Battery cell, battery, and electric device

Abstract

A battery cell (7), a battery (2), and an electric device. The battery cell (7) includes a case (20) and a positive electrode sheet (11). The case (20) has a melting point of N. The positive electrode sheet (11) is housed in the case (20) and includes a positive electrode active material, the positive electrode active material including lithium nickel cobalt manganese oxide, the weight of nickel elements in the lithium nickel cobalt manganese oxide being G1, the sum of the weights of the nickel elements, cobalt elements, and manganese elements being G2, and the value of G1 / G2 being M. M and N satisfy: 0.1≤M≤0.65, N≥(50M+500)℃; or, M and N satisfy: 0.65<M<1, N≥(950M+500)℃.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery, and an electrical device. Background Technology

[0002] Battery cells are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools, etc.

[0003] In the development of battery technology, improving the safety of individual battery cells is a key research direction. Summary of the Invention

[0004] This application provides a battery cell, a battery, and an electrical device that can improve the safety of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell comprising a casing and a positive electrode. The melting point of the casing is N. The positive electrode is housed within the casing and comprises a positive electrode active material, which includes lithium nickel cobalt manganese oxide. The weight of nickel in the lithium nickel cobalt manganese oxide is G1, and the sum of the weights of nickel, cobalt, and manganese is G2. The value of G1 / G2 is denoted as M. M and N satisfy: 0.1≤M≤0.65, N≥(50M+500)℃; or, M and N satisfy: 0.65<M<1, N≥(950M+500)℃.

[0006] The higher the value of M, the higher the rate of gas generation and the more heat generated by the electrode assembly during thermal runaway, and the higher the melting point required for the casing. Conversely, the lower the value of M, the less heat generated by the battery cell during thermal runaway, and the lower the melting point required for the casing. In the above technical solution, for battery cells satisfying 0.1≤M≤0.65, the melting point of the casing should be at least greater than or equal to (50M+500)℃ to reduce the risk of the casing melting through during battery cell thermal runaway. For battery cells satisfying 0.65<M<1, the melting point of the battery cell casing should be at least greater than or equal to (950M+500)℃ to reduce the risk of the casing melting through during battery cell thermal runaway.

[0007] In some embodiments, M and N satisfy: 0.1≤M≤0.65, N≥(200M+500)℃.

[0008] In some embodiments, M and N satisfy: 0.1≤M≤0.65, (50M+500)℃≤N≤(15000M+500)℃.

[0009] The above technical solution limits the melting point of the outer shell to less than or equal to (15000M+500)℃, which can reduce the excessive design of the melting point of the outer shell and facilitate the selection of outer shell materials.

[0010] In some embodiments, M and N satisfy: 0.65 < M < 1, N ≥ (1000M + 500) °C.

[0011] In some embodiments, M and N satisfy: 0.65 < M < 1, (950M + 500)℃ ≤ N ≤ (3000M + 500)℃.

[0012] The above technical solution will limit the melting point of the outer shell to less than or equal to (3000M+500)℃, which can reduce the excessive design of the melting point of the outer shell and facilitate the selection of outer shell materials.

[0013] In some embodiments, M and N satisfy: N≤(1800M+500)℃.

[0014] In some embodiments, the battery cell further includes a negative electrode sheet housed within a casing. The negative electrode sheet includes a negative electrode active material, which includes graphite and a silicon-containing material. The weight of the silicon-containing material is B1, and the weight of the graphite is B2. The value of B1 / (B1+B2) is denoted as P. P satisfies: 0 < P < 0.6.

[0015] Compared to graphite, silicon-containing materials have a higher specific capacity. The aforementioned technical solution effectively improves the energy density of individual battery cells by replacing some of the graphite with silicon-containing materials. However, silicon-containing materials expand significantly during charging. If the silicon content is too high, it will lead to excessive expansion force in the battery cells during charging, affecting their safety and cycle life. The aforementioned technical solution limits the value of P to greater than 0 and less than 0.6 to balance the energy density and expansion force of the battery cells.

[0016] In some embodiments, the tensile strength of the casing is Q, where Q and M satisfy: 0.1≤M≤0.65, Q≥(50M+50)MPa. For a single battery cell satisfying 0.1≤M≤0.65, the tensile strength of the casing should be at least greater than or equal to (50M+50)MPa to reduce the amount of stretching of the casing during thermal runaway of the battery cell, reduce the risk of casing cracking, and improve safety.

[0017] In some embodiments, Q and M satisfy: 0.1≤M≤0.65, Q≤(1100M+50)MPa. Limiting the tensile strength of the shell to less than or equal to (1100M+50)MPa reduces the excessive design of the shell's tensile strength and facilitates the selection of shell materials.

[0018] In some embodiments, the tensile strength of the casing is Q, where Q and M satisfy: 0.65 < M < 1, Q ≥ (300M + 50) MPa. For a single battery cell satisfying 0.65 < M < 1, the tensile strength of the casing should be at least greater than or equal to (300M + 50) MPa to reduce the amount of stretching of the casing during thermal runaway of the battery cell, reduce the risk of casing cracking, and improve safety.

