Secondary battery and electronic device

Abstract

The invention relates to a secondary battery and electronic equipment, the secondary battery comprises a first pole piece and a second pole piece which are opposite in polarity, the first pole piece comprises a first current collector and a first active layer arranged on the surface of the first current collector, the first current collector comprises a first polymer layer, a first metal layer and a second metal layer, a first metal layer and a second metal layer are arranged on the two opposite surfaces of the first polymer layer respectively. A first tab is arranged on the surface, deviating from the first polymer layer, of the first metal layer and comprises a first connecting part electrically connected with the first metal layer, a first heat absorption piece is arranged on the surface, deviating from the first metal layer, of the first tab, and the projection of the first heat absorption piece is at least partially overlapped with the first connecting part in the thickness direction of the first tab. According to the secondary battery and the electronic equipment, the thermal runaway risk of the secondary battery can be improved.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and particularly to a secondary battery and an electronic device. Background Art

[0002] As the power source of an electronic device, a secondary battery is crucial for ensuring the normal use of the electronic device. During the high-current charge and discharge process of a secondary battery, there is a risk of thermal runaway. A composite metal current collector (MPF) uses a metal-polymer-metal structure, which can reduce the weight of the battery. Moreover, the metal layer is relatively thin, which can reduce the burrs during the mechanical damage of the electrode assembly, reduce the probability of short circuit, and enhance the safety of the secondary battery, showing broad prospects in the field of secondary battery safety. However, the metal layer of the composite current collector is relatively thin. After the current collector and the tab are electrically connected by ultrasonic welding or riveting, the contact area between the metal layer on the current collector and the tab is small, resulting in an increase in the electrical connection resistance. In this case, during the high-current charge and discharge process, the joule heat generated at the connection between the metal layer and the tab increases significantly, leading to an increase in the temperature of the secondary battery and further triggering the risk of thermal runaway. Summary of the Invention

[0003] The purpose of this application is to provide a secondary battery and an electronic device, aiming to improve the risk of thermal runaway of the secondary battery.

[0004] According to the first aspect of this application, a secondary battery is provided, which includes a first electrode sheet and a second electrode sheet with opposite polarities. The first electrode sheet includes a first current collector and a first active layer provided on the surface of the first current collector. The first current collector includes a first polymer layer, a first metal layer, and a second metal layer. The first metal layer and the second metal layer are respectively provided on the opposite two surfaces of the first polymer layer. A first tab is provided on the surface of the first metal layer facing away from the first polymer layer. The first tab includes a first connection portion electrically connected to the first metal layer. A first heat absorber is provided on the surface of the first tab facing away from the first metal layer. Along the thickness direction of the first tab, the projection of the first heat absorber overlaps at least a part of the first connection portion.

[0005] In the above technical solution, by providing that the first current collector includes a first polymer layer, a first metal layer, and a second metal layer, with the first metal layer and the second metal layer respectively disposed on opposite surfaces of the first polymer layer, the safety of the secondary battery can be enhanced. By providing that a first tab is disposed on the surface of the first metal layer facing away from the first polymer layer, and the first tab includes a first connecting portion electrically connected to the first metal layer, the current of the first metal layer can be transmitted to the first tab. By providing that a first heat-absorbing member is disposed on the surface of the first tab facing away from the first metal layer, and in the thickness direction of the first tab, the projection of the first heat-absorbing member overlaps at least partially with the first connecting portion, the first heat-absorbing member can absorb the heat generated when the first tab has an overcurrent, thereby reducing the rapid transmission of heat, reducing the transfer of heat from the first tab to the second electrode plate, and reducing the temperature accumulation of the first tab, thus improving the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery.

[0006] In some preferred embodiments, in the thickness direction of the first tab, the first heat-absorbing member covers the first connecting portion, and the first heat-absorbing member can better absorb the heat of the first connecting portion.

[0007] In some preferred embodiments, in the thickness direction of the first tab, the first heat-absorbing member covers the first tab, and the first heat-absorbing member can better absorb the heat of the first tab.

