Battery and electric equipment

Abstract

The invention relates to the technical field of batteries, and discloses a battery and electric equipment, and the battery comprises a laminated core body which comprises a plurality of negative plates, a plurality of positive plates and a plurality of diaphragms which are laminated along a first direction; the negative plates and the positive plates are alternately arranged along the first direction; the projection area of the negative plate is larger than that of the positive plate in the first direction; the diaphragm is arranged between the adjacent negative plate and positive plate, and two opposite surfaces of the diaphragm along the first direction are respectively bonded with the negative plate and the positive plate; the shell is coated outside the laminated core body; the shell and the stacked core body are bonded along at least one side of the first direction; the binding power between the diaphragm and the negative plate is F1N / m, the binding power between the diaphragm and the positive plate is F2N / m, and the binding power between the shell and the laminated core body is F3N / m; wherein F3 > F1 > F2. According to the battery and the electric equipment, the problem of layering in the stacked core body in the falling process of the battery can be effectively relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery and electrical equipment. Background Art

[0002] Laminated batteries are widely used in consumer electronics batteries due to their high energy density and flexible packaging. Laminated batteries consist of a positive electrode, a negative electrode, a separator, an electrolyte, and an aluminum-plastic film. However, during a drum drop test, the protective plate on the top of the battery repeatedly impacts the negative electrode due to the impact of the drop, which can easily cause delamination of the stacked core and dramatically increase the risk of internal short circuits within the battery. Summary of the Invention

[0003] In view of this, the present invention provides a battery and an electrical device to solve the problem that the stacked core of a laminated battery is prone to delamination when it falls.

[0004] In a first aspect, the present invention provides a battery, comprising: a stacked body, comprising a plurality of negative electrode sheets, a plurality of positive electrode sheets, and a plurality of separators stacked along a first direction; the negative electrode sheets and the positive electrode sheets are alternately arranged along the first direction; the projected area of ​​the negative electrode sheets is larger than the projected area of ​​the positive electrode sheets along the first direction; the separator is arranged between adjacent negative electrode sheets and positive electrode sheets, and the two opposite surfaces of the separator along the first direction are respectively bonded to the negative electrode sheets and the positive electrode sheets; a shell, covering the outside of the stacked body; the shell is bonded to at least one side of the stacked body along the first direction; the bonding force between the separator and the negative electrode sheet is F1 N / m, the bonding force between the separator and the positive electrode sheet is F2 N / m, and the bonding force between the shell and the stacked body is F3 N / m; wherein F3>F1>F2.

[0005] In an optional embodiment, 1.2≤F3 / F1≤4.0; preferably, 2.0≤F3 / F1≤3.0.

[0006] In an optional embodiment, 0.3≤F2 / F1≤0.8; preferably, 0.5≤F2 / F1≤0.7.

[0007] In an optional embodiment, the diaphragm includes a base film, a heat-resistant layer and two adhesive layers; along the first direction, the heat-resistant layer is arranged on one side of the base film; and along the first direction, one of the two adhesive layers is arranged on the side of the base film away from the heat-resistant layer, and the other is arranged on the side of the heat-resistant layer away from the base film; preferably, the adhesive layer includes polymer particles; preferably, the polymer particles include a first polymer, and the first polymer includes a polymer formed by copolymerization of at least one monomer of methyl methacrylate, ethyl methacrylate, isooctyl acrylate, n-propyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate, styrene, butadiene, methacrylamide, acrylamide, acrylonitrile, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, and hexafluoropropylene; preferably, the average particle size of the primary particles of the polymer particles is 0.2μm-1μm.

[0008] In an optional embodiment, the battery includes a bonding member; the shell and the stacked core body are bonded to at least one side along the first direction by the bonding member; the stacked core body includes a first pole piece bonded to the bonding member, and the projected area of ​​the first pole piece along the first direction is S1 mm 2 , the projected area of ​​the bonding part along the first direction is S2 mm 2 ; 30%≤S2 / S1≤80%; preferably, 40%≤S2 / S1≤70%; preferably, adhesive members are provided on both sides of the stacked core along the first direction.

[0009] In an optional embodiment, the battery includes adhesive tape, which is arranged on the edge of the stacked core; the stacked core has a first surface and a second surface arranged opposite to each other, and a side surface connected between the first surface and the second surface; along the width direction of the adhesive tape, the adhesive tape covers at least part of the structure of the first surface, the side surface and the second surface in sequence; along the width direction of the adhesive tape, the size of the adhesive tape is c mm, the size of the part of the adhesive tape covering the first surface is a mm, and the size of the part of the adhesive tape covering the second surface is b mm; when the battery is in a 0% SOC state, along the first direction, the vertical distance between the first surface and the second surface is t mm; wherein, T = (cab) / t, 1.0≤T≤1.2; preferably, 1.02≤T≤1.1.

[0010] In an optional embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector; the negative electrode active material layer is bonded to the separator; a plurality of recesses are provided on the negative electrode active material layer at intervals, and the sum of the projected areas of the plurality of recesses along the first direction is S3mm 2 The projected area of ​​the negative electrode active material layer along the first direction is S4 mm 2 ; Among them, M=S3 / S4, 6%≤M≤60%.

[0011] In an optional embodiment, the concave portion is a groove, and the multiple grooves are spaced apart along the second direction; the depth of the groove is 5μm-60μm; and / or the width of the groove is 30μm-180μm; and / or the spacing between two adjacent grooves is 0.5mm-10mm; the second direction is perpendicular to the first direction.

[0012] In an optional embodiment, M / F1≤0.05.

[0013] In a second aspect, the present invention further provides an electrical device, comprising: the above-mentioned battery.

[0014] Utilizing the technical solution of the present invention, a gradient adhesion force design (F3>F1>F2) is employed to optimize the battery's drop resistance and delamination performance. The adhesion force F3 between the shell and the core stack is maximized, effectively securing the entire core stack within the membrane housing. This effectively resists movement of the entire core stack within the housing during a drop from a roller, restraining overall deformation of the core stack and alleviating delamination within the core stack caused by repeated movement and collision with the housing. The negative electrode sheet has a larger projected area along the first direction than the positive electrode sheet, so during a drop, the negative electrode sheet is impacted first. The adhesion force F1 between the separator and the negative electrode sheet is greater than the adhesion force F2 between the separator and the positive electrode sheet. The stronger adhesion between the negative electrode sheet and the separator prevents separation, while the weaker adhesion between the positive electrode sheet and the separator allows for a certain buffer, avoiding stress concentration that can lead to delamination. By designing a gradient adhesion force between the core stack and the shell, as well as between the various components of the core stack, the present invention optimizes the internal stress state and force transmission within the core stack during a drop impact, thereby alleviating delamination within the core stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 is a cross-sectional view of a battery according to an embodiment of the present invention;

[0017] Figure 2 is a cross-sectional view of a battery according to another embodiment of the present invention;

[0018] Figure 3 A schematic diagram of the internal structure of a battery according to an embodiment of the present invention;

[0019] Figure 4 is a cross-sectional view of a battery along a first direction according to an embodiment of the present invention;

[0020] Figure 5This is a schematic structural diagram of a battery adhesive tape according to an embodiment of the present invention;

[0021] Figure 6 This is a schematic structural diagram of a negative electrode sheet of a battery according to an embodiment of the present invention;

[0022] Figure 7 for Figure 6 Partial cross-sectional view along the first direction.

[0023] Description of reference numerals:

[0024] 1. Stacked core; 1a. First surface; 1b. Second surface; 1c. Side surface; 11. Negative electrode sheet; 111. Negative electrode current collector; 112. Negative electrode active material layer; 113. Concave portion; 12. Positive electrode sheet; 13. Separator; 14. First electrode sheet; 15. First edge; 16. Second edge.