[0019] In some embodiments, Q and M satisfy: 0.65 < M < 1, Q ≤ (950M + 50) MPa. Limiting the tensile strength of the shell to less than or equal to (950M + 50) MPa reduces the excessive design of the shell's tensile strength and facilitates the selection of shell materials.

[0020] In some embodiments, the housing includes a housing and an end cap, the housing having an opening and the end cap for closing the opening.

[0021] In some embodiments, the wall thickness of the casing is 0.05mm-2mm. The smaller the casing wall thickness, the easier it is for the casing to melt through in the event of thermal runaway of the battery cell; conversely, the larger the casing wall thickness, the greater the weight of the casing and the lower the energy density of the battery cell. The above technical solution sets the casing wall thickness to 0.05mm-2mm to balance the safety and energy density of the battery cell.

[0022] In some embodiments, the housing and end caps are made of the same material.

[0023] In some embodiments, the housing includes two first side plates disposed along a first direction and two second side plates disposed along a second direction, the second side plates connecting the two first side plates, the first direction being perpendicular to the second direction. The ratio of the housing dimension along the second direction to the housing dimension along the first direction is 1-50.

[0024] In some embodiments, the casing is made of steel or nickel. Materials such as steel and nickel have high melting points, which effectively reduces the risk of the casing melting through.

[0025] Secondly, embodiments of this application provide a battery comprising a plurality of battery cells according to any of the embodiments of the first aspect.

[0026] Thirdly, embodiments of this application provide an electrical device including a battery cell according to any of the embodiments of the first aspect, wherein the battery cell is used to provide electrical energy. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0028] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0029] Figure 2 Explosion diagrams of batteries provided for some embodiments of this application;

[0030] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0031] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application;

[0032] Figure 5 A cross-sectional schematic diagram of a battery cell provided in some embodiments of this application;

[0033] Figure 6 This is a schematic diagram of the structure of the positive electrode sheet of a battery cell provided in some embodiments of this application;

[0034] Figure 7 This is a schematic diagram of the structure of the negative electrode sheet of a battery cell provided in some embodiments of this application.

[0035] The reference numerals in the accompanying drawings for the specific embodiments are as follows:

[0036] 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Accommodation space; 6. Battery module; 7. Battery cell; 10. Electrode assembly; 11. Positive electrode sheet; 111. Positive current collector; 112. Positive active material layer; 12. Negative electrode sheet; 121. Negative current collector; 122. Negative active material layer; 13. Separator; 20. Outer shell; 21. Housing; 211. First side plate; 212. Second side plate; 22. End cap; 30. Electrode terminal; D1. First direction; D2. Second direction; D3. Third direction. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] 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 this application pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order or hierarchy.

[0039] In the description of this application, it should be understood that the terms "center", "lateral", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0040] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0041] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0043] In this application, "multiple" means two or more (including two).

[0044] In the embodiments of this application, "parallel" includes not only the case of absolute parallelism, but also the case of approximate parallelism as commonly understood in engineering; similarly, "perpendicular" also includes not only the case of absolute perpendicularity, but also the case of approximate perpendicularity as commonly understood in engineering. For example, if the angle between two directions is 80°-90°, the two directions can be considered perpendicular; if the angle between two directions is 0°-10°, the two directions can be considered parallel.

[0045] In this application, the battery cell may be cylindrical, flat, cuboid or other shapes, and the embodiments of this application are not limited to this.

[0046] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack. A battery generally includes a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0047] A single battery cell includes electrode components and an electrolyte. The electrode components include a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrode components. The positive electrode includes a positive current collector and a positive active material layer, with the active material layer coated on the surface of the current collector. The current collector includes a current-collecting section and a tab; the current-collecting section is coated with the active material layer, while the tab is not. Taking a lithium-ion battery as an example, the material of the current collector can be aluminum, and the active material layer includes a positive active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode includes a negative current collector and a negative active material layer, with the active material layer coated on the surface of the current collector. The current collector includes a current-collecting section and a tab; the current-collecting section is coated with the active material layer, while the tab is not. The negative electrode current collector can be made of copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon, etc. The separator can be made of PP (polypropylene) or PE (polyethylene), etc.

[0048] The battery cell also includes a casing, within which a sealed space is formed to house the electrode assembly and electrolyte. The casing protects the electrode assembly from the outside, reducing the risk of electrode assembly failure.

[0049] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, and charge / discharge rate. To improve the reversible capacity and low-temperature stability of individual battery cells, ternary lithium materials are used as the positive electrode active material. For example, the positive electrode active material comprises lithium nickel cobalt manganese oxide.

[0050] In the development of battery technology, battery safety also needs to be considered.

[0051] In a battery, multiple individual cells are used in groups. When a cell experiences thermal runaway due to an unexpected event (such as a collision, short circuit, or other conditions), the electrode assembly rapidly generates heat and produces high-temperature, high-pressure substances. Individual cells are typically equipped with a pressure relief mechanism, which breaks down when the internal pressure or temperature reaches a threshold, creating a channel for the release of the high-temperature, high-pressure substances. This pressure relief mechanism allows for pressure relief within the cell under controlled pressure or temperature conditions, thus preventing potentially more serious accidents.

