A negative electrode sheet, electrode assembly, battery cell, battery, and electric device

Abstract

The application relates to a negative electrode sheet, an electrode sheet assembly, a battery monomer, a battery and an electric equipment, and belongs to the technical field of secondary batteries. The negative electrode sheet comprises a copper foil, and the copper foil comprises a surface layer. The surface layer comprises a first (111) crystal face, and the volume of the first (111) crystal face is at least 60%. The copper foil with the first (111) crystal face is used as the negative electrode sheet, the adsorption energy of the (111) crystal face of copper to lithium is about -0.05 eV, the negative electrode sheet can better adsorb lithium ions, the adsorption energy is low, the diffusion capacity of lithium ions on the surface of the negative electrode sheet is improved, and the formation of lithium dendrites is reduced. When the volume ratio of the first (111) crystal face reaches a certain degree, the point of strong adsorption of lithium ions on the surface of the negative electrode sheet is reduced, and the possibility of lithium dendrite formation is reduced. Meanwhile, the elongation rate of the copper foil is not less than 3.73%, the tensile strength is not less than 35.4 kg / mm 2 and the requirements of being directly used as an electrode sheet can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a negative electrode sheet, an electrode sheet assembly, a battery monomer, a battery, and an electric device. BACKGROUND

[0002] In the use process of a conventional secondary battery, lithium dendrites are prone to be generated on the surface of the negative electrode sheet when the charging current exceeds the lithium precipitation window or overcharging. The continuous growth of the lithium dendrites leads to the consumption of active lithium, thereby reducing the first coulombic efficiency and cycle performance of the secondary battery. Moreover, when the lithium dendrites grow to a certain extent, they will pierce the separator, leading to internal short circuit of the battery cell and causing thermal runaway of the battery cell. SUMMARY

[0003] In view of the above problems, the present application provides a negative electrode sheet, an electrode sheet assembly, a battery monomer, a battery, and an electric device, which can improve the problem that lithium dendrites are prone to be formed on the surface of the negative electrode sheet.

[0004] In a first aspect, the embodiments of the present application provide a negative electrode sheet, which comprises a copper foil, and the copper foil comprises a surface layer; the surface layer comprises a first (111) crystal face, and the volume of the first (111) crystal face accounts for at least 60% of the volume of the entire surface layer; the elongation of the copper foil is not less than 3.73%; and the tensile strength of the copper foil is not less than 35.4 kg / mm 2 .

[0005] In the technical scheme of the embodiments of the present application, the copper foil with the first (111) crystal face is used as the negative electrode sheet. The adsorption energy of the (111) crystal face of copper to lithium is about -0.05 eV, which is within the suitable range of theoretical calculation of the adsorption energy required for lithium ion adsorption: -0.1 eV-0.1 eV, so that the negative electrode sheet can achieve better adsorption of lithium ions. Meanwhile, the adsorption energy is lower than that of the (100) crystal face of the conventional copper foil to lithium, which can improve the diffusion capacity of lithium ions on the surface of the negative electrode sheet, thereby reducing the formation of lithium dendrites. Moreover, by controlling the volume ratio of the first (111) crystal face of the surface layer of the copper foil to reach a certain degree, the point of strong adsorption of lithium ions on the surface of the negative electrode sheet can be reduced, thereby reducing the possibility of the occurrence of lithium dendrites on the entire surface of the negative electrode sheet. Meanwhile, the elongation of the copper foil is not less than 3.73%, and the tensile strength of the copper foil is not less than 35.4 kg / mm 2 , which can meet the requirements of being directly used as an electrode sheet.

[0006] In some embodiments, the volume of the first (111) crystal face accounts for at least 80% of the volume of the entire surface layer.

[0007] In the above implementation process, the greater the volume ratio of the first (111) crystal face, the fewer the points of strong adsorption of lithium ions on the surface of the negative electrode sheet, and the lower the possibility of the occurrence of lithium dendrites on the entire surface of the negative electrode sheet.

[0008] In some embodiments, the elongation of the copper foil is 3.73% to 6.98%; the tensile strength of the copper foil is 35.4 to 39.2 kg / mm 2 .

[0009] In the above implementation process, when the battery is continuously used, lithium ions are deposited on the surface of the negative plate, which can cause relatively large extension and is more likely to cause copper foil rupture after cycling. Controlling the elongation and tensile strength of the copper foil can reduce the possibility of copper foil rupture.

[0010] In some embodiments, the elongation of the copper foil is 4.28% to 5.93%; the tensile strength of the copper foil is 36.8 to 37.9 kg / mm 2 .

[0011] In some embodiments, the copper foil further comprises a support layer, the support layer comprises a second (111) crystal face and a (220) crystal face, and the surface layer is arranged on at least one surface of the support layer.

[0012] In the above implementation process, the support layer can provide better mechanical properties for the entire copper foil. The more the second (111) crystal face, the more conducive to the tensile strength of the entire copper foil, and the more the (220) crystal face, the more conducive to the elongation of the entire copper foil. The support layer having both the second (111) crystal face and the (220) crystal face can make the entire copper foil have a certain tensile strength and elongation.

[0013] In some embodiments, the thickness Ts of the surface layer satisfies the following relationship: 0.05 μm≤Ts≤1 μm.

[0014] In the above implementation process, since the surface layer mainly has the first (111) crystal face, the first (111) crystal face will have an adverse effect on the elongation of the entire copper foil. The thicker the surface layer, the more the first (111) crystal face, which in turn leads to a lower elongation of the negative plate using the copper foil, which is prone to cracking during use. The thinner the surface layer, the more difficult it is to make the surface layer have better uniformity on the support layer during its preparation, which affects the performance of the surface layer in resisting lithium dendrites.

[0015] In some embodiments, the thickness Ts of the surface layer satisfies the following relationship: 0.1 μm≤Ts≤0.5 μm.

[0016] In the above implementation process, controlling the thickness Ts of the surface layer to be between 0.1 and 0.5 μm can make the entire copper foil have better elongation, and can be more evenly distributed on the surface of the entire support layer, so as to fully exert its anti-lithium dendrite performance.

