A battery module and a battery pack

Abstract

The application provides a battery module and a battery pack, wherein the battery module comprises a first battery pack, a second battery pack and a shunt, the first battery pack and the second battery pack are connected in parallel through the shunt; the first battery pack comprises a plurality of first battery cells connected in series, the second battery pack comprises a plurality of second battery cells connected in series, the charge-discharge rate of the first battery cell is greater than that of the second battery cell, and the energy density of the second battery cell is greater than that of the first battery cell. By combining the use of the rate type battery cell and the energy type battery cell, the performance of different battery cells can be exerted in a low temperature environment, thereby improving the energy density of the battery pack, and further enabling the battery pack to have excellent discharge performance in a low temperature environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a battery module and a battery pack. BACKGROUND

[0002] Lithium ion batteries have the advantages of large specific capacity, high working voltage, long cycle life, portability, safety and environmental protection, and small environmental pollution, and are widely used in various products. However, with the increasing complexity of the use environment of the products, the battery as an energy source is required to have better environmental suitability. And the low temperature performance (low temperature generally refers to below-10℃) as an important indicator for evaluating the environmental suitability of the battery is particularly important.

[0003] The commonly used lithium ion battery will increase the polarization of the battery when used at low temperature, and the discharge voltage will be reached too early, resulting in too little discharge capacity or no discharge at all. This directly affects the performance of the lithium ion battery, and also affects the normal use of the lithium ion battery, and further affects the normal use of the electronic product installed with the lithium ion battery. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a battery module and a battery pack, which can exert the performance of different battery cells in a low temperature environment by using rate type battery cells and energy type battery cells in combination, thereby improving the energy density of the battery pack, and further enabling the battery pack to have excellent discharge performance in a low temperature environment.

[0005] In a first aspect, the embodiments of the present application provide a battery module, comprising: a first battery pack, a second battery pack and a shunt, the first battery pack and the second battery pack being connected in parallel through the shunt.

[0006] The first battery pack comprises a plurality of first battery cells connected in series, the second battery pack comprises a plurality of second battery cells connected in series, the charge-discharge rate of the first battery cell is greater than the charge-discharge rate of the second battery cell, and the energy density of the second battery cell is greater than the energy density of the first battery cell.

[0007] In an optional embodiment of the present application, the cell capacity of the first battery cell is greater than the cell capacity of the second battery cell.

[0008] In an optional embodiment of the present application, the first battery cells in the first battery pack and the second battery cells in the second battery pack are arranged in an interleaved stack.

[0009] In an optional embodiment of the present application, the number of second battery cells in the second battery pack is greater than the number of first battery cells in the first battery pack, and each first battery cell is arranged between two second battery cells.

[0010] In one optional embodiment of this application, the first battery cell and the second battery cell have the same length and the same width.

[0011] In one optional embodiment of this application, the first battery cell and the second battery cell satisfy the following conditions:

[0012] The areal density of the second cell is greater than that of the first cell;

[0013] The compaction density of the second cell is greater than that of the first cell;

[0014] The positive and negative electrode ratio of the first battery cell is greater than that of the second battery cell;

[0015] The electrolyte in the first battery cell is a low-temperature, high-rate electrolyte, while the electrolyte in the second battery cell is an energy-type electrolyte.

[0016] In one alternative embodiment of this application, the first battery cell is a wound structure, and the second battery cell is a stacked structure or a wound structure.

[0017] Secondly, embodiments of this application provide a battery pack, the battery pack including a plurality of battery modules as described above, the plurality of battery modules being connected in series and / or in parallel.

[0018] In one alternative embodiment of this application, the battery pack further includes a circuit board, on which the plurality of battery modules are stacked.

[0019] In one alternative embodiment of this application, the battery pack further includes a housing and thermally conductive foam, the plurality of battery modules and the circuit board are disposed within the housing, and the thermally conductive foam is provided in the gaps between the plurality of battery modules and the housing and between the circuit board and the housing.

[0020] This application provides a battery module and battery pack. The battery module includes a first battery pack, a second battery pack, and a shunt. The first and second battery packs are connected in parallel via the shunt. The first battery pack includes multiple first cells connected in series, and the second battery pack includes multiple second cells connected in series. The charge / discharge rate of the first cells is greater than that of the second cells, and the energy density of the second cells is greater than that of the first cells. By combining rate-capable and energy-capable cells, this application can leverage the performance of different cells at low temperatures, thereby increasing the energy density of the battery pack and enabling it to exhibit excellent discharge performance at low temperatures. This improves the performance of lithium-ion batteries while ensuring their normal operation, thus guaranteeing the normal use of electronic products equipped with lithium-ion batteries.

