Secondary battery and electronic device

Abstract

A secondary battery, comprising an electrode assembly and a first bonding member, wherein the electrode assembly comprises a first separator, a positive electrode sheet, a second separator, and a negative electrode sheet that are sequentially arranged layer by layer and wound; the positive electrode sheet comprises a first single-sided blank section and a first double-sided blank section, the first single-sided blank section is located on the secondary outer ring of the electrode assembly, and the first double-sided blank section is located on the outermost ring of the electrode assembly; the first separator comprises a first separator layer, and the first separator layer is located between the first single-sided blank section and the first double-sided blank section; the negative electrode sheet comprises a first double-sided coating section, the first double-sided coating section and the first single-sided blank section are stacked in a first direction, and the first double-sided coating section is closer to the winding center of the electrode assembly relative to the first single-sided blank section; the second separator comprises a second separator layer, and the second separator layer is located between the first single-sided blank section and the first double-sided coating section; the first single-sided blank section is bonded and fixed to the first separator layer or the second separator layer by means of the first bonding member.

Description

Secondary battery and electronic device

[0001] The present application claims priority to the prior application No. 202410520703.0, filed on April 28, 2024, with the State Intellectual Property Office of China, and entitled "Secondary battery and electronic device", the content of the above prior application is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a secondary battery and an electronic device. BACKGROUND

[0003] After the secondary battery falls, the isolation film is prone to shrink. The common means to solve the shrinkage of the isolation film caused by falling in the industry at present are: 1) reducing the amount of electrolyte in the secondary battery, reducing the impact of free electrolyte on the isolation film, so as to inhibit the shrinkage of the isolation film. 2) using high-adhesion isolation film, which inhibits the shrinkage of the isolation film by improving the adhesion between the isolation film and the pole piece. 3) using multiple winding adhesives on the electrode assembly, that is, adhering from one side of the electrode assembly to the opposite side. The above three will affect the electrolyte wettability, and then affect the interface of the secondary battery in the later stage of the cycle.

[0004] CONTENT OF THE APPLICATION

[0005] The inventors of the present application have studied the shrinkage mechanism of the isolation film on this basis, and found that after the pole pieces and the isolation film are wound into a winding structure, the binding force of the inner layer isolation film is usually greater than that of the outer layer due to the interlayer force of the winding structure. Therefore, the shrinkage degree of the outermost isolation film is larger, and at this time, under the condition of shrinkage of the head of the outermost isolation film, the positive pole piece contacts the negative pole piece arranged opposite to it, and the pressure drop is large at the moment of contact, and more heat is generated to cause safety problems such as fire.

[0006] The purpose of the present application is to provide a secondary battery and an electronic device, which aims to improve the safety problems caused by the voltage drop failure of the shrinkage of the isolation film when the secondary battery falls.

[0007] According to a first aspect of the present application, a secondary battery is provided, which includes an electrode assembly and a first adhesive. The electrode assembly includes a first separator, a positive electrode sheet, a second separator, and a negative electrode sheet which are sequentially stacked and wound. The positive electrode sheet includes a first single-sided blank section and a first double-sided blank section. The first single-sided blank section is located at a secondary outermost circle of the electrode assembly, and the first double-sided blank section is located at a primary outermost circle of the electrode assembly. The first single-sided blank section and the first double-sided blank section are stacked in a first direction. The first separator includes a first layer of film. In the first direction, the first layer of film is located between the first single-sided blank section and the first double-sided blank section. The negative electrode sheet includes a first double-sided coating section. The first double-sided coating section is stacked in the first direction with the first single-sided blank section, and the first double-sided coating section is closer to a winding center of the electrode assembly than the first single-sided blank section. The first direction is a thickness direction of the electrode assembly. The second separator includes a second layer of film. The second layer of film is located between the first single-sided blank section and the first double-sided coating section. The first single-sided blank section is adhesively fixed to the first layer of film or the second layer of film by the first adhesive.

[0008] The secondary battery according to the present application has the same polarity positive electrode sheet at the primary outermost circle and the secondary outermost circle of the electrode assembly. Even if the separator located between the primary outermost circle and the secondary outermost circle shrinks, short circuit does not occur. In addition, the positive electrode sheet at the secondary outermost circle and the first layer of film or the second layer of film stacked with the positive electrode sheet are adhesively fixed as a whole structure by the first adhesive. Compared with the conventional end green adhesive binding the winding structure at the winding termination end, the presence of the first adhesive moves the constraint position forward, and the electrical parameters of the secondary battery do not change significantly. Therefore, the shrinkage of the inner first separator and the second separator can be directly limited, and the safety problem caused by the voltage drop failure due to the shrinkage of the separator during the drop of the secondary battery can be improved.

[0009] In one or more optional embodiments described above, the secondary battery includes a positive electrode tab and a negative electrode tab. The positive electrode tab is electrically connected to the positive electrode sheet, and the negative electrode tab is electrically connected to the negative electrode sheet. The positive electrode tab and the negative electrode tab protrude from the same side of the electrode assembly. The second layer of film includes a second layer of film body and a second overhanging portion. The second layer of film body and the first single-sided blank section are stacked in the first direction. In the second direction, the second overhanging portion extends from the second layer of film body and protrudes from a side edge of the first single-sided blank section close to the positive electrode tab. The second direction is perpendicular to the first direction. The first adhesive includes a first portion and a second portion. The first portion is adhesively fixed to the current collector surface of the first single-sided blank section. The second portion extends from the first portion outside the electrode assembly and bends in the direction of the positive electrode tab, and the second portion is adhesively fixed to the second overhanging portion.

[0010] The above technical solution has the advantage that the bonding area of the first bonding member is larger than if the first bonding member were arranged with its side edge not protruding from the first single-face blank section. Thus, when the secondary battery falls, more impact force acting on the first overhanging portion can be dispersed by the first bonding member to the first single-face blank section, so as to further improve the safety problem caused by voltage drop failure of the second layer film due to shrinkage when the secondary battery falls.

[0011] In one or more optional embodiments above, the secondary battery includes a packaging bag. The packaging bag includes a main body portion and a top sealing portion extending outward from one side of the main body portion. The main body portion is provided with an electrode assembly, and the positive and negative tabs both protrude from the top sealing portion. A virtual plane in which the top sealing portion is located and perpendicular to the first direction is taken as a boundary surface to divide the electrode assembly into a first half portion and a second half portion. The first bonding member is located in the first half portion. The main body portion includes a second main wall, and the second main wall is arranged opposite to the second half portion in the first direction. The secondary battery includes a second bonding member, and the second half portion is fixed to the second main wall by the second bonding member.

[0012] Thus, the second bonding member can fix the electrode assembly to the inner wall of the packaging bag to reduce the situation that the electrolyte leaks when the electrode assembly hits and breaks the seal of the sealing portion during falling, thereby improving the anti-falling performance of the secondary battery. In addition, the first half portion is not additionally provided with a bonding member based on the consideration of wettability, so that the first half portion away from the second bonding member has a larger shrinkage degree of the isolation film during falling due to the lack of limitation. Arranging the first bonding member at the next outer circle of the first half portion not only has a better effect of limiting the shrinkage of the isolation film, but also because the second portion has a certain area in the second direction, the line pressure of the first side surface is smaller during falling, which can further reduce the situation that the electrolyte leaks when the electrode assembly hits and breaks the seal of the sealing portion during falling.