[0052] However, the inventors noticed that the high-temperature, high-pressure substances released from the electrode assembly would act on the outer casing. If the casing melted, the high-temperature, high-pressure substances might escape through the openings formed by the melting of the casing. These substances would then act on other normal battery cells, potentially causing them to experience thermal runaway and resulting in a safety accident.

[0053] Through extensive research, the inventors discovered that the heat generated by the electrode assembly during thermal runaway is related to the nickel content in the lithium nickel cobalt manganese oxide of the positive electrode active material. The higher the nickel content, the higher the rate of gas generation and the more heat generated by the electrode assembly during thermal runaway, and the higher the risk of the outer shell melting.

[0054] In view of this, the inventors have proposed a battery cell whose casing is selected based on the nickel content in the positive electrode active material to reduce the risk of the casing melting in the event of thermal runaway and improve safety. Specifically, the battery cell includes a casing and a positive electrode sheet. The melting point of the casing is N. The positive electrode sheet is housed within the casing and includes a positive electrode active material, which comprises lithium nickel cobalt manganese oxide. The weight of nickel in the lithium nickel cobalt manganese oxide is G1, and the sum of the weights of nickel, cobalt, and manganese is G2. The value of G1 / G2 is denoted as M. M and N satisfy: 0.1≤M≤0.65, N≥(50M+500)℃; or, M and N satisfy: 0.65<M<1, N≥(950M+500)℃.

[0055] The battery cells described in the embodiments of this application are applicable to batteries and electrical devices that use batteries.

[0056] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical devices.

[0057] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0058] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0059] like Figure 1 As shown, a battery 2 is installed inside the vehicle 1. The battery 2 can be located at the bottom, front, or rear of the vehicle 1. The battery 2 can be used to power the vehicle 1; for example, the battery 2 can serve as the operating power source for the vehicle 1.

[0060] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

[0061] In some embodiments of this application, the battery 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0062] Figure 2 This is an exploded schematic diagram of a battery provided for some embodiments of this application.

[0063] like Figure 2 As shown, battery 2 includes a housing 5 and battery cells ( Figure 2 (Not shown), the battery cells are housed inside the casing 5.

[0064] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0065] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0066] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0067] In battery 2, there can be one or more individual battery cells. If there are multiple individual battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple individual battery cells are connected in both series and parallel configurations. Multiple individual battery cells can be directly connected in series, parallel, or in a mixed configuration and then housed within housing 5. Alternatively, multiple individual battery cells can first be connected in series, parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole and housed within housing 5.

[0068] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0069] like Figure 3 As shown, in some embodiments, there are multiple battery cells 7, which are first connected in series, parallel, or mixed to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or mixed to form a whole and housed in a casing.

[0070] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0071] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application; Figure 5A cross-sectional schematic diagram of a battery cell provided in some embodiments of this application; Figure 6 This is a schematic diagram of the structure of the positive electrode sheet of a battery cell provided in some embodiments of this application; Figure 7 This is a schematic diagram of the structure of the negative electrode sheet of a battery cell provided in some embodiments of this application.

[0072] like Figures 4 to 7 As shown, this application embodiment provides a battery cell 7, which includes a casing 20 and a positive electrode 11. The melting point of the casing 20 is N. The positive electrode 11 is housed within the casing 20 and includes a positive electrode active material, which comprises lithium nickel cobalt manganese oxide. The weight of nickel in the lithium nickel cobalt manganese oxide is G1, and the sum of the weights of nickel, cobalt, and manganese is G2. The value of G1 / G2 is denoted as M. M and N satisfy: 0.1≤M≤0.65, N≥(50M+500)℃; or, M and N satisfy: 0.65<M<1, N≥(950M+500)℃.

[0073] For example, the battery cell 7 includes an electrode assembly 10, which includes a positive electrode 11 and a negative electrode 12. The electrode assembly 10 generates electrical energy through oxidation and reduction reactions during the insertion / extraction of lithium ions in the positive electrode 11 and the negative electrode 12.

[0074] The outer shell 20 is a hollow structure, with an internal cavity for accommodating the electrode assembly 10 and the electrolyte. The shape of the outer shell 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cuboid structure, a cuboid outer shell can be used; if the electrode assembly 10 is a cylindrical structure, a cylindrical outer shell can be used.

[0075] Lithium nickel cobalt manganese oxides include lithium, nickel, cobalt, manganese, and oxygen. Lithium nickel cobalt manganese oxides may include only the aforementioned five elements, or they may include other elements.

[0076] For example, the molecular formula of lithium nickel cobalt manganese oxide is Li x Ni a Co b Mn c Z d O 2-y A y Z represents a transition metal site doped with a cation, and A represents an oxygen site doped with an anion. In Li x Ni a Co b Mn c Z d O 2-y A y Among them, 0.8≤x≤1.2, 0<a<1, 0<b<1, 0<c<1, 0≤d≤0.2, a+b+c+d=1, 0≤y≤0.2.

