Battery and electric device

Abstract

The invention discloses a battery and an electric device. The battery comprises an outer package, an electrode assembly and an electrolyte, the electrode assembly is arranged in the inner space of the outer package, and the electrolyte is filled in the inner space of the outer package; wherein the electrode assembly comprises a pole piece, the pole piece comprises a main body part and a plurality of convex parts, each convex part is formed by a part of the pole piece protruding towards one side of the main body part, and the center-to-center distance L between every two adjacent convex parts is larger than or equal to 0.5 mm and smaller than or equal to 4.0 mm; the viscosity of the electrolyte at 25 DEG C is eta, and 3.0 < = eta / L < = 7.0, so that the distance between two adjacent convex parts is matched with the viscosity of the electrolyte, the convex parts can provide enough support for the isolating membrane, the electrolyte can smoothly flow among the convex parts, better liquid storage is realized, the infiltration effect of the electrolyte is improved, local liquid shortage is prevented, and the service life of the isolating membrane is prolonged. And the transmission effect of ions between the pole piece and the diaphragm can be improved, the charge-discharge cycle performance of the battery can be improved, the adhesion between the pole piece and the diaphragm can be improved, and the overall interface consistency of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery and an electrical device. Background Art

[0002] The charge and discharge cycle life is a key performance of the battery. In addition to optimizing and innovating the battery's electrolyte and electrode materials to improve the charge and discharge cycle life, the charge and discharge cycle life can also be effectively improved through the structural design and improvement of the battery's electrode assemblies. This puts more requirements on the structural design of the electrode assemblies. Summary of the invention

[0003] The inventors found that there would be extrusion between the layers of the electrode assembly, especially during the battery charging and discharging process, the expansion and extrusion of the electrode assembly would be further aggravated, resulting in insufficient electrolyte between the layers of the electrode assembly, poor wetting, prone to interface deterioration, and even abnormal conditions such as poor wetting and cycle failure.

[0004] The embodiments of the present application provide a battery and an electrical device, which can improve the problem of poor electrolyte infiltration in the battery.

[0005] In the first aspect, an embodiment of the present application provides a battery, including an outer package, an electrode assembly and an electrolyte. The electrode assembly is arranged in the internal space of the outer package, and the electrolyte is filled in the internal space of the outer package. The electrode assembly includes a pole piece, and the pole piece includes a main body and a plurality of protrusions, and the protrusions are formed by protruding part of the pole piece to one side of the thickness direction of the main body, and the center distance between two adjacent protrusions is L (mm), 0.5≤L≤4.0, and the viscosity of the electrolyte at 25°C is η (mpa·s), 3.0≤η / L≤7.0.

[0006] In some embodiments, the battery satisfies at least one of the following conditions:

[0007] (1) 1.2 ≤ L ≤ 3.5;

[0008] (3)6≤η / L≤6.8;

[0009] (2)6.0≤η≤14.0.

[0010] In some embodiments, the protrusion height of the outer surface of the protrusion is H (mm), the diameter of the inscribed sphere of the inner surface of the protrusion is R (mm), 9.38≤L2 / (2HR-H 2 )≤79.75.

[0011] In some embodiments, the battery satisfies at least one of the following conditions:

[0012] (1) 0.05≤H≤0.08;

[0013] (2)0.3≤R≤2.0.

[0014] In some embodiments, the projection area of ​​the outer surface of the protrusion in the thickness direction of the pole piece is S (mm 2 ), the pole piece satisfies at least one of the following conditions:

[0015] (1) 0.16 ≤ S ≤ 2.0;

[0016] (2)12.5≤S / H≤33.3.

[0017] The unit of S / H is mm.

[0018] In some embodiments, the pole piece includes a current collector and an active material layer connected to the surface of the current collector. The tensile strength of the current collector is T (MPa), and the projection area of ​​the outer surface of the protrusion in the thickness direction of the pole piece is S (mm 2 ). The pole piece satisfies at least one of the following conditions:

[0019] (1)30≤T≤400;

[0020] (2)100≤T / S≤200.

[0021] The unit of T / S is MPa / mm 2 .

[0022] In some embodiments, a plurality of protrusions are arranged side by side and spaced apart along a first direction of the pole piece to form a group of protrusion units, and in a second direction of the pole piece, two adjacent groups of protrusion units are spaced apart. The first direction, the second direction, and the thickness direction of the pole piece are perpendicular to each other. The spacing between two adjacent protrusions in the first direction and the second direction both satisfy the range of L. The protrusions of two adjacent protrusion units are collinearly arranged in the second direction; or, one of the protrusion units is translated relative to the other protrusion unit in the first direction by a preset distance A, and A satisfies: 0.3L≤A≤L.

[0023] In some embodiments, in the thickness direction of the pole piece, all the protrusions are bent toward the same side of the main body; or,

[0024] In the thickness direction of the pole piece, a part of the protrusion is bent toward one side of the main body, and another part of the protrusion is bent toward the other side of the main body.

[0025] In some embodiments, the electrolyte includes a linear ester compound, and based on the total mass of the electrolyte, the weight percentage of the linear ester compound is W, and 40wt.%≤W≤60wt.%.

[0026] In some embodiments, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet; at least one of the positive electrode sheet and the negative electrode sheet is formed by the electrode sheet having a protrusion.

[0027] In a second aspect, an embodiment of the present application provides a battery, including an outer package and the above-mentioned electrode assembly, wherein the electrode assembly is disposed in an internal space of the outer package.

[0028] Based on the batteries and electrical devices of the embodiments of the present application, by selecting protrusions that satisfy the conditions 0.5≤L≤4.0, 3.0≤η / L≤7.0, the spacing between two adjacent protrusions and the viscosity of the electrolyte are matched, the protrusions can provide sufficient support for the isolation membrane, and the electrolyte can flow smoothly between the protrusions, thereby achieving better liquid storage, improving the wetting effect of the electrolyte, preventing local liquid shortage, and improving the transmission effect of ions between the electrode and the isolation membrane, thereby improving the charge and discharge cycle performance of the battery, and also improving the adhesion between the electrode and the diaphragm, thereby improving the overall interface consistency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a schematic diagram of the front view structure of a pole piece in an embodiment of the present application in an unfolded state;

[0031] Figure 2 This is a schematic cross-sectional structural diagram of an electrode assembly according to an embodiment of the present application;

[0032] Figure 3 This is a schematic diagram of a partial cross-sectional structure of a pole piece having a convex portion according to an embodiment of the present application;

[0033] Figure 4 This is a schematic diagram of the main structure of a pole piece having an end clearance area according to an embodiment of the present application;

[0034] Figure 5 This is a schematic diagram of the front view structure of a pole piece having a pole ear area according to an embodiment of the present application;

[0035] Figure 6 This is a schematic diagram of the main structure of a pole piece in which the pole ear area penetrates the pole piece in one embodiment of the present application.

