Rechargeable batteries and electronic devices

Abstract

This application provides a secondary battery and electronic equipment, the secondary battery comprising an electrode assembly, the electrode assembly comprising a positive electrode plate, a negative electrode plate and a separator, the separator being provided between the positive electrode plate and the negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer, a groove formed on the surface of the negative electrode active material layer facing the positive electrode plate, the width of the groove being W mm and the pitch being S mm, the thickness of the electrode assembly being T 1 mm, and satisfying W ≥ S × T 1 / 1000. This application allows for adjusting the contact area between the surface of the negative electrode plate and the separator according to lithium-ion batteries of different thicknesses by adjusting the relationship between the width of the groove, the pitch of the groove and the thickness of the electrode assembly within the scope of this application, thereby increasing the adhesion between the negative electrode plate and the separator, improving the stability of the negative electrode plate, improving the deformation problem of the lithium-ion battery, and improving the cycle stability and safety of the lithium-ion battery.

Description

[Technical Field]

[0001] This application relates to the field of electrochemical technology, and more particularly to secondary batteries and electronic equipment. [Background technology]

[0002] Rechargeable batteries, such as lithium-ion batteries, possess characteristics such as high specific energy, high operating voltage, low self-discharge rate, small volume, and light weight, and are widely used in the field of electronic consumption. With the widespread application of lithium-ion batteries, market demands for their performance are increasing.

[0003] During repeated charge-discharge cycles, lithium-ion batteries can experience internal stress accumulation and deformation. This can lead to the battery's thickness exceeding standard limits, accelerating cycle decay and affecting its cycle stability. Furthermore, as heat accumulates within the lithium-ion battery during the cycle process, if this heat cannot be released in a timely manner, the risk of thermal runaway increases, impacting the battery's safety. [Overview of the project] [Problems that the invention aims to solve]

[0004] This application aims to provide a secondary battery and electronic device that improve the cycle stability and safety of lithium-ion batteries.

[0005] In this application, lithium-ion batteries are used as an example of secondary batteries, but the secondary batteries described in this application are not limited to lithium-ion batteries. The specific means are as follows. [Means for solving the problem]

[0006] The present invention provides a secondary battery comprising a positive electrode plate, a negative electrode plate, and a separator, wherein the separator is provided between the positive electrode plate and the negative electrode plate, and the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer, wherein a groove is formed on the surface of the negative electrode active material layer facing the positive electrode tab, the width of the groove is W mm, the pitch of the groove is S mm, the thickness of the electrode assembly is T 1 mm, and W ≥ S × T 1 / 1000. By controlling the width of the groove, the pitch of the groove, and the thickness of the electrode assembly to satisfy the scope of this invention, the contact area between the surface of the negative electrode plate and the separator can be adjusted according to lithium-ion batteries of different thicknesses, thereby adjusting the adhesive interface between the negative electrode plate and the separator, improving the stability of the negative electrode plate, improving the deformation problem of the lithium-ion battery, and improving the cycle stability and safety of the lithium-ion battery.

[0007] In some embodiments of this application, W ≤ 2 × S × T1. In this application, by ensuring that the width of the grooves, the pitch of the grooves, and the thickness of the electrode assembly meet the scope of this application, the adhesive interface between the negative electrode plate and the separator can be adjusted, improving the strain of the electrode plate in the XY direction, enhancing the stability of the negative electrode plate, improving the deformation problem of lithium-ion batteries, and improving the cycle stability and safety of lithium-ion batteries.

[0008] In some embodiments of this application, S×T1 / 400≦W≦S×T1 / 2. In this application, by controlling the width of the grooves, the pitch of the grooves, and the thickness of the electrode assembly to satisfy the scope of this application, the effective bonding area between the grooves on the surface of the negative electrode plate and the separator can be increased, thereby increasing the bonding strength between the negative electrode plate and the separator, improving the stability of the negative electrode plate, improving the deformation problem of lithium-ion batteries, and improving the cycle stability and safety of lithium-ion batteries.

[0009] In some embodiments of this application, 0.05 ≤ S ≤ 10 and 0.02 ≤ W ≤ 0.5. In this application, the width and pitch of the grooves are controlled within the above ranges. The contact area between the first adhesive layer in the separator and the recesses on the surface of the negative electrode active material layer can be increased, thereby increasing the adhesive force between the negative electrode plate and the separator, improving the stability of the negative electrode plate, mitigating the deformation problem of lithium-ion batteries, and improving the cycle stability and safety of lithium-ion batteries.

[0010] In some embodiments of this application, the OI value and S of the negative electrode plate satisfy S / OI ≤ 0.5, and in one embodiment, 0.0025 ≤ S / OI ≤ 0.2, and in another embodiment, 0.005 ≤ S / OI ≤ 0.03, where OI value = C 004 / C 110 , C 004 This is the peak area obtained from the (004) plane diffraction pattern in the X-ray diffraction pattern, C 110 This is the peak area obtained from the (110) plane diffraction pattern in the X-ray diffraction pattern.

[0011] This technology improves the adhesive strength between the negative electrode plate and the separator, reduces expansion deformation of the electrode plate in the XY direction, effectively reduces side reactions during high-current-rate charging of lithium-ion batteries, improves the degree of polarization of lithium-ion batteries during the charging process, and thus improves the charging speed of lithium-ion batteries.

[0012] In some embodiments of this application, an adhesive layer is provided on the surface of the separator facing the negative electrode tab, and the adhesive layer contains a polymer, with the polymer content ranging from 30% to 100% based on the mass of the adhesive layer. Through the combined effect of the above structural design and material selection, the adhesive strength between the negative electrode plate and the separator can be increased, improving the stability of the negative electrode plate, mitigating the deformation problem of lithium-ion batteries, and improving the cycle stability and safety of lithium-ion batteries.

[0013] In some embodiments of the present application, the thickness of the adhesive layer is T2 μm, the depth of the concave groove is H μm, and by satisfying H ≦ T2 + 20, the contact area between the adhesive layer in the separator and the concave groove on the surface of the negative electrode active material layer can be increased, the adhesive force between the negative electrode plate and the separator can be increased, the stability of the negative electrode plate can be improved, the problem of deformation of the lithium-ion battery can be improved, and the cycle stability and safety of the lithium-ion battery can be improved.

[0014] In some embodiments of the present application, the cross-sectional area of the concave groove is A μm 2 and 0.3×(W×H) < A < 0.95×(W×H), 2 ≦ H ≦ 50. In one aspect, 0.35×(W×H) < A < 0.8×(W×H) is satisfied. By satisfying the above relationship among A, W, and H and controlling H within the above range in cooperation, the adhesive area between the surface of the negative electrode plate and the separator can be effectively increased. In particular, the adhesive area between the side of the concave groove and the separator is increased, the adhesive force between the negative electrode plate and the separator is increased, the stability of the negative electrode plate is improved, the problem of deformation of the lithium-ion battery is improved, and the cycle stability and safety of the lithium-ion battery are improved.