[0013] In one or more optional embodiments above, the second isolation film includes a plurality of third layer films. Each third layer film includes a third layer film main body and a third overhanging portion. The third overhanging portion protrudes from the third layer film main body and protrudes from the side edge of the positive tab close to the positive tab in the second direction. The second portion is cut off at the positive tab or the negative tab and is fixed to the plurality of third overhanging portions located in the first half portion. In this way, part of the first isolation film and / or part of the second isolation film in the first half portion are fixed together by the second portion, which can limit the shrinkage of the first isolation film and the second isolation film as a whole, and further improve the situation that the isolation film in the first half portion slips between layers under the working condition of falling.

[0014] In one or more optional embodiments above, the main body portion includes a first side and a second side. The first side is connected with the first main wall of the top sealing portion, and the second side is connected with the second main wall. In the second direction, the first side is spaced apart from and opposite to the first half portion, and the second side is spaced apart from and opposite to the second half portion. In the second direction, an average distance between the first side and a side end surface of the negative electrode tab located in the first half portion is less than an average distance between the second side and a side end surface of the negative electrode tab located in the second half portion. The inventors analyzed that the first and second separation membranes located in the first half portion are more prone to shrinkage, and arranging the first adhesive member in the first half portion to constrain the first half portion can improve the situation that the outermost separation membrane of the secondary battery is prone to shrinkage, and reduce the assembly difficulty compared with the first adhesive member bypassing the positive and negative electrode tabs and being arranged in the first and second half portions.

[0015] In one or more optional embodiments above, 0.1≤S / W≤0.8, 4≤S≤8; wherein Smm is a distance between the tab adhesive of the positive electrode tab and the tab adhesive of the negative electrode tab in the third direction; Wmm is a width of the electrode assembly in the third direction; wherein the third direction, the second direction, and the first direction are perpendicular to each other.

[0016] In one or more optional embodiments above, the first adhesive member includes a first adhesive layer and a second adhesive layer arranged in a stack. The first adhesive layer is adhered and fixed to the current collector surface of the first single-face blank section and the second overhang portion, respectively. The second adhesive layer is configured to be adhered and fixed to the packaging bag of the secondary battery. In this way, the second layer of film can be bonded to the packaging bag by the first adhesive member to achieve separate fixed connection between the second layer of film and the packaging bag, thereby reducing the situation that the second layer of film moves or misplaces relative to the packaging bag, to further improve the safety problem caused by the voltage drop failure of the secondary battery due to the shrinkage of the second layer of film when the secondary battery falls.

[0017] In one or more optional embodiments above, the first double-face blank section has a first winding end tail away from the winding center of the electrode assembly. The secondary battery includes a third adhesive member, and the first winding end tail is adhered to the surface of the first double-face blank section away from the winding center of the electrode assembly by the third adhesive member. The advantages of such an arrangement are that, on the one hand, the third adhesive member can function to bind the electrode assembly; on the other hand, the third adhesive member can assist in maintaining the adhesive fixation between the first single-face blank section and the first or second layer of film, i.e., it can reduce the impact of the first winding end tail, the second winding end tail, and the third winding end tail being loosened in the fixed position due to the vibration conduction to the components at the first adhesive member.

[0018] In one or more optional embodiments above, the first separator film has a second winding end away from the winding center of the electrode assembly, and the second separator film has a third winding end away from the winding center of the electrode assembly. In the winding direction of the electrode assembly, the third winding end is beyond the first winding end, and the second winding end is beyond the third winding end. The third adhesive is a single-sided adhesive tape, which is adhered to the first winding end, the second winding end, the third winding end, and the surface of the first double-sided blank section away from the winding center of the electrode assembly, respectively. Thus, the constraint on the outermost separator film can be strengthened by the adhesive fixation, and the mechanical stress concentration between the stacked layers caused by the shrinkage of the outermost separator film can be further reduced.

[0019] According to a second aspect of the present application, an electronic device is provided, which includes the secondary battery as described above.

[0020] Additional aspects and advantages of the embodiments of the present application will be described in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following description and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference signs. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0022] FIG. 1 shows a structural schematic diagram of a secondary battery according to an embodiment of the present application;

[0023] FIG. 2 is a front view of the secondary battery shown in FIG. 1 without the folded sealing part;

[0024] FIG. 3 is a partial cross-sectional view along line A-A in FIG. 1;

[0025] FIG. 4 is a partial enlarged view of a in FIG. 3;

[0026] FIG. 5 is a top view of the secondary battery shown in FIG. 1 without the packaging bag;

[0027] FIG. 6 is a partial enlarged view of b in FIG. 4;

[0028] FIG. 7 is a partial cross-sectional view of another secondary battery according to an embodiment of the present application;

[0029] FIG. 8 is a top view of the secondary battery shown in FIG. 7 without the packaging bag;

[0030] FIG. 9 is a partial enlarged view of c in FIG. 8;

[0031] FIG. 10 is a partial enlarged view of d in FIG. 7;

[0032] Fig. 11 is a partial cross-sectional view of another secondary battery according to an embodiment of the present application;

[0033] Fig. 12 is a plan view of the secondary battery shown in Fig. 11, without the packaging bag assembled;

[0034] 10: packaging bag; 11: main body portion; 111: first main wall; 112: second main wall; 113: first side surface; 114: second side surface; 12: top seal portion;

[0035] 20: electrode assembly; 21: first separator; 211: first layer film; 210: second winding end; 22: positive electrode sheet; 221: double-sided coating section; 222: single-sided blank section; 2221: first single-sided blank section; 223: double-sided blank section; 2231: first double-sided blank section; 220: first winding end; 23: second separator; 231: first layer film; 230: third winding end; 24: negative electrode sheet; 241: first empty foil section; 242: single-sided coating section; 243: double-sided coating section; 2431: first double-sided coating section; 244: second empty foil section; 20a: first half; 20b: second half;

[0036] 31: positive electrode tab; 32: negative electrode tab;

[0037] 40: first adhesive member; 401: first portion; 402: second portion;

[0038] 50: second adhesive member; 60: third adhesive member;

[0039] T: first direction; H: second direction; W: third direction; Su: winding direction of the electrode assembly. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application.

[0041] Reference to "an embodiment" in this application means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another.

[0042] In the description of the present application, it should be noted that unless specifically stated and limited otherwise, the terms "mounting", "connecting", and the like should be interpreted broadly, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium; can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0043] The term "vertical" is used to describe the ideal state between two components. In the actual production or use state, there can be an approximate vertical state between the two components. For example, in combination with numerical description, vertical can refer to the included angle between two straight lines in the range of 90°±10°, vertical can also refer to the dihedral angle between two planes in the range of 90°±10°, and vertical can also refer to the included angle between a straight line and a plane in the range of 90°±10°. The two components described as "vertical" can not be absolute straight lines or planes, but can be approximately straight lines or planes, and as a whole, the overall extension direction is considered to be a "straight line" or a "plane".