[0008] In some preferred embodiments, the surface of the first metal layer facing away from the first polymer layer includes a connected coating area and an empty foil area. The coating area is provided with a first active layer, and the empty foil area is provided with a first tab, which can reduce the possibility of the first active layer overlapping with the first tab in the thickness direction of the first current collector, thereby reducing the thickness of the secondary battery and improving the energy density of the secondary battery.

[0009] In some preferred embodiments, the first heat-absorbing member includes graphite, and the specific heat capacity of the first heat-absorbing member is ≥1300 J / (kg·K). Graphite has good heat capacity, can quickly absorb the heat generated when the first tab has an overcurrent and the temperature does not rise significantly. In addition, graphite also has good thermal conductivity and can quickly disperse the heat of the first tab, reducing the possibility of temperature accumulation of the first tab. The larger the specific heat capacity of the first heat-absorbing member, the stronger the ability of the first heat-absorbing member to absorb the heat of the first tab, and the smaller the temperature rise, and the better the effect of improving the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery. When the first heat-absorbing member includes graphite and the specific heat capacity of the first heat-absorbing member is less than 1300 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious. By providing that the specific heat capacity of the first heat-absorbing member is ≥1300 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab can be improved, thereby improving the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery.

[0010] In some preferred embodiments, the first heat-absorbing member includes a phase change material. The phase change material can absorb and release heat through phase change. The phase change material can absorb heat and turn into a liquid when the temperature of the first tab rises, and release heat and return to a solid state when the temperature of the secondary battery drops. During this process, the temperature fluctuation is not obvious, which can stabilize the operating temperature of the first tab and the secondary battery, and can improve the problem of thermal runaway of the secondary battery.

[0011] In some preferred embodiments, the first heat-absorbing member includes paraffin wax, and the specific heat capacity of the first heat-absorbing member ≥ 3000 J / (kg·K). The latent heat of phase change of paraffin wax has a relatively large change range, and it can absorb more heat. When the first heat-absorbing member includes paraffin wax, when the specific heat capacity of the first heat-absorbing member is less than 3000 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious. By setting the specific heat capacity of the first heat-absorbing member ≥ 3000 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab can be improved, and thus the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery can be improved.

[0012] In some preferred embodiments, the first heat-absorbing member is a metal foil. The metal foil has good thermal conductivity and can quickly conduct away the heat from the high-temperature area of the first tab, which can improve the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery.

[0013] In some preferred embodiments, the first heat-absorbing member is an aluminum foil. Aluminum has better thermal conductivity than other metals, which can further improve the performance of the first heat-absorbing member in conducting away the heat from the high-temperature area of the first tab.

[0014] In some preferred embodiments, the thickness of the first heat-absorbing member is 10 μm to 50 μm. The greater the thickness of the first heat-absorbing member, the stronger the ability of the first heat-absorbing member to absorb the heat of the first tab, and the smaller the temperature rise, and the better the effect of improving the thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery. When the thickness of the first heat-absorbing member is less than 10 μm, the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious. By setting the thickness of the first heat-absorbing member ≥ 10 μm, the ability of the first heat-absorbing member to absorb the heat of the first tab can be improved, and thus the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery can be improved. When the thickness of the first heat-absorbing member is greater than 50 μm, continuing to increase the thickness of the first heat-absorbing member, the improvement of the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious, and it is easy to consume more energy density of the secondary battery. By setting the thickness of the first heat-absorbing member ≤ 50 μm, the energy density of the secondary battery can be improved.

[0015] In some preferred embodiments, the first connecting portion, the first metal layer, and the second metal layer are connected by riveting or roll welding, so that the first tab, the first metal layer, and the second metal layer can be electrically connected and conduct, which can improve the energy utilization rate of the first electrode sheet.

[0016] In some preferred embodiments, a second tab is provided on the surface of the second metal layer facing away from the first polymer layer. The second tab is connected to the first tab. The second tab includes a second connecting portion electrically connected to the second metal layer, and the current of the second metal layer can be sequentially transmitted to the second tab and the first tab. A second heat absorbing member is provided on the surface of the second tab facing away from the second metal layer. Along the thickness direction of the second tab, the projection of the second heat absorbing member overlaps at least a part of the second connecting portion. The second heat absorbing member can absorb the heat generated when the second tab has current flowing through it, thereby reducing the rapid transmission of heat, reducing the transfer of heat from the second tab to the second electrode sheet, and reducing the temperature accumulation of the second tab, thus improving the problem of thermal runaway caused by overheating of the second tab during high-current discharge of the secondary battery.