[0015] In some embodiments of the present application, the polymer includes at least one of polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, styrene - butadiene copolymer, polyacrylonitrile, butadiene - acrylonitrile polymer, polyacrylic acid, polyacrylate, and acrylate - styrene copolymer. The present application is advantageous for improving the interfacial adhesive force and heat resistance performance of the separator by controlling the separator to include the above polymer.

[0016] In some embodiments of the present application, along the width direction of the negative electrode plate, the concave groove portion forms a structure that penetrates the negative electrode plate. Here, the concave groove includes a first segment with a width of W1 and a second segment with a width of W2, and satisfies 1.2 < W1 / W2 < 1.8. By controlling the above configuration and the relationship between the widths of the first segment and the second segment within the above range, the contact area between the surface of the negative electrode plate and the separator can be effectively increased, and the adhesion between the negative electrode plate and the separator can be enhanced.

[0017] In some embodiments of the present application, along the width direction of the negative electrode plate, the concave groove forms a structure that does not penetrate the negative electrode plate. By configuring it in this way, while being advantageous for the stress release of the negative electrode active material during cycling, the local adhesion between the negative electrode plate and the separator can be improved, further improving the cycle performance and cycle swelling of the secondary battery. Also, the process difficulty during the manufacture of the concave groove can be reduced, and the manufacturing cost can be lowered.

[0018] The second invention of the present application provides an electronic device including the secondary battery described in the above embodiment. Thereby, the electronic device has good cycle stability and safety.

Effect of the Invention

[0019] The present application provides a secondary battery and an electronic device. Among them, when observed from the thickness direction of the negative electrode plate, the surface of the negative electrode active material layer of the negative electrode plate includes concave grooves. In the present application, by controlling the width of the concave grooves, the interval between the concave grooves, and the thickness of the electrode assembly within the scope of the present application, according to lithium-ion batteries of different thicknesses, the contact area between the surface of the negative electrode plate and the separator can be adjusted. As a result, the adhesion between the negative electrode plate and the separator can be improved, the stability of the negative electrode plate can be enhanced, the deformation problem of the lithium-ion battery can be improved, and the cycle stability and safety of the lithium-ion battery can be improved.

Brief Description of the Drawings

[0020] The drawings described herein form part of this application and are provided to offer a further understanding of this application. The schematic embodiments and their descriptions of this application interpret this application and do not limit this application. [Figure 1] It is a schematic structural diagram of an electrode assembly in some embodiments of this application. [Figure 2] It is a schematic cross-sectional structural diagram of an electrode assembly along its own thickness direction in some embodiments of this application. [Figure 3] It is a schematic cross-sectional structural diagram of a negative electrode plate along its own thickness direction in some embodiments of this application. [Figure 4] It is a plan view of a negative electrode plate along its own thickness direction in some embodiments of this application. [Figure 5] It is a schematic cross-sectional structural diagram of a separator along its own thickness direction in some embodiments of this application. [Figure 6] It is a schematic structural diagram observed from the thickness direction of a separator in some other embodiments of this application. [Figure 7] It is a schematic structural diagram of a concave groove of a negative electrode plate in some embodiments of this application. [Figure 8] It is a schematic structural diagram of a concave groove in some other embodiments of this application. [Figure 9] It is a concave groove which is a schematic structural diagram of a concave groove of a negative electrode plate in some other embodiments of this application.

Modes for Carrying Out the Invention

[0021] To make the objectives, technical solutions and advantages of this application clearer, the following provides examples with reference to the drawings to explain this application in more detail. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, those skilled in the art will fall within the scope of protection sought for this application for all other embodiments that can be made without creative efforts.

[0022] In the specific embodiments described in this application, lithium-ion batteries were used as an example of secondary batteries, but the secondary batteries described in this application are not limited to lithium-ion batteries. The specific means are as follows.

[0023] The first invention of this application provides a secondary battery, which, as shown in Figure 1, comprises an electrode assembly 10, where the X direction is the longitudinal direction of the electrode assembly 10, the Y direction is the width direction of the electrode assembly 10, and the Z direction is the thickness direction of the electrode assembly 10. As shown in Figure 2, the electrode assembly 10 includes a positive electrode plate 20, a negative electrode plate 30, and a separator 40, the separator 40 being provided between the positive electrode plate 20 and the negative electrode plate 30, the positive electrode plate 20 including a positive electrode current collector 21 and a positive electrode active material layer 22, and the negative electrode plate 30 including a negative electrode current collector 31 and a positive electrode active material layer 32, the negative electrode active material layer 32 having grooves 321 on the surface facing the positive electrode plate 20. As shown in Figures 3 and 4, the width of the grooves 321 is W mm, and the pitch of the grooves 321 is S mm. As shown in Figure 1, the thickness of the electrode assembly 10 is T1 mm, and W ≥ S × T1 / 1000. In this application, the width of the groove means the width of the groove on the surface of the negative electrode plate, and the pitch of the groove means the distance between two adjacent grooves. In this application, the negative electrode active material layer 32 may be provided on one side or on both sides.

[0024] This application allows for adjusting the contact area between the surface of the negative electrode plate and the separator according to lithium-ion batteries of different thicknesses by controlling the width of the grooves, the pitch of the grooves, and the thickness of the electrode assembly within the scope of this application. This increases the adhesive force between the negative electrode plate and the separator, improves the stability of the negative electrode plate, mitigates the deformation problem of lithium-ion batteries, and improves the cycle stability and safety of lithium-ion batteries.

[0025] In some embodiments of the present application, W ≤ 2×S×T1. By controlling the width of the concave groove, the pitch of the concave groove, and the thickness of the electrode assembly within the scope of the present application, the contact area between the concave groove on the surface of the negative electrode plate and the separator can be effectively increased, thereby increasing the adhesion between the negative electrode plate and the separator, improving the stability of the negative electrode plate, improving the deformation problem of the lithium-ion battery, and improving the cycle stability and safety of the lithium-ion battery.

[0026] In some embodiments of the present application, S×T1 / 400 ≤ W ≤ S×T1 / 2 is satisfied. By controlling the width of the concave groove, the pitch of the concave groove, and the thickness of the electrode assembly within the scope of the present application, the contact area between the concave groove on the surface of the negative electrode plate and the separator can be effectively increased, thereby increasing the adhesion between the negative electrode plate and the separator, improving the stability of the negative electrode plate, improving the deformation problem of the lithium-ion battery, and improving the cycle stability and safety of the lithium-ion battery.

