Electrode assembly, battery and electric device

Abstract

The invention relates to an electrode assembly, a battery and a power utilization device, the electrode assembly comprises a positive pole piece, a negative pole piece and an isolating membrane arranged between the positive pole piece and the negative pole piece, and the negative pole piece comprises a negative current collector, a negative functional layer and an alkali metal layer arranged on at least one side of the negative current collector; the negative electrode current collector comprises a negative electrode center part and a negative electrode edge part arranged outside the negative electrode center part in a surrounding manner; the alkali metal layer is at least arranged opposite to the negative electrode center part; the negative electrode functional layer is at least arranged opposite to at least part of the negative electrode edge part, is connected with the negative electrode edge part and the isolating membrane, and comprises a polymer. The problem that the cycle performance of the battery is poor can be solved, and the cycle performance of the battery can be improved.

Description

Technical Field

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

[0002] Batteries have characteristics such as high capacity and long life, and thus are widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools, etc. Due to the great progress of batteries, higher requirements are put forward for the performance of batteries. In order to improve the performance of batteries, the electrode assemblies inside the batteries are usually optimized and improved.

[0003] However, at present, when the electrode assembly is applied to a battery, the reliability of the battery during use is still poor. Summary of the Invention

[0004] The present application provides an electrode assembly, a battery, and an electrical device, and the cycle performance of the battery described in the present application can be improved.

[0005] In a first aspect, an embodiment of the present application provides an electrode assembly. The electrode assembly includes a positive electrode tab, a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab. The negative electrode tab includes a negative current collector, a negative functional layer, and an alkali metal layer disposed on at least one side of the negative current collector. The negative current collector includes a negative central portion and a negative edge portion surrounding the outside of the negative central portion. The alkali metal layer is disposed opposite to at least the negative central portion; the negative functional layer is disposed opposite to at least a part of the negative edge portion, and the negative functional layer connects the negative edge portion and the separator, and the negative functional layer includes a polymer.

[0006] Thus, in the embodiment of the present application, a negative functional layer is provided at the edge portion of the negative electrode tab. Since the negative functional layer contains a polymer, it has adhesiveness and can bond the separator, so that the negative functional layer and the separator are connected as a whole. Even if the phenomenon of alkali metal pulverization occurs during the cyclic charging of the battery cell, the negative functional layer and the separator can play a certain role in blocking the alkali metal, reducing the risk of alkali metal escaping, thereby improving the reliability of the battery cell during use.

[0007] In some embodiments, the alkali metal layer is disposed opposite to the negative central portion, and the negative functional layer surrounds the outside of the alkali metal layer.

[0008] Thus, in the embodiment of the present application, the negative functional layer surrounds the outside of the alkali metal layer. The negative functional layer connects the negative edge portion and the separator, and basically confines the alkali metal layer within the area of the negative electrode tab, reducing the risk of alkali metal escaping, thereby improving the reliability of the battery cell during use.

[0009] In some embodiments, the alkali metal layer includes a first metal portion and a second metal portion. The first metal portion is disposed opposite to the center portion of the negative electrode. The second metal portion is disposed around the first metal portion. The second metal portion is located between the edge portion of the negative electrode and the negative electrode functional layer, and connects the edge portion of the negative electrode and the negative electrode functional layer.

[0010] Thus, in the embodiments of the present application, one side of the negative electrode functional layer is connected to the edge portion of the negative electrode through the second metal portion, and the other side of the negative electrode functional layer is connected to the separator, thereby substantially limiting the alkali metal layer within the negative electrode tab region, reducing the risk of alkali metal escape, and thus improving the use reliability of the battery cell.

[0011] In some embodiments, the negative electrode tab further includes a negative electrode tab ear. The negative electrode tab ear is located on one side of the negative electrode current collector along the first direction, and is connected to the edge portion of the negative electrode. The first direction is perpendicular to the thickness direction of the negative electrode tab. The negative electrode functional layer extends at least to the connection portion between the negative electrode tab ear and the edge portion of the negative electrode.

[0012] Thus, in the embodiments of the present application, by providing the negative electrode functional layer at the connection portion, the connection stability of the connection portion can be improved, thereby improving the overall structural stability of the negative electrode tab and further improving the use reliability of the battery cell.

[0013] In some embodiments, the negative electrode functional layer includes a first sub-layer and a second sub-layer. The first sub-layer is disposed at least on one side of the edge portion of the negative electrode along the thickness direction of the negative electrode tab. The second sub-layer is disposed at least on the other side of the edge portion of the negative electrode along the thickness direction of the negative electrode tab. The end portion of the second sub-layer facing away from the negative electrode tab ear is connected to the end portion of the first sub-layer facing away from the negative electrode tab ear.

[0014] In some embodiments, along the thickness direction of the electrode assembly, the projected contour of the positive electrode tab is located within the projection of the negative electrode functional layer.

[0015] Thus, in the embodiments of the present application, through the connection of the two end portions, the connection strength between the negative electrode functional layer and the edge portion of the negative electrode is higher, the negative electrode functional layer is not easily separated from the edge portion of the negative electrode, the structural stability of the negative electrode tab is further improved, and the ability of the end portion of the negative electrode functional layer to reduce metallic lithium is further enhanced. The use reliability of the battery cell can be further improved.

[0016] In some embodiments, the positive electrode tab includes a positive electrode current collector, a positive electrode functional layer, and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode current collector includes a positive electrode center portion and a positive electrode edge portion disposed around the positive electrode center portion. Along the thickness direction of the electrode assembly, the projection of the positive electrode edge portion and the projection of the negative electrode edge portion at least partially overlap. The positive electrode film layer is disposed at least opposite to the positive electrode center portion. The positive electrode film layer includes positive electrode active materials. The positive electrode functional layer is disposed at least opposite to at least a part of the positive electrode edge portion, and connects the positive electrode edge portion and the separator. The positive electrode functional layer includes a polymer.

[0017] Thus, in the embodiments of the present application, the positive electrode functional layer can block free metallic lithium, further reducing the risk of contact between metallic lithium and the positive electrode plate, and improving the reliability of use of the battery cell.

[0018] In some embodiments, the positive electrode film layer is disposed opposite to the central portion of the positive electrode, and the positive electrode functional layer is disposed around the positive electrode film layer. The positive electrode functional layer can block free metallic lithium, further reducing the risk of contact between metallic lithium and the positive electrode plate, and improving the reliability of use of the battery cell.

[0019] In some embodiments, the positive electrode film layer includes a first positive electrode portion and a second positive electrode portion. The first positive electrode portion is disposed opposite to the central portion of the positive electrode; the second positive electrode portion is disposed around the first positive electrode portion, and the second positive electrode portion is located between the edge portion of the positive electrode and the positive electrode functional layer and connects the edge portion of the positive electrode and the positive electrode functional layer.

[0020] Thus, in the embodiments of the present application, one side of the positive electrode functional layer is connected to the edge portion of the positive electrode through the second positive electrode portion, and the other side of the positive electrode functional layer is connected to the separator. The positive electrode functional layer can block free metallic lithium, further reducing the risk of contact between metallic lithium and the positive electrode plate, and improving the reliability of use of the battery cell.

[0021] In some embodiments, the positive electrode plate further includes a positive electrode tab, and the positive electrode tab is located on one side of the positive electrode current collector along the first direction and is connected to the edge portion of the positive electrode. The first direction is perpendicular to the thickness direction of the negative electrode plate; the positive electrode functional layer extends at least to the connection portion between the positive electrode tab and the edge portion of the positive electrode.

[0022] Thus, in the embodiments of the present application, by providing the positive electrode functional layer at the connection portion, the connection stability of the connection portion can be improved, thereby enhancing the overall structural stability of the positive electrode plate and further enhancing the reliability of use of the battery cell. Moreover, the positive electrode functional layer can further block free metallic lithium, reducing the risk of contact between metallic lithium and the positive electrode plate, and improving the reliability of use of the battery cell.

[0023] In some embodiments, along the thickness direction of the electrode assembly, the projection of the negative electrode plate is located within the projection of the separator. The size of the negative electrode plate can be less than or equal to the size of the separator, so that the separator can play a good role in isolating the positive electrode plate and the negative electrode plate.

[0024] In some embodiments, the size of the negative electrode functional layer along the first direction is 0.1 mm to 10 mm, and the first direction is perpendicular to the thickness direction of the negative electrode plate. When the size of the negative electrode functional layer along the first direction is within the above range, it is easy to set the negative electrode functional layer in the process, and the reliability of use of the battery cell can be effectively improved; moreover, the influence on the energy density of the battery cell is relatively small.

[0025] In some embodiments, the size of the negative electrode functional layer in the second direction is 0.1 mm to 10 mm, and the second direction is perpendicular to the thickness direction of the negative electrode plate. When the size of the negative electrode functional layer in the second direction is within the above range, it is easy to set the negative electrode functional layer in the process, and the service reliability of the battery cell can be effectively improved; moreover, the influence on the energy density of the battery cell is relatively small.

[0026] In some embodiments, the thickness H of the negative electrode functional layer satisfies the following formula: H = (x 1 ×y 1 +x 2 ×y 2 ) / (z×y 2 );

[0027] In the formula,

[0028] x 1 g / cm 2 represents the mass of the positive active material of the positive electrode film layer per unit area on one side of the positive electrode plate;

[0029] x 2 g / cm 2 represents the mass of the alkali metal in the alkali metal layer per unit area on one side;

[0030] y 1 mAh / g represents the theoretical gram capacity of the positive active material;

[0031] y 2 mAh / g represents the theoretical gram capacity of the alkali metal;

[0032] z g / cm 3 represents the deposition density of the alkali metal, 0.16 ≤ z ≤ 0.534.

[0033] Thus, when the thickness of the negative electrode functional layer in the embodiments of the present application satisfies the above formula, the negative electrode functional layer can effectively bond the negative electrode current collector and the separator, and a reserved space can be provided between the negative electrode current collector and the separator for the volume expansion of the negative electrode plate, reducing the risk of lithium metal pulverization due to volume expansion, and improving the overall structural stability of the electrode assembly.

[0034] In some embodiments, the electrode assembly further satisfies at least one of the following conditions,

[0035] (1) The adhesion of the negative electrode functional layer ≥ 0.15 N / mm;

[0036] (2) The ionic conductivity of the negative electrode functional layer is less than or equal to 1×10 -5 S·m.

[0037] In some embodiments, the polymer includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, lithium polyacrylate, sodium polyacrylate, polytetrafluoroethylene, polyimide, polyurethane, block copolymer, and the block copolymer includes at least one of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer; optionally, based on the total mass of the negative electrode functional layer, the mass content of the polymer is 8% to 100%. The above polymers have relatively high adhesiveness and relatively low ionic conductivity.

