuits in the battery and ensuring high reliability and good cycle performance.

[0026] In some embodiments, the thickness ratio of the first sublayer to the second sublayer is (0.1-0.9):1, and can optionally be (0.2-0.5):1. When the thickness ratio of the first sublayer to the second sublayer is within the above range, the insulating coating layer can be better bonded to the separator, while also providing the insulating coating with high density, high uniformity, and good resistance to dendrite penetration. This can further reduce the continued growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuit problems in the battery and ensuring high reliability and good cycle performance.

[0027] In some embodiments, the width of the interface modification layer is greater than the width of the positive electrode active material layer. This facilitates preferential deposition of metal on the interface modification layer during battery charging and minimizes metal deposition on the insulating coating, thereby reducing battery capacity loss.

[0028] In some embodiments, the battery cell further includes a separator positioned between the positive and negative electrode sheets. The bonding strength between the insulating coating and the separator is greater than the bonding strength between the interface modification layer and the separator. This improves the bonding between the insulating coating and the separator, further reducing the growth of dendrites at the negative electrode along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuits and ensuring high reliability and good cycle performance.

[0029] In some embodiments, the bonding strength between the insulating coating and the separator is 3 N / m-50 N / m, optionally 4 N / m-25 N / m. This allows for better bonding between the insulating coating and the separator, further reducing the growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuits in the battery and ensuring high reliability and good cycle performance.

[0030] In some embodiments, the two insulating coatings are respectively a first insulating coating and a second insulating coating, the first insulating coating is located on the negative electrode ear side of the negative electrode plate, the width of the first insulating coating is recorded as W1, the width of the second insulating coating is recorded as W2, and the width of the interface modification layer is recorded as W a , W1 / W a 0.01-0.1, optionally 0.01-0.05; and / or, W2 / W a The range is 0.01-0.1, and can be 0.01-0.05. This is beneficial to improving the processability of the negative electrode sheet and can also make the battery have a high energy density.

[0031] In some embodiments, the width of the interface modification layer is 50 mm-200 mm, and can be optionally 70 mm-150 mm.

[0032] In some embodiments, the thickness of the interface modification layer is 1 μm-50 μm, optionally 1 μm-20 μm.

[0033] In some embodiments, the interface modification layer contains an alkali metal affinity material, which is a sodium- or lithium-affinity material. The interface modification layer can provide active sites that induce uniform metal deposition, thereby improving the battery's cycling performance and further reducing internal short circuits caused by dendrite growth at the negative electrode during charge and discharge, thereby enhancing battery reliability.

[0034] In some embodiments, the battery cell is a negative electrode-free sodium battery cell or a negative electrode-free lithium battery cell.

[0035] In a second aspect, the present application provides a battery comprising the battery cell of the first aspect of the present application.

[0036] In a third aspect, the present application provides an electrical device comprising the battery according to the second aspect of the present application, wherein the battery is used to provide electrical energy.

[0037] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces 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 those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0039] FIG1 shows a schematic structural diagram of an electrode assembly provided in some embodiments of the present application.

[0040] FIG2 is a schematic structural diagram of the electrode assembly shown in FIG1 after charging.

[0041] FIG3 shows a schematic structural diagram of an electrode assembly provided in some other embodiments of the present application.

[0042] FIG4 is a schematic structural diagram of the electrode assembly shown in FIG3 after charging.

[0043] FIG5 shows a schematic structural diagram of an electrode assembly provided in some other embodiments of the present application.

[0044] FIG6 is a schematic diagram showing an electrical device including a battery provided in an embodiment of the present application as a power source.

[0045] In the accompanying drawings, the drawings are not necessarily drawn to scale.

[0046] The reference numerals are as follows: 101, negative electrode current collector; 102, insulating coating; 1021, first sublayer; 1022, second sublayer; 103, interface modification layer; 104, metal deposition layer; 201, positive electrode current collector; 202, positive electrode active material layer; 300, isolation membrane; T, thickness direction; W, width direction. DETAILED DESCRIPTION

[0047] Below, the embodiments of the battery cell, battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0048] " range " disclosed in the present 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 to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions without conflict, and such technical solutions should be considered to be included in the disclosure of the present application.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined with each other to form new technical solutions in the absence of conflict, and such technical solutions should be deemed to be included in the disclosure of this application.

[0051] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0052] Unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0053] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0054] The terms "first", "second" and the like in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0055] In the description of this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0056] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of the present application shown in the drawings are for illustrative purposes only and should not constitute any limitation on the present application.

[0057] In this application, the terms "plurality" and "multiple" refer to two or more.

[0058] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0059] A battery cell is the smallest unit of a battery that can independently realize the functions of charging and discharging. A battery cell can be cylindrical, rectangular, or in other shapes, and the embodiments of the present application are not limited thereto.

[0060] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0061] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0062] In some embodiments, battery cells may be assembled into a battery module. A battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module.

[0063] In some embodiments, the battery modules may 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.

[0064] In some embodiments, battery cells can be directly assembled into a battery pack. The battery pack can contain multiple battery cells, and the specific number can be adjusted according to the application and capacity of the battery pack.

[0065] An embodiment of the present application provides a battery cell. The battery cell is a negative electrode-free battery cell, for example, a negative electrode-free sodium battery cell or a negative electrode-free lithium battery cell.

[0066] A negative electrode-free battery generally refers to a battery that does not actively set a negative electrode active material layer on the negative electrode side during the battery manufacturing process. For example, during the battery manufacturing process, a negative electrode active material layer is not formed by coating or deposition of carbonaceous active materials (such as graphite, hard carbon, etc.) at the negative electrode. When the battery is charged for the first time, ions gain electrons on the negative electrode side and deposit at the negative electrode to form metal. When discharged, the metal can be converted into ions and return to the positive electrode, realizing cyclic charge and discharge. Compared with other batteries, negative electrode-free batteries can achieve higher energy density because they do not have a conventional negative electrode active material layer.

