Positive composite current collector, battery cell, battery device, and electrical device

Abstract

The present disclosure provides a positive composite current collector, a battery cell, a battery device, and an electrical device. The battery cell includes an electrode assembly, and the electrode assembly includes a wound negative electrode sheet, a separator, and a positive electrode sheet. The positive electrode sheet includes a positive composite current collector, and the positive composite current collector includes a support layer and a conductive layer located on at least one surface of the support layer; the conductive layers facing the winding axis direction are arranged at intervals along the length direction of the positive composite current collector, and the gap between two adjacent conductive layers penetrates along the width direction of the positive composite current collector; the positive composite current collector includes a flat region and a bent region, at least a part of the conductive layer is located in the flat region, and the gap between two adjacent conductive layers is located in the bent region. The battery cell of the present disclosure can reduce the occurrence of lithium or sodium deposition in the bent region of the wound battery cell, thereby improving the reliability of the battery cell.

Description

Technical Field

[0001] The present disclosure relates to the field of batteries, and particularly to a positive composite current collector, a battery cell, a battery device, and an electrical device. Background Art

[0002] The wound electrode assembly is widely used in lithium-ion or sodium-ion battery cells due to its mature process and low cost. However, the problem of lithium or sodium deposition exists in the bending area of the wound electrode assembly, reducing the reliability of the battery cell. Summary of the Invention

[0003] The present disclosure provides a positive composite current collector, a battery cell, a battery device, and an electrical device, which can reduce the occurrence of lithium or sodium deposition in the bending area of the wound battery cell, thereby improving the reliability of the battery cell.

[0004] In a first aspect, the present disclosure provides a battery cell, including an electrode assembly. The electrode assembly includes a wound negative electrode sheet, a separator, and a positive electrode sheet. The positive electrode sheet includes a positive composite current collector, and the positive composite current collector includes a support layer and a conductive layer located on at least one surface of the support layer. The conductive layers facing the winding axis direction are arranged at intervals along the length direction of the positive composite current collector, and the gap between two adjacent conductive layers penetrates along the width direction of the positive composite current collector. The positive composite current collector includes a straight area and a bending area, at least part of the conductive layer is located in the straight area, and the gap between two adjacent conductive layers is located in the bending area.

[0005] In the embodiment of the present disclosure, a gap without a conductive layer is provided in the bending area of the positive composite current collector, and the support layer does not have the ability to conduct electrons, thereby reducing the probability of the active ions in the positive active material on the surface of the support layer in the bending area from gaining or losing electrons, and thus reducing the occurrence probability of lithium or sodium deposition in the bending area of the wound battery cell and improving the reliability of the battery cell.

[0006] In some embodiments, the conductive layers are located on both surfaces of the support layer. The conductive layers facing the winding axis direction are arranged at intervals along the length direction of the positive composite current collector, and the conductive layers facing away from the winding axis direction are arranged at intervals along the length direction of the positive composite current collector.

[0007] In the embodiments of the present disclosure, by arranging the conductive layers on both sides of the support layer at intervals, the positive active material at the gap between two adjacent conductive layers in the bending area does not undergo an electrochemical reaction of gaining or losing electrons. Therefore, its expansion during the use of the battery cell is small, which can reduce the stress of the positive electrode plate in the bending area and improve the structural stability of the electrode assembly at the bending part. Similarly, since the probability of active ions in the positive active material on the surface of the support layer in the bending area gaining or losing electrons is further reduced, the probability of lithium or sodium precipitation in the bending area of the wound battery cell is further reduced, thereby further improving the cycle performance and reliability of the battery cell.

[0008] In some embodiments, the conductive layers are located in the straight area. This can make all the gaps between two adjacent conductive layers located in the bending area, further reducing the probability of active ions gaining or losing electrons in the bending area, thereby reducing the probability of lithium or sodium precipitation in the bending area of the wound battery cell and improving the cycle performance and reliability of the battery cell.

[0009] In some embodiments, the porosity of the support layer is 10% - 30%.

[0010] In some embodiments, the average pore diameter of the support layer is 100 nm - 10 μm.

[0011] In some embodiments, the thickness of the support layer is 1 μm - 5 μm.

[0012] When one or more of the porosity, average pore diameter, or thickness of the support layer are within the above ranges, it is beneficial for the electrolyte to infiltrate the bending area, further reducing the occurrence of lithium or sodium precipitation in the bending area, and can also endow the support layer with high mechanical properties, thereby further improving the cycle performance and reliability of the battery cell.

[0013] In some embodiments, the material of the support layer includes one or more of polyethylene terephthalate, polyethylene, polypropylene, epoxy resin, polystyrene, and their respective derivatives.

[0014] In some embodiments, the thickness of the conductive layer is 3 μm - 10 μm. This can balance the conductivity of the positive composite current collector and the energy density of the battery cell.

[0015] In some embodiments, the gap width Dn between two adjacent conductive layers is 5 mm - 10 mm, where n is an integer greater than or equal to 1.

[0016] In some embodiments, along the winding direction of the electrode assembly from the inner layer to the outer layer, Dn satisfies: D1 = D2 < D3 = D4 < …… < D n-1 = D n 。

[0017] In some embodiments, along the winding direction of the electrode assembly from the inner layer to the outer layer, D n satisfies: D1 = D2 = D3 = D4 = …… = D n-1 = D n .

[0018] In some embodiments, D is calculated based on the radius of the innermost bending region, the thickness of the negative electrode sheet, the thickness of the positive electrode sheet, the thickness of the separator, and the gap between the positive electrode sheet and the negative electrode sheet n .

[0019] In some embodiments, the thickness of the positive electrode sheet is 100 μm - 200 μm.