[0027] In some embodiments of the present application, 0.05 ≤ S ≤ 10 and 0.02 ≤ W ≤ 0.5 are satisfied. Without being limited by any theory, by adjusting the width of the concave groove and the pitch of the concave groove within the above ranges, the contact area between the first adhesive layer in the separator and the concave groove on the surface of the negative active material layer can be increased, thereby increasing the adhesion between the negative electrode sheet and the separator, improving the stability of the negative electrode plate, improving the deformation problem of the lithium-ion battery, and improving the cycle stability and safety of the lithium-ion battery.

[0028] In some embodiments of the present application, the OI value of the negative electrode plate and S satisfy S / OI ≤ 0.5. In one embodiment, 0.0025 ≤ S / OI ≤ 0.2 is satisfied. In one embodiment, 0.005 ≤ S / OI ≤ 0.03 is satisfied. However, the OI value = C 004 / C 110 、C 004 is the peak area obtained from the diffraction line pattern of the (004) plane in the X-ray diffraction pattern, and C 110This is the peak area obtained from the (110) plane diffraction pattern in the X-ray diffraction pattern.

[0029] Through research, the inventors have found that as the OI value increases, the degree of bend in the transmission of lithium ions in the graphite within the negative electrode active material increases, leading to greater polarization during the charging process of the lithium-ion battery. Conversely, when the OI value is low, the battery tends to deform in the XY direction. While not limited to any theory, this application aims to increase the adhesive strength between the negative electrode plate and the separator by controlling the groove pitch and the OI value of the negative electrode plate within the above range, while simultaneously reducing the expansion deformation of the electrode plate in the XY direction. This effectively reduces side reactions in the high-magnification charge state of the lithium-ion battery, improves the degree of polarization during the charging process of the lithium-ion battery, and thereby improves the charging speed of the lithium-ion battery.

[0030] In some embodiments of this application, an adhesive layer is provided on the surface of the separator facing the negative electrode plate, and the adhesive layer contains a polymer, wherein the polymer content is 30% to 100% based on the mass of the adhesive layer.

[0031] Exemplary, in some embodiments of this application, as shown in Figure 5, the separator 40 includes a base layer 41 and an adhesive layer 431 provided on the surface of the base layer 41, the adhesive layer 431 containing a polymer and a heat-resistant material. The synergistic effect of the above structural design and material selection enhances the adhesion between the negative electrode plate and the separator, improves the stability of the negative electrode plate, mitigates the deformation problem of lithium-ion batteries, and improves the cycle stability and safety of lithium-ion batteries. Furthermore, an adhesive layer containing both polymer and heat-resistant material can be obtained in a single coating step, simplifying the process steps and contributing to reduced production costs. Here, based on the mass of the adhesive layer, the polymer content is 30% to 80%, and the heat-resistant material content is 20% to 70%.

[0032] Exemplary, in some other embodiments of this application, as shown in Figure 6, the separator 40 comprises a base layer 41, on the surface of the base layer 41 a heat-resistant material layer 42 and an adhesive layer 431 are provided in order, the heat-resistant material layer 42 contains a heat-resistant material, and based on the mass of the adhesive layer, the polymer content is 100%. The synergistic effect of the above structural design and material selection can increase the adhesive strength between the negative electrode plate and the separator, improve the stability of the negative electrode plate, alleviate the deformation problem of the lithium-ion battery, and improve the cycle stability and safety of the lithium-ion battery.

[0033] This application does not impose any special restrictions on the heat-resistant material of the heat-resistant layer, as long as it can achieve the objectives of this application. For example, the heat-resistant material may include at least one of a ceramic material or a heat-resistant polymer material. The ceramic material may include at least one of Al2O3, boehmite, SiO2, TiO2, MgO, ZnO, ZrO2, or SnO2, and the heat-resistant polymer material may include at least one of polyimide and its derivatives, aromatic nylon and its modified products, phenolic resin, or polytetrafluoroethylene.

[0034] In some embodiments of this application, as shown in Figure 3, the depth of the groove 321 is H μm, and as shown in Figure 5, the thickness of the first adhesive layer 431 is T2 μm, satisfying H ≤ T2 + 20. By controlling H and T2 to satisfy the above relationship, the contact area between the first adhesive layer in the separator and the groove on the surface of the negative electrode active material layer can be increased, thereby increasing the adhesive strength between the negative electrode plate and the separator, improving the stability of the negative electrode plate, mitigating the deformation problem of lithium-ion batteries, and improving the cycle stability and safety of lithium-ion batteries.

[0035] In some embodiments of the present application, as shown in FIG. 3, the depth of the concave groove 321 is H μm, and as shown in FIG. 6, the thickness of the adhesive layer 431 is T2 μm, satisfying H≤T2 + 20, and preferably satisfying H≤T2 + 15. By controlling H and T2 to satisfy the above relationship, the contact area between the adhesive layer in the separator and the concave groove on the surface of the negative electrode active material layer can be increased, the adhesive force between the negative electrode plate and the separator can be increased, the stability of the negative electrode plate can be improved, the deformation problem of the lithium-ion battery can be improved, and the cycle stability and safety of the lithium-ion battery can be improved.

[0036] In some embodiments of the present application, as shown in FIG. 3, the cross-sectional area of the concave groove 321 is A μm 2 and satisfies 0.3×(W×H)<A<0.95×(W×H), 2≤H≤50. In one embodiment, it satisfies 0.35×(W×H)<A<0.8×(W×H). In the present application, the cross-sectional area of the concave groove means the area of the cross-section formed by the groove in the cross-section along the thickness direction of the negative electrode plate itself. By controlling A, W, and H to satisfy the above relationship and coordinately adjusting H within the above range, the adhesion area between the surface of the negative electrode plate and the separator can be effectively increased, especially the adhesion area between the side of the concave groove and the separator can be increased, thereby increasing the adhesive force between the negative electrode plate and the separator, improving the stability of the negative electrode plate, improving the deformation problem of the lithium-ion battery, and improving the cycle stability and safety of the lithium-ion battery.

[0037] In some embodiments of the present application, the polymer includes at least one of polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, styrene - butadiene copolymer, polyacrylonitrile, butadiene - acrylonitrile polymer, polyacrylic acid, polyacrylate, or acrylate - styrene copolymer, which is advantageous for improving the interfacial adhesion force of the separator.