[0067] A battery cell includes an electrode assembly and an outer packaging. The electrode assembly may be a wound structure or a laminated structure, which is not limited in the embodiments of the present application. The outer packaging may be used to encapsulate the electrode assembly. The outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS). The number of electrode assemblies contained in a battery cell may be one or more, which can be adjusted according to demand.

[0068] Figure 1 shows a schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application. Figure 2 shows a schematic diagram of the structure of the electrode assembly shown in Figure 1 after charging.

[0069] As shown in FIG1 and FIG2 , the electrode assembly of the battery cell includes a separator 300 , a positive electrode sheet and a negative electrode sheet, and the separator 300 is located between the positive electrode sheet and the negative electrode sheet.

[0070] The positive electrode plate includes a positive electrode current collector 201 and a positive electrode active material layer 202 located on at least one side of the positive electrode current collector 201. The negative electrode plate includes a negative electrode current collector 101 and two insulating coatings 102 disposed on the surface of the negative electrode current collector 101 near the positive electrode plate. The distance between the two insulating coatings 102 is greater than the width of the positive electrode active material layer 202, and the two insulating coatings 102 do not directly face the positive electrode active material layer 202.

[0071] The negative electrode plate may further include an interface modification layer 103 disposed on the negative electrode current collector 101 and between the two insulating coatings 102. "Optionally" indicates that the interface modification layer 103 may or may not be disposed on the negative electrode current collector 101 of the negative electrode plate.

[0072] The thickness of the insulating coating 102 is configured to be greater than 1.1 times the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged and the thickness of the optional interface modification layer 103, and less than the sum of the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged, the thickness of the positive electrode active material layer 202 and the thickness of the optional interface modification layer 103.

[0073] For example, when the interface modification layer 103 is not provided on the negative electrode current collector 101 of the negative electrode sheet (i.e., the thickness of the interface modification layer 103 is 0), the thickness of the insulating coating 102 is configured to be greater than 1.1 times the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged, and less than the sum of the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged and the thickness of the positive electrode active material layer 202; when the interface modification layer 103 is provided on the negative electrode current collector 101 of the negative electrode sheet, the thickness of the insulating coating 102 is configured to be greater than 1.1 times the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged and the sum of the thickness of the interface modification layer 103, and less than the sum of the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged, the thickness of the positive electrode active material layer 202, and the thickness of the interface modification layer 103.

[0074] For safety reasons, the negative electrode plate typically includes an overhang area (the area where the negative electrode and the positive electrode do not overlap) and a non-overhang area (the area where the negative electrode and the positive electrode overlap). During battery charging and discharging, the overhang area can cause serious dendrite problems. The continuous growth of dendrites can pierce the separator, causing an internal short circuit and posing a safety hazard to the battery.

[0075] Currently, when providing an insulating coating on the negative electrode current collector, the thickness rebound problem during the metal deposition process and the local unevenness of the metal deposition are not taken into consideration. As a result, the negative terminal still has a short circuit problem in the battery caused by dendrite growth.

[0076] In the embodiment of the present application, the thickness of the insulating coating is configured to be greater than 1.1 times the theoretical thickness of the metal deposition layer deposited when the battery cell is charged and the thickness of the optional interface modification layer. Due to the poor electronic conductivity of the insulating coating, metal deposition on the insulating coating can be avoided as much as possible. The problem of short circuit in the battery caused by the growth of dendrites at the negative terminal bypassing the insulating coating can also be effectively reduced, thereby improving the reliability of the battery, reducing the irreversible loss of capacity due to dendrite breakage, and improving the cycle performance of the battery.

[0077] At the same time, the thickness of the insulating coating is also configured to be less than the sum of the theoretical thickness of the metal deposition layer deposited during battery cell charging, the thickness of the positive electrode active material layer, and the thickness of the optional interface modification layer. This is because if the insulating coating is too thick, it will not only increase the weight of the battery cell and reduce the energy density of the battery cell, but also cause bulging of the battery cell after assembly, affecting the processing performance of the battery cell. In addition, if the insulating coating is too thick, it will cause misalignment when the electrode sheets are stacked, increase the ion transmission path between the positive and negative electrodes, and further affect the cycle performance of the battery cell.

[0078] Therefore, the battery cell provided by the embodiment of the present application can have high reliability, good cycle performance and good processing performance.

[0079] Optionally, the thickness of the insulating coating 102 is configured to be greater than 1.25 times the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged and the thickness of the optional interface modification layer 103, and less than the sum of the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged, the thickness of the positive electrode active material layer 202 and the thickness of the optional interface modification layer 103.

[0080] Optionally, the thickness of the insulating coating 102 is configured to be greater than 1.3 times the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged and the thickness of the optional interface modification layer 103, and less than the sum of the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged, the thickness of the positive electrode active material layer 202 and the thickness of the optional interface modification layer 103.

[0081] This can further reduce the problem of short circuit in the battery caused by the growth of dendrites at the negative terminal bypassing the insulating coating, improve the reliability of the battery, and further reduce the irreversible loss of capacity due to dendrite breakage, thereby improving the cycle performance of the battery.

[0082] The capacity per unit area of ​​the positive electrode active material layer 202 is recorded as M mAh / cm 2 The theoretical gram capacity of the metal deposited when the battery cell is charged is recorded as C a mAh / g, the theoretical density of the metal deposited when the battery cell is charged is recorded as ρ a g / cm 3 , then the theoretical thickness of the metal deposition layer 104 deposited when the battery cell is charged is (10000×M) / (C a ×ρ a ), the unit is μm. 10000 is the coefficient used for conversion between units (i.e., micrometers and centimeters).

[0083] The mass of the positive electrode active material per unit area of ​​the positive electrode active material layer is recorded as m1g / cm 2, the mass gram capacity of the positive electrode active material is recorded as C1mAh / g, then M=m1×C1.

