Battery and electric device

Abstract

This invention relates to the field of battery technology and discloses a battery and an electrical device, comprising: a battery cell, a first electrode including a bent portion, the first electrode including a current collector and an active material layer disposed in the current collector; a protective layer disposed on at least one side surface of the bent portion, with the protective layer disposed in at least a central region along the width direction, the protective layer including an insulating layer and an adhesive layer, and having at least a first through-hole in the insulating layer; the puncture resistance of the protective layer is F, the width of the protective layer is L, the ratio of the thickness of the active material layer to the thickness of the first electrode is m, and the pore density of the insulating layer in the central region is P, satisfying 0.04≤L / (F×P×m)≤23.22. This invention, while ensuring the protective effect of the protective layer on the active material layer and preventing material shedding from the active material layer, improves the wetting effect of the battery and the lithium-ion transport efficiency, reduces the risk of lithium plating, thereby reducing the risk of battery short circuit and improving battery safety performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to batteries and electrical devices. Background Technology

[0002] To meet the demand for high energy density in batteries, battery volume is constantly increasing. For wound battery cells, a protective layer is usually placed at the bends to reduce material loss. However, the protective layer poses a risk of lithium ions precipitating as lithium dendrites, affecting battery safety performance. Summary of the Invention

[0003] This invention provides a battery and an electrical device to solve the problem in the prior art where the protective layer at the bending part of the battery cell poses a risk of lithium ions precipitating in the form of lithium dendrites, affecting the safety performance of the battery.

[0004] In a first aspect, the present invention provides a battery comprising:

[0005] shell;

[0006] A battery cell is disposed within the housing. The battery cell is formed by winding a first electrode, a separator, and a second electrode that are stacked together. The battery cell includes a bent section and a straight section. The first electrode includes a bent portion that forms the bent section. The battery cell includes a tab that extends along the width direction of the first electrode. The first electrode includes a current collector and an active material layer disposed on at least one side of the current collector.

[0007] A protective layer is disposed on at least one side surface of the bent portion. Along the width direction of the first electrode, the area from 1 / 3 to 2 / 3 of the distance from the edge of the bent portion is the central region. The protective layer is disposed at least in the central region. The protective layer includes an isolation layer and an adhesive layer. The adhesive layer is disposed on the side of the isolation layer facing the bent portion. At least a plurality of first through holes are formed in the isolation layer.

[0008] Wherein, the puncture resistance of the protective layer is FN, the width of the protective layer along the length of the first electrode is L mm, the ratio of the thickness of the active material layer to the thickness of the first electrode is m, and the pore density of the isolation layer in the middle region is P%, satisfying 0.04≤L / (F×P×m)≤23.22.

[0009] Beneficial effects: By creating a first through-hole in the separator layer, a wetting channel is provided for the electrolyte, allowing for more thorough wetting of the electrolyte in the central region. This also serves as a lithium-ion transport channel, significantly reducing lithium plating inside the battery, minimizing lithium dendrite formation, and lowering the risk of short circuits caused by separator puncture. Furthermore, by limiting the range of L / (F×P×m), the protective layer's effectiveness against the active material layer is ensured, preventing material shedding from the active material layer while improving the battery's wetting effect and lithium-ion transport efficiency, reducing the risk of lithium plating, and consequently lowering the risk of short circuits and improving battery safety performance.

[0010] Secondly, the present invention also provides an electrical device comprising at least two of the aforementioned batteries. Attached Figure Description

[0011] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of the first electrode and the protective layer in the first embodiment of the present invention;

[0013] Figure 2 This is a schematic diagram of the structure of the second type of first electrode and protective layer according to an embodiment of the present invention;

[0014] Figure 3 This is a schematic diagram of the structure of the current collector having active material layers on both opposite sides according to an embodiment of the present invention;

[0015] Figure 4 A schematic diagram of a structure in which an active material layer is provided on one side of a current collector according to an embodiment of the present invention;

[0016] Figure 5 This is a schematic diagram of the structure of the isolation layer with a first through hole in an embodiment of the present invention;

[0017] Figure 6 This is a schematic diagram of the structure of the first colloidal region and the void region according to an embodiment of the present invention;

[0018] Figure 7 This is a schematic diagram of the structure of the second type of colloidal region and void region according to an embodiment of the present invention;

[0019] Figure 8 This is a schematic diagram of the structure of the third type of colloidal region and void region in an embodiment of the present invention;

[0020] Figure 9for Figure 8 A cross-sectional view along the AA direction;

[0021] Figure 10 This is a schematic diagram of the structure of the fourth type of colloidal region and void region according to an embodiment of the present invention;

[0022] Figure 11 This is a schematic diagram of the structure in an embodiment of the present invention, showing that the end of the protective layer does not extend beyond the edge of the active material layer;

[0023] Figure 12 This is a schematic diagram of the structure of the protective layer in an embodiment of the present invention, showing that the end of the protective layer extends beyond the edge of the active material layer but does not extend beyond the edge of the diaphragm.

[0024] Figure 13 This is a schematic diagram of the structure of the protective layer extending beyond the edge of the diaphragm in an embodiment of the present invention;

[0025] Figure 14 This is a schematic diagram of the protective layer extending to the straight section according to an embodiment of the present invention;

[0026] Figure 15 This is a schematic diagram of a structure in which protective layers are provided on both opposite sides of the bent portion according to an embodiment of the present invention.

[0027] Figure 16 This is a schematic diagram of the cooperative structure of the injection hole, the first electrode, and the protective layer in an embodiment of the present invention;

[0028] Figure 17 This is a schematic diagram of the battery cell structure according to an embodiment of the present invention;

[0029] Figure 18 This is a schematic cross-sectional view of the battery cell in an embodiment of the present invention, in the direction perpendicular to the width of the electrode sheet;

[0030] Figure 19 This is a schematic diagram of the battery explosion according to an embodiment of the present invention;

[0031] Figure 20 This is a schematic diagram of the crease and protective layer at the bend in an embodiment of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Outer shell; 11. Injection hole; 12. Shell; 13. Cover plate assembly; 2. Cell; 21. First electrode; 211. Bending section; 2111. Middle region; 2112. End region; 2113. Crease; 212. Current collector; 213. Active material layer; 214. Straight section; 22. Separator; 23. Bending section; 24. Straight section; 25. Tab; 3. Protective layer; 31. Separating layer; 311. First end; 312. Second end; 32. Adhesive layer; 321. Colloidal region; 322. Void region; 33. First through hole; 34. Second through hole. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Research has found that during the use of battery cells, lithium plating is a serious problem in the areas where protective layers are attached at the bends, especially in the middle area, where the wetting effect is worse than that of the two end areas. This results in poorer lithium-ion transport efficiency in the middle area, leading to more severe lithium plating and posing a safety hazard to the battery.

[0036] The following is combined Figures 1 to 20 The following describes embodiments of the present invention.