[0020] In some embodiments, the thickness of the negative electrode sheet is 100 μm - 200 μm.

[0021] In some embodiments, the thickness of the separator is 5 μm - 20 μm.

[0022] In some embodiments, the gap between the positive electrode sheet and the negative electrode sheet is 10 μm - 100 μm.

[0023] By adjusting one or more of the thickness of the positive electrode sheet, the thickness of the negative electrode sheet, the thickness of the separator, or the gap between the positive electrode sheet and the negative electrode sheet within the above ranges, the battery cell of the present disclosure can have good mechanical properties and high energy density at the same time.

[0024] In some embodiments, the conductive layer includes a metal, and the metal includes one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0025] In some embodiments, the positive electrode sheet further includes a positive electrode film layer provided on at least one surface of the positive electrode composite current collector; the compaction density of the positive electrode film layer is 1 - 5 g / cm 3 . This can improve the energy density of the battery cell, and can fully compact the positive electrode active material, reducing the phenomenon of powder shedding during cycling.

[0026] In a second aspect, the present disclosure provides a positive electrode composite current collector, which includes a support layer and a conductive layer located on at least one surface of the support layer; the conductive layer facing the winding axis direction is spaced along the length direction of the positive electrode composite current collector, and the gap between two adjacent conductive layers runs through along the width direction of the positive electrode composite current collector; the positive electrode composite current collector includes a straight region and a bending region, at least a part of the conductive layer corresponds to the straight region, and the gap between two adjacent conductive layers is located in the bending region.

[0027] In a third aspect, the present disclosure provides a battery device, which includes a plurality of battery cells of the first aspect of the present disclosure.

[0028] In a fourth aspect, the present disclosure provides an electrical device including the battery cell of the first aspect of the present disclosure or the battery device of the third aspect of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required to be used in the embodiments of the present disclosure. Obviously, the following described drawings are only some embodiments of the present disclosure, and those of ordinary skill in the art can obtain other drawings according to these drawings without creative efforts.

[0030] Figure 1 Schematic diagram of a battery cell provided for some embodiments of the present disclosure.

[0031] Figure 2 Schematic diagram of an electrical device provided for some embodiments of the present disclosure.

[0032] Figure 3 Schematic diagram of the structure of a positive composite current collector after winding provided for some embodiments of the present disclosure.

[0033] Figure 4 Front view of a positive composite current collector before winding provided for some embodiments of the present disclosure.

[0034] Figure 5 Top view of a positive composite current collector before winding provided for some embodiments of the present disclosure.

[0035] Figure 6 Another schematic diagram of the structure of a positive composite current collector before winding provided for some embodiments of the present disclosure.

[0036] Figure 7 Another schematic diagram of the structure of a positive composite current collector before winding provided for some embodiments of the present disclosure.

[0037] Figure 8 Another schematic diagram of the structure of a positive composite current collector after winding provided for some embodiments of the present disclosure.

[0038] Figure 9 Another schematic diagram of the structure of a positive composite current collector after winding provided for some embodiments of the present disclosure.

[0039] Among them, 10 is a positive composite current collector; 11 is a support layer; 12 is a conductive layer; 20 is a first surface; 30 is a second surface.

[0040] In the drawings, the drawings are not necessarily drawn to actual scale. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Hereinafter, embodiments of the positive electrode composite current collector, battery cell, battery device, and electrical device of the present disclosure will be specifically described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure and are not intended to limit the subject matter recited in the claims.

[0042] The "ranges" disclosed in the present disclosure are defined in the form of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The 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 the present disclosure, unless otherwise stated, 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" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when it is stated 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.

[0043] Unless otherwise specified, all embodiments and alternative embodiments of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of the present disclosure.

[0044] Unless otherwise specified, all technical features and alternative technical features of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of the present disclosure.

[0045] Unless otherwise specified, all steps of the present disclosure can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which 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.

[0046] In the present disclosure, the terms "a plurality of" and "multiple kinds of" refer to two or more than two.

[0047] In the description of the embodiments of the present disclosure, unless otherwise specified, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0048] Unless otherwise specified, the test temperature of each parameter mentioned in the present disclosure is 25 °C.

[0049] The battery cell mentioned in the embodiments of the present disclosure can independently achieve the functions of charging and discharging. The battery cell can be in the shape of a cuboid or other shapes. For example, Figure 1 is a battery cell 5 with a cuboid structure as an example.

[0050] The battery apparatus mentioned in the embodiments of the present disclosure may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include a plurality of battery cells, and the plurality of battery cells are connected in series, parallel or in a hybrid connection through a busbar component.

[0051] In some embodiments, the battery cell assembly is usually formed by arranging a plurality of battery cells.

[0052] As an example, the battery cell assembly can be a battery module, and the battery module is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0053] In some embodiments, the battery device may be a battery pack, which includes a box body and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body.

[0054] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box body by fixing the battery module in the box body.

[0055] As an example, the battery cell assembly may also be accommodated in the box body by directly fixing a plurality of battery cells to the box body.

[0056] As an example, the box body may include a first box body and a second box body. The first box body and the second box body are snapped together so that a closed space is formed inside the box body to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first box body may be a top cover or a bottom plate.

[0057] As an example, the box body may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0058] In some embodiments, the box body may be part of the chassis structure of a vehicle. For example, a part of the box body may become at least a part of the floor of the vehicle, or a part of the box body may become at least a part of the cross beam and longitudinal beam of the vehicle.

[0059] The technical solutions described in the embodiments of the present disclosure are applicable to various electrical devices using battery cells and battery devices, such as but not limited to mobile devices (such as mobile phones, tablet computers, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc. The battery cells and battery devices are used to store or provide electrical energy.