[0017] In some embodiments, the ratio of the volume ratio x of the second (111) crystal plane to the volume of the entire support layer and the volume ratio y of the (220) crystal plane to the volume of the entire support layer satisfies: x+y≥70%, 0.8≤x / y≤1.2.

[0018] In the above implementation process, by controlling x+y≥70%, 0.8≤x / y≤1.2, the entire copper foil can take into account the tensile strength performance and elongation performance, and thus can be better used as a negative electrode sheet to meet the performance requirements of the negative electrode sheet.

[0019] In some embodiments, the ratio of the volume ratio x of the second (111) crystal plane to the volume of the entire support layer and the volume ratio y of the (220) crystal plane to the volume of the entire support layer satisfies: x+y≥80%, 0.9≤x / y≤1.1.

[0020] In some embodiments, the thickness Tb of the support layer satisfies the following relationship: 4μm≤Tb≤12μm.

[0021] In the above implementation process, when the negative electrode sheet is continuously used in the battery, lithium ions are deposited on its surface, which can cause relatively large extension. Controlling the thickness of the support layer to be between 4μm and 12μm can reduce the possibility of cracking of the entire copper foil during use, while taking into account the energy density of the copper foil as a sheet applied to the battery.

[0022] In some embodiments, the thickness Tb of the support layer satisfies the following relationship: 6μm≤Tb≤10μm.

[0023] In a second aspect, the embodiments of the present application provide a negative electrode sheet, which includes a copper foil, the copper foil including a support layer and a surface layer; the surface layer is arranged on at least one surface of the support layer; the thickness Ts of the surface layer satisfies the following relationship: 0.05μm≤Ts≤1μm, the surface layer includes a first (111) crystal plane, the volume of the first (111) crystal plane accounts for at least 60% of the volume of the entire surface layer; the thickness Tb of the support layer satisfies the following relationship: 4μm≤Tb≤12μm, the support layer includes a second (111) crystal plane and a (220) crystal plane, the ratio of the volume ratio x of the second (111) crystal plane to the volume of the entire support layer and the volume ratio y of the (220) crystal plane to the volume of the entire support layer satisfies: x+y≥70%, 0.8≤x / y≤1.2.

[0024] In the technical scheme of the embodiment of the present application, the occurrence of lithium dendrites can be prevented by controlling the crystal face of the surface layer in the negative plate. Meanwhile, by controlling the thickness of the surface layer, the thickness of the support layer and the crystal face of the support layer, the copper foil has good tensile strength and elongation, thereby reducing the possibility of cracking when used as a negative plate. In addition, the battery using the copper foil as a negative plate can have a good energy density.

[0025] In a third aspect, the embodiment of the present application provides a pole piece assembly, the pole piece assembly comprising a separator film and a positive pole piece and a negative pole piece arranged on two surfaces of the separator film respectively, the surface of the negative pole piece facing the separator film having a copper foil, the copper foil comprising a surface layer; the surface layer comprising a first (111) crystal face, the volume of the first (111) crystal face accounting for at least 60% of the volume of the entire surface layer.

[0026] In the technical scheme of the embodiment of the present application, the copper foil with the first (111) crystal face is used as the negative pole piece, the adsorption energy of the (111) crystal face of copper to lithium is about -0.05eV, which is in the suitable range of theoretical calculation of adsorption energy required for lithium ion adsorption: -0.1eV~0.1eV, which can realize good adsorption of lithium ions by the negative pole piece. At the same time, the adsorption energy is lower than that of the (100) crystal face of the conventional copper foil to lithium, which can improve the diffusion ability of lithium ions on the surface of the negative pole piece, thereby reducing the formation of lithium dendrites. And by controlling the volume ratio of the first (111) crystal face of the surface layer of the copper foil to a certain extent, the point of strong adsorption of lithium ions on the surface of the negative pole piece can be reduced, thereby reducing the possibility of the occurrence of lithium dendrites on the surface of the entire negative pole piece.

[0027] In a fourth aspect, the embodiment of the present application provides a battery monomer, the battery monomer comprising the negative pole piece provided in the first aspect or the second aspect or the pole piece assembly provided in the third aspect.

[0028] In a fifth aspect, the embodiment of the present application provides a battery, the battery comprising the battery monomer provided in the third aspect.

[0029] In a sixth aspect, the embodiment of the present application provides a power consumption device, the power consumption device comprising the battery monomer provided in the fourth aspect or the battery provided in the fifth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are intended to further assist in understanding the preferred embodiments, and are consequently included herewith. Like reference numerals denote like parts throughout the various drawings. In the drawings:

[0031] Figure 1A structural schematic diagram of a vehicle provided for some embodiments of the present application;

[0032] Figure 2 A structural schematic diagram of a battery provided for some embodiments of the present application;

[0033] Figure 3 A structural schematic diagram of a battery cell provided for some embodiments of the present application;

[0034] Figure 4 An exploded view of a battery cell provided for some embodiments of the present application;

[0035] Figure 5 A structural schematic of a positive electrode sheet provided for some embodiments of the present application Figure 1 ;

[0036] Figure 6 A structural schematic of a positive electrode sheet provided for some embodiments of the present application Figure 2 ;

[0037] Figure 7 A scanning electron microscope image of a positive electrode sheet provided for some embodiments of the present application;

[0038] Figure 8 A structural schematic diagram of an electrode assembly provided for some embodiments of the present application.

[0039] Reference signs in the detailed description of the embodiments are as follows:

[0040] 1000-vehicle; 100-battery; 200-motor; 300-controller; 10-box body; 11-accommodation space; 12-first part; 13-second part; 20-battery cell; 21-outer shell; 211-opening; 22-end cover assembly; 221-end cover; 222-electrode terminal; 23-electrode assembly; 231-negative electrode sheet; 2311-supporting layer; 2312-surface layer; 24-current collecting member; 25-insulating protection piece. Detailed description of the embodiments

[0041] The embodiments of the technical solutions of the present application will be described in detail below in conjunction with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments of the present application, and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0043] In the description of the embodiments of the present application, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise explicitly specified and limited.