[0036] Reference numerals:

[0037] 20. Electrode body; 21. Straight section; 22. Corner section; 100. Tab; 40. Tab assembly; 50. Isolation membrane;

[0038] 300, pole piece; 311, convex part; 3111, inner surface; 3112, outer surface; 312, main body part;

[0039] 410, positive electrode sheet; 420, negative electrode sheet;

[0040] 310, convex point area; 320, tab area; 321, tab installation area; 322, protective glue installation area; 330, end avoidance area; 3201, first side boundary; 3202, second side boundary; 3203, bottom boundary; 3204, third side boundary; 3205, fourth side boundary; 331, head avoidance area; 332, end avoidance area;

[0041] 3411, first edge; 3421, second edge; 3431, third edge; 3441, fourth edge;

[0042] 3101, first boundary; 3102, second boundary; 3103, third boundary; 3104, fourth boundary;

[0043] 341, first area; 342, second area;

[0044] X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0046] The inventors found that during the charge and discharge process of the battery, the electrode assembly expands and the extrusion between the electrode assembly layers will be further aggravated, resulting in insufficient electrolyte between the electrode assembly layers, poor infiltration, easy interface deterioration, and even cycle failure.

[0047] The inventors also found that in the process of processing the electrode assembly, the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound multiple times in sequence to form an electrode body with multiple winding units. By increasing the spacing between two adjacent winding units and providing a convex portion on the electrode sheet to support the two adjacent winding units, the extrusion problem caused by the expansion of the electrode assembly can be improved. However, the presence of the convex portion will also interfere with the flow of the electrolyte to a certain extent, thereby affecting the infiltration effect of the electrolyte. Based on this, the embodiment of the present application provides a battery and an electrical device, which designs the convex portion of the electrode sheet to effectively improve the electrolytic infiltration and electrode sheet interface problems.

[0048] The battery provided in the embodiment of the present application includes an outer package and an electrode assembly disposed in the inner space of the outer package, and an electrolyte filled in the inner space of the outer package. The electrode assembly includes two pole pieces with opposite polarities and a separator, such as Figure 1 As shown, it is a schematic diagram of the main structure of an electrode sheet 300 in an embodiment of the present application in an unfolded state. The electrode sheets 300 have length directions X, width directions Y and thickness directions Z that are perpendicular to each other. The length directions X, width directions Y and thickness directions Z of the two electrode sheets 300 of opposite polarities of the electrode assembly are consistent. The separator 50 is arranged between the two electrode sheets 300 of opposite polarities in the thickness direction Z of the electrode sheets 300. One of the two electrode sheets 300 of opposite polarities is a positive electrode sheet 410, and the other is a negative electrode sheet 420. The separator 50 has insulation properties and is used to separate the positive electrode sheet 410 from the negative electrode sheet 420 to prevent the positive electrode sheet 410 and the negative electrode sheet 420 from short-circuiting.

[0049] like Figure 2 As shown, the isolation film 50 and the two pole pieces 300 are wound multiple times along the length direction X of the pole piece 300 to form the electrode body 20, and the length direction X of the pole piece 300 is the direction in which the pole piece 300 is wound. The electrode body 20 is flat, and each circle of pole pieces 300 includes two straight sections 21 and two corner sections 22. The two straight sections 21 are arranged opposite to each other in a direction perpendicular to the plate surface of the straight section 21, and the two straight sections 21 are arranged between the two corner sections 22 in a direction parallel to the plate surface of the straight section 21. The two straight sections 21 and the two corner sections 22 are connected end to end in sequence. Among them, the corner sections 22 of two adjacent circles of pole pieces 300 are prone to mutual extrusion, and the straight sections 21 of two adjacent circles of pole pieces 300 are also mutually extruded, and there is also extrusion between the straight sections 21 and the corner sections 22 of the same circle of pole pieces 300. Therefore, these extruded parts are prone to insufficient electrolyte infiltration.

[0050] In the embodiment of the present application, the pole piece 300 includes a main body 312 and a plurality of convex portions 311, each convex portion 311 is formed by a portion of the pole piece 300 protruding toward one side of the main body 312, that is, each convex portion 311 protrudes in the thickness direction Z of the pole piece 300. The pole piece 300 includes a first surface perpendicular to the thickness direction Z of the pole piece 300, please refer to Figure 1The first surface includes a convex region 310, and a plurality of convex portions 311 are provided in the convex region 310, and there is a gap between the convex region 310 and the edge of the first surface. After the two pole pieces 300 and the isolation film 50 are wound multiple times to form the electrode body 20, the convex portion 311 contacts the isolation film 50 to provide support for the isolation film 50. When the electrode body 20 expands, the convex portion 311 can still support the isolation film 50. The contact area between the convex portion 311 and the isolation film 50 is small, so that there is space between the portion of the pole piece 300 corresponding to the convex region 310 and the isolation film 50 for accommodating electrolyte, thereby preventing abnormal situations such as insufficient electrolyte and poor wetting between the pole piece 300 and the isolation film 50 due to expansion and extrusion.

[0051] The straight section 21 and the corner section 22 both have convex portions 311, so that the isolation membrane 50 corresponding to the straight section 21 and the corner section 22 can be supported. Optionally, all the convex portions 311 provided on a single pole piece 300 protrude toward the same side of the pole piece 300 in the thickness direction Z of the pole piece 300, for example, the convex portion 311 provided on the straight section 21 protrudes toward the side of the winding center of the electrode body 20, and the convex portion 311 provided on the corner section 22 protrudes toward the side where the winding center of the electrode body 20 is located; or, the convex portion 311 provided on the straight section 21 protrudes toward the side away from the winding center of the electrode body 20, and the convex portion 311 provided on the corner section 22 protrudes toward the side away from the winding center of the electrode body 20. Optionally, a portion of the protrusions 311 provided on a single pole piece 300 protrudes toward one side of the pole piece 300 in the thickness direction Z of the pole piece 300, and another portion of the protrusions 311 protrudes toward the other side of the pole piece 300 in the thickness direction Z of the pole piece 300. For example, the protrusions 311 provided on the straight section 21 protrude toward one side of the winding center of the electrode body 20, and the protrusions 311 provided on the corner section 22 protrude toward the side away from the winding center of the electrode body 20; or, the protrusions 311 provided on the straight section 21 protrude toward the side away from the winding center of the electrode body 20, and the protrusions 311 provided on the corner section 22 protrude toward the side of the winding center of the electrode body 20.

[0052] The above is only an exemplary introduction. The present application does not limit the orientation of the protrusion 311 of each pole piece 300 , and the orientation can be selected according to actual needs.

