Battery cell components, battery cells, batteries and electrical devices

Abstract

The present application relates to a battery cell assembly, a battery cell, a battery and an electrical device, wherein the battery cell assembly includes a multi-layer material coating, each of which is coated on one side of each negative electrode sheet facing the adjacent diaphragm; wherein one or more adjacent layers of the material coating constitute a coating group, and the volume expansion rate of each coating group gradually decreases from the inside to the outside of the battery cell assembly after winding. In the present application, since the volume expansion rate of each coating group gradually decreases from the inside to the outside, when the battery cell assembly is in the process of cyclic use, the volume expansion rate of the inner circle layer is higher than that of the outer circle layer, and the inner circle layer has more lithium insertion sites that can be used to accommodate lithium ions than the outer circle layer. When lithium ions migrate from the positive electrode to the adjacent negative electrode, more lithium ions can be embedded in the negative electrode, thereby avoiding the precipitation of excess lithium ions due to the inability to embed, thereby solving the problem of lithium precipitation in the battery and improving the cycle performance of the battery.

Description

Technical Field

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

[0002] The battery cell assembly is formed by winding the positive electrode sheet, the negative electrode sheet and the diaphragm. The battery cell assembly is the component where the electrochemical reaction occurs in the battery. When the battery is in circulation, lithium ions will be embedded and de-embedded between the positive and negative electrode sheets. When lithium ions migrate from the positive electrode to the negative electrode, the positive-negative electrode capacity ratio is insufficient in the area where the positive electrode wraps around the negative electrode in the corner of the battery cell assembly. Among them, too many lithium ions from the positive electrode are embedded in the negative electrode, and the negative electrode does not have enough capacity to meet the embedding of lithium ions, resulting in the precipitation of excess lithium ions in the area where the inner positive electrode wraps around the negative electrode, which seriously reduces the cycle performance of the battery. Summary of the invention

[0003] Based on this, it is necessary to provide a battery cell assembly, a battery cell, a battery and an electrical device to address the problem of lithium plating in batteries.

[0004] In a first aspect, the present application provides a battery cell assembly, comprising a plurality of positive electrode sheets, a plurality of negative electrode sheets, and a plurality of separators, wherein each positive electrode sheet and each negative electrode sheet are alternately stacked, each separator is disposed between each two adjacent positive electrode sheets and negative electrode sheets, and all positive electrode sheets, all negative electrode sheets, and all separators are wound in the same direction. In addition, the battery cell assembly further comprises a plurality of material coatings, each material coating being coated on a surface of each negative electrode sheet facing the separator adjacent thereto;

[0005] Among them, one layer or multiple adjacent layers of material coatings constitute a coating group, and the volume expansion rate of each coating group gradually decreases from the inside to the outside of the wound battery cell assembly.

[0006] Therefore, relative to a certain coating group, the coating group located in the inner circle has a larger volume expansion rate, so there are more lithium insertion sites available for embedding lithium ions, thus avoiding the problem of lithium plating, thereby improving the cycle performance of the battery cell assembly.

[0007] In some embodiments, each material coating is a silicon material coating, and the silicon content of each coating group gradually decreases from the inside to the outside of the wound battery cell assembly.

[0008] On the one hand, silicon materials have more lithium insertion sites than current graphite substrates, so that the lithium precipitation phenomenon can be improved from the material itself. On the other hand, silicon materials have a larger volume expansion rate than graphite substrates. The larger the volume expansion rate, the more lithium insertion sites it has for inserting lithium ions, thereby preventing lithium ions from being precipitated due to the inability to insert. In addition, the higher the silicon content, the greater the volume expansion rate. Therefore, by controlling the silicon content in each coating group, the volume expansion rate of each coating group is controlled, so that different coating groups have different lithium insertion capabilities according to demand, reducing the probability of lithium precipitation.

[0009] In some embodiments, the silicon material in each silicon material coating layer includes one or more of nano-silicon, silicon carbide, silicon oxide, and silicon alloy.