[0037] According to an embodiment of the present invention, a battery is provided, comprising: a casing 1; and a battery cell 2 disposed within the casing 1. The battery cell 2 is formed by winding a first electrode 21, a separator 22, and a second electrode that are stacked together. The battery cell 2 includes a bent section 23 and a straight section 24. The first electrode 21 includes a bent portion 211 for forming the bent section 23. The battery cell 2 includes a tab portion 25 extending along the width direction of the first electrode 21. The first electrode 21 includes a current collector 212 and an active material disposed on at least one side of the current collector 212. Layer 213; Protective layer 3, disposed on at least one side surface of the bending portion 211, with the central region 2111 located 1 / 3 to 2 / 3 of the distance from the edge of the bending portion 211 along the width direction of the first electrode 21, and the protective layer 3 is disposed at least in the central region 2111. The protective layer 3 includes an isolation layer 31 and an adhesive layer 32, with the adhesive layer 32 disposed on the side of the isolation layer 31 facing the bending portion 211, and at least a plurality of first through holes 33 are formed in the isolation layer 31. The puncture resistance of the protective layer 3 is FN, the width of the protective layer 3 along the length direction of the first electrode 21 is L mm, the ratio of the thickness of the active material layer 213 to the thickness of the first electrode 21 is m, and the pore density of the isolation layer 31 in the central region 2111 is P%, satisfying 0.04≤L / (F×P×m)≤23.22.

[0038] The battery using this embodiment provides a wetting channel for the electrolyte by creating a first through-hole 33 in the separator 31. This allows for more thorough wetting of the electrolyte in the central region 2111 and serves as a lithium-ion transport channel, thereby significantly reducing lithium plating inside the battery, minimizing lithium dendrite formation, and lowering the risk of short circuits caused by puncturing the separator 22. Furthermore, by limiting the range of L / (F×P×m), the protective effect of the protective layer 3 on the active material layer 213 is ensured, preventing material shedding from the active material layer 213 while improving the wetting effect and lithium-ion transport efficiency, reducing the risk of lithium plating, and thus lowering the risk of short circuits and improving battery safety performance.

[0039] It is worth noting that if the value of L / (F×P×m) is too large, the wetting effect of the electrolyte will be poor, the lithium ion transport efficiency will be poor, the risk of lithium dendrite formation will increase, and the risk of the separator 22 being punctured and causing a short circuit between the positive and negative electrodes will increase, affecting the safety performance of the battery. If the value of L / (F×P×m) is too small, the protective layer 3 will not provide sufficient protection for the active material layer 213, increasing the risk of material loss from the active material layer 213.

[0040] Specifically, if the value of L is too small, the coverage area of ​​the bending portion 211 will be too small, posing a risk of material loss in the uncovered areas of the bending portion 211; if the value of L is too large, the coverage area of ​​the bending portion 211 will be too large, affecting the lithium-ion transport efficiency and exacerbating the lithium plating problem in the battery. If the value of F is too small, the protective layer 3 will be easily pierced by lithium dendrites, posing a risk of short circuit between the positive and negative electrodes and affecting the battery's safety performance; if the value of F is too large, the protective layer 3 will not be easily deformed, and it will not be easily bent synchronously when the bending portion 211 is bent, making it easy for the active material layer 213 to be peeled off when the protective layer 3 is bent. If the value of P is too small, the channels for the transport of electrolyte and lithium ions will be too small, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuit between the positive and negative electrodes due to puncture of the separator 22, thus affecting the safety performance of the battery. If the value of P is too large, it will easily affect the reliability of the adhesive layer 32 adhering to the bending part 211, which may easily cause the protective layer 3 to fall off, or even peel off the active material layer 213. If the value of m is too large, the active material layer 213 will be too thick, resulting in poor binding force on the surface of the active material layer 213, which may easily cause the active material layer 213 to fall off. If the value of m is too small, the active material layer 213 will be too thin, reducing the capacity for lithium ions and easily causing lithium plating problems.

[0041] Optionally, L / (F×P×m) can take any value from 0.04, 0.08, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 5.9, 6, 6.45, 7, 7.5, 8, 10, 12, 15, 18, 20, 22, 23.22, or a value between any two values.

[0042] Preferably, the puncture resistance FN of the protective layer 3, the width L mm of the protective layer 3 along the length direction of the first electrode 21, the ratio m of the thickness of the active material layer 213 to the thickness of the first electrode 21, and the pore density P% of the isolation layer 31 in the central region 2111 satisfy 0.08≤L / (F×P×m)≤6.45.

[0043] It should be noted that, in one embodiment, more preferably, the first through-hole 33 can be formed only in the separator 31, that is, the first through-hole 33 only penetrates the separator 31 and does not extend to the adhesive layer 32. Since the electrolyte is an organic solvent and the adhesive layer 32 is an organic polymer material, during battery use, the adhesive layer 32 corresponding to the first through-hole 33 will swell, increasing the gaps between molecular chains, and may even cause the adhesive layer 32 to detach, thereby allowing the electrolyte and lithium ions to pass through.

[0044] Of course, in other alternative embodiments, a first through hole 33 can also be formed in the adhesive layer 32, that is, the first through hole 33 can penetrate both the insulating layer 31 and the adhesive layer 32.

[0045] It should be further explained that the above-mentioned "at least the central region 2111 is provided with a protective layer 3" means that: along the width direction of the first electrode 21, the protective layer 3 can be provided only in the central region 2111, while no protective layer 3 is provided in the region outside the central region 2111; of course, the protective layer 3 can also be provided in the central region 2111, and the protective layer 3 can also be provided in the region outside the central region 2111. In this case, the first through hole 33 can be provided only on the isolation layer 31 corresponding to the central region 2111, and of course, the first through hole 33 can also be provided on the isolation layer 31 corresponding to the region outside the central region 2111.

[0046] In this embodiment, the puncture resistance F of the protective layer 3 can be adjusted using the following method:

[0047] The puncture resistance (F) of the protective layer can be controlled by adjusting the material of the isolation layer, its thickness, the size of the pores, and the spacing between the pores. For example, using a high-strength substrate such as nylon (PA) or polyester film (PET) can significantly improve puncture resistance. A multi-layered composite isolation layer can also be used to disperse the puncture force. Increasing the thickness of the isolation layer can also effectively increase puncture resistance. Reducing the pore size of individual pores or increasing the spacing between pores can also improve the puncture resistance of the protective layer.

[0048] In this embodiment, the pore density P of the isolation layer 31 in the central region 2111 can be controlled by the following method:

[0049] The diameter of a single through-hole can be adjusted, and / or the spacing between adjacent through-holes can be adjusted to increase the pore density. Increasing the diameter of a single through-hole increases the pore density, while decreasing the spacing between adjacent through-holes increases the pore density.

[0050] Specifically, in one embodiment, the material of the insulating layer 31 is: polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, or hexafluoropropylene. Vinylidene fluoride copolymer, tetrafluoropropylene Vinylidene fluoride copolymer, trifluorochloropropylene Any one of the following: vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, and nonwoven fabric.

