Battery and electrochemical device

Abstract

The application provides a battery pack and an electrochemical device. The battery pack comprises at least two battery cells, each of which comprises a first shell, an electrode assembly, an electrolyte and a heating element, the first shell containing the electrode assembly and the electrolyte, and the heating element being partially disposed in the electrolyte. At least one unidirectional conductive element and a heating loop, the at least two battery cells being connected in series, the heating element and the at least one unidirectional conductive element being disposed on the heating loop, and the heating elements being connected in series and / or in parallel. The heating loop is configured to provide a flow path for a heating current, and the flow direction of the heating current is opposite to that of the self-discharge current of the battery pack. Thus, the battery pack and the electrochemical device provided by the application can reduce the adverse effects of the self-discharge of the battery pack.

Description

Battery packs and electrochemical devices Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a battery pack and an electrochemical device. Background Technology

[0002] Lithium batteries require heating elements to charge and discharge in low-temperature environments. However, the heating elements are placed in the electrolyte of the battery cells, which creates a voltage difference between the heating elements and the electrodes of the cells. This voltage difference also creates a voltage difference between the heating elements in different cells, resulting in current flowing between the heating elements in different cells and increasing the adverse effects of self-discharge of the lithium battery. Summary of the Invention

[0003] In view of the above problems, this application provides a battery pack and an electrochemical device that can reduce the adverse effects of self-discharge of the battery pack.

[0004] In a first aspect, this application provides a battery pack. The battery pack includes: at least two cells, each cell including a first housing, an electrode assembly, an electrolyte, and a heating element. The first housing contains the electrode assembly and the electrolyte, and the heating element is partially disposed in the electrolyte. At least one unidirectional conductive element and a heating circuit are included. The at least two cells are connected in series, and the heating element and at least one unidirectional conductive element are disposed on the heating circuit. The heating elements are connected in series and / or in parallel. The heating circuit is configured to provide a flow path for heating current, the flow direction of which is opposite to the flow direction of the self-discharge current of the battery pack.

[0005] In conjunction with the first aspect, in one possible implementation, the unidirectional conductive element includes at least one of a rectifier, a transistor, a Zener diode, a light-emitting diode, and a MOSFET.

[0006] In conjunction with the first aspect, in one possible implementation, the unidirectional conductive element includes a diode, the heating elements in the heating circuit are connected in series, a diode is disposed between adjacent heating elements, and the conduction direction of the diode is opposite to the direction of the self-discharge current of the battery pack.

[0007] In conjunction with the first aspect, in one possible implementation, the unidirectional conductive element includes a first diode and a second diode, and the heating elements in the heating circuit are connected in parallel. Each heating element includes a first end and a second end, and a first diode is disposed on the connection path between the first ends of adjacent heating elements, and a second diode is disposed on the connection path between the second ends of adjacent heating elements. The conduction direction of the first diode is opposite to the direction of the self-discharge current of the battery pack, and the conduction direction of the second diode is the same as the direction of the self-discharge current of the battery pack.

[0008] In conjunction with the first aspect, in one possible implementation, the unidirectional conductive element includes a third diode, a fourth diode, and a fifth diode. At least two heating elements in the heating circuit are connected in series, and at least two other heating elements in the heating circuit are connected in parallel. A third diode is disposed on the connection path between adjacent heating elements connected in series, a fourth diode is disposed on the connection path between the first ends of adjacent heating elements connected in parallel, and a fifth diode is disposed on the connection path between the second ends of adjacent heating elements connected in parallel. The conduction direction of the third diode is opposite to the direction of the self-discharge current of the battery pack, while the conduction directions of the fourth and fifth diodes are the same as the direction of the self-discharge current of the battery pack.

[0009] In conjunction with the first aspect, in one possible implementation, the heating element is covered with an insulating film, which serves to isolate the heating element from the electrolyte.

[0010] In conjunction with the first aspect, in one possible implementation, the heating element is made of at least one of nickel, aluminum, copper, silver, titanium, stainless steel, or magnesium.