[0038] In some embodiments, the negative electrode functional layer further includes inorganic particles, and the inorganic particles include Al 2 O 3 、γ-AlOOH、SiO 2 、SiC、Si 3 N 4 、AlN、BN、Al 4 C 3 and at least one of them; optionally, based on the total mass of the negative electrode functional layer, the mass content of the inorganic particles is 10% to 92%. The inorganic particles can improve the hardness of the negative electrode functional layer, further relieve the shear stress caused by the edge of the positive electrode plate to the negative electrode plate, and improve the structural stability of the negative electrode plate.

[0039] In some embodiments, the alkali metal layer includes at least one of lithium metal and sodium metal; optionally, the alkali metal layer includes lithium metal.

[0040] In a second aspect, the present application also provides a battery, which includes an electrode assembly according to any one of the embodiments of the first aspect of the present application.

[0041] In a third aspect, the present application also provides an electrical device, which includes a battery according to any one of the embodiments of the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0043] Figure 1 is a schematic diagram of an embodiment of the electrode assembly of the present application.

[0044] Figure 2 is a schematic diagram of another embodiment of the electrode assembly of the present application.

[0045] Figure 3 It is a schematic diagram of an embodiment of the negative electrode sheet of the present application.

[0046] Figure 4 It is a schematic diagram of another embodiment of the negative electrode sheet of the present application.

[0047] Figure 5 It is a schematic diagram of yet another embodiment of the negative electrode sheet of the present application.

[0048] Figure 6 It is a schematic diagram of yet another embodiment of the negative electrode sheet of the present application.

[0049] Figure 7 It is a schematic diagram of yet another embodiment of the electrode assembly of the present application.

[0050] Figure 8 It is a schematic diagram of an embodiment of the positive electrode sheet of the electrode assembly of the present application.

[0051] Figure 9 It is a schematic diagram of another embodiment of the positive electrode sheet of the electrode assembly of the present application.

[0052] Figure 10 It is a schematic diagram of yet another embodiment of the positive electrode sheet of the electrode assembly of the present application.

[0053] Figure 11 It is a schematic diagram of an embodiment of the battery cell of the present application.

[0054] Figure 12 is Figure 11 exploded schematic diagram of the embodiment of the battery cell.

[0055] Figure 13 It is a schematic diagram of an embodiment of the battery module of the present application.

[0056] Figure 14 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0057] Figure 15 is Figure 14 exploded schematic diagram of the embodiment of the battery pack shown.

[0058] Figure 16 It is a schematic diagram of an embodiment of an electrical device including the battery cell of the present application as a power source.

[0059] The drawings are not necessarily drawn to actual scale.

[0060] The description of the reference numerals is as follows:

[0061] X, the first direction; Y, the thickness direction;

[0062] 1. Battery pack; 2. Upper box body; 3. Lower box body; 4. Battery module;

[0063] 5. Battery cell; 51. Shell; 52. Electrode assembly;

[0064] 53. Cover plate;

[0065] 6. Electrical device;

[0066] 7. Negative electrode tab;

[0067] 71. Negative electrode current collector; 711. Negative electrode central part; 712. Negative electrode edge part;

[0068] 72. Alkali metal layer; 721. First metal part; 722. Second metal part;

[0069] 73. Negative electrode functional layer; 731. First sub-layer; 732. Second sub-layer;

[0070] 74. Negative electrode tab;

[0071] 8. Positive electrode tab;

[0072] 81. Positive electrode current collector; 811. Positive electrode central part; 812. Positive electrode edge part;

[0073] 82. Positive electrode film layer; 821. First positive electrode part; 822. Second positive electrode part;

[0074] 83. Positive electrode functional layer;

[0075] 84. Positive electrode tab;

[0076] 9. Separator. Detailed implementation manners

[0077] Hereinafter, embodiments of the electrode assembly, battery, and electrical device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0078] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0079] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0080] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0081] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, if a method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0082] The battery cell includes an electrode assembly and an electrolyte, a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode film layer containing a positive electrode active material. The positive electrode active material is a donor that provides active ions such as active ions and sodium ions for the battery cell. The negative electrode plate includes a negative electrode film layer containing a negative electrode active material. The negative electrode active material can act as an acceptor for active ions. The electrolyte provides a migration path for active ions between the positive electrode plate and the negative electrode plate.

[0083] Since the theoretical specific capacity of alkali metals is relatively high, and they have relatively low density and relatively negative electrode potential, using alkali metals as the negative electrode active material can significantly improve the energy density of a single battery cell.

[0084] During the charging process of a single battery cell, active ions obtain electrons from the external circuit and migrate to the negative electrode plate, where they are deposited on the negative electrode plate in the form of particles. However, the active ions may deposit unevenly on the negative electrode plate, resulting in the local generation of a large amount of alkali metal on the negative electrode plate, thus forming alkali metal dendrites. As the alkali metal dendrites continue to grow, it may lead to the pulverization of the alkali metal. The pulverized alkali metal is likely to escape from the negative electrode plate and may even escape to the positive electrode plate, thereby causing a short circuit and reducing the reliability of the single battery cell; moreover, the escape of alkali metal to the positive electrode plate may react chemically with the positive electrode current collector in the positive electrode plate, leading to heat release in the system, which may trigger thermal runaway of the single battery cell and deteriorate the reliability of the single battery cell.

[0085] In view of the above problems, an electrode assembly is proposed in the embodiments of the present application. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. A negative electrode functional layer is provided at the edge portion of the negative electrode plate. Since the negative electrode functional layer contains a polymer, it has adhesiveness and can bond the separator, so that the negative electrode functional layer and the separator are connected as a whole. Even when the pulverization of alkali metal occurs during the cyclic charging process of the single battery cell, the negative electrode functional layer and the separator can play a certain role in blocking the alkali metal, reducing the risk of alkali metal escaping, and thus improving the reliability of the single battery cell. Next, the technical solutions of the present application will be described in detail.

[0086] Electrode assembly

[0087] In a first aspect, an electrode assembly is proposed in the embodiments of the present application.

[0088] As Figure 1 shown, the electrode assembly 52 includes a positive electrode plate 8, a negative electrode plate 7, and a separator 9 disposed between the positive electrode plate 8 and the negative electrode plate 7. The negative electrode plate 7 includes a negative electrode current collector 71, a negative electrode functional layer 73, and an alkali metal layer 72 disposed on at least one side of the negative electrode current collector 71. The negative electrode current collector 71 includes a negative electrode central portion 711 and a negative electrode edge portion 712 disposed around the outside of the negative electrode central portion 711. The alkali metal layer 72 is disposed at least opposite to the negative electrode central portion 711. The negative electrode functional layer 73 is disposed at least opposite to at least a part of the negative electrode edge portion 712, and the negative electrode functional layer 73 connects the negative electrode edge portion 712 and the separator 9. The negative electrode functional layer 73 includes a polymer.

[0089] The electrode assembly 52 can be a wound electrode assembly, a stacked electrode assembly, or other forms of electrode assemblies. The wound electrode assembly is formed by winding the positive electrode sheet 8, the separator 9, and the negative electrode sheet 7 in sequence. The outer shape structure of the wound electrode assembly can be a flat structure or a cylindrical structure, etc. The stacked electrode assembly is formed by stacking the positive electrode sheet 8, the separator 9, and the negative electrode sheet 7 in sequence, and its outer shape structure can be a cuboid structure. When the electrode assembly 52 is a stacked structure, the thickness direction of the electrode assembly 52 is parallel to the thickness direction Y of the negative electrode sheet 7 and the thickness direction of the positive electrode sheet 8. Figure 1 The structural schematic diagram of the stacked electrode assembly is shown.

[0090] The negative electrode sheet 7 includes a negative current collector 71, an alkali metal layer 72, and a negative electrode functional layer 73. The negative current collector 71 includes two sides opposite to each other along the thickness direction Y of the negative electrode sheet 7. An alkali metal layer 72 can be provided on one of the two sides, or alkali metal layers 72 can be provided on both sides. Figure 1 The Y direction shown in it is the thickness direction Y of the negative electrode sheet 7. Since the electrode assembly 52 is a stacked structure, in this case, the thickness direction of the electrode assembly 52 is parallel to the thickness direction Y of the negative electrode sheet 7.

[0091] The negative current collector 71 can include a negative electrode central portion 711 and a negative electrode edge portion 712. The negative electrode edge portion 712 is disposed around the negative electrode central portion 711. The definitions of the negative electrode central portion 711 and the negative electrode edge portion 712 are to distinguish different regions of the negative current collector 71, and there may be no obvious boundary between the two. For example, the negative current collector 71 is made of copper foil, and the copper foil is an integral structure.

[0092] The alkali metal layer 72 is at least disposed opposite to the negative electrode central portion 711. It can be understood that along the thickness direction Y of the negative electrode sheet 7, the projection of the negative electrode central portion 711 is located within the projection of the alkali metal layer 72, that is, the alkali metal layer 72 at least covers the negative electrode central portion 711. The alkali metal layer 72 can be only disposed on the negative electrode central portion 711 to cover the negative electrode central portion 711; or on the basis of being disposed on the negative electrode central portion 711 to cover the negative electrode central portion 711, it can also be disposed on at least part of the negative electrode edge portion 712 to cover at least part of the negative electrode edge portion 712. During the charging process, the active ions from the positive electrode sheet 8 are transferred from the electrolyte to the liquid layer on the surface of the alkali metal layer 72 through liquid-phase mass transfer. The active ions transferred to the alkali metal layer 72 gain electrons on the surface of the alkali metal layer 72 and deposit to form alkali metal. During the discharging process, the alkali metal layer 72 can provide active ions for the system and can supplement the content of active ions in the system.

[0093] The negative electrode functional layer 73 is disposed at least opposite to at least a part of the negative electrode edge portion 712. The negative electrode functional layer 73 may cover a part of the structure of the negative electrode edge portion 712 and be disposed opposite to a part of the structure of the negative electrode edge portion 712; alternatively, the negative electrode functional layer 73 may cover the negative electrode edge portion 712 and be disposed opposite to the negative electrode edge portion 712. In this case, it can be understood that the negative electrode functional layer 73 completely covers the negative electrode edge portion 712; alternatively, in addition to covering the negative electrode edge portion 712 and being disposed opposite to the negative electrode edge portion 712, the negative electrode functional layer 73 may also cover a part of the negative electrode tab 74 and be disposed opposite to a part of the negative electrode tab 74; it can be understood that along the thickness direction Y of the negative electrode plate 7, the projection of the negative electrode edge portion 712 and the projection of the negative electrode functional layer 73 at least partially overlap. The negative electrode plate 7 is generally a rectangular parallelepiped sheet structure. The negative electrode edge portion 712 can be considered as the four edge portions of the negative electrode plate 7. The negative electrode functional layer 73 may cover one edge portion, two edge portions, three edge portions or four edge portions of the four edge portions; the negative electrode functional layer 73 may further extend to the negative electrode tab 74 and cover a part of the structure of the negative electrode tab 74.