[0051] Specifically, in one embodiment, the adhesive layer 32 is made of any one of the following: acrylic acid-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic acid copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic acid-grafted polyethylene, maleic anhydride-grafted polyethylene, acrylic acid-grafted polypropylene, maleic anhydride-grafted polypropylene, polyvinylidene fluoride, carboxymethyl cellulose, polyimide, polyetherimide, polyethylene phthalate, styrene-isoprene-styrene copolymer rubber, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, and styrene-isoprene-styrene copolymer.

[0052] Specifically, in one embodiment, such as Figure 5 As shown, the diameter of a single first through-hole 33 is a μm, satisfying 10μm≤a μm≤500μm. This configuration ensures the adhesion between the protective layer 3 and the bending portion 211, while also guaranteeing the wetting effect of the electrolyte and the lithium ion transport efficiency.

[0053] It is worth noting that if the value of 'a' is too small, the channels for electrolyte and lithium ion transport will be too small, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuit between the positive and negative electrodes due to puncture of the separator 22, thus affecting the safety performance of the battery. If the value of 'a' is too large, it may affect the reliability of the adhesive layer 32 adhering to the bending part 211, which may easily lead to the detachment of the protective layer 3, or even the peeling off of the active material layer 213.

[0054] It should be noted that the first through hole 33 is disposed through the insulating layer 31 along the thickness direction of the first electrode 21. The aperture 'a' μm of a single first through hole 33 refers to the aperture of the first through hole 33 as projected onto a plane perpendicular to the thickness direction.

[0055] Specifically, in one embodiment, the first through hole 33 is a cylindrical hole; see below for details. Figure 5 The orthographic projection of the first through hole 33 onto the projection plane perpendicular to the thickness direction is a circle, and the diameter of the circle ranges from 10μm to 500μm.

[0056] Optionally, the value of 'a' can be any value from 10, 20, 50, 80, 100, 150, 200, 250, 300, 350, 400, 420, 450, 480, 500, or a value between any two values.

[0057] Specifically, in one embodiment, such as Figure 5As shown, the distance between adjacent first through holes 33 is b μm, satisfying 500μm≤b μm≤2000μm. This setting ensures the adhesion between the protective layer 3 and the bending portion 211, while also guaranteeing the wetting effect of the electrolyte and the lithium ion transport efficiency.

[0058] It is worth noting that if the value of b is too large, the barrier effect of the separator 31 on the electrolyte and lithium ions will be too great, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuit between the positive and negative electrodes due to puncture of the separator 22, thus affecting the safety performance of the battery. If the value of b is too small, it may affect the reliability of the adhesive layer 32 adhering to the bending part 211, which may easily lead to the detachment of the protective layer 3, or even peel off the active material layer 213.

[0059] Optionally, the value of b can be any value from 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, or a value between any two values.

[0060] It should be noted that the distance b μm between adjacent first through holes 33 refers to the distance between the geometric centers of the orthographic projections of adjacent first through holes 33 onto a projection plane perpendicular to the thickness direction.

[0061] For example, the first through hole 33 is a cylindrical hole, and correspondingly, as shown in the figure. Figure 5 As shown, the orthographic projection of the first through hole 33 onto the projection plane perpendicular to the thickness direction is a circle, and the distance b μm between adjacent first through holes 33 is the center distance between the two circular projections.

[0062] It is worth noting that the length direction of the first electrode 21 refers to the winding direction of the first electrode 21, the width direction of the first electrode 21 refers to the lead-out direction of the electrode tab 25, and the width direction of the first electrode 21 is perpendicular to the length direction of the first electrode 21.

[0063] In one embodiment, the pore density P% of the isolation layer 31 in the central region 2111 satisfies 1%≤P%≤30%. This configuration ensures the adhesion between the protective layer 3 and the bending portion 211, while also guaranteeing the wetting effect of the electrolyte and the lithium ion transport efficiency.

[0064] It is worth noting that if the value of P is too small, the channels for the electrolyte and lithium ions to transport are too small, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuit between the positive and negative electrodes due to puncture of the separator 22, thus affecting the safety performance of the battery. If the value of P is too large, it can easily affect the reliability of the adhesive layer 32 adhering to the bending part 211, which can easily lead to the detachment of the protective layer 3, or even the peeling off of the active material layer 213.

[0065] Optionally, P can take any value from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 18, 20, 22, 25, 28, 30, or a value between any two values.

[0066] Preferably, the pore density P% of the isolation layer 31 in the central region 2111 satisfies 3%≤P%≤25%.

[0067] In one embodiment, such as Figure 5 As shown, along the width direction of the first electrode 21, the insulating layer 31 has a first end 311 near the tab 25. The minimum distance between the first end 311 and the first through hole 33 is c mm, satisfying 0.5 mm ≤ c mm ≤ 53 mm. This configuration ensures the strong adhesion between the protective layer 3 and the bent portion 211 while further guaranteeing the lithium ion transport effect.

[0068] It is worth noting that if the value of c is too small, the adhesion between the protective layer 3 and the bending portion 211 in the area near the first end 311 will be reduced, making it easy for the protective layer 3 to detach from the bending portion 211, or even peel off the active material layer 213. In addition, since the heat generated at the tab portion 25 is concentrated during battery use, the regional resistance of the electrode near the tab portion 25 will increase. If the value of c is too large, it will not be effective in improving the lithium-ion transport efficiency in the area of ​​the electrode near the tab portion 25, thus affecting the cycle performance of the battery.

[0069] Optionally, c can take any value from 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 42, 45, 50, 53, or a value between any two values.

[0070] It should be noted that, in one embodiment, such as Figure 1 As shown, the tab 25 extends only from one side along the width direction of the first electrode 21, in which case the insulating layer 31 has only one first end 311. In another embodiment, as... Figure 2 As shown, the tab 25 extends out on both sides along the width direction of the first electrode 21, and at this time, the insulating layer 31 has two first ends 311.

[0071] It is worth noting that when measuring the minimum distance c between the first end 311 and the first through hole 33, first measure the distance c1 from the first through hole to the edge of the middle region along the width direction (which can be measured by SEM), then measure the distance c2 from the edge of the middle region to the first end (which can be measured by a laser scanning diameter gauge), and finally calculate c = c1 + c2.

[0072] In one embodiment, such as Figure 5 As shown, along the length of the first electrode 21, the two ends of the insulating layer 31 form second ends 312. The minimum distance between the second ends 312 and the first through hole 33 is d μm, satisfying 500 μm ≤ d μm ≤ 2000 μm. This configuration ensures the adhesion between the protective layer 3 and the bent portion 211, while also guaranteeing the wetting effect of the electrolyte and the lithium ion transport efficiency.

[0073] It is worth noting that if the value of d is too large, the barrier effect of the separator 31 on the electrolyte and lithium ions will be too great, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuit between the positive and negative electrodes due to the puncture of the separator 22, thus affecting the safety performance of the battery. If the value of d is too small, under the action of the electrolyte, the adhesive layer 32 is prone to swelling or even falling off in the area near the second end 312, which may affect the reliability of the adhesive layer 32 adhering to the bending part 211, thus easily causing the protective layer 3 to fall off, and even peeling off the active material layer 213.

