Lithium ion battery, power battery module, battery pack, electric automobile and energy storage device

Abstract

The invention provides a lithium ion battery, a power battery module, a battery pack, an electric vehicle and an energy storage device.The lithium ion battery comprises a shell and a pole shank packaged in the shell, and the pole shank comprises a positive plate, a negative plate and a separator located between the positive plate and the negative plate; the positive plate comprises a positive current collector and a positive material layer loaded on the positive current collector, one of the positive current collector, the positive material layer, the negative plate and the separator with the lowest melting point is defined as an effective component, and the effective component meets the following condition: # imgabs0 #. By reasonably optimizing and designing parameters such as sizes in different directions and the like of the pole core part, the safety of the battery is greatly improved, the probability of thermal runaway or thermal diffusion of the battery is effectively reduced, and damage to adjacent batteries or the outside caused by heat generated by the battery is avoided.

Description

[0001] This application is a divisional application of the Chinese patent application with the application number 202010478294.4 and the invention title of "Lithium-ion battery, power battery module, battery pack, electric vehicle and energy storage device", which was filed with the Chinese Patent Office on May 29, 2020. Technical Field

[0002] This application relates to the technical field of lithium-ion batteries, and specifically, to lithium-ion batteries, power battery modules, battery packs, electric vehicles and energy storage devices. Background Art

[0003] The unique characteristics of lithium-ion batteries have been applied in more and more fields. Especially in the aspect of power batteries, they have developed rapidly. When lithium batteries are used as the main energy supply source for electric vehicles, especially the large-scale use of ternary batteries in recent years, accidents such as fires and explosions caused by thermal runaway of lithium-ion power batteries (the phenomenon of overheating, catching fire and explosion where the self-temperature rise rate of the battery changes sharply due to the exothermic chain reaction of the battery) often occur. In a battery pack, once one battery undergoes thermal runaway, it often triggers the thermal runaway of adjacent batteries in the battery pack or system, that is, thermal diffusion, resulting in the out-of-control of the entire battery pack and causing serious consequences such as fires and explosions. At present, the safety of using lithium-ion batteries still faces challenges.

[0004] Application Content

[0005] This application aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of this application is to provide a lithium-ion battery that can effectively improve the thermal runaway problem and enhance the safety of use.

[0006] In one aspect of this application, this application provides a lithium-ion battery. According to the embodiments of this application, the lithium-ion battery includes a housing and an electrode core encapsulated in the housing. The electrode core includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer loaded on the positive electrode current collector. It is characterized in that the component with the lowest melting point among the positive electrode current collector, the positive electrode material layer, the negative electrode sheet, and the separator is defined as the effective component, and the effective component satisfies the following conditions:

[0007]

[0008] wherein, L is the dimension of the effective component in the first direction, W is the dimension of the effective component in the second direction, d 2 is the thickness of the effective component, ρ is the density of the effective component, C pFor the hot melt of the effective component, the first direction is parallel to the direction in which the current is led out in the effective component, and the second direction intersects the first direction. In this lithium-ion battery, by reasonably optimizing and designing parameters such as the dimensions of the electrode core component in different directions, the battery safety is greatly improved. For a lithium-ion battery that meets the above conditions, the probability of battery thermal runaway or thermal diffusion is effectively reduced, and damage to adjacent batteries or the outside caused by battery heat generation is avoided.

[0009] In another aspect of the present application, the present application provides a lithium-ion battery. The lithium-ion battery includes a housing and an electrode core encapsulated in the housing. The electrode core includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer loaded on the positive electrode current collector. The positive electrode current collector satisfies the following conditions:

[0010]

[0011] wherein, L is the dimension of the positive electrode current collector in the first direction, W is the dimension of the positive electrode current collector in the second direction, d 2 is the thickness of the positive electrode current collector, ρ is the density of the positive electrode current collector, C p is the specific heat capacity of the positive electrode current collector. The first direction is parallel to the direction in which the current is led out in the positive electrode current collector, and the second direction intersects the first direction.

[0012] In another aspect of the present application, the present application provides a power battery module. According to an embodiment of the present application, the power battery module includes at least one of the above-mentioned lithium-ion batteries. The possibility of thermal runaway and thermal diffusion of the power battery module is significantly reduced, and the use safety is significantly improved.