[0044] The term "parallel" is used to describe the ideal state between two components. In the actual production or use state, there can be an approximate parallel state between the two components. For example, in combination with numerical description, parallel can refer to the included angle between two straight lines in the range of 180°±10°, parallel can also refer to the dihedral angle between two planes in the range of 180°±10°, and parallel can also refer to the included angle between a straight line and a plane in the range of 180°±10°. The two components described as "parallel" can not be absolute straight lines or planes, but can be approximately straight lines or planes, and as a whole, the overall extension direction is considered to be a "straight line" or a "plane".

[0045] The technical features involved in different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0046] Fig. 1 is a structural schematic diagram of a secondary battery according to an embodiment of the present application. First, referring to the example shown in Fig. 1, the secondary battery includes: a packaging bag 10; an electrode assembly 20 accommodated in the packaging bag 10; a positive electrode tab 31 having one end electrically connected to the electrode assembly 20; a negative electrode tab 32 having one end electrically connected to the electrode assembly 20; the other end of the positive electrode tab 31 and the other end of the negative electrode tab 32 both protrude from the same side of the packaging bag 10, and the part of the positive electrode tab 31 protruding out of the packaging bag 10 and the part of the negative electrode tab 32 protruding out of the packaging bag 10 can be electrically connected to an external device to realize the charging and discharging of the secondary battery.

[0047] In some embodiments, the secondary battery includes an electrolyte, the electrolyte is contained in the inner cavity of the packaging bag 10, and the electrode assembly is soaked in the electrolyte.

[0048] For convenience of description, a three-dimensional rectangular coordinate system is established with the thickness direction of the secondary battery as the first direction, the height direction of the secondary battery as the second direction, and the width direction of the secondary battery as the third direction, as shown in FIGS. 1-11.

[0049] In some embodiments, the first direction T is parallel to the direction in which the electrode tabs in the electrode assembly to be described below are stacked. In addition, the first direction T is also parallel to the direction in which the first side and the second side to be described below are oppositely arranged.

[0050] In some embodiments, the second direction H is also parallel to the direction in which the tab extends to be described below; in addition, the second direction H is also parallel to the direction in which the first side and the first half to be described below are oppositely arranged, and parallel to the direction in which the second side and the second half are oppositely arranged.

[0051] In some embodiments, the third direction W is parallel to the direction in which the positive tab and the negative tab to be described below are oppositely arranged.

[0052] For the packaging bag 10, please refer to FIG. 1 in combination with FIGS. 3, 7, and 11. In some embodiments, the packaging bag 10 includes a main body 11 and a plurality of sealing portions 12 (not shown in the figure). The main body 11 has a first main wall 111, a second main wall 112, and a peripheral wall (not shown in the figure) extending between the first main wall 111 and the second main wall 112 and surrounding the four sides of the first main wall 111 and the four sides of the second main wall 112, and the first main wall 111, the second main wall 112, and the peripheral wall define a receiving cavity for containing the electrode assembly 20. The plurality of sealing portions 12 are integrally connected to the four sides of the peripheral wall, respectively, thereby forming a closed container to package the electrode assembly 20.

[0053] The peripheral wall includes a first side 113 and a second side 114. The first side 113 and the second side 114 are both located on the same side of the main body 11, the first side 113 is located on one side of the second direction H of the main body 11 and is connected to the first main wall 111, and the second side 114 is connected to the second main wall 112.

[0054] The plurality of sealing portions 12 include a top sealing portion 121, which extends outward from one side of the second direction H of the main body 11 and can be configured to allow the positive tab 31 and the negative tab 32 to extend out; one side of the top sealing portion 121 along the first direction T is integrally connected to the first side 113, and the other side of the top sealing portion 121 along the first direction T is integrally connected to the second side 114.

[0055] In implementation, the packaging bag 10 includes a first bag body 101 (not shown) and a second bag body 102 (not shown). The first bag body 101 and the second bag body 102 are sealingly connected, and at least one of the first bag body 101 and the second bag body 102 can be made into a concave accommodating cavity by using a drawing tool such as a punch. For ease of description, the first bag body 101 is taken as an example to define the accommodating cavity, and the second bag body 102 is taken as an example to be flat. The first bag body 101 extends outward from the periphery of the accommodating cavity to form a plurality of connecting edges, and the plurality of connecting edges of the first bag body 101 and the periphery of the second bag body 102 can be connected by, but not limited to, fusion to form a plurality of aforementioned sealing portions 12 connected in sequence to seal the accommodating cavity, and the part enclosed therebetween is the aforementioned main body portion 11 to accommodate the electrode assembly 20. As shown in FIG. 3, the first bag body 101 includes a first side surface 113, and the second bag body 102 includes a second side surface 114.

[0056] One side of the first bag body 101 and one side of the second bag body 102 can be connected to each other. However, the present application is not limited thereto. For example, the first bag body 101 and the second bag body 102 can be manufactured separately to be separated from each other.

[0057] In some embodiments, the first bag body 101 and the second bag body 102 are both made of a packaging film. Specifically, the packaging film includes a first polymer layer (not shown), a metal layer (not shown), and a second polymer layer (not shown) arranged in sequence from inside to outside.

[0058] The first polymer layer melts at a preset temperature and has viscosity to facilitate packaging of the packaging bag 10. As an example, the first polymer layer can be made of polypropylene material, so that the first polymer layer is difficult to be dissolved or swollen by the electrolyte, thereby reducing the risk of corrosion of the metal layer stacked with the first polymer layer.

[0059] The metal layer is used to reduce the situation that water vapor penetrates into the inner cavity to exchange with the electrolyte. As an example, the metal layer can be made of aluminum material, which reacts with oxygen in the air to form a dense oxide film to block the penetration of water vapor into the inside of the packaging bag 10.

[0060] Of course, the material of the metal layer can be variously selected. For example, in other embodiments, the metal layer can be selected from one of steel, titanium, and alloys.

[0061] The second polymer layer can reduce the situation that air penetrates into the inner cavity of the packaging bag 10, and can improve the deformation ability of the packaging bag 10. As an example, the second polymer layer can be made of nylon material.

[0062] For example, in other embodiments, the packaging film can be made of only a single polymer layer such as polyethylene, polypropylene, acid anhydride modified polypropylene, etc.

[0063] It is to be understood that when the packaging bag 10 is made of a packaging film, the specific shape of the packaging bag 10 depends on the shape of the electrode assembly 20 due to the deformability of the packaging film, in other words, the shape of the packaging bag 10 can match the shape of the electrode assembly 20 accommodated therein.

[0064] For the electrode assembly 20, which can be accommodated in the accommodation cavity, includes a positive electrode tab 22, a negative electrode tab 24, a first separator film 21, and a second separator film 23. The number of the positive electrode tab 22, the negative electrode tab 24, the first separator film 21, and the second separator film 23 is one each and each is substantially in a strip structure in the unfolded state. A first separator film 21, a positive electrode tab 22, a second separator film 23, and a negative electrode tab 24 are sequentially stacked and wound to form a wound structure having a winding central axis.