[0038] In some embodiments of the present application, as shown in FIG. 7, along the width direction of the negative electrode plate 30, the concave groove 321 forms a structure penetrating the negative electrode plate. The concave groove 321 includes a first segment 3211 with a width of W1 and a second segment 3212 with a width of W2, satisfying 1.2 < W1 / W2 < 1.8. As is clear from FIG. 7, the penetrating concave groove 321 includes a first segment 3211, a second segment 3212, and a third segment 3213. By controlling the above structure and the relationship between the widths of the first segment and the second segment within the above range, the contact area between the surface of the negative electrode plate and the separator can be effectively increased, and the adhesion force between the negative electrode plate and the separator can be enhanced.

[0039] In some embodiments of the present application, as shown in FIG. 8, along the width direction of the negative electrode plate 30, the concave groove 321 forms a structure that does not penetrate the negative electrode plate. As is clear from FIG. 8, the concave groove 321 has a first segment 3211, a second segment 3212, and a third segment 3213. The first segment 3211, the second segment 3212, and the third segment 3213 do not overlap, and the third segment 3213 is located between the first segment 3211 and the second segment 3212. The first segment 3211, the second segment 3212, and the third segment 3213 are provided in parallel, thereby forming a non-penetrating concave groove 321. Among them, when observed from the length direction of the electrode plate, there is a first overlapping region in the first segment 3211 and the second segment 3212, and a second overlapping region in the second segment 3212 and the third segment 3213. In the width direction of the electrode plate, the lengths of the first overlapping region and the second region are less than 30% of the width of the electrode plate. With the above configuration, the local adhesion performance between the negative electrode plate and the separator can be improved, which is beneficial for the stress release of the negative electrode active material during the cycle process, thereby further improving the cycle performance and cycle expansion of the secondary battery. Also, it is beneficial for reducing the process difficulty during the manufacture of the concave groove, thereby reducing the production cost. <L

[0040] In some embodiments of this application, as shown in Figure 9, the groove 321 along the width direction of the negative electrode plate 30 forms a structure that does not penetrate the negative electrode plate. As can be seen from Figure 9, the groove 321 has a first segment 3211 and a second segment 3212, and the first segment 3211 and the second segment 3212 do not overlap and can be provided parallel to each other, thereby forming a groove 321 with a non-penetrating structure. When observed from the length direction of the electrode plate, there is a first overlapping region between the first segment 3211 and the second segment 3212, and in the width direction of the electrode plate, the length of the first overlapping region is less than 30% of the width of the electrode plate. The above configuration improves the local adhesion performance between the negative electrode plate and the separator, facilitates stress release of the negative electrode active material during the cycle process, thereby further improving the cycle performance and cycle expansion of the secondary battery. It also reduces the difficulty of the manufacturing process for the grooves, thereby reducing production costs.

[0041] To make it clear, the electrode assembly of this application can be a wound structure, and when its electrode plates are unfolded, they typically have a long side and a short side. In one embodiment of this application, when the electrode assembly is a wound structure, the width direction is the direction of extension of the short side after the electrode plates have been unfolded, and the length direction is the direction of extension of the long side after the electrode plates have been unfolded. The electrode plates of this disclosure comprise a positive electrode plate 20 and a negative electrode plate 30.

[0042] The secondary battery of this application may include any device that causes an electrochemical reaction, as long as it achieves the purpose of this application. For example, the secondary battery includes, but is not limited to, lithium-ion secondary batteries (lithium-ion batteries), sodium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries. The battery structure of this application includes, but is not limited to, soft pack type batteries, prismatic hard case batteries, or cylindrical hard case batteries.

[0043] This application does not impose any special restrictions on the negative electrode current collector, and is acceptable as long as it achieves the objectives of this application. For example, the negative electrode current collector may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, or composite current collectors. This application does not impose any special restrictions on the thickness of the negative electrode current collector, and is acceptable as long as it achieves the objectives of this application. For example, the thickness of the negative electrode current collector is 4 μm to 10 μm. In this application, the negative electrode active material layer may be provided on one surface in the thickness direction of the negative electrode current collector, or on two surfaces in the thickness direction of the negative electrode current collector. Here, "surface" may refer to the entire area of ​​the negative electrode current collector, or to a part of the area of ​​the negative electrode current collector, and this application does not impose any special restrictions, and is acceptable as long as it achieves the objectives of this application.

[0044] This application does not impose any special restrictions on the type of negative electrode active material, as long as it can achieve the objectives of this application. For example, the negative electrode active material includes graphite, a mixture of graphite and silicon, silicon oxide, or silicon carbide, and the graphite can be selected from artificial graphite or natural graphite. Optionally, the negative electrode active material layer may further contain at least one of a conductive agent, a thickener, or an adhesive. This application does not impose any special restrictions on the type of conductive agent, thickener, and binder in the negative electrode active material layer, as long as it can achieve the objectives of this application. For example, the negative electrode adhesive includes, but is not limited to, at least one of polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-difluoroethylene), polyethylene, polypropylene, polyacrylic acid, styrene-butadiene rubber, acrylic styrene-butadiene rubber, epoxy resin, or nylon. This application does not impose any special restrictions on the mass ratio of the negative electrode active material, conductive agent, thickener, and binder in the negative electrode active material layer, and is acceptable as long as it achieves the objective of this application. For example, the mass ratio of the negative electrode active material, conductive agent, thickener, and binder in the negative electrode active material layer is (96-98):(0-1.5):(0.5-1.5):(1.0-1.9).

[0045] This application does not impose any special restrictions on the OI value of the negative electrode plate, and only needs to be such that the objective of this invention is achieved. For example, the OI value may be between 5 and 30.

[0046] This application does not impose any special restrictions on the material of the separator substrate layer, and those skilled in the art can select it based on their actual needs, as long as it achieves the objectives of this application. For example, the material of the separator substrate layer includes, but is not limited to, at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, etc. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane can be used.

[0047] In this application, there are no special restrictions on the thickness of the first adhesive layer and / or the second adhesive layer in the separator, and it is sufficient to achieve the objective of the invention of this application. For example, the thickness of the first adhesive layer and / or the second adhesive layer may be from 1 μm to 20 μm.

[0048] The secondary battery of this application further comprises an electrolyte, and this application does not particularly limit the electrolyte; a person skilled in the art can select it based on actual needs, as long as it achieves the purpose of this application. For example, at least one of the following can be mixed in a certain mass ratio to obtain a non-aqueous organic solvent: ethylene carbonate (also called ethylene carbonate, abbreviated as EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), propyl propionate (PP), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC), then a lithium salt can be added, dissolved, and mixed uniformly. The above "mass ratio" in this application does not have any particular limitations and is as long as it achieves the purpose of this application. This application does not limit the type of lithium salt, as long as it achieves the purpose of this application. Examples of lithium salts include at least one of LiPF6, LiBF4, LiAsF6, LiC1O4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, lithium dioxalatoborate (LiBOB), and lithium difluoroborate. In this application, there are no special restrictions on the concentration of the lithium salt in the electrolyte; it is sufficient to achieve the objectives of this application. For example, the concentration of the lithium salt is 1.0 mol / L to 2.0 mol / L.