[0013] In still another aspect of the present application, the present application provides a battery pack. According to an embodiment of the present application, the battery pack includes at least one of the above-mentioned lithium-ion batteries or the above-mentioned battery module. The battery pack has high use safety and a long service life.

[0014] In yet another aspect of the present application, the present application provides an electric vehicle. According to an embodiment of the present application, the electric vehicle includes the above-mentioned power battery module or the above-mentioned battery pack. The electric vehicle has excellent safety and a long service life.

[0015] In another aspect of the present application, the present application provides an energy storage device. According to an embodiment of the present application, the energy storage device includes the above-mentioned power battery module or the above-mentioned battery pack. The probability of thermal runaway and thermal diffusion of the energy storage device is significantly reduced, and it has excellent safety and a long service life. Description of the Drawings

[0016] Figure 1 is a schematic structural view of a stacked electrode core according to an embodiment of the present application.

[0017] Figure 2 is Figure 1 a schematic cross-sectional structural view of a positive electrode sheet along line A-A in

[0018] Figure 3 is a schematic structural view of a flattened state of a laminate constituting a wound electrode core according to an embodiment of the present application.

[0019] Figure 4 is a schematic structural view of a wound electrode core according to an embodiment of the present application.

[0020] Figure 5 is a schematic structural view of a wound electrode core according to an embodiment of the present application.

[0021] Figure 6 is Figure 4 and Figure 5 a schematic plan view of a winding section in

[0022] Figure 7 is Figure 6 a schematic cross-sectional structural view along line B-B in

[0023] Figure 8 a schematic plan view of a winding section according to another embodiment of the present application. Detailed Description of the Embodiments

[0024] The embodiments of the present application will be described in detail below. The following described embodiments are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those technical or conditions not specified in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0025] In one aspect of the present application, the present application provides a lithium-ion battery. According to an embodiment of the present application, the lithium-ion battery includes a housing and an electrode core encapsulated in the housing. The electrode core includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer loaded on the positive electrode current collector. Define the component with the lowest melting point among the positive electrode current collector, the positive electrode material layer, the negative electrode sheet, and the separator as the effective component, and the effective component satisfies the following conditions:

[0026]

[0027] Wherein, L is the dimension of the effective component in the first direction, W is the dimension of the effective component in the second direction, d 2 is the thickness of the effective component, ρ is the density of the effective component, C p is the heat capacity of the effective component. The first direction is parallel to the direction in which the current is led out in the effective component, and the second direction intersects with the first direction. In this lithium-ion battery, by reasonably optimizing and designing parameters such as the dimensions of the electrode core component in different directions, the battery safety is greatly improved. For a lithium-ion battery that meets the above conditions, the probability of battery thermal runaway or thermal diffusion is effectively reduced. At the same time, there are no new components added, the battery system design remains unchanged, and there is no additional cost increase. In addition, in the lithium-ion battery of the present application, the higher the value of A, the relatively lower the battery safety. After exceeding 850, the internal structure design of the battery makes the generated heat unable to be discharged in time, resulting in a decrease in battery safety; while the lower the value of A, the serious waste of battery space and the unfavorable shape of the battery for arrangement inside the electric vehicle.

[0028] In some embodiments, the effective component satisfies the following conditions:

[0029]

[0030] Thereby, the safety of the lithium-ion battery is further improved, and the probability of thermal runaway and thermal diffusion is further reduced.

[0031] Specifically, the inventors of the present application based on the following two equations and models for reasonable design and optimization to obtain the lithium-ion battery of the present application, specifically as follows:

[0032] According to the general heat balance equation:

[0033]

[0034] The boundary conditions are:

[0035]

[0036] Where ρ represents the density of a predetermined component in the system, T represents the temperature when the system reaches thermal equilibrium, t represents time, Cp represents the specific heat of the predetermined component, k represents the thermal conductivity, Q represents the generated heat, h represents the heat coefficient between the shell and the air, E represents the electromotive force, U represents the terminal voltage, I represents the charge and discharge current, T surface represents the surface temperature of the system, T room represents the room temperature.

