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 electrode plate comprises a positive electrode plate current collector and a positive electrode material layer loaded on the positive electrode current collector, one of the positive electrode current collector, the positive electrode material layer, the negative electrode plate and the separator with the lowest melting point is defined as an effective component, and the effective component meets the following condition: # imgabs0 #. According to the lithium ion battery, parameters such as the number of layers of the pole core parts and sizes in different directions are reasonably optimized and designed, so that the safety of the battery is greatly improved, and the probability of thermal runaway or thermal diffusion of the battery is effectively reduced according to the lithium ion battery meeting the conditions.

Description

Technical Field

[0001] The present 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

[0002] The unique characteristics of lithium-ion batteries have been applied in more and more fields. Especially in the aspect of power batteries, it has 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, fire, and explosion where the self-temperature rise rate of the battery changes sharply due to the battery heat release chain reaction) 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 fire and explosion. Currently, the safety of using lithium-ion batteries still faces challenges.

[0003] Content of the Application

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of the present invention is to provide a lithium-ion battery that can effectively improve the thermal runaway problem and enhance the safety of use.

[0005] 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:

[0006]

[0007] where n is the number of layers of the effective component, 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. In this lithium-ion battery, by reasonably optimizing and designing parameters such as the number of layers of the electrode core components and the dimensions 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 occurring is effectively reduced.

[0008] In another aspect of the present application, the present application provides a lithium-ion battery. According to an embodiment of the present invention, 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:

[0009]

[0010] where n is the number of layers of the positive electrode current collector, 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 heat capacity of the positive electrode current collector. The first direction is parallel to the current extraction direction in the positive electrode current collector, and the second direction intersects the first direction.

[0011] In yet 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.

[0012] 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 aforementioned lithium-ion batteries or the aforementioned battery module. The battery pack has high use safety and a long service life.

[0013] In 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 power battery module or the aforementioned battery pack. The electric vehicle has excellent safety and a long service life.

[0014] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of a laminated electrode core according to an embodiment of the present application.

[0016] Figure 2 is Figure 1 a schematic cross-sectional structural diagram of a positive electrode along line A-A in

[0017] Figure 3 It is a schematic structural diagram of the flattened state of the laminate that constitutes the wound electrode core in an embodiment of the present application.

[0018] Figure 4 It is a schematic structural diagram of the wound electrode core in an embodiment of the present application.

[0019] Figure 5 It is a schematic structural diagram of the wound electrode core in an embodiment of the present application.

[0020] Figure 6 is Figure 4 and Figure 5 a schematic plan view of one winding section in

[0021] Figure 7 is Figure 6 a schematic cross-sectional structure diagram along line B-B in

[0022] Figure 8 It is a schematic plan view of one winding section in another embodiment of the present application. Detailed implementation manners

[0023] The embodiments of the present invention will be described in detail below. The following described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0024] In one aspect of the present application, the present application provides a lithium-ion battery. According to the embodiments 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:

[0025]

[0026] where n is the number of layers of the effective component, 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 melting 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 number of layers of the electrode core component and the dimensions 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 additional components, the battery system design is not changed, and there is no additional cost increase.

[0027] In some embodiments, the effective component satisfies the following conditions:

[0028]

[0029] Thus, the safety of the lithium-ion battery is further improved, and the probabilities of thermal runaway and thermal diffusion are further reduced.

[0030] 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, as follows:

[0031] According to the general heat balance equation:

[0032]

[0033] The boundary conditions are:

[0034]

[0035] 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 outer 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, and T room represents the room temperature.

[0036] For the one-dimensional heat diffusion model, there is:

[0037]

[0038] Where Q is a heat given instantaneously at the point x = 0 at t = 0, △T is the increment of the temperature at a 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 thermal conductivity coefficient α = k / (ρc), k is the thermal conductivity of the heat conductor, and m 2 = 2h / (kδ).

[0039] Based on the above equations and models, combined with the inventors' actual research experience 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 number, size, and thermodynamics of the effective components in the battery, when a short circuit occurs in the battery, the short circuit point is quickly melted, thus cutting off the short circuit point and preventing further heat generation. At the same time, it is ensured that the material does not reach the runaway point, which can greatly ensure the safety of the battery and thus avoid the occurrence of thermal runaway, greatly improving the safety of the battery.

[0040] Specifically, the lithium-ion battery of this application can be a liquid battery, a solid-state 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-state 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.