[0060] Figure 2 It is a schematic diagram of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0061] During the cycling process of the battery cell, the positive electrode active material and the negative electrode active material will expand, resulting in the extrusion of the electrolyte in the bending area of the wound electrode core, causing lithium or sodium deposition in the bending area due to poor electrolyte infiltration. In addition, due to winding, the area of the side of the positive electrode facing the winding axis (also called the concave surface of the positive electrode) in the bending area is larger than the area of the side of the negative electrode facing away from the core (also called the convex surface of the negative electrode). This may cause the lithium or sodium deintercalation ability of the concave surface of the positive electrode to be greater than the lithium or sodium intercalation ability of the convex surface of the negative electrode, resulting in lithium or sodium deposition on the convex surface of the negative electrode, and further affecting the reliability of the battery cell.

[0062] In the related art, by making the unit area capacity of the positive electrode active material in the bending area of the positive electrode tab smaller than that of the positive electrode active material in the flat area of the positive electrode tab, and making the areal density in the bending area smaller than that in the flat area during coating, the purpose of avoiding the lithium deintercalation ability of the positive electrode in the bending area being greater than the lithium intercalation ability of the negative electrode can be achieved, and finally the lithium deposition problem in the bending area can be reduced. However, there is still a problem that lithium deposition occurs in the bending area due to poor electrolyte infiltration caused by the expansion of the positive and negative electrodes during the cycling process.

[0063] In view of this, the present disclosure provides a positive electrode composite current collector, a battery cell, a battery device, and an electrical device using the same, which can reduce the occurrence of lithium or sodium deposition in the bending area of the wound battery cell, thereby improving the reliability of the battery cell.

[0064] A battery cell includes an electrode assembly. The electrode assembly includes a wound negative electrode tab, a separator, and a positive electrode tab. The positive electrode tab includes a positive electrode composite current collector 10. As Figures 3 - 5 shown, the positive electrode composite current collector 10 includes a support layer 11 and a conductive layer 12 located on at least one surface of the support layer 11;

[0065] The conductive layers 12 facing the winding axis direction are arranged at intervals along the length direction of the positive electrode composite current collector 10, and the gaps between adjacent two conductive layers 12 are arranged to penetrate along the width direction of the positive electrode composite current collector 10;

[0066] The positive electrode composite current collector 10 includes a flat area S1 and a bending area S2. At least a part of the conductive layer 12 is located in the flat area S1, and the gaps between adjacent two conductive layers 12 are located in the bending area S2.

[0067] As Figure 5 shown, the x direction is the length direction of the positive electrode composite current collector, and the y direction is the width direction of the positive electrode composite current collector. The gaps between adjacent two conductive layers extend in the width direction of the positive electrode composite current collector to separate the conductive layers. The bending area is formed due to the winding of the electrode assembly, and the extending direction of the bending area is parallel to the extending direction of the winding axis.

[0068] It is understandable that whether it is poor electrolyte infiltration or lithium or sodium precipitation caused by the positive electrode's lithium removal ability being greater than the negative electrode's lithium insertion ability, the cause can be attributed to the imbalance of the electrochemical reaction of lithium ions or sodium ions undergoing redox in the bending zone.

[0069] The embodiment of the present disclosure provides a gap without a conductive layer in the bending area of the positive electrode composite current collector, and the support layer does not have the ability to conduct electrons, thereby reducing the probability of active ions in the positive electrode active material on the surface of the support layer in the bending area gaining or losing electrons, thereby reducing the probability of lithium or sodium deposition in the bending area of the wound battery cell and improving the reliability of the battery cell.

[0070] The electrode assembly in the disclosed embodiments is wound so that the positive composite current collector has a concave and convex portion in its folded region, with the concave portion facing the winding axis of the electrode assembly. Similarly, the positive electrode tab has a first convex surface and a first concave surface in its folded region, while the negative electrode tab has a second convex surface and a second concave surface in its folded region.

[0071] Generally, compared with the straight area, the outer electrode sheet in the bent area has a larger surface area than the inner electrode sheet. The negative electrode sheet, the separator, and the positive electrode sheet are stacked in the order of separator, negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet... from the first layer to the last layer, and a battery cell is formed by winding. At this time, the positive electrode sheet is located on the outer layer of the wound electrode assembly relative to the negative electrode sheet, that is, when the outer layer is the positive electrode sheet and the inner layer is the negative electrode sheet, under the same unit area capacity, for the lithium ions or sodium ions released from the positive electrode sheet, the negative electrode sheet cannot fully embed these lithium ions or sodium ions due to insufficient lithium or sodium embedding space, resulting in the occurrence of lithium or sodium precipitation. Moreover, in the bending area, the active material layer on the side of the positive electrode sheet or the negative electrode sheet facing the winding axis is squeezed and aggregated, and the stress inside the electrode sheet increases, which is not conducive to the deintercalation and deintercalation of active ions during the charging and discharging process. The active material layer on the side of the positive electrode sheet or the negative electrode sheet away from the winding center will become loose, so that the closer the positive electrode sheet or the negative electrode sheet is to the winding center, the greater the stress difference on the electrode sheet, and the more serious the lithium or sodium precipitation.

[0072] Therefore, by arranging the conductive layers facing the winding axis at intervals along the length direction of the positive electrode composite current collector, the probability of lithium or sodium deposition in the bending area of the wound battery cell can be reduced, thereby improving the reliability of the battery cell.

[0073] In some embodiments, as Figure 4 As shown, the positive electrode composite current collector has a first surface 20 and a second surface 30 opposite to each other along the thickness direction. After winding, the first surface 20 faces the winding axis, and the second surface 30 faces away from the winding axis.