[0025] 2. Shell;

[0026] 3. Bonding parts;

[0027] 4. Adhesive tape;

[0028] 5. Earpiece;

[0029] Z, first direction; R - width direction of the adhesive tape. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0031] Laminated batteries are widely used in the field of consumer electronic batteries due to their high energy density and flexible packaging characteristics. Laminated batteries are composed of a laminated core, an electrolyte, and an aluminum-plastic film. The laminated core includes a positive electrode sheet, a negative electrode sheet, and a separator stacked in sequence along the thickness of the battery, with the separator located between the positive and negative electrodes. However, in the drum drop test, the protective plate in the top area of ​​the battery will repeatedly hit the negative electrode sheet due to the impact of the drop, causing significant fluctuations in the bonding force between the negative electrode sheet and the separator. After long-term accumulation, the degradation of the bonding force causes the laminated core to delaminate, that is, the positive or negative electrode sheet and the separator are misaligned, which causes the risk of internal short circuits in the battery to increase sharply.

[0032] Therefore, the embodiments of the present application provide a battery and an electrical device that can solve the above problems.

[0033] The following combination Figures 1 to 7, describing embodiments of the present invention.

[0034] According to an embodiment of the present invention, on one hand, a battery is provided. According to an embodiment of the present invention, on one hand, a battery is provided. In the embodiments of the present application, the battery may be a secondary battery, which refers to a battery that can be recharged to activate the active material after the battery cells are discharged and continue to be used. The battery may be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium metal battery, a sodium metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, etc., and the embodiments of the present application are not limited thereto.

[0035] like Figure 1-Figure 3 As shown, the battery includes an electrode assembly, a shell 2 and an electrolyte (not shown in the figure). Among them, the electrode assembly includes a stacked core 1. The stacked core 1 includes a plurality of negative electrode sheets 11, a plurality of positive electrode sheets 12 and a plurality of separators 13 stacked along a first direction Z. Along the first direction Z, the negative electrode sheets 11 and the positive electrode sheets 12 are alternately arranged. Along the first direction Z, the projected area of ​​the negative electrode sheet 11 is larger than the projected area of ​​the positive electrode sheet 12 to ensure that the negative electrode sheet 11 can cover the positive electrode sheet 12 to avoid lithium plating problems. It can be understood that the first direction Z is also the thickness direction of the stacked core 1, and can also be understood as the thickness direction of the battery. During the charging and discharging process of the battery, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode sheet 12 and the negative electrode sheet 11.

[0036] The diaphragm 13 is arranged between the adjacent negative electrode sheet 11 and the positive electrode sheet 12, and the two opposite surfaces of the diaphragm 13 along the first direction Z are bonded to the negative electrode sheet 11 and the positive electrode sheet 12 respectively. The diaphragm 13 is arranged between the positive electrode sheet 12 and the negative electrode sheet 11, which can prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The diaphragm 13 and the negative electrode sheet 11, as well as the diaphragm 13 and the positive electrode sheet 12, can be bonded by a thermal composite process, an adhesive, or the like. Preferably, the thermal composite process is used to bond, which can not only resist the impact of falling, but also maintain the ion transmission efficiency. The thermal composite process is used to bond the stacked positive electrode sheet 12, the negative electrode sheet 11 and the diaphragm 13 into an integrated laminated structure by heating and pressurizing, that is, the above-mentioned stacked core body 1.

[0037] The positive electrode sheet 12 may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The negative electrode sheet 11 may include a negative electrode current collector 111 and a negative electrode active material layer 112 disposed on at least one surface of the negative electrode current collector. The positive electrode current collector may be aluminum foil or aluminum foil with a plated surface, and the negative electrode current collector 111 may be copper foil or copper foil with a plated surface. The positive electrode active material layer and the negative electrode active material layer 112 may be made of active materials commonly known in the art for use in batteries.

[0038] The positive electrode active material layer includes a positive electrode active material and a positive electrode binder. The positive electrode active material includes one or more of lithium cobalt oxide, lithium iron phosphate, nickel cobalt manganese lithium, nickel cobalt aluminum lithium, lithium manganese oxide, and lithium-rich manganese-based lithium. The positive electrode binder is primarily a polyvinylidene fluoride (PVDF)-based binder.

[0039] The negative electrode active material layer 112 includes a negative electrode active material and a negative electrode binder. The negative electrode active material includes, but is not limited to, one or more of natural graphite, artificial graphite, mesocarbon microbeads, lithium titanate, silicon anode, silicon-carbon anode, and alloy anode. The negative electrode binder is primarily styrene-butadiene rubber.

[0040] Wherein, a conductive agent is provided in both the positive electrode active material layer and the negative electrode active material layer, and the conductive agent includes at least one of conductive carbon black, Ketjen black, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0041] Furthermore, the electrode assembly includes a tab 5, which is located on one side of the length direction of the stacked core 1 and is connected to the electrode sheet of the stacked core 1. The tab 5 can lead the current out of the electrode assembly. Specifically, the tab 5 includes a positive tab 5 and a negative tab 5. The positive tab 5 is connected to the positive electrode sheet 12, and the negative tab 5 is connected to the negative electrode sheet 11. Figure 1-Figure 3 The L direction shown in the figure is perpendicular to the first direction Z, and the L direction can be understood as the length direction of the battery.

[0042] The shell 2 is used to encapsulate components such as the electrode assembly and the electrolyte. The shell 2 can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), or an aluminum-plastic film. The thickness of the shell 2 can be 50-200 μm. For example, the shell 2 is a steel shell, and the steel shell includes a shell portion and a cover portion. The shell portion has a receiving cavity and an opening connected to the receiving cavity, and the electrode assembly and the electrolyte are received in the receiving cavity; the cover portion is connected to the opening of the shell portion and is used to close the opening of the shell portion.

[0043] Specifically, the shell 2 is wrapped around the stacked core 1; the shell 2 is bonded to the stacked core 1 on at least one side along the first direction Z. The shell 2 and the stacked core 1 can be bonded by hot pressing, melting, adhesive, or other methods, preferably adhesive bonding, which is simple and reliable.

[0044] The electrolyte plays a role in conducting ions between the positive and negative electrodes. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0045] The present application has no particular limitation on the type of the diaphragm 13 . For example, any well-known porous structure diaphragm with good chemical stability and mechanical stability can be selected.

[0046] In some embodiments, the bonding force between the separator 13 and the negative electrode sheet 11 is F1 N / m, the bonding force between the separator 13 and the positive electrode sheet 12 is F2 N / m, and the bonding force between the casing 2 and the stacked core 1 is F3 N / m, where F3>F1>F2.

[0047] In some embodiments, the bonding force between the separator 13 and the negative electrode sheet 11 is F1 ≥ 8 N / m, preferably F1 ≥ 10 N / m. The bonding force between the separator 13 and the positive electrode sheet 12 is F2, and the bonding force between the casing 2 and the stacked core 1 is F3 as long as the above relationship is satisfied.

[0048] For example, F1 is 8N / m, F2 is 7N / m, and F3 is 8N / m; for example, F1 is 8N / m, F2 is 7N / m, and F3 is 10N / m; for example, F1 is 8N / m, F2 is 6N / m, and F3 is 8N / m; for example, F1 is 9N / m, F2 is 8N / m, and F3 is 10N / m; for example, F1 is 10N / m, F2 is 8N / m, and F3 is 12N / m; for example, F1 is 12N / m, F2 is 10N / m, and F3 is 13N / m; and so on.