[0094] Since the negative electrode functional layer 73 contains a polymer, it has adhesiveness and can bond the separator 9, so that the negative electrode functional layer 73 and the separator 9 are connected as a whole. Even when the pulverization of alkali metal occurs during the cyclic charging of the battery cell, the negative electrode functional layer 73 and the separator 9 can play a role in blocking alkali metal to a certain extent, reducing the possibility of the pulverized alkali metal escaping from the negative electrode plate 7 and reducing the risk of alkali metal escaping, thereby improving the use reliability of the battery cell.

[0095] In some embodiments, the alkali metal layer 72 includes at least one of lithium metal and sodium metal. For example, the alkali metal layer 72 includes lithium metal, that is, the alkali metal layer 72 is a lithium metal layer. Alternatively, the alkali metal layer 72 includes sodium metal, that is, the alkali metal layer 72 is a sodium metal layer. Alternatively, the alkali metal layer 72 includes lithium metal and sodium metal, and the alkali metal layer 72 is a lithium-sodium metal layer. The theoretical specific capacity of lithium metal is relatively high, and it has a relatively low density and a relatively negative electrode potential. Using lithium metal as the negative electrode active material can significantly improve the energy density of the battery cell.

[0096] [Negative electrode plate]

[0097] In the embodiments of the present application, the set area of the alkali metal layer 72 can be flexibly set according to production requirements. For example, the alkali metal layer 72 may partially cover the negative electrode current collector 71. Specifically, it may only cover the negative electrode central portion 711; it may also completely cover the negative electrode current collector 71; the setting manner of the negative electrode functional layer 73 can be adaptively adjusted according to the set area of the alkali metal layer 72. The alkali metal layer 72 can be formed on the negative electrode current collector 71 by means of roll pressing, electroplating or evaporation plating.

[0098] As Figure 1 and Figure 2 shown, in some embodiments, the alkali metal layer 72 is disposed opposite to the center portion 711 of the negative electrode, and the negative electrode functional layer 73 is disposed around the alkali metal layer 72. When the alkali metal layer 72 is disposed on and covers the center portion 711 of the negative electrode, the negative electrode functional layer 73 is disposed around the alkali metal layer 72, and the negative electrode functional layer 73 connects the negative electrode edge portion 712 and the separator 9, basically restricting the alkali metal layer 72 within the region of the negative electrode tab 7, reducing the risk of alkali metal escaping, thereby improving the reliability of use of the battery cell.

[0099] As Figures 2 to 4 shown, in some other embodiments, the alkali metal layer 72 includes a first metal portion 721 and a second metal portion 722. The first metal portion 721 is disposed opposite to the center portion 711 of the negative electrode; the second metal portion 722 is disposed around the first metal portion 721 and is connected to the first metal portion 721. The second metal portion 722 is located between the negative electrode edge portion 712 and the negative electrode functional layer 73 and connects the negative electrode edge portion 712 and the negative electrode functional layer 73.

[0100] The definitions of the first metal portion 721 and the second metal portion 722 are for distinguishing different regions of the alkali metal layer 72, and there may be no obvious boundary therebetween. For example, the alkali metal is coated on the negative electrode current collector 71 to form the alkali metal layer 72, and the alkali metal layer 72 is an integral structure. The first metal portion 721 is disposed on and covers the center portion 711 of the negative electrode, the second metal portion 722 is disposed around the first metal portion 721 and is connected to the first metal portion 721. The second metal portion 722 is disposed on at least a part of the negative electrode edge portion 712 and covers at least a part of the negative electrode edge portion 712. The negative electrode functional layer 73 covers the second metal portion 722, and one side of the negative electrode functional layer 73 is connected to the negative electrode edge portion 712 through the second metal portion 722, and the other side of the negative electrode functional layer 73 is connected to the separator 9, thereby basically restricting the alkali metal layer 72 within the region of the negative electrode tab 7, reducing the risk of alkali metal escaping, thereby improving the reliability of use of the battery cell.

[0101] In some embodiments, the negative electrode tab 7 includes a negative electrode current collector 71 and a negative electrode tab 74. The negative electrode tab 74 is located on one side of the negative electrode current collector 71 along the first direction X, and the negative electrode tab 74 is connected to the negative electrode edge portion 712. The first direction X is perpendicular to the thickness direction Y of the negative electrode tab 7. In the embodiments of the present application, the first direction X can be the width direction or the length direction of the negative electrode tab 7. At least a part of the negative electrode tab 74 is not coated with a negative electrode active material such as an alkali metal. The negative electrode current collector 71 and the negative electrode tab 74 can be integrally formed. For example, a one-piece copper foil is sheared to form a negative electrode tab 74 protruding from the negative electrode current collector 71. Of course, the negative electrode current collector 71 and the negative electrode tab 74 can also be separately formed and then connected.

[0102] As Figure 5 shown, in some embodiments, the negative electrode functional layer 73 at least extends to the connection portion of the negative electrode tab 74 and the negative electrode edge portion 712. Since the connection stability of the connection portion of the negative electrode tab 74 and the negative electrode edge portion 712 is relatively poor, by providing the negative electrode functional layer 73 at the connection portion, the connection stability of the connection portion can be improved, thereby enhancing the overall structural stability of the negative electrode tab 7 and further enhancing the use reliability of the battery cell.

[0103] Furthermore, the negative electrode functional layer 73 can further extend to the negative electrode tab 74 and cover a part of the negative electrode tab 74 close to the negative electrode edge portion 712, which can further enhance the overall structural stability of the negative electrode tab 7 and can further reduce the risk of lithium metal escaping.

[0104] The negative electrode functional layer 73 can be provided on one side of the negative electrode current collector 71 or on both sides of the negative electrode current collector 71. For example, when the alkali metal layer 72 is provided on one side of the negative electrode current collector 71, the negative electrode functional layer 73 can be correspondingly provided on this side of the negative electrode current collector 71; for another example, when the alkali metal layer 72 is provided on both sides of the negative electrode current collector 71, the negative electrode functional layer 73 can be provided on one of the two sides of the negative electrode current collector 71, and the negative electrode functional layer 73 can also be provided on both sides of the negative electrode current collector 71. Providing the negative electrode functional layer 73 on both sides can more effectively slow down the escape of the alkali metal, thereby enhancing the use reliability of the battery cell.

[0105] As Figure 6 shown, when the negative electrode functional layer 73 is provided on both sides of the negative electrode current collector 71, it can be considered that the negative electrode functional layer 73 includes two layers. One layer is the first sub-layer 731, and the first sub-layer 731 is at least provided on one side of the negative electrode edge portion 712 along the thickness direction Y of the negative electrode tab 7; the other layer is the second sub-layer 732, and the second sub-layer 732 is at least provided on the other side of the negative electrode edge portion 712 along the thickness direction Y of the negative electrode tab 7.

[0106] In some embodiments, the end of the second sub-layer 732 facing away from the negative electrode tab 74 is connected to the end of the first sub-layer 731 facing away from the negative electrode tab 74. Through the connection of their ends, the connection strength between the negative electrode functional layer 73 and the negative electrode edge portion 712 is higher, the negative electrode functional layer 73 is not easily separated from the negative electrode edge portion 712, the structural stability of the negative electrode plate 7 is further improved, and the ability of the end of the negative electrode functional layer 73 to reduce metallic lithium is further enhanced. The use reliability of the battery cell can be further improved.

[0107] Optionally, the dimension of the negative electrode functional layer 73 in the first direction X is 0.1 mm to 10 mm; it can be optionally 1 mm to 4 mm. When the dimension of the negative electrode functional layer 73 in the first direction X is within the above range, it is easy to set the negative electrode functional layer 73 in terms of process, and the use reliability of the battery cell can be effectively improved; moreover, the influence on the energy density of the battery cell is relatively small.

[0108] The negative electrode plate 7 is usually a rectangular parallelepiped sheet structure. The negative electrode edge portion 712 can be considered as the four edge portions of the negative electrode plate 7. When the negative electrode functional layer 73 can cover two, three or four of the four edge portions, the dimension of the negative electrode functional layer 73 in the first direction X is the dimension of the negative electrode functional layer 73 covering one of the edge portions. When the negative electrode functional layer 73 can cover one of the four edge portions, the dimension of the negative electrode functional layer 73 in the first direction X is the dimension of the edge portion covered by the negative electrode functional layer 73.

[0109] Exemplarily, the size of the negative electrode functional layer 73 in the first direction X can be 0.1 mm, 0.2 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4.0 mm, 4.2 mm, 4.5 mm, 4.8 mm, 5.0 mm, 5.2 mm, 5.5 mm, 5.8 mm, 6.0 mm, 6.2 mm, 6.5 mm, 6.8 mm, 7.0 mm, 7.2 mm, 7.5 mm, 7.8 mm, 8.0 mm, 8.2 mm, 8.5 mm, 8.9 mm, 9.0 mm, 9.2 mm, 9.5 mm, 9.8 mm, 10.0 mm or a range composed of any two of the above values. The first direction X is parallel to the length direction or the width direction of the negative electrode tab 7. When the first direction X is parallel to the length direction of the negative electrode tab 7, the size of the negative electrode functional layer 73 in the first direction X is the length of the negative electrode functional layer 73, and the size of the negative electrode current collector 71 in the first direction X is the length of the negative electrode current collector 71; when the first direction X is parallel to the width direction of the negative electrode tab 7, the size of the negative electrode functional layer 73 in the first direction X is the width of the negative electrode functional layer 73, and the size of the negative electrode current collector 71 in the first direction X is the width of the negative electrode current collector 71.

[0110] Optionally, the size of the negative electrode functional layer 73 in the second direction is from 0.1 mm to 10 mm; it can be optionally from 1 mm to 4 mm. When the size of the negative electrode functional layer 73 in the second direction is within the above range, it is easy to set the negative electrode functional layer 73 in terms of process, and it can effectively improve the use reliability of the battery cell; moreover, the influence on the energy density of the battery cell is relatively small.

[0111] The negative electrode tab 7 is generally a rectangular parallelepiped sheet structure. The negative electrode edge portion 712 can be considered as the four edge portions of the negative electrode tab 7. When the negative electrode functional layer 73 can cover two of the four edge portions, three edge portions or four edge portions, the size of the negative electrode functional layer 73 in the second direction is the size of the negative electrode functional layer 73 covering one of the edge portions. When the negative electrode functional layer 73 can cover one of the four edge portions, the size of the negative electrode functional layer 73 in the second direction is the size of the edge portion covered by the negative electrode functional layer 73.