[0074] Optionally, d can be any value from 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, or a value between any two values.

[0075] In one embodiment, such as Figures 6 to 10 As shown, the adhesive layer 32 includes a colloidal region 321 and a void region 322. Along the width direction of the first electrode 21, the height of the void region 322 is x mm, which satisfies 2 mm ≤ x mm ≤ 10 mm.

[0076] It is worth noting that if the value of x is too large, the setting range of the colloidal region 321 may be too small, affecting the reliability of the adhesion between the protective layer 3 and the bending part 211, which may easily lead to the detachment of the protective layer 3 or even the peeling off of the active material layer 213. If the value of x is too small, the area available for setting the first through hole 33 may be too small, and the barrier effect of the separator 31 on the electrolyte and lithium ions may be too large, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of the separator 22 being punctured, leading to a short circuit between the positive and negative electrodes, thus affecting the safety performance of the battery.

[0077] Optionally, x can take any value from 2, 3, 4, 5, 6, 7, 8, 9, 10 or a value between any two values.

[0078] Furthermore, in one embodiment, such as Figures 6 to 10 As shown, the first through hole 33 is located in the region opposite the isolation layer 31 and the vacancy area 322.

[0079] Furthermore, in one embodiment, such as Figures 6 to 10 As shown, a vacancy area 322 is provided in the central region 2111.

[0080] Preferably, in one embodiment, such as Figure 6 As shown, the vacancy area 322 is located on one side of the isolation layer 31 along the length direction of the first electrode 21, and the width of the vacancy area 322 is e mm, which satisfies 1 mm ≤ e mm ≤ 10 mm.

[0081] Optionally, the value of e can be any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a value between any two values.

[0082] More preferably, in one embodiment, such as Figure 7 As shown, the vacancy area 322 is located on both sides of the isolation layer 31 along the length direction of the first electrode 21. The total width of the vacancy area 322 is f mm, which satisfies 2 mm ≤ f mm ≤ 15 mm.

[0083] Optionally, f can take any value from 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a value between any two values.

[0084] It is worth noting that, such as Figure 7 As shown, along the length direction of the first electrode 21, the width of the vacancy area 322 set on one side of the isolation layer 31 is f1 mm, and the width of the vacancy area 322 set on the other side of the isolation layer 31 is f2 mm, satisfying f=f1+f2.

[0085] Alternatively, in another preferred embodiment, such as Figure 8 and Figure 9 As shown, along the width direction of the first electrode 21, the colloidal region 321 is provided at opposite ends of the isolation layer 31, and the vacancy region 322 is located between the two colloidal regions 321.

[0086] As an alternative implementation method, optionally, such as Figure 10As shown, along the length of the first electrode 21, the colloidal region 321 is disposed on opposite sides of the isolation layer 31, and the vacancy region 322 is located between the two colloidal regions 321. It is worth noting that, along the length of the first electrode 21, the protective layer 3 is usually disposed in the middle of the bend 211. If the protective layer 3 is missing adhesive in the middle of the length of the first electrode 21 (i.e., the vacancy region 322), it will have a certain impact on the protective effect of the bend 211 in the middle of the length of the first electrode 21.

[0087] In one embodiment, such as Figure 9 As shown, the thickness of the isolation layer 31 is g μm, satisfying 10μm≤g μm≤70μm. This setting ensures the protection of the active material layer 213 while avoiding any impact on the volumetric energy density of the battery.

[0088] It is worth noting that if the value of g is too small, the separator layer 31 may be pierced by lithium dendrites, leading to a short circuit risk between the positive and negative electrodes. If the value of g is too large, the separator layer 31 will occupy too much space inside the battery, affecting the volumetric energy density of the battery.

[0089] Optionally, g can take any value from 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, or a value between any two values.

[0090] In one embodiment, such as Figure 9 As shown, the thickness of the adhesive layer 32 is h μm, satisfying 10μm≤h μm≤50μm. This setting ensures the reliable adhesion of the protective layer 3 to the bending portion 211 while avoiding any impact on the volumetric energy density of the battery.

[0091] It is worth noting that if the value of h is too small, the adhesion between the adhesive layer 32 and the bending portion 211 may be weak, causing the protective layer 3 to easily detach from the bending portion 211, and even peeling off the active material layer 213. If the value of h is too large, the adhesive layer 32 will occupy too much space inside the battery, affecting the volumetric energy density of the battery.

[0092] Optionally, h can take any value from 10, 12, 15, 18, 20, 25, 30, 35, 40, 42, 45, 48, 50, or a value between any two values.

[0093] Furthermore, in one embodiment, the thickness of the isolation layer 31 is g μm, and the thickness of the adhesive layer 32 is h μm, satisfying g:h = (10:2) ~ (10:5). Preferably, g:h = 10:3.

[0094] In one embodiment, such as Figure 2As shown, along the width direction of the first electrode 21, the two sides of the central region 2111 are end regions 2112. At least a portion of the end regions 2112 are provided with a protective layer 3, and a second through hole 34 is provided in the isolation layer 31. By also providing a protective layer 3 in the end regions 2112 of the bent portion 211, the protective effect on the bent portion 211 is further ensured, reducing the risk of material falling out. Furthermore, the second through hole 34 in the isolation layer 31 provides a wetting channel for the electrolyte, making the electrolyte wetting of the end regions 2112 more sufficient, and can also serve as a lithium ion transport channel, thereby significantly reducing the lithium plating problem inside the battery, reducing the formation of lithium dendrites, and reducing the risk of short circuit caused by puncturing the separator 22.

[0095] Furthermore, in one embodiment, the pore density of the isolation layer 31 at the end region 2112 is Q%, satisfying Q < P. Since the wetting effect of the electrolyte in the end region 2112 is better than that in the middle region 2111, the lithium ion transport efficiency at the end region 2112 is better, and the risk of lithium plating is lower. Therefore, there is no need to provide too many second through holes 34, which can further ensure the adhesion reliability of the protective layer 3 at the end region 2112.

[0096] In one embodiment, the puncture resistance FN of the protective layer 3 satisfies 2N≤FN≤10N. This setting ensures both the protective effect of the protective layer 3 and its bending resistance, preventing the active material layer 213 from peeling off when the protective layer 3 is bent.

[0097] It is worth noting that if the value of F is too small, the protective layer 3 is easily punctured by lithium dendrites, posing a risk of short circuit between the positive and negative electrodes and affecting the battery's safety performance. If the value of F is too large, the protective layer 3 is not easily deformed, and it is not easy for the protective layer 3 to be bent synchronously when bending at the bending part 211, which makes it easy for the active material layer 213 to be peeled off when the protective layer 3 is bent.

[0098] Optionally, F can take any value from 2, 2.2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a value between any two values.

[0099] Preferably, the puncture resistance FN of the protective layer 3 satisfies 2.2N≤FN≤8N.