[0077] Z includes at least one of the following elements: Al, Si, Mg, Ti, V, Cr, Fe, Cu, Zn, Mo, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te, and W. A includes at least one of the following elements: F, N, P, and S.

[0078] For example, lithium nickel cobalt manganese oxide can be LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 LiNi 0.85 Co 0.15 Mn 0.05 O2.

[0079] M is used to characterize the nickel content. For example, in Li... x Ni a Co b Mn c P d O 2-y A y In the middle, M can be adjusted by adjusting the values ​​of a, b, and c.

[0080] The higher the value of M, the higher the rate of gas generation and the more heat generated by the electrode assembly 10 during thermal runaway, and the higher the melting point required for the casing 20; conversely, the lower the value of M, the less heat generated by the battery cell 7 during thermal runaway, and the lower the melting point required for the casing 20. The inventors of this application have discovered that for a battery cell 7 satisfying 0.1≤M≤0.65, the melting point of the casing 20 should be at least greater than or equal to (50M+500)℃ to reduce the risk of the casing 20 melting through during thermal runaway of the battery cell 7. For a battery cell 7 satisfying 0.65<M<1, the melting point of the casing 20 of the battery cell 7 should be at least greater than or equal to (950M+500)℃ to reduce the risk of the casing 20 melting through during thermal runaway of the battery cell 7.

[0081] In some embodiments, the elemental content of the positive electrode active material can be detected using inductively coupled plasma atomic emission spectroscopy (ICP).

[0082] In some embodiments, M and N satisfy: 0.1≤M≤0.65, N≥(200M+500)℃.

[0083] In some embodiments, M and N satisfy: 0.1≤M≤0.65, (50M+500)℃≤N≤(15000M+500)℃.

[0084] When selecting the outer shell 20, in addition to considering its melting point, other factors need to be considered, such as the strength and cost of the outer shell 20. The inventors discovered through research that limiting the melting point of the outer shell 20 to less than or equal to (15000M+500)℃ can reduce the excessive design of the melting point of the outer shell 20 and facilitate the selection of materials for the outer shell 20.

[0085] In some embodiments, for a battery cell 7 with M of 0.1-0.65, the melting point N of the casing 20 may be (50M+500)℃, (100M+500)℃, (200M+500)℃, (500M+500)℃, (1000M+500)℃, (2000M+500)℃, (5000M+500)℃, (10000M+500)℃, or (15000M+500)℃.

[0086] In some embodiments, M and N satisfy: 0.65 < M < 1, N ≥ (1000M + 500) °C.

[0087] In some embodiments, M and N satisfy: 0.65 < M < 1, N ≤ (3000M + 500)℃.

[0088] When selecting the outer shell 20, in addition to considering its melting point, other factors need to be considered, such as the strength and cost of the outer shell 20. The inventors discovered through research that limiting the melting point of the outer shell 20 to less than or equal to (3000M+500)℃ can reduce the excessive design of the melting point of the outer shell 20 and facilitate the selection of materials for the outer shell 20.

[0089] In some embodiments, M and N satisfy: N≤(1800M+500)℃.

[0090] In some embodiments, M and N satisfy: 0.1≤M≤0.65, 600℃≤N≤1800℃. Optionally, N is 600℃-800℃.

[0091] In some embodiments, M and N satisfy: 0.65 < M < 1, 800℃ ≤ N ≤ 1800℃. Optionally, N is 1400℃-1600℃.

[0092] In some embodiments, the battery cell 7 further includes a negative electrode sheet 12 housed within the casing 20. The negative electrode sheet 12 includes a negative electrode active material, which includes graphite and a silicon-containing material. The weight of the silicon-containing material is B1, and the weight of the graphite is B2. The value of B1 / (B1+B2) is denoted as P. P satisfies: 0 < P < 0.6.

[0093] Compared to graphite, silicon-containing materials have a higher specific capacity. In this embodiment, silicon-containing materials are used to replace part of the graphite, which effectively improves the energy density of the battery cell 7. However, silicon-containing materials expand significantly during charging. If the silicon content is too high, it will lead to excessive expansion force in the battery cell 7 during charging, affecting the safety and cycle life of the battery cell 7. The inventors have limited the value of P to be greater than 0 and less than 0.6 to balance the energy density and expansion force of the battery cell 7.

[0094] In some embodiments, the silicon-containing material includes at least one of silicon oxide, pure silicon, and silicon carbide.

[0095] In some embodiments, the tensile strength of the outer shell 20 is Q, where Q and M satisfy: 0.1≤M≤0.65, Q≥(50M+50)MPa.

[0096] Tensile strength is the critical value at which a material transitions from uniform plastic deformation to localized concentrated plastic deformation, and it is also the maximum load-bearing capacity of a material under static tensile conditions. For ductile materials, tensile strength characterizes the material's resistance to maximum uniform plastic deformation. Before being subjected to the maximum tensile stress, the material deforms uniformly; however, beyond this point, necking begins to occur, resulting in concentrated deformation. For brittle materials without uniform plastic deformation, or brittle materials with very small uniform plastic deformation, tensile strength reflects the material's fracture resistance.