[0011] In conjunction with the first aspect, in one possible implementation, the battery pack also includes an adapter that connects to the battery cells.

[0012] In conjunction with the first aspect, in one possible implementation, the battery pack further includes a second housing, in which at least two cells are stacked longitudinally and / or arranged laterally and housed.

[0013] In conjunction with the first aspect, in one possible implementation, the electrode assembly is a wound structure or a stacked structure.

[0014] Secondly, this application provides an electrochemical device. The electrochemical device includes a battery pack as provided in any possible implementation of the first aspect. Attached Figure Description

[0015] Figure 1 is a schematic diagram of the battery pack.

[0016] Figure 2 is a schematic diagram of a battery pack provided in this application.

[0017] Figure 3 is another schematic diagram of the battery pack provided in this application.

[0018] Figure 4 is another schematic diagram of the battery pack provided in this application.

[0019] Explanation of main component symbols Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings.

[0021] It is understood that the connection relationships described in this application refer to direct or indirect connections. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, A can be directly connected to C, and C can be directly connected to B, thus achieving a connection between A and B through C. It is also understood that the "A connects to B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0022] In the description of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0023] In the description of this application, the words "first," "second," etc., are used only to distinguish different objects and do not limit the quantity or order of execution, nor do they imply that they must be different. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0024] Lithium batteries require heating elements to charge and discharge in low-temperature environments. However, the heating elements are placed in the electrolyte of the battery cells, which creates a voltage difference between the heating elements and the electrode components of the cells. This voltage difference also creates a voltage difference between the heating elements in different cells, resulting in current flowing between the heating elements in different cells and increasing the adverse effects of self-discharge of the lithium battery.

[0025] Specifically, please refer to Figure 1, which is a schematic diagram of the battery pack. The battery pack includes at least two cells, for example, cell 10a and cell 10b.

[0026] In some embodiments, cells 10a and 10b can be connected in series with more cells, meaning the battery pack can include three or more cells. This application does not impose any limitation on the number of cells. Both cells 10a and 10b include an electrolyte 101, a heating element 102, an electrode assembly 103, and a first housing 101a. The electrode assembly 103 and the electrolyte 101 are housed within the first housing 101a. The electrode assembly 103 includes a positive tab 103a and a negative tab 103b. The positive tab 103a of cell 10a is connected to the total positive terminal 104 of the battery pack, the negative tab 103b of cell 10a is connected to the positive tab 103a of cell 10a, and the negative tab 103b of cell 10b is connected to the total negative terminal 105 of the battery pack. Thus, multiple cells are connected in series to form a charging / discharging circuit, which is connected to the total positive terminal 104 and the total negative terminal 105 of the battery pack. When multiple battery cells are charging, the charging current supplied by the external power supply device flows into the charging and discharging circuit from the main positive terminal 104, flows sequentially through the positive tab 103a and negative tab 103b in each battery cell, and then flows out from the main negative terminal 105, thereby realizing the charging operation of the battery pack. When multiple battery cells are discharging, the current output by the battery pack is output from the main positive terminal 104 to the external electrical device, and then flows back to the main negative terminal 105.

[0027] In some embodiments, the positions of the positive and negative tabs of cell 10a and / or cell 10b can be interchanged. The positions of the total positive terminal 104 and the total negative terminal 105 of the battery pack can also be interchanged. After the interchange, the charging current and discharging current of the battery pack are reversed compared to before the interchange.

[0028] Heating element 102 is partially disposed in electrolyte 101, and heating element 102 in cell 10a and heating element 102 in cell 10b are connected in series or in parallel to form a heating circuit. Heating element 102 is used to heat the corresponding cell.

[0029] Since the heating element 102 is partially immersed in the electrolyte 101, if the insulation between the contact surface of the heating element 102 and the electrolyte 101 is poor, the charging and discharging circuit and the heating circuit may be connected through the electrolyte 101, which may cause a short circuit between the charging and discharging circuit and the heating circuit, resulting in a self-discharge current in the heating circuit, thus causing the battery pack to self-discharge.