[0017] In some preferred embodiments, the second electrode sheet includes a second current collector and a second active layer provided on the surface of the second current collector. The second current collector includes a second polymer layer, a third metal layer, and a fourth metal layer. The third metal layer and the fourth metal layer are respectively provided on the opposite two surfaces of the second polymer layer, which can enhance the safety of the secondary battery. A third tab is provided on the surface of the third metal layer facing away from the second polymer layer. The third tab includes a third connecting portion electrically connected to the third metal layer, and the current of the third metal layer can be transmitted to the third tab. A third heat absorbing member is provided on the surface of the third tab facing away from the third metal layer. Along the thickness direction of the third tab, the projection of the third heat absorbing member overlaps at least a part of the third connecting portion. The third heat absorbing member can absorb the heat generated when the third tab has current flowing through it, thereby reducing the rapid transmission of heat, reducing the transfer of heat from the third tab to the first electrode sheet, and reducing the temperature accumulation of the third tab, thus improving the problem of thermal runaway caused by overheating of the third tab during high-current discharge of the secondary battery.

[0018] In a second aspect, the present application also proposes an electronic device, including the secondary battery according to any one of the embodiments in the first aspect above.

[0019] Additional aspects and advantages of the embodiments of the present application will be described, shown, or elucidated in part in the subsequent description, or through the implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One or more embodiments are illustrated by corresponding drawings. These illustrative descriptions do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated, and the dimensions in the drawings do not constitute a proportional limitation.

[0021] Figure 1 Structural schematic diagram of a secondary battery according to some embodiments of the present application;

[0022] Figure 2 Structural schematic diagram of an electrode assembly according to some embodiments of the present application;

[0023] Figure 3 Structural schematic diagram of an electrode assembly and a first heat absorber according to some embodiments of the present application;

[0024] Figure 4 Structural schematic diagram of an electrode assembly, a first heat absorber and a second heat absorber according to some embodiments of the present application;

[0025] Figure 5 Structural schematic diagram of an electrode assembly, a first heat absorber and a third heat absorber according to some embodiments of the present application.

[0026] Description of reference numerals:

[0027] 100, secondary battery; 10, housing; 20, electrode assembly; 21, first electrode tab; 211, first current collector; 2111, first polymer layer; 2112, first metal layer; 211a, coated area; 211b, empty foil area; 2113, second metal layer; 212, first active layer; 22, second electrode tab; 221, second current collector; 2211, second polymer layer; 2212, third metal layer; 2213, fourth metal layer; 222, second active layer; 23, separator; 241, first tab; 2411, first connection portion; 242, second tab; 2421, second connection portion; 243, third tab; 2431, third connection portion; 251, first heat absorber; 252, second heat absorber; 253, third heat absorber; X, first direction. Detailed Description of the Invention

[0028] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application.

[0029] Reference to "embodiment" in the present application means that a specific feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0030] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0031] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0032] The term "vertical" is used to describe the ideal state between two components. In the actual production or use state, there may be a state approximately vertical between two components. For example, in combination with numerical descriptions, vertical can refer to the included angle range between two straight lines being between 90±10°, vertical can also refer to the dihedral angle range between two planes being between 90±10°, and vertical can also refer to the included angle range between a straight line and a plane being between 90±10°. The two components described as "vertical" may not be absolute straight lines or planes, and may also be approximately straight lines or planes. From a macroscopic perspective, as long as the overall extension direction is a straight line or a plane, the components can be considered "straight lines" or "planes".

[0033] The technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0034] In a first aspect, an embodiment of the present application provides a secondary battery 100. Please refer to Figure 1 , the secondary battery 100 includes a housing 10 and an electrode assembly 20. The housing 10 can accommodate the electrode assembly 20 and an electrolyte (not shown in the figure), and the electrolyte infiltrates the electrode assembly 20 within the housing 10.