[0097] The tensile strength of the outer shell 20 can be tested according to the following steps: cut a sample from the outer shell 20 and measure the cross-sectional area S of the sample. o The specimen is mounted on a tensile testing machine, which stretches the specimen and records the tensile force value in real time. After the specimen breaks, the maximum load F that the specimen could withstand before breaking is obtained. b The tensile strength of the outer shell 20 is F. b / S o .

[0098] The higher the value of M, the higher the rate and the greater the amount of gas generated by the electrode assembly 10 during thermal runaway. The gas increases the internal pressure of the outer casing 20, causing the outer casing 20 to stretch under the action of internal pressure, which in turn makes the outer casing 20 more prone to cracking under the action of high temperature and high pressure substances.

[0099] The inventors of this application discovered through research that for a battery cell 7 that satisfies 0.1≤M≤0.65, the tensile strength of the casing 20 should be at least greater than or equal to (50M+50)MPa, in order to reduce the amount of stretching of the casing 20 during thermal runaway of the battery cell 7, reduce the risk of cracking of the casing 20, and improve safety.

[0100] In some embodiments, Q and M satisfy: 0.1 ≤ M ≤ 0.65, Q ≤ (1100M + 50) MPa. Optionally, Q is (50M + 50) MPa, (100M + 50) MPa, (200M + 50) MPa, (500M + 50) MPa, (800M + 50) MPa, (1000M + 50) MPa, or (1100M + 50) MPa.

[0101] When selecting the outer shell 20, factors such as the melting point, tensile strength, and cost of the outer shell 20 need to be considered. The inventors found through research that limiting the tensile strength of the outer shell 20 to less than or equal to (1100M+50)MPa can reduce the excessive design of the tensile strength of the outer shell 20 and facilitate the selection of materials for the outer shell 20.

[0102] In some embodiments, the tensile strength of the outer shell 20 is Q, where Q and M satisfy: 0.65 < M < 1, Q ≥ (300M + 50) MPa.

[0103] The inventors of this application have discovered through research that for a battery cell 7 that satisfies 0.65 < M < 1, the tensile strength of the casing 20 should be at least greater than or equal to (300M + 50) MPa, in order to reduce the amount of stretching of the casing 20 during thermal runaway of the battery cell 7, reduce the risk of cracking of the casing 20, and improve safety.

[0104] In some embodiments, the tensile strength of the outer shell 20 is Q, where Q and M satisfy: 0.65 < M < 1, Q ≤ (950M + 50) MPa. Optionally, Q is (300M + 50) MPa, (400M + 50) MPa, (500M + 50) MPa, (700M + 50) MPa, (900M + 50) MPa, or (950M + 50) MPa.

[0105] When selecting the outer shell 20, factors such as the melting point, tensile strength, and cost of the outer shell 20 need to be considered comprehensively. The inventors found through research that limiting the tensile strength of the outer shell 20 to less than or equal to (950M+50)MPa can reduce the excessive design of the tensile strength of the outer shell 20 and facilitate the selection of materials for the outer shell 20.

[0106] In some embodiments, the housing 20 may be made of metal.

[0107] In some embodiments, the outer casing 20 may be made of copper, iron, aluminum, nickel, stainless steel, aluminum alloy, copper alloy, magnesium-aluminum alloy, zinc alloy, nickel alloy or other materials.

[0108] In some embodiments, the housing 20 includes a housing 21 and an end cap 22, the housing 21 having an opening and the end cap 22 for closing the opening.

[0109] End cap 22 is sealed to housing 21 to form a sealed space for accommodating electrode assembly 10 and electrolyte. In some examples, housing 21 has an opening at one end, and end cap 22 is configured as one that covers the opening of housing 21. In other examples, housing 21 has openings at both opposite ends, and end cap 22 is configured as two, with each end cap 22 covering one of the two openings of housing 21.

[0110] Regardless of the specific type, the shape of the end cap 22 can be adapted to the shape of the housing 21 to fit the housing 21. Optionally, the end cap 22 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 22 is not easily deformed when subjected to compression and impact, so that the battery cell 7 can have higher structural strength and the safety performance can also be improved.

[0111] The housing 21 can have various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 21 can be determined according to the specific shape and size of the electrode assembly 10. The material of the housing 21 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and this application embodiment does not impose any special limitations on this.

[0112] The housing 21 and the end cap 22 may be made of the same material or different materials. For example, if the housing 21 and the end cap 22 are made of different materials, then the melting point of the housing 21 and the melting point of the end cap 22 both satisfy the aforementioned relationship.

[0113] In some embodiments, the end cap 22 may be provided with functional components such as electrode terminals 30. The electrode terminals 30 can be used to electrically connect with the electrode assembly 10 for outputting or inputting electrical energy from the battery cell 7.