[0049] In this embodiment, a gradient adhesion design (F3 > F1 > F2) optimizes the battery's drop resistance and delamination performance. The adhesion F3 between the housing 2 and the core stack 1 is maximized, effectively securing the entire core stack 1 within the membrane housing. This effectively resists movement of the entire core stack 1 within the housing 2 during a roller drop, restraining overall deformation of the core stack 1 and mitigating internal delamination of the core stack 1 caused by repeated movement and collision with the housing 2. The negative electrode sheet 11 has a larger projected area along the first direction Z than the positive electrode sheet 12. During a drop, the negative electrode sheet 11 is impacted first. The adhesion F1 between the separator 13 and the negative electrode sheet 11 is greater than the adhesion F2 between the separator 13 and the positive electrode sheet 12. The stronger adhesion between the negative electrode sheet 11 and the separator 13 prevents separation, while the weaker adhesion between the positive electrode sheet 12 and the separator 13 allows for some cushioning, preventing stress concentration that can lead to delamination. The present invention optimizes the stress state and force transmission inside the stacked core during drop impact and improves the internal delamination problem of the stacked core by designing the adhesive force gradient between the stacked core 1 and the shell 2 and between the components of the stacked core 1.

[0050] It should be noted that, in the present invention, the bonding force F1 between the separator 13 and the negative electrode sheet 11, the bonding force F2 between the separator 13 and the positive electrode sheet 12, and the bonding force F3 between the shell 2 and the stacked core 1 all refer to the bonding force when the battery is in the 0% SOC (States of Charge) state.

[0051] In the first direction Z, the stacked core 1 has a first electrode piece 14 located on the outermost side. The first electrode piece 14 is bonded to the housing 2. The bonding force between the housing 2 and the stacked core 1 is F3, which is the bonding force between the housing 2 and the first electrode piece 14. The first electrode piece 14 can be the positive electrode piece 12 or the negative electrode piece 11.

[0052] The adhesion force F1 between the separator 13 and the negative electrode sheet 11, the adhesion force F2 between the separator 13 and the positive electrode sheet 12, and the adhesion force F3 between the housing 2 and the stacked core 1 can all be characterized by peeling force. Specifically, the adhesion force F1 between the separator 13 and the negative electrode sheet 11 refers to the force required to separate the separator 13 from the negative electrode sheet 11; the adhesion force F2 between the separator 13 and the positive electrode sheet 12 refers to the force required to separate the separator 13 from the positive electrode sheet 12; and the adhesion force F3 between the housing 2 and the stacked core 1 refers to the force required to separate the housing 2 from the stacked core 1. In some cases, the housing 2 and the stacked core 1 are bonded together using an adhesive 3, such as a hot melt adhesive. During the peel test, the adhesive 3 may remain on either the housing 2 or the stacked core 1. If the adhesive member 3 remains on the shell 2, the bonding force F3 between the shell 2 and the laminated core 1 is the bonding force between the laminated core 1 and the adhesive member 3. If the adhesive member 3 remains on the laminated core 1, the bonding force F3 between the shell 2 and the laminated core 1 is the bonding force between the shell 2 and the adhesive member 3. That is, the bonding force F3 between the shell 2 and the laminated core 1 specifically refers to the minimum of the bonding force between the shell 2 and the adhesive member 3 and the bonding force between the laminated core 1 and the adhesive member 3. Furthermore, in some embodiments, 1.2 ≤ F3 / F1 ≤ 4.0. For example, the ratio F3 / F1 can be 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8, 4.0, or a range consisting of any of the foregoing values.

[0053] Optionally, 1.5≤F3 / F1≤4.0; 1.5≤F3 / F1≤3.8; 1.5≤F3 / F1≤3.5; 1.5≤F3 / F1≤3.2; 1.5≤F3 / F1≤3.0; 1.8≤F3 / F1≤4.0; 1.8≤F3 / F1≤3.8; 1.8≤F3 / F1≤3.5; 1.8≤F3 / F1≤3.2; 1.8≤F3 / F1≤3.0; 2≤F3 / F1≤4.0; 2≤F3 / F1≤3.8; 2≤F3 / F1≤3.5; 2≤F3 / F1≤3.2; 2≤F3 / F1≤3.0. Preferably, 2.0≤F3 / F1≤3.0.

[0054] In this embodiment, when the above relationship is satisfied, sufficient dispersion of stress inside and outside the battery can be ensured, so that the entire battery is evenly stressed, avoiding local stress concentration leading to internal delamination. Experimental verification shows that when F3 / F1 is less than 1.2, F3 is too small relative to F1, and the connection between the entire stacked core 1 and the shell 2 is not strong enough. When rolling and falling, the stacked core 1 is easily separated from the shell 2, and the stacked core 1 moves within the shell 2. The positive and negative electrodes 12 and 11 of the stacked core 1 collide with the shell 2, causing wrinkles, deformation, and internal delamination of the electrodes. When F3 / F1 is greater than 4, F3 is too large relative to F1. On the one hand, when rolling and falling, the stress on the shell 2 is easily concentrated on the shell 2 and the electrode of the stacked core 1 connected to the shell 2, causing delamination of the electrode connected to the shell 2 and the internal structure of the stacked core 1. On the other hand, the shell 2 restricts the natural deformation of the electrode, causing stress to be concentrated in the bonding area between the shell 2 and the stacked core 1. Long-term cyclic expansion or external force impact can easily cause electrode fracture or shell 2 delamination.

[0055] Furthermore, in some embodiments, 0.3≤F2 / F1≤0.8. For example, the ratio of F2 / F1 can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, or a range consisting of any of the above values.

[0056] Optionally, 0.35≤F2 / F1≤0.8; 0.35≤F2 / F1≤0.75; 0.35≤F2 / F1≤0.7; 0.35≤F2 / F1≤0.65; 0.4≤F2 / F1≤0.8; 0.4≤F2 / F1≤0.75; 0.4≤F2 / F1≤0.7; 0.4≤F2 / F1≤0.65; 0.5≤F2 / F1≤0.8; 0.5≤F2 / F1≤0.75; 0.5≤F2 / F1≤0.7; 0.5≤F2 / F1≤0.65. Preferably, 0.5≤F2 / F1≤0.7.

[0057] In this embodiment, because the projected area of ​​the negative electrode sheet 11 along the first direction Z is larger than the projected area of ​​the positive electrode sheet 12 along the first direction Z, when the battery is dropped, the protective plate impacts the negative electrode sheet 11. Therefore, it is necessary to ensure strong adhesion between the negative electrode sheet 11 and the separator 13. When F1 and F2 satisfy the aforementioned relationship, the stress on the negative electrode sheet 11 can be better distributed to the positive electrode sheet 12, thereby preventing delamination caused by a significant difference in the forces acting on the negative and positive electrode sheets 11, 12. Experimental verification shows that if F2 / F1 is less than 0.3, F2 is too small relative to F1. During the drum drop test, the stress of the positive electrode sheet 12 and the negative electrode sheet 11 is unevenly dispersed, and the stress is easily concentrated between the positive electrode sheet 12 and the diaphragm 13, causing the positive electrode sheet 12 and the diaphragm 13 to be displaced, thereby causing internal delamination of the stacked core 1; when F2 / F1 is greater than 0.8, F2 is too large relative to F1. During the drum drop test, the stress is easily concentrated between the negative electrode sheet 11 and the diaphragm 13, causing the negative electrode sheet 11 and the diaphragm 13 to be displaced, thereby causing internal delamination of the stacked core 1.

[0058] It should be noted that the bonding force F1 between the separator 13 and the negative electrode sheet 11 , the bonding force F2 between the separator 13 and the positive electrode sheet 12 , and the bonding force F3 between the casing 2 and the stacked core 1 can all be tested using methods and instruments known in the art.