[0041] 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.

[0042] 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.

[0043] 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 current collector. 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.

[0044] 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 they can be arranged opposite to each other (refer to Figure 1 and Figure 7 ), and the direction in which the tabs lead out is the direction in which the current is led out.

[0045] In the electrode core, a plurality of positive electrode sheets 10 and negative electrode sheets 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. Alternatively, the positive electrode plates, the separator, and the negative electrode plates can be stacked and then wound to form a wound electrode core (refer to the structural schematic diagram Figure 2 ). The specific method can be referred to the conventional technology and will not be described in detail here.

[0046] It should be noted that for the stacked electrode core, specifically refer to Figure 1 , which includes a plurality of alternately stacked positive electrode plates 10 and negative electrode plates 20, and a separator (not shown in the figure) is provided between adjacent positive electrode plates 10 and negative electrode plates 20. At this time, n is the number of stacked effective components, L is the dimension of an effective component in the first direction, W is the dimension of an effective component in the second direction, and d 2 is the thickness of an effective component (dimension along the stacking direction).

[0047] 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 successively stacked positive electrode plate 10, separator 40, and negative electrode plate 20 are defined as the stacked body 30, and the stacked body 30 is divided into a plurality of successively connected winding segments 31 (refer to Figure 3 ). When in the wound state, a plurality of winding segments 31 are successively stacked (refer to Figure 4 ). At this time, n is the number of winding segments (or twice the number of winding turns of the effective component), L is the dimension of the effective component in the first direction in a winding segment, W is the average value of the dimensions of the effective component in the second direction in a plurality of winding segments, and d 2 is the thickness of the effective component in a winding segment.

[0048] In addition, it should be noted that the second direction described in this article intersects with the first direction. Specifically, it means that the 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 angle between the first direction and the second direction can be specifically 90 degrees, that is, the first direction and the second direction are perpendicular.

[0049] Specifically, according to the commonly used materials of various components 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 is not out of control, which can greatly ensure the safety of the battery. Among the various short-circuit forms inside the battery that cause 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 sheet, etc., after the positive current collector comes into contact with the negative electrode material and causes a short circuit, the heat generated 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 then easily 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.

[0050] The following further describes the solution of the present application in detail with the positive current collector as an effective component.

[0051] 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.

[0052] Specifically, the positive electrode tab can be welded to the positive current collector or 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.

[0053] Furthermore, 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 positive electrode sheets 10 and negative electrode sheets 20 alternately laminated. n is the number of the positive current collectors 12 in the plurality of positive electrode sheets 10, L is the dimension of the positive current collector 12 in one positive electrode sheet 10 in the first direction, W is the dimension of the positive current collector 12 in one positive electrode sheet 10 in the second direction, d 2 is the thickness of the positive current collector 12 in one positive electrode sheet 10, Figure 1 andFigure 2 In the shown electrode core, the number of layers n of the positive current collector is 3, L, W, and d 2 As shown in the figure.

[0055] In some other embodiments, the electrode core in the lithium-ion battery can be a wound electrode core. Refer 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, a plurality of winding segments 31 are stacked. Each winding segment 31 includes a positive electrode sheet 10, a separator 40, and a negative electrode sheet 20 stacked in sequence. n is the number of the winding segments 31, L is the dimension of the positive current collector 12 in one winding segment 31 in the first direction, W is the average value of the dimensions of the positive current collector 12 in a plurality of winding segments 31 in the second direction, and d 2 is the thickness of the positive current collector 12 in one winding segment 31. Specifically, Figures 3 to 7 in the shown wound electrode core, n = 5, W = (W1 + W2 + W3 + W4 + W5) / 5, L = L1.