[0053] In the embodiment of the present application, the viscosity of the electrolyte at 25°C is η, such as Figure 3As shown, the center distance between two adjacent protrusions 311 is L, 0.5≤L≤4.0, 3.0≤η / L≤7.0, for example, L can be 0.5mm, 0.8mm, 1.5mm, 2.0mm, 2.7mm, 3.2mm, 4.0mm or any range between the above two, and η / L can be 3.0, 3.5, 4.2, 4.6, 5.3, 6.2, 7.0 or any range between the above two. By selecting the range in which the convex portion 311 and the electrolyte satisfy the above conditional expression, the spacing between two adjacent convex portions 311 and the viscosity η of the electrolyte are matched, the convex portion 311 can provide sufficient support for the separator 50, the electrolyte can flow smoothly between the convex portions 311, achieve better liquid storage, improve the infiltration effect of the electrolyte, prevent local lack of liquid, and improve the transmission effect of ions between the pole piece 300 and the separator 50, improve the charge and discharge cycle performance of the battery, and also improve the bonding between the pole piece and the diaphragm, and improve the overall interface consistency of the battery. When L is higher than the upper limit of 4.0mm, the spacing between two adjacent convex portions 311 is too large, the supporting capacity of the convex portion 311 is insufficient, the improvement of the infiltration effect of the electrolyte is limited, and it is easy to cause the bonding between the pole piece and the diaphragm to deteriorate, the consistency of the interlayer interface is deteriorated, and it is also easy to cause the self-discharge performance of the battery to deteriorate. When L is lower than the lower limit of 0.5mm, the spacing between two adjacent convex portions 311 is too small, which is easy to cause the space between two adjacent convex portions 311 to be too small and the storage capacity is insufficient. When η / L is higher than the upper limit, the electrolyte viscosity is too high, the electrolyte is not easy to flow, the electrolyte infiltration effect is poor, resulting in poor battery charge and discharge cycle performance, and it is easy to cause purple spots or lithium precipitation in the battery during the cycle. When η / L is lower than the lower limit, the distance between two adjacent protrusions 311 is too large, the support capacity of the protrusion 311 is insufficient, and the effect of improving the battery charge and discharge cycle performance is poor.

[0054] In some embodiments, the electrolyte satisfies: 6.0≤η≤14.0, for example, η can be 6.0mpa·s, 8.5mpa·s, 9.8mpa·s, 10.2mpa·s, 11.5mpa·s, 14.0mpa·s or any range thereof. In the above viscosity range, the electrolyte can flow smoothly in the gap between the pole piece 300 and the separator 50, improve the infiltration effect of the electrolyte, and also improve the dynamic performance of the battery and the transmission efficiency of lithium ions.

[0055] In some embodiments, the electrolyte includes a linear ester compound, and the weight percentage of the linear ester compound is W based on the total mass of the electrolyte, 40wt.%≤W≤60wt.%, for example, W can be 40wt.%, 45wt.%, 48wt.%, 51wt.%, 55wt.%, 60wt.%, or any range of the above two. In the above content range, it is convenient to control the viscosity of the electrolyte within a suitable range, prevent the viscosity of the electrolyte from being too high to reduce the wetting effect of the electrolyte, and prevent the viscosity of the electrolyte from being too low, resulting in insufficient battery system dynamics and lithium precipitation during the cycle.

[0056] In some embodiments, the linear ester compound of the present application includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and methyl butyl carbonate.

[0057] like Figure 3 As shown, the convex portion 311 has an inner surface 3111 connected to one surface of the main body 312 and an outer surface 3112 connected to the other surface of the main body 312. The outer surface 3112 of the convex portion 311 has a vertex Q and a bottom edge m. The bottom edge m of the convex portion 311 is connected to the surface of the main body 312 of the pole piece 300. The convex portion 311 is convexly arranged on the main body 312 of the pole piece 300. The vertex Q of the convex portion 311 is the point of the convex portion 311 that is farthest from the bottom edge m in the thickness direction Z of the pole piece 300. The protrusion height H of the outer surface 3112 is the dimension from the vertex Q of the convex portion 311 to the bottom edge m of the convex portion 311 in the thickness direction Z of the pole piece 300. The convex portion 311 has a central axis K passing through the vertex Q and parallel to the thickness direction of the pole piece 300. The center spacing L of two adjacent convex portions 311 is the spacing between the central axes K of two adjacent convex portions 311 in the direction Z perpendicular to the thickness of the pole piece 300.

[0058] The top surface of the outer surface 3112 of the convex portion 311 in contact with the isolation membrane 50 is an arc surface, which prevents the top of the convex portion 311 from being too sharp and piercing the isolation membrane 50. The outer surface 3112 of the convex portion 311 is similar in shape to the inner surface 3111, and the top surface of the outer surface 3112 is an arc surface, and the part of the inner surface 3111 of the convex portion 311 corresponding to the top surface of the outer surface 3112 is also an arc surface, and the arc surface is in the inner ball D2, and the inner ball D1 and the inner ball D2 have the same spherical center, and the diameter of the inner ball D2 of the inner surface 3111 of the convex portion 311 is R.

[0059] Among them, 9.38≤L2 / (2HR-H 2 )≤105, for example, L 2 / (2HR-H 2) can be 9.38, 10.5, 15.0, 22.3, 55.0, 47.8, 86.3, 94.0, 79.75, 105.0 or any range of the above two. By selecting the range in which the protrusions 311 satisfy the above conditional expression, the distribution density of the protrusions 311 per unit area of ​​the pole piece 300 can be controlled to be appropriate, so that the pole piece 300 can flow smoothly between the protrusions 311, and better liquid storage can be achieved, the infiltration effect of the electrolyte can be improved, and the transmission effect of ions between the pole piece 300 and the isolation membrane 50 can be improved, and the height, spacing and sharpness of the protrusions 311 can be within a suitable range. The protrusions 311 can have good structural strength, are not easy to deform, provide more stable support for the isolation membrane 50, and are not easy to puncture the isolation membrane 50. It can also play a role in improving the ductility of the pole piece, so that the pole piece has suitable ductility. When L 2 / (2HR-H 2 ) is higher than the upper limit of 105.0, or when L 2 / (2HR-H 2 ) is higher than the upper limit of 79.75, the distribution density of the convex portion 311 is too sparse, the convexity of the convex portion 311 is insufficient, and the supporting force of the convex portion 311 is insufficient. It is also easy to cause the pole piece to extend and deteriorate in its XY direction (i.e., the length direction and the width direction) during the cycle, piercing the isolation film or the outer packaging structure. When L 2 / (2HR-H 2 ) is lower than the lower limit of 4.0, the distribution density of the protrusions 311 is too dense, which may easily lead to a small gap between the electrode 300 and the isolation membrane 50, thereby causing the electrolyte infiltration effect to deteriorate, and may also easily cause the battery to have dot-like purple spots or lithium deposition corresponding to the distribution of the protrusions during the cycle.

[0060] In some embodiments, the pole piece 300 satisfies: 0.05≤H≤0.08, and H can be 0.05mm, 0.06mm, 0.07mm, 0.08mm or any range of the above two. In the above spacing range, the gap between the pole piece 300 and the isolation membrane 50 is better, and the electrolyte infiltration effect is better. When H is higher than the upper limit of 0.08mm, the height of the protrusion 311 is too high, and the protrusion 311 is easy to deform. When H is lower than the lower limit of 0.02mm, the height of the protrusion 311 is too low, and the support capacity of the protrusion 311 for the isolation membrane 50 is insufficient. The spacing between the pole piece 300 and the isolation membrane 50 is too small, and the improvement of the electrolyte infiltration effect is poor.