[0037] For the one-dimensional heat diffusion model, there is:

[0038]

[0039] Wherein, Q is a quantity of heat given at the point x = 0 at the instant t = 0, △T is the increment of the temperature at the distance x = R from the zero point relative to the room temperature, ρ is the density of the heat conductor, c is the heat capacity of the heat conductor, δ is the thickness of the heat conductor, α is the heat conduction coefficient α = k / (ρc), k is the thermal conductivity of the heat conductor, m 2 = 2h / (kδ).

[0040] Based on the above equations and models, combined with the actual research experience of the inventors, and following the following principles, the inventors proposed this application: Thermal runaway is mostly caused by internal short circuits in the battery. Once a short circuit occurs, the temperature at the short circuit point can rise rapidly, triggering thermal runaway of the battery, which is extremely likely to cause fire or explosion. In the lithium-ion battery of this application, by controlling parameters such as the size and thermodynamics of the effective components in the battery, when a short circuit occurs in the battery, the short circuit point can be quickly melted, thus cutting off the short circuit point, preventing further heat generation, and at the same time ensuring that the material does not reach the runaway point, thereby greatly ensuring the safety of the battery and avoiding the occurrence of thermal runaway, and greatly improving the safety of the battery.

[0041] Specifically, the lithium-ion battery of this application can be a liquid battery, a solid battery or a polymer battery. For liquid batteries and polymer batteries, it can include a positive electrode sheet, a negative electrode sheet and a separator (i.e., a partition) located between the positive electrode sheet and the negative electrode sheet. Of course, the electrode core also includes an electrolyte. For solid batteries, it includes a positive electrode sheet, a negative electrode sheet and a solid electrolyte layer (i.e., a partition) located between the positive electrode sheet and the negative electrode sheet.

[0042] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode material layer loaded on the negative electrode current collector; in this embodiment, the component with the lowest melting point among the positive electrode current collector, the positive electrode material layer, the negative electrode current collector, the negative electrode material layer and the separator is defined as the effective component.

[0043] In some other embodiments, the negative electrode sheet can be a lithium foil or a lithium strip. In this embodiment, the component with the lowest melting point among the positive electrode current collector, the positive electrode material layer, the lithium foil (or lithium strip) and the separator is defined as the effective component.

[0044] In still some other embodiments, the negative electrode sheet may include a porous current collector and a negative electrode active material deposited in the porous structure. In this embodiment, the component with the lowest melting point among the positive electrode current collector, the positive electrode material layer, the porous current collector and the separator is defined as the effective component.

[0045] In addition, a positive electrode tab and a negative electrode tab for leading out current are respectively provided on the positive electrode sheet and the negative electrode sheet. Specifically, the positive electrode tab and the negative electrode tab are respectively led out from one side of the positive electrode sheet and the negative electrode sheet, and the positive electrode tab and the negative electrode tab can be arranged on the same side (refer to Figure 8 ), or can be arranged opposite to each other (refer to Figure 1 and Figure 7) The direction in which the tab is led out is the direction in which the current is led out.

[0046] In the electrode core, multiple positive electrode plates 10 and negative electrode plates 20 can be alternately stacked in sequence to form a stacked electrode core (for the structural schematic diagram, refer to Figure 1 ), a separator is provided between adjacent positive electrode plates and negative electrode plates, or the positive electrode plate, the separator, and the negative electrode plate can be stacked and then wound to form a wound electrode core (for the structural schematic diagram, refer to Figure 2 ). The specific method can refer to the conventional technology and will not be described in detail here.

[0047] It should be noted that for the stacked electrode core, specifically refer to Figure 1 , which includes multiple positive electrode plates 10 and negative electrode plates 20 alternately stacked in sequence, and a separator (not shown in the figure) is provided between adjacent positive electrode plates 10 and negative electrode plates 20. At this time, L refers to the dimension of an effective component in the first direction, W refers to the dimension of an effective component in the second direction, and d 2 is the thickness of an effective component (the dimension along the stacking direction).