[0059] For example, the test method for F1 and F2 may be: disassembling the battery cell to obtain at least 5 groups of samples containing the diaphragm 13-pole piece interface; using a universal material testing machine to peel off the 5 groups of samples containing the diaphragm 13-pole piece interface respectively, with the steel plate of the universal material testing machine fixing the diaphragm 13 and the clamp of the universal material testing machine clamping the pole piece; after preloading 0.1N tension to eliminate relaxation, the pole piece is uniformly peeled off the diaphragm 13 at a speed of 50mm / min in a direction perpendicular to the coating direction of the pole piece; recording the peeling force-displacement curve, taking the valid data segment in the middle section of the displacement, and the average value of each peeling force is the value of the adhesion force F1 or F2.

[0060] For example, the test method for F3 can be as follows: disassemble the battery cell to obtain samples of the shell 2-electrode piece interface; use a universal material testing machine to peel off five groups of samples containing the shell 2-electrode piece interface, with the steel plate of the universal material testing machine fixing the shell 2 and the fixture of the universal material testing machine clamping the electrode; after preloading 0.1N tension to eliminate relaxation, peel the electrode piece from the shell at a constant speed of 50mm / min in a direction perpendicular to the coating direction of the electrode piece; record the peeling force-displacement curve, and take the valid data segment in the middle of the displacement as the value of the bonding force F3. Among them, the two sides of the diaphragm 13 are respectively bonded to the negative electrode piece 11 and the positive electrode piece 12, in order to achieve that the bonding force F1 between the diaphragm 13 and the negative electrode piece 11 is greater than the bonding force F2 between the diaphragm 13 and the positive electrode piece 12.

[0061] In some embodiments, the diaphragm 13 includes a base film, a heat-resistant layer, and two adhesive layers. Along a first direction Z, the heat-resistant layer is disposed on one side of the base film; and along the first direction Z, one of the two adhesive layers is disposed on a side of the base film away from the heat-resistant layer, while the other is disposed on a side of the heat-resistant layer away from the base film.

[0062] In some embodiments, the heat-resistant layer includes heat-resistant particles and a heat-resistant layer binder, wherein the heat-resistant particles account for 90%-99% of the mass of the heat-resistant layer, and the heat-resistant layer binder accounts for 1%-10% of the mass of the heat-resistant layer. The heat-resistant particles include one or more of boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin oxide, titanium oxide, barium titanate, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, and melamine thiocyanate. The heat-resistant layer binder includes one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polymethyl methacrylate, polybutyl methacrylate, styrene-acrylic latex, polyacrylonitrile, polyethyl acrylate, polyvinyl acetate, polyacrylic acid, polyacrylate, polyurethane polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, or copolymer systems derived from the above polymers.

[0063] In some embodiments, the bonding layer is discontinuously arranged. Along the first direction Z, the projected area of ​​the bonding layer on the heat-resistant layer accounts for 10% to 50% of the area of ​​the heat-resistant layer. Specifically, the bonding layer includes polymer particles. The polymer particles include a first polymer, and the first polymer includes a polymer formed by copolymerization of at least one monomer selected from methyl methacrylate, ethyl methacrylate, isooctyl acrylate, n-propyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate, styrene, butadiene, methacrylamide, acrylamide, acrylonitrile, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, and hexafluoropropylene.

[0064] Furthermore, the average particle size of the primary particles of the polymer particles is 0.2 μm to 1 μm. When the polymer particles are based on a monomer containing an ester group, the polymer particles are arranged in a single layer in the adhesive layer. When the polymer particles are based on a monomer containing a fluorine element, the polymer particles contain secondary particles (particles formed by agglomeration of four or more primary particles) in the adhesive layer, and the average particle size of the secondary particles is 5 μm to 15 μm.

[0065] It should be noted that the average particle size of the primary and secondary particles of the polymer particles can be measured using methods and instruments known in the art. For example, a scanning electron microscope (SEM) measurement method is used: the battery is disassembled to obtain the separator 13; a sample of the separator 13 containing the adhesive layer is dried and fixed, etc.; the sample is placed in the SEM device, and an appropriate acceleration voltage and magnification are selected to obtain a high-resolution image of the polymer particles; the particle size of the polymer particles is directly measured on the image using the image processing software provided by the SEM; and the average particle size is calculated by measuring the maximum diameter, minimum diameter, or equivalent diameter of the polymer particles.

[0066] In other embodiments, the bonding layer is continuously provided and has a porous structure. The bonding layer includes a polymer and inorganic particles, the polymer accounts for 40%-70% by mass of the bonding layer, and the inorganic particles account for 30%-60% by mass of the bonding layer. The polymer includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. Inorganic particles include one or more of boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), melamine thiocyanate, melamine cyanurate, and symmetrical triaminotriazine.

[0067] Furthermore, the positive electrode sheet 12 may include the aforementioned positive electrode active material layer, which includes a PVDF (polyvinylidene fluoride) binder. The negative electrode sheet 11 may include the aforementioned negative electrode active material layer 112, which includes a styrene-butadiene rubber binder. The bonding force between the styrene-butadiene rubber binder and the adhesive layer of the separator 13 can be greater than the bonding force between the PVDF binder and the adhesive layer of the separator 13, thereby achieving F1>F2.

[0068] Furthermore, of the two adhesive layers on both sides of the separator 13 along the first direction Z, one is connected to the positive electrode sheet 12, and the other is connected to the negative electrode sheet 11. By adjusting the thickness, composition, particle size, coating area, etc. of the two adhesive layers on both sides of the separator 13 along the first direction Z, the magnitudes of F1 and F2 can also be controlled to achieve F1>F2.

[0069] Furthermore, in some embodiments, the negative electrode active material layer 112 further includes a silicon-based material selected from one or more of elemental silicon, silicon oxides (e.g., SiOx / C), silicon-carbon composites (e.g., Si / C), silicon-nitrogen composites, and silicon alloys, wherein the average particle size of the silicon-carbon material is 6 μm to 12 μm. The silicon-based material in the negative electrode active material layer 112 can achieve a balance between electrochemical performance, slurry rheology, and electrode uniformity, providing a suitable working environment for the binder, thereby improving the bonding strength between the negative electrode sheet 11 and the separator 13, thereby achieving a bonding strength F1 between the separator 13 and the negative electrode sheet 11 greater than the bonding strength F2 between the separator 13 and the positive electrode sheet 12.

[0070] Of course, the bonding force between the negative electrode sheet 11 and the separator 13 can also be improved by adjusting the battery formation process parameters, such as increasing the formation pressure; increasing the formation temperature to slightly increase the bonding force, etc., so as to achieve F1>F2.

[0071] Furthermore, in some embodiments, the battery includes the aforementioned adhesive member 3, and the casing 2 is bonded to at least one side of the stacked core 1 along the first direction Z via the adhesive member 3. The adhesive member 3 comprises at least one of acrylic acid, methacrylate, and rubber; wherein the rubber comprises at least one of polyisobutylene, styrene-butadiene-styrene triblock copolymer (SIS), styrene-isoprene-styrene triblock copolymer (SBS), and styrene-ethylene-butylene-styrene block copolymer (SEBS). The stacked core 1 includes a first pole piece 14 bonded to the adhesive member 3. The first pole piece 14 is specifically the outermost pole piece of the stacked core 1 along the first direction Z. The pole piece can be either the positive pole piece 12 or the negative pole piece 11.