[0044] Reference herein to "embodiments" means that the particular features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily a separate or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0045] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects.

[0046] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), and similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0047] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0048] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection", "fixing", and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0049] At present, from the development of market situation, the application of power battery is more and more extensive. Power battery is not only applied to energy storage power supply system such as hydroelectric, thermal, wind and solar power station, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, military equipment and aerospace and other fields. With the continuous expansion of the application field of power battery, the market demand is also increasing.

[0050] The power battery can be a lithium ion battery, which has a very wide application in portable electronic devices, electric vehicles and other fields. The copper foil surface of the negative electrode sheet of the conventional secondary battery has a large area of (100) crystal face, and the adsorption energy of copper (100) crystal face to lithium is about -0.23eV, which exceeds the suitable range of theoretical calculation of adsorption energy required for lithium ion adsorption: -0.1eV~0.1eV, which is relatively strong to lithium ion, which is not conducive to the diffusion of lithium on the surface of copper foil. During the use of the secondary battery, lithium dendrites are easily generated on the surface of the negative electrode sheet 231 when the charging current exceeds the lithium precipitation window or overcharging. The continuous growth of lithium dendrites leads to the consumption of active lithium, thereby reducing the first coulomb efficiency and cycle performance of the secondary battery. Moreover, when the lithium dendrites grow to a certain extent, they will pierce the separator, causing internal short circuit of the battery cell and leading to thermal runaway of the battery cell.

[0051] In order to reduce the possibility of lithium dendrite formation on the surface of the negative electrode sheet 231, a three-dimensional structure can be loaded on the surface of the copper foil of the negative electrode sheet 231. The three-dimensional structure has a large surface area, which can reduce the average current density, disperse the electric field, promote the uniform deposition of lithium ions, and further reduce the possibility of lithium dendrite formation. However, the three-dimensional structure occupies a large space, which causes waste of the volume of the battery cell and reduces the energy density of the battery 100. At the same time, the three-dimensional structure is hollow, which has low strength and reduces the strength of the entire negative electrode sheet 231. In addition, the material of the three-dimensional structure is often different from that of the copper foil, which makes the preparation difficult.

[0052] In order to improve the problem that lithium dendrites are easily formed on the surface of the negative electrode sheet 231 under the premise of small volume and high strength, the copper crystal face type on the surface of the copper foil can be adjusted to reduce the adsorption of lithium ions. The adsorption energy of copper (111) crystal face to lithium is about -0.05eV, which is lower than that of the conventional copper foil (100) crystal face to lithium, which can reduce the possibility of lithium ion diffusion on the surface of the negative electrode sheet 231. At the same time, the adsorption energy is in the suitable range of theoretical calculation of adsorption energy required for lithium ion adsorption: -0.1eV~0.1eV, which can realize good adsorption of lithium ions by the negative electrode sheet 231.

[0053] Based on the above considerations, the application provides a negative plate 231, which comprises a copper foil, the copper foil comprising a support layer 2311 and a surface layer 2312; the surface layer 2312 is arranged on at least one surface of the support layer 2311; the thickness Ts of the surface layer 2312 satisfies the following relationship: 0.05 μm≤Ts≤1 μm, the surface layer 2312 comprises a first (111) crystal face, and the volume of the first (111) crystal face accounts for at least 60% of the volume of the entire surface layer 2312; the thickness Tb of the support layer 2311 satisfies the following relationship: 4 μm≤Tb≤12 μm, the support layer 2311 comprises a second (111) crystal face and a (220) crystal face, and the relationship between the volume ratio x of the second (111) crystal face to the volume of the entire support layer 2311 and the volume ratio y of the (220) crystal face to the volume of the entire support layer 2311 satisfies the following relationship: x+y≥70%, 0.8≤x / y≤1.2.

[0054] In the negative plate 231, the copper foil with the first (111) crystal face is used as the negative plate 231, the adsorption energy of the (111) crystal face of copper to lithium is about -0.05 eV, which is in the suitable range of theoretical calculation of the adsorption energy required for lithium ion adsorption: -0.1 eV-0.1 eV, so that the negative plate 231 can better adsorb lithium ions. Meanwhile, the adsorption energy is lower than the adsorption energy of the (100) crystal face of the conventional copper foil to lithium, which can improve the diffusion capacity of lithium ions on the surface of the negative plate 231, thereby reducing the formation of lithium dendrites. By controlling the volume ratio of the first (111) crystal face of the surface layer 2312 of the copper foil to a certain extent, the point of strong adsorption of lithium ions on the surface of the negative plate 231 can be reduced, thereby reducing the possibility of lithium dendrites on the surface of the negative plate 231. In addition, the copper foil has good mechanical properties, and when it is used as the negative plate 231, the negative plate 231 can reduce the possibility of cracking after cycling.

[0055] The negative plate 231 can be used to prepare an electrode assembly 23, which can be used in an electric device such as a vehicle 1000, a ship or an aircraft, but is not limited thereto. The power supply system of the electric device can be composed of the battery monomer 20, the battery 100 and the like disclosed in the application, so that the possibility of lithium dendrites on the surface of the negative plate 231 is reduced, the volume of the negative plate 231 can be better controlled, and the strength of the negative plate 231 can be maintained, thereby improving the energy density, service life and other performances of the battery monomer 20.

[0056] The embodiments of the present application provide a power consumption device using a battery as a power supply. The power consumption device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship, a spacecraft and the like. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy and an electric aircraft toy and the like. The spacecraft can include an airplane, a rocket, a space shuttle and a spacecraft and the like.

[0057] The following embodiments are described by taking a power consumption device in an embodiment of the present application as a vehicle 1000 for example for convenience of description.

[0058] Please refer to Figure 1 , Figure 1 A structural schematic diagram of the vehicle 1000 is provided for some embodiments of the present application. The vehicle 1000 can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile and the like. The vehicle 1000 is internally provided with a battery 100, which can be arranged at the bottom, the head or the tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as an operating power supply of the vehicle 1000. The vehicle 1000 can further include a controller 300 and a motor 200, and the controller 300 is used to control the battery 100 to supply power to the motor 200, for example, to meet the working power demand of the vehicle 1000 during starting, navigation and driving.