[0084] The capacity per unit area of ​​the positive electrode active material layer and the mass-gram capacity of the positive electrode active material can be obtained through coin cell testing. During testing, a coin cell can be assembled in an argon atmosphere glove box using a metal sheet (e.g., a lithium sheet or a sodium sheet) that is the same metal deposited during battery cell charging as the counter electrode and the positive electrode sheet.

[0085] At 25°C, the prepared button battery was left to stand for 6 hours, fully charged at 0.1C and fully discharged at 0.1C to obtain the discharge capacity. The capacity per unit area of ​​the positive electrode active material layer and the mass gram capacity of the positive electrode active material can then be calculated based on the discharge capacity.

[0086] The isolation film of the button cell may be a polyethylene film with a thickness of 12 μm.

[0087] The solvent of the button battery electrolyte can be diethylene glycol dimethyl ether (DEGDME), the solute can be LiPF6 or NaPF6 (the metal ion type is consistent with the metal type deposited when the battery cell is charged), and the concentration is 1 mol / L.

[0088] The button cell assembly process can adopt techniques known in the art, for example, starting from the positive electrode shell and assembling from bottom to top, or starting from the negative electrode shell and assembling from bottom to top, and the entire assembly process is carried out in an argon atmosphere glove box with a water content of less than 10 ppm.

[0089] The thickness of the insulating coating, the thickness of the positive electrode active material layer, and the thickness of the interface modification layer can be measured using a micrometer. For accuracy, multiple locations (e.g., 5-10) can be measured and then the average value can be taken.

[0090] In some embodiments, the metal deposition layer 104 deposited when the battery cell is charged may be a sodium metal layer or a lithium metal layer.

[0091] When the metal deposition layer 104 deposited during battery cell charging is a sodium metal layer, the theoretical gram capacity C of the metal (ie, sodium) deposited during battery cell charging is a mAh / g is 1166mAh / g, and the theoretical density of the metal (i.e., sodium) deposited when the battery cell is charged is ρ a g / cm 3 0.968g / cm 3 (i.e. density at 25°C).

[0092] When the metal deposition layer 104 deposited during battery cell charging is a lithium metal layer, the theoretical gram capacity C of the metal (ie, lithium) deposited during battery cell charging is amAh / g is 3860mAh / g, and the theoretical density of the metal (i.e. lithium) deposited when the battery cell is charged is ρ a g / cm 3 0.534g / cm 3 (i.e. density at 25°C).

[0093] In some embodiments, the density of the insulating coating 102 can be greater than or equal to 20%. This can reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0094] Optionally, the density of the insulating coating 102 can be 30%-85%, 50%-80%, thereby further reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby further reducing the internal short circuit problem of the battery.

[0095] The density of the insulating coating is well known in the art and can be measured using instruments and methods known in the art. The density of the insulating coating = (P1 / P2) × 100%. P1 represents the apparent density of the sample, which can be calculated based on the weight and volume of the sample; P2 represents the true density of the sample, which can be measured using a true density tester using an inert gas (such as nitrogen) as a medium and a gas displacement method in accordance with GB / T 24586-2009. During the test, a sample of appropriate size can be cut out from the area of ​​the negative electrode sheet that contains the insulating coating but does not contain the interface modification layer for testing. When the insulating coating is located on both surfaces of the negative electrode current collector, the insulating coating on one side can be scraped off for testing.

[0096] In some embodiments, an inorganic insulating filler is dispersed in the insulating coating 102. The inorganic insulating filler is an electronic insulating material, which facilitates the metal to preferentially deposit on the interface modification layer or the negative electrode current collector and avoids metal deposition on the insulating coating as much as possible, thereby reducing battery capacity loss.

[0097] The density of the insulating coating is related to the parameters of the insulating coating (such as thickness, surface density, etc.), the parameters of the inorganic insulating filler in the insulating coating (such as particle size, particle morphology, particle stacking morphology), and the content of the inorganic insulating filler and the binder. By adjusting one or more of the above parameters, the density of the insulating coating can be adjusted.

[0098] In some embodiments, the volume distribution particle size Dv50 of the inorganic insulating filler can be less than or equal to 2 μm, and can be optionally in the range of 0.001 μm to 0.5 μm. When the volume distribution particle size Dv50 of the inorganic insulating filler is within the above range, it is conducive to the close packing of the inorganic insulating filler and can also increase the density of the insulating coating, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery's charge and discharge process, thereby reducing the internal short circuit problem of the battery and also ensuring high reliability and good cycle performance of the battery.

[0099] The volume distribution particle size Dv50 of a material is well known in the art and represents the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%. It can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer in accordance with GB / T19077-2016. The testing instrument can be a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. in the UK.

[0100] In some embodiments, the thickness of the insulating coating 102 is denoted as H0 μm, the volume distribution particle size Dv50 of the inorganic insulating filler is denoted as D0 μm, and H0 / D0 ≥ 5. H0 / D0 can reflect the number of stacked layers of the inorganic insulating filler. A larger number of stacked layers of inorganic insulating filler can improve the density and uniformity of the insulating coating, thereby reducing the continued growth of dendrites at the negative terminal along the pores of the insulating coating during battery charging and discharging, thereby reducing internal short circuit problems in the battery and ensuring high reliability and good cycle performance.

[0101] In some embodiments, the tap density of the inorganic insulating filler may be 0.8 g / cm 3 -2.0g / cm 3 , optional 0.95g / cm 3 -1.40g / cm 3 When the tap density of the inorganic insulating filler is within the above range, the density of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0102] The tap density of a material is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester, as per GB / T 5162-2006. A Dandong Better BT-301 instrument can be used, using the following test parameters: vibration frequency 250 ± 15 times / minute, amplitude 3 ± 0.2 mm, vibration count 5000 times, and a 25 mL graduated cylinder.

[0103] In some embodiments, the specific surface area of ​​the inorganic insulating filler may be 3 m 2 / g-25m 2 / g, optional 7m 2 / g-20m 2 When the specific surface area of ​​the inorganic insulating filler is within the above range, the density of the insulating coating can be increased, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0104] The specific surface area of ​​a material is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using an ASAP 3020 surface area and pore size analyzer available from Micromeritics, Inc., USA.