[0010] In some embodiments, the gram capacity of the silicon material in each silicon material coating layer ranges from 350 mAh / g to 4000 mAh / g.

[0011] By controlling the gram capacity range of silicon material in each layer of silicon material coating, the coating quality of the silicon material coating can be controlled, thereby controlling the thickness of the negative electrode sheet after coating the silicon material coating, effectively controlling the energy density of the battery cell assembly, and further improving the energy density of the battery.

[0012] In some embodiments, the mass percentage of silicon in each silicon material coating is 1%-100%. By controlling the mass percentage of silicon in each layer of silicon material coating, the volume expansion rate of different silicon material coatings can be adjusted, so that the silicon material coatings in different layers have corresponding lithium insertion capabilities according to actual needs, avoiding the occurrence of lithium precipitation.

[0013] In some embodiments, each negative electrode sheet includes a graphite substrate layer, and the mass ratio of each silicon material coating layer to the graphite substrate layer in the adjacent negative electrode sheet is 0.1%-10%.

[0014] On the one hand, by controlling the mass ratio of each layer of silicon material coating and the graphite substrate layer in the adjacent negative electrode sheet, the common thickness of each layer of silicon material coating and the adjacent negative electrode sheet can be controlled, thereby avoiding excessive thickness of the negative electrode sheet after the silicon material coating is applied, which affects the energy density of the battery cell assembly. On the other hand, by controlling the mass ratio of each layer of silicon material coating and the graphite substrate layer in the adjacent negative electrode sheet, the lithium insertion capacity of the negative electrode sheet after each layer of silicon material coating is applied can be regulated, so that the lithium insertion capacity of the negative electrode sheet just matches the amount of lithium ion precipitation. Therefore, on the basis of satisfying the complete embedding of lithium ions without lithium precipitation, the thickness of the negative electrode sheet is not increased, thereby improving the energy density of the battery.

[0015] In some embodiments, during the discharge process of the battery cell assembly, lithium is embedded in each material coating, and the thickness difference between the innermost material coating and the outermost material coating after the lithium embedding is greater than or equal to 3 μm. By controlling the thickness difference between the innermost and outermost material coatings after the lithium embedding, the stress can be adjusted.

[0016] In some embodiments, during the discharge process of the battery cell assembly, lithium is embedded in each material coating, and the thickness difference between the innermost material coating and the outermost material coating after lithium embedding is greater than or equal to 5 μm. Thus, it can be ensured that each material coating at different positions has sufficient lithium embedding sites, ensuring that lithium ions are embedded smoothly and avoiding the phenomenon of lithium precipitation.

[0017] In some embodiments, the battery cell assembly is formed with a corner portion and a horizontal portion, and each material coating is disposed between each negative electrode sheet of the corner portion and the separator adjacent thereto.

[0018] As for the corners, the positive electrode sheet covers the negative electrode sheet, resulting in a smaller area where the negative electrode sheet and the positive electrode sheet face each other. Therefore, applying each layer of material coating between each layer of negative electrode sheet and the adjacent separator in the corner can provide more lithium insertion sites and improve the lithium precipitation phenomenon.

[0019] In some embodiments, the capacity excess coefficient ratio of the corner portion to the horizontal portion ranges from 1.001 to 1.5, wherein the capacity excess coefficient is the ratio of the active material capacity of the negative electrode sheet to the positive electrode sheet per unit area facing each other.

[0020] By controlling the capacity excess coefficient ratio of the corner part and the horizontal part, the ratio of the number of lithium ions released by the positive electrode active material to the number of lithium ions embedded in the negative electrode active material can be controlled, ensuring that the negative electrode has enough lithium insertion sites to accommodate all the lithium ions released from the positive electrode, thereby avoiding the problem of lithium plating.

[0021] In a second aspect, the present application provides a battery cell, comprising a housing and the battery cell assembly as described above, wherein the battery cell assembly is accommodated in the housing.