[0035] Regarding the above electrode assembly 20, please refer to Figure 2 , Figure 2The winding structure of the electrode assembly 20 is shown. The electrode assembly 20 includes a first electrode tab 21, a separator 23, and a second electrode tab 22. The polarities of the first electrode tab 21 and the second electrode tab 22 are opposite. A separator 23 is disposed between the adjacent second electrode tab 22 and the first electrode tab 21. The first electrode tab 21, the separator 23, and the second electrode tab 22 are stacked and wound. Exemplarily, along the thickness direction of the first electrode tab 21 and / or the second electrode tab 22, after the first electrode tab 21, the separator 23, and the second electrode tab 22 are stacked in sequence, they are wound to form the wound electrode assembly 20. In the embodiments of the present application, the electrode assembly 20 is taken as an example of a winding structure for illustration. In some other embodiments, the electrode assembly 20 may also be a stacked structure. For example, along the thickness direction of the first electrode tab 21 and / or the second electrode tab 22, the first electrode tab 21, the separator 23, and the second electrode tab 22 are stacked in sequence to form a stacked electrode assembly 20.

[0036] In some embodiments, please refer to Figure 3 , the first electrode tab 21 includes a first current collector 211 and a first active layer 212. The first active layer 212 is disposed on the surface of the first current collector 211. In some embodiments, the first electrode tab 21 may be a positive electrode tab. In some other embodiments, the first electrode tab 21 may be a negative electrode tab.

[0037] In some embodiments, the first current collector 211 includes a first metal layer 2112, a first polymer layer 2111, and a second metal layer 2113. Along the thickness direction (the first direction X) of the first current collector 211, the first metal layer 2112 and the second metal layer 2113 are respectively disposed on the opposite two surfaces of the first polymer layer 2111. The first polymer layer 2111 serves as the main mechanical support layer of the first current collector 211 and may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), polyimide, polytetrafluoroethylene, and polyester. The first metal layer 2112 may include at least one of aluminum, copper, nickel, titanium, silver, and zirconium. The second metal layer 2113 may include at least one of aluminum, copper, nickel, titanium, silver, and zirconium. The first current collector 211 can reduce the thickness of the metal layer by using the first polymer layer 2111 as the main mechanical support layer, thereby reducing the metal burrs generated when the secondary battery 100 is mechanically damaged, and reducing the mass of the first current collector 211, thereby improving the mass energy density of the secondary battery 100. In some other embodiments, the first current collector 211 may be a single-layer metal foil, and the single-layer metal foil may include at least one of aluminum, copper, nickel, titanium, and silver.

[0038] In some embodiments, the first metal layer 2112 and the second metal layer 2113 are respectively disposed on opposite two surfaces of the first polymer layer 2111 by electroplating. In some embodiments, the first metal layer 2112 and the second metal layer 2113 are respectively disposed on opposite two surfaces of the first polymer layer 2111 by evaporation coating.

[0039] In some embodiments, a first active layer 212 is disposed on the surface of the first metal layer 2112 facing away from the first polymer layer 2111. In some embodiments, a first active layer 212 is disposed on the surface of the second metal layer 2113 facing away from the first polymer layer 2111, which can reduce the number of layers of the first electrode sheet 21 in the secondary battery 100, thereby improving the energy density.

[0040] In some embodiments, the first active layer 212 is infiltrated by the above-mentioned electrolyte within the housing 10 to undergo an electrochemical reaction. The first active layer 212 includes a positive electrode active material, a conductive agent, a binder, etc. The above-mentioned materials are mixed and stirred evenly and coated on the surface of the first metal layer 2112 facing away from the first polymer layer 2111, thereby obtaining the first active layer 212. The positive electrode active material may include at least one of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt aluminate, lithium manganese oxide, and lithium manganese iron phosphate.