[0059] In some embodiments of the present application, the battery 100 can not only be used as an operating power supply of the vehicle 1000, but also be used as a driving power supply of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1000.

[0060] In the present application, the battery 100 can refer to a single battery monomer, which can also refer to a single physical module including a plurality of battery monomers 20 to provide higher voltage and capacity, which can be in the form of a battery pack, a battery module and the like. The battery 100 can include a box 10 for packaging a plurality of battery monomers 20, and the box 10 can avoid the influence of liquid or other foreign matters on the charging or discharging of the battery monomers 20.

[0061] Figure 2 A disassembled structural schematic diagram of the battery 100 is provided for some embodiments of the present application. Please refer to Figure 2 , the battery 100 includes a box 10 and a battery monomer 20, and the battery monomer 20 is accommodated in the box 10.

[0062] The box 10 is used to provide a containing space 11 for the battery cell 20. In some embodiments, the box 10 can include a first part 12 and a second part 13, the first part 12 and the second part 13 are mutually covered to define the containing space 11 for containing the battery cell 20. Of course, the connection between the first part 12 and the second part 13 can be sealed by a sealing member (not shown in the figure), which can be a sealing ring, sealing glue, etc.

[0063] The first part 12 and the second part 13 can be various shapes, such as a cuboid, a cylinder, etc. The first part 12 can be a hollow structure with one side open to form a containing cavity for containing the battery cell 20, and the second part 13 can also be a hollow structure with one side open to form a containing cavity for containing the battery cell 20, and the open side of the second part 13 covers the open side of the first part 12, thereby forming the box 10 with the containing space 11. Of course, as shown in the figure, the first part 12 can be a hollow structure with one side open, and the second part 13 can be a plate structure, and the second part 13 covers the open side of the first part 12, thereby forming the box 10 with the containing space 11. Figure 2

[0064] In the battery 100, the battery cell 20 can be one or multiple. If the battery cell 20 is multiple, the multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection, where the mixed connection means that some of the multiple battery cells 20 are connected in series and some are connected in parallel. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and then the whole of the multiple battery cells 20 is contained in the box 10; of course, the multiple battery cells 20 can first be connected in series, in parallel, or in a mixed connection to form a battery module, and then multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, which is contained in the box 10. The battery cell 20 can be in the shape of a cylinder, a flat body, a cuboid, or other shapes, etc. Figure 2 An example is shown in which the battery cell 20 is in the shape of a square.

[0065] In some embodiments, the battery 100 can further include a current collecting member (not shown in the figure), and the multiple battery cells 20 can be electrically connected through the current collecting member to achieve the series connection, parallel connection, or mixed connection of the multiple battery cells 20.

[0066] Figure 3 A structural schematic diagram of the battery cell 20 provided by some embodiments of the present application is shown in the figure, Figure 4 An exploded view of the battery cell 20 provided by some embodiments of the present application is shown in the figure. Please refer to Figure 3 and Figure 4 The battery cell 20 can include a shell 21, an end cap assembly 22, and an electrode assembly 23. The shell 21 has an opening 211, the electrode assembly 23 is contained in the shell 21, and the end cap assembly 22 is used to cover the opening 211. ​

[0067] The shape of the shell 21 can be determined according to the specific shape of the electrode assembly 23. For example, if the electrode assembly 23 is a cuboid structure, the shell 21 can also be a cuboid structure. Figure 3 and Figure 4 Exemplarily, the shell 21 and the electrode assembly 23 are square.

[0068] The material of the shell 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not make special limitations on this.

[0069] The end cover assembly 22 includes an end cover 221 and an electrode terminal 222. The end cover assembly 22 is used to cover the opening 211 of the shell 21 to form a sealed mounting space (not shown in the figure), which is used to accommodate the electrode assembly 23. The mounting space is also used to accommodate the electrolyte, such as electrolyte solution. As a component for outputting the electrical energy of the electrode assembly 23, the electrode terminal 222 in the end cover assembly 22 is used to be electrically connected with the electrode assembly 23, that is, the electrode terminal 222 is electrically connected with the tab of the electrode assembly 23, for example, the electrode terminal 222 is connected with the tab through the current collecting member 24 to realize the electrical connection between the electrode terminal 222 and the tab.

[0070] It should be noted that the opening 211 of the shell 21 can be one or two. If the opening 211 of the shell 21 is one, the end cover assembly 22 can also be one, and two electrode terminals 222 can be arranged in the end cover assembly 22, which are respectively used to be electrically connected with the positive tab and the negative tab of the electrode assembly 23. If the opening 211 of the shell 21 is two, for example, the two openings 211 are arranged at the opposite sides of the shell 21, and the end cover assembly 22 can also be two, which are respectively covered at the two openings 211 of the shell 21. In this case, the electrode terminal 222 in one end cover assembly 22 can be a positive electrode terminal, which is used to be electrically connected with the positive tab of the electrode assembly 23, and the electrode terminal 222 in the other end cover assembly 22 can be a negative electrode terminal, which is used to be electrically connected with the negative tab 231 of the electrode assembly 23.

[0071] In some embodiments, as shown in Figure 4 The battery monomer 20 can also include an insulating protective member 25 fixed to the outer periphery of the electrode assembly 23, which is used to insulate and isolate the electrode assembly 23 from the shell 21. Exemplarily, the insulating protective member 25 is an adhesive tape adhered to the outer periphery of the electrode assembly 23. In some embodiments, the number of the electrode assemblies 23 is multiple, the insulating protective member 25 is arranged around the outer periphery of the multiple electrode assemblies 23, and the multiple electrode assemblies 23 form an integral structure to maintain the structural stability of the electrode assemblies 23.

[0072] Please refer to Figure 8The electrode assembly 23 includes a positive electrode sheet, a negative electrode sheet 231, and a separator. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on a surface of the positive electrode current collector. The positive electrode current collector, which is not coated with the positive electrode active material layer, protrudes from the positive electrode current collector coated with the positive electrode active material layer, and serves as a positive electrode tab.