[0021] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A circuit diagram of a battery module provided in an embodiment of this application;

[0024] Figure 2 This is a schematic diagram of the structure of a battery module provided in an embodiment of this application;

[0025] Figure 3 A circuit diagram of a battery pack provided in an embodiment of this application;

[0026] Figure 4 This is a circuit diagram of another battery pack provided in an embodiment of this application;

[0027] Figure 5 This is a circuit diagram of another battery pack provided in an embodiment of this application. Detailed Implementation

[0028] 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, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. Based on the embodiments of this application, every other embodiment obtained by those skilled in the art without inventive effort falls within the scope of protection of this application.

[0029] In the description of the embodiments of this application, it should be noted that the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing the invention 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, and therefore should not be construed as a limitation of the invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "provided with," "installed," "connected," and "connected" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] First, the applicable application scenarios of this application are introduced. This application can be applied to the field of lithium battery technology. Lithium-ion batteries have advantages such as large specific capacity, high operating voltage, long cycle life, portability, safety, environmental friendliness, and low environmental pollution, and are widely used in various products. With the advancement of technology and the development of society, portable products are developing towards miniaturization, intelligence, and multi-functionality, and the complexity of the product usage environment is gradually increasing. However, with the increasing complexity of the product usage environment, batteries as energy sources are required to have better environmental adaptability. Low-temperature performance (low temperature generally refers to below -10℃) is a crucial indicator for evaluating the environmental adaptability of batteries, and thus becomes particularly important.

[0032] Currently used lithium-ion batteries experience increased polarization when discharged in low-temperature environments, reaching the discharge voltage prematurely. This results in insufficient discharge capacity or even no discharge at all. This directly impacts the performance of lithium-ion batteries, their normal operation, and consequently, the functionality of electronic products using them. With the expanding applications of lithium-ion batteries, there is an urgent need to address the discharge problem in low-temperature environments.

[0033] Based on this, embodiments of this application provide a battery module and battery pack that can bring out the performance of different cells in low-temperature environments, thereby improving the energy density of the battery pack and enabling the battery pack to have excellent discharge performance in low-temperature environments.

[0034] Please see Figure 1 , Figure 1This is a circuit diagram of a battery module provided in an embodiment of this application. Figure 1 As shown, the battery module provided in this application embodiment includes: a first battery pack 101, a second battery pack 102, and a shunt 103. The first battery pack 101 and the second battery pack 102 are connected in parallel through the shunt 103.

[0035] The first battery pack 101 includes a plurality of first cells 1011 connected in series, and the second battery pack 102 includes a plurality of second cells 1021 connected in series. The charge-discharge rate of the first cells 1011 is greater than that of the second cells 1021, and the energy density of the second cells 1021 is greater than that of the first cells 1011.

[0036] Here, the first battery pack 101 includes multiple first cells 1011 connected in series, and the second battery pack 102 includes multiple second cells 1021 connected in series. The first cells are rate-controlled cells, and the second cells are energy-controlled cells. Specifically, the charge / discharge rate of the first cells is greater than that of the second cells, and the energy density of the second cells is greater than that of the first cells. This allows the first cells to generate heat first, and the generated energy is used to heat the second cells, thus achieving low-temperature performance of the battery pack.

[0037] In one optional embodiment, the first battery cell and the second battery cell satisfy the following conditions:

[0038] (1) The areal density of the second cell is greater than that of the first cell.

[0039] Areal density refers to the density per unit area of ​​a battery cell, and is calculated as weight / volume. As areal density increases, the internal resistance of the cell increases, resulting in a significant increase in internal resistance during charge-discharge cycles, leading to a decrease in discharge specific capacity and a deterioration in cycle performance.

[0040] Specifically, the areal density of the second cell is defined as ρ. b The areal density of the first battery cell is ρ a , then ρ b =k1*ρ a The value of k1 ranges from 1 to 1.6.

[0041] (2) The compaction density of the second cell is greater than that of the first cell.

[0042] Compacted density = areal density / material thickness; the higher the compacted density, the higher the battery capacity.

[0043] Specifically, the compaction density of the second cell is defined as σ. b The compaction density of the first cell is σ. a Then σ b =k2*σ aThe value of k2 ranges from 1 to 1.6.

[0044] (3) The positive and negative electrode ratio of the first cell is greater than that of the second cell.

