Battery and electric device

Abstract

The invention discloses a battery and an electric device. The battery comprises an outer package, an electrode assembly and electrolyte, the electrode assembly comprises an isolating membrane and a plurality of pole pieces, the pole pieces and the isolating membrane are wound for multiple circles to form an electrode main body, and the electrode main body comprises a straight part and corner parts arranged at the two opposite ends of the straight part; the pole piece is provided with a plurality of first convex parts arranged corresponding to the corner parts, the height of the first convex parts is Hm (mu m) along the thickness direction of the pole piece, and Hm is more than or equal to 20 and less than or equal to 80; the electrolyte comprises lithium difluorophosphate, based on the total weight of the electrolyte, the weight percentage of the lithium difluorophosphate is E (%), and E is more than or equal to 0.01 and less than or equal to 3.00. According to the invention, the content E of the lithium difluorophosphate is matched with the height Hm of the first convex part, so that a solid electrolyte interface film formed by the lithium difluorophosphate on a pole piece interface, especially the first convex part, has a good improvement effect on the circulation of lithium ions on the basis of meeting the improvement of the electrolyte infiltration effect; and the 1s direct-current impedance of the battery at 20% SOC can be further reduced.

Description

[0001] This application is a divisional application of the patent application filed on March 18, 2025, with application number 202510319242.5 and invention title "A Battery and an Electric Device". Technical Field

[0002] This application relates to the field of battery technology, and more particularly to a battery and an electrical device. Background Technology

[0003] Currently, a significant portion of secondary battery electrode assemblies employ a wound structure. For wound electrode assemblies, hot pressing is required after winding, and the electrode assembly is fixed after being placed in the outer packaging. Under these circumstances, electrolyte cannot easily penetrate the interior of the wound electrode assembly, which can easily lead to abnormalities such as insufficient electrolyte or poor electrolyte wetting. Ultimately, this can cause deterioration of the electrode interface, affecting battery cycle performance and even causing lithium plating, thus compromising battery safety. Summary of the Invention

[0004] The inventors discovered that there is compression between the layers of the electrode assembly, which leads to insufficient electrolyte between the layers, poor wetting, and easy interface deterioration.

[0005] This application provides a battery and an electrical device that can improve the problem of poor electrolyte wetting.

[0006] In a first aspect, embodiments of this application provide a battery, including an outer packaging, an electrode assembly, and an electrolyte, wherein the electrode assembly is disposed in the internal space of the outer packaging, and the electrolyte fills the internal space of the outer packaging; The electrode assembly includes a separator and multiple electrode sheets. The separator is disposed between two electrode sheets with opposite polarities, and the electrode sheets and the separator are wound multiple times to form an electrode body. The electrode body includes a straight portion and corner portions disposed at opposite ends of the straight portion. The corner portions of the electrode sheets are provided with multiple first protrusions. Along the thickness direction of the electrode sheet, the height of the first protrusion is Hm, in μm, and Hm satisfies: 20≤Hm≤80. The electrolyte includes lithium difluorophosphate. Based on the total weight of the electrolyte, the weight percentage of lithium difluorophosphate is E, expressed as %, and E satisfies: 0.01 ≤ E ≤ 3.00.

[0007] Based on the above embodiments, the content E of lithium difluorophosphate is matched with the height Hm of the first protrusion, so that the solid electrolyte interface film formed by lithium difluorophosphate at the electrode interface has a good effect on improving the flow of lithium ions at the first protrusion, thereby improving the electrode interface problem and reducing the DC resistance value of the battery at 20% capacity.

[0008] In some embodiments, the battery satisfies: 0.01≤E≤1.8, 20≤Hm≤40.

[0009] In some embodiments, the electrolyte further includes ethylene glycol bis(2-cyanoethyl) ether, and the weight percentage of ethylene glycol bis(2-cyanoethyl) ether is F based on the total weight of the electrolyte, in % , where F satisfies: 0.1 ≤ F ≤ 2.5.

[0010] Based on the above embodiments, ethylene glycol bis(2-cyanoethyl) ether can assist lithium difluorophosphate in forming a stable solid electrolyte interface film at the positive electrode interface, improving the problem of uneven solid electrolyte interface film formation caused by the presence of protrusions. Furthermore, the solid electrolyte interface film can also suppress the occurrence of side reactions at the electrode interface at low temperatures, improve the low-temperature discharge performance and intermittent cycle performance of the battery, and reduce the amount of gas generated during long-term battery cycles.

[0011] In some embodiments, the battery satisfies: 0.1≤F≤1.8, 20≤Hm≤60.

[0012] In some embodiments, the battery satisfies: 0.3≤F≤1.2, 20≤Hm≤40.

[0013] In some embodiments, the viscosity of the electrolyte is A, in mPa·s, and the battery satisfies: 4.0 ≤ A ≤ 7.0.

[0014] Based on the above embodiments, by matching the viscosity A of the electrolyte with the height of the first protrusion, a suitable distance is made between the electrode and the separator, which helps to improve the wetting rate of the electrolyte and facilitates the selection of the lithium difluorophosphate content within a suitable range, so that lithium difluorophosphate forms a solid electrolyte interface film of suitable thickness at the positive electrode interface.

[0015] In some embodiments, the battery satisfies: 5≤A≤6.5, 20≤Hm≤40.

[0016] In some embodiments, the electrolyte further includes a lithium salt selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, and tetraethylammonium tetrafluoroborate.

[0017] In some embodiments, the electrolyte further includes a lithium salt, including lithium difluorooxalate borate, wherein the weight percentage of lithium difluorooxalate borate is K based on the total weight of the electrolyte, in % and K satisfies: 3.0 ≤ K ≤ 10.0.

[0018] Based on the above embodiments, by adding lithium difluorooxalate borate to the electrolyte, lithium difluorooxalate borate can suppress gas production and improve the performance of the hot box. At the same time, it has good high voltage stability and a wide operating temperature range. It also has low ion migration resistance at -20°C. By selecting the height Hm of the first protrusion, the wetting effect of the electrolyte into the active material layer can be improved. Furthermore, by selecting the weight percentage K of lithium difluorooxalate borate in the range of 3.0 ≤ K ≤ 10.0, the application of lithium difluorooxalate borate in electrolytes can be promoted.

[0019] In some embodiments, the battery satisfies: 3.0≤K≤8.0, 20≤Hm≤60.

[0020] In some embodiments, the electrode has a plurality of second protrusions disposed corresponding to the flat portion, and the height of the second protrusion is Hn (in μm) along the thickness direction of the electrode; the diameter of the inner surface of the first protrusion is Rm (in mm), and the diameter of the inner surface of the second protrusion is Rn (in mm); the battery satisfies at least one of the following conditions: (1) 5 ≤ Hn ≤ 40; (2) 1.25≤Hm / Hn≤5; (3) 0.3≤Rm≤10; (4) Rm = Rn.