[0073] The negative electrode sheet 231 can be in a form including only a metal foil, which can be a copper foil. To ensure that no fusing occurs even when a large current is passed, the number of positive electrode tabs is plural and stacked together, and the number of negative electrode tabs is plural and stacked together.

[0074] The separator can be made of PP (polypropylene), PE (polyethylene), or the like.

[0075] In addition, the electrode assembly 23 can be a wound-type electrode assembly 23 or a stacked-type electrode assembly 23, and the embodiments of the present application are not limited thereto.

[0076] Figure 5 Structure of the negative electrode sheet 231 according to some embodiments of the present application Figure 1 , Figure 6 Structure of the negative electrode sheet 231 according to some embodiments of the present application Figure 2 ; see Figure 5 and Figure 6 The negative electrode sheet 231 according to some embodiments of the present application includes a copper foil including a surface layer 2312, the surface layer 2312 including a first (111) crystal plane, the volume of the first (111) crystal plane being at least 60% of the volume of the entire surface layer 2312, the elongation of the copper foil being not less than 3.73%, and the tensile strength of the copper foil being not less than 35.4 kg / mm 2 .

[0077] A crystal plane refers to a plane passing through the centers of atoms in crystallography. A crystal can develop a polyhedral shape composed of planes of different orientations during self-growth. The planes in these polyhedral shapes are referred to as crystal planes.

[0078] The calculation of the volume ratio of the crystal plane to the entire surface layer 2312 can be as follows: XRD tests are performed on the copper foil to be calculated and a standard copper powder to obtain the crystal plane diffraction intensity I (hkl) of the copper foil to be calculated and the crystal plane diffraction intensity I 0(hkl) of the standard copper powder, and then the following formula is used for calculation:

[0079]

[0080] The elongation is the percentage of the total deformation of the gauge length section after the sample is stretched to break relative to the original gauge length L: δ = ΔL / L x 100%.

[0081] The tensile strength is the critical value of the transition from uniform plastic deformation to local concentrated plastic deformation of the metal, and is also the maximum load capacity of the metal under static tension. The tensile strength represents the resistance of the maximum uniform plastic deformation of the material. Before the tensile sample bears the maximum tensile stress, the deformation is uniform and consistent, but after that, the necking phenomenon occurs, that is, concentrated deformation occurs. For brittle materials without (or with little) uniform plastic deformation, it reflects the fracture resistance of the material.

[0082] By adopting the copper foil with the first (111) crystal face as the negative plate 231, the adsorption energy of the (111) crystal face of copper to lithium is about -0.05 eV, which is in the suitable range of theoretical calculation of the adsorption energy required for lithium ion adsorption: -0.1 eV-0.1 eV, which can realize better adsorption of lithium ions by the negative plate 231. At the same time, the adsorption energy is lower than the adsorption energy of the (100) crystal face of the conventional copper foil to lithium, which can improve the diffusion ability of lithium ions on the surface of the negative plate 231, thereby reducing the formation of lithium dendrites. And by controlling the volume ratio of the first (111) crystal face of the surface layer 2312 of the copper foil to reach a certain degree, the point of strong adsorption of lithium ions on the surface of the negative plate 231 can be reduced, thereby reducing the possibility of lithium dendrites on the surface of the entire negative plate 231. At the same time, the elongation of the copper foil is not less than 3.73%, and the tensile strength of the copper foil is not less than 35.4 kg / mm 2 , which can meet the requirements of being directly used as a plate.

[0083] In the technical scheme of the embodiment of the application, the volume of the first (111) crystal face accounts for at least 80% of the volume of the entire surface layer 2312. The greater the volume ratio of the first (111) crystal face, the fewer the points of strong adsorption of lithium ions on the surface of the negative plate 231, and the less likely the lithium dendrites on the surface of the entire negative plate 231.

[0084] In the technical scheme of the embodiment of the application, the elongation of the copper foil is 3.73%-6.98%, and the tensile strength of the copper foil is 35.4-39.2 kg / mm 2 . Optionally, the elongation of the copper foil is 4.28%-5.93%, and the tensile strength of the copper foil is 36.8-37.9 kg / mm 2 .

[0085] When the negative plate 231 is continuously used in the battery 100, lithium ions are deposited on its surface, which can cause relatively large extension of the negative plate 231, and the copper foil is more likely to break after cycling. Controlling the elongation and tensile strength of the copper foil can reduce the possibility of copper foil breakage.

[0086] For example, the elongation of the copper foil can be 3.73%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, and 6.98%, etc., which can also be any value in the range of 3.73% to 6.98%. The tensile strength of the copper foil can be 35.4 kg / mm 2 , 35.5 kg / mm 2 , 36 kg / mm 2 , 36.5 kg / mm 2 , 37 kg / mm 2 , 37.5 kg / mm 2 , 38 kg / mm 2 , 38.5 kg / mm 2 , 39 kg / mm 2 , and 39.2 kg / mm 2 , etc., which can also be any value in the range of 35.4 to 39.2 kg / mm 2 .

[0087] The copper foil further comprises a support layer 2311 comprising a second (111) crystal plane and a (220) crystal plane, and a surface layer 2312 disposed on at least one surface of the support layer 2311.

[0088] The surface layer 2312 disposed on at least one surface of the support layer 2311 means that the surface layer 2312 can be disposed on any surface of the support layer 2311, or can be disposed on both opposite surfaces of the support layer 2311. Please continue to refer to Figure 5 In one embodiment, the surface layer 2312 is disposed on one surface of the support layer 2311. Please continue to refer to Figure 6 In another embodiment, the surface layer 2312 is disposed on both surfaces of the support layer 2311.

[0089] The support layer 2311 can provide good mechanical properties to the entire copper foil. The more the second (111) crystal plane, the more conducive to the tensile strength of the entire copper foil, and the more the (220) crystal plane, the more conducive to the elongation of the entire copper foil. The support layer 2311 having both the second (111) crystal plane and the (220) crystal plane can make the entire copper foil have a certain tensile strength and elongation.