[0045] The positive and negative electrode ratio refers to the N / P ratio, which is the ratio of the negative electrode capacity to the positive electrode capacity. The formula for calculating N / P is: N / P = Negative electrode areal density × Active material ratio × Active material discharge specific capacity / Positive electrode areal density × Active material ratio × Active material discharge specific capacity. Here, as the N / P ratio increases, the battery capacity will also increase.

[0046] Specifically, the positive and negative electrode ratio of the first battery cell is defined as follows: The positive and negative electrode ratio of the second battery cell is but The value of k3 ranges from 1 to 1.5.

[0047] (4) The electrolyte of the first cell is a low-temperature and high-rate electrolyte, and the electrolyte of the second cell is an energy-type electrolyte.

[0048] The electrolyte in the first cell has a significant impact on the low-temperature performance of lithium batteries. By appropriately designing the solvent and adjusting the ratio, the viscosity of the electrolyte can be effectively reduced, thus improving its low-temperature performance. Furthermore, the electrolyte in the first cell is a high-rate electrolyte, which can improve the battery's rate discharge performance and cycle performance.

[0049] For example, the electrolyte of the first battery cell can be formulated by mixing lithium electrolyte salt, non-aqueous organic solvent, film-forming additive, low-melting-point and low-viscosity additive, and low-temperature conductive additive. By reasonably adjusting the composition ratio, the battery can be guaranteed to have good cycle performance at room temperature, and the rate discharge performance and conductivity of the low-temperature electrolyte can be improved at low temperatures, effectively expanding the application range of lithium-ion batteries in low-temperature environments.

[0050] Based on the above, it can be seen that the first cell is an ultra-low temperature performance cell with better heat dissipation and dynamic performance, while the second cell is a cell with relatively poor heat dissipation, relatively high energy density, and high energy density.

[0051] With the above settings, the first cell can be defined as a rate-capacity cell and the second cell as an energy-capacity cell. By combining the advantages of different types of cells, the rate-capacity cell and the energy-capacity cell can be combined to enable them to perform at low temperatures and high rates, thereby improving the energy density of the battery module.

[0052] In one optional embodiment, the cell capacity of the first battery cell is different from that of the second battery cell. Specifically, the cell capacity of the first battery cell is greater than that of the second battery cell.

[0053] Here, cell capacity actually refers to battery capacity. Battery capacity is one of the important performance indicators for measuring battery performance. Cell capacity represents the total capacity of the battery, and the unit is usually milliampere-hours (mAh).

[0054] Here, the cell capacity of the first cell is defined as Ca, and the cell capacity of the second cell is defined as Cb. The cell capacities are related as follows: Ca = K4 * Cb, where K4 > 1.2.

[0055] Since it is necessary to make full use of the heat generated by the first battery cell to heat the second battery cell, the first battery pack composed of the first battery cell needs to be charged first to release heat. As a result, the cell capacity of the first battery cell needs to be greater than that of the second battery cell. This ensures that the first battery pack can be charged or discharged synchronously with the second battery pack when the first battery pack is charged or discharged first.

[0056] In this embodiment, a first battery pack and a second battery pack are connected in parallel via a shunt in a circuit. A shunt is an instrument for measuring direct current, based on the principle that a voltage is generated across a resistor when direct current flows through it. The shunt in this embodiment can be configured to handle different currents in the parallel circuits as needed. For example, if the total current is 10A, the shunt can divide the current into 3A and 7A, distributing them to the two parallel circuits respectively, thus achieving the function of current shunting.

[0057] Furthermore, in this embodiment of the application, the first battery pack and the second battery pack are connected in parallel by a shunt, and different currents are distributed to the branch where the first battery pack is located and the branch where the second battery pack is located by the shunt, wherein the first current in the branch where the first battery pack is located is greater than the second current in the branch where the second battery pack is located.

[0058] Specifically, the shunt is used to shunt current in the parallel circuit of the battery module according to a preset setting. In this embodiment, the shunt needs to be set according to the cell capacity of the first cell and the second cell. The current in the shunt of the first battery pack composed of the first cells connected in series is denoted as I. a The current in the branch circuit containing the second battery pack, which consists of the second battery cells connected in series, is denoted as I. b The relationship between the magnitudes of the currents satisfies I a =K5*I b The value of K5 ranges from 1.1 to 10.