[0030] Therefore, this application provides a battery pack 10 that can reduce the adverse effects of self-discharge by setting a unidirectional conductive element.

[0031] Specifically, please refer to Figure 2. The battery pack 10 may include at least two cells. Here, we will take the battery pack 10 including cells 10a, 10b and 10c as an example for explanation.

[0032] In some embodiments, the battery pack 10 may include more battery cells, and this application does not impose any limit on the number of battery cells.

[0033] In some embodiments, one or more of the cells 10a, 10b, and 10c can constitute any one of lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, lithium-sulfur batteries, aluminum-ion batteries, aqueous batteries, solid-state batteries, etc. This application does not limit the chemical composition of the cells or the structure of the battery pack 10.

[0034] The battery pack 10 provided in this application also includes at least one unidirectional conductive element 107. The structures of cell 10c, cell 10a, and cell 10b are the same or similar. The structures of cell 10a and cell 10b can be found in the relevant description in Figure 1, and will not be repeated here. The negative electrode tab 103b of cell 10c is connected to the total negative terminal 105. The positive electrode tab 103a of cell 10c is connected to the negative electrode tab 103b of cell 10b, thus cell 10c, cell 10a, and cell 10b are connected in series to form a charging and discharging circuit.

[0035] In some embodiments, the types of cells 10a, 10b, and 10c may be the same or different. For example, any one of cells 10a, 10b, and 10c may include one or more of pouch cells, prismatic cells, or cylindrical cells. This application does not limit the type of cells in the battery pack.

[0036] The heating circuit is connected to an external heating source 106. The heating source 106 provides heating current, causing the heating element 102 to generate heat to heat the battery cell 101.

[0037] In some embodiments, the heating source 106 can be a power supply device that can output electrical energy, such as a constant current source or a constant voltage source, or it can be an energy storage device such as a battery pack or a power module.

[0038] In some embodiments, the heating element can be a metal with good thermal conductivity. For example, the material of the heating element can be at least one of nickel, aluminum, copper, silver, titanium, stainless steel, and magnesium. In this way, the range of materials for the heating element is wide and the compatibility is good.

[0039] Specifically, each heating element 102 has a first end and a second end. The first end of the heating element 102 in cell 10a is connected to the first output terminal P1 of the heating source 106. The second end of the heating element 102 in cell 10a is connected to the first end of the heating element 102 in cell 10b. The second end of the heating element 102 in cell 10b is connected to the first end of the heating element 102 in cell 10c. The second end of the heating element 102 in cell 10c is connected to the second output terminal P2 of the heating source 106. Thus, the three heating elements 102 are connected in series between the first output terminal P1 and the second output terminal P2 of the heating source 106, and the three heating elements 102 and the heating source 106 together form a heating circuit.

[0040] The first output terminal P1 and the second output terminal P2 of the heating source 106 have opposite polarities, and their polarities can be set according to a preset current direction in the heating circuit. The preset current direction is the current direction in the heating circuit when the heating source 106 is not providing heating current.

[0041] In this embodiment, the first output terminal P1 is the positive output terminal, and the second output terminal P2 is the negative output terminal.

[0042] Specifically, since the heating element 102 is disposed in the electrolyte 101 of the corresponding battery cell, a voltage difference will be generated between the heating element 102 and the electrode assembly of the corresponding battery cell, and a voltage difference will also be generated between the heating elements 102 in different battery cells. In some application scenarios, such as when the heating source 106 is not working, the battery pack 10 is in a static state, and the battery pack 10 is neither connected to an external charging device for charging nor to an external electrical device for discharging, the charging and discharging circuit formed by the interconnection of multiple cells lacks both the charging current provided by the external charging device and the discharging current output to the external electrical device. In these situations, the voltage difference between the heating elements 102 in different cells may generate a preset current. This preset current can flow in the charging / discharging circuit and the heating circuit, forming a closed current path. The electronic components or conductive structures located in these circuits, such as the heating element 102, the positive tab 103a, and the negative tab 103b, experience unnecessary losses due to the current flowing through them, resulting in self-discharge losses in the battery pack 10. In this application scenario, the preset current is the self-discharge current of the battery pack 10.