[0065] The positive electrode tab 22 includes a positive electrode current collector (not shown) and a positive electrode active material layer (not shown) provided on at least one surface of the positive electrode current collector.

[0066] The positive electrode current collector is generally made of a material having high conductivity without causing chemical changes. As such a material, stainless steel, aluminum, nickel, calcined carbon, or aluminum or stainless steel on the surface of which is surface-treated with carbon, nickel, titanium, silver, or the like can be cited, but is not limited thereto. It is to be understood that the configuration of the positive electrode current collector is various, such as a film, a tab, a foil, a mesh, a porous body, a foam, or a nonwoven fabric.

[0067] The positive electrode current collector is configured to be electrically connected to one end of the positive electrode tab 31, and the other end of the positive electrode tab 31 protrudes from the top seal portion 121.

[0068] It is to be understood that the specific connection method between the positive electrode tab 31 and the positive electrode tab 22 is various, and it is only necessary to connect the positive electrode tab 31 and the positive electrode tab 22 together and achieve electrical conduction therebetween. For example, the positive electrode tab 31 can be fixed to the positive electrode current collector by welding, riveting, or conductive adhesive bonding.

[0069] In the case of a lithium secondary battery, the positive electrode active material layer includes a positive electrode active material, which can include, but is not limited to, a layered compound of lithium cobaltate, lithium nickelate, lithium nickel cobalt manganese phosphate, lithium nickel cobalt aluminum phosphate, lithium manganese phosphate, lithium nickel phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium iron phosphate, or the like; or a compound substituted with one or more transition metals; for example, lithium manganese oxide such as LiMnO4 (x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, or the like; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, or the like; a compound represented by the chemical formula LiNiMnO2 (M is one or more selected from the group consisting of Co, Al, Ti, Mg, Zr, Mo, and W); or the like. 1+x Mn 2-x O4 (x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, or the like; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, or the like; a compound represented by the chemical formula LiNiMnO2 (M is one or more selected from the group consisting of Co, Al, Ti, Mg, Zr, Mo, and W); or the like. 1-x M xNi-site type lithium nickel oxides represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 to 0.3); and those with the chemical formula LiMn 2-x M x Lithium-manganese composite oxides represented by O2 (M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which some Li is replaced by alkaline earth ions; disulfide compounds; Fe2(MoO4)3, etc.

[0070] The negative electrode 24 includes a negative electrode current collector (not shown) and a negative electrode active material layer (not shown) disposed on at least one surface of the negative electrode current collector.

[0071] Negative current collectors are typically made of materials that are conductive but do not cause chemical changes. Examples of such materials include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatments such as carbon, nickel, titanium, or silver, but are not limited to these. Understandably, the construction of negative current collectors is quite diverse, including membranes, sheets, foils, meshes, porous materials, foams, or nonwoven fabrics.

[0072] The negative current collector is configured to be electrically connected to one end of the negative electrode tab 32, and the other end of the negative electrode tab 32 protrudes from the top seal 121. The negative electrode tab 32 and the positive electrode tab 31 are spaced apart in the third direction W.

[0073] It is understandable that the connection between the negative tab 32 and the negative current collector is similar to the connection between the positive tab 31 and the positive current collector. Please refer to the connection method between the positive tab 31 and the positive current collector. It will not be elaborated here.

[0074] In the case of a lithium-ion secondary battery, the negative electrode active material layer may include a negative electrode active material, which may include, but is not limited to, carbon, such as non-graphitized carbon, graphite-based carbon, etc.; and metal complex oxides, such as Li. x Fe2O3 (0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Group 1, Group 2 and Group 3 of the periodic table, halogen; 0 < x < 1; 1 < y < 3; 1 < z < 8), etc.; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxide such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, etc.; conductive polymer such as polyacetylene, etc.; lithium cobalt nickel-based material, etc.

[0075] The first separator 21 and the second separator 23 can be made of a generally known polyolefin separator or an organic or inorganic composite layer formed on an olefin-based material, which insulates the electrodes between the positive electrode sheet 22 and the negative electrode sheet 24, but are not particularly limited thereto.

[0076] It is worth mentioning that the electrode assembly 20 in each embodiment of the present application should satisfy that the width of the second direction H of the first separator 21 and the second separator 23 should be greater than the width of the second direction H of the negative electrode sheet 24, and the width of the second direction H of the negative electrode sheet 24 should be greater than the width of the second direction H of the positive electrode sheet 22. Thus, the first separator 21 and the second separator 23 can provide an additional safety margin to reduce the situation of short circuit caused by the direct contact of the positive electrode sheet 22 and the negative electrode sheet 24, in addition, the area of the negative electrode sheet 24 exceeding the positive electrode sheet 22 along the second direction H can adjust the positive and negative electrode capacity, thereby improving the excessive lithium ions of the positive electrode sheet 22 during the charging process of the secondary battery, which cannot be completely embedded in the negative electrode active material, thereby causing lithium precipitation on the surface of the negative electrode sheet 24, which brings safety risks.

[0077] The positive electrode sheet 22 has at least two first flat portions (not shown in the figure) and a first curved portion (not shown in the figure) connected between each two first flat portions, that is, one end of the first curved portion is connected with one first flat portion, and the other end of the first curved portion is connected with another first flat portion, and the positive electrode sheet 22 is bent by the first curved portion to form a coiled strip structure.

[0078] As shown in FIG. 5, FIG. 8 or FIG. 12, in some embodiments, the positive electrode sheet 22 includes a plurality of double-sided coating sections 221, a single-sided blank section 222 and a double-sided blank section 223 connected in turn from the inside to the outside of the coiled structure. Among them, the plurality of double-sided coating sections 221 are located in the innermost circle of the electrode assembly 20, the single-sided blank section 222 is located in the second outermost circle of the electrode assembly 20, and the double-sided blank section 223 is located in the outermost circle of the electrode assembly 20.

[0079] It should be noted that the double-coated section 221 mentioned herein specifically refers to the part of the positive electrode sheet 22 in which the positive active material layer is provided on both surfaces of the positive current collector along the thickness direction thereof. The single-coated blank section 222 specifically refers to the part of the positive electrode sheet 22 in which the positive active material layer is provided only on the surface of the positive current collector facing the center of the winding structure. The double-coated blank section 223 specifically refers to the part of the positive electrode sheet 22 in which the positive active material layer is not provided on both surfaces of the positive current collector along the thickness direction thereof.

[0080] Optionally, a double-coated section 221 can include at most two first straight portions and at most two first curved portions. A single-coated blank section 222 can include at most two first straight portions and one first curved portion. A double-coated blank section 223 can include one first straight portion and at most two first curved portions.