[0090] In the technical solution of the embodiment of the present application, the thickness Ts of the surface layer 2312 satisfies the following relationship: 0.05 μm≤Ts≤1 μm. When the battery 100 is used continuously, lithium ions are deposited on the surface of the negative plate 231, which may cause relatively large extension. Since the surface layer 2312 mainly has the first (111) crystal face, the first (111) crystal face will have an adverse effect on the elongation of the entire copper foil. The thicker the surface layer 2312 is, the more the first (111) crystal face is, which further leads to that the elongation of the negative plate 231 using the copper foil is low, and the negative plate 231 is prone to cracking during use. The thinner the surface layer 2312 is, the more difficult it is to make the surface layer 2312 have better uniformity on the support layer 2311 during preparation of the surface layer 2312, which affects the performance of the surface layer 2312 in resisting lithium dendrites.

[0091] Optionally, the thickness Ts of the surface layer 2312 satisfies the following relationship: 0.1 μm≤Ts≤0.5 μm. Controlling the thickness Ts of the surface layer 2312 to be between 0.1 μm and 0.5 μm can make the entire copper foil have better elongation, and can be more uniformly distributed on the surface of the entire support layer 2311, so as to fully exert the performance of the surface layer 2312 in resisting lithium dendrites.

[0092] For example, the thickness Ts of the surface layer 2312 can be 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm and 1 μm, etc. It can also be any other value in the range of 0.05 μm to 1 μm.

[0093] In the technical solution of the embodiment of the present application, the support layer 2311 includes the second (111) crystal face and the (220) crystal face. The more the second (111) crystal face is, the more beneficial to the tensile strength of the entire copper foil, and the more the (220) crystal face is, the more beneficial to the elongation of the entire copper foil. The support layer 2311 having the second (111) crystal face and the (220) crystal face at the same time can make the entire copper foil have certain tensile strength and elongation.

[0094] In the technical solution of the embodiment of the present application, the relationship between the ratio x of the volume of the second (111) crystal plane to the volume of the entire support layer 2311 and the ratio y of the volume of the (220) crystal plane to the volume of the entire support layer 2311 satisfies x+y≥70%, 0.8≤x / y≤1.2. Alternatively, the relationship between the ratio x of the volume of the second (111) crystal plane to the volume of the entire support layer 2311 and the ratio y of the volume of the (220) crystal plane to the volume of the entire support layer 2311 satisfies x+y≥80%, 0.9≤x / y≤1.1. By controlling x+y≥70%, 0.8≤x / y≤1.2, the entire copper foil can balance the tensile strength performance and the elongation rate performance, thereby being better used as the negative plate 231 to meet the performance requirements of the negative plate 231.

[0095] For example, the sum of the ratio x of the volume of the second (111) crystal plane to the volume of the entire support layer 2311 and the ratio y of the volume of the (220) crystal plane to the volume of the entire support layer 2311 can satisfy x+y=70%, x+y=72%, x+y=75%, x+y=78%, x+y=80%, x+y=83%, x+y=85%, x+y=87%, x+y=90%, x+y=92%, x+y=95%, x+y=97%, x+y=100%, etc., which can also be any value greater than or equal to 70%; the ratio of the volume of the second (111) crystal plane to the volume of the entire support layer 2311 to the ratio of the volume of the (220) crystal plane to the volume of the entire support layer 2311 can satisfy x / y=0.8, x / y=0.85, x / y=0.9, x / y=0.95, x / y=1, x / y=1.05, x / y=1.1, x / y=1.15, and x / y=1.2, etc., which can also be any value in the range of 0.8-1.2.

[0096] In the technical solution of the embodiment of the present application, the thickness Tb of the support layer 2311 satisfies the following relationship: 4μm≤Tb≤12μm. Alternatively, the thickness Tb of the support layer 2311 satisfies the following relationship: 6μm≤Tb≤10μm. When the lithium ions are deposited on the surface of the negative plate 231 during the continuous use of the battery 100, the extension of the negative plate 231 can be relatively large. Controlling the thickness of the support layer 2311 to be between 4-12μm can reduce the possibility of cracking of the entire copper foil during use, while the energy density of the battery 100 can be considered.

[0097] For example, the thickness Tb of the support layer 2311 can be 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, etc., which can also be any value in the range of 4-12μm.

[0098] It should be noted that when determining the thickness Ts of the surface layer 2312 of the product negative electrode and the thickness Tb of the support layer 2311, it can be obtained by measuring the scanning electron microscope image of its cross section, as shown in Figure 7 Meanwhile, when detecting the crystal face of the support layer 2311, after the thickness of the surface layer 2312 is determined, the surface layer 2312 corresponding to the thickness is removed by mechanical polishing or the like, and then XRD testing is performed to obtain.

[0099] After the foregoing introduces the material and structure of the negative electrode sheet 231, the preparation method of the negative electrode sheet 231 will be specifically introduced below.

[0100] When the copper foil is of the structure shown in Figure 5 , that is, only the surface layer 2312 is arranged on one surface of the support layer 2311, the preparation process can be that the support layer 2311 is prepared first, and then the surface layer 2312 is prepared on the surface of the support layer 2311. Alternatively, the surface layer 2312 can be prepared first, and then the support layer 2311 is prepared on the surface of the surface layer 2312.

[0101] The preparation of the support layer 2311 can be prepared by electrodeposition, and the specific process is as follows: step 1) dissolving copper sulfate pentahydrate with deionized water, and adding a small amount of concentrated sulfuric acid to prepare an electrolyte with a pH value of 0.9-1.1 and a copper sulfate content of 240-260 g / L; step 2) applying a pulse current for electrodeposition with a copper sheet as an anode and a titanium sheet as a cathode, and the electrodeposition parameter ranges are respectively a deposition current density of 0.5 A / cm 2 , a deposition time of 50 ms, a deposition standing time of 50-80 ms, an oxidation current density of 0.05 A / cm 2 , an oxidation time of 20 ms, an oxidation standing time of 20 ms, and a cycle of 2400-7200 times to obtain different thicknesses; step 3) taking out the cathode and cleaning it alternately with dilute sulfuric acid and deionized water to obtain a copper foil with a highly preferred orientation of crystal face.