[0074] In some embodiments, as Figure 6 andFigure 7 As shown, the conductive layer 12 is located on both side surfaces of the support layer 11; the conductive layers 12 facing the winding axis direction are arranged at intervals along the length direction of the positive composite current collector 10, and the conductive layers 12 facing away from the winding axis direction are arranged at intervals along the length direction of the positive composite current collector 10.

[0075] In the embodiment of the present disclosure, by arranging the conductive layers on both sides of the support layer at intervals, the positive active material at the gap between two adjacent conductive layers in the bending area does not undergo an electrochemical reaction of gaining or losing electrons. Therefore, its expansion during the use of the battery cell is small, which can reduce the stress of the positive electrode plate in the bending area and improve the structural stability of the electrode assembly at the bending position. Similarly, since the probability of active ions in the positive active material on the surface of the support layer in the bending area gaining or losing electrons is further reduced, the probability of lithium or sodium deposition in the bending area of the wound battery cell is further reduced, and the cycle performance and reliability of the battery cell are further improved.

[0076] As Figure 8 shown, in some embodiments, the conductive layer 12 is located in the straight area S1, and the conductive layer 12 is located in the bending area S2.

[0077] As Figure 9 shown, in some embodiments, the conductive layer 12 is located in the straight area S1.

[0078] In the embodiment of the present disclosure, by making the conductive layer located in the straight area, the gaps between two adjacent conductive layers can all be located in the bending area, further reducing the probability of active ions gaining or losing electrons in the bending area, thereby reducing the probability of lithium or sodium deposition in the bending area of the wound battery cell and improving the cycle performance and reliability of the battery cell.

[0079] In some embodiments, the porosity of the support layer can be 10% - 30%, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, or a range composed of any two of the above values.

[0080] In some embodiments, the average pore diameter of the support layer can be 100 nm - 10 μm. For example, it can be 100 nm, 500 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range composed of any two of the above values.

[0081] When the porosity or average pore diameter of the support layer is within the above range, it is beneficial to the infiltration of the electrolyte into the bending area, further reducing the occurrence of lithium or sodium deposition in the bending area, and can also endow the support layer with higher mechanical properties, thereby further improving the cycle performance and reliability of the battery cell.

[0082] In some embodiments, the material of the support layer may include one or more of polyethylene terephthalate, polyethylene (PE), polypropylene (PP), epoxy resin, polystyrene (PS), and their respective derivatives.

[0083] The thickness of the support layer and the thickness of the conductive layer can be set according to the thickness of the positive electrode sheet.

[0084] In some embodiments, the thickness of the support layer may be 1 μm - 5 μm, for example, it may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range composed of any two of the above values. This can further improve the wettability of the electrolyte in the bending area, reduce the occurrence of lithium or sodium deposition in the bending area, and also endow the support layer with high mechanical properties, thereby further improving the cycling performance and reliability of the battery cell.

[0085] In some embodiments, the thickness of the conductive layer may be 3 μm - 10 μm, for example, it may be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range composed of any two of the above values.

[0086] The use of the positive composite current collector in the embodiments of the present disclosure can improve the mass energy density of the battery cell. When the thickness of the conductive layer is within the above range, the conductivity of the positive composite current collector and the energy density of the battery cell can be balanced.

[0087] The thicknesses of the support layer and the conductive layer both refer to their average thicknesses, which can be measured using a micrometer.

[0088] In some embodiments, the gap width D between two adjacent conductive layers n is 5 mm - 10 mm, and n is an integer greater than or equal to 1.

[0089] After winding the positive composite current collector, n increases from 1 to n in sequence from the innermost end to the outermost end of the positive composite current collector.

[0090] In some embodiments, along the x - direction, the width of the conductive layer is L n , and n is an integer greater than or equal to 1.

[0091] In some embodiments, along the winding direction of the electrode assembly from the inner layer to the outer layer, D n satisfies: D1 = D2 = D3 = D4 =... = D n-1 = D n . In the case where D n satisfies: D1 = D2 = D3 = D4 =... = D n-1 = D n , L nSatisfy: L1 < L2 < L3 < L4 < …… < L n-1 < L n .

[0092] In some embodiments, along the winding direction of the electrode assembly from the inner layer to the outer layer, D n Satisfy: D1 = D2 < D3 = D4 < …… < D n-1 = D n . In D n Satisfy: D1 = D2 < D3 = D4 < …… < D n-1 = D n case, L i Satisfy: L1 ≈ L2 ≈ L3 ≈ …… ≈ L n .

[0093] It should be noted that the winding direction of the electrode assembly may refer to the extension direction from the innermost end of the positive electrode tab to the outermost end of the positive electrode tab, rather than specifically referring to the winding direction during the formation of the electrode assembly.

[0094] It can be understood that the bending degree and amplitude of the tab wound on the inner layer are greater than those of the tab wound on the outer layer. Therefore, in the wound electrode assembly, the part closer to the winding axis of the electrode assembly is more likely to deposit lithium or sodium. Similarly, when the electrode assembly expands, the layer closer to the winding axis of the wound electrode assembly is more severely squeezed.

[0095] As the winding radius gradually increases, along the winding direction from the inner layer to the outer layer, the length of the bending area gradually increases. Therefore, it is necessary to make the width of the gap between adjacent two conductive layers change as much as possible with the change of the length of the bending area, so that along the winding direction, multiple gaps cover the corresponding bending area in a larger range. That is, make the width of the gap between adjacent conductive layers of each layer match the length of the corresponding bending area as much as possible. Thus, the problem of lithium or sodium deposition in the bending area can be further improved, and the cycle performance and reliability of the battery cell can be further enhanced.

[0096] In some embodiments, D n Is half of the arc circumference corresponding to the bending area of the corresponding layer of the positive composite current collector.