[0114] In some embodiments, the electrode assembly 10 includes a positive electrode 11, a negative electrode 12, and a separator 13 separating the positive electrode 11 and the negative electrode 12. The electrode assembly 10 may be a wound structure, a stacked structure, or other structures.

[0115] In some embodiments, the positive electrode 11 includes a positive current collector 111 and a positive active material layer 112 coated on the surface of the positive current collector 111, wherein the positive active material layer 112 includes a positive active material. Optionally, the positive active material layer 112 further includes a conductive agent and a binder.

[0116] In some embodiments, the negative electrode 12 includes a negative electrode current collector 121 and a negative electrode active material layer 122 coated on the surface of the negative electrode current collector 121. The negative electrode active material layer 122 includes a negative electrode active material. The negative electrode active material layer 122 also includes a conductive agent and a binder.

[0117] In some embodiments, the wall thickness t of the housing 21 is 0.05mm-2mm.

[0118] The thinner the casing 21, the easier it is for the casing 21 to melt through in the event of thermal runaway of the battery cell 7; conversely, the thicker the casing 21, the heavier the casing 21, and the lower the energy density of the battery cell 7. Through calculation and experimentation, the inventors set the wall thickness of the casing 21 to 0.05mm-2mm to balance the safety and energy density of the battery cell 7.

[0119] Optionally, the wall thickness of the housing 21 is 0.05mm, 0.1mm, 0.2mm, 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm or 2mm.

[0120] In some embodiments, the thickness of the end cap 22 is greater than the wall thickness of the housing 21.

[0121] In some embodiments, the housing 21 and the end cap 22 are made of the same material. A housing 21 and end cap 22 made of the same material are easier to join together by welding.

[0122] In some embodiments, the housing 21 includes two first side plates 211 disposed along a first direction D1 and two second side plates 212 disposed along a second direction D2, the second side plates 212 connecting the two first side plates 211, the first direction D1 being perpendicular to the second direction D2. The ratio θ of the dimension of the housing 21 along the second direction D2 to the dimension of the housing 21 along the first direction D1 is 1-50.

[0123] The inventors limited the value of θ to 1-50 to facilitate the arrangement of multiple battery cells 7.

[0124] In some embodiments, the area of ​​the first side plate 211 is larger than the area of ​​the second side plate 212.

[0125] In some embodiments, the size of the housing 21 along the third direction D3 is 10mm-200mm, and the third direction D3 is perpendicular to the first direction D1 and the second direction D2.

[0126] In some embodiments, the outer casing 20 is made of steel or nickel. Materials such as steel and nickel have melting points exceeding 1400°C, which effectively reduces the risk of the outer casing 20 melting through.

[0127] Alternatively, the housing 21 may be made of SPCC (generally cold-rolled carbon steel sheet and strip), 304 stainless steel or pure nickel.

[0128] According to some embodiments of this application, this application also provides a battery comprising multiple battery cells of any of the above embodiments.

[0129] According to some embodiments of this application, this application also provides an electrical device, including a battery cell from any of the above embodiments, wherein the battery cell is used to provide electrical energy to the electrical device. The electrical device can be any of the aforementioned devices or systems that utilize battery cells.

[0130] According to some embodiments of this application, refer to Figures 4 to 7 This application provides a battery cell 7, which includes a casing 20 and an electrode assembly 10 housed within the casing 20. The electrode assembly 10 includes a positive electrode 11 and a negative electrode 12. The melting point of the casing 20 is N, and the tensile strength of the casing 20 is Q. The positive electrode 11 includes a positive electrode active material, which comprises lithium nickel cobalt manganese oxide. The weight of nickel in the lithium nickel cobalt manganese oxide is G1, and the sum of the weights of nickel, cobalt, and manganese is G2. The value of G1 / G2 is denoted as M. The negative electrode 12 includes a negative electrode active material, which comprises graphite and a silicon-containing material. The weight of the silicon-containing material is B1, and the weight of the graphite is B2. The value of B1 / (B1+B2) is denoted as P. P satisfies: 0 < P < 0.6.

[0131] In some examples, M, N, and Q satisfy: 0.1 ≤ M ≤ 0.65, (50M+500)℃ ≤ N ≤ (15000M+500)℃, and (50M+50)MPa ≤ Q ≤ (1100M+50). In other examples, M, N, and Q satisfy: 0.65 < M < 1, (950M+500)℃ ≤ N ≤ (3000M+500)℃, and (300M+50)MPa ≤ Q ≤ (950M+50)MPa.

[0132] The present application is further illustrated below with reference to the embodiments.

[0133] To make the inventive purpose, technical solution, and beneficial technical effects of this application clearer, the following describes this application in further detail with reference to embodiments. However, it should be understood that the embodiments of this application are merely for explaining this application and are not intended to limit this application, and the embodiments of this application are not limited to the embodiments given in the specification. Unless otherwise specified, specific experimental or operating conditions in the embodiments are prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0134] Example 1 can be prepared according to the following steps:

[0135] (i) The positive electrode active material LiNi a Co b Mn c O2, conductive agent acetylene black, and binder PVDF are mixed in a mass ratio of 96:2:2. NMP solvent is added, and the mixture is stirred in a vacuum mixer until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing, slitting, and cutting, the positive electrode sheet is obtained.