[0043] Furthermore, the preset current direction is related to the positions of the total positive terminal 104 and the total negative terminal 105. Here, we will take the example in Figure 2 where the total positive terminal 104 is connected to the positive tab 103a of the cell 10a and the total negative terminal 105 is connected to the negative tab 103b of the cell 10c. Since the heating element 102, the positive tab 103a, and the negative tab 103b in each cell are all disposed in the electrolyte, there is a voltage difference between the heating element 102 and the positive tab 103a or between the heating element 102 and the negative tab 103b. Since the potential of the total positive terminal 104 is higher than the potential of the total negative terminal 105, the potential of the positive tab 103a in the cell 10a is greater than the potential of the negative tab 103b. Correspondingly, the potential of the heating element 102 in the cell 10a is also higher than the potential of the heating element 102 in the cell 10b and the cell 10c. At this time, the preset current direction is from the second end of the heating element 102 in cell 10a to the first end of the heating element 102 in cell 10b. Therefore, after determining the preset current direction based on the positions of the total positive terminal 104 and the total negative terminal 105, the polarities of the first output terminal P1 and the second output terminal P2 can be specifically set as negative and positive, respectively. Thus, when the heating source 106 is working, that is, when the heating source 106 provides heating current, the direction of the heating current is opposite to the preset current direction. This means that in the scenario where the heating source 106 normally provides heating current, on the one hand, since the heating current provided by the heating source 106 flows through the heating circuit, the potential difference relationship between the different heating elements 102 may change, thereby suppressing the generation of the preset current. On the other hand, the heating current can offset at least a portion of the preset current, thereby reducing unnecessary losses in the battery pack 10 caused by the preset current.

[0044] In some embodiments, if the positions of the positive and negative tabs of each cell in FIG1 are interchanged, the positions of the total positive terminal 104 and the total negative terminal 105 are also interchanged, and the polarities of the first output terminal P1 and the second output terminal P2 are also interchanged accordingly.

[0045] A unidirectional conductive element 107 is disposed on the heating circuit. The unidirectional conductive element 107 is used to control the current direction in the heating circuit to be opposite to the preset current direction of the battery pack 10.

[0046] The unidirectional conductive element 107 can be one or more of a rectifier, transistor, Zener diode, light-emitting diode, and MOSFET. In some embodiments, the unidirectional conductive element 107 may include an electronic component that controls the unidirectional flow of current through it, that is, an electronic component with unidirectional conductivity. Therefore, the unidirectional conductive element has a wide range of material selection, good compatibility, and low cost.

[0047] The following description uses a unidirectional conductive element 107 including a diode as an example. The unidirectional conductive element 107 includes at least one diode, each diode being disposed between the electrical connections of every two heating elements 102, or between the electrical connections of the heating element 102 and the heating source 106. That is, every two heating elements 102 are connected via a diode, or the heating element 102 and the heating source 106 are connected via a diode.

[0048] Among them, diode D1 is electrically connected between the heating element 102 of battery cell 10a and the heating element 102 of battery cell 10b, diode D2 is electrically connected between the heating element 102 of battery cell 10b and the heating element 102 of battery cell 10c, and diode D3 is electrically connected between the heating element 102 of battery cell 10c and the positive terminal of the heating source 106.

[0049] The conduction direction of the diode is opposite to the preset current direction. For example, the anode of diode D1 is connected to the first end of the heating element 102 of cell 10b, the cathode of diode D1 is connected to the second end of the heating element 102 of cell 10a, the anode of diode D2 is connected to the first end of the heating element 102 of cell 10c, the cathode of diode D2 is connected to the second end of the heating element 102 of cell 10b, the anode of diode D3 is connected to the positive output terminal of the heating source 106, and the cathode of diode D3 is connected to the second end of the heating element 102 of cell 10c.