[0061] In some embodiments, the pole piece 300 satisfies: 0.3≤R≤2.0, for example, R can be 0.3mm, 0.6mm, 0.9mm, 1.3mm, 1.5mm, 2.0mm or any range of the above two. In the above radius range, the pole piece 300 has a suitable protrusion degree to prevent the protrusion 311 from being easily deformed by external force, and the protrusion 311 has a good supporting structural strength, which is convenient for matching with the height H of the protrusion 311, so that the protrusion 311 occupies a suitable area of ​​the entire pole piece 300, and then within the unit area, the distribution density of the protrusion 311 is suitable, which can also play a role in storing residual electrolyte and improve the battery's liquid retention capacity.

[0062] In some embodiments, the projection area of ​​the outer surface 3112 of the protrusion 311 in the thickness direction Z of the pole piece 300 is S, wherein 0.16≤S≤2.0, for example, S may be 0.16 mm 2 , 0.18mm 2 , 0.20mm 2 , 0.80mm 2 , 1.22mm 2 , 1.64mm 2 , 2.00mm 2 By selecting the projection area of ​​the convex portion 311 to meet the above range, it is convenient to control the space occupied by the convex portion 311 to be appropriate, so that there is a suitable space between the isolation membrane 50 and the main body 312 of the pole piece 300 for accommodating the electrolyte, and it can also play the effect of strengthening the rigidity of the substrate and preventing the substrate from wrinkling and bending.

[0063] In some embodiments, 12.5≤S / H≤33.3, for example, S / H can be 12.5mm, 15.0mm, 23.5mm, 28.0mm, 33.3mm or any range of the above two. By selecting the ratio of the projection area S and the height H of the convex portion 311 within the above range, the convex portion 311 is relatively smooth, and the connection between the convex portion 311 and the main body 312 is prevented from being too steep, which causes the convex portion 311 to be easily deformed by external force, greatly improving the self-discharge performance of the battery, helping to improve the charge and discharge cycle performance of the battery, prolonging the service life, and reducing the stress concentration during the battery cycle, improving the expansion problem of the battery.

[0064] In some embodiments, the pole piece 300 includes a current collector and an active material layer connected to the surface of the current collector; the tensile strength of the current collector is T, 100≤T / S≤200, for example, T / S can be 100MPa / mm 2 、110MPa / mm 2 、120MPa / mm 2 、130MPa / mm 2、150MPa / mm 2 、180MPa / mm 2 、200MPa / mm 2 Or any range of the above two. By selecting the tensile strength T of the current collector and the projected area S of the convex portion 311 in a suitable range, the pole piece 300 is not easily deformed or damaged, and can maintain the shape of the convex portion 311 when subjected to a large force, thereby improving the self-discharge performance of the battery. At the same time, during the charge and discharge process, under the influence of the expansion force, the ductility of the pole piece 300 is appropriate, which can significantly improve the charge and discharge cycle performance of the battery, and can also prevent the pole piece from piercing the isolation membrane or piercing the outer packaging to cause the electrolyte to be exposed and safety risks.

[0065] In some embodiments, 30≤T≤400, which can prevent deformation or breakage due to insufficient strength during the manufacture and use of the pole piece 300, and also makes it easier to control the process during the manufacture of the pole piece 300, thereby reducing manufacturing defects while improving mechanical strength and electrochemical stability, improving the overall durability of the battery, and also improving production efficiency and reducing production costs.

[0066] In some embodiments, a plurality of protrusions 311 are arranged side by side and spaced apart along the first direction of the pole piece 300 to form a group of protrusion units. In the second direction of the pole piece 300, two adjacent groups of protrusion units are spaced apart. The first direction, the second direction, and the thickness direction Z of the pole piece 300 are perpendicular to each other. Optionally, the first direction is the length direction X of the pole piece 300, and the second direction is the width direction Y of the pole piece 300, or the first direction is the width direction Y of the pole piece 300, and the second direction is the length direction X of the pole piece 300. Figure 1 and Figure 4 As shown, the distance between two adjacent protrusions 311 in the first direction and the second direction both meets the range of L, where Figure 1 As shown, the convex portions 311 of two adjacent convex portion units are arranged collinearly in the second direction; or, as shown Figure 4 As shown, one of the convex units is translated relative to the other convex unit in the first direction by a preset distance A, and A satisfies: 0.3L≤A≤L. In the above arrangement, the convex portions 311 are arranged in an orderly manner, which is conducive to the infiltration of the electrolyte and the transfer of ions, and can provide uniform support force. During the charge and discharge process, it can provide good support stability and improve the charge and discharge cycle performance of the battery. The orderly arranged convex portions 311 can also reduce bubbles in the electrolyte, improve the uniformity of electrolyte transmission, and increase the conductivity of the electrode, thereby reducing the internal resistance of the battery.

[0067] In some embodiments, the number of active material layers of the pole piece 300 is one layer, and is disposed on one surface of the current collector along the thickness direction Z of the pole piece 300; or, the number of active material layers is two layers, and along the thickness direction Z of the pole piece 300, one active material layer is disposed on one surface of the current collector, and the other active material layer is disposed on the other surface of the current collector. Wherein, the thickness of the current collector is h1, 0.001≤h1≤0.200, and the thickness of the active material layer is h2, 0.010≤h2≤0.500. In the embodiment of the present application, the convex portion 311 is formed by a portion of the current collector and a portion of the active material layer. For example, the convex portion 311 of the embodiment of the present application can be processed by rolling. Specifically, the roller acts on a portion of the area of ​​the pole piece 300 on one side of the pole piece 300, and the current collector and the active material layer in the area are deformed and bent together, that is, the convex portion 311 is formed.

[0068] In some embodiments, the surface of the active material layer facing away from the current collector forms a first surface, the first surface includes a convex region 310, a convex portion 311 is provided in the convex region 310, the convex region 310 is defined by a convex boundary line, the convex portion 311 of the convex region 310 may be located in the inner area defined by the convex boundary line, and the convex portion 311 may also be inscribed in the convex boundary line. The first surface also includes an end avoidance region 330 and an edge avoidance region, the end avoidance region 330 is connected to the end of the convex region 310 in the length direction X of the pole piece 300 and extends to the edge of the pole piece 300, and the edge avoidance region is provided on one side of the convex region 310 in the width direction Y of the pole piece 300 and extends to the edge of the pole piece 300. The edge avoidance region and the end avoidance region 330 are not provided with a convex portion 311, and after the two pole pieces 300 and the isolation film 50 are wound, the surface of the pole piece 300 corresponding to the edge avoidance region and the end avoidance region 330 can be spaced from the isolation film 50.