[0097] In some embodiments, according to the radius of the innermost bending area, the thickness of the negative electrode tab, the thickness of the positive electrode tab, the thickness of the separator, and the gap between the positive electrode tab and the negative electrode tab, D n is calculated.

[0098] The gap between the positive electrode plate and the negative electrode plate refers to the distance between the positive electrode plate and the negative electrode plate along the thickness direction of the electrode assembly. The above distance includes the thickness of the separator between the positive electrode plate and the negative electrode plate, and the distance between the positive electrode plate and the negative electrode plate is the distance measured before injecting electrolyte after the bare battery cell is put into the shell.

[0099] In some embodiments, D n is calculated according to the formula (1) as follows:

[0100] D 2i-1 = π×[r + i×x + i×y + 2i×z + w×(i + 1)] (1)

[0101] r is the radius of the innermost bending area, x is the thickness of the negative electrode plate, y is the thickness of the positive electrode plate, z is the thickness of the separator, w is the gap between the positive electrode plate and the negative electrode plate. i is the number of layers of the positive electrode plate in the bending area, and n can be 1, 2, 3... 2i - 1, 2i. The D calculated by the above formula n can make the length of the bending area of the positive electrode plate basically correspond to the gap between the conductive layers, thereby further reducing the problem of lithium or sodium precipitation in the bending area.

[0102] In some embodiments, along the winding direction of the electrode assembly from the inner layer to the outer layer, Dn satisfies: D1 = D2 < D3 = D4 <... < D n-1 = D n , and D max is 5 mm - 10 mm.

[0103] In some embodiments, along the winding direction of the electrode assembly from the inner layer to the outer layer, D n satisfies: D1 = D2 = D3 = D4 =... = D n-1 = D n , and D max is 5 mm - 10 mm.

[0104] D n satisfies that D max is 5 mm - 10 mm, that is, in the case where D calculated by the formula (1) n > D max , then D n takes the value of D max . Thus, it is possible to reduce the occurrence of lithium or sodium precipitation in the bending area of the wound battery cell and improve the reliability of the battery cell, while taking into account the mass energy density of the battery cell.

[0105] In some embodiments, the thickness of the positive electrode plate can be 100 - 200 μm.

[0106] In some embodiments, the thickness of the negative electrode sheet can be 100 - 200 μm.

[0107] In some embodiments, the thickness of the separator can be 5 - 20 μm.

[0108] In some embodiments, the gap between the positive electrode sheet and the negative electrode sheet can be 10 μm - 100 μm.

[0109] By adjusting one or more of the thickness of the positive electrode sheet, the thickness of the negative electrode sheet, the thickness of the separator, or the gap between the positive electrode sheet and the negative electrode sheet within the above ranges, the battery cell can have good mechanical properties while also having a high energy density in the embodiments of the present disclosure.

[0110] In some embodiments, the conductive layer includes a metal, and the metal includes one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0111] In some embodiments, the N / P of the battery cell can be 1 - 1.2. N / P refers to the ratio of the negative electrode capacity to the positive electrode capacity.

[0112] In some embodiments, the positive electrode sheet may further include a positive electrode film layer provided on at least one surface of the positive electrode composite current collector.

[0113] In some embodiments, the tap density of the positive electrode film layer can be 1 - 5 g / cm 3 。

[0114] When the tap density of the positive electrode film layer is within the above range, the energy density of the battery cell can be improved, and the positive electrode active material can be fully compacted, reducing the phenomenon of powder shedding during cycling.

[0115] In some embodiments, the positive electrode film layer is provided on the surface of the conductive layer, and the positive electrode film layer is provided on the surface of the support layer.

[0116] Taking a lithium-ion battery cell as an example: the positive electrode active material can include one or more of lithium transition metal oxides and their modified materials, lithium-containing phosphates and their modified materials, lithium titanate, sulfur, selenium, and tellurium.

[0117] Optionally, examples of the lithium transition metal oxide may include but are not limited to one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium-rich manganese-based materials.

[0118] Optionally, examples of the lithium-containing phosphate may include but are not limited to one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0119] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material may include one or more of lithium transition metal oxides represented by the general formula Li a Ni b Co c M d O e A f and their modified materials. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A may include one or more of N, F, S, and Cl.

[0120] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.83 Mn 0.08 Co 0.07 O2 (abbreviated as Ni83), LiNi 0.90 Mn 0.05 Co 0.05 O2 (abbreviated as Ni90), LiNi 0.94 Mn 0.03 Co 0.03 O2 (abbreviated as Ni94), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, and one or more of their respective modified materials.

[0121] Taking a single sodium-ion battery as an example: The positive electrode active material may include, but is not limited to, one or more of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue-based materials.

[0122] As an example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue-based materials, materials with the general formula X p M’ q (PO4) r O x Y 3-x or more. In the general formula X p M’ q (PO4) r O x Y 3-x , 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, X includes, but is not limited to, H + , Li + , Na + , K + and NH4 + or more, M’ is a transition metal cation, optionally including, but not limited to, one or more of V, Ti, Mn, Fe, Co, Ni, Cu, and Zn, and Y is a halogen anion, optionally one or more of F, Cl, and Br.

[0123] During the charge and discharge process of the single battery, the insertion and extraction and consumption of Li or Na will occur, and the molar content of Li or Na is different when the single battery is discharged to different states. In the listing of the positive electrode active material in the present disclosure, the molar content of Li or Na is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the single battery, after charge and discharge cycles, the molar content of Li or Na will change. In the listing of the positive electrode active material in the present disclosure, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of O to change, and the actual molar content of O will also fluctuate.

[0124] The modification materials of the above-mentioned cathode active materials can be doping modification and / or surface coating modification of the cathode active materials.