[0050] Thus, the direction of the preset current in the heating circuit is opposite to the conduction direction of the diode, thereby inhibiting the flow of the preset current when it flows through the corresponding diode. When the heating source 106 starts working, the heating current flows through the heating circuit, and the direction of the heating current is the same as the conduction direction of the diode, so the heating current can flow normally in the heating circuit. That is to say, in scenarios such as when the heating source 106 is not working and the battery pack is in a static state, the unidirectional conductive element 107 can inhibit the flow of the preset current in the heating circuit. In scenarios where the heating source 106 is working normally and providing heating current, the unidirectional conductive element 107 can not only inhibit the flow of the preset current in the heating circuit, but also control the normal flow of the heating current in the heating circuit. Therefore, regardless of whether the heating source 106 is working, the unidirectional conductive element 107 can reduce the battery pack loss caused by the self-discharge of the battery pack 10, and does not affect the normal flow of the heating current in the heating circuit when the heating source 106 is working.

[0051] Please refer to Figure 3, which is another schematic diagram of the battery pack 10 provided in this application. The difference between Figure 3 and Figure 2 is that the heating elements 102 in all the cells are connected in parallel to form a heating circuit.

[0052] Specifically, the first end of the heating element 102 in cell 10a is connected to the first output terminal P1 of the heating source 106, the first end of the heating element 102 in cell 10b, and the first end of the heating element 102 in cell 10c. The second end of the heating element 102 in cell 10a is connected to the second output terminal P2 of the heating source 106, the second end of the heating element 102 in cell 10b, and the second end of the heating element 102 in cell 10c. Thus, the three heating elements 102 are connected in parallel between the first output terminal P1 and the second output terminal P2 of the heating source 106, and the three heating elements 102 together with the heating source 106 form a heating circuit. Taking the positive terminal 104 connected to the positive tab 103a of the battery cell 10a and the negative terminal 105 connected to the negative tab 103b of the battery cell 10c as an example, based on the relevant description in Figure 2 regarding the position of the positive terminal 104 and the negative terminal 105 to determine the direction of the preset current, it can be determined that the direction of the preset current is from the first end of the heating element 102 in the battery cell 10a to the first end of the heating element 102 in the battery cell 10b, and from the second end of the heating element 102 in the battery cell 10a to the second end of the heating element 102 in the battery cell 10b.

[0053] Here, taking the unidirectional conductive element 107, including diodes D4-D9, as an example, diodes D4, D6, and D8 are first diodes, electrically connected between the first output terminal P1 of the heating source 106 and the first end of the heating element 102 of the battery cell 10a, between the first output terminal P1 of the heating source 106 and the first end of the heating element 102 of the battery cell 10b, and between the first output terminal P1 of the heating source 106 and the first end of the heating element 102 of the battery cell 10c, respectively. Diodes D5, D7, and D9 are second diodes, electrically connected between the second output terminal P2 of the heating source 106 and the second end of the heating element 102 of the battery cell 10a, between the second output terminal P2 of the heating source 106 and the second end of the heating element 102 of the battery cell 10b, and between the second output terminal P2 of the heating source 106 and the second end of the heating element 102 of the battery cell 10c, respectively. The conduction direction of the first diodes is opposite to the preset current direction, and the conduction direction of the second diodes is the same as the preset current direction. That is, the anodes of diodes D4, D6, and D8 are all electrically connected to the first output terminal P1 of the heating source 106, the cathodes of diodes D5, D7, and D9 are respectively electrically connected to the first end of the heating element 102 of battery cell 10a, the first end of the heating element 102 of battery cell 10b, and the first end of the heating element 102 of battery cell 10c, and the cathodes of diodes D5, D7, and D9 are all electrically connected to the second output terminal P2 of the heating source 106, and the anodes of diodes D5, D7, and D9 are respectively electrically connected to the second end of the heating element 102 of battery cell 10a, the second end of the heating element 102 of battery cell 10b, and the second end of the heating element 102 of battery cell 10c.