[0041] In some embodiments, a first tab 241 is disposed on the surface of the first metal layer 2112 facing away from the first polymer layer 2111. The first tab 241 includes a first connection portion 2411 electrically connected to the first metal layer 2112, and the current of the first metal layer 2112 can be transmitted to the first tab 241. Since the first metal layer 2112 is relatively thin and the contact area between the first connection portion 2411 and the first tab 241 is small, the electrical connection resistance between the first connection portion 2411 and the first tab 241 increases. In this case, during the large current charge and discharge process, the joule heat generated at the connection between the first connection portion 2411 and the first tab 241 increases significantly, resulting in an increase in the temperature of the secondary battery 100, and further leading to a risk of thermal runaway.

[0042] To improve the above problems, in the embodiments of the present application, a first heat-absorbing member 251 is disposed on the surface of the first tab 241 facing away from the first metal layer 2112. Along the thickness direction of the first tab 241, the projection of the first heat-absorbing member 251 overlaps at least a part of the first connection portion 2411. The first heat-absorbing member 251 can absorb the heat generated when the first tab 241 has an overcurrent, and further can reduce the rapid transmission of heat, thereby reducing the heat transfer of the first tab 241 to the second electrode sheet 22, and reducing the temperature accumulation of the first tab 241, thereby improving the problem that the first tab 241 overheats and causes thermal runaway in the secondary battery 100 under large current discharge.

[0043] In some embodiments, along the thickness direction of the first tab 241, the first heat-absorbing member 251 covers the first connection portion 2411, and the first heat-absorbing member 251 can better absorb the heat of the first connection portion 2411.

[0044] In some embodiments, along the thickness direction of the first tab 241, the first heat-absorbing member 251 covers the first tab 241, and the first heat-absorbing member 251 can better absorb the heat of the first tab 241.

[0045] In some embodiments, the surface of the first metal layer 2112 facing away from the first polymer layer 2111 includes a connected coating region 211a and a bare foil region 211b. The first active layer 212 is provided in the coating region 211a, and the first tab 241 is provided in the bare foil region 211b. This can reduce the possibility of the first active layer 212 and the first tab 241 overlapping in the thickness direction of the first current collector 211, thereby reducing the thickness of the secondary battery 100 and improving the energy density of the secondary battery 100.

[0046] In some embodiments, the first heat-absorbing member 251 includes graphite, and the specific heat capacity of the first heat-absorbing member 251 ≥ 1300 J / (kg·K). Graphite has good heat capacity and can quickly absorb the heat generated when the first tab 241 is overcurrent and the temperature does not rise significantly. In addition, graphite also has good thermal conductivity and can quickly disperse the heat of the first tab 241, reducing the possibility of temperature accumulation in the first tab 241. The larger the specific heat capacity of the first heat-absorbing member 251, the stronger the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241, and the smaller the temperature rise, the better the effect of improving the thermal runaway of the first tab 241 under high-current discharge of the secondary battery 100. When the first heat-absorbing member 251 includes graphite and the specific heat capacity of the first heat-absorbing member 251 is less than 1300 J / (kg·K), the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241 is not obvious. By setting the specific heat capacity of the first heat-absorbing member 251 ≥ 1300 J / (kg·K), the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241 can be improved, and thus the problem of thermal runaway of the first tab 241 under high-current discharge of the secondary battery 100 can be improved.

[0047] In some embodiments, the first heat-absorbing member 251 includes a phase change material. The phase change material can absorb and release heat through phase change. The phase change material can absorb heat and turn into a liquid when the temperature of the first tab 241 rises, and release heat and return to a solid state when the temperature of the secondary battery 100 drops. During this process, the temperature fluctuation is not obvious, which can stabilize the operating temperature of the first tab 241 and the secondary battery 100, and improve the problem of thermal runaway of the secondary battery 100.

[0048] In some embodiments, the first heat-absorbing member 251 includes paraffin wax, and the specific heat capacity of the first heat-absorbing member 251 is ≥ 3000 J / (kg·K). The phase change latent heat of paraffin wax has a relatively large variation range, and it can absorb more heat. When the first heat-absorbing member 251 includes paraffin wax, when the specific heat capacity of the first heat-absorbing member 251 is less than 3000 J / (kg·K), the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241 is not obvious. By setting the specific heat capacity of the first heat-absorbing member 251 to be ≥ 3000 J / (kg·K), the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241 can be improved, and thus the problem of thermal runaway caused by overheating of the first tab 241 during high-current discharge of the secondary battery 100 can be improved.