[0048] For the wound electrode core, specifically refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 . After the positive electrode plate 10, the negative electrode plate 20, and the separator 40 are stacked, they are wound. Specifically, the positive electrode plate 10, the separator 40, and the negative electrode plate 20 stacked in sequence are defined as the stack 30. The stack 30 is divided into multiple wound segments 31 connected in sequence (refer to Figure 3 ). When in the wound state, multiple wound segments 31 are stacked in sequence (refer to Figure 4 ). At this time, L is the dimension of the effective component in one wound segment in the first direction, W is the average value of the dimensions of the effective components in multiple wound segments in the second direction, and d 2 is the thickness of the effective component in one wound segment.

[0049] In addition, it should also be noted that the second direction described in this article intersects with the first direction. Specifically, it means that the included angle between the first direction and the second direction can be greater than 0 degrees and less than or equal to 90 degrees. In some specific embodiments, the included angle between the first direction and the second direction can specifically be 90 degrees, that is, the first direction and the second direction are perpendicular.

[0050] Specifically, according to the commonly used materials of each component in a lithium-ion battery, generally, the melting point of the positive current collector is relatively low. When the positive current collector melts during thermal runaway, the electrode material does not go out of control, which can greatly ensure the safety of the battery. Among the various short-circuit forms inside the battery that lead to thermal runaway, such as short-circuit between the positive and negative electrode materials, short-circuit between the positive current collector and the negative electrode sheet, short-circuit between the negative current collector and the positive electrode, etc., after the positive current collector comes into contact with the negative electrode material and causes a short circuit, the generated heat is the largest. Experiments have found that once a short circuit occurs, the temperature at the short-circuit point can quickly rise to 200 °C, thereby triggering the out-of-control of the material and extremely likely causing fire or explosion. In the lithium-ion battery of the present application, with the basic purpose of ensuring that the material does not reach the out-of-control point when the short-circuit point melts, the positive current collector is selected as an effective component, which can effectively avoid thermal runaway and thermal diffusion, and thus greatly improve the safety of battery use.

[0051] The following further details the solution of the present application with the positive current collector as an effective component.

[0052] According to an embodiment of the present application, referring to Figure 1 and Figure 2 , a positive electrode tab 11 is also led out from one side of the positive electrode sheet 10. Specifically, the direction in which the positive electrode tab is led out is the direction in which the current in the positive current collector is led out. Therefore, at this time, the first direction is parallel to the direction in which the positive electrode tab is led out.

[0053] Specifically, the positive electrode tab can be welded to the positive current collector, or can be formed by cutting the positive current collector, that is, the positive electrode tab and the positive current collector are integrally formed. It should be noted that regardless of the way the positive electrode tab is led out from the positive current collector, the dimension of the positive current collector in the first direction does not include the dimension of the positive electrode tab in the first direction. It can be understood that the situation of the negative electrode tab can be the same as that of the positive electrode tab, and will not be elaborated here one by one. Further, the second direction can be selected according to the actual situation. In some specific embodiments, the second direction is perpendicular to the first direction. Thus, the matching degree with the above conditions is higher, the probability of thermal runaway and thermal diffusion is lower, and the safety of the battery is better.

[0054] In some embodiments, referring to Figure 1 and Figure 2 , the electrode core in the lithium-ion battery can be a laminated electrode core. The laminated electrode core includes a plurality of alternately laminated positive electrode sheets 10 and negative electrode sheets 20. L is the dimension of the positive current collector 12 in the positive electrode sheet 10 in the first direction, W is the dimension of the positive current collector 12 in the positive electrode sheet 10 in the second direction, and d 2 is the thickness of the positive current collector 12 in the positive electrode sheet 10. Figure 1 and Figure 2 In the electrode core shown, L, W, and d 2 are as shown in the figure.

[0055] In some other embodiments, the electrode core in the lithium-ion battery can be a wound electrode core. Referring to Figures 3 to 7 , the wound electrode core is formed by winding a laminate 30 divided into a plurality of sequentially connected winding segments 31. In the wound electrode core, the plurality of winding segments 31 are stacked, and each winding segment 31 includes a positive electrode sheet 10, a separator 40, and a negative electrode sheet 20 that are sequentially stacked. L is the dimension of the positive electrode current collector 12 in one winding segment 31 in the first direction, W is the average value of the dimensions of the positive electrode current collector 12 in the plurality of winding segments 31 in the second direction, and d 2 is the thickness of the positive electrode current collector 12 in one winding segment 31. Specifically, Figures 3 to 7 in the shown wound electrode core, W = (W1 + W2 + W3 + W4 + W5) / 5, and L is as shown in the figure.