[0059] Here, by taking advantage of the respective advantages of different types of battery cells, a shunt is cleverly used during use to separate the current according to the cell capacity of the first and second battery cells, so that the two types of battery cells can be fully charged and discharged in the same charging and discharging time, so as to make full use of the battery pack's full capacity.

[0060] This embodiment of the application uses a shunt to connect rate-type cells and energy-type cells in parallel, allowing the shunt to distribute current to the parallel circuit according to a preset value. This allows the cell with superior low-temperature performance and rate performance (the first cell) to generate heat first, which then heats the second cell. Furthermore, by utilizing the respective advantages of different types of cells, the advantages of the cells are maximized in the battery pack. By cleverly combining rate-type cells and energy-type cells, their respective performances are brought into play at low temperatures and high rates, thereby improving the energy density of the battery module and enabling the battery module to have excellent discharge performance in low-temperature environments.

[0061] Furthermore, such as Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of a battery module provided in an embodiment of this application. Figure 2 In this battery module, the first cells in the first battery pack and the second cells in the second battery pack are stacked alternately. For example, the first battery pack 101 in this battery module includes three first cells 1011 connected in series, and the second battery pack 102 includes four second cells 1021 connected in series. The first cells 1011 and the second cells 1021 are stacked alternately.

[0062] Here, the first cell 1011 in the first battery pack 101 and the second cell 1021 in the second battery pack 102 are stacked alternately to achieve the required voltage. This allows the heat generated by the first cell 1011 to be evenly diffused to the space where the second cell 1021 is located, thereby making the second cell 1021 heat up evenly and effectively improving the low-temperature performance of the existing battery pack.

[0063] In one optional embodiment, the number of cells in the second battery pack is greater than the number of cells in the first battery pack, and each first cell is disposed between two second cells.

[0064] For example, the number of first cells in the first battery pack is defined as n, and the number of second cells in the second battery pack is n+1. This allows for the following stacking sequence: second cell, first cell, second cell, first cell, second cell, and so on, with each first cell placed between two second cells to fully utilize the heat generated by the first cells to heat the second cells. The stacking order can be referenced from [reference needed]. Figure 2 The diagram shows the structure of the battery module.

[0065] This application embodiment achieves a self-heating method for the battery module by placing each first battery cell between two second battery cells and making full use of the heat generated by the first battery cell to heat the second battery cell. This improves the charging and discharging capability of the second battery cell and enhances the low-temperature performance of the existing battery pack. Compared with the existing technology that achieves the low-temperature performance of the battery pack through external heating, this application embodiment can utilize the advantages of the battery cell itself to achieve the low-temperature performance of the battery pack.

[0066] In one alternative embodiment, the first battery cell and the second battery cell have the same length and the same width.

[0067] In this embodiment, the first and second battery cells have the same dimensions (length and width), but their thicknesses may be the same or different. Here, it is only necessary to ensure that the length and width of the first and second battery cells are the same, which facilitates a more stable stacking of the first and second battery cells.

[0068] In one optional embodiment, the first battery cell has a wound structure, and the second battery cell has a laminated structure or a wound structure. For example, the first battery cell is a wound cell, and the second battery cell is a laminated cell or a wound cell.

[0069] Specifically, wound cells typically involve first ultrasonically welding the tabs to the current collector, using aluminum tabs for the positive electrode and nickel tabs for the negative electrode. Then, the positive and negative electrodes and the separator are arranged in the order of positive electrode-separator-negative electrode-separator, and finally assembled into a cylindrical or square cell by winding. Laminated cells, on the other hand, typically use the current collector as the lead-out tabs, and the positive and negative electrodes and the separator are stacked layer by layer in the order of positive electrode-separator-negative electrode to form a laminated cell. Laminated cells can be constructed using either a direct lamination method where the separator is cut, or a folding method where the separator is not cut, using a Z-shaped lamination.

[0070] The main reason why the first cell described in this application embodiment is a wound cell is that the internal resistance of the wound cell is relatively larger than that of the laminated cell. This application embodiment utilizes its large internal resistance to heat the adjacent second cell using the heat generated during charging and discharging.

[0071] This allows the low-temperature, high-rate-performance cells to generate heat first, and the heat generated by the rate-performance cells is used to heat the energy-type cells, thereby achieving a self-heating method for the battery module, improving the charging and discharging capabilities of the energy-type cells, and improving the low-temperature performance of the battery pack.