[0125] In some embodiments, the cathode film layer may further include a cathode binder, and the cathode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0126] In some embodiments, the cathode film layer may further include a cathode conductive agent, and the cathode conductive agent may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0127] [Cathode composite current collector]

[0128] A cathode composite current collector includes a support layer and a conductive layer located on at least one surface of the support layer;

[0129] The conductive layers facing the winding axis direction are arranged at intervals along the length direction of the cathode composite current collector, and the gap between two adjacent conductive layers penetrates along the width direction of the cathode composite current collector;

[0130] The cathode composite current collector includes a straight region and a bent region, at least part of the conductive layer corresponds to the straight region, and the gap between two adjacent conductive layers is located in the bent region.

[0131] [Preparation method of cathode composite current collector]

[0132] In some embodiments, the preparation method of the cathode composite current collector includes: arranging conductive layers at intervals on at least one surface of the support layer.

[0133] In some embodiments, the setting method of the conductive layer may include, but is not limited to, vapor deposition, electroless plating, electroplating, bonding, and mechanical rolling.

[0134] Exemplarily, the conductive layer can be formed by vapor deposition, thereby improving the bonding force between the conductive layer and the support layer.

[0135] In some embodiments, the preparation method of the support layer may include a melt-extrusion-biaxial stretching method.

[0136] A mask can be covered on the surface of the support layer before forming the conductive layer, so as to obtain a conductive layer with gaps in one step; or a metal conductive layer with gaps can be prepared by chemical etching, laser etching, etc. after forming the conductive layer.

[0137] [Negative electrode plate]

[0138] The structure and composition of the negative electrode plate can be selected according to the type of battery cell, and the embodiments of the present disclosure do not limit this.

[0139] In some embodiments, the negative electrode plate may include a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0140] The negative electrode active material can be a negative electrode active material for battery cells known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microbeads, silicon-based materials, and tin-based materials, etc. The silicon-based materials may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include at least one of elemental tin, tin oxides, and tin alloys. However, the present disclosure is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of battery cells can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0141] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0142] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0143] In some embodiments, the negative electrode film layer may further include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0144] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0145] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0146] In some embodiments, the negative electrode plate may include a negative electrode current collector and a metal layer disposed on at least one surface of the negative electrode current collector. The metal material in the metal layer may include one or more of lithium element and lithium alloy.

[0147] A lithium alloy may be an alloy of metallic lithium and other metallic elements or non-metallic elements. For example, the other metallic elements in the lithium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the non-metallic elements in the lithium alloy may include one or more of boron, carbon, and silicon.

[0148] In some embodiments, the negative electrode sheet may be a lithium sheet (foil) or a lithium alloy sheet (foil).

[0149] In some embodiments, the negative electrode plate may include a negative electrode current collector but not a metal layer, thereby forming a negative electrode-free lithium metal battery cell. During the charge and discharge cycle of the negative electrode-free lithium metal battery cell, the lithium in the positive electrode will be precipitated and stripped off in the form of lithium metal on the negative electrode side.

[0150] In some embodiments, the negative electrode current collector may include a metal foil, a conductive polymer material, a carbon material, or a composite current collector. Examples of metal foil include pure metals, alloys, and surface-treated metals, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include but are not limited to copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, aluminum, aluminum alloys, silver, and silver alloys. Examples of polymer materials include but are not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The composite current collector may be formed by forming a metal material on a polymer substrate.

[0151] In some embodiments, the negative electrode plate may be made of foamed metal. The foamed metal may be nickel foam, copper foam, aluminum foam, alloy foam, or carbon foam. When the foamed metal is used as the negative electrode plate, the surface of the foamed metal may or may not be provided with a negative electrode active material.

[0152] As an example, the negative electrode active material can be filled or / and deposited in the negative electrode current collector.

[0153] [Separator]

[0154] In some embodiments, the separator is disposed between the positive electrode and the negative electrode. The separator of the embodiments of the present disclosure can be a porous structure separator with good chemical stability and mechanical stability.

[0155] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0156] Optionally, an inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator.

[0157] [Electrolyte]

[0158] The battery cell includes an electrolyte, and the electrolyte functions to conduct ions between the positive and negative electrodes. The embodiments of the present disclosure do not specifically limit the type of the electrolyte, and it can be selected according to requirements. For example, the electrolyte can include one or more of a solid electrolyte, a gel electrolyte, and a liquid electrolyte (i.e., an electrolytic solution).

[0159] In some embodiments, the electrolyte uses an electrolytic solution, and the electrolytic solution includes an electrolyte salt and a solvent.

[0160] The type of the electrolyte salt is not specifically limited and can be selected according to actual requirements.

[0161] Taking a lithium-ion battery cell as an example, the electrolyte salt can include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro bis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro bis(oxalato)phosphate (LiTFOP).

[0162] Taking a single sodium-ion battery as an example, the electrolyte salt may include, but is not limited to, one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluoro(oxalato)borate (NaDFOB), sodium bis(oxalato)borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluoro(oxalato)phosphate (NaDFOP), and sodium tetrafluoro(oxalato)phosphate (NaTFOP).

[0163] The type of the solvent is not specifically limited and can be selected according to actual needs.

[0164] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate (PPC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE). The solvent may also be an ether solvent. The ether solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether.

[0165] In some embodiments, the electrolyte may also optionally 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 performances, such as additives for improving the overcharge / quick charge performance of the single battery, additives for improving the high-temperature performance of the single battery, additives for improving the low-temperature performance of the single battery, etc.

[0166] Among them, the gel electrolyte includes a polymer as a framework network and can be used in combination with an ionic liquid-lithium salt.

[0167] Among them, the solid electrolyte includes a polymer solid electrolyte, an inorganic solid electrolyte, and a composite solid electrolyte.