[0100] In one embodiment, such as Figure 1 As shown, the width L mm of the protective layer 3 along the length direction of the first electrode 21 satisfies 10 mm ≤ L mm ≤ 30 mm. This setting avoids material shedding from the active material layer 213 while reducing the risk of lithium plating in the battery.

[0101] It is worth noting that if the value of L is too small, the coverage area of ​​the bending part 211 will be too small, and there is a risk of material falling out in the uncovered areas of the bending part 211. If the value of L is too large, the coverage area of ​​the bending part 211 will be too large, which will affect the lithium-ion transport efficiency and exacerbate the lithium plating problem in the battery.

[0102] Optionally, L can be any value from 10, 12, 15, 18, 20, 22, 25, 28, 30, or a value between any two values.

[0103] Preferably, the width L mm of the protective layer 3 along the length direction of the first electrode 21 satisfies 12 mm ≤ L mm ≤ 28 mm.

[0104] In one embodiment, the ratio m of the thickness of the active material layer 213 to the thickness of the first electrode 21 satisfies 0.63 ≤ m ≤ 0.96. This setting reduces the risk of material shedding from the active material layer 213 while also reducing the risk of lithium plating in the battery.

[0105] It is worth noting that if the value of m is too large, the active material layer 213 will be too thick, resulting in poor binding force on the surface of the active material layer 213 and making it easy for the active material layer 213 to shed material. If the value of m is too small, the active material layer 213 will be too thin, reducing the capacity to accommodate lithium ions and making lithium plating more likely.

[0106] Optionally, m can take any value from 0.63, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.93, 0.95, 0.96, or a value between any two values.

[0107] Preferably, the ratio m of the thickness of the active material layer 213 to the thickness of the first electrode 21 satisfies 0.68≤m≤0.93.

[0108] It is worth noting that the "thickness of the active material layer 213" mentioned above refers to the total thickness v μm of the active material layer 213. Specifically, as shown in... Figure 4 As shown, when an active material layer 213 is provided only on one side of the current collector 212 along the thickness direction, the dimension v μm is the thickness of the active material layer 213; as Figure 3 As shown, when active material layers 213 are provided on both opposite surfaces of the current collector 212 along the thickness direction, the dimension v μm is the sum of the thicknesses of the two active material layers 213, that is, v = v1 + v2. In addition, the thickness of the first electrode 21 is w μm, therefore, m = v / w.

[0109] In one embodiment, the thickness v μm of the active material layer 213 satisfies 30μm≤v μm≤210μm; and the thickness w μm of the first electrode 21 satisfies 34μm≤w μm≤228μm.

[0110] Optionally, v can take any value from 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, or a value between any two values.

[0111] Optionally, w can take any value from 34, 45, 55, 65, 75, 85, 95, 105, 115, 125, 135, 145, 155, 165, 175, 185, 195, 205, 215, 225, 228, or a value between any two values.

[0112] Specifically, for the negative electrode, the thickness of the current collector 212 (copper foil) is 4μm to 12μm; when the active material layer 213 is silicon carbide, the thickness of the active material layer 213 is 30μm to 160μm; when the active material layer 213 is graphite, the thickness of the active material layer 213 is 40μm to 200μm.

[0113] Specifically, for the positive electrode, the thickness of the current collector 212 (aluminum foil) is 6μm to 18μm; when the active material layer 213 is lithium iron phosphate, the thickness of the active material layer 213 is 70μm to 210μm; when the active material layer 213 is ternary material, the thickness of the active material layer 213 is 30μm to 150μm.

[0114] In one embodiment, such as Figure 11 As shown, along the width direction of the first electrode 21, the end of the protective layer 3 is located within the edge of the active material layer 213, and the distance between the end of the protective layer 3 and the edge of the active material layer 213 is j mm, satisfying 1 mm ≤ j mm ≤ 15 mm. That is, the protective layer 3 is completely located within the active material layer 213, and the protective layer 3 does not extend beyond the active material layer 213. This configuration reduces the risk of material loss from the active material layer 213 while also reducing the risk of lithium plating in the battery.

[0115] It is worth noting that if the value of j is too large, the coverage area of ​​the protective layer 3 over the bending part 211 may be too small, posing a risk of material loss in the uncovered areas of the bending part 211. If the value of j is too large, the coverage area of ​​the bending part 211 may be too large, affecting the lithium-ion transport efficiency and exacerbating the lithium plating problem in the battery.

[0116] Optionally, j can take any value from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a value between any two values.

[0117] In one embodiment, such as Figure 12 As shown, along the width direction of the first electrode 21, the end of the protective layer 3 extends beyond the edge of the active material layer 213 by a width of i mm, satisfying i mm ≥ 0.1 mm. This arrangement ensures that the protective layer 3 completely covers the edge of the active material layer 213, further preventing the problem of material shedding from the active material layer 213.

[0118] Furthermore, in one embodiment, such as Figure 12 As shown, along the width direction of the first electrode 21, the end of the protective layer 3 is located between the edge of the active material layer 213 and the edge of the diaphragm 22.

[0119] Additionally, in another embodiment, such as Figure 13 As shown, along the width direction of the first electrode 21, the width of the end of the protective layer 3 extending beyond the edge of the separator 22 is k mm, satisfying 0.1 mm ≤ k mm ≤ 9.6 mm. Setting the protective layer 3 beyond the separator 22 allows the portion of the protective layer 3 extending beyond the separator 22 to provide support, reducing the risk of material falling out under the squeezing action of the separator 22 after the cell 2 is installed in the casing. However, if the protective layer 3 extends too far beyond the separator 22, it will affect the volumetric energy density of the battery.

[0120] Optionally, k can take any value from 0.1, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.6 or a value between any two values.

[0121] In one embodiment, such as Figure 14 As shown, the first electrode 21 also includes a straight portion 214 connected to the bent portion 211. The straight portion 214 forms a straight section 24. Along the length direction of the first electrode 21, the protective layer 3 extends to the straight portion 214. The width of the protective layer 3 on the straight portion 214 is n mm, satisfying n mm ≤ 15 mm. This configuration ensures the adhesion stability of the protective layer 3 on the first electrode 21 and the protection effect on the bent portion 211, while reducing the risk of lithium plating in the battery.

[0122] It is worth noting that if the value of n is too large, the coverage area of ​​the first electrode 21 will be too large, affecting the lithium-ion transport efficiency and exacerbating the lithium plating problem in the battery.

[0123] Optionally, n can take any value from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a value between any two values.

[0124] Specifically, in one embodiment, such as Figure 15 As shown, protective layers 3 are provided on both opposite sides of the bent portion 211. This design further prevents the active material layer 213 from shedding.

[0125] Specifically, in one embodiment, the first electrode 21 is wound into several turns, and a protective layer 3 is provided within the first five turns closest to the starting end of the winding of the first electrode 21. The first electrode 21 experiences greater stress within the first five turns closest to the starting end of the winding, making it more prone to material shedding. Therefore, providing a protective layer 3 within the first five turns closest to the starting end of the winding of the first electrode 21 reduces the risk of material shedding while ensuring the volumetric energy density of the battery.