[0112] Exemplarily, the size of the negative electrode functional layer 73 in the second direction can be 0.1 mm, 0.2 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4.0 mm, 4.2 mm, 4.5 mm, 4.8 mm, 5.0 mm, 5.2 mm, 5.5 mm, 5.8 mm, 6.0 mm, 6.2 mm, 6.5 mm, 6.8 mm, 7.0 mm, 7.2 mm, 7.5 mm, 7.8 mm, 8.0 mm, 8.2 mm, 8.5 mm, 8.9 mm, 9.0 mm, 9.2 mm, 9.5 mm, 9.8 mm, 10.0 mm or a range composed of any two of the above values. The first direction X, the second direction and the thickness direction Y of the negative electrode tab 7 are perpendicular to each other in pairs; the first direction X is parallel to the length direction or the width direction of the negative electrode tab 7. When the first direction X is parallel to the length direction of the negative electrode tab 7, the second direction is parallel to the width direction of the negative electrode tab 7, and the size of the negative electrode functional layer 73 in the second direction is the width of the negative electrode functional layer 73, and the size of the negative electrode current collector 71 in the second direction is the width of the negative electrode current collector 71; when the first direction X is parallel to the width direction of the negative electrode tab 7, the second direction is parallel to the length direction of the negative electrode tab 7, the size of the negative electrode functional layer 73 in the second direction is the length of the negative electrode functional layer 73, and the size of the negative electrode current collector 71 in the second direction is the length of the negative electrode current collector 71.

[0113] In some embodiments, the thickness H of the negative electrode functional layer 73 satisfies the following formula: H = (x 1 × y 1 + x 2 × y 2 ) / (z × y 2 );

[0114] In the formula,

[0115] x 1 g / cm 2 represents the mass of the positive active material of the positive electrode film layer 82 per unit area on one side of the positive electrode tab 8;

[0116] x 2 g / cm 2 represents the mass of the alkali metal in the alkali metal layer 72 per unit area on one side;

[0117] y 1 mAh / g represents the theoretical gram capacity of the positive active material;

[0118] y 2 mAh / g represents the theoretical gram capacity of the alkali metal;

[0119] z g / cm 3 It represents the deposition density of an alkali metal such as lithium metal, where 0.16 ≤ z ≤ 0.534.

[0120] In the above formula, the positive electrode film layer 82 per unit area on one side refers to the positive electrode film layer 82 on one side of the positive electrode current collector 81, and the alkali metal layer 72 per unit area on one side refers to the alkali metal layer 72 on one side of the negative electrode current collector 71. This formula indicates that alkali metal ions such as lithium ions in the positive electrode sheet 8 can basically all be deposited into the negative electrode sheet 7. At the same time, as the lithium metal on the negative electrode is pulverized during cycling, when the deposition density of lithium metal is less than or equal to 0.16 g / cm 3 , the porosity of the alkali metal layer 72 is relatively high, the wetting ability of the electrolyte for the negative electrode sheet 7 is relatively poor, and the performance of the battery cell has a downward trend; 0.534 g / cm 3 is the density of lithium metal, and the deposition density of lithium metal is usually less than 0.534.

[0121] When the thickness of the negative electrode functional layer 73 satisfies the above formula, the negative electrode functional layer 73 can effectively bond the negative electrode current collector 71 and the separator 9. A reserved space can be provided between the negative electrode current collector 71 and the separator 9 for the volume expansion of the negative electrode sheet 7, reducing the risk of lithium metal pulverization caused by volume expansion, and improving the overall structural stability of the electrode assembly 52. The thickness of the negative electrode functional layer 73 can be greater than the thickness of the alkali metal layer 72 or less than the thickness of the alkali metal layer 72. In the case where the thickness of the negative electrode functional layer 73 is relatively large, it is more conducive to providing a reserved space.

[0122] In the embodiments of the present application, the mass of the positive electrode active material has the meaning well-known in the art and can be measured by methods and equipment known in the art. For example, the elemental content in the positive electrode active material in the positive electrode film layer 82 can be analyzed by inductively coupled plasma technology (ICP), and then the mass of the positive electrode active material can be calculated.

[0123] In the embodiments of the present application, the mass of the alkali metal layer 72 has the meaning well-known in the art and can be measured by methods and equipment known in the art. For example, take the cold-pressed negative electrode sheet 7 (if it is a double-sided cold-pressed negative electrode sheet 7, the alkali metal layer 72 on one side can be wiped off first), measure the area S0 of the alkali metal layer 72, punch it into small circular pieces with an area of S1, weigh it, and record it as M1. Then wipe off the alkali metal layer 72 of the above-mentioned weighed negative electrode sheet 7, weigh the weight of the negative electrode current collector 71, and record it as M0. The mass of the alkali metal layer 72 = (the weight M1 of the negative electrode sheet 7 - the weight M0 of the negative electrode current collector 71) × S0 / S1 of the area of the alkali metal layer 72.

[0124] In the embodiments of the present application, z g / cm 3The deposition density of an alkali metal such as lithium metal can be detected by means of thickness measurement. After the battery cell is cycled, the thickness of the negative electrode sheet 7 is measured as a1, where the thickness of the negative electrode current collector 71 is a2. It is punched into small round pieces with an area of s1, the total weight of the small round pieces is w1, and the weight of the small round piece current collector is w2. The deposition density z = (w1 - w2) / (s1*(a1 - a2)).

[0125] In some embodiments, the thickness of the alkali metal layer 72 is 1 μm to 50 μm; optionally 8 μm to 20 μm.

[0126] Exemplarily, the thickness of the alkali metal layer 72 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or a range composed of any two of the above values.

[0127] In some embodiments, the adhesion of the negative electrode functional layer 73 ≥ 0.15 N / mm; optionally 0.15 to 0.3 N / mm; when the adhesion of the negative electrode functional layer 73 is within the above range, the combination of the negative electrode functional layer 73 and the separator 9 is more stable, which can improve the overall structural stability of the electrode assembly 52.

[0128] Exemplarily, the adhesion of the negative electrode functional layer 73 can be 0.15 N / mm, 0.16 N / mm, 0.20 N / mm, 0.30 N / mm, or a range composed of any two of the above values.

[0129] In the embodiments of the present application, the adhesion of the negative electrode functional layer 73 has the meaning well known in the art, and can be detected by conventional equipment and methods in the art. For example, take a fresh battery cell, discharge it at 1C to 2.8V, then disassemble the battery cell, extract the electrode plate (the positive electrode plate 8 or the negative electrode plate 7). Taking the negative electrode plate 7 as an example for illustration, after the electrolyte on the surface of the negative electrode plate 7 volatilizes, the adhesion of the negative electrode functional layer 73 on the negative electrode plate 7 is measured according to the following steps, and the test can be carried out with reference to the national standard GBT27901995 "Test Method for 180° Peel Strength of Adhesives". As an example, cut the negative electrode plate into test specimens with a size of 5*100 mm2 for standby; bond the negative electrode functional layer 73 on the electrode plate with double-sided tape and compact it with a roller to make the double-sided tape fit with the negative electrode functional layer 73; stick the other side of the double-sided tape on the stainless steel surface, bend one end of the specimen in the reverse direction, and the bending angle is 180°; use a tensile machine for testing, fix one end of the stainless steel on the lower fixture of the tensile machine, fix the bent end of the specimen on the upper fixture, adjust the angle of the specimen to ensure that the upper and lower ends are in a vertical position, and then stretch the specimen at a speed of 50 mm / min until the negative electrode functional layer 73 is completely peeled off from the negative electrode current collector 71, and record the displacement and force during the process. Divide the force at the moment of force balance by the width of the electrode plate that fits with the double-sided tape (the width direction of the electrode plate is perpendicular to the peeling direction) as the bonding force of the electrode plate per unit length.

[0130] In some embodiments, the ionic conductivity of the negative electrode functional layer 73 is less than or equal to 1×10 -5 S·m; when the ionic conductivity of the negative electrode functional layer 73 is within the above range, the ion-conducting performance of the negative electrode functional layer 73 is poor, so that active ions are not easily reduced to generate alkali metals through the negative electrode functional layer 73, reducing the risk of alkali metal dendrites precipitating at the edge of the negative electrode plate 7.

[0131] Exemplarily, the ionic conductivity of the negative electrode functional layer 73 can be 1×10 -5 S·m, 0.9×10 -5 S·m, 0.8×10 -5 S·m, 0.7×10 -5 S·m, 0.6×10 -5 S·m, 0.5×10 -5 S·m, 0.4×10 -5 S·m, 0.3×10 -5 S·m, 0.2×10 -5 S·m, 0.1×10 -5 S·m, 0.05×10 -5 S·m, 1×10 -6 S·m, 1×10 -7 S·m, 1×10 -8 S·m, 1×10-9 S·m or a range composed of any two of the above values.

[0132] In the embodiments of the present application, the ionic conductivity of the negative electrode functional layer 73 has the meaning well known in the art and can be detected by using conventional equipment and methods in the art. The slurry is coated into a film to form the negative electrode functional layer 73, punched into small round pieces with an area of S, and a stainless steel is used as a blocking electrode to form a symmetrical battery, and the impedance of the small round pieces at 25 °C is tested. The ionic conductivity of the negative electrode functional layer 73 is calculated by the formula σ = l / (R·S), where σ is the ionic conductivity, l is the coating thickness, and R is the impedance value of the negative electrode functional layer 73.

[0133] In some embodiments, the polymer may include at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, lithium polyacrylate, sodium polyacrylate, polytetrafluoroethylene, polyimide, polyurethane, block copolymer. The above polymers have relatively high adhesiveness and relatively small ionic conductivity.

[0134] In some embodiments, based on the total mass of the negative electrode functional layer 73, the mass content of the polymer is 8% to 100%, such as 8%, 9%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or a range composed of any two of the above values. When the mass content of the polymer is within the above range, the adhesiveness of the negative electrode functional layer 73 can be improved, and the connection stability between the negative electrode current collector 71 and the separator 9 can be improved.

[0135] In some embodiments, the negative electrode functional layer 73 may further include inorganic particles; further, the inorganic particles can improve the hardness of the negative electrode functional layer 73, further relieve the shear stress caused by the edge of the positive electrode plate 8 on the negative electrode plate 7, and improve the structural stability of the negative electrode plate 7.

[0136] In some embodiments, the inorganic particles may include Al 2 O 3 、γ-AlOOH、SiO 2 、SiC、Si 3 N 4 、AlN、BN、Al 4 C 3 at least one of them.

[0137] In some embodiments, based on the total mass of the negative electrode functional layer 73, the mass content of the inorganic particles is 0 to 92%, such as 1%, 5%, 8%, 9%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or a range composed of any two of the above values.

[0138] In some embodiments, the negative electrode current collector 71 can be a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0139] The negative electrode sheet 7 does not exclude other additional functional layers other than the alkali metal layer 72. For example, in some embodiments, the negative electrode sheet 7 of the embodiments of the present application further includes a conductive bottom coating (for example, composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector 71 and sandwiched between the negative electrode current collector 71 and the alkali metal layer 72. In other embodiments, the negative electrode sheet 7 of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0140] [Positive electrode sheet]

[0141] In order to further improve the use reliability of the battery cell, the embodiments of the present application can further improve the positive electrode sheet 8.