[0022] In a third aspect, the present application provides a battery, comprising the battery cell as described above.

[0023] In a fourth aspect, the present application provides an electrical device comprising the battery as described above.

[0024] The above-mentioned battery cell components, battery cells, batteries and electrical devices, since the volume expansion rate of each coating group gradually decreases from the inside to the outside, when the battery cell components are in the process of cyclic use, the volume expansion rate of the inner layer is higher than that of the outer layer, and the inner layer has more lithium insertion sites that can be used to accommodate lithium ions than the outer layer. When lithium ions migrate from the positive electrode to the adjacent negative electrode, more lithium ions can be embedded in the negative electrode, thereby avoiding the precipitation of excess lithium ions due to the inability to embed, thereby solving the problem of battery lithium precipitation and improving the battery cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0026] Figure 2 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0027] Figure 3 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0028] Figure 4 A schematic cross-sectional structure diagram of a battery cell assembly according to some embodiments of the present application;

[0029] Figure 5 A partial cross-sectional view of a battery cell assembly according to some embodiments of the present application;

[0030] In the figure: 1000, vehicle; 100, battery; 200, controller; 300, motor; 10, housing; 20, battery cell; 11, first part; 12, second part; 21, end cover; 22, shell; 23, battery cell assembly; 231, positive electrode sheet; 232, negative electrode sheet; 233, diaphragm; 234, material coating; 235, corner portion; 236, horizontal portion; 21a, electrode terminal; 23a, pole ear. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0032] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0033] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0034] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0036] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0037] At present, from the perspective of market development, the application of power batteries is becoming more and more extensive. Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.

[0038] During the use of the battery, it needs to be charged and discharged. During the charge and discharge cycle, the positive electrode active material and the negative electrode active material embed or extract ions. For the wound battery cell assembly, the area where the positive electrode covers the negative electrode at the corner has an insufficient capacity ratio due to the bending. As a result, too many lithium ions in the positive electrode at the corner are embedded in the negative electrode, and the negative electrode does not have enough lithium insertion sites to accommodate all the lithium ions, resulting in the excess lithium ions being unable to be embedded and precipitated, affecting the battery's cycle performance.

[0039] Furthermore, in order to prevent lithium ion precipitation, the positive and negative electrode capacity ratio of the battery can be increased. However, if the positive and negative electrode capacity ratio is too large, although lithium precipitation can be avoided during the use of the battery, it will lead to a thicker battery cell assembly, thereby reducing the energy density of the battery.

[0040] Based on the above considerations, in order to solve the problem of lithium plating during battery recycling without reducing the energy density of the battery, the applicant has designed a battery cell assembly after in-depth research, in which a material coating is applied between the negative electrode sheet and the adjacent separator, and the volume expansion rate of each coating group is gradually reduced from the inside to the outside, so that the negative electrode sheet coated in the corresponding positive electrode sheet has a larger volume expansion rate, thereby having more lithium insertion sites for embedding more lithium ions, avoiding the problem of lithium plating in the battery and improving the battery's cycle performance.

[0041] The battery cell disclosed in the embodiment of the present application can be used in, but not limited to, electric devices such as vehicles, ships or aircraft. The electric device using a battery as a power source provided in the embodiment of the present application can be, but not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, an electric airplane toy, etc., and the spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0042] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0043] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0044] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0045] Please refer to Figure 2 , Figure 2An exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. Among them, the box 10 is used to provide a storage space for the battery cell 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0046] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0047] Each battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0048] Please refer to Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery. Figure 3 The battery cell 20 includes an end cover 21, a shell 22, a battery cell assembly 23 and other functional components.

[0049] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the battery cell assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0050] The shell 22 is a component used to cooperate with the end cover 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the battery cell assembly 23, electrolyte and other components. The shell 22 and the end cover 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cover 21 at the opening. Without limitation, the end cover 21 and the shell 22 can also be integrated. Specifically, the end cover 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cover 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the battery cell assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0051] The battery cell assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more battery cell assemblies 23 may be contained in the housing 22. The battery cell assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the battery cell assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab. The positive tab and the negative tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tab 23a connects the electrode terminal 21a to form a current loop.