[0081] The negative electrode sheet 24 has at least two second straight portions (not shown in the figure) and a second curved portion (not shown in the figure) connected between each two second straight portions, i.e., one end of the second curved portion is connected to one second straight portion, and the other end of the second curved portion is connected to another second straight portion, and the negative electrode sheet 24 is bent into a winding strip structure through the second curved portion.

[0082] As shown in FIGS. 5, 8 or 12, in some embodiments, the negative electrode sheet 24 includes, from inside to outside of the winding structure in the winding direction, a first blank foil section 241, a single-coated section 242, a plurality of double-coated sections 243, and a second blank foil section 244. Among them, the first blank foil section 241 is located in the innermost circle of the electrode assembly 20, the single-coated section 242 is located in the second innermost circle of the electrode assembly 20, the plurality of double-coated sections 243 are located in the inner circle of the electrode assembly 20, and the second blank foil section 244 is located in the outermost circle of the electrode assembly 20. In the first direction T, the first blank foil section 241 and the single-coated section 242 are arranged opposite to the part of the double-coated section 221; the remaining part of the double-coated section 221 and the single-coated blank section 222 are arranged opposite to the double-coated section 243.

[0083] It should be noted that the first blank foil section 241 and the second blank foil section 244 mentioned herein specifically refer to the part of the negative electrode sheet 24 in which the negative active material layer is not provided on both surfaces of the negative current collector along the thickness direction thereof. The single-coated section 242 specifically refers to the part of the negative electrode sheet 24 in which the negative active material layer is provided only on the surface of the negative current collector away from the center of the winding structure. The double-coated section 243 specifically refers to the part of the negative electrode sheet 24 in which the negative active material layer is provided on both surfaces of the negative current collector along the thickness direction thereof.

[0084] Optionally, the first empty foil section 241 can include a second flat portion. The single-coated foil section 242 can include at most two second flat portions and at most two second curved portions. The double-coated foil section 243 can include at most two second flat portions and at most two second curved portions. The second empty foil section 244 can include a partial second flat portion.

[0085] Referring to FIG. 4, FIG. 6, or FIG. 9, in some embodiments, a portion of the double-coated foil section 243 is defined as a first double-coated foil section 2431, which can be a second flat portion as shown in FIG. 6 or FIG. 9.

[0086] A portion of the single-coated empty section 222 is defined as a first single-coated empty section 2221, which can be a first flat portion as shown in FIG. 6 or FIG. 9. In the first direction T, the first single-coated empty section 2221 is stacked with the first double-coated foil section 2431.

[0087] A portion of the second separation film 23 is defined as a second layer film 231, which is between the first single-coated empty section 2221 and the first double-coated foil section 2431. It should be noted that the second layer film 231 does not refer to a certain formation layer in the second separation film 23, but refers to a portion of the second separation film 23 in a certain layer.

[0088] A portion of the double-coated empty section 223 is defined as a first double-coated empty section 2231, which can be a first flat portion as shown in FIG. 6 or FIG. 9. In the first direction T, the first double-coated empty section 2231 is stacked with the first single-coated empty section 2221.

[0089] A portion of the first separation film 21 is defined as a first layer film 211, which is between the first single-coated empty section 2221 and the first double-coated empty section 2231. It should be noted that the first layer film 211 does not refer to a certain formation layer in the first separation film 21, but refers to a portion of the first separation film 21 in a certain layer.

[0090] The secondary battery includes a first adhesive 40, and the first single-coated empty section 2221 is adhered and fixed to the first layer film 211 or the second layer film 231 through the first adhesive 40.

[0091] The secondary battery relates to the outermost and the next outermost of the electrode assembly 20 are both positive electrode sheets 22 of the same polarity, so that even if the separator between the outermost and the next outermost shrinks, short circuit does not occur. In addition, the positive electrode sheet 22 of the next outermost and the first layer film 211 or the second layer film 231 laminated therewith are bonded and fixed as a whole by the first adhesive 40. Compared with the conventional green tape at the end of winding, the presence of the first adhesive 40 makes the constraint position forward, and the electrical parameters of the secondary battery do not change significantly, so that the shrinkage of the inner first separator 21 and the second separator 23 can be more directly limited, thereby improving the safety problem of voltage drop failure caused by the shrinkage of the separator when the secondary battery falls.

[0092] In some embodiments, the second layer film 231 includes a second layer film body (not shown) and a second overhanging portion (not shown). The second layer film body and the first single-sided blank section 2221 are laminated in the first direction T. Along the second direction H, the second overhanging portion extends from the second layer film body and protrudes from the first single-sided blank section 2221 to the side edge close to the positive tab 31 or the negative tab 32.

[0093] As shown in FIG. 4, the cross section of the first adhesive 40 is generally inverted L-shaped, which includes a first part 401 and a second part 402 extending from the first part 401 outside the electrode assembly 20 and bending towards the positive tab 31 or the negative tab 32. The first part 401 is bonded and fixed to the current collector surface of the first single-sided blank section 2221, and the second part 402 is bonded and fixed to the second overhanging portion.

[0094] The benefits of the above technical solution are that the bonding area of the first adhesive 40 is larger than that when the first adhesive 40 is not protruding from the side edge of the first single-sided blank section 2221. Therefore, when the secondary battery falls, more impact force acting on the first overhanging portion can be dispersed to the first single-sided blank section 2221 by the first adhesive 40, so as to further improve the safety problem of voltage drop failure caused by the easy shrinkage of the second layer film 231 when the secondary battery falls.

[0095] Alternatively, as shown in FIG. 7, in other embodiments, the first layer film 211 includes a first layer film body and a first overhanging portion. The first layer film body and the first single-sided blank section 2221 are laminated in the first direction T. Along the second direction H, the first overhanging portion extends from the first layer film body and protrudes from the first single-sided blank section 2221 to the side edge close to the positive tab 31. The cross section of the first adhesive 40 is generally I-shaped, which is bonded and fixed to the current collector surface of the first layer film body and the first single-sided blank section 2221, respectively.

[0096] Alternatively, in other embodiments, different from the foregoing embodiments, the first adhesive 40 is still substantially inverted-L-shaped in cross section, but the second portion 402 thereof faces in the opposite direction from the second portion 402 of the first adhesive 40 in the foregoing embodiments. That is, the first portion 401 is adhesively fixed to the current collector surface of the first single-face blank section 2221, and the second portion 402 is adhesively fixed to the first overhang.

[0097] For the first adhesive 40, in some embodiments, the first adhesive 40 includes a first adhesive layer (not shown) and a second adhesive layer (not shown) arranged in layers. The first adhesive layer is adhesively fixed to the current collector surface of the first single-face blank section 2221 and the second overhang, respectively. The second adhesive layer is configured to be adhesively fixed to the packaging bag 10.

[0098] Specifically, the first adhesive layer of the first portion 401 is adhesively fixed to the current collector surface of the first single-face blank section 2221, and the first adhesive layer of the second portion 402 is adhesively fixed to the second overhang. The second adhesive layer of the first portion 401 is adhesively fixed to the first layer film body, and the second adhesive layer of the second portion 402 is adhesively fixed to the first side surface 113. Of course, in other embodiments, the second adhesive layer of the first portion 401 need not be provided, and only the second adhesive layer of the second portion 402 is retained.