[0126] It is worth noting that during the winding process of the first electrode 21, when the tail end of the first electrode 21 overlaps with the starting end of the winding for the fifth time along the stacking direction of the first electrode 21, it is the fifth turn formed by winding.

[0127] Of course, a protective layer 3 can also be provided at all the bends 211 of the first electrode 21 to further prevent the active material layer 213 from falling off.

[0128] Furthermore, such as Figure 20 As shown, the first electrode 21 is wound in several turns, and a crease 2113 is formed at the bend 211 of the first turn near the starting end of the winding of the first electrode 21. The protective layer 3 covers the crease 2113.

[0129] Specifically, such as Figure 20 As shown, along the length direction of the first electrode 21, the edge of the protective layer 3 extends beyond the crease 2113 by a distance of r mm, which satisfies r mm ≥ 3 mm.

[0130] Specifically, in one embodiment, such as Figure 16 and Figure 17 As shown, two bent sections 23 are arranged at relatively intervals, and a straight section 24 connects the two bent sections 23. Both bent sections 23 are provided with a protective layer 3. This arrangement further prevents the active material layer 213 from falling off.

[0131] Specifically, in one embodiment, a protective layer 3 is provided on the first electrode 21, and the first electrode 21 is a positive electrode. That is, the protective layer 3 can be provided only on the positive electrode.

[0132] Of course, in other alternative embodiments, a protective layer 3 is provided on both the first electrode 21 and the second electrode.

[0133] In one embodiment, such as Figure 16 As shown, the outer casing 1 includes a first surface opposite to the lead-out end of the tab portion 25 of the battery cell 2. The first surface has an injection hole 11. Along the width direction of the first electrode 21, the distance between the injection hole 11 and the edge of the first electrode 21 is t mm, satisfying 4 mm ≤ t mm ≤ 8.5 mm. This arrangement ensures the effective wetting of the battery cell 2 by the electrolyte while preventing excessive impact from the electrolyte on the first electrode 21, thus avoiding material shedding.

[0134] It is worth noting that if the value of t is too large, the distance between the injection hole 11 and the first electrode 21 will be too far, resulting in an excessively long electrolyte flow path. This is not conducive to wetting the cell 2, affecting the lithium-ion transport efficiency and easily causing lithium plating problems. If the value of t is too small, the distance between the injection hole 11 and the first electrode 21 will be too close. During electrolyte injection, the impact of the electrolyte on the edge of the first electrode 21 will be too great, increasing the risk of material loss from the active material layer 213.

[0135] Optionally, t can take any value from 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5 or a value between any two values.

[0136] Specifically, such as Figure 19 As shown, the outer casing 1 includes a housing 12 and a cover assembly 13. At least one end of the housing 12 is open. The cover assembly 13 is connected to the housing 12 and seals the opening. The cover assembly 13 and the housing 12 enclose a receiving space, and the battery cell 2 is disposed in the receiving space.

[0137] In one embodiment, such as Figure 16 As shown, along the extension direction of the straight section 24, the distance between the injection hole 11 and the edge of the protective layer 3 is u mm, satisfying 50 mm ≤ u mm ≤ 110 mm. This setting ensures the wetting effect of the electrolyte on the cell 2 while avoiding any impact on the lithium-ion transmission efficiency.

[0138] It is worth noting that if the value of u is too large, the distance between the injection hole 11 and the bend 211 may be too large, making it difficult to ensure sufficient wetting of the cell 2 and affecting the wetting effect of the electrolyte on the cell 2. If the value of u is too small, the coverage area of ​​the protective layer 3 may be too large, affecting the lithium-ion transport efficiency and exacerbating the lithium plating problem in the battery.

[0139] Optionally, the value of u can be any one of 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, or a value between any two of these values.

[0140] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, comprising at least two of the aforementioned batteries.

[0141] It is worth noting that batteries can serve as the operating power source for electrical devices, as well as the driving power source, replacing or partially replacing fuel or natural gas to provide driving power for vehicles. Electrical devices encompass a wide range of technological fields, including energy storage devices, electric ships, aircraft, laptops, power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0142] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0143] The preparation of the example battery and the comparative battery includes the following steps:

[0144] (1) Preparation of the positive electrode:

[0145] The prepared positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, it is cold-pressed and slit to obtain the positive electrode sheet. Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98):(4~1):(4~1).

[0146] (2) Preparation of negative electrode:

[0147] The negative electrode active material, conductive agent acetylene black, thickener CMC, and binder SBR are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained. The ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0148] (3) Preparation of electrolyte:

[0149] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0150] (4) Preparation of the diaphragm:

[0151] Polyethylene film is selected as the diaphragm.

[0152] (5) Preparation of lithium-ion batteries:

[0153] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence to form a battery cell, and a protective layer is attached. The battery cell is placed in a battery casing, which is a square casing. The battery is dried, injected with electrolyte, and then packaged, allowed to stand, formed, and capacitated to obtain a lithium-ion battery. The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate; the negative electrode active material can be selected from one or more negative electrode active materials, including artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0154] The relevant performance of the batteries in the above embodiments and comparative examples was tested, and the test results are recorded in Table 1. The test methods are as follows:

[0155] Performance 1: Battery capacity retention rate

[0156] Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The difference between the batteries in each embodiment and the comparative example lies in the values ​​of L, F, P, and m, as shown in Table 1; all other structures are the same. The lithium-ion batteries were charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, then charged with a constant voltage of 0.33C until the current dropped to 0.05C. After standing for 5 minutes, the batteries were discharged with a constant current of 0.33C to the lower limit voltage. This process was repeated three times to obtain the third discharge capacity Q1, which was taken as the fixed capacity.

[0157] The lithium-ion battery is charged at room temperature (25℃) with a constant current of 0.33C to the upper limit voltage, then charged with a constant voltage of 0.33C until the current drops to 0.05C. After resting for 5 minutes, the battery is discharged with a constant current of 0.33C to the lower limit voltage. This constitutes one cycle. After n cycles, the discharge capacity Qn of the battery on the nth cycle is recorded. The formula for calculating the battery capacity retention rate is "Capacity retention rate = Qn / Q1 × 100%". The number of cycles n when the capacity retention rate first falls below 80% is recorded as the number of cycles for that battery. If n is less than 1200, the battery is considered unqualified; otherwise, it is considered qualified.

[0158] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0159] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0160] Performance 2: Battery Lithium Plating

[0161] Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The difference between the batteries in each embodiment and the comparative example lies in the values ​​of L, F, P, and m, as shown in Table 1; all other structures are the same. The lithium-ion batteries were charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, then charged at a constant voltage until the current dropped to 0.05C. After resting for 5 minutes, the batteries were discharged at a constant current of 0.33C to the lower limit voltage. This constituted one cycle, and 2000 cycles were performed. Then, the lithium-ion batteries were charged at 0.33C to the upper limit voltage, with a cutoff current less than or equal to 0.05C, resulting in a fully charged battery.