[0105] The inorganic insulating filler in the insulating coating is a known material and can also be directly commercially obtained. In some embodiments, the inorganic insulating filler in the insulating coating includes one or more of ceramics, silicates, minerals, and glasses. Alternatively, the inorganic insulating filler includes one or more of 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, boehmite, mica, bentonite, hectorite, kaolin, and talc.

[0106] The insulating coating layer also contains a binder, which is used to bind the inorganic insulating filler to the negative electrode current collector. The binder in the insulating coating layer is a known material and can also be directly purchased commercially. In some embodiments, the binder in the insulating coating includes styrene-butadiene copolymer, acrylate-styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic rubber, butyl rubber, styrene-butadiene rubber, fluororubber, polyethylene, polypropylene, ethylene propylene diene monomer (EPM), ethylene propylene diene monomer (EPDM), polyethylene oxide, polyepichlorohydrin, polyvinyl pyrrolidone, polyphosphazene, polyacrylonitrile, polystyrene, polyvinyl pyridine, chlorosulfonated polyethylene, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyacrylic acid (PAA), polyimide, polyamideimide, polyimide-polyamideimide copolymer, and one or more polymers in which the foregoing polymers are partially or fully substituted with alkali metals.

[0107] In some embodiments, the weight content of the inorganic insulating filler in the insulating coating may be 10%-90%, optionally 10%-80%, and more optionally 20%-70%, based on the total weight of the insulating coating.

[0108] In some embodiments, the weight content of the binder in the insulating coating may be greater than or equal to 10%, optionally 20%-90%, and more optionally 30%-80%, based on the total weight of the insulating coating.

[0109] By adjusting the weight content of the inorganic insulating filler and / or binder in the insulating coating within the above range, the density and uniformity of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during battery charging and discharging, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0110] In some embodiments, the surface density of the insulating coating may be 0.06 mg / cm 2 -13.0mg / cm 2 , optional 0.10mg / cm 2 -3.50mg / cm 2 When the surface density of the insulating coating is within the above range, the density and uniformity of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during battery charging and discharging, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0111] In some embodiments, the two insulating coatings 102 are respectively a first insulating coating and a second insulating coating. The first insulating coating is located on the negative electrode ear side of the negative electrode sheet. The width of the first insulating coating is recorded as W1, and the width of the second insulating coating is recorded as W2. W1 is greater than or equal to 0.5 mm, W2 is greater than or equal to 0.5 mm, and W1 / W2 is greater than or equal to 0.5, which can be selected as 1-3.

[0112] The current density in the negative electrode tab area is usually widely distributed and the temperature in the negative electrode tab area is higher. As a result, the metal deposition growth is looser and dendrites are more easily formed in the negative electrode tab area. By adjusting W1 / W2 within the above range, the performance of the battery can be further improved and the internal short circuit problem of the battery can be further reduced.

[0113] In some embodiments, the width W1 of the first insulating coating layer may be 0.5 mm to 20 mm, and may be optionally 1 mm to 15 mm.

[0114] In some embodiments, the width W2 of the second insulating coating layer may be 0.5 mm to 10 mm, and may be optionally 1 mm to 5 mm.

[0115] The width of the first insulating coating, the width of the second insulating coating, and the width of the interface modification layer can be measured using a soft ruler with a minimum quantile of 0.5 mm. For accuracy, multiple positions (e.g., 5-10) can be measured and then averaged.

[0116] Figure 3 shows a schematic diagram of the structure of an electrode assembly provided in some other embodiments of the present application. Figure 4 shows a schematic diagram of the structure of the electrode assembly shown in Figure 3 after charging.

[0117] As shown in Figures 3 and 4, the negative electrode plate includes an interface modification layer 103, which is located between two insulating coatings 102. The interface modification layer 103 is an alkali metal affinity material layer, such as a sodium affinity layer or a lithium affinity layer.

[0118] Setting an interface modification layer on the negative electrode surface of the negative electrode-free battery can induce uniform metal deposition and alleviate the volume expansion of the negative electrode during the charging and discharging process. This can further reduce the internal short circuit problem of the battery caused by dendrite growth at the negative end during the charging and discharging process of the battery, making the battery highly reliable and with good cycle performance.

[0119] In some embodiments, the width of the interface modification layer 103 is greater than that of the positive electrode active material layer 202. This helps the metal to be preferentially deposited on the interface modification layer during battery charging and avoids metal deposition on the insulating coating as much as possible, thereby reducing battery capacity loss.

[0120] In some embodiments, the bonding force between the insulating coating 102 and the separator 300 can be greater than the bonding force between the interface modification layer 103 and the separator 300. This allows for better bonding between the insulating coating and the separator, further reducing the growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuit issues in the battery and ensuring high reliability and good cycle performance.

[0121] In some embodiments, the bonding strength between the insulating coating 102 and the separator 300 can be 3N / m-50N / m, or optionally 4N / m-25N / m. This allows for better bonding between the insulating coating and the separator, further reducing the growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuits in the battery and ensuring high reliability and good cycle performance.

[0122] In some embodiments, the two insulating coatings 102 are respectively a first insulating coating and a second insulating coating. The first insulating coating is located on the negative electrode ear side of the negative electrode sheet. The width of the first insulating coating is recorded as W1, the width of the second insulating coating is recorded as W2, and the width of the interface modification layer 103 is recorded as W a , W1 / W a It can be 0.01-0.1, optionally 0.01-0.05; and / or, W2 / W a It can be 0.01-0.1, and can be optionally 0.01-0.05. This is beneficial to improving the processability of the negative electrode sheet and can also make the battery have a high energy density.

[0123] In some embodiments, the width of the interface modification layer 103 may be 50 mm-200 mm, and optionally 70 mm-150 mm.

[0124] In some embodiments, the thickness of the interface modification layer 103 may be 1 μm-50 μm, and may be optionally 1 μm-20 μm.