[0099] Thus, the second layer film 231 can be bonded to the packaging bag 10 by the first adhesive 40 to achieve separate fixed connection between the second layer film 231 and the packaging bag 10, thereby reducing the occurrence of the second layer film 231 moving or misaligning relative to the packaging bag 10, so as to further improve the safety problem caused by the voltage drop failure of the second layer film 231 shrinking when the secondary battery falls.

[0100] The first adhesive layer can be selected from at least one of a temperature-sensitive adhesive or a pressure-sensitive adhesive having initial adhesion.

[0101] The temperature-sensitive adhesive can be selected from at least one of a terpene resin, a petroleum resin, a naphthenic oil, a polyolefin, a polyvinyl butyral, a polyamide, an ethylene-vinyl acetate copolymer, a styrene-isoprene-styrene block copolymer, and a polyester, wherein the naphthenic oil cannot be used alone; the polyolefin can be selected from at least one of polypropylene, polybutene, polyisoprene, and polystyrene; the polyamide can be selected from at least one of polyacrylamide, polycaprolactam, and epoxy polyamide; and the polyester can be selected from at least one of thermoplastic polyurethane, nitrile rubber-phenol formaldehyde resin, and ethylene-phenol formaldehyde resin.

[0102] The pressure-sensitive adhesive with initial tack can be selected from at least one of acrylic resin adhesive, thermosetting polyurethane adhesive, silicone adhesive, natural rubber, synthetic rubber. The pressure-sensitive adhesive with initial tack refers to the pressure-sensitive adhesive that can produce adhesion to an object when the object and the pressure-sensitive adhesive are briefly contacted under finger pressure at room temperature (25°C).

[0103] The second adhesive layer can be selected from a pressure-sensitive adhesive without initial tack or a composite material of a pressure-sensitive adhesive without initial tack and a temperature-sensitive adhesive without adhesion at room temperature (25°C).

[0104] The pressure-sensitive adhesive without initial tack can be selected from at least one of ethylene-butylene-polystyrene linear triblock copolymer, styrene-butadiene block copolymer, epoxidized styrene-isoprene-styrene block copolymer. The temperature-sensitive adhesive without adhesion at room temperature can be selected from at least one of polyolefin, polyvinyl butyral, polyamide, ethylene-vinyl acetate copolymer, styrene-isoprene-styrene block copolymer, polyester; wherein the polyolefin can be selected from at least one of polypropylene, polybutylene, polyisoprene, polystyrene; the polyamide can be selected from at least one of polyacrylamide, polycaprolactam, epoxy polyamide; the polyester can be selected from at least one of thermoplastic polyurethane, nitrile rubber-phenolic resin, ethylene-phenolic resin.

[0105] The pressure-sensitive adhesive without initial tack refers to the pressure-sensitive adhesive that does not produce adhesion to an object when the object and the pressure-sensitive adhesive are briefly contacted under finger pressure at room temperature.

[0106] As an example, the first adhesive member 40 is a double-sided adhesive tape including a substrate. The substrate is sandwiched between the first adhesive layer and the second adhesive layer. The substrate can be selected from at least one of polyethylene terephthalate, oriented polyolefin, polyimide. The oriented polyolefin can be selected from at least one of oriented polyethylene, oriented polypropylene, oriented polybutylene, oriented polyethylene-propylene copolymer, oriented polystyrene.

[0107] Alternatively, in other embodiments, the first adhesive member 40 can also be a single-sided adhesive tape. In this case, the first adhesive member 40 includes the aforementioned substrate and the aforementioned first adhesive layer provided on one surface of the substrate. Specifically, the first adhesive layer of the first portion 401 is adhesively fixed to the current collector surface of the first single-sided blank section 2221, and the first adhesive layer of the second portion 402 is adhesively fixed to the second overhanging portion.

[0108] It can be understood that the shape of the first adhesive member 40 can be various. For example, the first adhesive member 40 can be rectangular, circular, diamond-shaped, triangular, ring-shaped, hui-shaped, porous, etc.

[0109] In some embodiments, the first adhesive member can have a width in the third direction W of 8 mm to 100 mm.

[0110] In some embodiments, the first portion 401 can have a pitch in the second direction H that is equal to the sum of the pitch of the second portion 402 in the first direction T and 8 mm to 100 mm, wherein the pitch of the second portion 402 in the first direction T can be 0 mm to 10 mm.

[0111] In some embodiments, the first portion 401 can have a thickness in the first direction T of 1 μm to 100 μm, and the second portion 402 can have a thickness in the second direction H of 1 μm to 100 μm.

[0112] In some embodiments, the first adhesive member can have a bonding force to the current collector surface of the first single-sided blank section 2221 under a unit size of greater than or equal to 0.05 N / mm.

[0113] Please refer to FIGS. 4, 7, or 11 in combination with FIGS. 5, 8, or 12, in some further embodiments, the electrode assembly 20 is divided into a first half 20a and a second half 20b by a virtual plane in which the top seal portion 121 is located and which is perpendicular to the first direction T. Along the first direction T, the first half 20a is oppositely disposed to the first main wall 111; along the second direction H, the first half 20a is spaced apart from and oppositely disposed to the first side surface 113. Along the first direction T, the second half 20b is oppositely disposed to the second main wall 112; along the second direction H, the second half 20b is spaced apart from and oppositely disposed to the second side surface 114. The first adhesive member 40 is located in the first half 20a.

[0114] The secondary battery includes a second adhesive member 50, and the second half 20b is fixedly adhered to the second main wall 112 by the second adhesive member 50.

[0115] The second adhesive member 50 can thus fix the electrode assembly 20 to the inner wall of the packaging bag 10 to reduce the occurrence of the electrolyte leakage of the electrode assembly 20 when the electrode assembly 20 hits the seal portion 12 to open the seal, thereby improving the drop resistance of the secondary battery. In addition, the first half 20a is not additionally provided with an adhesive member based on the consideration of wettability, so that the first half 20a away from the second adhesive member 50 has a larger shrinkage of the separator when dropping due to the lack of restriction. Arranging the first adhesive member 40 at the outer periphery of the first half 20a not only has a better effect of restricting the shrinkage of the separator, but also, because the second portion 402 has a certain area in the second direction H, the first side surface 113 has a smaller line pressure of the positive and negative electrode plates 24 when dropping, which can further reduce the occurrence of the electrolyte leakage of the electrode assembly 20 when the electrode assembly 20 hits the seal portion 12 to open the seal.

[0116] As an example, the second adhesive 50 can be a double-sided adhesive tape. It can be understood that the double-sided adhesive tape can be, but is not limited to, a common rubber-based, hot-melt type of glue or adhesive tape, etc. having double-sided adhesion, which can be, but is not limited to, a single polymer or a mixture of polymers.