[0049] In some embodiments, the first heat-absorbing member 251 is a metal foil. The metal foil has good thermal conductivity and can quickly conduct away the heat of the high-temperature area of the first tab 241, and can improve the problem of thermal runaway caused by overheating of the first tab 241 during high-current discharge of the secondary battery 100.

[0050] In some embodiments, the first heat-absorbing member 251 is an aluminum foil. Aluminum has better thermal conductivity than other metals, and can further improve the performance of the first heat-absorbing member 251 in conducting away the heat of the high-temperature area of the first tab 241.

[0051] In some embodiments, the thickness H of the first heat-absorbing member 251 is 10 μm to 50 μm. The greater the thickness of the first heat-absorbing member 251, the stronger the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241, and the smaller the temperature rise, and the better the effect of improving the problem of thermal runaway caused by overheating of the first tab 241 during high-current discharge of the secondary battery 100. When the thickness of the first heat-absorbing member 251 is less than 10 μm, the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241 is not obvious. By setting the thickness of the first heat-absorbing member 251 to be ≥ 10 μm, the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241 can be improved, and thus the problem of thermal runaway caused by overheating of the first tab 241 during high-current discharge of the secondary battery 100 can be improved. When the thickness of the first heat-absorbing member 251 is greater than 50 μm, continuing to increase the thickness of the first heat-absorbing member 251, the improvement in the ability of the first heat-absorbing member 251 to absorb the heat of the first tab 241 is not obvious, and it is easy to consume more energy density of the secondary battery 100. By setting the thickness of the first heat-absorbing member 251 to be ≤ 50 μm, the energy density of the secondary battery 100 can be improved.

[0052] In some embodiments, the first connecting portion 2411, the first metal layer 2112, and the second metal layer 2113 are connected by riveting or roll welding, so that the first tab 241, the first metal layer 2112, and the second metal layer 2113 can be electrically connected and conducted, and the energy utilization rate of the first electrode plate 21 can be improved.

[0053] In some embodiments, please refer to Figure 4 , on the surface of the second metal layer 2113 facing away from the first polymer layer 2111, a second tab 242 is provided. The second tab 242 is connected to the first tab 241. The second tab 242 includes a second connecting portion 2421 electrically connected to the second metal layer 2113. The current of the second metal layer 2113 can be sequentially transmitted to the second tab 242 and the first tab 241. On the surface of the second tab 242 facing away from the second metal layer 2113, a second heat absorber 252 is provided. Along the thickness direction of the second tab 242, the projection of the second heat absorber 252 overlaps at least a part of the second connecting portion 2421. The second heat absorber 252 can absorb the heat generated when the second tab 242 has an overcurrent, thereby reducing the rapid transmission of heat, reducing the transfer of heat from the second tab 242 to the second electrode plate 22, and reducing the temperature accumulation of the second tab 242, thereby improving the problem of thermal runaway caused by overheating of the second tab 242 during high-current discharge of the secondary battery 100.

[0054] In some embodiments, please refer to Figure 5 , the second electrode plate 22 includes a second current collector 221 and a second active layer 222 provided on the surface of the second current collector 221. The second current collector 221 includes a second polymer layer 2211, a third metal layer 2212, and a fourth metal layer 2213. The third metal layer 2212 and the fourth metal layer 2213 are respectively provided on the opposite two surfaces of the second polymer layer 2211, which can reduce the thickness of the metal layer of the second current collector 221, improve the energy density of the secondary battery 100, and enhance the safety of the secondary battery 100. On the surface of the third metal layer 2212 facing away from the second polymer layer 2211, a third tab 243 is provided. The third tab 243 includes a third connecting portion 2431 electrically connected to the third metal layer 2212. The current of the third metal layer 2212 can be transmitted to the third tab 243. On the surface of the third tab 243 facing away from the third metal layer 2212, a third heat absorber 253 is provided. Along the thickness direction of the third tab 243, the projection of the third heat absorber 253 overlaps at least a part of the third connecting portion 2431. The third heat absorber 253 can absorb the heat generated when the third tab 243 has an overcurrent, thereby reducing the rapid transmission of heat, reducing the transfer of heat from the third tab 243 to the first electrode plate 21, and reducing the temperature accumulation of the third tab 243, thereby improving the problem of thermal runaway caused by overheating of the third tab 243 during high-current discharge of the secondary battery 100.