[0052] See also Figure 4 and Figure 5 , Figure 4 A schematic cross-sectional structure diagram of a battery cell assembly provided in some embodiments of the present application, Figure 5 A partial cross-sectional view of a battery cell assembly provided for some embodiments of the present application. One embodiment of the present application provides a battery cell assembly 23, including a plurality of positive electrode sheets 231, a plurality of negative electrode sheets 232, and a plurality of separators 233. Each positive electrode sheet 231 and each negative electrode sheet 232 are alternately stacked, and each separator 233 is arranged between each two adjacent positive electrode sheets 231 and negative electrode sheets 232, and all positive electrode sheets 231, all negative electrode sheets 232, and all separators 233 are wound in the same direction. In addition, the battery cell assembly 23 also includes a multilayer material coating 234, and each material coating 234 is coated on one side surface of each negative electrode sheet 232 facing the separator 233 adjacent thereto. Among them, one or adjacent multilayer material coatings 234 constitute a coating group, and the volume expansion rate of each coating group gradually decreases from the inside to the outside of the battery cell assembly 23 after winding.

[0053] It should be noted that a material coating 234 is coated between each layer of the negative electrode sheet 232 and the adjacent separator 233, that is, a material coating 234 is coated on the surface of one side of each layer of the negative electrode sheet 232 facing the adjacent separator 233. When a layer of material coating 234 constitutes a coating group, it means that the volume expansion rate of each layer of the material coating 234 located in the outer circle is smaller than that of the material coating 234 in the adjacent inner circle. When two or more adjacent layers of material coatings 234 constitute a coating group, the volume expansion rate of each material coating 234 in each coating group can be equal, and the volume expansion rate of each coating group located in the outer circle is smaller than that of the coating group in the adjacent inner circle.

[0054] Furthermore, in the process of coating the material coating 234, the coating method can be coating, and of course, it can also be sprayed or plated, etc., which will not be described in detail here.

[0055] Specifically, for the battery cell assembly 23 after winding, the volume expansion rate of each coating group gradually decreases from the inside to the outside, that is, the volume expansion rate between each coating group decreases according to a certain coefficient. By controlling the decreasing coefficient, the volume expansion rate of each coating group can be regulated, thereby achieving stress regulation between each coating group, which plays a role in reducing lithium precipitation.

[0056] In addition, compared with a certain coating group, the coating group located in the inner circle has a larger volume expansion rate, so there are more lithium insertion sites that can be used to embed lithium ions, avoiding the problem of lithium plating, thereby improving the cycle performance of the battery cell assembly 23.

[0057] In some embodiments, each layer of material coating 234 is a silicon material coating 234, and the silicon content of each coating group gradually decreases from the inside to the outside of the wound battery cell assembly 23.

[0058] On the one hand, since the current negative electrode sheet 232 substrate is mostly made of graphite substrate, when the material coating 234 is made of silicon material coating 234, due to its own structural characteristics, the silicon material has more lithium insertion sites compared to the graphite substrate, thereby being able to improve the lithium precipitation phenomenon from the material itself.

[0059] On the other hand, silicon material has a larger volume expansion rate than graphite substrate. The larger the volume expansion rate, the more lithium insertion sites it has for embedding lithium ions, thereby preventing lithium ions from precipitating due to the inability to embed.

[0060] Furthermore, the silicon content of each coating group gradually decreases from the inside to the outside, and the more silicon content, the greater the volume expansion rate. Therefore, by controlling the silicon content in each coating group, the volume expansion rate of each coating group is controlled, so that different coating groups have different lithium insertion capabilities according to needs, reducing the probability of lithium precipitation.