[0125] In some embodiments, an alkali metal affinity material is dispersed in the interface modification layer 103. The alkali metal affinity material is a sodium-affinity material or a lithium-affinity material. The interface modification layer thus provides active sites that induce uniform metal deposition, thereby improving the battery's cycling performance and further reducing internal short circuits caused by dendrite growth at the negative terminal during charge and discharge, thereby enhancing battery reliability.

[0126] In some embodiments, the alkali metal affinity material in the interface modification layer 103 is a known material and can be directly commercially obtained. For example, it can include one or more of a carbon material, a metal, a metal alloy, and a metal oxide. The metal elements in the metal, metal alloy, and metal oxide are all known elements, for example, it can include one or more of Zn, Ag, Al, Mg, Sn, and Au.

[0127] In some embodiments, the carbon material may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, soft carbon, and hard carbon.

[0128] In order to improve battery performance, the negative electrode of the negative electrode-free battery can also be provided with some conventional substances that can be used as negative electrode active materials, such as carbon materials. Although these substances have a certain capacity, due to their low content and the fact that they are not used as the main negative electrode active materials in the battery, the battery constructed in this way can still be regarded as a negative electrode-free battery. The CB (Cell Balance) value of the negative electrode-free battery is usually very small. For example, in some embodiments, the CB value of the negative electrode-free battery can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery divided by the unit area capacity of the positive electrode. Since the negative electrode-free battery does not contain or only contains a small amount of negative electrode active material, the unit area capacity of the negative electrode is small, and thus the CB value is very small, for example, usually less than or equal to 0.1.

[0129] The interface modification layer may further include a binder. The binder is a known material and can also be directly commercially obtained. In some embodiments, the binder in the interface modification layer 103 may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), sodium carboxymethyl cellulose (CMC), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0130] In some embodiments, the weight content of the alkali metal affinity material in the interface modification layer 103 may be 2%-98%, optionally 5%-80%, based on the total weight of the interface modification layer 103 .

[0131] In some embodiments, the weight content of the binder in the interface modification layer 103 may be 2%-98%, optionally 20%-95%, based on the total weight of the interface modification layer 103 .

[0132] FIG5 shows a schematic structural diagram of an electrode assembly provided in some other embodiments of the present application.

[0133] As shown in FIG. 5 , in some embodiments, the insulating coating 102 may include a first sublayer 1021 and a second sublayer 1022 located between the first sublayer 1021 and the negative electrode current collector 101 .

[0134] In some embodiments, the first sublayer 1021 is free of inorganic insulating fillers, while the second sublayer 1022 is dispersed with inorganic insulating fillers. This allows for better adhesion between the insulating coating and the separator, further reducing the growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuits in the battery and ensuring high reliability and good cycle performance. In this case, the weight content of the binder in the first sublayer 1021 is 100%.

[0135] In some embodiments, an inorganic insulating filler is dispersed in the first sublayer 1021, and an inorganic insulating filler is dispersed in the second sublayer 1022. The weight content of the inorganic insulating filler in the first sublayer 1021 is less than the weight content of the inorganic insulating filler in the second sublayer 1022. This improves the adhesion between the insulating coating and the separator, further reduces the growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuits in the battery and ensuring high reliability and good cycle performance.

[0136] In some embodiments, the weight content of the binder in the first sub-layer 1021 is greater than or equal to 15%, and the weight content of the inorganic insulating filler is less than or equal to 85%, based on the total weight of the first sub-layer.

[0137] This can better bond the insulating coating to the isolation membrane, and further reduce the continued growth of dendrites at the negative terminal along the pores of the insulating coating during battery charging and discharging, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0138] In some embodiments, the weight content of the binder in the second sub-layer 1022 may be 1%-30%, and the weight content of the inorganic insulating filler may be 70%-99%, based on the total weight of the second sub-layer.

[0139] Optionally, the weight content of the binder in the second sub-layer 1022 may be 5%-30%, and the weight content of the inorganic insulating filler may be 70%-95%, based on the total weight of the second sub-layer.

[0140] As a result, the insulating coating has high density, high uniformity and good resistance to dendrite penetration, which can reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during battery charging and discharging, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

[0141] The types of inorganic insulating fillers in the first sublayer and the second sublayer can be the same or different, and the types of binders in the first sublayer and the second sublayer can be the same or different. The types of inorganic insulating fillers and binders can be as described above and will not be repeated here.

[0142] In some embodiments, the thickness ratio of the first sublayer 1021 to the second sublayer 1022 can be (0.1-0.9):1, or optionally (0.2-0.5):1. When the thickness ratio of the first sublayer to the second sublayer is within the above range, the insulating coating layer can be better bonded to the separator, while also providing the insulating coating with high density, high uniformity, and good resistance to dendrite penetration. This can further reduce the continued growth of dendrites at the negative terminal along the pores of the insulating coating during battery charge and discharge, thereby reducing internal short circuit problems in the battery and ensuring high reliability and good cycle performance.

[0143] In some embodiments, the negative electrode current collector 101 may include one or more of a metal foil, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, a carbon paper current collector, and a composite current collector.

[0144] In some embodiments, the negative electrode current collector 101 may have a porous structure. For example, the negative electrode current collector 101 may include one or more of a porous aluminum foil, a porous copper foil, and a porous stainless steel foil.

[0145] In some embodiments, the negative electrode current collector 101 may include a polymer material base layer and a conductive metal layer formed on at least one side of the polymer material base layer.

[0146] Optionally, the metal material in the conductive metal layer may include one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0147] Optionally, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0148] Methods for preparing negative electrode sheets are well known. In some embodiments, the interface modification layer slurry and the insulating coating slurry can be applied to the negative electrode current collector and dried. Coating methods can include gravure coating, micro-gravure coating, extrusion coating, transfer coating, or spray coating.