[0055] In some embodiments, the second polymer layer 2211 may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The third metal layer 2212 may include at least one of aluminum, copper, nickel, titanium, and silver. The second current collector 221 uses the second polymer layer 2211 as the main mechanical support layer, which can thin the metal layer, thereby reducing the metal burrs caused by mechanical damage to the secondary battery 100 and reducing the mass of the second current collector 221, thereby improving the mass energy density of the secondary battery 100.

[0056] In some embodiments, the second active layer 222 is infiltrated by the above-mentioned electrolyte within the housing 10 to undergo an electrochemical reaction. The second active layer 222 includes a negative electrode active material, a conductive agent, a binder, etc. The above-mentioned materials are mixed and stirred evenly and coated on the surface of the second current collector 221 to obtain the second active layer 222. The negative electrode active material may include at least one of graphite, silicon, hard carbon, and carbon fiber.

[0057] In a second aspect of the present application, an electronic device is further proposed, including the secondary battery 100 according to any one of the embodiments of the first aspect above. The electronic device of the embodiments of the present application is not particularly limited, and it may be any electronic device known in the prior art. For example, the electronic device includes but is not limited to Bluetooth headsets, mobile phones, tablets, laptop computers, electric toys, electric tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy, and an electric aircraft toy, etc. The spacecraft may include an airplane, a rocket, a space shuttle, and a spaceship, etc.

[0058] Test part:

[0059] 1. External short circuit test of the secondary battery:

[0060] Place the secondary battery sample in a test environment of 25 ± 2 °C, and short-circuit the positive and negative electrodes of the sample with a load resistor of 40 ± 20 mΩ until one of the following conditions is reached to end the test: 1) Stop when the sample voltage is lower than 0.1 V and the surface temperature drops to the test environment temperature ± 10 °C; 2) If the sample voltage cannot drop to 0.1 V, stop when the surface temperature drops to the test environment temperature.

[0061] Passing standard: After the above steps, the secondary battery sample does not explode, the surface temperature of the sample does not exceed 150 °C, and it does not catch fire to pass.

[0062] Example 1

[0063] <Preparation of the first electrode sheet>:

[0064] The first electrode is the positive electrode. The positive active material lithium cobalt oxide (LiCoO₂), carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75 wt%, and it is stirred evenly.

[0065] Polyethylene terephthalate is selected as the first polymer layer, and the thickness of the first polymer layer is 6 μm. A first metal layer and a second metal layer made of aluminum with a thickness of 1.5 μm are provided on the two surfaces of the first polymer layer to obtain the first current collector. The above slurry is coated on the coating area of the surface of the first current collector and an empty foil area is reserved. The slurry is dried to obtain the first electrode with the first active layer coated on the surface.

[0066] <Preparation of the second electrode>:

[0067] The second electrode is the negative electrode. Graphite is used as the negative active material. The negative active material graphite, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed in a weight ratio of 96:2:2, and deionized water is added as a solvent to prepare a slurry with a solid content of 70 wt%, and it is stirred evenly.

[0068] Copper foil is selected as the second current collector. The above slurry is coated on the surface of the second current collector and an empty foil area is reserved. The slurry is dried to obtain the second electrode with the second active layer coated on the surface.

[0069] <Preparation of the separator>:

[0070] A polyethylene porous membrane is used as the base layer, and a ceramic layer containing alumina ceramic and PVDF binder is coated on one surface of the base layer as the separator (CCS). Among them, the mass percentage content of alumina ceramic in the ceramic layer is 95%.