[0072] For example, Figure 1 As shown, along the first direction Z, an adhesive member 3 is provided on one side of the stacked core 1, and the adhesive member 3 is bonded between the first pole piece 14 and the housing 2. Specifically, the housing 2 has a deep pit surface and a shallow pit surface that are opposite to each other along the first direction Z. The adhesive member 3 can be disposed in the deep pit surface or the shallow pit surface. Preferably, the adhesive member 3 can be disposed in the deep pit surface. In this manner, the anti-drop performance of the stacked core 1 is better when the adhesive member 3 is attached between the deep pit surface and the first pole piece 14 than when the adhesive member 3 is attached between the shallow pit surface and the first pole piece 14.

[0073] For example, Figure 2 As shown, along the first direction Z, adhesive members 3 are provided on both sides of the stacked core 1, and the adhesive members 3 on both sides of the stacked core 1 are respectively bonded between the first pole pieces 14 and the housing 2 on both sides of the stacked core 1. In other words, the adhesive members 3 on both sides of the stacked core 1 are respectively arranged in the deep pit surface and the shallow pit surface. In this way, the drop resistance of the stacked core 1 is better than that when the adhesive members 3 are attached between the deep pit surface and the first pole piece 14.

[0074] Furthermore, in some embodiments, the projection area of ​​the first pole piece 14 along the first direction Z is S1mm 2 The projection area of ​​the adhesive member 3 along the first direction Z is S2 mm 2 ; 30%≤S2 / S1≤80%. It should be noted that, in this embodiment, as long as the first pole piece 14 on at least one side of the stacked core 1 along the first direction Z and the bonding member 3 bonded thereto satisfy 30%≤S2 / S1≤80%, it is sufficient.

[0075] Exemplarily, the battery includes an adhesive member 3 bonded between the first pole piece 14 and the housing 2. Here, S1 refers to the projected area of ​​the first pole piece 14 along the first direction Z, and S2 refers to the projected area of ​​the adhesive member 3 along the first direction Z. The ratio of the projected area of ​​the first pole piece 14 along the first direction Z to the projected area of ​​the adhesive member 3 along the first direction Z satisfies the following conditions: 30% ≤ S2 / S1 ≤ 80%.

[0076] Exemplarily, the battery includes two adhesive members 3, which are respectively bonded between the first pole piece 14 and the shell 2 on both sides of the stacked core 1. For ease of description, the two first pole pieces 14 on both sides of the stacked core 1 are respectively the first sub-pole piece and the second sub-pole piece, and the two adhesive members 3 are respectively the first sub-adhesive member and the second sub-adhesive member. The first sub-adhesive member is bonded between the first sub-pole piece and the shell 2, and the second sub-adhesive member is bonded between the second sub-pole piece and the shell 2. At this time, when S1 refers to the projected area of ​​the first sub-pole piece along the first direction Z, S2 refers to the projected area of ​​the first sub-adhesive member along the first direction Z, and the ratio of the projected area of ​​the first sub-pole piece along the first direction Z to the projected area of ​​the first sub-adhesive member along the first direction Z satisfies: 30% ≤ S2 / S1 ≤ 80%. When S1 refers to the projected area of ​​the second sub-pole piece along the first direction Z, and S2 refers to the projected area of ​​the second sub-adhesive member along the first direction Z, the ratio of the projected area of ​​the second sub-pole piece along the first direction Z to the projected area of ​​the second sub-adhesive member along the first direction Z satisfies: 30% ≤ S2 / S1 ≤ 80%. It is understood that at least one of the ratio of the projected area of ​​the first sub-pole piece along the first direction Z to the projected area of ​​the first sub-adhesive member along the first direction Z, and the ratio of the projected area of ​​the second sub-pole piece along the first direction Z to the projected area of ​​the second sub-adhesive member along the first direction Z, satisfies: 30% ≤ S2 / S1 ≤ 80%.

[0077] For example, S2 / S1 may be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or a range consisting of any of the above values.

[0078] Optionally, 35%≤S2 / S1≤80%; 35%≤S2 / S1≤75%; 35%≤S2 / S1≤70%; 35%≤S2 / S1≤65%; 40%≤S2 / S1≤80%; 40%≤S2 / S1≤75%; 40%≤S2 / S1≤70%; 40%≤S2 / S1≤65%, etc. Preferably, 40%≤S2 / S1≤70%.

[0079] In this embodiment, when S2 / S1 satisfies the aforementioned relationship, it is possible to ensure that the adhesive 3 has a sufficient area share to improve the transfer of stress throughout the core stack, ensuring that there are sufficient stress transfer sites, thereby improving the internal delamination problem of the core stack during the roller drop test. When S2 / S1 is less than 30%, the area of ​​the adhesive 3 is too small, and the bonding force between the shell 2 and the core stack 1 is insufficient. When the core stack 1 is dropped, the shell 2 and the core stack 1 are easily separated, which in turn causes the core stack 1 to move during the drop and cause delamination. When S2 / S1 is greater than 80%, on the one hand, the area of ​​the adhesive 3 is too large, and the bonding force between the shell 2 and the core stack 1 is too strong. When the core stack 1 is dropped, the outermost electrode of the core stack, i.e., the first electrode 14, is easily broken. On the other hand, the excessive area of ​​the adhesive 3 causes the adhesive 4 surrounding the core stack 1 to overlap, resulting in increased thickness and loss of ED. For example, each bonding member 3 includes at least one bonding portion, at least one bonding portion is located in the middle of the first pole piece 14, and is arranged at intervals to ensure uniform arrangement of stress transfer points and improve uniformity of stress transfer. Figure 3 As shown, the adhesive member 3 includes two adhesive portions, which are spaced apart and rectangular, and the first pole piece 14 is rectangular. Along the width direction of the battery, that is, the width direction of the first pole piece 14, that is, Figure 3 In the W direction, the width of the bonding portion is W1, and the width of the first electrode 14 is W2; along the length direction of the battery, that is, the length direction of the first electrode 14, that is Figure 3 In the L direction, the length of the bonding portion is L1, and the length of the first pole piece 14 is L2. At this time, the projection area of ​​the first pole piece 14 along the first direction Z is S1 = L2 * W2; the projection area of ​​the bonding member 3 along the first direction Z is S2 = 2 * L1 * W1.

[0080] It is understandable that the bonding portion can also be set to one, three, four or more. For example, the bonding portions can be spaced apart to form n (n ≥ 2) bonding portions, and the bonding portions are evenly arranged in the middle of the first pole piece 14; the bonding portion is circular, and the radius of the bonding portion is r. In this case, the projected area of ​​the bonding member 3 along the first direction Z is S2 = n*πr 2 .

[0081] Furthermore, in some embodiments, Figure 3-Figure 5As shown, the battery includes adhesive tape 4, which is applied to the edge of the core stack 1 to encapsulate the edge of the core stack 1 and ensure its integrity. Specifically, the core stack 1 has a first surface 1a and a second surface 1b, which are opposite each other, and a side surface 1c connecting the first and second surfaces 1a and 1b. Along the width direction R of the adhesive tape, the adhesive tape 4 sequentially covers at least a portion of the first surface 1a, the side surface 1c, and the second surface 1b. Along the width direction R, the adhesive tape 4 has a dimension of c mm, with the portion covering the first surface 1a measuring a mm and the portion covering the second surface 1b measuring b mm. When the battery is at 0% SOC, the vertical distance between the first surface 1a and the second surface 1b along the first direction Z is t mm. It can be understood that the vertical distance between the first and second surfaces 1a and 1b is also the thickness of the core stack 1.

[0082] Wherein, T=(cab) / t, 1.0≤T≤1.2. For example, T can be 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, or any range thereof.

[0083] It can be understood that T represents the tightness of the adhesive tape 4 . The larger the T value, the looser the tightness, and the smaller the T value, the tighter the tightness.