[0102] The preparation of the support layer 2311 can be prepared by electrodeposition, and the specific process is as follows: step 1) dissolving copper sulfate pentahydrate with deionized water, and adding a small amount of concentrated sulfuric acid to prepare an electrolyte with a pH value of 0.9-1.1 and a copper sulfate content of 240-260 g / L; step 2) applying a pulse current for electrodeposition with a copper sheet as an anode and a titanium sheet as a cathode, and the electrodeposition parameter ranges are respectively a deposition current density of 0.5 A / cm 2 , a deposition time of 50 ms, a deposition standing time of 0-20 ms, an oxidation current density of 0.05 A / cm 2, oxidation time 20 ms, oxidation standing time 20 ms, cycle 30-600 times to obtain different thicknesses; step 3): the cathode is taken out and cleaned alternately with dilute sulfuric acid and deionized water to obtain a copper foil with a high degree of crystal plane preferred orientation.

[0103] After the negative sheet 231 is prepared, the first separator film, the positive sheet, the second separator film, and the negative sheet 231 are sequentially stacked, wound to form a wound flat structure, and then heat-pressed to obtain a wound electrode assembly 23; or, after the positive sheet is prepared, the positive sheet, the separator film, the negative sheet 231, the separator film, and so on are sequentially stacked to form a laminated electrode assembly 23.

[0104] The electrode assembly 23 can be used to prepare a battery monomer 20, which can be used to prepare a battery 100 and provide electrical energy for an electrical device.

[0105] One or more embodiments will be described in more detail below with reference to the following examples. Of course, these examples do not limit the scope of one or more embodiments.

[0106] Examples and Comparative Examples

[0107]

Preparation of the positive sheet

[0108] The positive active material, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are added to N-methyl pyrrolidone (NMP) at a weight ratio of 96:2:2, stirred and mixed uniformly to obtain a coating layer slurry; then the slurry is uniformly coated on the positive current collector at a mass of 280 mg / 1540.25 mm 2 , and dried to obtain a positive sheet.

[0109]

Preparation of the negative sheet 231

[0110] A copper foil with a support layer 2311 and a surface layer 2312 arranged on both surfaces of the support layer 2311 is prepared by electrodeposition, and the copper foil is mechanically cut to obtain a negative sheet 231.

[0111]

Preparation of the electrolyte

[0112] In an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), organic solvents 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) are mixed uniformly at a volume ratio of 1:1, 1 mol / L lithium salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is added and uniformly dispersed, and 2 wt% lithium nitrate (LiNO3) is dissolved in the above organic solvents as an additive, stirred uniformly, and an electrolyte is obtained.

[0113]

Separator film

[0114] A polypropylene film is used as the separator film.

[0115]

Preparation of lithium ion battery

[0116] The above positive electrode sheet, separator film, and negative electrode sheet 231 are stacked in order with the separator film between the positive and negative electrode sheets 231 to play a role of separation, and then wound to obtain a bare battery cell. The bare battery cell is welded with tabs, and is loaded into an aluminum case, and is baked at 80°C to remove water. Then, an electrolyte is injected and sealed to obtain a non-charged battery. The non-charged battery is sequentially subjected to processes of standing, hot and cold pressing, formation, shaping, capacity testing, and the like to obtain a lithium ion battery product.

[0117] The main parameters of each example and comparative example are controlled as shown in the following table:

[0118]

[0119]

[0120] It should be noted that the entire copper foil of Comparative Example 1 has only one layer, which is counted as the surface layer in the table.

[0121] The tensile strength and elongation of the negative electrode sheet 231 provided by each example and comparative example are tested, then the energy density of the battery 100 provided by each example and comparative example is tested, then the cycle is carried out according to the process of 1C / 1C charge and discharge, and the cycle number is recorded. After the attenuation to 80% SOH, the morphology of lithium deposition on the negative electrode sheet 231 is confirmed by disassembly.

[0122] The tensile strength test process is as follows: the test sample copper foil is cut into 100*15mm pieces with a knife die, then the pieces are fixed and clamped vertically to the high-iron tension machine clamp with the initial height of the clamp being 5cm, the tensile rate is set to 50mm / min, the maximum tension F is measured, and the maximum tension F is brought into the following formula: tensile strength = F / 9.8 / (15mm*T), wherein T is the thickness of the test sample copper foil, to obtain the tensile strength.

[0123] The elongation test process is as follows: first, the extensometer is installed on the tensile testing machine, then the test sample copper foil is installed in the clamp, the initial position of the extensometer is calibrated, then the testing machine is operated to break the test sample copper foil, and the elongation of the metal is read.

[0124] The test process of the energy density test is as follows: charging at a constant current of 1C to a voltage of 4.35 V, then charging at a constant voltage of 4.35 V to a current of 0.05C, at this time the lithium ion battery 100 reaches a full charge state, then standing for 5 min, discharging at a constant current of 1C to a voltage of 2.8 V, then standing for 5 min, recording the energy of the lithium ion battery 100 at the time of 1C constant current discharge, and finally measuring the mass of the lithium ion battery 100. According to the obtained data, the energy density (Wh / kg) of the lithium ion battery 100 is calculated according to the following formula: energy density (Wh / kg) of the lithium ion battery 100 = energy of the lithium ion battery 100 at the time of 1C constant current discharge / mass of the lithium ion battery 100, to obtain the energy density.

[0125] The results are shown in the following table:

[0126]

[0127]

[0128] It should be noted that in the table, no dendrite means that the area of dendrite appearance accounts for 0% of the entire negative electrode sheet surface area; partial dendrite means that the area of dendrite appearance accounts for 0-20% of the entire negative electrode sheet surface area, and dendrite means that the area of dendrite appearance accounts for more than 20% of the entire negative electrode sheet surface area.