[0049] The positive electrode plate of this application may comprise a positive electrode active material layer and a positive electrode current collector. This application does not impose any special restrictions on the type of positive electrode active material, as long as it can achieve the objectives of this application. The positive electrode active material may include, for example, at least one of the following: lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, etc. In this application, the positive electrode active material may include nonmetallic elements, for example, at least one of the following: fluorine, phosphorus, boron, chlorine, silicon, or sulfur. These elements can further enhance the stability of the positive electrode active material. The positive electrode active material layer of this application may further include a conductive agent and an adhesive. The mass ratio of the positive electrode active material, conductive agent, and adhesive in the positive electrode active material layer of this application is not particularly limited and can be selected by those skilled in the art based on actual needs, as long as it can achieve the objectives of this application. The mass ratio of the positive electrode active material, conductive agent, and adhesive in the positive electrode active material layer is, for example, (96-98):(1-3):(2-3).

[0050] This application does not impose any special restrictions on the positive electrode current collector, and is acceptable as long as it achieves the objectives of this application. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil, or a composite current collector. This application does not impose any special restrictions on the thickness of the positive electrode current collector, as long as it achieves the objectives of this application. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm. In this application, the positive electrode active material layer may be provided on one surface in the thickness direction of the positive electrode current collector, or on two surfaces in the thickness direction of the positive electrode current collector. Here, "surface" may refer to the entire area of ​​the positive electrode current collector, or to a part of the area of ​​the positive electrode current collector, and this application does not impose any special restrictions, and is acceptable as long as it achieves the objectives of this application.

[0051] This application does not impose any special restrictions on the method for manufacturing the negative electrode plate, and is acceptable as long as it achieves the objective of this application. For example, a method for manufacturing a negative electrode plate may include, but is not limited to, the following steps: dispersing and mixing a negative electrode active material, a conductive agent, a thickener, and an adhesive in deionized water to form a uniform negative electrode slurry; applying the negative electrode slurry onto a negative electrode current collector; drying and cold pressing; forming grooves on the surface of the negative electrode plate; and subsequently performing cutting and slitting steps to obtain a negative electrode plate with the structure shown in Figure 3.

[0052] This application does not impose any particular restrictions on the method for manufacturing a positive electrode plate, and is acceptable as long as it achieves the objectives of this application. For example, a method for manufacturing a positive electrode plate may include, but is not limited to, the following steps: dispersing and mixing an active material, a conductive agent, and a binder in an NMP solvent to form a uniform positive electrode slurry; applying the positive electrode slurry onto a positive electrode current collector; and drying, cold pressing, cutting, and slitting to obtain a positive electrode plate.

[0053] In this application, there are no special restrictions on the shape of the groove, and it is acceptable as long as the purpose of this application is achieved. For example, when viewed from the longitudinal direction of the negative electrode plate, the shape of the groove may include at least one of a square, rectangle, trapezoid, triangle, or semicircle, and when viewed from the thickness direction of the negative electrode plate, the shape of the groove may include at least one of a straight line, diagonal line, bent line, or curved line.

[0054] This application does not impose any special restrictions on the method of manufacturing grooves, as long as the objective of this application is achieved. For example, it includes, but is not limited to, laser etching, machining, or pore-forming agent processing. Taking laser etching as an example, the width and depth of the grooves usually increase as the laser output increases, and the pitch of the grooves can usually be adjusted by the laser processing speed. Therefore, technicians can adjust parameters such as the width, depth, and pitch of the grooves by adjusting parameters such as the laser output, processing speed, and electrode plate travel speed. In this application, as shown in Figure 1, the electrode assembly includes a flat region and a bent region. In the manufacturing process of lithium-ion batteries, technicians can provide grooves in the bent region as needed for design purposes, that is, provide grooves in the region where the electrode plates of the electrode assembly are bent, thereby improving the interfacial adhesion performance of the negative electrode plate in that region and improving the cycle stability and safety of the lithium-ion battery.

[0055] This application is not particularly limited to the method for manufacturing a secondary battery, and any manufacturing method known in the art can be selected as long as it can achieve the objectives of this application. For example, a method for manufacturing a secondary battery may include, but is not limited to, the steps of stacking a positive electrode plate, a separator and a negative electrode plate in order, performing operations such as winding and folding as necessary to obtain a wound electrode assembly, then placing the electrode assembly in a packaging bag, injecting electrolyte into the packaging bag and sealing it to obtain a secondary battery.

[0056] A second embodiment of this application provides an electronic device equipped with the secondary battery described in the above embodiment. As a result, the electronic device has good cycle stability and safety.

[0057] This application does not impose any special restrictions on electronic devices, and may include any electronic device known in the existing art. In some embodiments, and in some examples, the electronic device includes, but is not limited to, laptop computers, pen-input computers, mobile computers, e-readers, mobile phones, portable fax machines, portable copiers, portable printers, headphone stereos, video recorders, LCD televisions, handheld vacuum cleaners, portable CD players, MiniDiscs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles (E-bikes), bicycles, lighting fixtures, toys, game consoles, clocks, power tools, strobes, cameras, large household batteries or lithium-ion capacitors, etc.

[0058] Examples The embodiments of this application will be described in more detail below with reference to examples and comparative examples. Various tests and evaluations will be carried out according to the following methods.

[0059] Test method and apparatus: Test of the adhesive strength F between the negative electrode plate and the separator: Cut out a negative electrode plate to which a separator measuring 15mm x 60mm is attached, and fix the sample to a steel plate using double-sided tape measuring 20mm x 100mm, with the test surface facing downwards. Insert one end of a paper tape, which has the same width as the sample and is 150mm longer than the sample, under the sample and secure it with wrinkle tape. Fix the steel plate to the bottom of the high-strength tensile testing machine, fix the other end of the paper tape to the upper chuck of the high-strength tensile testing machine, and then start the high-strength tensile testing machine. After the tensile force stabilizes, the tensile force data is used as the adhesive force.

[0060] Testing the thickness T1 of the electrode assembly: Under conditions of (25±3)℃, the thickness of the lithium-ion battery is measured using a micrometer and defined as T0. Next, the lithium-ion battery is disassembled, and the thickness of the disassembled packaging bag is measured and defined as T3. The thickness of the electrode assembly T1 is calculated using the following formula: T1 = T0 - T3.