[0162] Disassemble the battery, then remove the electrodes and observe the lithium plating on the surface of the negative electrode in the bend. The portion where the projection of a single protective layer overlaps with the negative electrode is the first region, and the lithium plating area of ​​the first region is measured and recorded as S1. The area of ​​the first region of the active material layer of a single protective layer in the bend is recorded as S2. According to the formula, the percentage of the lithium plating area on the surface of the first region = (S1 / S2) × 100%, the percentage of the lithium plating area on the surface of the first region is calculated. If the lithium plating area on the surface of the first region is less than 10%, it is considered slight lithium plating; if the lithium plating area on the surface of the first region is between 10% and 50%, it is considered moderate lithium plating; if the lithium plating area on the surface of the first region is greater than 50%, it is considered severe lithium plating. Severe lithium plating is unacceptable.

[0163] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0164] In this test, the positive electrode active material of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder satisfies 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder satisfies 95:2:1:2.

[0165] The test method for puncture resistance F can be carried out using the following steps:

[0166] Discharge the battery to the lower limit voltage at 0.33C, disassemble the battery, remove the protective layer, and refer to GB / T 37841. The 2019 Test Method for Puncture Resistance of Plastic Films and Sheets measures the puncture resistance force F.

[0167] When the positive electrode active material of the battery is lithium nickel cobalt manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate, the lower limit voltage is 2.5V; when the positive electrode active material of the battery is lithium nickel manganese oxide, the lower limit voltage is 3.5V.

[0168] The test method for the ratio m of the thickness of the active material layer to the thickness of the first electrode can be carried out using the following steps:

[0169] The battery was discharged to the lower limit voltage at 0.33C, the battery was disassembled, the electrode was removed, and the electrode was dried at 60℃ for 3 hours. The thickness d1 of the active material layer and the thickness d2 of the electrode were measured using a scanning electron microscope. The value of m was calculated according to the formula m=d1 / d2.

[0170] When the positive electrode active material of the battery is lithium nickel cobalt manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate, the lower limit voltage is 2.5V; when the positive electrode active material of the battery is lithium nickel manganese oxide, the lower limit voltage is 3.5V.

[0171] The following steps can be used to test pore density:

[0172] Remove the protective layer from the battery sample and dry it at 60°C for 60 minutes. After ensuring the sample is dry, measure the length and width of the protective layer sample with a micrometer and calculate the sample area.

[0173] The pore structure of the first through-hole in the protective layer sample was observed using a scanning electron microscope (SEM), and the total area of ​​the first through-hole on the protective layer sample was measured.

[0174] Pore ​​density calculation formula: Pore density = (Total area of ​​the first through hole / Sample area) × 100%.

[0175] The testing method for L can be implemented using the following steps:

[0176] Discharge the battery to the lower limit voltage at 0.33C, disassemble the battery, remove the electrode, and use vernier calipers to measure the length of the protective layer along the unfolding direction of the electrode, which is L.

[0177] Table 1:

[0178]

[0179] As can be seen from Table 1, in Examples 1 to 18, the value of L / (F×P×m) is in the range of 0.04 to 23.22. Therefore, the batteries in Examples 1 to 18 have a cycle count of not less than 1200 cycles and the batteries do not have serious lithium plating problems.

[0180] As can be seen from Table 1, in Comparative Example 1 and Comparative Example 3, the value of L / (F×P×m) is not in the range of 0.04 to 23.22 and is less than 0.04. Therefore, the batteries in Comparative Example 1 and Comparative Example 3 have a cycle count of less than 1200 cycles, and the battery capacity retention rate test is unqualified.

[0181] As can be seen from Table 1, in Comparative Examples 2, 4 and 5, the value of L / (F×P×m) is not in the range of 0.04 to 23.22 and is greater than 23.22. Therefore, the batteries in Comparative Examples 2, 4 and 5 have serious lithium plating problems.

[0182] The following defines and explains some of the terms used in this application.

[0183] The positive electrode is one of the core components in a battery that carries the positive electrode active material. During charging, metal ions (e.g., lithium ions in a lithium battery) are released from the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (e.g., lithium ions in a lithium battery) are released from the negative electrode and intercalate into the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0184] A positive electrode generally includes a positive current collector and a positive active material layer. The positive active material layer is coated on at least one surface of the positive current collector and includes: a positive active material, a conductive agent, and a binder. The positive active material includes, but is not limited to, at least one of the following: lithium phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive active materials for batteries. These positive active materials can be used alone or in combination. The lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Conductive agents include, but are not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon nanotubes, graphene, and carbon nanofibers. Binders include, but are not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resins, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan.

[0185] For the negative electrode, during battery charging, active ions (such as Li) from the positive electrode are embedded in the negative electrode, while electrons from the positive electrode are transferred to the negative electrode through the external circuit to maintain charge balance; during discharge, the active ions (such as Li) previously embedded in the negative electrode can be released, while electrons from the negative electrode are transferred to the positive electrode through the external circuit to maintain charge balance, thus achieving energy storage and release.

[0186] The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium with a silver-plated surface. A composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). The negative electrode active layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material can be a carbon-based material such as graphite, porous carbon, hard carbon, soft carbon, or mesophase carbon microspheres, or a silicon-based material such as elemental silicon, silicon oxides, silicon-carbon composites, or silicon-nitrogen composites. The conductive agent can be conductive carbon black, carbon nanotubes, etc., and the binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0187] A battery cell is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of carrying out electrochemical reactions such as charging and discharging.

[0188] A battery cell is the basic unit of a battery, typically consisting of a positive electrode, a negative electrode, and a separator. Lithium-ion cells primarily function by the movement of lithium ions between the positive and negative electrodes. In cylindrical cells, a three-layer thin-film structure is wound into a cylindrical electrode assembly, while in cuboid cells, the thin-film structure is wound or stacked into an electrode assembly with a roughly cuboid shape.

[0189] The tab is located on one side of the positive / negative current collector and is separately or integrally formed with the current collector. It is electrically connected to the current collector to conduct the current on the corresponding current collector. The tab is made of a metal material with good conductivity (such as copper, aluminum, or nickel).

[0190] A separator is placed between the positive and negative electrode plates to separate them and prevent them from short-circuiting due to contact.