[0021] In some embodiments, the electrode includes a current collector and an active material layer disposed on the surface of the current collector. The active material layer includes carbon nanotubes with a length of L in μm, where L satisfies: 0.2 ≤ L ≤ 5.

[0022] Based on the above embodiments, the carbon nanotubes have a suitable length, which makes the active material layer at the first and second protrusions have good morphological stability and is not prone to abnormalities such as cracks and shedding. It also improves the electronic conductivity of the electrode and the effect of floating charging of the battery at 45°C.

[0023] In some embodiments, the diameter of the carbon nanotube is D1, in nm, and D1 satisfies: 5≤D1≤18.

[0024] Based on the above embodiments, the appropriate diameter D1 of the carbon nanotubes has the effect of reducing interfacial side reactions in the electrode, improving cycle life, and improving the performance of the battery thermal chamber.

[0025] Secondly, embodiments of this application provide an electrical device, which includes a housing and a battery as described above, wherein the battery is disposed in the internal space of the housing.

[0026] Based on the battery and power device embodiments of this application, by adding lithium difluorophosphate to the electrolyte and selecting a weight percentage E of lithium difluorophosphate that satisfies 0.01 ≤ E ≤ 3.00, lithium difluorophosphate can improve the ion flow in the lithium salt. Simultaneously, it uniformly forms a thin solid electrolyte interface film on the surface of the positive electrode active material layer, capturing gas molecules at the electrolyte-electrode interface and reducing interfacial side reactions, thereby improving the battery's fast-charging performance and charge-discharge cycle performance. Furthermore, by matching the lithium difluorophosphate content E with the height Hm of the first protrusion, while improving the electrolyte wetting effect, the solid electrolyte interface film, especially at the first protrusion, effectively improves the flow of lithium ions, thus mitigating the 1s DC resistance of the battery at 20% SOC. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a front view schematic diagram of the electrode sheet in the unfolded state according to an embodiment of this application; Figure 2 This is a cross-sectional view of an electrode assembly according to an embodiment of this application; Figure 3 This is a partial cross-sectional view of an embodiment of the present application showing a electrode sheet with a protrusion. Figure 4 This is a front view schematic diagram of an embodiment of the present application showing an electrode sheet having an end clearance area.

[0029] Figure label: 20. Electrode body; 21. Straight section; 22. Corner section; 50. Separating membrane; 300, pole piece; 311, convex portion; 301, first convex portion; 410. Positive electrode plate; 420. Negative electrode plate; 330. End clearance zone; 331. Head clearance zone; 332. Tail clearance zone; 341. Edge clearance zone; X: length direction; Y: width direction; Z: thickness direction. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] The inventors discovered that the electrode assembly inside the secondary battery adopts a wound structure, which requires hot pressing of the electrode assembly after the electrode sheets and separator are alternately stacked and wound. There is internal stress inside the electrode assembly, resulting in poor electrolyte wettability. Furthermore, the electrode assembly expands during charging and discharging, which further exacerbates the interlayer compression of the electrode assembly, leading to insufficient electrolyte, poor wetting, and ultimately, interface deterioration at weak points, and even lithium plating. To solve the above problems, gaps need to be created between battery layers. Currently, there are the following methods for creating gaps: (1) Applying adhesive paper to specific positions on the electrode to form gaps. This method currently improves the wetting ability, but the presence of adhesive paper occupies thickness, increasing the thickness of the electrode assembly and causing a certain loss in the energy density of the battery; (2) Applying soluble chemical substances to form gaps by uniformly applying some adhesive that is soluble in electrolyte to the electrode, but the improvement effect is limited and there are other side effects on battery performance; (3) Thickening the separator membrane. The separator membrane has a stronger ability to store electrolyte and improves the wetting effect of electrolyte, but this method will thicken the battery and greatly reduce the energy density.

[0032] The inventors also discovered that by machining protrusions on the electrode sheets, which provide support during winding, gaps are formed between the electrode layers of the electrode assembly, thereby improving the electrolyte transport capacity within the electrode assembly and enhancing the battery's cycle performance. Based on this, embodiments of this application provide a battery and electrical device that design the protrusions on the electrode sheets and the electrolyte to effectively improve poor electrolyte wetting and electrode interface problems.

[0033] The battery provided in this application includes an outer packaging and an electrode assembly disposed within the inner space of the outer packaging, as well as an electrolyte filling the inner space of the outer packaging. The electrode assembly includes two electrodes of opposite polarity and a separator, such as... Figure 1 The diagram shown is a front view of an embodiment of the electrode 300 in its unfolded state. The electrode 300 has two perpendicular length directions (X), width directions (Y), and thickness directions (Z). The length directions (X), width directions (Y), and thickness directions (Z) are aligned for two electrodes 300 with opposite polarities in the electrode assembly. Figure 2As shown, the separator 50 is disposed in the thickness direction Z of the electrode 300 between two electrodes 300 with opposite polarities. One of the two electrodes 300 with opposite polarities is a positive electrode 410 and the other is a negative electrode 420. The separator 50 has insulating properties to separate the positive electrode 410 and the negative electrode 420 to prevent the positive electrode 410 and the negative electrode 420 from being short-circuited.

[0034] like Figure 2 As shown, the separator 50 and two electrode sheets 300 are wound multiple times along the length direction X of the electrode sheets 300 to form the electrode body 20. The length direction X of the electrode sheets 300 is the direction in which the electrode sheets 300 are wound. The electrode body 20 is flat and includes a straight portion 201 and two corner portions 202. The two corner portions 202 are respectively disposed at opposite ends of the straight portion 201. Specifically, each turn of the electrode sheet 300 of the electrode body 20 includes two straight sections 21 and two corner sections 22. The two straight sections 21 are arranged side by side in a direction perpendicular to the surface of the straight section 21, and the two corner sections 22 are arranged opposite each other in a direction along the surface of the straight section 21. That is, the two straight sections 21 and the two corner sections 22 are connected end to end. The electrode body 20 has a terminal end, which is formed by a portion of the straight section 21 of the outermost electrode sheet 300. All the straight sections 21, the end points, and the isolation membrane 50 sandwiched between two adjacent straight sections 21 are stacked in a direction perpendicular to the surface of the straight section 21 to form a straight portion 201; all the corner sections 22 located on the same side of the straight section 21 in a direction parallel to the surface of the straight section 21 and the isolation membrane 50 sandwiched between two adjacent corner sections 22 together form a corner portion 202.

[0035] At least one of the positive electrode 410 and the negative electrode 420 has a protrusion 311. Specifically, the electrode 300 includes a current collector and an active material layer, with the active material layer and the current collector stacked along the thickness direction Z of the electrode 300, and the active material layer disposed on the surface of the current collector. The protrusion 311 is formed by a portion of the current collector and a portion of the active material layer protruding along the thickness direction Z of the electrode 300 towards the same side of the electrode 300. The electrolyte, as a channel for ion transport, enters the battery through the electrolyte injection process and continuously wets the interior of the battery driven by gravity and capillary forces. In this embodiment, the protrusion 311 provides support for the separator 50, creating a gap between the separator 50 and the electrode 300, thereby improving the electrolyte wetting effect.