[0069] The end avoidance region 330 is disposed at the end of the convex point region 310 in the length direction X of the pole piece 300 and extends to the edge of the pole piece 300, and the end avoidance region 330 also extends to the edge of the pole piece 300 in the width direction Y of the pole piece 300. Figure 4 As shown, the end space avoidance area 330 includes at least one of a head space avoidance area 331 and a tail space avoidance area 332. Preferably, the end space avoidance area 330 includes both the head space avoidance area 331 and the tail space avoidance area 332. In the length direction X of the pole piece 300, the head space avoidance area 331 is arranged at one end of the convex point area 310, and the tail space avoidance area 332 is arranged at the other end of the convex point area 310.

[0070] After the two pole pieces 300 and the isolation film 50 are wound, the head air avoidance area 331 can be located in the innermost turns of the electrode body 20, which is convenient for the winding of the electrode body 20 and helps to improve the structural stability of the central area of ​​the electrode body 20. The tail air avoidance area 332 can be located in the outermost turns of the electrode body 20. The tail air avoidance area 332 can serve as a buffer area between the protrusion 311 and the tail end of the electrode body 20, so that the portion of the pole piece 300 corresponding to the end air avoidance area 330 can more smoothly form a constraint on the inner layer structure of the electrode body 20, which helps to improve the packaging stability of the electrode body 20. Especially when the electrode body 20 has a tendency to expand, the tail air avoidance area 332 without the protrusion 311 is used for tailing, which can prevent the tail of the electrode body 20 from slipping due to expansion stress and improve the structural stability of the electrode body 20.

[0071] Specifically, the first surface of the pole piece 300 includes a first edge 3411 and a second edge 3421 that are relatively set in the length direction X of the pole piece 300, and the convex point boundary line of the convex point area 310 includes a first boundary 3101 and a second boundary 3102 that are relatively set in the length direction X of the pole piece 300, the first boundary 3101 corresponds to the first edge 3411, and the second boundary 3102 corresponds to the second edge 3421. The head space avoidance area 331 is formed between the first edge 3411 and the first boundary 3101, and the tail space avoidance area 332 is formed between the second edge 3421 and the second boundary 3102. One end of the isolation membrane 50 is flush with the head space avoidance area 331 or extends out of the head space avoidance area 331 to be sandwiched between two pole pieces 300 with opposite polarities. The pole piece 300 is wound along the length direction X of the pole piece 300 from the head space avoidance area 331 and the isolation membrane 50 to form a flat electrode body 20, that is, the head space avoidance area 331 is located in the inner circle of the electrode body 20, and the tail space avoidance area 332 is located in the outer circle of the electrode body 20. The other end of the isolation membrane 50 extends out of the tail space avoidance area 332 in the winding direction of the pole piece 300 to prevent the isolation membrane 50 from shrinking and causing the two pole pieces 300 with opposite polarities to short-circuit.

[0072] The first surface of the pole piece 300 has an edge avoidance area, which includes a first area 341 and a second area 342. In the width direction Y of the pole piece 300, the first area 341 is connected to one side of the convex area 310, and the second area 342 is connected to the other side of the convex area 310. The first area 341 extends to the edge of the pole piece 300 in a direction away from the second area 342, and the second area 342 extends to the edge of the pole piece 300 in a direction away from the first area 341. That is, the two opposite boundaries of the convex area 310 in the width direction Y of the pole piece 300 are respectively spaced from the corresponding edges of the pole piece 300, thereby preventing the deformation stress when the convex portion 311 is processed in the convex area 310 from causing abnormal deformation such as wavy edges or wrinkles on the edge of the pole piece 300.

[0073] Specifically, the pole piece 300 includes a third edge 3431 and a fourth edge 3441 that are relatively arranged in the width direction Y of the pole piece 300, and the convex point boundary line of the convex point area 310 includes a third boundary 3103 and a fourth boundary 3104 that are relatively arranged in the width direction Y of the pole piece 300, the third boundary 3103 corresponds to the third edge 3431, and the fourth boundary 3104 corresponds to the fourth edge 3441. The first area 341 is formed between the third boundary 3103 and the third edge 3431, and the second area 342 is formed between the fourth boundary 3104 and the fourth edge 3441, and the first area 341 and the second area 342 extend in the length direction X of the pole piece 300 to connect to the end avoidance area 330, that is, the extension line of the first boundary 3101, the extension line of the second boundary 3102, the third boundary 3103 and the first boundary 3104. The three edges 3431 define a first area 341, the extension line of the first boundary 3101, the extension line of the second boundary 3102, the fourth boundary 3104 and the fourth edge 3441 define a second area 342, the extension line of the first boundary 3101, the first edge 3411, the third edge 3431 and the fourth edge 3441 define a head avoidance area 331, the extension line of the second boundary 3102, the second edge 3421, the third edge 3431 and the fourth edge 3441 define a tail avoidance area 332, the convex point area 310 is located in the area defined by the first boundary 3101, the second boundary 3102, the third boundary 3103 and the fourth boundary 3104, and the convex portion 311 can be inscribed in at least one of the first boundary 3101, the second boundary 3102, the third boundary 3103 and the fourth boundary 3104.

[0074] Optionally, the first boundary 3101, the second boundary 3102, the first edge 3411 and the second edge 3421 are parallel to the width direction Y of the pole piece 300, and the third boundary 3103, the fourth boundary 3104, the third edge 3431 and the fourth edge 3441 are parallel to the length direction X of the pole piece 300. At this time, the head avoidance area 331 and the tail avoidance area 332 are each independently rectangular or square, and the first area 341 and the second area 342 are rectangular.

[0075] Optionally, one of the first region 341 and the second region 342 is used to mount the tab assembly 40 of the electrode assembly, such as Figure 4 As shown, exemplarily, the second region 342 is used to install the tab assembly 40 of the electrode assembly, and the convex region 310 is spaced apart from the tab assembly 40. At this time, the convex region 310 is defined by a first boundary 3101, a second boundary 3102, a third boundary 3103 and a fourth boundary 3104.

[0076] Alternatively, if Figure 5As shown, the first surface also includes a tab area 320 , which extends from the third boundary 3103 toward the side where the fourth boundary 3104 is located. The tab area 320 is used to install the tab assembly 40 of the electrode assembly, and the tab assembly 40 is spaced apart from the bump area 310 . Among them, when the pole lug assembly 40 is installed in the pole lug area 320, its processing method will affect the installation stability of the pole lug assembly 40, as well as the stability of the structure around the pole lug assembly 40, and further affect the stability of the interface of the pole piece 300. For example, when the pole lug assembly 40 is pressed and installed on the pole piece 300 by rolling, the pole lug assembly 40 is pressed together with the area with the protrusion 311, or the distance between the pole lug assembly 40 and the protrusion 311 is too close, which may cause deformation of the protrusion 311 and the existence of indentations. By planning the pole lug area 320 for installing the pole lug assembly 40, the installation of the pole lug assembly 40 is facilitated, the process difficulty is reduced, the installation stability of the pole lug assembly 40 is improved, and the interface stability near the pole lug assembly 40 is improved. The pole lug assembly 40 and the protrusion 311 can also be misaligned in the thickness direction Z of the pole piece 300. When the electrode assembly is applied to a battery, it helps to improve the energy density of the battery.