[0061] Measurement of the OI value of the negative electrode plate: Based on the Chinese machinery industry standard JB / T4220-2011 "Method for Measuring Lattice Constants of Artificial Graphite," the 004 diffraction pattern and 110 diffraction pattern of the carbon coating on the negative electrode were measured. The test conditions were as follows: CuKa radiation was used for the X-rays, and the CuKa radiation was removed by a filter or monochromator. The operating voltage of the X-ray tube was (30-35)kV, and the operating current was (15-20)mA. The counter scanning speed was 1 / 4(°) / min. When the 004 diffraction pattern was recorded, the scanning range at diffraction angle 2θ was 53°~57°. When the 110 diffraction pattern was recorded, the scanning range at diffraction angle 2θ was 75°~79°.

[0062] Of the unit cell lengths obtained from the 004 diffraction pattern, the length of the c-axis is C 004 It is written as follows. Of the unit cell lengths obtained from the 110 diffraction line pattern, the length of the a-axis is C 110 This is written as follows. The OI value is calculated using the following formula.

[0063] OI value = C 004 / C 110

[0064] Testing of adhesive layer thickness T2: In the electrode assembly, a separator portion not facing the positive electrode active material layer or the negative electrode active material layer was selected, and after fabricating the separator cross-section by ion beam cross-sectional polishing (CP), the thickness T2 of the adhesive layer was measured using a scanning electron microscope (ZEISS Sigma / X-max).

[0065] Measurement of groove depth H, groove width W, groove pitch S, and groove cross-sectional area A: Using a VK-1050 laser confocal microscope, the grooved region is imaged, and optical and depth information of the electrode plate within the microscope's field of view is acquired. The surface of the electrode plate is scanned using laser confocal mode at 20x magnification. After the scan is complete, the acquired measurement data is processed using the data analysis software associated with the device. A reference plane is set for the measurement data using the "Reference plane setting" function in "Image processing," then the "Smoothing" function is selected, and the shape is smoothed by selecting the "5x5" size and "Simple average" type. After processing is complete, the parameters of the groove are measured using the "Contour measurement" function.

[0066] Depth H of groove and width W of groove: As shown in Figure 3, the depth of the groove is defined as the difference in depth between the deepest part of the groove and the reference surface, and the width of the groove is defined as the distance between the intersection points of both sides of the groove and the reference surface. Measurements were taken once at 10 μm intervals along the same groove, for a total of 20 measurements. The average values ​​of the depth and width from these 20 measurements were calculated and recorded as the groove depth H and width W.

[0067] Groove pitch S: For adjacent grooves (considered adjacent grooves when observed from the longitudinal direction of the electrode plate and the overlap portion of two adjacent grooves exceeds 50% of their respective lengths), the groove pitch is defined as the distance between the midpoints of the widths of the two grooves in the perpendicular direction of the grooves. Measurements are taken once at 10 μm intervals along the selected grooves, for a total of 20 measurements. The average value is calculated and denoted as the groove pitch S.

[0068] Area of ​​the groove A: Using a VK-1050 laser confocal microscope, the groove region is imaged, and optical and depth information of the pole piece within the microscope's field of view is acquired. The surface of the electrode plate is scanned using laser confocal mode at 20x magnification, and after the scan is complete, depth data relative to the reference line at the width of each pixel is acquired. Within the width of the groove, the depth (hi) at each pixel width (w0) is integrated to obtain A = Σ i h i *w0, let this be the cross-sectional area A of the groove.

[0069] Measurement of capacity retention rate and thickness expansion rate of lithium-ion batteries: At 25°C, a lithium-ion battery is charged with a constant current at a multiplier of 0.7C until the voltage reaches 4.5V, then charged with a constant voltage at 4.5V until the current reaches 0.05C, and subsequently discharged with a constant current at a multiplier of 1C until the voltage reaches 3.0V. This constitutes one charge-discharge cycle, and after repeating this charge-discharge cycle 500 times, the capacity retention rate and thickness expansion rate of the lithium-ion battery are measured.

[0070] The capacity retention rate of a lithium-ion battery after 500 cycles = Discharge capacity after 500 cycles / Discharge capacity after 1 cycle × 100%.

[0071] The thickness expansion rate of a lithium-ion battery after 500 cycles = Thickness of the lithium-ion battery after 500 cycles / Thickness of the lithium-ion battery after 1 cycle × 100%.

[0072] Measurement of the cycle interface of the negative electrode plate of a lithium-ion battery: A lithium-ion battery that has undergone 500 cycles is charged at 25°C with a constant current at a multiplier of 0.7C until the voltage reaches 4.5V, then charged at a constant voltage of 4.5V until the current reaches 0.05C. Subsequently, the battery is disassembled, and the operator visually observes the cycle interface of the negative electrode plate. If intermittent, pinpoint purple spots or lithium deposits occur on the surface of the negative electrode plate, or if lithium deposits occur on purple spots, it is determined that a minor interface problem has occurred in the negative electrode plate. If large, continuous purple spots or lithium deposits occur on the body of the negative electrode plate, or if lithium deposits occur on purple spots, it is determined that a serious interface problem has occurred in the negative electrode plate.

[0073] Measuring the heat box pass-through rate of lithium-ion batteries: Lithium-ion batteries were placed in a sealed temperature-controlled box and charged with a constant current at a multiplier of 0.7C at 25°C until the voltage reached 4.5V. Then, they were charged with a constant voltage at 4.5V until the current reached 0.05C. After that, the temperature-controlled box was heated at (5±2)°C / min until the temperature reached 130°C, and then kept at a constant temperature for 60 minutes. After the temperature-controlled box cooled naturally, the lithium-ion batteries were observed to see if they had ignited or exploded. A lithium-ion battery was considered to have passed if it did not ignite or explode. Each example or comparative example tested 100 lithium-ion batteries, and the heat box pass rate (%) = number of batteries passed / 100 × 100%.

[0074] Example 1 <Manufacturing of negative electrode plates> Synthetic graphite (OI value 14), sodium carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 97.5:1:1.5, and deionized water was added to prepare a slurry with a solid content of 75 wt%, which was then uniformly stirred. The slurry was uniformly applied to one surface of a 4 μm thick copper foil negative electrode current collector and dried at 85°C to obtain a negative electrode plate with a negative electrode active material layer thickness of 50 μm. The above process was then repeated on the other surface of this negative electrode plate to obtain a negative electrode plate with negative electrode active material applied to both sides. After cold pressing the obtained negative electrode plate, grooves were etched into the surface of the negative electrode active material layer using laser processing technology, followed by slitting and cutting. The electrode ear welding area was then cleaned, and the electrode ears were welded to obtain the negative electrode plate. The parameters such as groove depth H, groove width W, groove pitch S, and groove cross-sectional area A are shown in Table 1.