[0061] The silicon material in each layer of silicon material coating 234 includes one or more of nano silicon, silicon carbide, silicon oxide, and silicon alloy.

[0062] The silicon material in the silicon material coating 234 can be a material containing lithium-intercalated active silicon such as nano-silicon, silicon carbide, silicon oxide or silicon alloy, wherein the metal in the silicon alloy can be iron, aluminum, nickel, tin or other metals. That is, the active components in the silicon material coating 234 can include multiple types. For example, the active material component in the silicon material coating 234 can be a mixture of artificial graphite, silicon oxide, a conductive agent and an adhesive, and the content of silicon oxide is 50%. Specifically, a suitable active component can be selected according to actual needs, which will not be described in detail here.

[0063] In some embodiments, the gram capacity of the silicon material in each layer of the silicon material coating 234 is in the range of 350 mAh / g-4000 mAh / g.

[0064] As a specific embodiment, when the gram capacity of the silicon material in the silicon material coating 234 is 350 mAh / g, the coating mass of the silicon material coating 234 is 40 mg / 1540.25 mm 2 At this time, the gram capacity of graphite in the negative electrode graphite substrate layer is 355 mAh / g, and the coating mass of the graphite substrate layer is 123 mg / 1540.25 mm 2 Therefore, the gram capacity of the active material on the positive electrode sheet 231 is 195 mAh / g, and the coating mass is 0.195 mg / 1540.25 mm 2 .

[0065] As a specific embodiment, when the gram capacity of the silicon material in the silicon material coating 234 is 1000 mAh / g, the coating mass of the silicon material coating 234 is 20 mg / 1540.25 mm 2 At this time, the gram capacity of graphite in the negative electrode graphite substrate layer is 355 mAh / g, and the coating mass of the graphite substrate layer is 123 mg / 1540.25 mm 2 Therefore, the gram capacity of the active material on the positive electrode sheet 231 is 195 mAh / g, and the coating mass is 0.195 mg / 1540.25 mm 2 .

[0066] As a specific embodiment, when the gram capacity of the silicon material in the silicon material coating 234 is 4000 mAh / g, the coating mass of the silicon material coating 234 is 5 mg / 1540.25 mm 2 At this time, the gram capacity of graphite in the negative electrode graphite substrate layer is 355 mAh / g, and the coating mass of the graphite substrate layer is 123 mg / 1540.25 mm 2 Therefore, the gram capacity of the active material on the positive electrode sheet 231 is 195 mAh / g, and the coating mass is 0.195 mg / 1540.25 mm 2 .

[0067] By controlling the gram capacity range of the silicon material in each layer of the silicon material coating 234, the coating quality of the silicon material coating 234 can be controlled, thereby controlling the thickness of the negative electrode sheet 232 after coating the silicon material coating 234, effectively controlling the energy density of the battery cell assembly 23, and further improving the energy density of the battery 100.

[0068] In some embodiments, the mass percentage of silicon in each layer of silicon material coating 234 is 1%-100%. Since the mass percentage of silicon will directly affect the volume expansion rate of the silicon material coating 234, that is, the larger the mass percentage of silicon, the larger the volume expansion rate of the silicon material coating 234, and vice versa.

[0069] Therefore, by controlling the mass proportion of silicon elements in each layer of silicon material coating 234, the volume expansion rate of different silicon material coatings 234 can be adjusted, so that the silicon material coatings 234 in different layers have corresponding lithium insertion capabilities according to actual needs, avoiding lithium precipitation.

[0070] In some embodiments, each negative electrode sheet 232 includes a graphite substrate layer (not shown in the figure), and the mass ratio of each silicon material coating layer 234 to the graphite substrate layer in the adjacent negative electrode sheet 232 is 0.1%-10%.

[0071] On the one hand, by controlling the mass ratio of each layer of silicon material coating 234 and the graphite substrate layer in the adjacent negative electrode sheet 232, the common thickness of each layer of silicon material coating 234 and the adjacent negative electrode sheet 232 can be controlled, thereby avoiding the negative electrode sheet 232 being too thick after coating the silicon material coating 234, thereby affecting the energy density of the battery cell assembly 23.