[0072] Based on the same concept, embodiments of this application provide a battery pack, including multiple such... Figure 1 and Figure 2 The battery modules shown are multiple battery modules connected in series and / or in parallel. For example... Figures 3 to 5 As shown,Figure 3 Multiple battery modules 10 are shown connected in series. Figure 4 Multiple battery modules 10 are shown connected in parallel. Figure 5 Multiple battery modules 10 are shown connected in series and in parallel.

[0073] The description of the battery module in the battery pack can be found above. Figure 1 and Figure 2 The description is as follows, and it can achieve the same technical effect, so I will not go into details.

[0074] Here, the battery pack is made up of multiple battery modules connected in series, in parallel, or in a series-parallel configuration. Connecting multiple battery modules in series can achieve the purpose of increasing voltage, while connecting multiple battery modules in parallel can achieve the purpose of increasing capacity.

[0075] In one alternative embodiment, the battery pack further includes a circuit board on which multiple battery modules are stacked.

[0076] By stacking battery modules on a circuit board, the battery modules can be placed more neatly, thus saving space.

[0077] In one alternative embodiment, the battery pack further includes a housing and thermally conductive foam, with multiple battery modules and circuit boards disposed within the housing, and thermally conductive foam provided in the gaps between the multiple battery modules and the housing, as well as between the circuit boards and the housing.

[0078] Here, the housing is used to mount multiple battery modules and circuit boards to prevent them from being impacted. Thermally conductive foam is installed in the gaps between the multiple battery modules and the housing, as well as between the circuit boards and the housing, to act as a buffer within the housing and prevent external impacts from affecting the battery modules and circuit boards.

[0079] The battery pack provided in this application embodiment uses a shunt to connect rate-type cells and energy-type cells in parallel, so that the shunt distributes the current to the parallel circuit according to a preset amount. In this way, the cell with better low-temperature performance and rate performance (the first cell) can generate heat first to heat the second cell. In this way, the advantages of different types of cells are fully utilized to maximize the advantages of the cells in the battery pack. By cleverly combining rate-type cells and energy-type cells, they can exert their respective performance at low temperature and high rate, thereby improving the energy density of the battery module and enabling the battery module to have excellent discharge performance in low-temperature environments.

[0080] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The scope of protection of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application. Such modifications, changes, 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, and should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A battery module, characterized in that, The battery module includes: a first battery pack, a second battery pack, and a current shunt, wherein the first battery pack and the second battery pack are connected in parallel through the current shunt; The first battery pack includes a plurality of first cells connected in series, and the second battery pack includes a plurality of second cells connected in series. The charge-discharge rate of the first cells is greater than that of the second cells, and the energy density of the second cells is greater than that of the first cells. The current in the branch circuit of the first battery pack composed of the first cells connected in series is denoted as Ia, and the current in the branch circuit of the second battery pack composed of the second cells connected in series is denoted as Ib. The relationship between the current magnitudes satisfies Ia = K5 * Ib, where the value of K5 ranges from 1.1 to 10.

2. The battery module according to claim 1, characterized in that, The capacity of the first battery cell is greater than that of the second battery cell.

3. The battery module according to claim 1, characterized in that, The first cell in the first battery pack and the second cell in the second battery pack are stacked alternately.

4. The battery module according to claim 3, characterized in that, The number of second cells in the second battery pack is greater than the number of first cells in the first battery pack, and each first cell is disposed between two second cells.

5. The battery module according to claim 3, characterized in that, The first battery cell and the second battery cell have the same length and the same width.

6. The battery module according to claim 1, characterized in that, The first battery cell and the second battery cell satisfy the following conditions: The areal density of the second cell is greater than that of the first cell; The compaction density of the second cell is greater than that of the first cell; The positive and negative electrode ratio of the first battery cell is greater than that of the second battery cell; The electrolyte in the first battery cell is a low-temperature, high-rate electrolyte, while the electrolyte in the second battery cell is an energy-type electrolyte.

7. The battery module according to claim 1, characterized in that, The first battery cell has a wound structure, and the second battery cell has a stacked structure or a wound structure.

8. A battery pack, characterized in that, The battery pack includes a plurality of battery modules as described in any one of claims 1 to 7, wherein the plurality of battery modules are connected in series and / or in parallel.

9. The battery pack according to claim 8, characterized in that, The battery pack also includes a circuit board, on which the plurality of battery modules are stacked.

10. The battery pack according to claim 9, characterized in that, The battery pack also includes a housing and thermally conductive foam. The plurality of battery modules and the circuit board are disposed inside the housing, and the thermally conductive foam is provided in the gaps between the plurality of battery modules and the housing and between the circuit board and the housing.

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