[0036] Electrolytes typically comprise multiple components, primarily falling into three categories: lithium salts, non-aqueous organic solvents, and additives. These components influence the electrolyte's viscosity, ionic conductivity, and density, thereby affecting its ion transport performance. In this embodiment, by combining the electrolyte components with the protrusions 311 of the electrode 300, the electrolyte wetting process can be accelerated and the wetting effect improved, enhancing the electrolyte's ion transport capability. This, in turn, improves the battery's high-current cycle performance, enhances battery kinetics, and reduces the battery's DC impedance.

[0037] The electrode 300 has a plurality of first protrusions 301 provided corresponding to the corner portion 202, such as Figure 3 As shown, along the thickness direction Z of the electrode 300, the height of the first protrusion 301 is Hm, in μm, and Hm satisfies: 20 ≤ Hm ≤ 80. For example, Hm can be 20, 25, 34, 54, 66, 70, 80, or any range of the above. Since the corner portion 202 is a high-risk area for compression between the layers of the electrode body 20, by providing the corner portion 202 with the first protrusion 301, stable support can be provided for the separator 50 of the corner portion 202, thereby improving the wetting effect of the electrolyte in the corner portion 202. The electrolyte also includes lithium difluorophosphate. Based on the total weight of the electrolyte, the weight percentage of lithium difluorophosphate is E, in %. E satisfies: 0.01 ≤ E ≤ 3.00. For example, E can be 0.01, 0.10, 0.15, 2.11, 2.45, 2.68, 3.00, or any range of the above. By selecting a lithium difluorophosphate (LiPF6) weight percentage E in the electrolyte within the aforementioned range, LiPF6 can improve the ion flow in the lithium salt. Simultaneously, it uniformly forms a thin solid electrolyte interface film on the surface of the positive electrode active material layer, capturing gas molecules at the interface between the electrolyte and electrode 300, reducing interfacial side reactions, and thus improving the battery's charge-discharge cycle performance. Furthermore, since the first protrusion 301 is easily damaged by compression, the resulting solid electrolyte interface film is relatively thin. Matching the LiPF6 content E with the height Hm of the first protrusion allows the solid electrolyte interface film, especially at the first protrusion 301, to effectively improve lithium ion flow, mitigating the 1s DC impedance of the battery at 20% SOC (State of Charge). However, when Hm is below 20 μm or above 80 μm, the improvement in battery cycle performance by LiPF6 combined with the first protrusion 301 is limited. When the weight percentage E of LiPF6 exceeds 3.00%, problems such as high electrolyte viscosity and lithium ion enrichment at the electrode 300 interface also arise.

[0038] Preferably, the battery satisfies: 0.01≤E≤1.8, 20≤Hm≤40. When the content E of lithium difluorophosphate is combined with the height Hm of the first protrusion 301, the electrolyte can have a more suitable viscosity and ion transport capacity, so as to better improve the electrolyte wetting effect and improve the fast charging performance of the battery.

[0039] In some embodiments, the electrolyte further includes ethylene glycol bis(2-cyanoethyl) ether. The weight percentage of ethylene glycol bis(2-cyanoethyl) ether is F, expressed as %, based on the total weight of the electrolyte. F satisfies the following condition: 0.1 ≤ F ≤ 2.5. For example, F can be 0.10, 0.15, 0.58, 1.22, 1.68, 2.23, 2.50, or any range thereof. By including ethylene glycol bis(2-cyanoethyl) ether in the electrolyte, it can assist lithium difluorophosphate in forming a stable solid electrolyte interface film at the interface of the positive electrode 410, improving the unevenness of the solid electrolyte interface film formation caused by the presence of the protrusion 311. Furthermore, the solid electrolyte interface film can suppress the occurrence of side reactions at the electrode 300 interface at low temperatures, improving the low-temperature discharge performance and intermittent cycle performance of the battery, while reducing gas production during long-cycle operation.

[0040] In some embodiments, the battery satisfies: 0.1 ≤ F ≤ 1.8, 20 ≤ Hm ≤ 60. By selecting the weight percentage F of ethylene glycol bis(2-cyanoethyl) ether to match the height of the first protrusion 301, when the first protrusion 301 of the corner portion 202 has a higher height, ethylene glycol bis(2-cyanoethyl) ether can effectively improve the stability of the solid electrolyte interface film, as well as improve the low-temperature high-rate discharge performance and charge-discharge cycle performance of the battery. Preferably, the battery satisfies: 0.3 ≤ F ≤ 1.2, 20 ≤ Hm ≤ 40. Within this range, ethylene glycol bis(2-cyanoethyl) ether can better stabilize the problem of uneven solid electrolyte interface film caused by the presence of protrusion 311, and assist lithium difluorophosphate in forming a more stable solid electrolyte interface film at the interface of the positive electrode 410.

[0041] In some embodiments, the viscosity of the electrolyte is A, measured in mPa·s, and the battery satisfies: 4.0 ≤ A ≤ 7.0, 20 ≤ Hm ≤ 80. For example, A can be 4.0, 4.6, 5.0, 5.3, 6.8, 7.0, or any range thereof. By selecting the electrolyte viscosity A within the above range, and based on the electrolyte having a good wetting effect, it is convenient to select the lithium difluorophosphate content within a suitable range so that the lithium difluorophosphate forms a solid electrolyte interface film of suitable thickness at the interface of the positive electrode 410. By matching the electrolyte viscosity A with the height of the first protrusion 301, a suitable distance is achieved between the electrode 300 and the separator 50, which helps to improve the electrolyte wetting rate. Preferably, the battery satisfies: 5 ≤ A ≤ 6.5, 20 ≤ Hm ≤ 40.

[0042] In some embodiments, the lithium salt in the electrolyte is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, and lithium tetrafluoroborate.

[0043] The presence of lithium difluorooxalate borate can inhibit the high-temperature decomposition of lithium salts and suppress gas production, thus improving the performance of the thermal chamber. It also exhibits good high-voltage stability and a wide operating temperature range, with low ion migration resistance at -20°C. However, due to its low solubility in electrolytes, lithium difluorooxalate borate tends to have poor wetting effects, hindering its mainstream application in electrolytes. In this embodiment, a protrusion 311 is provided on the electrode 300 to create a suitable gap between the electrode 300 and the separator 50, improving the wetting effect of the electrolyte into the active material layer and promoting the application of lithium difluorooxalate borate in electrolytes. When the lithium salt includes lithium difluorooxalate borate, the weight percentage of lithium difluorooxalate borate, K, is % based on the total weight of the electrolyte. K satisfies the following condition: 3.0 ≤ K ≤ 10.0. For example, K can be 3.00, 3.55, 3.69, 5.22, 6.68, 8.89, 10.00, or any range thereof. By selecting lithium difluorooxalate borate within the above range, the electrolyte can have a good wetting effect. Preferably, the battery satisfies: 3.0 ≤ K ≤ 9.0, 20 ≤ Hm ≤ 60, ensuring that lithium difluorooxalate borate can be fully dissolved in the electrolyte and that the electrolyte has a suitable wetting effect.