[0142] As Figure 7 shown, in some embodiments, along the thickness direction of the electrode assembly 52, the projection of the positive electrode sheet 8 is located within the projection of the negative electrode sheet 7, which means that the width of the positive electrode sheet 8 is less than or equal to the width of the negative electrode sheet 7, and the length of the positive electrode sheet 8 is less than or equal to the length of the negative electrode sheet 7. When the electrode assembly 52 is a stacked electrode assembly 52, the thickness direction of the electrode assembly 52 is parallel to the thickness direction Y of the negative electrode sheet 7; when the electrode assembly 52 is a wound electrode assembly 52 and the electrode assembly 52 has a flat structure, the flat electrode assembly 52 has a bending area, so the thickness direction Y of the negative electrode sheet 7 may present multiple directions; when the electrode assembly 52 has a cylindrical structure, the thickness direction of the cylindrical electrode assembly 52 can be considered parallel to the radial direction of the cylindrical structure.

[0143] Optionally, the edge of the negative electrode tab 7 along the first direction X extends beyond the edge of the positive electrode tab 8 along the first direction X, that is, the width of the positive electrode tab 8 is smaller than the width of the negative electrode tab 7, or the length of the positive electrode tab 8 is smaller than the length of the negative electrode tab 7. The relatively large area of the negative electrode tab 7 enables the active ions escaping from the positive electrode tab 8 to be embedded in the negative electrode tab 7, reducing the risk of the active ions growing into alkali metal dendrites in the negative electrode tab 7, thereby improving the reliability of use of the battery cell.

[0144] Since the size of the positive electrode tab 8 is shorter than that of the negative electrode tab 7, the edge of the positive electrode tab 8 (for example, one side of the positive electrode tab 8 along the first direction X) may cause shear stress on the negative electrode tab 7, making the negative electrode tab 7 likely to generate cracks or even break. To reduce the risk of the negative electrode tab 7 generating cracks, in some embodiments, along the thickness direction of the electrode assembly 52, the projection profile of the positive electrode tab 8 is located within the projection of the negative electrode functional layer 73, that is, the projection profile of the positive electrode tab 8 can be considered to be formed by the edge projection of the positive electrode tab 8. The edge of the positive electrode tab 8 is disposed opposite to the negative electrode functional layer 73, and since the negative electrode functional layer 73 contains a polymer, it can buffer the shear stress caused by the edge of the positive electrode tab 8 on the negative electrode tab 7, alleviating the stress concentration problem of the negative electrode tab 7, thereby reducing the risk of the negative electrode tab 7 generating cracks and improving the structural stability of the negative electrode tab 7.

[0145] In some embodiments, the positive electrode tab 8 may include a positive electrode current collector 81, a positive electrode functional layer 83, and a positive electrode film layer 82 disposed on at least one side of the positive electrode current collector 81. The positive electrode current collector 81 includes a positive electrode central portion 811 and a positive electrode edge portion 812 disposed around the outside of the positive electrode central portion 811. Along the thickness direction of the electrode assembly 52, the projection of the positive electrode edge portion 812 and the projection of the negative electrode edge portion 712 at least partially overlap. The positive electrode film layer 82 is disposed at least opposite to the positive electrode central portion 811, and the positive electrode film layer 82 includes positive electrode active materials; the positive electrode functional layer 83 is disposed at least opposite to the positive electrode edge portion 812 and connects the positive electrode edge portion 812 and the separator 9, and the positive electrode functional layer 83 includes a polymer. The polymer in the positive electrode functional layer 83 may be made of the same material as the polymer in the negative electrode functional layer 73 or may be made of a different material.

[0146] In some embodiments, the polymer may include at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, lithium polyacrylate, sodium polyacrylate, polytetrafluoroethylene, polyimide, polyurethane, and block copolymer. The above polymers have relatively high adhesiveness and relatively low ionic conductivity.

[0147] In some embodiments, based on the total mass of the positive electrode functional layer 83, the mass content of the polymer is 8% to 100%, such as 8%, 9%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or a range composed of any two of the above values. When the mass content of the polymer is within the above range, the adhesiveness of the positive electrode functional layer 83 can be improved.

[0148] The positive electrode functional layer 83 can play a role in blocking free metallic lithium, further reducing the risk of contact between metallic lithium and the positive electrode tab 8, and improving the reliability of use of the battery cell.

[0149] The positive electrode current collector 81 includes two sides that are opposite to each other along the thickness direction of the positive electrode tab 8. One of the two sides can be provided with the positive electrode film layer 82, and both sides can also be provided with the positive electrode film layer 82.

[0150] The positive electrode current collector 81 can include a positive electrode central portion 811 and a positive electrode edge portion 812. The positive electrode edge portion 812 is disposed around the positive electrode central portion 811. The definitions of the positive electrode central portion 811 and the positive electrode edge portion 812 are to distinguish different regions of the positive electrode current collector 81, and there may be no obvious boundary between the two. For example, the positive electrode current collector 81 is made of aluminum foil, and the aluminum foil is an integral structure. The projection of the positive electrode edge portion 812 and the projection of the negative electrode edge portion 712 at least partially overlap. When the size of the positive electrode current collector 81 is smaller than that of the negative electrode current collector 71, the projection of the positive electrode edge portion 812 can be located within the projection of the negative electrode edge portion 712. Of course, the two can also partially overlap; when the size of the positive electrode current collector 81 is equal to the size of the negative electrode current collector 71, the projection of the positive electrode edge portion 812 can overlap with the projection of the negative electrode edge portion 712. Of course, the two can also partially overlap.

[0151] The positive electrode film layer 82 is at least disposed opposite to the positive electrode central portion 811. It can be understood that along the thickness direction of the positive electrode tab 8, the projection of the positive electrode central portion 811 is located within the projection of the positive electrode film layer 82, that is, the positive electrode film layer 82 at least covers the positive electrode central portion 811. The positive electrode film layer 82 can be only disposed on the positive electrode central portion 811 to cover the positive electrode central portion 811; or on the basis of being disposed on the positive electrode central portion 811 to cover the positive electrode central portion 811, it can also be disposed on at least a part of the positive electrode edge portion 812 to cover at least a part of the positive electrode edge portion 812.

[0152] The positive electrode functional layer 83 is disposed at least opposite to the positive electrode edge portion 812. It can be understood that along the thickness direction of the positive electrode sheet 8, the projection of the positive electrode edge portion 812 is located within the projection of the positive electrode functional layer 83, that is, the positive electrode functional layer 83 covers at least the positive electrode edge portion 812. The positive electrode functional layer 83 can be disposed only at the positive electrode edge portion 812 to cover the positive electrode edge portion 812; or on the basis of being disposed at the positive electrode edge portion 812 to cover the positive electrode edge portion 812, it can also be disposed at a part of the positive electrode tab 84 in the positive electrode sheet 8 and cover the positive electrode tab 84.

[0153] When the size of the positive electrode current collector 81 is smaller than that of the negative electrode current collector 71, since the projection of the positive electrode edge portion 812 and the projection of the negative electrode edge portion 712 at least partially overlap, it means that the edge of the positive electrode sheet 8 is disposed opposite to the negative electrode edge portion 712. In this case, a positive electrode functional layer 83 containing a polymer is disposed on the positive electrode edge portion 812 of the positive electrode sheet 8. The positive electrode functional layer 83 causes less shear stress on the negative electrode sheet 7, thereby being able to slow down the stress concentration problem of the negative electrode sheet 7, reducing the risk of the negative electrode sheet 7 generating cracks, and improving the structural stability of the negative electrode sheet 7. And the positive electrode functional layer 83 can play a barrier role for free metallic lithium, further reducing the risk of metallic lithium contacting the positive electrode sheet 8 and improving the use reliability of the battery cell.

[0154] In the embodiment of the present application, the setting area of the positive electrode film layer 82 can be flexibly set according to production requirements. For example, the positive electrode film layer 82 can partially cover the positive electrode current collector 81. Specifically, it can only cover the positive electrode central portion 811; or it can completely cover the positive electrode current collector 81. The setting mode of the positive electrode functional layer 83 can be adaptively adjusted according to the setting area of the positive electrode film layer 82.

[0155] Please continue to refer to Figure 7 , in some embodiments, the positive electrode film layer 82 is disposed opposite to the positive electrode central portion 811, and the positive electrode functional layer 83 is disposed around the positive electrode film layer 82. When the positive electrode film layer 82 is disposed at the positive electrode central portion 811 and covers the positive electrode central portion 811, the positive electrode functional layer 83 is disposed around the positive electrode film layer 82. The positive electrode functional layer 83 connects the positive electrode edge portion 812 and the separator 9. The positive electrode functional layer 83 can play a further barrier role for free metallic lithium, further reducing the risk of metallic lithium contacting the positive electrode sheet 8 and improving the use reliability of the battery cell.

[0156] Such as Figure 8As shown, in some other embodiments, the positive electrode film layer 82 includes a first positive electrode portion 821 and a second positive electrode portion 822. The first positive electrode portion 821 is disposed opposite to the positive electrode central portion 811. The second positive electrode portion 822 is disposed around the first positive electrode portion 821 and is connected to the first positive electrode portion 821. The second positive electrode portion 822 is located between the positive electrode edge portion 812 and the positive electrode functional layer 83 and connects the positive electrode edge portion 812 and the positive electrode functional layer 83.

[0157] The definitions of the first positive electrode portion 821 and the second positive electrode portion 822 are to distinguish different regions of the positive electrode film layer 82, and there may be no obvious boundary between the two. For example, when the positive electrode active material is coated on the positive electrode current collector 81 to form the positive electrode film layer 82, the positive electrode film layer 82 is an integral structure. The first positive electrode portion 821 is disposed on the positive electrode central portion 811 and covers the positive electrode central portion 811. The second positive electrode portion 822 is disposed around the first positive electrode portion 821 and is connected to the first positive electrode portion 821. The second positive electrode portion 822 is disposed on at least a part of the positive electrode edge portion 812 and covers at least a part of the positive electrode edge portion 812. The positive electrode functional layer 83 covers the second positive electrode portion 822, and one side of the positive electrode functional layer 83 is connected to the positive electrode edge portion 812 through the second positive electrode portion 822. The other side of the positive electrode functional layer 83 is connected to the separator 9. The positive electrode functional layer 83 can block free metallic lithium, further reducing the risk of metallic lithium contacting the positive electrode plate 8 and improving the use reliability of the battery cell.