[0129] From the above table, it can be obtained by comparing the examples and the comparative examples that increasing the volume ratio of the copper (111) crystal plane of the surface layer 2312 can improve the problem of lithium dendrite generation. It can be obtained by comparing the data of examples 1-3 and comparative example 2 that when the volume ratio of the copper (111) crystal plane of the surface layer 2312 reaches 60%, the effect of inhibiting lithium dendrite can be achieved. At the same time, when the entire copper foil meets the requirements of elongation not less than 3.6% and tensile strength not less than 35 kgf, the mechanical property requirements of directly serving as a negative electrode sheet can be met, and the probability of cracking of the negative electrode sheet during use can be effectively reduced.

[0130] By comparing Example 1, 4 to 6 and Comparative Example 7, it can be seen that when the thickness of the surface layer 2312 is less than 0.05 μm, partial lithium dendrites appear and the life of the battery 100 is significantly shortened. The inventor analyzes that the reason is that the surface layer 2312 is too thin and it is difficult to be uniformly distributed on the support layer 2311 due to the current technical limitations, which leads to the generation of lithium dendrites. Therefore, when the technology advances to the point that the thinner surface layer 2312 can be uniformly distributed on the support layer 2311, the surface layer 2312 can be made thinner without being limited by this, and the effect of inhibiting lithium dendrites is still good. When the thickness of the surface layer 2312 is greater than 1 μm, the elongation of the entire copper foil is less than 3.5% and the copper foil cracks after cycling. It can be seen that the thickness of the surface layer 2312 is preferably controlled between 0.05 and 1 μm. When the thickness of the surface layer 2312 is between 0.05 and 0.2 μm, the copper (111) crystal plane of the surface layer 2312 hardly affects the performance of the entire copper foil and has a good effect of inhibiting lithium dendrites.

[0131] By comparing Example 1, 7 to 8 and Comparative Examples 4 to 5, it can be seen that as the ratio of the proportion of the copper (111) crystal plane to the copper (220) crystal plane increases, the tensile strength of the entire copper foil gradually increases, while the elongation of the entire copper foil gradually decreases. When the ratio of the proportion of the copper (111) crystal plane to the copper (220) crystal plane is less than 0.8 or greater than 1.2, the copper foil cracks after cycling. It can be seen that the ratio of the proportion of the copper (111) crystal plane to the copper (220) crystal plane is preferably controlled between 0.5 and 1.2.

[0132] By comparing Example 1, 9 to 10 and Comparative Example 6, it can be seen that as the sum of the proportions of the copper (111) crystal plane and the copper (220) crystal plane increases, the tensile strength and elongation of the entire copper foil gradually increase. When the sum of the proportions of the copper (111) crystal plane and the copper (220) crystal plane is less than 60%, the copper foil cracks after cycling. It can be seen that the sum of the proportions of the copper (111) crystal plane and the copper (220) crystal plane is preferably greater than 60%.

[0133] By comparing Example 1, 11 to 13 and Comparative Example 7, it can be seen that when the thickness of the support layer 2311 is less than 4, the copper foil cracks after cycling. When the thickness of the support layer 2311 is greater than 12, although the life of the battery 100, the state of the copper foil after cycling and the lithium deposition morphology are all in good condition, the energy density of the battery 100 is less than 300 Wh / kg, which is relatively low. It can be seen that the thickness of the support layer 2311 is preferably controlled between 4 and 12 μm.

[0134] The above merely provides specific examples of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall fall into the scope of protection of the present application.

Claims

1. A negative electrode sheet, characterized in that, The negative electrode includes a copper foil, which comprises a surface layer and a support layer. The surface layer is disposed on at least one surface of the support layer. The surface layer includes a first (111) crystal plane, the volume of which is at least 60% of the total volume of the surface layer. The thickness Ts of the surface layer satisfies the following relationship: 0.05μm≤Ts≤1μm. The support layer includes a second (111) crystal plane and a (220) crystal plane. The thickness Tb of the support layer satisfies the following relationship: 4μm≤Tb≤12μm. The elongation of the copper foil is not less than 3.73%. The tensile strength of the copper foil is not less than 35.4kg / mm². 2 .

2. The negative electrode sheet according to claim 1, characterized in that, The volume of the first (111) crystal plane accounts for at least 80% of the total volume of the surface layer.

3. The negative electrode sheet according to claim 1, characterized in that, The elongation of the copper foil is 3.73%~6.98%; and / or The tensile strength of the copper foil is 35.4~39.2 kg / mm². 2 .

4. The negative electrode sheet according to claim 3, characterized in that, The elongation of the copper foil is 4.28%~5.93%; and / or The tensile strength of the copper foil is 36.8~37.9 kg / mm². 2 .

5. The negative electrode sheet according to claim 1, characterized in that, The thickness Ts of the surface layer satisfies the following relationship: 0.1μm≤Ts≤0.5μm.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that, The relationship between the ratio x of the volume of the second (111) crystal plane to the total volume of the support layer and the ratio y of the volume of the (220) crystal plane to the total volume of the support layer satisfies: x + y ≥ 70% and 0.8 ≤ x / y ≤ 1.

2.

7. The negative electrode sheet according to claim 6, characterized in that, The relationship between the volume of the second (111) crystal plane as a percentage of the total volume of the support layer, x, and the volume of the (220) crystal plane as a percentage of the total volume of the support layer, y, satisfies the following: x + y ≥ 80%, 0.9 ≤ x / y ≤ 1.

1.

8. The negative electrode sheet according to claim 1, characterized in that, The thickness Tb of the support layer satisfies the following relationship: 6μm≤Tb≤10μm.

9. An electrode assembly, characterized in that, The electrode assembly includes a separator and positive electrode sheets respectively disposed on two surfaces of the separator and a negative electrode sheet as described in any one of claims 1 to 8.

10. A single battery cell, characterized in that, The battery cell includes the negative electrode sheet according to any one of claims 1 to 8 or the electrode assembly according to claim 9.

11. A battery, characterized in that, The battery comprises the battery cell of claim 10.

12. An electrical appliance, characterized in that, The electrical equipment includes the battery cell of claim 10 or the battery of claim 11.

Images