[0056] In some embodiments, the material of the positive electrode current collector includes aluminum, such as aluminum foil, and the negative electrode current collector is copper foil. When reasonable designs are made for various parameters of the battery (parameters such as the number of effective component layers, dimensions in different directions, thickness, heat capacity, etc.), combined with the low melting point of aluminum, it can effectively ensure that when the material melts at the short-circuit point, the material is not out of control, thereby avoiding thermal runaway and thermal diffusion, and greatly ensuring the safety of the lithium-ion battery.

[0057] In some specific embodiments, the thickness d 2 of the positive electrode current collector can have a value range between 6 μm and 15 μm (specifically, such as 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc.); the density ρ of the positive electrode current collector has a value range between 2000 kg·m -3 and 3000 kg·m -3 (specifically, such as 2000 kg·m -3 , 2100 kg·m -3 , 2200 kg·m -3 , 2300 kg·m -3 , 2400 kg·m -3 , 2500 kg·m -3 , 2600 kg·m -3 , 2700 kg·m -3 , 2800 kg·m -3 , 2900 kg·m -3 , 3000 kg·m -3 , etc.); the heat capacity C p of the positive electrode current collector has a value range between 800 J·kg -1 ·°C -1 and 900 J·kg -1 ·°C-1 between (such as 800 J·kg -1 ·°C -1 、810 J·kg -1 ·°C -1 、820 J·kg -1 ·°C -1 、830 J·kg -1 ·°C -1 、840 J·kg -1 ·°C -1 、850 J·kg -1 ·°C -1 、860 J·kg -1 ·°C -1 、870 J·kg -1 ·°C -1 、880 J·kg -1 ·°C -1 、890 J·kg -1 ·°C -1 、900 J·kg -1 ·°C -1 etc.). Specifically, d 2 、ρ、C p are the thermal characteristic properties of the positive current collector. When the product of the three is larger, it is more difficult for the short-circuit point to fuse, and the risk of out-of-control is greater. Within the above range, it can effectively ensure that when the short-circuit point fuses, the material is not out of control, better ensuring the safety of the battery.

[0058] In some specific embodiments, the ratio L / W of the size L of the positive current collector in the first direction to the size W of the positive current collector in the second direction ranges from 0 to 30 (such as 1, 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, etc.). L / W determines the ohmic resistance inside the battery. The larger L / W is, the larger the ohmic resistance is, and the more heat the battery generates. At the same time, L / W determines the impedance of the positive current collector. The larger its value is, the greater the total heat generation of the battery cell before the short-circuit point fuses, and the greater the risk of out-of-control. Within the above range, the normal operation of the battery can be ensured, while the risk of out-of-control is relatively low, and the heat generation can be controlled within a certain range, thus avoiding damage to adjacent batteries or the outside caused by the heat generation of the battery.

[0059] In some specific embodiments, in the lithium-ion battery of the present application, there are no particular restrictions on the specific types of the positive electrode material layer and the negative electrode active material, and those skilled in the art can flexibly select and adjust according to actual needs. In some specific embodiments, the positive electrode material layer may include lithium iron phosphate material. In some specific embodiments, the negative electrode active material may include at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate. Thus, the matching with the above-mentioned thermal runaway conditions is better, and the risk of thermal runaway of the lithium-ion battery is lower.

[0060] In some specific embodiments, the lithium-ion battery may be a rectangular battery; further, the length of the lithium-ion battery may be 500 mm - 2500 mm (specifically, such as 500 mm, 800 mm, 1000 mm, 1500 mm, 1800 mm, 2000 mm, 2200 mm, 2500 mm, etc.). Specifically, it may be a lithium-ion battery with a housing having a certain strength (preferably a metal housing). The lithium-ion battery within this shape and size range has better matching with the above-mentioned thermal runaway conditions, and the risk of thermal runaway of the lithium-ion battery is lower.