[0168] As an example, the polymer of the polymer solid electrolyte may include polyethers (polyethylene oxide), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, single-ion polymers, polyionic liquids, cellulose, etc.

[0169] As an example, the inorganic solid electrolyte may be one or more of oxide solid electrolytes (crystalline perovskite, lithium superionic conductor, garnet, amorphous LiPON film), sulfide solid electrolytes (crystalline lithium superionic conductor, amorphous sulfide), and halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0170] As an example, the composite solid electrolyte is formed by adding inorganic solid electrolyte fillers to the polymer solid electrolyte.

[0171] In some embodiments, the battery cell may further include an outer package. The outer package may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package may also be a soft package, such as a pouch soft package. The material of the soft package may be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0172] The preparation method of the battery cell is well-known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte may be assembled to form the battery cell. As an example, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process. Exemplarily, the positive electrode sheet, the separator, and the negative electrode sheet are wound on a winding mandrel to form a cylindrical structure. After the winding mandrel is removed, the cylindrical structure is flattened to form a wound core. The electrode assembly is placed in the outer package, dried, and then the above-mentioned electrolyte is injected. After processes such as vacuum packaging, standing, and formation, the battery cell is obtained.

[0173] Embodiment

[0174] The following embodiments more specifically describe the content of the present disclosure. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the present disclosure 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 the instruments used in the embodiments are all commercially available.

[0175] Embodiment 1

[0176] Preparation of the positive composite current collector:

[0177] The surface of the 5μm thick support layer polypropylene (PP) is cleaned and placed in a vacuum plating chamber. The high-purity aluminum wire in the metal evaporation chamber is melted and evaporated at a high temperature of 1300℃-2000℃. The evaporated aluminum passes through the cooling system in the vacuum plating chamber, and finally forms a 5μm thick aluminum metal conductive layer on both sides of the support layer. Laser etching is used to etch the corresponding gap on the aluminum metal conductive layer according to the requirement of i=40 layers of positive electrode sheets in the bending area of the battery cell to obtain a positive electrode composite current collector. The width of the gap is determined by D 2i-1 = π×[r+i×x+i×y+2i×z+w×(i+1)], and D n Satisfy the formula, D1=D2<D3=D4<……<D 79 =D 80 , D max =10mm, the thickness of the positive electrode sheet is 110μm, the thickness of the negative electrode sheet is 135μm, the thickness of the isolation film is 15μm, the gap between the positive electrode sheet and the negative electrode sheet is 25μm, and the clamping needle radius is 3mm.

[0178] Preparation of positive electrode sheet:

[0179] The positive electrode active material 0.4 (Li2MnO3) · 0.6 (LiNi 0.5 Mn 0.5 O2), acetylene black as a positive electrode conductive agent, and polyvinylidene fluoride (PVDF) as a positive electrode binder were mixed in a mass ratio of 94:4:2, and N-methylpyrrolidone as a solvent was added and stirred thoroughly to obtain a positive electrode slurry. The positive electrode slurry was coated on both sides of the positive electrode composite current collector, and then the positive electrode sheet was obtained through drying, cold pressing, die cutting and other processes. The compaction density of the positive electrode film layer was 1.65g / cm 3 .

[0180] Preparation of negative electrode sheet:

[0181] The negative electrode active material graphite, the negative electrode conductive agent acetylene black, the negative electrode binder styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 94:2:3:1, and deionized water was added as a solvent. The mixture was thoroughly stirred and mixed to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of a conventional negative electrode current collector copper foil, and then dried, cold pressed, and die-cut to obtain a negative electrode sheet. The compacted density of the negative electrode film layer was 1.65g / cm 3 .

[0182] Preparation of electrolyte:

[0183] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), polycarbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. Then, LiPF6, VC, DTD, and PS were added and stirred evenly to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L, and the mass percentages of VC, DTD, and PS were 3%, 1%, and 1% respectively.

[0184] Preparation of a lithium-ion battery monomer:

[0185] The die-cut separator, positive electrode sheet, and negative electrode sheet were stacked in the order of separator, negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet... from the first layer to the last layer, and a battery core was formed by winding. The battery core was placed in an outer package and the above-mentioned electrolyte was injected, and then a lithium-ion battery monomer was obtained through processes such as formation and aging.

[0186] Example 2

[0187] The preparation method of the lithium-ion battery monomer was the same as that of Example 1 except for the following differences.

[0188] During the preparation of the positive composite current collector, aluminum metal conductive layers with a thickness of 5 μm were formed on both sides of the support layer, but corresponding gaps were laser-etched only on one side of the aluminum metal conductive layer. The width of the gaps was the same as the values of D1, D3, D5... D in Example 1, and a positive composite current collector was obtained. And the conductive layers in the lithium-ion battery monomer facing the winding axis direction were arranged at intervals along the length direction of the positive composite current collector. n And the conductive layers in the lithium-ion battery monomer facing the winding axis direction were arranged at intervals along the length direction of the positive composite current collector.

[0189] Example 3

[0190] During the preparation of the positive composite current collector, D n satisfied the formula D1 = D2 = D3 = D4 =... = D 79 = D 80 = D 40 and D 40 According to the formula D 40 = π × [r + i × x + i × y + 2i × z + w × (i + 1)] calculated, the preparation method of the lithium-ion battery monomer was the same as that of Example 1.

[0191] Comparative Example 1

[0192] The preparation method of the lithium-ion battery monomer was the same as that of Example 1 except that the positive current collector was an aluminum metal current collector.

[0193] Comparative Example 2

[0194] The preparation method of the lithium-ion battery monomer is the same as that of Example 1, except that the conductive layers on both sides of the positive composite current collector are not spaced apart.