[0077] Each lug area 320 is used to set at least one lug assembly 40. For example, the lug assembly 40 includes a lug and a protective glue. The lug and the protective glue can be installed in the same lug area 320; or, the lug is installed in one of the lug areas 320, and the protective glue is installed in another lug area 320.

[0078] There are multiple tabs, some of which are installed on one of the pole pieces 300, and the other tabs are installed on the other pole piece 300, wherein the tabs installed on the positive pole piece 410 are positive tabs, and the tabs installed on the negative pole piece 420 are negative tabs. The tab area 320 includes a tab installation area, which is used to install the tabs of the electrode assembly.

[0079] Alternatively, if Figure 5 As shown, the tab region 320 extends from the fourth boundary 3104 along the width direction Y of the pole piece 300 to the side where the third boundary 3103 is located, and is spaced apart from the third boundary 3103; or, as shown in Figure 6, the tab region 320 extends from the fourth boundary 3104 along the width direction Y of the pole piece 300 through the convex point region 310.

[0080] The electrode sheet 300 includes a positive electrode sheet 410 and a negative electrode sheet 420. The embodiment of the present application has no special restrictions on the materials of the positive electrode sheet 410 and the negative electrode sheet 420. Various materials that can be used as the positive electrode sheet 410 and the negative electrode sheet 420 that are well known in the art are applicable to the present application.

[0081] For example, the negative electrode current collector may be at least one of copper foil, aluminum foil, nickel foil or carbon-based current collector; the thickness of the negative electrode current collector may be 1 μm to 200 μm. The negative electrode active material layer may be disposed on one surface or two opposite 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 may be coated only on a partial area of ​​the negative electrode current collector. For example, the thickness of the negative electrode active material layer may be 10 μm to 500 μm.

[0082] The negative electrode active material layer includes a negative electrode active material. For example, the negative electrode active material includes at least one of lithium metal, natural graphite, artificial graphite or silicon-based materials, and the silicon-based material includes at least one of silicon, silicon oxide, silicon carbon compound or silicon alloy. The negative electrode active material layer may also include a conductive agent and / or a binder. For example, the conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers or carbon nanowires; the binder in the negative electrode active material layer may include at least one of carboxymethyl cellulose CMC, polyacrylic acid, polyacrylic acid salt, polyacrylic acid ester, polyvinyl pyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.

[0083] In some exemplary embodiments, the positive electrode sheet 410 includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. Exemplarily, the positive electrode current collector may be made of aluminum foil, and of course, other positive electrode current collectors commonly used in the art may also be used, and the thickness of the positive electrode current collector may be 1 μm to 200 μm. The positive electrode active material layer may be disposed on one surface or two opposite surfaces of the positive electrode current collector. Further, in the thickness direction Z of the positive electrode sheet 410, the positive electrode active material layer may be coated only on a partial area of ​​the positive electrode current collector, and the thickness of the positive electrode active material layer may be 10 μm to 500 μm.

[0084] The positive electrode active material layer includes a positive electrode active material. For example, the positive electrode active material includes LiCoO2, LiNiO2, LiMn2O4, 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-zO2, 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. Exemplarily, the positive electrode active material may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide or lithium nickel manganese oxide, and the above positive electrode active materials may be doped and / or coated. The positive electrode active material layer also includes a binder and a conductive agent. Illustratively, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene; the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers.

[0085] The embodiments of the present application have no particular restrictions on the materials of the isolation film 50, the tabs and the protective adhesive. Various materials known in the art that can be used as the isolation film 50, the tabs and the protective adhesive are applicable to the present application.

[0086] Exemplarily, the separator 50 includes at least one of 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. In particular, polyethylene and polypropylene have a good effect on preventing short circuits and can improve the stability of the electrode assembly through the shutdown effect. The thickness of the separator 50 is in the range of about 3μm to 500μm. The positive and negative tabs are made of metal conductive materials.

[0087] The embodiments of the present application do not have any particular restrictions on the electrolyte. Various materials that can be used as electrolytes known in the art are applicable to the present application. The electrolyte includes lithium salts and non-aqueous organic solvents.

[0088] Illustratively, the lithium salt includes lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium nitrate, lithium methylsulfite.

[0089] Exemplarily, the non-aqueous organic solvent may also include at least one of a carboxylate compound, an ether compound or other organic solvent. The above-mentioned carbonate compound may include but is not limited to at least one of a chain carbonate compound and a cyclic carbonate compound. The above-mentioned chain carbonate compound may include but is not limited to at least one of dipropyl carbonate (DPC) or ethyl methyl carbonate (EMC). The above-mentioned cyclic carbonate compound may include but is not limited to at least one of butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The above-mentioned carboxylate 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 above-mentioned ether compound may include but is 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 above-mentioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate. The present application has no particular restrictions on the mass percentage of the non-aqueous organic solvent in the electrolyte, as long as the purpose of the present application can be achieved. For example, based on the total mass of the electrolyte, the mass percentage of the non-aqueous organic solvent is 10% to 70%.

[0090] The present application has no particular limitation on the packaging bag, and it may be any packaging bag known in the art, as long as it can achieve the purpose of the present application.

[0091] The present application does not particularly limit the type of battery, which may include any device that undergoes an electrochemical reaction. In the present application, the battery may include, but is not limited to: a lithium metal battery, a lithium ion battery (lithium ion battery), a lithium polymer battery or a lithium ion polymer battery (lithium ion polymer battery), etc.

[0092] The preparation process of the battery of the present application is well known to those skilled in the art, and the present application has no particular limitation. For example, it may include but is not limited to the following steps: stacking the positive electrode, the separator and the negative electrode in order, and winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a battery; or stacking the positive electrode, the separator and the negative electrode in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly of a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a battery. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the packaging bag as needed to prevent the pressure inside the battery from rising and overcharging and discharging.

[0093] The present application also provides an electric device, which includes the battery in any of the above embodiments. Therefore, the electric device provided by the present application has good performance.

[0094] The present application does not particularly limit the type of electrical device, and it can be any electrical device known in the prior art. In some embodiments, the electrical device may include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0095] The present application is further described below by taking the electrode assembly of a lithium-ion battery as an example and combining specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0096] The following methods are used to test the performance of lithium-ion batteries in various embodiments and comparative examples of the present application:

[0097] (1) 25℃ / 45℃ cycle test

[0098] In a 25℃ / 45℃ environment, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery design maximum voltage is 4.5V), and then charged at a constant voltage at the maximum voltage until the current is 0.02C, and then discharged at a constant current of 0.7C until the final voltage is 3.0V, and the discharge capacity of the first cycle is recorded. Repeat the above steps for 1000 charge and discharge cycles, and record the discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles.

[0099] 25° C. 1C charge / 0.7C discharge cycle capacity retention rate=(discharge capacity at the 1000th cycle / discharge capacity at the first cycle)×100%.

[0100] Cycle capacity retention rate of 45° C. 1C charge / 0.7C discharge=(discharge capacity of the 800th cycle / discharge capacity of the first cycle)×100%.