[0061] It can be understood that in addition to the components described above, the lithium-ion battery may also have the necessary structures and components of a conventional lithium-ion battery. For example, it may include an external electrolyte or a solid electrolyte, necessary connection lines, etc. Specifically, all can refer to conventional technologies and will not be elaborated here too much.

[0062] In some specific embodiments, there are multiple electrode cores encapsulated in the housing, and the multiple electrode cores are divided into several electrode core groups, and the electrode core groups are connected in series. Specifically, if there are 15 electrode cores encapsulated in the housing and every 5 electrode cores are divided into an electrode core group, then there are 3 electrode core groups in the housing, and these 3 electrode core groups are connected in series.

[0063] In some specific embodiments, a packaging film is further provided between the housing and the electrode core, and the electrode core is encapsulated in the packaging film. Thus, the electrode core can be better protected to avoid problems such as breakage, improving the safety of the battery and extending the service life of the battery.

[0064] In another aspect of the present application, the present application provides a lithium-ion battery. According to an embodiment of the present application, the lithium-ion battery includes a housing and an electrode core received in the housing, the electrode core includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer loaded on the positive electrode current collector, and the positive electrode current collector satisfies the following conditions:

[0065]

[0066] Wherein, L is the dimension of the positive current collector in the first direction, W is the dimension of the positive current collector in the second direction, d 2 is the thickness of the positive current collector, ρ is the density of the positive current collector, C p is the heat capacity of the positive current collector. The first direction is parallel to the direction in which the current is led out from the positive current collector, and the second direction intersects with the first direction.

[0067] It can be understood that the housing, the positive electrode sheet, the negative electrode sheet, and the separator involved in this lithium-ion battery can all be consistent with the previous description, and will not be elaborated here one by one.

[0068] In another aspect of the present application, the present application provides a power battery module. According to an embodiment of the present application, the power battery module includes at least one of the aforementioned lithium-ion batteries. The possibility of thermal runaway and thermal diffusion of the power battery module is significantly reduced, and the use safety is significantly improved.

[0069] Specifically, in this power battery module, multiple lithium-ion batteries can be connected in series, in parallel, or in a combination of both. Some lithium-ion batteries can also be connected to form a module, and multiple modules are further connected to form a power battery module. Of course, specific designs and selections can be made according to actual needs and will not be described in detail here.

[0070] In yet another aspect of the present application, the present application provides a battery pack. According to an embodiment of the present application, the battery pack includes at least one of the aforementioned lithium-ion batteries or the aforementioned battery module. The battery pack has high use safety and a long service life.

[0071] In still another aspect of the present application, the present application provides an electric vehicle. According to an embodiment of the present application, the electric vehicle includes the aforementioned battery module or the aforementioned battery pack. The electric vehicle has excellent safety and a long service life.

[0072] It can be understood that in addition to the power battery module described above, the electric vehicle may also include the necessary structures and components of a conventional electric vehicle, such as a body, tires, an engine, a frame, an interior, etc. Specific implementations can be based on conventional technologies and will not be elaborated here in detail.

[0073] In another aspect of the present application, the present application provides an energy storage device. According to an embodiment of the present application, the energy storage device includes the aforementioned power battery module or the aforementioned battery pack. The probability of thermal runaway and thermal diffusion of the energy storage device is significantly reduced, and it has excellent safety and a long service life. The embodiments of the present application will be described in detail below.

[0074] In the following examples and comparative examples, a power battery module is used. The power battery module is formed by connecting multiple lithium-ion batteries in series. Each lithium-ion battery is a laminated battery. The positive current collector is aluminum foil, the positive electrode material is lithium iron phosphate material, the negative current collector is copper foil, the negative electrode material is graphite, the separator is a polyolefin separator, the electrolyte is a lithium hexafluorophosphate organic electrolyte, and the lithium-ion battery is a rectangular battery with a length of 1000 mm.