[0149] The positive electrode sheet includes a positive electrode current collector 201 and a positive electrode active material layer 202 located on at least one side of the positive electrode current collector 201. The positive electrode current collector 201 has two surfaces that face each other in its thickness direction, and the positive electrode active material layer 202 is located on either or both of the two opposing surfaces of the positive electrode current collector 201. As shown in Figures 1 to 5, the positive electrode active material layer 202 is located on one side of the positive electrode current collector 201, but the present application is not limited to this.

[0150] The positive electrode active material layer 202 includes a positive electrode active material.

[0151] When the battery cell is a lithium battery cell without a negative electrode, the positive electrode active material includes a material that can extract and insert lithium. As an example, the positive electrode active material may include one or more of a lithium transition metal oxide, a lithium-containing phosphate, and their respective modified compounds. Examples of lithium transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium-containing phosphates may include one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

[0152] When the battery cell is a sodium battery cell without a negative electrode, the positive electrode active material includes a material capable of extracting and inserting sodium. As an example, the positive electrode active material may include one or more of a layered transition metal oxide (including P2 type, O3 type, etc.), a polyanion material (such as phosphate, fluorophosphate, pyrophosphate, sulfate, etc.), and a Prussian material.

[0153] In some embodiments, the positive electrode active material may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M may include at least two of Fe, Co, Cr, Mn, Ni, V, Ti, Mo), NaMO2 (M may include at least two of Fe, Co, Ni, V, Ti, Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, sodium iron pyrophosphate, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0154] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0155] In some embodiments, the positive active material layer 202 may further include a positive electrode conductive agent. For example, the positive electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0156] In some embodiments, the positive electrode active material layer 202 may further include a positive electrode binder. For example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, 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).

[0157] In some embodiments, the thickness of the positive electrode active material layer 202 may be 60 μm-150 μm, and optionally 68 μm-135 μm.

[0158] In some embodiments, the positive electrode current collector 201 may be a metal foil or a composite current collector. As an example of a metal foil, aluminum 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 side of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0159] The positive electrode active material layer 202 is typically formed by coating a positive electrode slurry onto the positive electrode current collector 201, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional positive electrode conductive agent, an optional positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent may be N-methylpyrrolidone (NMP).

[0160] The separator 300 is disposed between the positive electrode and the negative electrode, and is primarily used to prevent internal short circuits. The present application does not specifically limit the type of separator, and any known porous separator with good chemical and mechanical stability can be used.

[0161] In some embodiments, the material of the isolation membrane 300 may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane 300 may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0162] The battery cell also includes an electrolyte. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on needs. For example, the electrolyte can include one or more selected from solid electrolytes and liquid electrolytes (i.e., electrolytes).

[0163] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.

[0164] When the battery cell is a negative electrode-free lithium battery cell, as an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0165] When the battery cell is a negative electrode-free sodium battery cell, as an example, the electrolyte salt may include one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorobis(oxalatophosphate) (NaDFOP) and sodium tetrafluorooxalatophosphate (NaTFOP).

[0166] In some embodiments, the solvent may include one or more of an ester solvent, a sulfone solvent, and an ether solvent. As an example, the solvent may include, but is not limited to, one or more 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), diethyl sulfone (ESE), dimethoxymethane (DMM), diethylene glycol dimethyl ether (DG), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), and tetraethylene glycol dimethyl ether.

[0167] In some embodiments, the electrolyte may optionally include additives, for example, additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature power performance, etc.

[0168] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, separator, negative electrode sheet and electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, dried and injected with the above-mentioned electrolyte, and then subjected to packaging, standing, formation and other processes to obtain a battery cell. Multiple battery cells can also be further connected in series, in parallel or in a mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in a mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0169] The embodiments of the present application also provide an electrical device, which includes a battery provided in the embodiments of the present application, and the battery is used to provide electrical energy. The battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0170] The electrical device can select a specific type of battery, such as a battery cell, a battery module, or a battery pack, according to its usage requirements.

[0171] Figure 6 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0172] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0173] Example

[0174] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0175] Example 1

[0176] (1) Preparation of negative electrode sheet

[0177] Carbon nanotubes (CNT) and sodium carboxymethyl cellulose (CMC) were fully stirred and mixed in an appropriate amount of deionized water as a solvent in a weight ratio of 80:20 to form an interface modification layer slurry.

[0178] The inorganic insulating filler alumina and the binder polyacrylic acid (PAA) were mixed in an appropriate amount of deionized water in a weight ratio of 70:30 to form an insulating coating slurry. The volume distribution particle size Dv50 of the alumina was 0.25 μm and the tap density was 1.38 g / cm 3 , specific surface area is 13.4m 2 / g.

[0179] The interface modification layer slurry is coated on the surface of the negative electrode current collector copper foil, and the insulating coating slurry is coated on both sides of the interface modification layer slurry in the width direction. After drying and welding the negative electrode tabs, the negative electrode sheet is obtained.

[0180] The thickness of the interface modification layer is 5 μm, and the thickness of the two insulating coatings is 20.4 μm.

[0181] (2) Preparation of positive electrode sheet

[0182] The positive electrode active material, sodium iron pyrophosphate, the conductive agent, carbon black (Super P), and the binder, polyvinylidene fluoride (PVDF), were thoroughly stirred and mixed in an appropriate amount of solvent, NMP, at a weight ratio of 90:5:5 to form a uniform positive electrode slurry. The positive electrode slurry was coated on the surface of the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet. The mass of the positive electrode active material per unit area of ​​the positive electrode active material layer was 0.01568 g / cm 2 The mass capacity of the positive electrode active material is 100 mAh / g, and the capacity per unit area of ​​the positive electrode active material layer is 1.568 mAh / cm 2 , the thickness of the positive electrode active material layer is 101 μm.

[0183] (3) Preparation of electrolyte

[0184] The fully dried NaPF6 was dissolved in diethylene glycol dimethyl ether (DEGDME) to prepare an electrolyte with a concentration of 1 mol / L.

[0185] (4) Preparation of isolation membrane

[0186] A porous polyethylene film was used as the separator.