[0158] As Figure 9 As shown, in some embodiments, the positive electrode plate 8 includes a positive electrode current collector 81 and a positive electrode tab 84. The positive electrode tab 84 is located on one side of the positive electrode current collector 81 along the first direction X, and the positive electrode tab 84 is connected to the positive electrode edge portion 812. The first direction X is perpendicular to the thickness direction of the positive electrode plate 8. In the embodiments of the present application, the first direction X may be the width direction or the length direction of the positive electrode plate 8. At least a part of the positive electrode tab 84 is not coated with the positive electrode active material. The positive electrode current collector 81 and the positive electrode tab 84 may be integrally formed. For example, a one-piece copper foil is sheared to form the positive electrode tab 84 protruding from the positive electrode current collector 81. Of course, the positive electrode current collector 81 and the positive electrode tab 84 may also be separately formed and then connected.

[0159] As Figure 10As shown, in some embodiments, the positive electrode functional layer 83 extends at least to the connection between the positive electrode tab 84 and the positive electrode edge portion 812. Since the connection stability at the connection between the positive electrode tab 84 and the positive electrode edge portion 812 is poor, by providing the positive electrode functional layer 83 at the connection, the connection stability at the connection can be improved, thereby enhancing the overall structural stability of the positive electrode sheet 8 and further enhancing the use reliability of the battery cell. Moreover, the positive electrode functional layer 83 can further block free metallic lithium, reducing the risk of metallic lithium contacting the positive electrode sheet 8 and improving the use reliability of the battery cell.

[0160] Furthermore, the positive electrode functional layer 83 can further extend to the positive electrode tab 84, covering the portion of the positive electrode tab 84 close to the positive electrode edge portion 812, which can further enhance the overall structural stability of the positive electrode sheet 8 and further reduce the risk of metallic lithium escaping.

[0161] Optionally, the size of the positive electrode functional layer 83 in the first direction X is 0.1 mm to 10 mm; it can be selected as 1 mm to 4 mm. When the size of the positive electrode functional layer 83 in the first direction X is within the above range, it is easy to set the positive electrode functional layer 83 in terms of process, and it can effectively improve the use reliability of the battery cell; moreover, the impact on the energy density of the battery cell is relatively small.

[0162] Optionally, the size of the positive electrode functional layer 83 in the second direction is 0.1 mm to 10 mm; it can be selected as 1 mm to 4 mm. When the size of the positive electrode functional layer 83 in the second direction is within the above range, it is easy to set the positive electrode functional layer 83 in terms of process, and it can effectively improve the use reliability of the battery cell; moreover, the impact on the energy density of the battery cell is relatively small.

[0163] In some embodiments, the adhesion force of the positive electrode functional layer 83 ≥ 0.15 N / mm; it can be selected as 0.15 / mm to 0.3 N / mm; when the adhesion force of the positive electrode functional layer 83 is within the above range, the combination of the positive electrode functional layer 83 and the separator 9 is more stable, which can improve the overall structural stability of the electrode assembly 52.

[0164] Exemplarily, the adhesion force of the positive electrode functional layer 83 can be 0.15 N / mm, 0.16 N / mm, 0.20 N / mm, 0.30 N / mm, or a range composed of any two of the above values.

[0165] In the embodiments of the present application, the adhesion force of the positive electrode functional layer 83 has the meaning well-known in the art, and can be detected by conventional equipment and methods in the art. Its specific detection method is similar to the detection of the adhesion force of the negative electrode functional layer 73, and will not be elaborated here.

[0166] In some embodiments, the polymer may include at least one of vinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, lithium polyacrylate, sodium polyacrylate, polytetrafluoroethylene, polyimide, polyurethane, block copolymer.

[0167] In some embodiments, based on the total mass of the positive electrode functional layer 83, the mass content of the polymer is 8% to 100%, such as 8%, 9%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or a range composed of any two of the above values. When the mass content of the polymer is within the above range, the adhesiveness of the positive electrode functional layer 83 can be improved, and the connection stability between the positive electrode current collector 81 and the separator 9 can be improved.

[0168] In some embodiments, the positive electrode functional layer 83 may further include inorganic particles; further, the inorganic particles can increase the hardness of the positive electrode functional layer 83.

[0169] In some embodiments, the inorganic particles may include Al 2 O 3 、γ-AlOOH、SiO 2 、SiC、Si 3 N 4 、AlN、BN、Al 4 C 3 and at least one of them.

[0170] In some embodiments, based on the total mass of the positive electrode functional layer 83, the mass content of the inorganic particles is 0 to 92%, such as 1%, 5%, 8%, 9%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or a range composed of any two of the above values.

[0171] In some embodiments, the positive electrode current collector 81 may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0172] In some embodiments, the positive electrode active material may be a positive electrode active material for battery cells known in the art. By way of example, the positive electrode active material may include at least one of the following materials: layered positive electrode active materials (such as ternary, lithium nickelate / sodium, lithium cobaltate / sodium, lithium manganate / sodium, lithium-rich / sodium layered, and rock salt phase layered materials, etc.), olivine-type phosphate active materials, and spinel-structured positive electrode active materials (such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel lithium manganate, and lithium nickel manganate, etc.).

[0173] Exemplarily, the general formula of the layered positive electrode active material is Li x A y Ni a Co b Mn c M (1-a-b-c) Y z , where 0 ≤ x ≤ 2.1, 0 ≤ y ≤ 2.1, and 0.9 ≤ x + y ≤ 2.1; 0 ≤ a ≤ 1, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, and 0.1 ≤ a + b + c ≤ 1; 1.8 ≤ z ≤ 3.5; A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; Y includes one or more of O and F. Specifically, the layered positive electrode active material may include lithium cobaltate LCO, lithium nickelate LNO, lithium manganate LMO, etc.

[0174] Optionally, the layered positive electrode active material is a ternary material, for example, 0 < a ≤ 1, 0 < b ≤ 1, 0 < c ≤ 1. Exemplarily, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), and LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), or one or more of them.

[0175] Exemplarily, the general formula of the olivine-type phosphate active material is Li x A y Me a M b P 1-c X c Y z, where 0 ≤ x ≤ 1.3, 0 ≤ y ≤ 1.3, and 0.9 ≤ x + y ≤ 1.3; 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5; 0 ≤ c ≤ 0.5; 3 ≤ z ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F. Specifically, the olivine-type phosphate active material includes LiFePO 4 , LiMnPO 4 , LiNiPO 4 , and LiCoPO 4 among others.

[0176] Exemplarily, the general formula of the cathode active material with a spinel structure is Li x A y Mn a M 2-a Y z , where 0 ≤ x ≤ 2, 0 ≤ y ≤ 1, and 0.9 ≤ x + y ≤ 2; 0.5 ≤ a ≤ 2; 3 ≤ z ≤ 5; A includes one or more of Na, K, and Mg; M includes one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; Y includes one or more of O and F. Specifically, the cathode active material with a spinel structure includes LiMn 2 O 4 , LiNi 0.5 Mn 1.5 O 4 , LiCr 0.3 Mn 1.7 O 4 , Li 1.1 Al 0.1 Mn 1.9 O 4 , Li 2 Mn 2 O 4 and Li 1.5 Mn 2 O 4 among others.

[0177] During the charge and discharge process of a battery cell, the insertion and extraction of active ions such as Li will occur, along with consumption. The molar content of Li in the battery cell is different when the battery cell is discharged to different states. In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change.

[0178] In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will show fluctuations.

[0179] In some embodiments, the positive electrode film layer 82 may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0180] In some embodiments, the positive electrode film layer 82 may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0181] [Separator membrane]

[0182] In some embodiments, along the thickness direction of the electrode assembly 52, the projection of the negative electrode plate 7 is located within the projection of the separator membrane 9. The length of the negative electrode plate 7 may be less than or equal to the length of the separator membrane 9, and the width of the negative electrode plate 7 may be less than or equal to the width of the separator membrane 9, so that the separator membrane 9 can play a good role in isolating the positive electrode plate 8 and the negative electrode plate 7.

[0183] Optionally, the edge of the negative electrode plate 7 along the first direction X extends beyond the edge of the separator membrane 9 along the first direction X. That is, the length of the negative electrode plate 7 may be less than the length of the separator membrane 9, or the width of the negative electrode plate 7 may be less than the width of the separator membrane 9, so that the separator membrane 9 can play a good role in isolating the positive electrode plate 8 and the negative electrode plate 7.

[0184] The present application does not particularly limit the type of the separator membrane 9. Any well-known porous structure separator membrane 9 with good chemical stability and mechanical stability can be selected.

[0185] In some embodiments, the material of the separator 9 may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator 9 may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator 9 is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0186] Battery cell

[0187] In a second aspect, the present application provides a battery cell, which includes an electrode assembly. The electrode assembly includes the electrode assembly according to any one of the embodiments of the first aspect of the present application. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. A negative electrode functional layer is provided at an edge portion of the negative electrode plate. Since the negative electrode functional layer contains a polymer, it has adhesiveness and can bond the separator, so that the negative electrode functional layer and the separator are connected as a whole. Even when the phenomenon of alkali metal pulverization occurs during the cyclic charging process of the battery cell, the pulverized alkali metal will be blocked by the negative electrode functional layer and the separator, reducing the risk of alkali metal escape, thereby improving the reliability of use of the battery cell.

[0188] [Electrolyte]

[0189] In some embodiments, the battery cell further includes an electrolyte.

[0190] During the charge and discharge process of the battery cell, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The type of the electrolyte in the embodiments of the present application is not particularly limited and can be selected according to actual needs.

[0191] The electrolyte includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0192] As an example, the electrolyte salt may include, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluoro(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), or at least one of them.

[0193] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate, methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0194] In some embodiments, the electrolyte may optionally further include additives. For example, the additives may include negative electrode film-forming additives, may also include positive electrode film-forming additives, and may further include additives that can improve certain battery performance, such as additives for improving battery overcharge performance, additives for improving battery high-temperature performance, additives for improving battery low-temperature power performance, and the like.

[0195] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be made into an electrode assembly by a winding process and / or a stacking process.

[0196] In some embodiments, the battery cell may include an outer package. The outer package may be used to encapsulate the above electrode assembly and electrolyte.

[0197] In some embodiments, the outer package of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell may also be a soft package, such as a pouch-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0198] This application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other arbitrary shape. As Figure 11 is a battery cell 5 with a square structure as an example.

[0199] In some embodiments, such as Figure 12As shown, the outer package may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator may be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 may be one or more, which can be adjusted according to requirements.

[0200] The preparation method of the battery cell of the present application is well-known. In some embodiments, the positive electrode plate, the separator, the negative electrode plate and the electrolyte may be assembled to form a battery cell. As an example, the positive electrode plate, the separator and the negative electrode plate may be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly is placed in the outer package, dried and then injected with the electrolyte, and after processes such as vacuum packaging, standing, formation, and shaping, the battery cell is obtained.

[0201] In some embodiments of the present application, the battery cells according to the present application may be assembled into a battery module, and the number of battery cells included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0202] Figure 13 is a schematic diagram of a battery module 4 as an example. As Figure 13 shown, in the battery module 4, multiple battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the multiple battery cells 5 may be fixed by fasteners.