[0117] In some embodiments, a portion of the second isolation film 23 is defined as a third layer film (not shown in the figure), and the number of the third layer films is multiple, each of which includes a third layer film body (not shown in the figure) and a third overhang (not shown in the figure). The third layer film body is located between the double-sided coating section 221 and the double-sided coating section 243. Along the second direction H, the third overhang extends from the third layer film body and protrudes from the side edge of the positive electrode sheet 22 close to the positive electrode tab 31.

[0118] A portion of the first isolation film 21 is defined as a fourth layer film (not shown in the figure), and the number of the fourth layer films is multiple, each of which includes a fourth layer film body (not shown in the figure) and a fourth overhang (not shown in the figure). The fourth layer film body is located between the double-sided coating section 221 and the double-sided coating section 243. Along the second direction H, the fourth overhang extends from the fourth layer film body and protrudes from the side edge of the positive electrode sheet 22 close to the positive electrode tab 31.

[0119] As shown in FIGS. 11-12, the second portion 402 extends and stops at the positive electrode tab 31 or the negative electrode tab 32 from the first portion 401 extending out of the electrode assembly 20 towards the direction of the positive electrode tab 31. The second portion 402 is adhered and fixed with the multiple third overhangs and / or the multiple fourth overhangs located in the first half 20a. In this way, the partial first isolation film 21 and / or the partial second isolation film 23 in the first half 20a are adhered and fixed together by the second portion 402, which can limit the shrinkage of the first isolation film 21 and the second isolation film 23 as a whole, and further improve the occurrence of interlayer slippage of the isolation film in the first half 20a under the working conditions such as falling.

[0120] Optionally, along the second direction H, the average distance between the first side surface 113 and the side end surface of the negative electrode sheet 24 located in the first half 20a is smaller than the average distance between the second side surface 114 and the side end surface of the negative electrode sheet 24 located in the second half 20b.

[0121] It should be noted that the reason why the average distance between the first side surface 113 and the side end surface of the negative tab 24 located at the first half 20a is smaller than the average distance between the second side surface 114 and the side end surface of the negative tab 24 located at the second half 20b is that the second bag body 102 is preformed into the concave accommodating cavity by using a drawbench or the like, and the size of the accommodating cavity inevitably has assembly tolerance with the electrode assembly 20 due to the machining precision of the machine; while the first bag body 101 plastically extends with the part of the electrode assembly 20 protruding from the accommodating cavity into a shape matching the part of the electrode assembly 20 protruding from the accommodating cavity, that is, the accommodating cavity of the first bag body 101 has no assembly tolerance with the electrode assembly 20, so the first bag body 101 is forced to plastically extend between the peripheral side surface of the electrode assembly 20 and the part of the electrode assembly 20 protruding from the accommodating cavity of the second bag body 102, and has a smaller average distance.

[0122] The inventor analyzes that the first separation film 21 and the second separation film 23 located at the first half 20a are more likely to shrink after drop simulation, and arranging the first adhesive 40 at the first half 20a to constrain the first half 20a can not only improve the situation that the outermost separation film of the secondary battery is easy to shrink, but also reduce the assembly difficulty compared with arranging the first adhesive 40 around the positive and negative tabs 32 and arranging the first adhesive 40 at the first half 20a and the second half 20b.

[0123] It should be noted that the average distance between the first side surface and the side end surface of the negative tab located at the first half and the average distance between the second side surface and the side end surface of the negative tab located at the second half mentioned here can be obtained according to the following test method.

[0124] Firstly, the secondary battery is transferred into the cavity of the X-ray computed tomography (X-Ray CT, model: GE Phoenix m300) equipped with the device, and the battery is scanned. Then, the image after scanning of the battery is calculated and synthesized by using the software matched with the device. The processed image can be used to cut any cross section of the battery, and the synthesized X-ray CT cross section image is obtained;

[0125] It should be noted that in the process of selecting the cross section image, the area containing the tab at the outermost side of the battery should be avoided in the cut image. The brightness of the cut image should be adjusted until the outline of the packaging bag and the current collector of the negative tab can be distinguished.

[0126] Then, a plurality of different measurement points are selected on the first side surface in the direction from the first main wall to the top sealing part, and all the sizes between the measurement points and the side end surface of the negative tab located at the first half are obtained. The average distance between the first side surface and the side end surface of the negative tab located at the first half is obtained by dividing the sum of all the sizes by the number of measurement points.

[0127] For example, the measurement of one of the measuring points, along the second direction, the line segment from the measuring point to the side end face of the negative tab located in the first half is measured using a digital ruler, and then a proportional conversion is performed to obtain the size between the measuring point and the side end face of the negative tab located in the first half.

[0128] Similarly, along the direction from the second main wall to the top sealing portion, a plurality of different measuring points are selected on the second side face, and a plurality of sizes between the measuring points and the side end face of the negative tab located in the second half are obtained. The average distance between the second side face and the side end face of the negative tab located in the second half is obtained by dividing the sum of all sizes by the number of measuring points.

[0129] For example, the measurement of one of the measuring points, along the second direction, the line segment from the measuring point to the side end face of the negative tab located in the second half is measured using a digital ruler, and then a proportional conversion is performed to obtain the size between the measuring point and the side end face of the negative tab located in the second half.

[0130] As shown in FIG. 2, in some optional embodiments, 0.1≤S / W≤0.8, 4≤S≤8; wherein S is the distance between the tab adhesive of the positive tab 31 and the tab adhesive of the negative tab 32 along the third direction W; and W is the width of the electrode assembly 20 along the third direction W. For example, the value of S / W can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or a range formed by any two of the above values. The value of S can be 4, 5, 6, 7, 8, or a range formed by any two of the above values. The electrode assembly 20 satisfies this condition, meaning that the distance between the positive and negative tabs 32 and the distance between the side edge of the electrode assembly 20 stacked with the tabs and the tabs along the third direction W are too small, and the width of the first adhesive 40 along the third direction W is generally larger than the distance between the positive and negative tabs 32 or the distance between the side edge of the electrode assembly 20 stacked with the tabs and the tabs, thereby ensuring that the first adhesive 40 is difficult to pass through the gap between the tab adhesive of the positive tab 31 and the tab adhesive of the negative tab 32 or the gap between the side edge of the electrode assembly 20 stacked with the tabs and the tabs.

[0131] As shown in FIG. 10, in some embodiments, the first double-face blank section 2231 has a first winding end 220 away from the winding center of the electrode assembly 20;

[0132] The first separation film 21 has a second winding end 210 away from the winding center of the electrode assembly 20;

[0133] The second separation film 23 has a third winding end 230 away from the winding center of the electrode assembly 20;

[0134] The secondary battery includes a third adhesive 60, the first winding end 220 is adhered to the surface of the first double-sided blank section 2231 facing away from the winding center of the electrode assembly 20 by the third adhesive 60, and the second winding end 210 and the third winding end 230 are sandwiched between the third adhesive 60 and the surface of the second double-sided blank section 223 facing away from the winding center of the electrode assembly 20. As an example, the third adhesive 60 is a single-sided adhesive tape. As such an adhesive tape, green tape can be listed. The advantage of such an arrangement is that, on the one hand, the third adhesive 60 can play a role in restraining the electrode assembly 20; on the other hand, the third adhesive 60 plays an auxiliary role in maintaining the adhesive fixation between the first single-sided blank section 2221 and the first layer film 211 or the second layer film 231, that is, it can reduce the impact of the first winding end 220, the second winding end 210 and the third winding end 230 on the loosening of the fixed position of each component caused by the conduction of vibration to the first adhesive 40.