[0187] (5) Preparation of batteries

[0188] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a negative electrode-free sodium battery is obtained.

[0189] Example 2

[0190] The preparation method of the battery is similar to that of Example 1, except that in the preparation of the negative electrode sheet, the thickness of the insulating coating is 22.5 μm.

[0191] Example 3

[0192] The preparation method of the battery is similar to that of Example 1, except that in the preparation of the negative electrode sheet, the thickness of the insulating coating is 30.0 μm.

[0193] Example 4

[0194] The preparation method of the battery is similar to that of Example 1, except that in the preparation of the negative electrode sheet, the thickness of the insulating coating is 20.0 μm, and the mass of the positive electrode active material per unit area in the positive electrode active material layer is 0.00941 g / cm 2 The mass capacity of the positive electrode active material is 100 mAh / g, and the capacity per unit area of ​​the positive electrode active material layer is 0.941 mAh / cm 2 , the thickness of the positive electrode active material layer is 68 μm.

[0195] Example 5

[0196] The preparation method of the battery is similar to that of Example 1, except that in the preparation of the negative electrode sheet, the thickness of the insulating coating is 33.5 μm, and the mass of the positive electrode active material per unit area in the positive electrode active material layer is 0.02509 g / cm 2 The mass capacity of the positive electrode active material is 100 mAh / g, and the capacity per unit area of ​​the positive electrode active material layer is 2.509 mAh / cm 2 , the thickness of the positive electrode active material layer is 135 μm.

[0197] Comparative Example 1

[0198] The preparation method of the battery is similar to that of Example 1, except that the preparation process of the negative electrode is different.

[0199] Carbon nanotubes (CNT) and sodium carboxymethyl cellulose (CMC) were fully stirred and mixed in an appropriate amount of deionized water as a solvent in a weight ratio of 80:20 to form an interface modification layer slurry.

[0200] The interface modification layer slurry is coated on the surface of the negative electrode current collector copper foil, and after drying and welding the negative electrode tab, the negative electrode sheet is obtained.

[0201] Comparative Example 2

[0202] The preparation method of the battery is similar to that of Example 5, except that in the preparation of the negative electrode plate, the thickness of the insulating coating is 5.0 μm.

[0203] Comparative Example 3

[0204] The preparation method of the battery is similar to that of Example 5, except that in the preparation of the negative electrode plate, the thickness of the insulating coating is 27.2 μm.

[0205] Comparative Example 4

[0206] The preparation method of the battery is similar to that of Example 1, except that in the preparation of the negative electrode sheet, the thickness of the insulating coating is 130.0 μm.

[0207] Performance Testing

[0208] (1) Cyclic performance test

[0209] At 25°C, the prepared battery was charged at a constant current of 1C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After standing for 5 minutes, the battery was discharged at a constant current of 1C to a voltage of 2.0V. This constitutes one charge-discharge cycle, and the discharge capacity is the discharge capacity after the first cycle. The battery was cycled 500 times in this manner.

[0210] Battery capacity retention after 500 cycles = discharge capacity after 500 cycles / discharge capacity after the first cycle.

[0211] (2) Sodium precipitation test

[0212] At 25°C, the prepared battery was charged at a constant current of 5C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After standing for 5 minutes, the battery was discharged at a constant current of 1C to a voltage of 2.0V. This is a charge and discharge cycle. The battery was cycled 10 times in the above manner, then charged at a constant current of 5C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. The battery was disassembled to observe the sodium precipitation at the junction of the interface modification layer and the insulating coating at the negative terminal.

[0213] The degree of sodium precipitation can be determined according to the following circumstances.

[0214] Failure: The width of the area where sodium dendrites are precipitated is greater than or equal to 80% of the width of the insulating coating.

[0215] Severe precipitation: The width of the area where sodium dendrites are precipitated is greater than or equal to 50% but less than 80% of the width of the insulating coating.

[0216] Moderate precipitation: The width of the region where sodium dendrites are precipitated is greater than or equal to 20% but less than 50% of the width of the insulating coating.

[0217] Slight precipitation: The width of the area where sodium dendrites are precipitated is greater than or equal to 5% but less than 20% of the width of the insulating coating.

[0218] No precipitation: The width of the area where sodium dendrites are precipitated is less than 5% of the width of the insulating coating.

[0219] The test results are shown in Tables 1 and 2. In Table 2, since no insulating coating is provided on the negative electrode current collector of Comparative Example 1, "failure" means that the width of the region where sodium dendrites are precipitated is greater than 5 mm.

[0220] Table 1

[0221] Table 2

[0222] It can be seen from the test results of Examples 1 to 5 and Comparative Examples 2 to 3 that configuring the thickness of the insulating coating to be greater than 1.1 times the theoretical thickness of the metal deposition layer deposited when the battery is charged and the sum of the thickness of the interface modification layer can reduce the degree of sodium precipitation on the surface of the negative electrode, thereby effectively reducing the internal short circuit problem of the battery caused by dendrite growth at the negative terminal position, and can also improve the cycle performance of the battery.

[0223] The test results of Examples 1 to 5 and Comparative Example 4 show that configuring the thickness of the insulating coating to be less than the theoretical thickness of the metal deposit layer deposited during battery charging, the thickness of the positive electrode active material layer, and the thickness of the interface modification layer can improve the battery's cycling performance. This is because when the thickness of the insulating coating is configured to be greater than the sum of the theoretical thickness of the metal deposit layer deposited during battery charging, the thickness of the positive electrode active material layer, and the thickness of the interface modification layer, misalignment occurs when the pole pieces are stacked, thereby lengthening the ion transmission path between the positive and negative electrodes, thereby affecting battery performance.