[0054] Thus, since the conduction direction of the first diode is opposite to the direction of the preset current, and the conduction direction of the second diode is the same as the direction of the preset current, the first and second diodes cooperate to suppress the flow of the preset current in the heating circuit when the heating source 106 is not working and the battery pack 10 is in a static state. However, when the heating source 106 is working normally and providing heating current, while the flow of the preset current in the heating circuit is suppressed, the heating current can still flow normally in the heating circuit. Therefore, regardless of whether the heating source 106 is working, the combination of the first and second diodes can reduce battery pack losses caused by self-discharge of the battery pack 10, without affecting the normal flow of heating current in the heating circuit when the heating source is working.

[0055] Please refer to Figure 4, which is another schematic diagram of the battery pack 10 provided in this application. In this embodiment, the battery pack 10 includes six cells, namely cells 10a-10f. The heating elements 102 in all cells are connected in series to form a heating circuit.

[0056] Specifically, the connection method of the heating element 102 in cells 10a-10c is the same as that in Figure 1, which is a series connection, and will not be described again here. The connection method of the heating element 102 in cells 10d-10e is the same as that in Figure 2, which is a parallel connection, and will not be described again here.

[0057] The first end of the heating element 102 of cell 10a is connected to the first output terminal P1 of the heating source 106. The second end of the heating element 102 of cell 10a is connected to the first end of the heating element 102 of cell 10b through diode D10. The second end of the heating element 102 of cell 10b is connected to the first end of the heating element 102 of cell 10c through diode D11. The second end of the heating element 102 of cell 10c is connected to the first end of the heating element 102 of cell 10d through diodes D12 and D13.

[0058] In this configuration, diodes D10, D11, and D12 form the third diode. The conduction direction of the third diode is opposite to the preset current direction. For example, the anode of diode D10 is electrically connected to the first end of the heating element 102 of cell 10b, the cathode of diode D10 is electrically connected to the second end of the heating element 102 of cell 10a, the anode of diode D11 is electrically connected to the first end of the heating element 102 of cell 10c, the cathode of diode D11 is electrically connected to the second end of the heating element 102 of cell 10b, and the anode of diode D12 is electrically connected to the first end of cell 10d via diode D13. Thus, the heating elements 102 in cells 10a-10c form a series connection.

[0059] The first ends of the heating elements 102 in cells 10d, 10e, and 10f are connected to the second output terminal P2 of the heating source 106 via diodes D13, D15, and D17, respectively. The second ends of the heating elements 102 in cells 10d, 10e, and 10f are connected to the first output terminal P1 of the heating source 106 via diodes D14, D16, and D18, respectively. Thus, the heating elements 102 in cells 10d, 10e, and 10f are connected in parallel. In other words, the heating elements 102 in cells 10a-10f are connected in a mixed configuration to form a heating circuit. Diodes D13, D15, and D17 are the fourth diodes. The conduction direction of the fourth diodes is the same as the preset current direction. Diodes D14, D16, and D18 are the fifth diodes. The conduction direction of the fifth diodes is the same as the preset current direction. For example, the anode of diode D13 is electrically connected to the anode of diode D12 and the second output terminal P2 of heating source 106, and the cathode of diode D13 is electrically connected to the first end of heating element 102 of cell 10d. The anode of diode D14 is electrically connected to the second end of heating element 102 of cell 10d and the second output terminal P2 of heating source 106, and the cathode of diode D14 is electrically connected to the first output terminal P1 of heating source 106. The conduction directions of diodes D15 and D17 are the same as those of diode D13, and the conduction directions of diodes D16 and D18 are the same as those of diode D14.