[0195] Comparative Example 3

[0196] The preparation method of the lithium-ion battery monomer is the same as that of Example 1, except for the following differences.

[0197] The positive active material is coated on both side surfaces of the positive current collector aluminum foil at intervals to obtain a positive electrode sheet.

[0198] Test part

[0199] (1)Cycle capacity retention rate

[0200] At 25 °C, it is charged at a constant current of 1C to 4.4V, then charged at a constant voltage of 4.4V until the current drops to 0.05C, and then discharged at a constant current of 1C to 2.5V to obtain the first-cycle discharge specific capacity (Cd1); it is charged and discharged repeatedly according to the above steps for 500 cycles, and the discharge specific capacity after 500 cycles is recorded as Cdn.

[0201] The 500-cycle capacity retention rate (%) = the discharge specific capacity after 500 cycles (Cdn) / the first-cycle discharge specific capacity (Cd1) × 100%.

[0202] (2)Mass energy density

[0203] At 25 °C, the lithium-ion battery monomer is charged at a constant current of 0.33C to 4.4V and continues to be charged at a constant voltage until the current is 0.05C; after the lithium-ion battery monomer is left standing for 5 minutes, it is discharged at a constant current of 0.33C to 2.5V to obtain the discharge energy Q.

[0204] The mass energy density of the lithium-ion battery monomer (Wh / kg) = the discharge energy Q / the mass m of the lithium-ion battery monomer.

[0205] (3)Judgment of the lithium deposition level in the bent area of the negative electrode sheet

[0206] After cycling the battery monomer 500 times according to the above cycling method, disassemble the battery monomer and further disassemble the positive electrode sheet and the negative electrode sheet, observe the lithium deposition situation in the bent area of the negative electrode sheet, and the judgment criteria are shown in Table 1.

[0207] Table 1

[0208]

[0209] The test results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 2.

[0210] Table 2

[0211]

[0212] As can be seen from the test results in Table 2, the embodiments of the present disclosure can reduce the occurrence of lithium plating in the bending area of the wound battery cell, improving the reliability of the battery cell.

[0213] It should be noted that the present disclosure is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same constitution and the same effect as the technical idea within the scope of the technical solution of the present disclosure are included in the technical scope of the present disclosure. In addition, within the scope not departing from the gist of the present disclosure, various modifications that can be conceived by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present disclosure.

Claims

1. A battery cell includes an electrode assembly, and the electrode assembly includes a wound negative electrode tab, a separator, and a positive electrode tab. The positive electrode tab includes a positive composite current collector, and is characterized in that, the positive composite current collector includes a support layer and a conductive layer located on at least one surface of the support layer; the conductive layers facing the winding axis direction are arranged at intervals along the length direction of the positive composite current collector, and the gaps between adjacent two of the conductive layers are arranged to penetrate along the width direction of the positive composite current collector; the positive composite current collector includes a flat area and a bent area, at least part of the conductive layer is located in the flat area, and the gaps between adjacent two of the conductive layers are located in the bent area; the positive electrode tab further includes a positive electrode film layer arranged on at least one surface of the positive composite current collector, the positive electrode film layer is arranged on the surface of the conductive layer, and the positive electrode film layer is arranged on the surface of the support layer.

2. The battery cell according to claim 1, wherein, The conductive layer is located on both surfaces of the support layer; the conductive layers facing the winding axis direction are arranged at intervals along the length direction of the positive composite current collector, and the conductive layers facing away from the winding axis direction are arranged at intervals along the length direction of the positive composite current collector.

3. The battery cell according to claim 1, wherein The conductive layer is located in the flat area.

4. The battery cell according to claim 1, characterized in that, The porosity of the support layer is 10% - 30%; and / or, the average pore diameter of the support layer is 100 nm - 10 μm; and / or, the thickness of the support layer is 1 μm - 5 μm.

5. The battery cell according to claim 1, characterized in that, The material of the support layer includes one or more of polyethylene terephthalate, polyethylene, polypropylene, epoxy resin, polystyrene and their respective derivatives.

6. The battery cell according to claim 1, wherein The thickness of the conductive layer is 3 μm - 10 μm.

7. The battery cell according to claim 1, characterized in that, The gap width D between two adjacent conductive layers n is 5 mm - 10 mm, and n is an integer greater than or equal to 1.

8. The battery cell according to claim 7, characterized in that, From the inner layer to the outer layer along the winding direction of the electrode assembly, the D n Satisfies: D1 = D2 < D3 = D4 < …… < D n-1 = D n ; and / or, Along the winding direction of the electrode assembly from the inner layer to the outer layer, the D n satisfies: D1 = D2 = D3 = D4 =……=D n-1 = D n .

9. The battery cell according to claim 7, wherein Calculate the D based on the radius of the innermost bending area, the thickness of the negative electrode sheet, the thickness of the positive electrode sheet, the thickness of the separator, and the gap between the positive electrode sheet and the negative electrode sheet n .

10. The battery cell according to claim 1, characterized in that, the battery cell satisfies one or more of the following conditions (1)-(4): (1) The thickness of the positive electrode tab is 100 μm - 200 μm; (2) The thickness of the negative electrode tab is 100 μm - 200 μm; (3) The thickness of the separator is 5 μm - 20 μm; (4) The gap between the positive electrode tab and the negative electrode tab is 10 μm - 100 μm.

11. The battery cell according to claim 1, wherein The conductive layer includes a metal, and the metal includes one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

12. The battery cell according to claim 1, characterized in that, The compaction density of the positive electrode film layer is 1-5 g / cm 3 .

13. A battery device, characterized in that, including a plurality of battery cells according to any one of claims 1 - 12.

14. An electrical device, characterized in that, including the battery cell according to any one of claims 1 - 12 or the battery device according to claim 13.

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