[0224] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising a positive electrode sheet and a negative electrode sheet, wherein: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector; The negative electrode plate comprises a negative electrode current collector and two insulating coatings arranged on the surface of the negative electrode current collector close to the positive electrode plate, the distance between the two insulating coatings is greater than the width of the positive electrode active material layer, and the two insulating coatings are not directly opposite to the positive electrode active material layer; The negative electrode plate may further include an interface modification layer disposed on the negative electrode current collector and between the two insulating coatings; The thickness of the insulating coating is configured to be greater than 1.1 times the theoretical thickness of the metal deposition layer deposited when the battery cell is charged and the thickness of an optional interface modification layer, and less than the sum of the theoretical thickness of the metal deposition layer deposited when the battery cell is charged, the thickness of the positive electrode active material layer and the thickness of an optional interface modification layer.

2. The battery cell according to claim 1, wherein: The thickness of the insulating coating is configured to be greater than 1.25 times the theoretical thickness of the metal deposition layer deposited when the battery cell is charged and the thickness of an optional interface modification layer, and less than the sum of the theoretical thickness of the metal deposition layer deposited when the battery cell is charged, the thickness of the positive electrode active material layer and the thickness of an optional interface modification layer.

3. The battery cell according to any one of claims 1 to 2, wherein: The capacity per unit area of ​​the positive electrode active material layer is recorded as M mAh / cm 2 The theoretical gram capacity of the metal deposited when the battery cell is charged is recorded as C a mAh / g, the theoretical density of the metal deposited when the battery cell is charged is recorded as ρ a g / cm 3 , then the theoretical thickness of the metal deposition layer deposited when the battery cell is charged is (10000×M) / (C a ×ρ a ), unit is μm.

4. The battery cell according to any one of claims 1 to 3, wherein: The density of the insulating coating is greater than or equal to 20%, and can be optionally 50%-80%.

5. The battery cell according to any one of claims 1 to 4, wherein: Inorganic insulating fillers are dispersed in the insulating coating.

6. The battery cell according to claim 5, wherein: The insulating coating satisfies at least one of the following conditions (1) to (5): (1) The volume distribution particle size Dv50 of the inorganic insulating filler is less than or equal to 2 μm, and can be selected to be 0.001 μm-0.5 μm; (2) The thickness of the insulating coating is recorded as H0 μm, the volume distribution particle size Dv50 of the inorganic insulating filler is recorded as D0 μm, and H0 / D0≥5; (3) The tap density of the inorganic insulating filler is 0.8 g / cm 3 -2.0g / cm 3 , optional 0.95g / cm 3 -1.40g / cm 3 ; (4) The specific surface area of ​​the inorganic insulating filler is 3m 2 / g-25m 2 / g, optional 7m 2 / g-20m 2 / g; (5) The surface density of the insulating coating is 0.06 mg / cm 2 -13.0mg / cm 2 , optional 0.10mg / cm 2 -3.50mg / cm 2 .

7. The battery cell according to any one of claims 1 to 6, wherein: The two insulating coatings are respectively a first insulating coating and a second insulating coating, the first insulating coating is located on the negative electrode ear side of the negative electrode plate, the width of the first insulating coating is recorded as W1, the width of the second insulating coating is recorded as W2, W1 is greater than or equal to 0.5 mm, W2 is greater than or equal to 0.5 mm, and W1 / W2 is greater than or equal to 0.5, which can be selected as 1-3; Optionally, W1 is 0.5 mm-20 mm, optionally 1 mm-15 mm; and / or, Optionally, W2 is 0.5mm-10mm, optionally 1mm-5mm.

8. The battery cell according to any one of claims 1 to 7, wherein: The insulating coating layer includes a first sublayer and a second sublayer located between the first sublayer and the negative electrode current collector, wherein the first sublayer does not contain any inorganic insulating filler, and the second sublayer contains any inorganic insulating filler.

9. The battery cell according to any one of claims 1 to 7, wherein: The insulating coating includes a first sublayer and a second sublayer located between the first sublayer and the negative electrode current collector, the first sublayer is dispersed with an inorganic insulating filler, the second sublayer is dispersed with an inorganic insulating filler, and the weight content of the inorganic insulating filler in the first sublayer is less than the weight content of the inorganic insulating filler in the second sublayer.

10. The battery cell according to any one of claims 8 to 9, wherein: The thickness ratio of the first sublayer to the second sublayer is (0.1-0.9):1, and can be optionally (0.2-0.5):

1.

11. The battery cell according to any one of claims 1 to 10, wherein: The width of the interface modification layer is greater than the width of the positive electrode active material layer.

12. The battery cell according to any one of claims 1 to 11, wherein: The battery cell further includes a separator, which is located between the positive electrode sheet and the negative electrode sheet. The bonding force between the insulating coating and the isolation film is greater than the bonding force between the interface modification layer and the isolation film; and / or, The bonding force between the insulating coating and the isolation film is 3N / m-50N / m, and can be optionally 4N / m-25N / m.

13. The battery cell according to any one of claims 1 to 12, wherein: The two insulating coatings are respectively a first insulating coating and a second insulating coating. The first insulating coating is located on the negative electrode ear side of the negative electrode plate. The width of the first insulating coating is recorded as W1, the width of the second insulating coating is recorded as W2, and the width of the interface modification layer is recorded as W a , W1 / W a 0.01-0.1, optionally 0.01-0.05; and / or, W2 / W a It is 0.01-0.1, and can be optionally 0.01-0.

05.

14. The battery cell according to any one of claims 1 to 13, wherein: The width of the interface modification layer is 50 mm-200 mm, and can be 70 mm-150 mm; and / or, The thickness of the interface modification layer is 1 μm-50 μm, and can be optionally 1 μm-20 μm.

15. The battery cell according to any one of claims 1 to 14, wherein: The interface modification layer is dispersed with an alkali metal affinity material, and the alkali metal affinity material is a sodium affinity material or a lithium affinity material.

16. The battery cell according to any one of claims 1 to 15, wherein: The battery cell is a negative electrode-free sodium battery cell or a negative electrode-free lithium battery cell.

17. A battery comprising the battery cell according to any one of claims 1 to 16.

18. An electrical device comprising the battery according to claim 17, wherein the battery is used to provide electrical energy.

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