[0044] In some embodiments, the electrode 300 has a plurality of second protrusions 302 corresponding to the flat portion 201. Along the thickness direction of the electrode 300, the height of the second protrusion 302 is Hn, in μm, and Hn satisfies: 5 ≤ Hn ≤ 40. For example, Hn can be 5, 10, 15, 25, 35, 40, or any range thereof. By selecting the height of the second protrusion 302 within the above range, the second protrusion 302 provides good support for the flat portion 201 of the electrode body 20. Furthermore, the height Hm of the first protrusion 301 and the height Hn of the second protrusion 302 satisfy: 1.5 ≤ Hm / Hn ≤ 5. This ensures a suitable ratio between the height Hm of the first protrusion 301 and the height Hn of the second protrusion 302, providing better support for the flat portion 201 and the corner portion 202 of the electrode body 20, and improving the wetting effect of the electrolyte.

[0045] In some embodiments, the diameter of the inner surface of the first protrusion 301 is Rm, in mm, and Rm satisfies: 0.3 ≤ Rm ≤ 10. For example, Rm can be 0.3, 10, 15, 25, 35, 40, or any range thereof. By selecting a range where the diameter Rm of the inner surface of the first protrusion 301 satisfies the above condition, it is easier to match the height of the first protrusion 301, so that the first protrusion 301 of the electrode 300 has a suitable elongation and a suitable sharpness, giving the first protrusion 301 good support stability, which helps to form a uniform solid electrolyte interface film at the first protrusion 301. In some embodiments, the diameter of the inner surface of the second protrusion 302 is Rn, in mm, and Rm = Rn. Similarly, this helps to form a uniform solid electrolyte interface film at the second protrusion 302. If the first protrusion 301 or the second protrusion 302 is irregular in shape, an equivalent diameter, i.e., the distance between the two farthest points, is used.

[0046] In this embodiment of the application, when the electrode 300 has a first protrusion 301 and a second protrusion 302, optionally, all protrusions 311 of the same electrode 300 are arranged to protrude on the same side of the electrode 300 in the thickness direction Z of the electrode 300. For example, the first protrusion 301 provided in the straight section 21 and the second protrusion 302 provided in the corner section 22 both protrude toward the side of the winding center of the electrode body 20; or, the first protrusion 301 provided in the straight section 21 and the second protrusion 302 provided in the corner section 22 both protrude toward the side away from the winding center of the electrode body 20. Optionally, a portion of the protrusions 311 of the same electrode 300 protrude toward one side of the electrode 300 in the thickness direction Z, and another portion of the protrusions 311 protrude toward the other side of the electrode 300 in the thickness direction Z. For example, the first protrusion 301 provided on the straight section 21 protrudes toward the side facing the winding center of the electrode body 20, and the second protrusion 302 provided on the corner section 22 protrudes toward the side away from the winding center of the electrode body 20; or, the first protrusion 301 provided on the straight section 21 protrudes toward the side away from the winding center of the electrode body 20, and the second protrusion 302 provided on the corner section 22 protrudes toward the side facing the winding center of the electrode body 20.

[0047] The above is merely an illustrative description. This application does not limit the orientation of the protrusions 311 of each electrode 300, and the orientation can be selected according to actual needs.

[0048] In some embodiments, the active material layer of the electrode 300 includes a conductive agent, which includes carbon nanotubes. The length of the carbon nanotubes is L, in μm, and L satisfies: 0.2 ≤ L ≤ 5. For example, L can be 0.3, 10, 15, 25, 35, 40, or any range thereof. By including carbon nanotubes in the active material layer, the high-temperature impedance of the electrode 300 and the high-temperature charge / discharge rate performance of the battery can be improved. The appropriate length of the carbon nanotubes within the aforementioned range ensures good morphological stability of the active material layer at the first protrusion 301 and the second protrusion 302, reducing the likelihood of cracks, shedding, or other abnormalities. Furthermore, it improves the electronic conductivity of the electrode and enhances the battery's float charging performance at 45°C.

[0049] In some embodiments, the diameter of the carbon nanotubes is D1, in nm, and D1 satisfies: 5 ≤ D1 ≤ 18. For example, D1 can be 5, 6, 8, 10, 12, 15, 18, or any range thereof. By selecting the diameter D1 of the carbon nanotubes within the above range, it is effective in reducing interfacial side reactions in the electrode, improving cycle life, and improving the performance of the battery thermal chamber.

[0050] In some embodiments, the surface of the active material layer facing away from the current collector forms a first surface. A protrusion 311 is disposed on a protrusion region of the first surface, the protrusion region being defined by a protrusion boundary line. The protrusion 311 in the protrusion region may be located within the area defined by the protrusion boundary line, or it may be internally connected to the protrusion boundary line. The first surface also includes an end clearance region 330 and an edge clearance region 341. The end clearance region 330 is connected to the end of the protrusion region in the length direction X of the electrode 300 and extends to the edge of the electrode 300. The edge clearance region 341 is disposed on one side of the protrusion region in the width direction Y of the electrode 300 and extends to the edge of the electrode 300. Neither the edge clearance region 341 nor the end clearance region 330 has a protrusion 311. After the two electrodes 300 and the separator 50 are wound together, the surfaces of the electrodes 300 corresponding to the edge clearance regions 341 and 330 can be spaced apart from the separator 50. The end clearance area 330 includes a head clearance area 331 and a tail clearance area 332. In the electrode body 20, the head clearance area 331 of the electrode 300 is located in the innermost layer, and the tail clearance area 332 of the electrode 300 is located in the outermost layer.

[0051] In this embodiment, the current collector of the negative electrode 420 is a negative electrode current collector, and the active material layer is a negative electrode active material layer; the current collector of the positive electrode 410 is a positive electrode current collector, and the active material layer is a positive electrode active material layer. This embodiment does not impose any particular limitations on the materials used for the positive electrode active material, positive electrode current collector, negative electrode active material, and negative electrode current collector. Various materials known in the art that can be used as positive electrode active materials, positive electrode current collectors, negative electrode active materials, and negative electrode current collectors are applicable to this application.

[0052] Exemplarily, the negative electrode current collector can be at least one of copper foil, aluminum foil, nickel foil, or carbon-based current collector; the thickness of the negative electrode current collector can be from 1 μm to 200 μm. The negative electrode active material layer can be disposed on one or both opposing surfaces of the negative electrode current collector. Further, in the thickness direction Z of the negative electrode sheet 420, the negative electrode active material layer can be coated only on a portion of the negative electrode current collector. Exemplarily, the thickness of the negative electrode active material layer can be from 10 μm to 500 μm.