[0084] In this embodiment, when the tightness of the adhesive tape 4 satisfies 1.0 ≤ T ≤ 1.2, uniform stress transfer within the stacked core 1 can be ensured, effectively mitigating delamination within the stacked core 1. Specifically, when the adhesive tape 4 is applied too loosely (T > 1.2), it fails to provide sufficient fixation and restraint for the stacked core 1, and relative displacement between the layers of the stacked core 1 is likely to occur, resulting in a disordered stress distribution and, in the event of a fall, delamination of the stacked core 1.

[0085] Preferably, when 1.02≤T≤1.1, the stress transfer uniformity and anti-delamination effect are more prominent, which can further optimize the structural performance of the stacked core 1 and meet the high quality requirements of the battery in complex usage scenarios. Figure 3 As shown, the battery includes the aforementioned tab 5, which is connected to one side of the stacked core 1 along the L direction. The stacked core 1 has a second edge 16 disposed opposite the tab 5 along the L direction, and two first edges 15 connected to both sides of the second edge 16 along the W direction. The two second edges 16 are located on both sides of the tab 5 along the W direction. At least one piece of adhesive tape 4 is disposed on each of the first edges 15 and the second edge 16, and the tightness of each piece of adhesive tape 4 satisfies 1.0 ≤ T ≤ 1.2.

[0086] Furthermore, in some embodiments, when the battery is at 100% SOC, the vertical distance between the first surface 1a and the second surface 1b along the first direction Z is t1 mm, where d = t1-t. Wherein, 5d ≥ T ≥ 1.1d. For example, T can be 1.1d, 1.5d, 2d, 2.5d, 3d, 3.5d, 4d, 4.5d, 5d, or a range consisting of any of the above relationships. It is understood that the value of d depends on the battery's own expansion properties, and d is between 0.06t and 0.25t, and the value of t is between 1mm and 11mm.

[0087] In this embodiment, when the tightness of the adhesive tape 4 satisfies 5d ≥ T ≥ 1.1d, the stress of the battery can be evenly distributed during the drop, preventing uneven stress on the pole pieces of the stacked core 1 and delamination. When T < 1.1d, the edge of the pole piece can easily cause the adhesive tape 4 to tear during the drop, causing delamination of the stacked core 1 and problems such as pole piece misalignment and short circuit. When T > 5d, the stress of the battery is unevenly distributed during the drop, causing delamination of the stacked core 1 and pole piece failure.

[0088] Furthermore, in some embodiments, Figure 6 and Figure 7 As shown, the negative electrode sheet 11 includes a negative electrode current collector 111 and a negative electrode active material layer 112 disposed on at least one surface of the negative electrode current collector 111. The negative electrode active material layer 112 is bonded to the separator 13. A plurality of recesses 113 are spaced apart on the negative electrode active material layer 112. The sum of the projected areas of the plurality of recesses 113 along the first direction Z is S3 mm. 2 The projection area of ​​the negative active material layer 112 along the first direction Z is S4 mm 2 . Among them, M=S3 / S4, 6%≤M≤60%.

[0089] For example, M can be 6%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range consisting of any of the above values.

[0090] In this embodiment, the recess 113 is provided to reduce the expansion rate of the negative electrode sheet 11, thereby improving the bond strength between the separator 13 and the negative electrode caused by the expansion of the negative electrode sheet 11 during battery cycling, and further alleviating the internal delamination problem of the stack 1 during battery drops. When M is between 6% and 60%, the recess 113 in the negative active material layer 112 effectively buffers the stress generated by the expansion of the active material during cycling. When M ≥ 6%, the recess 113 ensures sufficient space to accommodate expansion deformation, preventing stress concentration and cracking at the bonding interface, thereby ensuring the bond strength between the negative electrode sheet 11 and the separator 13 and mitigating the bond strength degradation after cycling. When M ≤ 60%, a sufficient proportion of the active material surface area is retained to maintain the bond strength with the separator 13, preventing the contact area from being weakened due to an excessive proportion of the recess 113. This balances expansion buffering with bond strength and slows bond strength degradation. If M is less than 6%, the area of ​​the recess 113 is too small to effectively buffer the expansion deformation of the negative electrode sheet 11, and thus cannot effectively alleviate the weakening of the bonding strength between the negative electrode sheet 11 and the separator 13 caused by cyclic expansion. If M is greater than 60%, the area of ​​the negative electrode active material layer 112 is too small, making it difficult for the negative electrode active material layer 112 to maintain its bonding strength with the separator 13, resulting in weakening of the bonding strength between the negative electrode sheet 11 and the separator 13 after cycling. The present invention does not impose specific restrictions on the specific configuration and shape of the recess 113, as long as it can achieve the function of alleviating the weakening of the bonding strength between the separator 13 and the negative electrode caused by the expansion of the negative electrode sheet 11. The recess 113 can be formed using laser scribing technology.

[0091] For example, the recesses 113 may be a plurality of pits, grooves, etc., which are arranged at intervals on the negative electrode active material layer 112 , and are preferably arranged at intervals.

[0092] In some embodiments, as Figure 5 and Figure 6 As shown, the recess 113 is a groove, and a plurality of grooves are spaced apart along the second direction, and the second direction is perpendicular to the first direction Z. Setting the recess 113 as a groove can increase the electrolyte contained, further enhance the swelling of the glue layer in the diaphragm 13 and the negative electrode sheet 11, and thereby improve the problem of weakened adhesion of the negative electrode sheet 11 due to expansion during the battery cycle. It can be understood that the length direction L and the width direction W of the battery are both perpendicular to the first direction Z, and the second direction can be any direction within the plane where the direction L and the direction W are located. The second direction can be parallel to the direction L, or to the direction W, or at an angle to both the direction L and the direction W. Preferably, the second direction is parallel to the direction L to facilitate laser scribing.

[0093] For example, the depth of the groove may be 5 μm-60 μm, wherein the depth of the groove specifically refers to the dimension of the groove in the first direction Z, that is, Figure 7For example, the depth of the groove may be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, or a range thereof.

[0094] For example, the width of the groove may be 30 μm to 180 μm, wherein the width of the groove specifically refers to the size of the groove in the second direction, that is, Figure 6 or Figure 7 For example, the width of the groove may be 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, or a range thereof.

[0095] For example, along the second direction, the spacing between two adjacent grooves is 0.5mm-10mm. Figure 6 or Figure 7 For example, along the second direction, the spacing between two adjacent grooves can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, or any range thereof.

[0096] Furthermore, in some embodiments, M / F1≤0.05, that is, the ratio of M to F1≤0.05. For example, the ratio of M / F1 can be 0.05, 0.045, 0.04, 0.035, 0.03, 0.025, 0.02, 0.015, 0.01, or a range consisting of any of the above values.

[0097] In this embodiment, the recess 113 in the negative active material layer 112 of the negative electrode sheet 11 slightly reduces the bonding area between the negative electrode sheet 11 and the separator 13, weakening the adhesion between the separator 13 and the negative electrode sheet 11. However, the electrolyte in the recess 113 allows the glue layer in the separator 13 and the negative electrode sheet 11 to swell more effectively, which in turn improves the adhesion between the two. Experimental verification shows that when M / F1 ≤ 0.05, the adhesion increased by swelling can be greater than or equal to the adhesion weakened by the reduced bonding area, further improving the weakened adhesion between the separator 13 and the negative electrode caused by the expansion of the negative electrode sheet 11, thereby alleviating the delamination problem within the stacked core during the drop process. If M / F1>0.05, the proportion of the concave portion 113 to the negative electrode active material layer 112 is too large relative to F1, and the swelling of the glue layer generated by the concave portion 113 is insufficient to offset the attenuation of the bonding force caused by the reduction in the bonding area between the negative electrode active material layer 112 and the separator 13, and thus the attenuation problem of F1 during the cycle cannot be alleviated.