[0075] <Manufacturing of positive electrode plates> Lithium cobalt oxide, polyvinylidene fluoride, and conductive agent SuperP were mixed in a mass ratio of 96:2:2, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, which was then uniformly stirred. This slurry was uniformly applied to one surface of a 9 μm thick positive electrode current collector aluminum foil and dried at 95°C to obtain a positive electrode plate with a positive electrode active material layer thickness of 60 μm. The above process was then repeated on the other surface of the negative electrode plate to obtain a positive electrode plate with positive electrode active material applied to both sides. The positive electrode plate obtained above was then cold-worked, slit, and cut, the electrode ear welding area was cleaned, and the electrode ears were further welded to obtain a positive electrode plate.

[0076] <Preparation of Electrolyte> Ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, and vinylene carbonate were mixed in a mass ratio of 8:85:5:2 to obtain a non-aqueous organic solvent. Subsequently, an electrolyte was prepared by mixing lithium salt LiPF6 with the obtained non-aqueous organic solvent in a mass ratio of 8:92.

[0077] <Separator Manufacturing> <Manufacturing of the base layer> A 5μm thick polypropylene film was used.

[0078] <Manufacturing of heat-resistant material layer> The mass ratio of aluminum trioxide ceramic particles, butadiene styrene polymer, and deionized water was set to 35:10:55. A total of 30 kg of butadiene styrene polymer and deionized water were placed in a twin-screw planetary stirrer with a volume of 60 L and dispersed at 45°C for 3 hours. Subsequently, 16.1 kg of aluminum trioxide ceramic powder was added to the stirrer and dispersed at high speed at 45°C for 2 hours. After that, ball milling was performed using a nano-polishing machine for a milling time of 1.5 hours. The polishing medium used was spherical zirconia beads with a diameter of 6 μm, and a colloidal solution for a heat-resistant material layer was obtained.

[0079] The coating was applied to the substrate surface using a transfer coating method, with a coating speed of 6 m / min and a coating amount of 0.18 mg / cm². 2The material was adjusted to a coating thickness of 1.5 μm, a three-stage drying method was adopted, with each oven stage having a length of 3 m and oven temperatures set to 50°C, 60°C, and 60°C respectively, to form a base layer containing a heat-resistant material layer on one side. Subsequently, the above process was repeated on the other surface of the base layer to form a structure in which heat-resistant material layers were applied to both sides.

[0080] <Manufacturing of adhesive layer> Polymer particles having a core-shell structure were used, wherein the shell is a styrene-acrylic acid ester copolymer, the core is an acrylic acid ester polymer, the total swelling degree is 450%, and the particle size is 0.45 μm. The coating liquid for the polymer adhesive layer was prepared from 25 parts by mass of a core-shell structure polymer emulsion (40% solids), 40 parts by mass of deionized water, and 35 parts by mass of ethanol. The preparation process was as follows: A total of 50 kg of deionized water and ethanol solvent was added to a twin-screw planetary stirrer and mixed at 25°C for 1 hour. Then, 16.7 kg of core-shell structure polymer emulsion was added and dispersed at 45°C for 2 hours to obtain the coating liquid for the polymer adhesive layer.

[0081] A gravure roll coating method was used to apply the heat-resistant material layer to the surface of the porous substrate, forming a double-sided coating structure. The mass and thickness of both sides of the coating were kept the same, the coating speed was 6 m / min, and the coating amount was 0.036 mg / cm². 2 The process is adjusted to employ a three-stage drying method, with each stage having an oven length of 3m and oven temperatures set to 50°C, 60°C, and 60°C respectively. After drying, a polymer adhesive layer with single-layer particles is obtained, and the thickness of the adhesive layer is 2μm.

[0082] <Manufacturing of lithium-ion batteries> The positive electrode plate, separator, and negative electrode plate manufactured as described above are stacked in order, with the grooved surface of the negative electrode plate facing the positive electrode plate, and the separator placed between the positive and negative electrode plates to provide isolation. After this, they are wound to obtain an electrode assembly, and the thickness of the electrode assembly is shown in Table 1. The electrode assembly is placed in an aluminum plastic film packaging bag, dried, and then the electrolyte is injected. A lithium-ion battery is obtained through processes such as vacuum sealing, standing, chemical conversion, degassing, and trimming.

[0083] Examples 2 to 25 In the <Manufacturing of Negative Electrode Plate> and <Manufacturing of Lithium-ion Battery>, the manufacturing parameters such as the thickness T1 of the electrode assembly, the OI value of the graphite, the thickness T2 of the adhesive layer, the depth H of the groove, the width W of the groove, the pitch S of the groove, and the cross-sectional area A of the groove were adjusted as shown in Table 2, except that they were the same as in Example 1.

[0084] Example 26 Aside from adjusting the <separator manufacturing process>, other parameters were adjusted according to Table 2, in addition to those in Example 9.

[0085] <Separator Manufacturing> <Manufacturing of the base layer> A polypropylene film with a thickness of 9 μm was used.

[0086] <Manufacturing of adhesive layer> Polyvinylidene fluoride and aluminum trioxide ceramic particles were mixed in a mass ratio of 60:40, and NMP was added as a solvent to prepare an adhesive layer slurry with a solid content of 75 wt%, which was then stirred until uniform. The adhesive layer slurry was applied to the surface of one substrate layer and dried at 90°C to obtain an adhesive layer, the thickness of which is shown in Table 2. Subsequently, the above process was repeated on the surface of the other substrate layer to obtain a separator with adhesive layers applied to both sides.

[0087] Example 27 In the <Separator Production>, the procedure is the same as in Example 26, except that the type of polymer is adjusted to a polyvinylidene fluoride-hexafluoropropylene copolymer.

[0088] Comparative Example 1 Except for the preparation of the negative electrode plate, the procedure is the same as in Example 1.

[0089] <Manufacturing of negative electrode plates> Artificial graphite (OI value 14), conductive carbon black (SP), carboxymethylcellulose sodium (CMC), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 96.5:1:1:1.5, and deionized water was added to prepare a slurry with a solid content of 75 wt%, which was then uniformly stirred. This slurry was uniformly applied to one surface of a 6 μm thick copper foil negative electrode current collector and dried at 85°C. After obtaining a negative electrode plate with a negative electrode active material layer thickness of 50 μm, the above process was repeated on the other surface of this negative electrode plate to obtain a negative electrode plate with negative electrode active material applied to both sides. After further slitting and cutting, it was dried under vacuum conditions at 110°C for 4 hours, and electrode tabs were welded to obtain a negative electrode plate.

[0090] Comparative Example 2 In the <Separator Manufacturing>, the process was the same as in Comparative Example 1, except that the thickness of the adhesive layer was adjusted to 5 μm and the adhesive strength F between the negative electrode plate and the separator was adjusted to 12 N / m.