[0053] Exemplarily, the negative electrode active material layer includes a negative electrode active material, which includes at least one of lithium metal, natural graphite, artificial graphite, or silicon-based materials. The silicon-based material includes at least one of silicon, silicon oxide, silicon carbide, or silicon alloy. The negative electrode active material layer may also include a conductive agent. Exemplarily, the conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, Ketjen black, sheet graphite, graphene, carbon fiber, or carbon nanowire, in addition to carbon nanotubes. The negative electrode active material layer may also include a binder, which may include at least one of carboxymethyl cellulose (CMC), polyacrylate, polyacrylate, polyvinylpyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0054] For example, the positive current collector can be aluminum foil, or other positive current collectors commonly used in the art can be used. The thickness of the positive current collector can be from 1 μm to 200 μm. The positive active material layer can be disposed on one or both opposite surfaces of the positive current collector. Furthermore, in the thickness direction Z of the positive electrode 410, the positive active material layer can be coated only on a portion of the positive current collector, and the thickness of the positive active material layer can be from 10 μm to 500 μm.

[0055] For example, the positive electrode active material includes LiCoO2, LiNiO2, LiMn2O4, and LiCo. 1-y M y O2, LiNi 1-y M y O2, LiMn 2-y M y O4, LiNi x Co y Mn z M 1-x-y-z O2, wherein M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1. The positive electrode active material layer also includes a conductive agent. Exemplarily, the conductive agent in the positive electrode active material layer may include, in addition to carbon nanotubes, at least one of conductive carbon black, acetylene black, Ketjen black, sheet graphite, graphene, or carbon fiber. The positive electrode active material layer may also include a binder, which may include at least one of vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0056] This application does not impose any particular limitation on the separator 50, and various materials known in the art that can be used as the separator 50 are applicable to this application. Exemplarily, the separator 50 includes at least one selected from polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Polyethylene and polypropylene, in particular, have good short-circuit prevention properties and can improve the stability of the electrode assembly through a turn-off effect. The thickness of the separator 50 is in the range of about 3 μm to 500 μm. The positive and negative tabs are made of a metallic conductive material.

[0057] In this embodiment, the battery further includes a positive electrode tab and a negative electrode tab. The positive electrode tab is disposed on the positive electrode plate 410, and the negative electrode tab is disposed on the negative electrode plate 420. In this embodiment, there are no special limitations on the positive electrode tab, the negative electrode tab, and the protective adhesive. Various materials known in the art that can be used as positive electrode tabs, negative electrode tabs, and protective adhesives are applicable to this application.

[0058] The electrolyte in this application embodiment also includes a non-aqueous organic solvent. This application embodiment does not particularly limit the non-aqueous organic solvent; various materials known in the art that can be used as non-aqueous organic solvents are applicable to this application. Exemplarily, the non-aqueous organic solvent may contain at least one of a carboxylic acid ester compound, an ether compound, or other organic solvent. The aforementioned carbonate compound may include, but is not limited to, at least one of a chain carbonate compound and a cyclic carbonate compound. The aforementioned chain carbonate compound may include, but is not limited to, at least one of dipropyl carbonate (DPC) or ethyl methyl carbonate (EMC). The aforementioned cyclic carbonate compound may include, but is not limited to, at least one of butyl carbonate (BC) or vinyl ethylene carbonate (VEC). The aforementioned carboxylic acid ester compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters. This application does not impose any particular limitation on the weight percentage of non-aqueous organic solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the total mass of the electrolyte, the weight percentage of non-aqueous organic solvents may be from 10% to 70%.

[0059] This application does not impose any particular restrictions on the packaging bag for the battery; it can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0060] This application does not impose any particular limitation on the type of battery, which may include any device in which an electrochemical reaction occurs. In this application, the battery may include, but is not limited to, lithium metal batteries, lithium-ion batteries, lithium polymer batteries, or lithium-ion polymer batteries.

[0061] The battery manufacturing process described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, it may include, but is not limited to, the following steps: after installing the positive electrode tab on the positive electrode plate 410 and the negative electrode tab on the negative electrode plate 420, the positive electrode plate 410, the separator 50 and the negative electrode plate 420 are stacked in sequence, and the electrode plate is wound, folded or otherwise operated as needed to obtain a wound electrode assembly. The electrode assembly is placed in a packaging bag, the electrolyte is injected into the packaging bag and sealed to obtain a battery; or, the positive electrode plate 410, the separator 50 and the negative electrode plate 420 are stacked in sequence, and the four corners of the entire stacked structure are fixed with tape to obtain a stacked electrode assembly. The electrode assembly is placed in a packaging bag, the electrolyte is injected into the packaging bag and sealed to obtain a battery.

[0062] The battery described in this application can be used in electrical devices. This application does not specifically limit the type of electrical device; it can be any electrical device known in the prior art. In some embodiments, the electrical device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0063] The present application will be further illustrated below using a lithium-ion battery as an example and with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0064] The performance of lithium-ion batteries in the embodiments and comparative examples of this application is tested using the following methods: (1) Test method for capacity retention during 25℃ / 45℃ 1.5C charging / 0.5C discharging cycles In an environment of 25℃ / 45℃, the lithium-ion battery was charged at a constant current of 1.5C to its full charge voltage (the maximum designed voltage of the lithium-ion battery is 4.53V). Then, it was charged at the maximum voltage at a constant voltage until the current reached 0.02C. Finally, it was discharged at a constant current of 0.5C until the final voltage reached 3.0V. The discharge capacity of the first cycle was recorded. The above steps were then repeated for charge and discharge cycles, and the discharge capacity of the lithium-ion battery in each charge and discharge cycle was recorded.

[0065] The cycle capacity retention rate at 25℃ / 45℃ with 1.5C charging and 0.5C discharging is calculated as (discharge capacity of the Nth cycle / discharge capacity of the first cycle) × 100%.

[0066] The number of charge-discharge cycles with a 25℃ / 45℃ 0.5C cycle capacity ≤ 80% is: the number of charge-discharge cycles when the cycle capacity retention rate is 80%.

[0067] (2) Test method for the height H of the protrusion 311 The electrode was measured using scanning electron microscopy (SEM). The electrode sample was placed in an SEM microscope, and high-resolution images of the protrusions were acquired by scanning with an electron beam. In the SEM image, image processing software was used to draw a measurement line along the height direction of the protrusion. Based on the image pixel information and the known magnification, the height of the protrusion was calculated. Similarly, the diameter of the protrusion was measured in the SEM image using image processing software. The height H of the protrusion was obtained by averaging the diameters of three adjacent protrusion locations.

[0068] It can also be obtained through the VR series shape profile measuring microscope.

[0069] (3) Electrolyte viscosity test method The electrolyte sample was placed in a beaker, and the viscosity of the electrolyte was tested at 25°C using a viscometer.