[0101] (2) Test method for tensile strength of current collector

[0102] Prepare the specimens according to the standards (such as ASTM D882, ISO 527), and obtain the current collector specimen size of 150mm long × 10mm wide, and the thickness is based on the actual thickness of the current collector. Prepare multiple specimens (at least 5), and place the specimens in the vertical direction each time (that is, the plate surface of the current collector is parallel to the vertical direction), clamp the upper and lower clamps of the universal material testing machine to the edge of the specimen, and clamp them relatively to the edge of the specimen along the length direction of the current collector. The clamping width of each side is 5mm, and ensure that the specimen is aligned in the clamp and there is no deviation. Adjust the clamping force of the clamp to ensure that the specimen does not slip or damage. Set the tensile speed to 50mm / min, select the tensile test mode, start the testing machine, apply tensile force, and record the force-displacement curve until the specimen breaks. Record the maximum tensile force, and take the average of the maximum tensile forces of multiple specimens, which is the tensile strength.

[0103] (3) Liquid retention test method

[0104] During the assembly process of lithium-ion batteries, after drying in a vacuum oven at 85°C for 12 hours to remove moisture, the weight of the dry battery before injection is calculated and recorded as w1; after the lithium-ion battery is obtained through vacuum packaging, standing, formation, capacity, degassing, trimming and other processes, the weight of the lithium-ion battery is calculated and recorded as w2.

[0105] Liquid retention amount = (w2-w1) / w1×100%.

[0106] (4) Wetting improvement effect test method

[0107] Cut the electrode into a standard size of 10mm×10mm to ensure that the surface of the electrode is clean and uncontaminated. Add 5μL of electrolyte to the surface of the electrode and observe the diffusion rate and wetting area of ​​the electrolyte. Use a contact angle meter to measure the contact angle of the electrolyte on the surface of the electrode. Evaluate the wettability of the electrode based on the diffusion rate and contact angle of the electrolyte. The faster the diffusion rate, the smaller the contact angle and the better the wettability.

[0108] Among them, the contact angle range is 15°~25°, the surface wetting effect is "good", and the contact angle range is 5°~15°, the surface wetting effect is "poor".

[0109] Example 1-1

[0110] (1) Preparation of positive electrode sheet

[0111] The positive electrode active material lithium cobalt oxide LiCoO2, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride PVDF are mixed in a mass ratio of 97.9:0.9:1.2, N-methylpyrrolidone NMP is added as a solvent, and stirred evenly under the action of a vacuum mixer to obtain a positive electrode sheet slurry with a solid content of 75wt%. The positive electrode sheet slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 9μm, and dried and cold pressed at 85°C to obtain a positive electrode sheet with a single-sided coating of a positive electrode material layer with a thickness of 95μm. After that, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of a positive electrode material layer. After cutting, a positive electrode sheet with a specification of 74mm×851mm is obtained for standby use, and the compaction density of the positive electrode material layer is 4.20g / cm 3 .

[0112] (2) Preparation of negative electrode sheet

[0113] The negative electrode active material artificial graphite, the binder styrene-butadiene rubber SBR, and the thickener sodium carboxymethyl cellulose CMC are mixed in a mass ratio of 97.4:1.4:1.2, and then deionized water is added as a solvent, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode sheet slurry with a solid content of 50wt%. The negative electrode sheet slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 10μm, and dried and cold pressed at 85°C to obtain a negative electrode sheet with a negative electrode sheet material layer coated on one side with a thickness of 130μm. After that, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a negative electrode sheet material layer coated on both sides. After cutting and welding the negative electrode nickel tabs, a negative electrode sheet with a specification of 76mm×867mm is obtained for standby use, and the compaction density of the negative electrode sheet material layer is 1.80g / cm 3 .

[0114] (3) Preparation of isolation membrane

[0115] A polyethylene (PE) porous membrane with a thickness of 5 μm was used.

[0116] (4) Preparation of electrolyte

[0117] 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) were mixed in a mass ratio of 1:1:2 to obtain a base solvent, and then lithium hexafluorophosphate (LiPF6) was dissolved in the above base solvent to obtain an electrolyte. Among them, based on the total mass of the electrolyte, the mass percentage of LiPF6 is 12.5%.

[0118] (5) Assembly of lithium-ion batteries

[0119] The positive electrode tab is installed in one of the second regions 342 of the positive electrode sheet 410 by rolling, the protective adhesive is attached to the second region 342 of the positive electrode sheet 410 , and the negative electrode tab is installed in the edge region of the negative electrode sheet 420 by rolling.

[0120] The positive electrode sheet 410 with the positive electrode tab, the separator 50, and the negative electrode sheet 420 with the negative electrode tab are stacked in order, so that the separator 50 is located between the positive electrode sheet 410 and the negative electrode sheet 420 to play a role of isolation, and then wound to obtain the electrode body 20. The electrode assembly is placed in an outer packaging aluminum plastic film, placed in a vacuum oven at 85°C for 12 hours to remove moisture, and then injected with electrolyte, and a lithium-ion battery is obtained through vacuum packaging, standing, formation, capacity, degassing, trimming and other processes.

[0121] In Example 1-1, the positive electrode sheet has a convex portion, and the convex portion is rolled out on the positive electrode sheet by rolling, and Figure 4 The electrode shown is used as the positive electrode, and the parameters of the lithium-ion battery are shown in Table I.

[0122] Table I

[0123]

[0124]

[0125] Comparative Example 1-1 is the same as Example 1-1 except that no convex portion is provided in the preparation of the positive electrode plate.

[0126] Examples 1-2 to 1-14 and Comparative Examples 1-1 to 1-4 are the same as Example 1-1, except that the center distance L between two adjacent protrusions and the viscosity η of the electrolyte at 25°C are adjusted as shown in Table 1 in the preparation of the positive electrode plate, wherein the viscosity η of the electrolyte at 25°C can be obtained by adjusting the proportions of the components in the base solvent.

[0127] The parameters of the lithium-ion batteries of Examples 1-1 to 1-14 and Comparative Examples 1-1 to 1-4 and the performance test results of the lithium-ion batteries are shown in Table 1.

[0128] Table 1

[0129]

[0130] Among them, the greater the number of charge and discharge cycles and the greater the liquid retention, the better the battery performance.

[0131] It can be seen from Examples 1-1 to 1-14 and Comparative Examples 1-1 to 1-4 in Table 1 that when the lithium-ion battery satisfies: 0.5mm≤L≤4.0mm, 3.0≤η / L≤7.0, the distance between two adjacent protrusions 311 and the viscosity η of the electrolyte can be matched, the protrusions 311 can provide sufficient support for the isolation membrane 50, and the electrolyte can flow smoothly between the protrusions 311 to achieve better liquid storage, improve the wetting effect of the electrolyte, prevent local liquid shortage, and improve the transmission effect of ions between the electrode 300 and the isolation membrane 50, thereby improving the charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C, and improving the liquid retention of the lithium-ion battery.