[0060] Thus, since the conduction direction of the third diode is opposite to the direction of the preset current, while the conduction directions of the fourth and fifth diodes are the same as the direction of the preset current, the third, fourth, and fifth diodes cooperate to suppress the flow of the preset current in the heating circuit when the heating source 106 is not working and the battery pack 10 is in a static state. However, when the heating source 106 is working normally and providing heating current, while the flow of the preset current in the heating circuit is suppressed, the heating current can still flow normally in the heating circuit. Therefore, regardless of whether the heating source 106 is working, the cooperation of the third, fourth, and fifth diodes can reduce battery pack losses caused by self-discharge of the battery pack 10, and does not affect the normal flow of heating current in the heating circuit when the heating source is working.

[0061] In some embodiments, the heating element 102 is further covered with an insulating film, which serves to isolate the heating element 102 from the electrolyte 101. Thus, the insulating film enhances the isolation between the heating element 102 and the electrolyte 101, reducing the risk of short circuits. This reduces the likelihood of electrical connections forming between the electrode assembly of the battery cell and the heating element through the electrolyte, lowers the preset current, and consequently reduces the self-discharge rate of the battery pack 10, mitigating battery pack 10 losses.

[0062] In some embodiments, the heating element 102 may not need to be covered with an insulating film. Even if the lack of an insulating film on the heating element 102 results in poor insulation between the heating element 102 and the electrolyte 101, the flow of the preset current in the heating circuit can be suppressed by providing the unidirectional conductive element 107. Furthermore, the manufacturing cost of the battery pack 10 provided in this application can be reduced, the manufacturing process can be simplified, the structure can be simplified, the volume can be reduced, and the risk of a large preset current due to insufficient insulation film coverage or sealing, thereby increasing the self-discharge level of the battery pack 10, can be reduced.

[0063] In some embodiments, the battery pack 10 further includes an adapter for electrically connecting the electrode assemblies between every two cells. For example, the negative tab 103b of cell 10a, the adapter, and the positive tab 103a of cell 10b are welded together, such that the negative tab 103b of cell 10a is electrically connected to the positive tab 103a of cell 10b via the adapter. Therefore, the adapter can enhance the stability of the electrical connection between multiple cells and is easy to implement.

[0064] In some embodiments, the battery pack 10 further includes a second housing in which all battery cells are stacked or wound and housed. Thus, multiple battery cells can be arranged in the second housing in various positional relationships, such as vertical stacking or lateral arrangement.

[0065] In some embodiments, the electrode assembly of the cell in the battery pack 10 can be a wound structure or a stacked structure. Specifically, the electrode assembly can be a wound electrode assembly or a stacked electrode assembly. The cell in the battery pack 10 can also be a combination of a wound structure and a stacked structure.

[0066] The following describes the beneficial effects of the battery pack 10 provided in this application, based on experimental data. Please refer to Table 1, which shows the self-discharge rate test results of the battery pack.

[0067] In this embodiment of the application, the battery cell in the battery pack 10 is a soft-pack wound cell with a capacity of 4Ah. The active material of the positive electrode is NCM811, which accounts for 96% of the mass, and the compaction density of the positive electrode is 3.4g / cc. The active material of the positive electrode is graphite, and the compaction density of the negative electrode is 1.6g / cc.

[0068] Table 1. Self-discharge rate test results of the battery pack

[0069] As shown in Table 1, referring to the test results of Example 1, Example 4, and Comparative Example 1, it can be seen that in the heating circuit formed by the series connection of heating elements, the self-discharge rate of the battery pack will decrease after the unidirectional conductive element is set. Among them, the self-discharge rate of the battery pack when the unidirectional conductive element is a MOSFET is lower than the self-discharge rate of the battery pack when the unidirectional conductive element is a diode.

[0070] Referring to the test results of Example 5 and Comparative Example 2, it can be seen that in the heating circuit formed by parallel heating elements, the self-discharge rate of the battery pack decreases after a unidirectional conductive element is installed.