[0070] (4) Test procedure for the 20% SOC 1s DCR (Direct Current Resistance) value of a fresh battery A fully charged battery is left to rest for 1 hour, then discharged to the target 20% SOC using a 0.2C current. After resting for 1 minute, it is discharged at 1C for 1 second. During the 1 second of current application, the change in battery terminal voltage is recorded. The DC internal resistance of the battery is calculated using the formula R = ΔV / I, where ΔV is the voltage change in 1 second before and after current application, and I is the applied current. (5) Test scheme for discharge capacity retention rate (%) at -20℃ and 0.2C Five lithium-ion batteries were taken from each group and charged at 25°C. Constant current and constant voltage charging was performed at a charging current of 1C until the upper limit voltage was reached. The fully charged lithium-ion batteries were then left to stand at 25°C and -20°C for 1 hour respectively, followed by constant current discharge at a discharge current of 0.2C until the cutoff voltage was reached. The discharge capacity DR at 25°C and the discharge capacity DL at -20°C were obtained. The upper limit voltage for charging the lithium-ion batteries was 4.53V, and the discharge cutoff voltage was 3V.

[0071] Low-temperature capacity retention (%) = DL / DR × 100%.

[0072] A lower low-temperature capacity retention rate indicates a worse low-temperature charge-discharge performance of the lithium-ion battery; a higher low-temperature capacity retention rate indicates a better low-temperature charge-discharge performance of the lithium-ion battery.

[0073] (6) Gas production test plan The amount of gas released by the battery is measured using a gas analyzer or gas collection device. The operation method is as follows: ensure that the equipment is calibrated to improve the accuracy of the measurement, place the battery in the test container and start recording the initial gas amount, and use the charge-discharge cycle method in the 25℃ 1.5C charge / 0.5C discharge cycle capacity retention test method in test item (1) to charge and discharge 800 times, and then measure the amount of gas in the battery.

[0074] Battery gas production = Gas volume after test - Initial gas volume.

[0075] (7) Test scheme for 134℃ hot box pass rate (%, test 10ea) Ten lithium-ion batteries from each group were taken and charged in an environment of 25°C. Constant current and constant voltage charging was performed at a charging current of 1C until the upper voltage limit was reached. The fully charged lithium-ion batteries were then placed in a hot chamber. When the chamber temperature reached 134°C, the batteries were left to stand for 1 hour, during which time the battery voltage and equipment temperature data were recorded. If no fire occurred after 1 hour, the test was considered passed.

[0076] Pass rate (%) = Number of batteries that passed the test / 10 × 100%.

[0077] A higher pass rate indicates better battery thermal box performance.

[0078] (8) Test scheme for the longest time without gas production during float charging at 45℃ Maintain the test environment temperature at 45℃, which can be achieved using a temperature control chamber or environmental chamber. Connect the battery to the float power supply, ensuring correct connection and good contact. Start CV at 4.53V, record the start time, and monitor the battery voltage, current, temperature, and thickness daily. Observe the battery for any abnormal phenomena, such as overheating, leakage, or gas production.

[0079] Thickness expansion rate = (test thickness / initial thickness) * 100% - 1.

[0080] Record the dates on which significant gas production is observed and the thickness expansion rate is >10%, in days.

[0081] (9) Test scheme for electrode electronic conductivity Using a four-probe tester or other suitable conductivity testing equipment, the procedure is as follows: calibrate the equipment to ensure measurement accuracy, and ensure the ambient temperature and humidity are between 20℃ and 25℃. Place the sample on the testing equipment, ensuring good contact between the probe and the sample surface. Apply a known current and calculate the conductivity by measuring the voltage drop. For the four-probe method, conductivity can be calculated using the following formula: σ = I / V * t / W, where σ is the electronic conductivity, I is the current, V is the voltage drop, t is the sample thickness, and W is the sample width.

[0082] (10) Test scheme for K value After the battery production is completed, the open circuit voltage OCV1 of the battery is measured first using an open circuit voltage tester. After an interval of 48 hours, the open circuit voltage OCV2 of the battery is measured again. The K value is (OCV1-OCV2)mv / 48h.

[0083] The K value can characterize the self-discharge performance of a battery. The larger the K value, the faster the battery loses power, meaning the battery's charge decreases quickly when it is at rest. The smaller the K value, the slower the battery loses power and the better its stability, meaning the battery's charge decreases slowly when it is at rest.

[0084] (11) Electrolyte composition measurement The tests were performed using GC-MS combined with the internal standard method.

[0085] Example 1-1 (1) Preparation of positive electrode 410 The positive electrode active material is LiCoO2, the positive electrode conductive agent is conductive carbon black (Super P), and the positive electrode binder is polyvinylidene fluoride (PVDF, Mw=7×10). 6The materials were mixed at a mass ratio of 97.5:1:1.5, with N-methylpyrrolidone (NMP) added as a solvent. The mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil current collector. After drying at 85°C and cold pressing, a positive electrode sheet 410 with a single-sided coating of 50 μm thick positive active material layer was obtained. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet 410 with a double-sided coating of positive active material layer. The sheet was then cut to a size of 74 mm × 851 mm for later use. The compaction density of the positive active material layer was 4.23 g / cm³. 3 .

[0086] (2) Preparation of negative electrode 420 Artificial graphite as the negative electrode active material, conductive carbon black (Super P) as the negative electrode conductive agent, and carboxymethyl cellulose (CMC-Na, Mw=7×10) as the thickener are used. 5 ), negative electrode binder styrene-butadiene rubber (SBR, Mw = 5 × 10), 6 The materials were mixed at a mass ratio of 97.5:1:0.5:1, and then deionized water was added as a solvent. The mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 50 wt%. The negative electrode slurry was uniformly coated onto one surface of an 8 μm thick copper foil current collector. It was then dried at 85°C and cold-pressed to obtain a negative electrode sheet 420 with a single-sided coating of 60 μm thick negative electrode active material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet 420 with a double-sided coating of negative electrode active material layer. The sheet was then cut to a size of 76 mm × 867 mm for later use. The compaction density of the negative electrode active material layer was 1.77 g / cm³. 3 .

[0087] (3) Preparation of the separating membrane 50 A 5μm thick polyethylene (PE) porous membrane was used.

[0088] (4) Preparation of electrolyte In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) are mixed in a mass ratio of 1:1:2 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6), lithium difluorophosphate, and ethylene glycol bis(2-cyanoethyl) ether are dissolved in the above base solvent to obtain an electrolyte.

[0089] Based on the total mass of the electrolyte, the weight percentage of LiPF6 (K) is 8.0%, the weight percentage of lithium difluorophosphate (E) is 0.01%, the weight percentage of ethylene glycol bis(2-cyanoethyl) ether (F) is 0.1%, and the viscosity of the electrolyte (A) is 5.5 mPa·s.