[0091] Comparative Examples 3-4 In the <Manufacturing of Negative Electrode Plates> and <Manufacturing of Lithium-ion Batteries>, the manufacturing parameters such as the thickness T1 of the electrode assembly, the width W of the groove, and the pitch S of the groove were adjusted as shown in Table 1, except that they were the same as in Example 1.

[0092] [Table 1] Note: In Table 1, " / " indicates that the corresponding manufacturing parameter is not available.

[0093] [Table 2] Note: In Table 2, " / " indicates that the corresponding manufacturing parameter is not available.

[0094]

Table 3

[0095] Referring to Table 1, as is clear from Examples 1 to 2 and Comparative Examples 1 to 4, in the lithium-ion battery of the present application, by providing concave grooves on the surface of the negative electrode active material layer facing the positive electrode plate and controlling the relationship between the width of the concave grooves, the pitch of the concave grooves, and the thickness of the electrode assembly within the scope of the present application, the adhesive force between the negative electrode plate and the separator can be improved. Further, the heat box passing rate of the lithium-ion battery is significantly improved, and the thickness expansion rate after the cycle process of the lithium-ion battery is also significantly reduced. The lithium-ion battery of the present application has excellent cycle stability and safety, and particularly exhibits excellent cycle stability and safety under high-temperature environments.

[0096] Referring to Tables 2 to 3, although the pitch of the concave grooves, the width of the concave grooves, the thickness of the adhesive layer, and the depth of the concave grooves usually also affect the performance of the lithium-ion battery, as can be seen from Examples 1 to 25, when W≧S×T1 / 1000 is satisfied, by controlling the above parameters within the scope of the present application, a lithium-ion battery having excellent cycle stability and safety can be obtained.

[0097] Although the cross-sectional area of the concave grooves usually also affects the performance of the lithium-ion battery, as is clear from Examples 13 to 15, when 0.3×(W×H)<A<0.95×(W×H) is satisfied, by controlling the above parameters within the scope of the present application, a lithium-ion battery having excellent cycle stability and safety can be obtained.

[0098] Although the structure of the adhesive layer in the separator, the type of polymer in the adhesive layer, and the type of heat-resistant material in the heat-resistant material layer usually affect the performance of the lithium-ion battery, as can be seen from Examples 26 to 27, when W≧S×T1 / 1000 is satisfied, by controlling the above parameters within the scope of the present application, a lithium-ion battery having excellent cycle stability and safety can be obtained.

[0099] In this specification, relational terms such as "1st," "2nd," etc., are used solely to distinguish one entity or operation from another, and do not necessarily imply that any actual relationship or order exists between these entities or operations. Furthermore, "includes," "contains," or any other variation thereof is intended to mean non-exclusive inclusion. Thus, a process, method, article, or apparatus that includes a set of elements includes not only those elements but also other elements not explicitly listed, or further elements specific to that process, method, article, or apparatus.

[0100] Unless further restrictions are imposed, an element limited by the phrase "including one..." does not preclude the presence of other identical elements in a process, method, article, or apparatus that includes that element. The foregoing are merely preferred embodiments of this application and do not limit it. Any modifications, substitutions with equivalents, improvements, etc., made within the spirit and principles of this application shall all be within the scope of protection of this application. [Explanation of Symbols]

[0101] 10 Electrode Assembly 20 Positive electrode plate 21 Positive electrode current collector 22 Cathode active material layer 30 Negative electrode plate 31 Negative electrode current collector 32 Negative electrode active material layer 40 Separators 41 Base material layer 42 Heat-resistant material layer 321 Groove 431 Adhesive layer 3211 First Segment 3212 Second Segment 3213 Third Segment

Claims

1. Equipped with an electrode assembly, The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is provided between the positive electrode plate and the negative electrode plate. The aforementioned negative electrode plate includes a negative electrode current collector and a negative electrode active material layer. A groove is formed on the surface of the negative electrode active material layer facing the positive electrode plate, the width of the groove is W mm, and the pitch of the groove is S mm. The thickness of the electrode assembly is T １ mm, and W ≥ S × T １ A secondary battery characterized by satisfying the condition / 1000.

2. The secondary battery according to claim 1, characterized in that W ≤ 2 × S × T1.

3. S×T １ / 400≦W≦S×T １ The secondary battery according to claim 1, characterized in that it is / 2.

4. Satisfying at least one of the following conditions: (a) 0.05≦S≦10, (b) The secondary battery according to claim 1, characterized in that 0.02 ≤ W ≤ 0.

5.

5. The OI value of the negative electrode plate and S satisfy S / OI ≤ 0.

5. Here, the OI value = C ００４ / C １１０ , C ００４ This is the peak area obtained from the (004) plane diffraction pattern in the X-ray diffraction pattern, C １１０ The secondary battery according to claim 1, characterized in that is the peak area obtained from the (110) plane diffraction pattern in the X-ray diffraction pattern.

6. The secondary battery according to claim 5, characterized in that 0.005 ≤ S / OI ≤ 0.03 and 8 ≤ OI ≤ 25.

7. An adhesive layer is provided on the surface of the separator facing the negative electrode plate, and the adhesive layer contains a polymer. The secondary battery according to claim 1, characterized in that the polymer content is 30% to 100% based on the mass of the adhesive layer.

8. The secondary battery according to claim 7, characterized in that the adhesive force between the separator and the negative electrode plate is FN / m and F > 3.

9. The thickness of the adhesive layer is T ２ μm, the depth of the concave groove is H μm, and H ≤ T ２ + 20, and the secondary battery according to claim 7, characterized in that it satisfies the above conditions.

10. The cross-sectional area of ​​the groove is A μm ２ The secondary battery according to claim 9, wherein the following conditions are met: 0.3 × (W × H) < A < 0.95 × (W × H), where 2 ≤ H ≤ 50.

11. The secondary battery according to claim 10, characterized in that it satisfies 0.35 × (W × H) < A < 0.8 × (W × H).

12. The secondary battery according to claim 7, characterized in that the polymer includes at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene copolymer, polyacrylonitrile, butadiene-acrylonitrile polymer, polyacrylic acid, polyacrylic acid ester, and acrylic acid ester-styrene copolymer.

13. Along the width direction of the negative electrode plate, the groove portion forms a structure that penetrates the negative electrode plate. Here, the groove has a width W. １ The first segment is W ２ The second segment is 1.2 < W １ / W ２ A secondary battery according to claim 1, which satisfies 1.

8.

14. The secondary battery according to claim 1, characterized in that the groove forms a structure that does not penetrate the negative electrode plate along the width direction of the negative electrode plate.

15. An electronic device characterized by comprising a secondary battery as described in any one of claims 1 to 14.

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