[0136] (ii) The negative electrode active material graphite, conductive agent acetylene black, thickener CMC and binder SBR are mixed in a mass ratio of 96.4:1:1.2:1.4, and deionized water is added as solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on copper foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing, slitting and cutting, the negative electrode sheet is obtained.

[0137] (iii) Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0138] (iv) Use a 7μm thick polyethylene film as a separator.

[0139] (v) The positive electrode, the separator and the negative electrode are stacked together and wound into multiple turns, and then flattened into a flat shape to prepare the electrode assembly.

[0140] (vi) The electrode assembly and heating element are installed into a square housing, and the housing and end caps are welded together. Then, through processes such as liquid injection, settling, formation, and shaping, a single battery cell is obtained. The heating element is attached to the electrode assembly, and the wires of the heating element extend from the end cap.

[0141] In step (i), a + b + c = 1. When preparing the positive electrode active material, the weight of nickel can be changed by adjusting the molar ratio of nickel, cobalt, and manganese atoms. The weight of nickel is G1, the sum of the weights of nickel, cobalt, and manganese is G2, the weight of cobalt atoms is G3, and the weight of manganese is G4. In Example 1, M = G1 / G2 = 0.5, G3 / G2 = 0.2, and G4 / G2 = 0.3.

[0142] In step (vi), both the shell and the end cap are made of aluminum alloy, and the melting point N of the shell is 660°C.

[0143] Example 2:

[0144] The preparation method of the battery cell in Example 2 is the same as that in Example 1, except that: M = G1 / G2 = 0.6, G3 / G2 = 0.2, G4 / G2 = 0.2.

[0145] Example 3:

[0146] The preparation method of the battery cell in Example 3 is the same as that in Example 1, except that: M = G1 / G2 = 0.65, G3 / G2 = 0.15, and G4 / G2 = 0.2.

[0147] Example 4:

[0148] The preparation method of the battery cell in Example 4 is the same as that in Example 1, except that: M = G1 / G2 = 0.1, G3 / G2 = 0.5, G4 / G2 = 0.4.

[0149] Example 5:

[0150] The preparation method of the battery cell in Example 5 is the same as that in Example 1, except that: M = G1 / G2 = 0.3, G3 / G2 = 0.4, G4 / G2 = 0.3.

[0151] Example 6:

[0152] The preparation method of the battery cell in Example 6 is the same as that in Example 1, except that the casing and end cap are both made of copper-zinc alloy and the melting point N of the casing is 550°C.

[0153] Example 7:

[0154] The preparation method of the battery cell in Example 7 is the same as that in Example 1, except that: M = G1 / G2 = 0.7, G3 / G2 = 0.15, G4 / G2 = 0.15; the casing and end cap are both made of steel, and the melting point N of the casing is 1500℃.

[0155] Example 8:

[0156] The preparation method of the battery cell in Example 8 is the same as that in Example 7, except that: M = G1 / G2 = 0.8, G3 / G2 = 0.1, G4 / G2 = 0.1.

[0157] Example 9:

[0158] The preparation method of the battery cell in Example 9 is the same as that in Example 7, except that: M = G1 / G2 = 0.9, G3 / G2 = 0.05, G4 / G2 = 0.05.

[0159] Example 10:

[0160] The preparation method of the battery cell in Example 10 is the same as that in Example 7, except that: M = G1 / G2 = 0.96, G3 / G2 = 0.02, G4 / G2 = 0.02.

[0161] Example 11:

[0162] The preparation method of the battery cell in Example 11 is the same as that in Example 8, except that the casing and end cap are both made of copper-nickel alloy and the melting point N of the casing is 1300°C.

[0163] Example 12:

[0164] The preparation method of the battery cell in Example 12 is the same as that in Example 7, except that the casing and end cap are both made of copper-nickel alloy and the melting point N of the casing is 1200°C.

[0165] Comparative Example 1:

[0166] The preparation method of the battery cell in Comparative Example 1 is the same as that in Example 1, except that: M = G1 / G2 = 0.6, G3 / G2 = 0.2, G4 / G2 = 0.2; the casing and end cap are both made of zinc alloy, and the melting point N of the casing is 420°C.

[0167] Comparative Example 2:

[0168] The preparation method of the battery cell in Comparative Example 2 is the same as that in Example 1, except that: M = G1 / G2 = 0.1, G3 / G2 = 0.5, G4 / G2 = 0.4; the casing and end cap are both made of zinc alloy, and the melting point N of the casing is 420°C.

[0169] Comparative Example 3:

[0170] The preparation method of the battery cell in Comparative Example 3 is the same as that in Example 1, except that: M = G1 / G2 = 0.7, G3 / G2 = 0.15, G4 / G2 = 0.15; the casing and end cap are both made of zinc alloy, and the melting point N of the casing is 420°C.