[0090] (5) Assembly of lithium-ion batteries The positive electrode aluminum tab is installed in the edge clearance area 341 of the positive electrode sheet 410 by rolling, and the protective adhesive is pasted on the edge area of ​​the positive electrode sheet 410. The negative electrode nickel tab is installed in the edge clearance area 341 of the negative electrode sheet 420 by rolling.

[0091] The positive electrode 410 with a positive tab, the separator 50, and the negative electrode 420 with a negative tab are stacked sequentially, with the separator 50 positioned between the positive electrode 410 and the negative electrode 420 to provide insulation. The electrode assembly is then wound to form the electrode body 20. The electrode assembly is placed in an outer aluminum-plastic film package and dried in an 85°C vacuum oven for 12 hours to remove moisture. Electrolyte is then injected, and the battery undergoes vacuum sealing, settling, formation (constant current charging at 0.2°C to 3.5V, followed by constant current charging at 1C to 3.9V), capacity testing, degassing, and edge trimming to obtain the lithium-ion battery.

[0092] In Example 1-1, the negative electrode sheet 420 has a first protrusion 301 and a second protrusion 302. The protrusion 311 is rolled out of the negative electrode sheet 420 by a rolling process, and then... Figure 4 The electrode 300 shown is used as the negative electrode 420.

[0093] Examples 1-2 to 1-15 and Comparative Examples 1-1 to 1-6 are the same as in Example 1-1, except that the height Hm of the first protrusion 301 is adjusted according to Table 1 in the preparation of the negative electrode 420 and the weight percentage E of lithium difluorophosphate is adjusted according to Table 1 in the preparation of the electrolyte. The electrolytes in Comparative Examples 1-6 do not contain lithium difluorophosphate.

[0094] The parameters and performance test results of the lithium-ion batteries of Examples 1-1 to 1-15 and Comparative Examples 1-1 to 1-6 are shown in Table 1.

[0095] Table 1

[0096] Among them, the larger the number of charge-discharge cycles and the smaller the DCR value at 20% SOC 1s, the better the battery performance.

[0097] As can be seen from Examples 1-1 to 1-15 and Comparative Examples 1-1 to 1-6 in Table 1, by selecting the height Hm of the first protrusion of the electrode to satisfy 20 ≤ Hm ≤ 80, and selecting the weight percentage E of lithium difluorophosphate in the electrolyte to satisfy 0.01 ≤ E ≤ 3.00, lithium difluorophosphate can improve the ion flowability in the lithium salt, reduce interfacial side reactions, thereby improving the charge-discharge cycle performance of the battery and reducing the 1s DC impedance of the battery at 20% SOC. However, when Hm is below 20 μm or above 80 μm, the improvement of fast-charging performance of the battery by lithium difluorophosphate combined with the first protrusion 301 is limited. When the weight percentage E of lithium difluorophosphate is above 3.00%, problems such as high electrolyte viscosity and lithium ion enrichment at the electrode 300 interface also occur.

[0098] As can be seen from Examples 1-1 to 1-6, Hm satisfies 20≤Hm≤40, and as can be seen from Examples 1-7 to 1-15, E satisfies 0.01≤E≤3.00. This allows the electrolyte to have a more suitable viscosity and ion transport capability, thereby improving the electrolyte wetting effect, improving the charge-discharge cycle performance of the lithium-ion battery, and making the DCR value of the lithium-ion battery at 20% SOC 1s smaller.

[0099] Examples 2-1 to 2-18 are the same as those in Examples 1-3, except that the height Hm of the first protrusion 301 is adjusted according to Table 2 in the preparation of the negative electrode 420, and the weight percentage F of ethylene glycol bis(2-cyanoethyl) ether is adjusted according to Table 2 in the preparation of the electrolyte.

[0100] The parameters and performance test results of the lithium-ion batteries in Examples 2-1 to 2-18 are shown in Table 2.

[0101] Table 2

[0102] As can be seen from Examples 2-1 to 2-14 and Examples 1-3 in Table 2, by selecting the weight percentage F of ethylene glycol bis(2-cyanoethyl) ether to satisfy 0.1≤F≤1. and selecting the height Hm of the first protrusion 301 to satisfy 20≤Hm≤80, Hm matches F. When the first protrusion 301 of the corner portion 202 has a higher height, ethylene glycol bis(2-cyanoethyl) ether can effectively improve the stability of the solid electrolyte interface film, improve the low-temperature high-rate discharge performance and intermittent cycle performance of the battery, and reduce the amount of gas generated in the long cycle of the battery.

[0103] According to Examples 2-1 to 2-8, F satisfies 0.1≤F≤1.8, and according to Examples 2-9 to 2-14, Hm satisfies 20≤Hm≤60. Ethylene glycol bis(2-cyanoethyl) ether can better stabilize the problem of uneven solid electrolyte interface film caused by the presence of protrusion 311, and assist lithium difluorophosphate in forming a more stable solid electrolyte interface film at the interface of positive electrode 410, so as to improve the low-temperature high-rate discharge performance and charge-discharge cycle performance of the battery.

[0104] Examples 3-1 to 3-13 are the same as those in Examples 1-3, except that the height Hm of the first protrusion 301 is adjusted according to Table 3 in the preparation of the negative electrode 420, and the viscosity A of the electrolyte is adjusted according to Table 3 in the preparation of the electrolyte.

[0105] The parameters and performance test results of the lithium-ion batteries in Examples 3-1 to 3-13 are shown in Table 3.

[0106] Table 3

[0107] As can be seen from Examples 3-1 to 3-13 and Examples 1-3 in Table 3, by selecting an electrolyte viscosity A that satisfies 4.0≤A≤7.0 and a first protrusion height Hm that satisfies 20≤Hm≤80, the electrolyte viscosity A is matched with the height Hm of the first protrusion 301, so that there is a suitable distance between the electrode 300 and the separator 50. This helps to improve the electrolyte wetting rate and facilitates the selection of lithium difluorophosphate content within a suitable range, so that lithium difluorophosphate forms a solid electrolyte interface film of suitable thickness at the interface of the positive electrode 410. This can effectively improve the low-temperature high-rate discharge performance and charge-discharge cycle performance of lithium-ion batteries, as well as improve the pass rate of high-temperature hot box tests of batteries.

[0108] As can be seen from Examples 3-1 to 3-7 and Examples 1-3, by selecting an electrolyte viscosity A that further satisfies 5.0≤A≤6.5 and a first protrusion height Hm that satisfies 20≤Hm≤40, the various performance characteristics of the lithium-ion battery can be further improved.

[0109] Examples 4-1 to 4-13 are the same as in Example 3-1, except that the height Hm of the first protrusion 301 is adjusted according to Table 4 in the preparation of the negative electrode 420, and the type of lithium salt or the weight percentage K of lithium difluorooxalate borate is adjusted according to Table 4 in the preparation of the electrolyte.

[0110] The parameters and performance test results of the lithium-ion batteries in Examples 4-1 to 4-13 are shown in Table 4.