[0203] Optionally, the battery module 4 may further include a housing having a receiving space, and multiple battery cells 5 are received in the receiving space.

[0204] In some embodiments, the above battery module may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0205] Figure 14 and Figure 15 are schematic diagrams of a battery pack 1 as an example. As Figure 14 and Figure 15 shown, the battery pack 1 may include a battery box and multiple battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for receiving the battery modules 4. The multiple battery modules 4 may be arranged in the battery box in any manner.

[0206] The battery according to the embodiments of the present application may include one battery cell or multiple battery cells. In the case where the battery includes multiple battery cells, the battery may include a battery module or a battery pack.

[0207] Electrical device

[0208] A third aspect of the embodiments of the present application provides an electrical device, which includes at least one of the battery cell, battery module or battery pack of the present application. The battery cell, battery module or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, 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, a satellite, an energy storage system, etc.

[0209] The electrical device can select a battery cell, battery module or battery pack according to its usage requirements.

[0210] Figure 16 It is a schematic diagram of an electrical device 6 as an example. The electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 6 for high power and high energy density, a battery pack or a battery module can be used.

[0211] Another example of an electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and a battery cell can be used as the power source.

[0212] Embodiment

[0213] The following embodiments more specifically describe the content disclosed in the present application. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the embodiments are commercially available.

[0214] Example 1

[0215] 1. Preparation of the positive electrode sheet

[0216] Aluminum foil is used as the positive electrode current collector.

[0217] The positive electrode active material LiNi 0.8 Co 0.1Mn 0.1 O 2 (NCM811), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone NMP at a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode paste; the positive electrode paste is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode film layer is formed;

[0218] A polymer is coated around the positive electrode film layer to form a positive electrode functional layer, and the positive electrode plate is prepared.

[0219] Among them,

[0220] The length of the positive electrode current collector is 84 mm, and the width is 44 mm;

[0221] The width of the positive electrode functional layer is 2 mm, and the thickness is 25 μm;

[0222] The length of the positive electrode film layer is 80 mm, and the width is 40 mm.

[0223] 2. Preparation of the negative electrode plate

[0224] Copper foil is used as the negative electrode current collector.

[0225] Metallic lithium is uniformly cold pressed onto the surface of the negative electrode current collector copper foil to obtain an alkali metal layer;

[0226] A polymer is coated around the alkali metal layer to form a negative electrode functional layer, and the negative electrode plate is prepared.

[0227] Among them,

[0228] The length of the negative electrode current collector is 90 mm, and the width is 50 mm;

[0229] The width of the negative electrode edge part of the negative electrode current collector is 4 mm;

[0230] The width of the negative electrode functional layer is 4 mm, and the thickness is 25 μm;

[0231] The length of the alkali metal layer is 82 mm, and the width is 42 mm.

[0232] 3. Separator

[0233] A porous polyethylene (PE) membrane is used as the separator, and the length of the separator is 110 mm, and the width is 52 mm.

[0234] 4. Preparation of the electrolyte

[0235] In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents 1,3-dioxolane (DOL) and dimethoxyethane (DME) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, a lithium salt is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0236] 5. Preparation of battery cell

[0237] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an insulating role. The edge of the positive electrode sheet is arranged opposite to the negative electrode functional layer, and then they are laminated to obtain an electrode assembly; the electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte, and after processes such as vacuum packaging, standing, forming, and shaping, a lithium metal battery is obtained.

[0238] Comparative Example 1

[0239] 1. Preparation of positive electrode sheet

[0240] Aluminum foil is used as the positive electrode current collector.

[0241] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a weight ratio of 97.5:1.4:1.1 in an appropriate amount of solvent N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry; the positive electrode slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode film layer is formed;

[0242] Among them,

[0243] The length of the positive electrode current collector is 84 mm, and the width is 44 mm;

[0244] The length of the positive electrode film layer is 84 mm, and the width is 44 mm.

[0245] 2. Preparation of negative electrode sheet

[0246] Copper foil is used as the negative electrode current collector.

[0247] Metallic lithium is uniformly cold-pressed onto the surface of the negative electrode current collector copper foil to obtain an alkali metal layer, and the negative electrode sheet is prepared.

[0248] Among them,

[0249] The length of the negative electrode current collector is 90 mm, and the width is 50 mm;

[0250] The length of the alkali metal layer is 90 mm, and the width is 50 mm.

[0251] 3. Separator

[0252] A porous polyethylene (PE) membrane is used as the separator. The length of the separator is 110 mm and the width is 52 mm.

[0253] 4. Preparation of electrolyte

[0254] In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, a lithium salt is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0255] 5. Preparation of battery cell

[0256] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role. The edge of the positive electrode sheet is arranged opposite to the negative electrode functional layer, and then the electrode assembly is obtained by stacking; the electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After processes such as vacuum packaging, standing, formation, and shaping, a lithium metal battery is obtained.

[0257] Example 2

[0258] 1. Preparation of positive electrode sheet

[0259] Aluminum foil is used as the positive electrode current collector.

[0260] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a weight ratio of 97.5:1.4:1.1 in an appropriate amount of solvent N-methylpyrrolidone NMP to form a uniform positive electrode paste; the positive electrode paste is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode film layer is formed;

[0261] A polymer is coated on the periphery of the positive electrode film layer to form a positive electrode functional layer, and the positive electrode sheet is prepared.

[0262] Among them,

[0263] The length of the positive electrode current collector is 84 mm and the width is 44 mm;

[0264] The width of the positive electrode functional layer is 2 mm and the thickness is 25 μm;

[0265] The length of the positive electrode film layer is 80 mm and the width is 40 mm.

[0266] 2. Preparation of the negative electrode sheet

[0267] Copper foil is used as the negative electrode current collector.

[0268] Metallic lithium is evenly cold-pressed onto the surface of the negative electrode current collector copper foil to obtain an alkali metal layer;

[0269] A polymer is coated on the alkali metal layer to form a negative electrode functional layer, and the negative electrode sheet is prepared.

[0270] Among them,

[0271] The length of the negative electrode current collector is 90 mm, and the width is 50 mm;

[0272] The width of the negative electrode edge part of the negative electrode current collector is 4 mm;

[0273] The width of the negative electrode functional layer is 4 mm, and the thickness is 15 μm. The negative electrode functional layer is located on the side of the alkali metal layer away from the negative electrode current collector;

[0274] The length of the alkali metal layer is 90 mm, and the width is 50 mm.

[0275] 3. Separator

[0276] A porous polyethylene (PE) membrane is used as the separator. The length of the separator is 110 mm, and the width is 52 mm.

[0277] 4. Preparation of the electrolyte

[0278] In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, the lithium salt and the mixed solvent are mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0279] 5. Preparation of the battery cell

[0280] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play a separation role. The edge of the positive electrode sheet is arranged opposite to the negative electrode functional layer, and then the electrode assembly is obtained by stacking. The electrode assembly is placed in an outer packaging shell, dried, and then injected with the electrolyte. After vacuum packaging, standing, forming, shaping and other processes, a lithium metal battery is obtained.

[0281] Example 3

[0282] 1. Preparation of the positive electrode sheet

[0283] Aluminum foil is used as the positive electrode current collector.

[0284] The positive electrode active material LiNi 0.8 Co0.1 Mn 0.1 O 2 (NCM811), carbon black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder are fully stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) according to a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry; the positive electrode slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode film layer is formed;

[0285] A polymer is coated around the positive electrode film layer to form a positive electrode functional layer, and the positive electrode plate is prepared.

[0286] Among them,

[0287] The length of the positive electrode current collector is 84 mm, and the width is 44 mm;

[0288] The width of the positive electrode functional layer is 2 mm, and the thickness is 25 μm;

[0289] The length of the positive electrode film layer is 80 mm, and the width is 40 mm.

[0290] 2. Preparation of the negative electrode plate

[0291] Copper foil is used as the negative electrode current collector.

[0292] Metallic lithium is uniformly cold pressed onto the surface of the negative electrode current collector copper foil to obtain an alkali metal layer;

[0293] A polymer is coated around the alkali metal layer to form a negative electrode functional layer, and the negative electrode plate is prepared.

[0294] Among them,

[0295] The length of the negative electrode current collector is 90 mm, and the width is 50 mm;

[0296] The width of the negative edge part of the negative electrode current collector is 4 mm;

[0297] The width of the negative electrode functional layer is 4 mm, and the thickness is 25 μm, and the negative electrode functional layer extends to the connection between the negative electrode current collector and the negative electrode tab (copper foil);

[0298] The length of the alkali metal layer is 82 mm, and the width is 42 mm.

[0299] 3. Separator

[0300] A porous polyethylene (PE) membrane is used as the separator, and the length of the separator is 110 mm, and the width is 52 mm.

[0301] 4. Preparation of the electrolyte

[0302] In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents 1,3-dioxolane (DOL) and dimethoxyethane (DME) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, a lithium salt and the mixed solvent are mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0303] 5. Preparation of battery cell

[0304] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role. The edge of the positive electrode sheet is arranged opposite to the negative electrode functional layer, and then the stacked components are obtained; the electrode assembly is placed in an outer packaging shell, dried, injected with electrolyte, and after processes such as vacuum packaging, standing, forming, and shaping, a lithium metal battery is obtained.

[0305] Example 4

[0306] 1. Preparation of positive electrode sheet

[0307] Aluminum foil is used as the positive electrode current collector.

[0308] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone NMP in a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode paste; the positive electrode paste is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode film layer is formed;

[0309] A polymer is coated on the periphery of the positive electrode film layer to form a positive electrode functional layer, and the positive electrode sheet is prepared.

[0310] Among them,

[0311] The length of the positive electrode current collector is 80 mm, and the width is 40 mm;

[0312] The width of the positive electrode functional layer is 4 mm, and the thickness is 25 μm;

[0313] The length of the positive electrode film layer is 72 mm, and the width is 32 mm.

[0314] 2. Preparation of negative electrode sheet

[0315] Copper foil is used as the negative electrode current collector.

[0316] Metallic lithium is uniformly cold-pressed onto the surface of the negative electrode current collector copper foil to obtain an alkali metal layer;

[0317] A polymer is coated on the periphery of the alkali metal layer to form a negative electrode functional layer, and a negative electrode sheet is prepared.

[0318] Among them,

[0319] The length of the negative electrode current collector is 90 mm, and the width is 50 mm.

[0320] The width of the negative electrode edge part of the negative electrode current collector is 4 mm.

[0321] The width of the negative electrode functional layer is 4 mm, and the thickness is 25 μm.

[0322] The length of the alkali metal layer is 82 mm, and the width is 42 mm.

[0323] 3. Separator

[0324] A porous polyethylene (PE) membrane is used as the separator. The length of the separator is 110 mm, and the width is 52 mm.