[0072] On the other hand, by controlling the mass ratio of each silicon material coating 234 and the graphite substrate layer in the adjacent negative electrode sheet 232, the lithium insertion capacity of the negative electrode sheet 232 after each silicon material coating 234 is regulated, so that the lithium insertion capacity of the negative electrode sheet 232 is exactly matched with the amount of lithium ion precipitation. Thus, on the basis of satisfying the complete insertion of lithium ions without lithium precipitation, the thickness of the negative electrode sheet 232 is not increased, thereby improving the energy density of the battery 100.

[0073] In some embodiments, during the discharge process of the battery cell assembly 23 , lithium is embedded in each layer of the material coating 234 , and after the lithium is embedded, the thickness difference between the innermost material coating 234 and the outermost material coating 234 is greater than or equal to 3 μm.

[0074] Specifically, due to the different silicon material contents in different material coatings 234, the volume expansion rates of different material coatings 234 are different. During the discharge process of the battery cell assembly 23, lithium is embedded in each layer of the material coating 234 and the negative electrode sheet 232, and the thickness will be different after the lithium is embedded. By controlling the thickness difference between the innermost circle and the outermost circle of the material coating 234 after the lithium is embedded, the stress is adjusted.

[0075] In addition, when the thickness difference between the innermost circle material coating 234 and the outermost circle material coating 234 after lithium insertion is greater than or equal to 3 μm, it can ensure that each material coating 234 at different positions has sufficient lithium insertion sites, ensuring the smooth insertion of lithium ions and avoiding the occurrence of lithium precipitation.

[0076] As a preferred embodiment, the thickness difference between the innermost circle material coating 234 and the outermost circle material coating 234 after lithium insertion is greater than or equal to 5 μm, which can ensure that each material coating 234 at different positions has sufficient lithium insertion sites, ensure the smooth insertion of lithium ions, and avoid lithium precipitation.

[0077] In some embodiments, the battery cell assembly 23 is formed with a corner portion 235 and a horizontal portion 236 , and each layer of the material coating 234 is disposed between each layer of the negative electrode sheet 232 of the corner portion 235 and the separator 233 adjacent thereto.

[0078] Since the battery cell assembly 23 is formed by stacking multiple layers of negative electrode sheets 232, multiple layers of separators 233 and multiple layers of positive electrode sheets 231 in sequence and winding in the same direction, the battery cell assembly 23 is formed with a corner portion 235 and a horizontal portion 236. The corner portion 235 can be defined as the range of the arc tops on both sides of the battery cell assembly 23 extending 10mm to the left and right 20mm.

[0079] For the horizontal portion 236, the positive and negative electrode sheets 232 face the same area, so the probability of lithium deposition is small. For the corner portion 235, the positive electrode sheet 231 covers the negative electrode sheet 232, resulting in a smaller area for the negative electrode sheet 232 and the positive electrode sheet 231 to face each other. When the lithium ions in the positive electrode sheet 231 are released, there are not enough lithium insertion sites on the negative electrode sheet 232 for embedding all the lithium ions, thus causing lithium deposition.

[0080] Therefore, each layer of material coating 234 is coated between each layer of negative electrode sheet 232 in the corner portion 235 and the adjacent diaphragm 233 , that is, each layer of silicon material coating 234 is coated between each layer of negative electrode sheet 232 in the corner portion 235 and the adjacent diaphragm 233 .

[0081] On the one hand, due to its own material properties, silicon material can provide more lithium insertion sites compared to graphite substrates, so that the negative electrode 232 coated with the silicon material coating 234 has more lithium insertion sites that can embed lithium ions, reducing the probability of lithium precipitation.

[0082] On the other hand, silicon material has a larger volume expansion rate than graphite substrate. When the silicon material coating 234 is coated on the negative electrode sheet 232, the negative electrode sheet 232 has a larger volume expansion rate, thereby providing more lithium insertion sites and improving lithium precipitation.