[0111] Table 4

[0112] As can be seen from Examples 4-1 to 4-4 and Example 3-1 in Table 4, the lithium salt in the electrolyte is selected from lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalate borate, lithium difluorosulfonylimide, or lithium tetrafluoroborate. The lithium-ion battery exhibits good performance in low-temperature high-rate discharge, charge-discharge cycle performance, and high-temperature hot box test pass rate.

[0113] As can be seen from Examples 4-4 to 4-13 in Table 4, when the electrolyte includes lithium difluorooxalate borate, the weight percentage K of lithium difluorooxalate borate satisfies 3.0≤K≤10.0, allowing lithium difluorooxalate borate to dissolve in the electrolyte. Furthermore, the height Hm of the first protrusion satisfies 20≤Hm≤80, ensuring a suitable gap between the electrode 300 and the separator 50. This improves the wetting effect of the electrolyte into the active material layer, enabling the application of lithium difluorooxalate borate in the electrolyte. This, in turn, improves the thermal performance of the lithium-ion battery and enhances its low-temperature, high-rate discharge performance.

[0114] Examples 5-1 to 5-10 are the same as in Example 3-1, except that carbon nanotubes were used to replace conductive carbon black in the preparation of the negative electrode 420 as shown in Table 5, and the length L and diameter D1 of the carbon nanotubes were adjusted.

[0115] The parameters and performance test results of the lithium-ion batteries in Examples 5-1 to 5-10 are shown in Table 5.

[0116] Table 5

[0117] As can be seen from Examples 5-1 to 5-5 and Example 3-1 in Table 5, the height Hn of the second protrusion 302 satisfies 5≤Hn≤40 and 1.5≤Hm / Hn≤5. The height Hm of the first protrusion 301 and the height Hn of the second protrusion 302 are appropriately proportioned, providing better support for the straight portion 201 and the corner portion 202 of the electrode body 20, improving the wetting effect of the electrolyte, and helping to form a uniform solid electrolyte interface film at the first protrusion 301, thereby improving the various performance characteristics of the lithium-ion battery.

[0118] As can be seen from Examples 5-6 to 5-11 in Table 5, by selecting the diameter Rm of the inner surface of the first protrusion 301 to satisfy 0.3≤Rm≤10, it is easy to match with the height Hm of the first protrusion 301, so that the first protrusion 301 of the electrode 300 has a suitable elongation and a suitable sharpness, and the first protrusion 301 has good support stability, which helps to form a uniform solid electrolyte interface film at the first protrusion 301, thereby improving the various performances of the lithium-ion battery.

[0119] As can be seen from Examples 5-12 to 5-17 in Table 5, by selecting the length L of the carbon nanotube to satisfy 0.2≤L≤5, the carbon nanotube is of suitable length, which makes the active material layer at the first protrusion 301 and the second protrusion 302 have good morphological stability, and is not prone to abnormalities such as cracks and shedding. It also improves the electronic conductivity of the electrode and the effect of floating charging of lithium-ion batteries at 45°C.

[0120] As can be seen from Examples 5-18 to 5-25 in Table 5, by selecting the diameter D1 of the carbon nanotubes to satisfy 5≤D1≤18, the interfacial side reactions in the electrode can be reduced, thereby improving the charge-discharge cycle performance of the lithium-ion battery and the performance of the battery thermal box.

[0121] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0122] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery, characterized in that, The device includes an outer packaging, an electrode assembly, and an electrolyte, wherein the electrode assembly is disposed within the internal space of the outer packaging, and the electrolyte fills the internal space of the outer packaging. The electrode assembly includes a separator and multiple electrode sheets. The separator is disposed between two electrode sheets with opposite polarities, and the electrode sheets and the separator are wound multiple times to form an electrode body. The electrode body includes a straight portion and corner portions disposed at opposite ends of the straight portion. The corner portions of the electrode sheets are provided with multiple first protrusions. Along the thickness direction of the electrode sheet, the height of the first protrusion is Hm, in μm, and Hm satisfies: 20≤Hm≤80. The electrolyte includes lithium difluorophosphate, and the weight percentage of lithium difluorophosphate based on the total weight of the electrolyte is E, in %, where E satisfies: 0.01≤E≤3.00; The diameter of the inner surface of the first protrusion is Rm, in mm, and satisfies: 0.3≤Rm≤10.

2. The battery according to claim 1, characterized in that, The battery satisfies the following conditions: 0.01≤E≤1.8, 20≤Hm≤40.

3. The battery according to claim 1, characterized in that, The viscosity of the electrolyte is A, with units of mPa·s, and the battery satisfies: 4.0 ≤ A ≤ 7.

0.

4. The battery according to claim 3, characterized in that, The battery satisfies the following conditions: 5≤A≤6.5, 20≤Hm≤40.

5. The battery according to claim 1, characterized in that, The electrolyte also includes a lithium salt selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, and lithium tetrafluoroborate.

6. The battery according to claim 1, characterized in that, The electrolyte also includes a lithium salt, which includes lithium difluorooxalate borate. Based on the total weight of the electrolyte, the weight percentage of lithium difluorooxalate borate is K, in % , where K satisfies: 3.0 ≤ K ≤ 10.

0.

7. The battery according to claim 6, characterized in that, The battery satisfies the following conditions: 3.0≤K≤8.0, 20≤Hm≤60.

8. The battery according to any one of claims 1-7, characterized in that, The electrode has a plurality of second protrusions corresponding to the flat portion. Along the thickness direction of the electrode, the height of each second protrusion is Hn (in μm); the diameter of the inner surface of each second protrusion is Rn (in mm); the battery satisfies at least one of the following conditions: (1) 5 ≤ Hn ≤ 40; (2) 1.25≤Hm / Hn≤5; (3) Rm = Rn.

9. The battery according to any one of claims 1-8, characterized in that, The electrode includes a current collector and an active material layer disposed on the surface of the current collector. The active material layer includes carbon nanotubes with a length of L in μm, where L satisfies: 0.2 ≤ L ≤ 5.

10. The battery according to claim 9, characterized in that, The diameter of the carbon nanotube is D1, in nm, and D1 satisfies: 5≤D1≤18.

11. The battery according to claim 1, characterized in that, The electrolyte also includes ethylene glycol bis(2-cyanoethyl) ether. Based on the total weight of the electrolyte, the weight percentage of ethylene glycol bis(2-cyanoethyl) ether is F, in % and F satisfies: 0.2≤F≤1.

8.

12. The battery according to claim 11, characterized in that, The battery satisfies the following condition: 20 ≤ Hm ≤ 60.

13. The battery according to claim 12, characterized in that, The battery satisfies the following conditions: 0.3≤F≤1.2, 20≤Hm≤40.

14. An electrical appliance, characterized in that, include: shell; and, The battery according to any one of claims 1-13, wherein the battery is disposed in the internal space of the housing.

Images