[0098] Furthermore, the stacked core body 1 bonds the stacked positive electrode sheet 12 to the separator 13, and also bonds the negative electrode sheet 11 to the separator 13, through the aforementioned thermal lamination process. In some embodiments, before the positive electrode sheet 12, the negative electrode sheet 11, and the separator 13 are stacked, the negative electrode sheet 11 and the separator 13 are bonded together through a thermal lamination process, and then the stacked positive electrode sheet 12, the negative electrode sheet 11, and the separator 13 are bonded into an integrated laminate structure through a secondary thermal lamination process. This arrangement can increase the bonding strength between the negative electrode sheet 11 and the separator 13, alleviate the problem of easy delamination of the negative electrode sheet 11 and the separator 13 during a drop, thereby improving the delamination problem of the stacked core body 1 during a drop, reducing the risk of internal short circuits within the battery, and improving the safety performance of the battery.

[0099] According to another aspect of an embodiment of the present invention, an electrical device is provided, comprising the battery described above, the battery being used to provide electrical energy to the electrical device. The electrical device of the present invention comprises the battery of the present invention, and thus has the same technical effects as the battery of the present invention, and thus will not be further described herein.

[0100] The electrical equipment of the present invention can be any device that uses a battery. For example, the electrical equipment can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, and the like; the spacecraft includes airplanes, rockets, space shuttles, and spacecraft, and the like; the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0101] Example

[0102] Example 1-1

[0103] Method for preparing lithium-ion battery

[0104] Step 1: prepare a positive electrode active material layer slurry, apply the positive electrode active material layer slurry on the surface of the aluminum foil, and obtain the positive electrode sheet 12 through baking, rolling, and slitting.

[0105] Among them, the preparation method of the positive electrode active material layer is as follows: lithium cobalt oxide, conductive carbon material (Super P: carbon nanotube = 2:1, weight ratio), and binder PVDF are mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 97.6:1.35:1.05, and continuously stirred in a stirrer to form a uniform, flowing positive electrode active material layer slurry.

[0106] Step 2: Prepare the negative electrode active material layer 112 slurry, apply the negative electrode active material layer 112 slurry on the carbon-coated copper foil, and obtain the negative electrode sheet 11 through baking, laser scribing, roller pressing, and slitting.

[0107] The negative electrode active material layer 112 is prepared as follows: graphite, silicon-carbon material, conductive carbon black (Super P), carboxymethyl cellulose, and styrene-butadiene rubber are mixed in deionized water at a weight ratio of 91:6:0.5:1.3:1.2, and the mixture is continuously stirred in a blender to form a uniform, fluid slurry of the negative electrode active material layer 112.

[0108] In this step, laser scribing is used to form the recessed portion 113 on the negative electrode active material layer 112. By adjusting the scribing density of the laser scribing, the value of M and the ratio of M / F1 can be controlled.

[0109] Step 3: The positive electrode sheet 12 and the negative electrode sheet 11 are die-cut and laminated to obtain a laminated core 1.

[0110] In the thickness direction of the stacked core 1 , the outermost electrode sheets on both sides of the stacked core 1 are both positive electrode sheets 12 , and the two outermost positive electrode sheets 12 of the stacked core 1 form a first electrode sheet 14 .

[0111] Step 4: Paste adhesive tape 4 and adhesive member 3 on the outside of the stacked core 1.

[0112] When pasting the adhesive tape 4, the tightness of the adhesive tape 4 on the stacked core 1 is controlled by controlling the tension of the adhesive tape 4 on the adhesive tape roll, that is, the value of T.

[0113] The adhesive member 3 is attached to one side of the stacked core 1 along the first direction Z. By selecting adhesive members 3 of different sizes, the adhesive force F3 between the housing 2 and the stacked core 1 can be controlled, as well as the ratio S2 / S1.

[0114] Step 5: The aluminum-plastic film is punched through a mold core to obtain a shell 2.

[0115] Step 6: After the stacked core 1 is placed in the housing 2, the lithium-ion battery is packaged, baked, injected, formed, sorted, sealed, OCV, and packaged. During the formation process, the bonding force F1 between the separator 13 and the negative electrode sheet 11 and the bonding force F2 between the separator 13 and the positive electrode sheet 12 are controlled by adjusting the formation pressure and temperature.

[0116] The lithium-ion batteries in the examples and comparative examples of the present application were prepared using the same method as in Example 1-1.

[0117] The following test methods were used for the various examples and comparative examples of the present application:

[0118] 1. Drum drop test: At room temperature, charge the battery using a 0.5C constant current and constant voltage to the charge limit voltage. Using a battery-specific drum drop test fixture, perform a drum drop test, dropping the battery from a height of 1m at a speed of 5 cycles / min for 306 cycles (two drops constitute one cycle). After 306 cycles, inspect the battery cell for damage and leakage, and measure the cell open-circuit voltage. Charge the battery at room temperature using a 0.2C constant current and constant voltage to the limit voltage. The battery is then disassembled to confirm the probability of delamination of the core stack 1, the separation between the shell 2 and the core stack 1, the tearing of the adhesive tape 4, and the appearance of each electrode in the core stack 1.

[0119] The probability of delamination of the stack 1 is calculated as follows: 1000 batteries are selected as the total sample. After the 1000 batteries are subjected to the drum drop test, the batteries are disassembled and the appearance of the stack 1 is directly observed to determine whether it is delaminated. The probability of delamination of the stack 1 = (number of delaminated batteries / 1000) * 100%.

[0120] The peeling condition between the shell 2 and the stacked core 1 and the tearing condition of the adhesive tape 4 can be determined by directly observing the appearance of the stacked core 1 after disassembling the battery.

[0121] The appearance of each pole piece of the stacked core body 1 can be determined by obtaining image information of each pole piece through CT scanning, and judging whether each pole piece is wrinkled, deformed, broken or flat based on the image information.

[0122] 2. Cycle test:

[0123] Room Temperature Cycling Test: In a 25°C environment, the electrode assembly was charged at a constant current of 1C to the full charge voltage (the battery's maximum design voltage is 4.5V). Constant voltage charging was then performed at maximum voltage until the current reached 0.02C. Constant current discharge was then performed at a discharge current of 0.7C until the final voltage reached 3.0V. The discharge capacity of the first cycle was recorded. The above conditions and steps were repeated for 500 charge and discharge cycles, and the adhesion between the negative electrode sheet 11 and the separator 13 was tested.

[0124] The test method for the adhesion between the negative electrode sheet 11 and the separator 13 after 500 cycles is the same as the test method F3 above, and will not be repeated here.

[0125] The differences between Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-14 are that the bonding force F1 between the separator 13 and the negative electrode sheet 11, the bonding force F2 between the separator 13 and the positive electrode sheet 12, and the bonding force F3 between the casing 2 and the stacked core 1 are different. See Table 1 for details:

[0126]

[0127]

[0128] Table 1

[0129] According to the test results in Table 1, it can be seen that the test results of Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-14 show that making F3>F1>F2 can reduce the probability of delamination of the stacked core, thereby effectively alleviating the delamination problem of the stacked core 1 when the battery falls.

[0130] Combined with the test results of Examples 1-1 to 1-7, it can be seen that setting 1.2≤F3 / F1≤4.0 can further improve the delamination problem of the stacked core 1, avoid local stress concentration, ensure the flatness of each electrode in the stacked core 1, and thus ensure the safety performance of the battery.