[0083] Of course, a silicon material coating 234 may also be coated between the negative electrode sheet 232 in the horizontal portion 236 and the adjacent diaphragm 233 . The specific configuration may be made according to actual use requirements and will not be elaborated herein.

[0084] In some embodiments, the capacity excess coefficient ratio of the corner portion 235 to the horizontal portion 236 is in the range of 1.001-1.5, wherein the capacity excess coefficient is the ratio of the active material capacity of the negative electrode sheet 232 to the positive electrode sheet 231 on the unit area facing each other.

[0085] Specifically, the capacity excess coefficient of the horizontal portion 236 can be set to 1.14, and the capacity excess coefficient of the corner portion 235 can be set to 1.19. By controlling the capacity excess coefficient ratio of the corner portion 235 to the horizontal portion 236, the ratio of the number of lithium ions released by the positive electrode active material to the number of lithium ions embedded in the negative electrode active material can be controlled, ensuring that the negative electrode has enough lithium insertion sites to accommodate all lithium ions released from the positive electrode, thereby avoiding the problem of lithium precipitation.

[0086] However, when the capacity excess coefficient ratio of the corner portion 235 to the horizontal portion 236 is too small, the lithium ions released from the positive electrode cannot be completely embedded in the negative electrode, resulting in lithium precipitation. When the capacity excess coefficient ratio of the corner portion 235 to the horizontal portion 236 is too large, there are too many lithium insertion sites in the negative electrode, forming redundancy, resulting in excessive thickness of the battery cell assembly 23, affecting the energy density of the battery 100.

[0087] Therefore, by controlling the capacity excess coefficient ratio of the corner portion 235 to the horizontal portion 236 to be between 1.001 and 1.5, the thickness of the battery cell assembly 23 can be reduced and the energy density of the battery 100 can be improved while ensuring that the lithium ions released from the positive electrode are completely embedded in the negative electrode and lithium plating does not occur.

[0088] Based on the same concept as the above-mentioned battery cell assembly 23 , the present application provides a battery cell 20 , including a housing 22 and the above-mentioned battery cell assembly 23 . The battery cell assembly 23 is accommodated in the housing 22 .

[0089] When the above-mentioned battery cell assembly 23 is applied to the battery cell 20, it can ensure that the negative electrode sheets 232 of different layers from the inside to the outside of the battery cell assembly 23 have sufficient lithium insertion sites for inserting lithium ions released from the adjacent positive electrode sheet 231, thereby avoiding the problem of lithium precipitation. In addition, the silicon content in the silicon material coating 234 gradually decreases from the inside to the outside, so that each layer of the negative electrode sheet 232 has a suitable number of lithium insertion sites, which can avoid the problem of lithium precipitation without increasing the thickness of the negative electrode sheet 232, thereby improving the energy density of the battery cell 20.

[0090] Based on the same concept as the above-mentioned battery cell 20 , the present application provides a battery 100 , including the above-mentioned battery cell 20 .

[0091] When the battery cells 20 are applied to the battery 100, on one hand, each battery cell 20 is not prone to lithium deposition, which is beneficial to improving the cycle capacity of the battery 100. On the other hand, each battery cell 20 has a higher energy density, thereby improving the overall energy density of the battery 100.

[0092] Based on the same concept as the above-mentioned battery 100 , the present application provides an electrical device, including the above-mentioned battery 100 .

[0093] When the battery 100 is used in an electrical device, the battery 100 has a high cycle capacity, which can extend the service life of the electrical device. In addition, the battery 100 has a high energy density, so the overall energy density of the electrical device can be higher, thereby improving the performance of the electrical device.