[0056] In some embodiments, the material of the positive current collector includes aluminum, such as aluminum foil, and the negative current collector is copper foil. When making reasonable designs 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 fusing 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 of the positive current collector 2 can be in the range of 6 μm - 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 current collector is in the range of 2000 kgm -3 ~3000 kgm -3 (specifically, such as 2000 kgm -3 , 2100 kgm -3 , 2200 kgm -3 , 2300 kgm -3 , 2400 kgm -3 , 2500 kgm -3 , 2600 kgm -3 , 2700 kgm -3 , 2800 kgm -3 , 2900 kgm -3 , 3000 kgm -3 etc.); the heat capacity C of the positive current collector pThe value range is from 800 J·kg -1 ·K -1 -900 J·kg -1 ·K -1 (specifically, such as 800 J·kg -1 ·K -1 , 810 J·kg -1 ·K -1 , 820 J·kg -1 ·K -1 , 830 J·kg -1 ·K -1 , 840 J·kg -1 ·K -1 , 850 J·kg -1 ·K -1 , 860 J·kg -1 ·K -1 , 870 J·kg -1 ·K -1 , 880 J·kg -1 ·K -1 , 890 J·kg -1 ·K -1 , 900 J·kg -1 ·K -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 number of layers n of the positive current collector has a value range between 1 and 150 (specifically, such as 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, etc.). n is the total number of short-circuit layers of the positive current collector. When n is larger, the heat released by the short circuit is greater, and the risk of out-of-control is also greater. Within the above range, the energy density of the battery can be ensured while the risk of out-of-control is relatively low.

[0059] 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 has a value range between 0 and 30 (specifically, such as 1, 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, etc.). L / W determines the impedance of the positive current collector. The larger its value, the greater the total heat generation of the electrode core 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.

[0060] In some specific embodiments, in the lithium-ion battery of the present application, there are no particular limitations on the specific types of the positive electrode material layer and the negative electrode active material. 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 sheet includes a negative electrode active material, and 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.

[0061] 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.). The lithium-ion battery within this range of shapes and sizes has better matching with the above-mentioned thermal runaway conditions, and the risk of thermal runaway of the lithium-ion battery is lower.

[0062] 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 electrolyte or a solid electrolyte, necessary connection lines, etc. Specifically, all can refer to conventional technologies and will not be elaborated here too much.

[0063] 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 one electrode core group, then there are 3 electrode core groups in the housing, and these 3 electrode core groups are connected in series.

[0064] 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, improve the safety of the battery, and extend the service life of the battery.

[0065] In another aspect of the present application, the present application provides a lithium-ion battery. According to an embodiment of the present invention, 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:

[0066]

[0067] Wherein, n is the number of layers of the positive current collector, 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, and d 2 is the thickness of the positive current collector, ρ is the density of the positive current collector, and C p is the heat capacity of the positive current collector. The first direction is parallel to the current extraction direction in the positive current collector, and the second direction intersects the first direction.

[0068] It can be understood that the housing, positive electrode sheet, negative electrode sheet, and separator involved in this lithium-ion battery can all be the same as those described above, and will not be elaborated here one by one.

[0069] 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 lithium-ion batteries described above. The possibility of thermal runaway and thermal diffusion of the power battery module is significantly reduced, and the use safety is significantly improved.

[0070] 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.

[0071] 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 lithium-ion batteries described above or the power battery module described above. The battery pack has high use safety and a long service life.

[0072] 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 battery module described above or the battery pack described above. The electric vehicle has excellent safety and a long service life.

[0073] 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, interior decoration, etc., which can be carried out according to conventional technologies and will not be elaborated here in detail.

[0074] 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 power battery module described above or the battery pack described above. 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.

[0075] The embodiments of the present application will be described in detail below.

[0076] 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.

[0077] Performance test:

[0078] The needle puncture experiment 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 puncture procedure is as follows:

[0079] 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.

[0080] Needle puncture: 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.

[0081] The parameters and test results of each example and comparative example are shown in the following table:

[0082]

[0083]

[0084]

[0085] Among them,

[0086] It can be seen from the test results that when A is greater than 2000, the battery fails to pass the needle puncture experiment and thermal runaway occurs. When A is less than 2000 and greater than 80, the battery can pass the needle puncture experiment 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.

[0087] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", 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 the present invention. In this specification, the schematic expressions 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 any one or more embodiments or examples in a suitable manner. 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.

[0088] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

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, the positive electrode current collector satisfies the following conditions: Wherein, n is the number of layers of the positive current collector, 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, and d 2 is the thickness of the positive current collector, ρ is the density of the positive current collector, and 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 the first direction; the thickness d 2 of the positive current collector ranges from 6 μm to 10 μm; the ratio L / W of the dimension L of the positive electrode current collector in the first direction and the dimension W in the second direction has a value range between 2 and 30; the lithium-ion battery satisfies at least one of the following conditions: the lithium-ion battery is a rectangular 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 positive electrode current collector 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 ; the number of layers n of the positive current collector has a value range between 1 and 150.

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 sheet 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 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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