[0071] Referring to the test results of Examples 1-3 and Comparative Example 1, it can be seen that in the heating circuit formed by the series connection of heating elements, after setting a unidirectional conductive element, the self-discharge rate of the battery pack is similar for different heating element materials, that is, the self-discharge rate of the battery pack is not closely related to the heating element material.

[0072] Therefore, the battery pack 10 provided in this application, by setting a unidirectional conductive element 107 in the heating circuit formed by the heating element 102, can prevent the self-discharge current from flowing in the heating circuit of the battery pack 10 and allow the heating current provided by the heating source 106 to flow normally, thereby reducing the self-discharge rate of the battery pack 10, reducing the adverse effects of self-discharge of the battery pack 10, and improving the service life of the battery pack 10.

[0073] This application also provides an electrochemical device, which includes the above-mentioned battery pack 10.

[0074] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A battery pack, characterized in that, include: At least two battery cells, each battery cell including a first housing, an electrode assembly, an electrolyte, and a heating element, the first housing accommodating the electrode assembly and the electrolyte, and the heating element partially disposed in the electrolyte; At least one unidirectional conductive element and a heating circuit, wherein the at least two battery cells are connected in series, the heating element and the at least one unidirectional conductive element are disposed on the heating circuit, and the heating elements are connected in series and / or in parallel. The heating circuit is configured to provide a path for heating current, the direction of which is opposite to the direction of the self-discharge current of the battery pack.

2. The battery pack as described in claim 1, characterized in that, The unidirectional conductive component includes at least one of a rectifier, transistor, Zener diode, light-emitting diode, and MOSFET.

3. The battery pack as described in claim 1, characterized in that, The unidirectional conductive element includes a diode. The heating elements in the heating circuit are connected in series, and the diode is disposed between adjacent heating elements. The conduction direction of the diode is opposite to the direction of the self-discharge current of the battery pack.

4. The battery pack according to any one of claims 1 to 3, characterized in that, The unidirectional conductive element includes a first diode and a second diode, and the heating elements in the heating circuit are connected in parallel. Each of the heating elements includes a first end and a second end. The first diode is provided on the connection path between the first ends of adjacent heating elements, and the second diode is provided on the connection path between the second ends of adjacent heating elements. The first diode is in the opposite direction to the self-discharge current of the battery pack, while the second diode is in the same direction as the self-discharge current of the battery pack.

5. The battery pack according to any one of claims 1 to 3, characterized in that, The unidirectional conductive element includes a third diode, a fourth diode, and a fifth diode. At least two heating elements in the heating circuit are connected in series, and at least two other heating elements in the heating circuit are connected in parallel. The third diode is provided in the connection path between adjacent heating elements connected in series, the fourth diode is provided in the connection path between the first ends of adjacent heating elements connected in parallel, and the fifth diode is provided in the connection path between the second ends of adjacent heating elements connected in parallel. The conduction direction of the third diode is opposite to the direction of the self-discharge current of the battery pack, while the conduction directions of the fourth and fifth diodes are the same as the direction of the self-discharge current of the battery pack.

6. The battery pack according to any one of claims 1 to 5, characterized in that, The heating element is covered with an insulating film, which is used to isolate the heating element from the electrolyte.

7. The battery pack according to any one of claims 1 to 6, characterized in that, The heating element is made of at least one of nickel, aluminum, copper, silver, titanium, stainless steel, or magnesium.

8. The battery pack according to any one of claims 1 to 7, characterized in that, The battery pack also includes an adapter that connects to the battery cells.

9. The battery pack according to any one of claims 1 to 8, characterized in that, The battery pack also includes a second housing, in which the at least two of the battery cells are stacked longitudinally and / or arranged laterally and housed within the second housing.

10. The battery pack according to any one of claims 1 to 9, characterized in that, The electrode assembly has a wound structure or a stacked structure.

11. An electrochemical device, characterized in that, Includes the battery pack as described in any one of claims 1 to 10.

Images