[0094] When the present application is used specifically, a silicon material coating 234 is coated between each layer of the negative electrode sheet 232 and the adjacent diaphragm 233 in the corner portion 235 of the battery cell assembly 23, and the silicon content of each silicon material coating 234 gradually decreases from the inside to the outside, so that the volume expansion rate of the negative electrode sheet 232 coated with the silicon material coating 234 gradually decreases from the inside to the outside.

[0095] After winding, at the corner 235 of the battery cell assembly 23, the negative electrode sheet 232 located on the inner circle is folded more than the negative electrode sheet 232 located on the outer circle, that is, the number of lithium insertion sites on the negative electrode sheet 232 located on the inner circle is less than that on the negative electrode sheet 232 located on the outer circle.

[0096] Therefore, when the volume expansion rate of the negative electrode sheet 232 coated with the silicon material coating 234 gradually decreases from the inside to the outside, the negative electrode sheet 232 located in the inner circle has more lithium insertion sites than the negative electrode sheet 232 not coated with the silicon material coating 234, and can embed more lithium ions, thereby effectively improving the lithium precipitation phenomenon.

[0097] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A battery cell assembly, comprising a plurality of positive electrode sheets, a plurality of negative electrode sheets and a plurality of separators, wherein each of the positive electrode sheets and each of the negative electrode sheets are alternately stacked, each of the separators is arranged between each two adjacent positive electrode sheets and the negative electrode sheets, and all of the positive electrode sheets, all of the negative electrode sheets and all of the separators are wound in the same direction, characterized in that: The battery core assembly further includes a multi-layer material coating, each of which is coated on a surface of each negative electrode sheet facing the adjacent separator; Wherein, one or more adjacent layers of the material coatings constitute a coating group, and the volume expansion rate of each coating group gradually decreases from the inside to the outside of the wound battery core assembly; Each of the material coatings is a silicon material coating, and the silicon content of each coating group gradually decreases from the inside to the outside of the wound battery core assembly.

2. The battery cell assembly according to claim 1, characterized in that: The silicon material in each of the silicon material coatings includes one or more of nano silicon, silicon carbide, silicon oxide, and silicon alloy.

3. The battery core assembly according to claim 1, characterized in that: The gram capacity of the silicon material in each of the silicon material coatings ranges from 350 mAh / g to 4000 mAh / g.

4. The battery core assembly according to claim 1, characterized in that: The mass percentage of silicon element in each silicon material coating is 1%-100%.

5. The battery core assembly according to claim 1, characterized in that: Each of the negative electrode sheets comprises a graphite substrate layer, and the mass ratio of each of the silicon material coatings to the graphite substrate layer in the negative electrode sheet adjacent thereto is 0.1%-10%.

6. The battery core assembly according to claim 1, characterized in that: During the discharge process of the battery cell assembly, lithium is embedded in each of the material coatings, and after the lithium is embedded, the difference in thickness between the innermost circle of the material coating and the outermost circle of the material coating is greater than or equal to 3 μm.

7. The battery cell assembly according to claim 6, characterized in that: During the discharge process of the battery cell assembly, lithium is embedded in each of the material coatings, and after the lithium is embedded, the difference in thickness between the innermost circle of the material coating and the outermost circle of the material coating is greater than or equal to 5 μm.

8. The battery core assembly according to claim 1, characterized in that: The battery cell assembly is formed with a corner portion and a horizontal portion, and each of the material coatings is arranged between each of the negative electrode sheets at the corner portion and the separator adjacent thereto.

9. The battery core assembly according to claim 8, characterized in that: The capacity excess coefficient ratio of the corner portion to the horizontal portion is in the range of 1.001-1.5, wherein the capacity excess coefficient is the ratio of the active material capacity of the negative electrode sheet to the active material capacity of the positive electrode sheet on the unit area facing each other.

10. A battery cell, characterized in that: It comprises a shell and a battery cell assembly as described in any one of claims 1 to 9, wherein the battery cell assembly is accommodated in the shell.

11. A battery, characterized in that: Comprising the battery cell as claimed in claim 10.

12. An electrical device, characterized in that: Comprising the battery of claim 11.

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