[0131] Combined with the test results of Examples 1-8 to 1-14, it can be seen that: setting 0.3≤F2 / F1≤0.8 can better disperse the stress on the negative electrode sheet 11 to the positive electrode sheet 12, thereby preventing the negative electrode sheet 11 and the positive electrode sheet 12 from being subjected to excessive force differences and causing stratification, and further improving the stratification problem of the stacked core 1 during the battery falling process.

[0132] The difference between Examples 2-1 to 2-7 and Example 1-1 is that a special setting is made for the ratio of the projected area S2 of the adhesive member 3 along the first direction Z to the projected area S1 of the first pole piece 14 along the first direction Z. For details, see Table 2:

[0133]

[0134]

[0135] Table 2

[0136] According to the test results in Table 2, setting 30%≤S2 / S1≤80% can not only further alleviate the delamination problem of the stacked core 1 during battery drop, but also avoid the breakage of the first electrode sheet 14 and the wrinkling or deformation of the electrode sheets in the stacked core 1.

[0137] The difference between Examples 3-1 to 3-11 and Example 1-1 is that special settings are made for the tightness T of the adhesive tape 4 and the difference d between the thickness of the stacked core 1 when the battery is at 100% SOC and 0% SOC. See Table 3 for details:

[0138]

[0139] Table 3

[0140] According to the test results in Table 3, by making the tightness of the adhesive tape 4 satisfy 1.0≤T≤1.2, the uniformity of stress transmission inside the stacked core 1 can be ensured, thereby further alleviating the problem of easy delamination of the stacked core 1 when the battery falls.

[0141] Combining the test results of Examples 3-8 to 3-11, it can be seen that making T satisfy 5d≥T≥1.1d can further improve the problem of delamination of the stacked core 1 during the battery drop process. If T is less than 1.1d, it is easy to cause the problem of the electrode cutting the adhesive tape 4.

[0142] The difference between Examples 4-1 to 4-10 and Example 1-1 is that the negative electrode active material layer 112 of the negative electrode sheet 11 is specially configured. In particular, in Example 4-6, the laser scribing step is omitted in the second step of preparing the lithium-ion battery. See Table 4 for details:

[0143]

[0144]

[0145] Table 4

[0146] The test results in Table 4 show that providing the recess 113 on the negative electrode sheet 11 can effectively alleviate the problem of attenuation of the bonding strength between the negative electrode sheet 11 and the separator 13 during the cyclic expansion process of the negative electrode sheet 11, and M being between 6% and 60% can better ensure the effect of alleviating the attenuation of the bonding strength between the negative electrode sheet 11 and the separator 13.

[0147] Combined with the test results of Examples 4-5, 4-9 and 4-10, it can be seen that controlling M / F1≤0.05 can further improve the problem of weakened adhesion between the negative electrode sheet 11 and the separator 13 after cycling.

[0148] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery, characterized in that: include: A stacked core (1) comprises a plurality of negative electrode sheets (11), a plurality of positive electrode sheets (12) and a plurality of separators (13) stacked along a first direction (Z); along the first direction (Z), the negative electrode sheets (11) and the positive electrode sheets (12) are alternately arranged; along the first direction (Z), the projected area of ​​the negative electrode sheets (11) is larger than the projected area of ​​the positive electrode sheets (12); the separator (13) is arranged between adjacent negative electrode sheets (11) and positive electrode sheets (12), and two opposite surfaces of the separator (13) along the first direction (Z) are respectively bonded to the negative electrode sheets (11) and the positive electrode sheets (12); A shell (2) is coated on the outside of the stacked core body (1); the shell (2) is bonded to the stacked core body (1) along at least one side of the first direction (Z); The bonding force between the diaphragm (13) and the negative electrode sheet (11) is F1 N / m, the bonding force between the diaphragm (13) and the positive electrode sheet (12) is F2 N / m, and the bonding force between the shell (2) and the stacked core (1) is F3 N / m; wherein F3>F1>F2.

2. The battery according to claim 1, characterized in that 1.2≤F3 / F1≤4.0; Preferably, 2.0≤F3 / F1≤3.

0.

3. The battery according to claim 1, characterized in that 0.3≤F2 / F1≤0.8; Preferably, 0.5≤F2 / F1≤0.

7.

4. The battery according to any one of claims 1 to 3, characterized in that The diaphragm (13) comprises a base film, a heat-resistant layer and two adhesive layers; along the first direction (Z), the heat-resistant layer is arranged on one side of the base film; and along the first direction (Z), one of the two adhesive layers is arranged on a side of the base film away from the heat-resistant layer, and the other is arranged on a side of the heat-resistant layer away from the base film; Preferably, the bonding layer comprises polymer particles; preferably, the polymer particles comprise a first polymer, wherein the first polymer comprises a polymer formed by copolymerization of at least one monomer selected from the group consisting of methyl methacrylate, ethyl methacrylate, isooctyl acrylate, n-propyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate, styrene, butadiene, methacrylamide, acrylamide, acrylonitrile, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, and hexafluoropropylene; Preferably, the average particle size of the primary particles of the polymer particles is 0.2 μm to 1 μm.

5. The battery according to any one of claims 1 to 3, characterized in that The battery includes a bonding member (3); The shell (2) and the stacked core (1) are bonded together along at least one side of the first direction (Z) via the bonding member (3); The stacked core (1) comprises a first pole piece (14) bonded to the adhesive member (3), wherein the projection area of ​​the first pole piece (14) along the first direction (Z) is S1 mm 2 The projected area of ​​the adhesive member (3) along the first direction (Z) is S2 mm 2 ; 30%≤S2 / S1≤80%; Preferably, 40%≤S2 / S1≤70%; Preferably, along the first direction (Z), the bonding members (3) are provided on both sides of the stacked core body (1).

6. The battery according to any one of claims 1 to 3, characterized in that The battery comprises adhesive tape (4), and the adhesive tape (4) is arranged on the edge of the stacked core body (1); The stacked core (1) has a first surface (1a) and a second surface (1b) that are arranged opposite to each other, and a side surface (1c) connected between the first surface (1a) and the second surface (1b); along the width direction (R) of the adhesive tape, the adhesive tape (4) sequentially covers at least a portion of the structure of the first surface (1a), the side surface (1c), and the second surface (1b); Along the width direction (R) of the adhesive tape, the size of the adhesive tape (4) is c mm, the size of the portion of the adhesive tape (4) covering the first surface (1a) is a mm, and the size of the portion of the adhesive tape (4) covering the second surface (1b) is b mm; along the first direction (Z), when the battery is in a 0% SOC state, the vertical distance between the first surface (1a) and the second surface (1b) is t mm; Where, T = (cab) / t, 1.0≤T≤1.2; Preferably, 1.02≤T≤1.

1.

7. The battery according to any one of claims 1 to 3, characterized in that The negative electrode sheet (11) comprises a negative electrode current collector (111) and a negative electrode active material layer (112) arranged on at least one surface of the negative electrode current collector (111); The negative electrode active material layer (112) is bonded to the separator (13); a plurality of recesses (113) are spaced apart on the negative electrode active material layer (112), and the sum of the projected areas of the plurality of recesses (113) along the first direction (Z) is S3 mm 2 The projected area of ​​the negative electrode active material layer (112) along the first direction (Z) is S4 mm 2 ; Among them, M=S3 / S4, 6%≤M≤60%.

8. The battery according to claim 7, characterized in that The recess (113) is a groove, and a plurality of the grooves are spaced apart along the second direction; The depth of the groove is 5 μm-60 μm; and / or, The width of the groove is 30 μm-180 μm; and / or, Along the second direction, the distance between two adjacent grooves is 0.5mm-10mm; The second direction is perpendicular to the first direction (Z).

9. The battery according to claim 7, characterized in that M / F1≤0.

05.

10. An electrical device, characterized in that: include: The battery according to any one of claims 1 to 9.

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