[0132] It can be seen from Examples 1-1 to 1-14 and Comparative Examples 1-1 to 1-4 in Table 1 that the electrolyte satisfies: 6.0 MPa·s≤η≤14.0 MPa·s, the electrolyte can flow smoothly in the gap between the electrode 300 and the isolation membrane 50, the wetting effect of the electrolyte is improved, and the lithium-ion battery has good charge and discharge cycle performance at 25°C and 45°C.

[0133] It can be seen from Examples 1-1 to 1-7 in Table 1 that when the lithium-ion battery satisfies: 9.38≤L2 / (2HR-H 2 )≤105, which has a better effect on improving the charge and discharge cycle performance of lithium-ion batteries at 25℃ and 45℃.

[0134] The parameters of the lithium-ion batteries of Examples 2-1 to 2-12 and the performance test results of the lithium-ion batteries are shown in Table 2.

[0135] Table 2

[0136]

[0137] It can be seen from Examples 2-1 to 2-3, 2-9 to 2-10 and 1-4 in Table 2 that when the pole piece 300 satisfies: 0.05mm≤H≤0.08mm, the height of the protrusion 311 is appropriate, which can support the isolation membrane 50, so that the gap between the pole piece 300 and the isolation membrane 50 is better, the infiltration effect of the electrolyte can be improved, and the charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C is good.

[0138] It can be seen from Examples 2-4 to 2-8, Examples 2-11 to 2-12 and Example 1-4 in Table 2 that when the pole piece 300 satisfies: 0.3mm≤R≤2.0mm, the protrusion degree of the pole piece 300 is appropriate to prevent the protrusion 311 from being easily deformed by external force, the protrusion 311 has good supporting structural strength, and can also better play the role of storing residual electrolyte and improve the electrolyte infiltration effect. The charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C is good.

[0139] The parameters of the lithium-ion batteries of Examples 3-1 to 3-8 and the performance test results of the lithium-ion batteries are shown in Table 3.

[0140] Table 3

[0141]

[0142]

[0143] It can be seen from Examples 3-1 to 3-4 and Example 1-4 in Table 3 that the projection area S of the outer surface 3112 of the protrusion 311 in the thickness direction Z of the pole piece 300 satisfies: 0.16 mm 2 ≤S≤2.0, the space occupied by the protrusion 311 is appropriate, so that there is a suitable space between the isolation membrane 50 and the main body 312 of the electrode 300 for accommodating the electrolyte, and it can also strengthen the rigidity of the substrate to prevent the substrate from wrinkling and bending. The lithium-ion battery has good charge and discharge cycle performance at 25°C and 45°C.

[0144] It can be seen from Examples 3-5 to 3-8 and 1-4 in Table 3 that the tensile strength T of the current collector satisfies: 100 MPa / mm 2 ≤T / S≤200MPa / mm 2 , 30MPa≤T≤400MPa, the pole piece 300 is not easily deformed or damaged, and can maintain the shape of the protrusion 311 when subjected to a large force, thereby improving the self-discharge performance of the battery. At the same time, during the charge and discharge process, affected by the expansion force, the ductility of the pole piece 300 is appropriate, so that the lithium-ion battery has good charge and discharge cycle performance at 25°C and 45°C.

[0145] The parameters of the lithium-ion batteries of Examples 4-1 to 4-6 and the performance test results of the lithium-ion batteries are shown in Table 4.

[0146] Table 4

[0147]

[0148] It can be seen from Examples 4-1 to 4-6 and Example 1-4 in Table 4 that the weight percentage of the linear ester compound is W, 40wt.%≤W≤60wt.%, and the electrolyte can flow smoothly in the gap between the electrode 300 and the isolation membrane 50, thereby improving the wetting effect of the electrolyte and making the lithium-ion battery have good charge and discharge cycle performance at 25°C and 45°C.

[0149] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or position relationship based on the orientation or position relationship shown in the drawings, it is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0150] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A battery, characterized in that: It comprises an outer package, an electrode assembly and an electrolyte, wherein the electrode assembly is arranged in the inner space of the outer package, and the electrolyte is filled in the inner space of the outer package; Wherein, the electrode assembly includes a pole piece, the pole piece includes a main body and a plurality of convex parts, the convex part is formed by part of the pole piece protruding toward one side of the thickness direction of the main body, and the center distance between two adjacent convex parts is L (mm), 0.5≤L≤4.0; The viscosity of the electrolyte at 25° C. is η (mpa·s), 3.0≤η / L≤7.

0.

2. The battery according to claim 1, characterized in that The battery satisfies at least one of the following conditions: (1)1.2≤L≤3.5； (3)6≤η / L≤6.8; (2)6.0≤η≤14.

0.

3. The battery according to claim 1, characterized in that The protrusion height of the outer surface of the protrusion is H (mm), the diameter of the inscribed sphere on the inner surface of the protrusion is R (mm), 9.38≤L2 / (2HR-H 2 )≤79.

75.

4. The battery according to claim 3, characterized in that The battery satisfies at least one of the following conditions: (1)0.05≤H≤0.08； (2)0.3≤R≤2.0。 5. The battery according to claim 3, characterized in that The projection area of ​​the outer surface of the protrusion in the thickness direction of the pole piece is S (mm 2 ), the pole piece satisfies at least one of the following conditions: (1)0.16≤S≤2.0； (2)12.5≤S / H≤33.

3.

6. The battery according to claim 1, characterized in that The pole piece includes a current collector and an active material layer connected to the surface of the current collector; the tensile strength of the current collector is T (MPa), and the projection area of ​​the outer surface of the protrusion in the thickness direction of the pole piece is S (mm 2 ); The pole piece satisfies at least one of the following conditions: (1)30≤T≤400； (2)100≤T / S≤200.

7. The battery according to claim 1, characterized in that A plurality of the convex portions are arranged side by side and spaced apart along a first direction of the pole piece to form a group of convex portion units. In a second direction of the pole piece, two adjacent groups of the convex portion units are spaced apart. The first direction, the second direction and the thickness direction of the pole piece are perpendicular to each other. The spacing between two adjacent convex portions in the first direction and the second direction both meet the range of L. Wherein, the convex parts of two adjacent convex part units are collinearly arranged in the second direction; or, One of the convex units is translated relative to the other convex unit in the first direction by a preset distance A, and A satisfies: 0.3L≤A≤L.

8. The battery according to claim 1, characterized in that In the thickness direction of the pole piece, all the protrusions are bent toward the same side of the main body; or, In the thickness direction of the pole piece, a portion of the protrusion is bent toward one side of the main body, and another portion of the protrusion is bent toward the other side of the main body.

9. The battery according to claim 1, characterized in that The electrolyte includes a linear ester compound. Based on the total mass of the electrolyte, the weight percentage of the linear ester compound is W, and 40wt.%≤W≤60wt.%.

10. The battery according to claim 1, characterized in that The electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet; At least one of the positive electrode sheet and the negative electrode sheet is the sheet having the convex portion.

11. An electrical device, characterized in that: include: shell; and The battery according to any one of claims 1 to 10, wherein the battery is arranged in the internal space of the shell.

Images