[0135] Further, along the winding direction Su of the electrode assembly, the third winding end 230 exceeds the first winding end 220; the second winding end 210 exceeds the third winding end 230. The adhesive tape adheres the first winding end 220, the second winding end 210, the third winding end 230 and the surface of the first double-sided blank section 2231 facing away from the winding center of the electrode assembly 20, respectively. Thus, through the adhesive fixation of the adhesive tape, the constraint on the outermost isolation film is strengthened, and the occurrence of the case of mechanical stress concentration between the stacked layers caused by the shrinkage of the outermost isolation film is further reduced.

[0136] In some embodiments, along the winding direction Su of the electrode assembly, the length by which the third winding end 230 exceeds the first winding end 220 is 2mm to 10mm.

[0137] In some embodiments, the unit length adhesive force between the adhesive tape and the second winding end 210 is greater than or equal to 0.05N / mm.

[0138] In some embodiments, along the winding direction Su of the electrode assembly, the length by which the second winding end 210 exceeds the third winding end 230 is 2mm to 10mm.

[0139] In some embodiments, the unit length adhesive force between the adhesive tape and the third winding end 230 is greater than or equal to 0.05N / mm.

[0140] The electronic device of the present application can be, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, an illuminating appliance, a toy, a game machine, a timepiece, an electric tool, a flash lamp, a camera, a household large storage battery, and a lithium ion capacitor, etc.

[0141] The above description is merely an example of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process conversion using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A secondary battery, comprising an electrode assembly, the electrode assembly comprising a first separator, a positive electrode sheet, a second separator, and a negative electrode sheet which are sequentially stacked and wound, characterized in that: the positive electrode sheet comprises a first single-face blank section and a first double-face blank section, the first single-face blank section is located at a next outermost circle of the electrode assembly, the first double-face blank section is located at an outermost circle of the electrode assembly, and the first single-face blank section and the first double-face blank section are stacked in a first direction; the first separator comprises a first layer of film, and the first layer of film is located between the first single-face blank section and the first double-face blank section in the first direction; the negative electrode sheet comprises a first double-face coating section, the first double-face coating section is stacked with the first single-face blank section in the first direction, and the first double-face coating section is closer to a winding center of the electrode assembly than the first single-face blank section, wherein the first direction is a thickness direction of the electrode assembly; the second separator comprises a second layer of film, and the second layer of film is located between the first single-face blank section and the first double-face coating section; the secondary battery comprises a first adhesive, and the first single-face blank section is fixedly connected to the first layer of film or the second layer of film by the first adhesive; the secondary battery comprises a positive electrode tab and a negative electrode tab, the positive electrode tab is electrically connected to the positive electrode sheet, the negative electrode tab is electrically connected to the negative electrode sheet, and the positive electrode tab and the negative electrode tab protrude from the same side of the electrode assembly; the second layer of film comprises a second layer of film main body and a second overhanging portion, the second layer of film main body is stacked with the first single-face blank section in the first direction, and the second overhanging portion protrudes from a side edge of the first single-face blank section close to the positive electrode tab in a second direction, wherein the second direction is perpendicular to the first direction; the first adhesive comprises a first part and a second part, the first part is fixedly connected to a current collector surface of the first single-face blank section, the second part extends from the first part to the outside of the electrode assembly and is bent towards the positive electrode tab, and the second part is fixedly connected to the second overhanging portion; the secondary battery comprises a packaging bag, the packaging bag comprises a main body portion and a top sealing portion extending outward from one side of the main body portion, the electrode assembly is arranged in the main body portion, and the positive electrode tab and the negative electrode tab protrude from the top sealing portion; the electrode assembly is divided into a first half portion and a second half portion by a virtual plane where the top sealing portion is located and perpendicular to the first direction, wherein the first adhesive is located in the first half portion; the main body portion comprises a second main wall, the second main wall is arranged opposite to the second half portion in the first direction; and the secondary battery comprises a second adhesive, and the second half portion is fixedly connected to the second main wall by the second adhesive. ​ ​ ​ ​ ​ 2. The secondary battery according to claim 1, characterized by ​ ​ ​ 3. The secondary battery according to claim 2, characterized by ​ ​ ​ ​ 4. The secondary battery according to claim 3, characterized by The second isolation film comprises a plurality of third layer films; each of the third layer films comprises a third layer film body and a third overhang; along the second direction, the third overhang extends from the third layer film body and protrudes from a side edge of the positive electrode sheet close to the positive electrode tab; The second part is terminated at the positive electrode tab or the negative electrode tab and is adhesively fixed with the plurality of third overhangs located in the first half.

5. The secondary battery according to claim 4, characterized by The main body part comprises a first side and a second side, the first side is connected with the first main wall of the top sealing part, and the second side is connected with the second main wall; Along the second direction, the first side is spaced apart from and opposite to the first half, and the second side is spaced apart from and opposite to the second half; along the second direction, the average distance between the first side and the one side end surface of the negative electrode sheet located in the first half is less than the average distance between the second side and the one side end surface of the negative electrode sheet located in the second half.

6. The secondary battery according to claim 3, characterized by 0.1≤S / W≤0.8, 4≤S≤8; wherein, Along the third direction, the distance Smm between the tab adhesive of the positive electrode tab and the tab adhesive of the negative electrode tab; Along the third direction, the width of the electrode assembly is Wmm; wherein the third direction, the second direction and the first direction are perpendicular to each other.

7. The secondary battery according to any one of claims 2 to 6, characterized by, The first adhesive comprises a first adhesive layer and a second adhesive layer arranged in layers; the first adhesive layer is adhesively fixed to the current collector surface of the first single-sided blank section and the second overhang, respectively; the second adhesive layer is configured to be adhesively fixed to the packaging bag of the secondary battery.

8. The secondary battery according to any one of claims 2 to 6, characterized by The first double-sided blank section has a first winding end that is away from the winding center of the electrode assembly; The secondary battery comprises a third adhesive, and the first winding end is adhesively fixed to the surface of the first double-sided blank section away from the winding center of the electrode assembly through the third adhesive.

9. The secondary battery according to claim 8, characterized by The first isolation film has a second winding end that is away from the winding center of the electrode assembly, and the second isolation film has a third winding end that is away from the winding center of the electrode assembly; Along the winding direction of the electrode assembly, the third winding end is beyond the first winding end, and the second winding end is beyond the third winding end; The third adhesive is a single-sided adhesive paper, and the adhesive paper adhesively fixes the first winding end, the second winding end, the third winding end and the surface of the first double-sided blank section away from the winding center of the electrode assembly, respectively.

10. An electronic device, comprising: The secondary battery comprises the secondary battery according to any one of claims 1-9.

Images