[0325] 4. Preparation of electrolyte

[0326] In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, a lithium salt and the mixed solvent are mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0327] 5. Preparation of battery cell

[0328] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role. The edge of the positive electrode sheet is arranged opposite to the negative electrode functional layer, and then the electrode assembly is obtained by stacking. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, shaping and other processes, a lithium metal battery is obtained.

[0329] Example 5

[0330] 1. Preparation of positive electrode sheet

[0331] Aluminum foil is used as the positive electrode current collector.

[0332] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2(NCM811), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode paste; the positive electrode paste is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode film layer is formed;

[0333] A polymer is coated around the positive electrode film layer to form a positive electrode functional layer, and the positive electrode plate is prepared.

[0334] Among them,

[0335] The length of the positive electrode current collector is 80 mm, and the width is 40 mm;

[0336] The length of the positive electrode film layer is 80 mm, and the width is 40 mm.

[0337] 2. Preparation of the negative electrode plate

[0338] Copper foil is used as the negative electrode current collector.

[0339] Metallic lithium is uniformly cold-pressed onto the surface of the negative electrode current collector copper foil to obtain an alkali metal layer;

[0340] A polymer is coated around the alkali metal layer to form a negative electrode functional layer, and the negative electrode plate is prepared.

[0341] Among them,

[0342] The length of the negative electrode current collector is 90 mm, and the width is 50 mm;

[0343] The width of the negative electrode edge part of the negative electrode current collector is 4 mm;

[0344] The width of the negative electrode functional layer is 4 mm, and the thickness is 25 μm;

[0345] The length of the alkali metal layer is 82 mm, and the width is 42 mm.

[0346] 3. Separator

[0347] A porous polyethylene (PE) membrane is used as the separator, and the length of the separator is 110 mm, and the width is 52 mm.

[0348] 4. Preparation of the electrolyte

[0349] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) are mixed at a volume ratio of 1:1 to obtain an electrolyte solvent, and then a lithium salt and the mixed solvent are mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0350] 5. Preparation of the battery cell

[0351] Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role. The edge of the positive electrode sheet is arranged opposite to the negative electrode functional layer, and then stack them to obtain an electrode assembly; place the electrode assembly in an outer packaging shell, inject electrolyte after drying, and go through processes such as vacuum packaging, standing, forming, and shaping to obtain a lithium metal battery.

[0352] Example 6

[0353] Prepare a lithium-ion battery using a method similar to that of Example 1. The difference from Example 1 is that the thickness of the negative electrode functional layer is adjusted, and the thickness of the negative electrode functional layer in Example 6 is 40 μm.

[0354] Examples 7 and 8

[0355] Prepare a lithium-ion battery using a method similar to that of Example 1. The difference from Example 1 is that the material of the negative electrode functional layer is adjusted.

[0356] The relevant parameters of the examples and comparative examples are shown in Table 1.

[0357] Test section

[0358] 1. Test on the cycle capacity retention rate of the lithium-ion battery:

[0359] Perform a cycle test on the lithium-ion battery with the above structure under a clamping force of 0.2 MPa to 1 MPa. The specific steps are as follows: Charge the active ion battery at a constant current of 0.5 C until the voltage reaches 4.3 V, then charge at a constant voltage of 4.3 V until the current reaches 0.05 C, and let it stand for 10 min; discharge at a constant current of 0.5 C until the voltage reaches 2.8 V, and let it stand for 10 min.

[0360] After repeating the above steps 100 times, disassemble the battery; after separating the electrode sheets, observe the distribution of pulverized lithium and whether there are cracks on the negative electrode sheet.

[0361] Judgment criteria:

[0362] Qualified: No pulverized lithium escapes from the area of the negative electrode sheet, and there are no cracks on the negative electrode sheet;

[0363] Unqualified: Pulverized lithium appears outside the area of the negative electrode sheet, and cracks are generated on the negative electrode sheet.

[0364] After 100 cycles, disassemble the battery cell. The pulverized lithium is blocked within the area of the negative electrode sheet, and the edge of the positive active material falls within the edge coating area of the negative electrode sheet. There are no indentations and cracks on the negative electrode sheet.

[0365] Test results

[0366] The test results are shown in Table 1.

[0367] Table 1

[0368]

[0369] In Table 1, the block copolymer is a styrene-butadiene-styrene block copolymer.

[0370] In the single-layer positive electrode film layer of the positive electrode tab, the areal capacity of the positive electrode active material per unit area on one side of the positive electrode film layer is 3.2 mAh / cm 2 ;

[0371] The theoretical specific capacity of the positive electrode active material is 205 mAh / g.

[0372] In the negative electrode tab,

[0373] In the negative electrode tab, the mass of lithium metal in the alkali metal layer per unit area on one side is 0.52 mg / cm 2 ;

[0374] The theoretical specific capacity of lithium metal is 3860 mAh / g.

[0375] As can be seen from Table 1, compared with Comparative Example 1, the functional layer in the embodiment of the present application helps to separate the negative electrode material area, reduces the risk of battery failure caused by lithium powder exceeding the negative electrode area and contacting the positive electrode, and by adjusting the thickness of the functional layer, the bonding performance between the separator and the negative electrode tab can be made better, which is beneficial to further improving the reliability of battery use. In addition, the addition of the block copolymer can further improve the bonding firmness.

[0376] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as a limitation of the present application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of the present application.

Claims

1. An electrode assembly, characterized in that, it includes a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The negative electrode plate includes: a negative current collector, including a negative central portion and a negative edge portion disposed around the outside of the negative central portion; an alkali metal layer disposed on at least one side of the negative current collector, and the alkali metal layer is at least disposed opposite to the negative central portion; and a negative functional layer, at least disposed opposite to at least a part of the negative edge portion, and the negative functional layer connects the negative edge portion and the separator. The negative functional layer includes a polymer.

2. The electrode assembly according to claim 1, characterized in that, the alkali metal layer is disposed opposite to the negative central portion, and the negative functional layer is disposed around the outside of the alkali metal layer.

3. The electrode assembly according to claim 1 or 2, characterized in that, the alkali metal layer includes: a first metal portion disposed opposite to the negative central portion; and a second metal portion disposed around the outside of the first metal portion. The second metal portion is located between the negative edge portion and the negative functional layer and connects the negative edge portion and the negative functional layer.

4. The electrode assembly according to any one of claims 1 to 3, characterized in that, the negative electrode plate further includes a negative electrode tab, and the negative electrode tab is located on one side of the negative current collector along a first direction and is connected to the negative edge portion. The first direction is perpendicular to the thickness direction of the negative electrode plate; the negative functional layer at least extends to the connection portion between the negative electrode tab and the negative edge portion.

5. The electrode assembly according to claim 4, characterized in that, the negative functional layer includes: a first sub-layer disposed at least on one side of the negative edge portion along the thickness direction of the negative electrode plate; and a second sub-layer disposed at least on the other side of the negative edge portion along the thickness direction of the negative electrode plate. The end of the second sub-layer facing away from the negative electrode tab is connected to the end of the first sub-layer facing away from the negative electrode tab.

6. The electrode assembly according to any one of claims 1 to 5, characterized in that, along the thickness direction of the electrode assembly, the projected contour of the positive electrode plate is located within the projection of the negative functional layer.

7. The electrode assembly according to any one of claims 1 to 6, characterized in that, the positive electrode plate includes: a positive current collector, including a positive central portion and a positive edge portion disposed around the outside of the positive central portion. Along the thickness direction of the electrode assembly, the projection of the positive edge portion at least partially overlaps with the projection of the negative edge portion; a positive electrode film layer disposed on at least one side of the positive current collector, and the positive electrode film layer is at least disposed opposite to the positive central portion. The positive electrode film layer includes a positive electrode active material; and a positive functional layer, at least disposed opposite to at least a part of the positive edge portion, and connects the positive edge portion and the separator. The positive functional layer includes a polymer.

8. The electrode assembly according to claim 7, characterized in that, The positive electrode film layer is disposed opposite to the positive electrode central portion, and the positive electrode functional layer is disposed around the outside of the positive electrode film layer.

9. The electrode assembly according to claim 7, wherein, the positive electrode film layer includes: a first positive electrode portion disposed opposite to the positive electrode central portion; and a second positive electrode portion disposed around the outside of the first positive electrode portion, the second positive electrode portion being located between the positive electrode edge portion and the positive electrode functional layer and connecting the positive electrode edge portion and the positive electrode functional layer.

10. The electrode assembly according to any one of claims 7 to 9, wherein, the positive electrode tab further includes a positive electrode tab, the positive electrode tab being located on one side of the positive electrode current collector along a first direction and connected to the positive electrode edge portion, the first direction being perpendicular to the thickness direction of the negative electrode tab; the positive electrode functional layer extends at least to the connection portion of the positive electrode tab and the positive electrode edge portion.

11. The electrode assembly according to any one of claims 1 to 10, wherein, along the thickness direction of the electrode assembly, the projection of the negative electrode tab is located within the projection of the separator.

12. The electrode assembly according to any one of claims 1 to 11, wherein, the size of the negative electrode functional layer along the first direction is 0.1 mm to 10 mm, the first direction being perpendicular to the thickness direction of the negative electrode tab; and / or the size of the negative electrode functional layer along the second direction is 0.1 mm to 10 mm, the second direction being perpendicular to the thickness direction of the negative electrode tab.

13. The electrode assembly according to any one of claims 1 to 12, wherein, The thickness H of the negative electrode functional layer satisfies the following formula: H = (x 1 ×y 1 +x 2 ×y 2 ) / (z×y 2 ); wherein, x 1 g / cm 2 represents the mass of the positive active material of the positive electrode film layer per unit area on one side of the positive electrode sheet; x 2 g / cm 2 represents the mass of the alkali metal in the alkali metal layer per unit area on one side; y 1 mAh / g represents the theoretical gram capacity of the positive electrode active material; y 2 mAh / g represents the theoretical gram capacity of the alkali metal; z g / cm 3 represents the deposition density of the alkali metal, where 0.16 ≤ z ≤ 0.

534.

14. The electrode assembly according to any one of claims 1 to 13, wherein, the adhesion force of the negative electrode functional layer ≥ 0.15 N / mm.

15. The electrode assembly according to any one of claims 1 to 14, wherein, the polymer includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, lithium polyacrylate, sodium polyacrylate, polytetrafluoroethylene, polyimide, polyurethane, block copolymer, and the block copolymer includes at least one of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer.

16. The electrode assembly according to any one of claims 1 to 15, wherein, The negative electrode functional layer further includes inorganic particles, and the inorganic particles include at least one of Al 2 O 3 , γ-AlOOH, SiO 2 , SiC, Si 3 N 4 , AlN, BN, Al 4 C 3 .

17. The electrode assembly according to any one of claims 1 to 16, wherein, the alkali metal layer includes at least one of lithium metal and sodium metal.

18. A battery, wherein, comprising the electrode assembly according to any one of claims 1 to 17.

19. An electrical device, wherein, comprising the battery according to claim 18.

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