[0171] Comparative Example 4:

[0172] The preparation method of the battery cell in Comparative Example 4 is the same as that in Example 1, except that: M = G1 / G2 = 0.66, G3 / G2 = 0.22, and G4 / G2 = 0.22.

[0173] Comparative Example 5:

[0174] The preparation method of the battery cell of Comparative Example 5 is the same as that of Example 1, except that: M = G1 / G2 = 0.7, G3 / G2 = 0.15, G4 / G2 = 0.15; the shell and end cap are both made of copper alloy, and the melting point N of the shell is 1083℃.

[0175] Comparative Example 6:

[0176] The preparation method of the battery cell of Comparative Example 6 is the same as that of Example 1, except that: M = G1 / G2 = 0.9, G3 / G2 = 0.05, G4 / G2 = 0.05; the shell and end cap are both made of copper-nickel alloy, and the melting point N of the shell is 1300℃.

[0177] In Examples 1-12 and Comparative Examples 1-6, 100 battery cells were prepared, and thermal runaway tests were performed on each battery cell.

[0178] Specifically, the battery cells are placed in a sealed enclosure, and an external power source is used to energize the heating elements inside the battery cells. These heating elements heat the electrode assembly, causing thermal runaway. After thermal runaway, the battery cell casing is observed for melting, cracking, or other damage. If melting or cracking occurs, the casing is considered to have failed. The number of failed casings divided by the total number of battery cells gives the casing failure rate.

[0179] The evaluation results of Examples 1-12 and Comparative Examples 1-6 are shown in Table 1.

[0180] Table 1

[0181]

[0182] Referring to Examples 1-12 and Comparative Examples 1-6, the embodiments of this application select the outer casing based on the nickel content in the positive electrode active material to reduce the risk of the outer casing melting when the battery cell experiences thermal runaway, thereby improving safety.

[0183] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A single battery cell, comprising: The outer shell, the melting point of which is N; A positive electrode sheet is housed within the outer casing and includes a positive electrode active material. The positive electrode active material comprises lithium nickel cobalt manganese oxide. The weight of nickel in the lithium nickel cobalt manganese oxide is G1, and the sum of the weights of nickel, cobalt, and manganese is G2. The value of G1 / G2 is denoted as M. M and N satisfy: 0.1≤M≤0.65, N≥(50M+500)℃; Alternatively, M and N satisfy: 0.65 < M < 1, N ≥ (950M + 500)℃.

2. The battery cell according to claim 1, wherein, M and N satisfy: 0.1≤M≤0.65, N≥(200M+500)℃.

3. The battery cell according to claim 1 or 2, wherein, M and N satisfy: 0.1≤M≤0.65, (50M+500)℃≤N≤(15000M+500)℃.

4. The battery cell according to claim 1, wherein, M and N satisfy: 0.65 < M < 1, N ≥ (1000M + 500)℃.

5. The battery cell according to claim 1 or 4, wherein, M and N satisfy: 0.65 < M < 1, N ≤ (3000M + 500)℃.

6. The battery cell according to any one of claims 1, 2, and 4, wherein, M and N satisfy: N≤(1800M+500)℃.

7. The battery cell according to any one of claims 1, 2 and 4, further comprising a negative electrode sheet housed within the casing; The negative electrode sheet includes a negative electrode active material, which includes graphite and a silicon-containing material. The weight of the silicon-containing material is B1, and the weight of the graphite is B2. The value of B1 / (B1+B2) is denoted as P. P satisfies: 0 < P < 0.

6.

8. The battery cell according to claim 7, wherein, The tensile strength of the outer shell is Q, and Q and M satisfy: 0.1≤M≤0.65, Q≥(50M+50)MPa.

9. The battery cell according to claim 8, wherein, Q and M satisfy: Q≤(1100M+50)MPa.

10. The battery cell according to claim 7, wherein, The tensile strength of the outer shell is Q, and Q and M satisfy: 0.65 < M < 1, Q ≥ (300M + 50) MPa.

11. The battery cell according to claim 10, wherein, Q and M satisfy: Q≤(950M+50)MPa.

12. The battery cell according to any one of claims 1, 2, and 4, wherein, The housing includes a shell and an end cap, the shell having an opening and the end cap for closing the opening.

13. The battery cell according to claim 12, wherein, The wall thickness of the shell is 0.05mm-2mm.

14. The battery cell according to claim 12, wherein, The housing and the end cap are made of the same material.

15. The battery cell according to claim 12, wherein, The housing includes two first side plates arranged along a first direction and two second side plates arranged along a second direction, the second side plates connecting the two first side plates, and the first direction being perpendicular to the second direction; The ratio of the dimension of the housing along the second direction to the dimension of the housing along the first direction is 1-50.

16. The battery cell according to any one of claims 1, 2, and 4, wherein, The outer casing is made of materials including steel or nickel.

17. A battery comprising a plurality of battery cells according to any one of claims 1-16.

18. An electrical device comprising a battery cell according to any one of claims 1-16, the battery cell being used to provide electrical energy.

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