[0075] Performance test:

[0076] The needle penetration test is carried out according to the method of "GB / T 31485-2015 Safety Requirements and Test Methods for Power Batteries for Electric Vehicles". The specific needle penetration procedure is as follows:

[0077] Charging: At room temperature, the single battery is first discharged to the cut-off voltage of 2.0 V at a current of 1C + 0.2C, left standing for 30 min, and then charged to 3.8 V at a current of 1C + 0.2C.

[0078] Needle penetration: Use a high-temperature resistant steel needle with a diameter and a taper of 45° - 60° (the surface of the needle is smooth, without rust, oxide layer and oil stain), and penetrate from the direction perpendicular to the battery plate at a speed of (25 ± 5) mm / s. The penetration position should be close to the geometric center of the punctured surface, and the steel needle stays in the battery for 1 h for observation.

[0079] The parameters and test results of each example and comparative example are shown in the following table:

[0080]

[0081]

[0082] Among them,

[0083] It can be seen from the test results that when A is greater than 850, the battery fails to pass the needle penetration test and thermal runaway occurs. When A is less than 850 and greater than 3, the battery can pass the needle penetration test and thermal runaway does not occur, indicating that the lithium-ion battery meeting the conditions of this application has a lower runaway risk and higher safety.

[0084] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0085] Although the embodiments of this application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting this application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A lithium-ion battery, the lithium-ion battery comprising a housing and an electrode core encapsulated within the housing, the electrode core including a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet including a positive electrode current collector and a positive electrode material layer loaded on the positive electrode current collector, characterized in that, defining the positive electrode current collector as an effective component, the effective component satisfying the following conditions: Wherein, L is the dimension of the effective component in the first direction, W is the dimension of the effective component in the second direction, d 2 is the thickness of the effective component, ρ is the density of the effective component, C p is the heat capacity of the effective component, the first direction is parallel to the direction in which the current is led out in the effective component, and the second direction intersects the first direction; The thickness d of the positive current collector 2 ranges from 6 μm to 10 μm; the ratio L / W of the dimension L of the positive electrode current collector in a first direction to the dimension W of the positive electrode current collector in a second direction ranges from 2 to 30; the lithium-ion battery satisfies at least one of the following conditions: the lithium-ion battery is a square battery; the length of the lithium-ion battery is 500 mm - 2500 mm.

2. The lithium-ion battery according to claim 1, characterized in that, the effective component satisfies the following conditions:

3. The lithium-ion battery according to claim 1, characterized in that, a positive electrode tab is led out from one side of the positive electrode current collector, and the first direction is parallel to the direction in which the positive electrode tab is led out.

4. The lithium-ion battery according to claim 3, characterized in that, the second direction is perpendicular to the first direction.

5. The lithium-ion battery according to claim 1, characterized in that, the positive electrode current collector satisfies at least one of the following conditions: The density ρ of the positive current collector ranges from 2000 kg·m -3 to 3000 kg·m -3 ; The hot melt C of the positive current collector p has a value range of 800 J·kg -1 ·K -1 -900 J·kg -1 ·K -1 between them.

6. The lithium-ion battery according to claim 1, characterized in that, the material of the positive electrode current collector includes aluminum.

7. The lithium-ion battery according to claim 1, characterized in that, the electrode core satisfies at least one of the following conditions: the positive electrode material layer includes a lithium iron phosphate material; the negative electrode includes a negative electrode active material, and the negative electrode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate.

8. The lithium-ion battery according to any one of claims 1-7, characterized in that, the electrode cores encapsulated within the housing include a plurality of them, and the plurality of electrode cores are divided into several electrode core groups, and the electrode core groups are connected in series.

9. The lithium-ion battery according to any one of claims 1-7, characterized in that, a packaging film is further provided between the housing and the electrode core, and the electrode core is encapsulated within the packaging film.

10. A power battery module, characterized in that, it includes at least one lithium-ion battery according to any one of claims 1-9.

11. A battery pack, characterized in that, it includes at least one lithium-ion battery according to any one of claims 1-9 or the power battery module according to claim 10.

12. An electric vehicle, characterized in that, it includes the power battery module according to claim 10 or the battery pack according to claim 11.

13. An energy storage device, characterized in that, it includes the power battery module according to claim 10 or the battery pack according to claim 11.

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