[0191] The diaphragm can be at least one of glass fiber, nonwoven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be applied to the diaphragm surface. The coating can be an inorganic coating and / or an organic coating, wherein the inorganic coating material includes at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, and boehmite; and the organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0192] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery, characterized in that, include: Outer shell (1); A battery cell (2) is disposed inside the outer casing (1). The battery cell (2) is formed by winding a first electrode (21), a separator (22), and a second electrode stacked together. The battery cell (2) includes a bent section (23) and a straight section (24). The first electrode (21) includes a bent portion (211) which is used to form the bent section (23). The battery cell (2) includes a tab portion (25) which is led out along the width direction of the first electrode (21). The first electrode (21) includes a current collector (212) and an active material layer (213) disposed on at least one side of the current collector (212). A protective layer (3) is disposed on at least one side surface of the bent portion (211). Along the width direction of the first electrode (21), the middle region (2111) is located in the area from 1 / 3 to 2 / 3 of the edge of the bent portion (211). The protective layer (3) is disposed in at least the middle region (2111). The protective layer (3) includes an isolation layer (31) and an adhesive layer (32). The adhesive layer (32) is disposed on the side of the isolation layer (31) facing the bent portion (211). At least a plurality of first through holes (33) are provided in the isolation layer (31). The adhesive layer (32) includes a gel region (321) and a void region (322). The first through holes (33) are located in the region opposite to the isolation layer (31) and the void region (322). The void region (322) is disposed in the middle region (2111). Wherein, the puncture resistance of the protective layer (3) is FN, the width of the protective layer (3) along the length direction of the first electrode (21) is L mm, the ratio of the thickness of the active material layer (213) to the thickness of the first electrode (21) is m, and the pore density of the isolation layer (31) in the middle region (2111) is P%, satisfying 0.04≤L / (F×P×m)≤23.22, 1%≤P%≤30%, 2 N≤FN≤10 N, 10mm≤L mm≤30mm, and 0.63≤m≤0.

96.

2. The battery according to claim 1, characterized in that, The first electrode (21) is wound in several turns, and a crease (2113) is formed at the bend (211) of the first turn near the starting end of the first electrode (21), and the protective layer (3) covers the crease (2113).

3. The battery according to claim 2, characterized in that, Along the length direction of the first electrode (21), the edge of the protective layer (3) extends beyond the crease (2113) by a distance of r mm, satisfying r mm ≥ 3 mm.

4. The battery according to claim 1, characterized in that, Along the width direction of the first electrode (21), the insulating layer (31) has a first end (311) near the tab (25), and the minimum distance between the first end (311) and the first through hole (33) is c mm, satisfying 0.5 mm ≤ c mm ≤ 53 mm.

5. The battery according to claim 1, characterized in that, Along the length direction of the first electrode (21), the two ends of the isolation layer (31) form a second end (312), and the minimum distance between the second end (312) and the first through hole (33) is d μm, which satisfies 500μm≤d μm≤2000μm.

6. The battery according to claim 1, characterized in that, Along the width direction of the first electrode (21), the height of the vacancy area (322) is x mm, satisfying 2mm≤x mm≤10mm.

7. The battery according to claim 1, characterized in that, The vacancy area (322) is located on one side of the isolation layer (31) along the length direction of the first electrode (21), and the width of the vacancy area (322) is e mm, satisfying 1 mm ≤ e mm ≤ 10 mm.

8. The battery according to claim 1, characterized in that, The vacancy area (322) is located on opposite sides of the isolation layer (31) along the length direction of the first electrode (21), and the total width of the vacancy area (322) is f mm, satisfying 2 mm ≤ f mm ≤ 15 mm.

9. The battery according to any one of claims 1 to 8, characterized in that, The thickness of the isolation layer (31) is g μm, satisfying 10 μm ≤ g μm ≤ 70 μm; and / or, The thickness of the adhesive layer (32) is h μm, which satisfies 10μm≤h μm≤50μm.

10. The battery according to any one of claims 1 to 8, characterized in that, Along the width direction of the first electrode (21), the two sides of the middle region (2111) are end regions (2112), at least part of the end regions (2112) are provided with the protective layer (3), and a second through hole (34) is opened in the isolation layer (31).

11. The battery according to claim 10, characterized in that, The pore density of the isolation layer (31) at the end region (2112) is Q%, which satisfies Q < P.

12. The battery according to any one of claims 1 to 8, characterized in that, Along the width direction of the first electrode (21), the width of the end of the protective layer (3) extending beyond the edge of the active material layer (213) is i mm, satisfying i mm ≥ 0.1 mm.

13. The battery according to any one of claims 1 to 8, characterized in that, Along the width direction of the first electrode (21), the end of the protective layer (3) is located within the edge of the active material layer (213), and the distance between the end of the protective layer (3) and the edge of the active material layer (213) is j mm, satisfying 1 mm ≤ j mm ≤ 15 mm.

14. The battery according to claim 12, characterized in that, Along the width direction of the first electrode (21), the end of the protective layer (3) is located between the edge of the active material layer (213) and the edge of the diaphragm (22).

15. The battery according to claim 12, characterized in that, Along the width direction of the first electrode (21), the width of the end of the protective layer (3) extending beyond the edge of the diaphragm (22) is k mm, satisfying 0.1 mm ≤ k mm ≤ 9.6 mm.

16. The battery according to any one of claims 1 to 8, characterized in that, The first electrode (21) also includes a straight portion (214) connected to the bent portion (211), the straight portion (214) is used to form the straight segment (24), the protective layer (3) extends to the straight portion (214) along the length direction of the first electrode (21), and the width of the protective layer (3) on the straight portion (214) is n mm, satisfying n mm≤15 mm.

17. The battery according to any one of claims 1 to 8, characterized in that, The protective layer (3) is provided on both opposite sides of the bent portion (211).

18. The battery according to any one of claims 1 to 8, characterized in that, The first electrode (21) is wound in several turns, and the protective layer (3) is provided within five turns near the starting end of the winding of the first electrode (21).

19. The battery according to any one of claims 1 to 8, characterized in that, The two bent sections (23) are arranged at relative intervals, and the straight section (24) is connected between the two bent sections (23). Both bent sections (23) are provided with the protective layer (3).

20. The battery according to any one of claims 1 to 8, characterized in that, The first electrode (21) is provided with the protective layer (3), and the first electrode (21) is a positive electrode.

21. The battery according to any one of claims 1 to 8, characterized in that, The protective layer (3) is provided on both the first electrode (21) and the second electrode.

22. The battery according to any one of claims 1 to 8, characterized in that, The outer casing (1) includes a first surface disposed opposite to the lead-out end of the tab portion (25) of the battery cell (2). The first surface is provided with a liquid injection hole (11). Along the width direction of the first electrode (21), the distance between the liquid injection hole (11) and the edge of the first electrode (21) is t mm, which satisfies 4 mm ≤ t mm ≤ 8.5 mm.

23. The battery according to claim 22, characterized in that, Along the extension direction of the straight section (24), the distance between the injection hole (11) and the edge of the protective layer (3) is u mm, which satisfies 50 mm ≤ u mm ≤ 110 mm.

24. The battery according to claim 1, characterized in that, The puncture resistance FN of the protective layer (3), the width L mm of the protective layer (3) along the length direction of the first electrode (21), the ratio m of the thickness of the active material layer (213) to the thickness of the first electrode (21), and the pore density P% of the isolation layer (31) in the central region (2111) satisfy 0.08≤L / (F×P×m)≤6.

45.

25. An electrical appliance, characterized in that, It includes at least two batteries as described in any one of claims 1 to 24.

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