[0071] <Preparation of the electrolyte>:

[0072] In a dry argon atmosphere, first, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent, and then lithium salt lithium hexafluorophosphate (LiPF₆) is added to the basic organic solvent and dissolved and mixed evenly to obtain an electrolyte with a LiPF₆ mass concentration of 12.5%.

[0073] <Preparation of the secondary battery>:

[0074] Select an aluminum foil with a length of 38 mm, a width of 6 mm, and a thickness of 80 μm as the first tab. The first tab is provided in the empty foil area of the first metal layer. The first tab includes a first connection portion electrically connected to the first metal layer. A first heat absorber is provided on the surface of the first tab facing away from the first metal layer. The first heat absorber is a graphite sheet with a thickness of 20 μm. Along the thickness direction of the first tab, the first heat absorber covers the first connection portion. The first electrode, the separator, and the second electrode are stacked in sequence and then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then electrolyte is injected. After vacuum packaging, standing, forming, capacity measurement, degassing, edge trimming and other processes, a secondary battery is obtained.

[0075] The relevant parameters in Comparative Example 1 and Examples 1 to 10 are shown in Table 1 below.

[0076] Among them, no first heat absorber is provided on the surface of the first tab in Comparative Example 1 facing away from the first metal layer. The specific heat capacities of the first heat absorbers in Examples 1 to 3 are different. The thicknesses of the first heat absorbers in Example 1 and Examples 4 to 7 are different. The materials of the first heat absorbers in Examples 8 to 10 are paraffin, and the specific heat capacities of the first heat absorbers in Examples 8 to 10 are different.

[0077] Table 1

[0078]

[0079]

[0080] Note: In Table 1, "\ " means that the parameter is not included.

[0081] According to Table 1 above, combined with Comparative Example 1 and Examples 1 to 11, it can be seen that by providing a first heat absorber on the surface of the first tab facing away from the first metal layer, along the thickness direction of the first tab, the projection of the first heat absorber overlaps at least part of the first connection portion. The first heat absorber can absorb the heat generated when the first tab has current flowing through it, and then can reduce the rapid transmission of heat, thereby reducing the heat transferred from the first tab to the second electrode and reducing the temperature accumulation of the first tab, so as to improve the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery. Therefore, the passing rate of the external short-circuit test of the secondary battery can be improved.

[0082] Combined with Embodiments 1 to 3, it can be seen that when the first heat-absorbing member includes graphite, the larger the specific heat capacity of the first heat-absorbing member, the stronger the ability of the first heat-absorbing member to absorb the heat of the first tab, and the smaller the temperature rise. The better the effect of improving the thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery, so the higher the passing rate of the external short-circuit test of the secondary battery. When the specific heat capacity of the first heat-absorbing member is less than 1300 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious. By setting the specific heat capacity of the first heat-absorbing member ≥ 1300 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab can be improved, and then the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery can be improved, and the passing rate of the external short-circuit test of the secondary battery can be increased.

[0083] Combined with Embodiment 1 and Embodiments 4 to 7, it can be seen that the larger the thickness of the first heat-absorbing member, the stronger the ability of the first heat-absorbing member to absorb the heat of the first tab, and the smaller the temperature rise. The better the effect of improving the thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery, so the higher the passing rate of the external short-circuit test of the secondary battery. When the thickness of the first heat-absorbing member is less than 10 μm, the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious. By setting the thickness of the first heat-absorbing member ≥ 10 μm, the ability of the first heat-absorbing member to absorb the heat of the first tab can be improved, and then the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery can be improved, and the passing rate of the external short-circuit test of the secondary battery can be increased. When the thickness of the first heat-absorbing member is greater than 50 μm, continuing to increase the thickness of the first heat-absorbing member, the improvement of the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious, and it is easy to consume more energy density of the secondary battery. By setting the thickness of the first heat-absorbing member ≤ 50 μm, the energy density of the secondary battery can be increased.

[0084] Combined with Embodiments 8 to 10, it can be seen that when the first heat-absorbing member includes paraffin, the larger the specific heat capacity of the first heat-absorbing member, the stronger the ability of the first heat-absorbing member to absorb the heat of the first tab, and the smaller the temperature rise. The better the effect of improving the thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery, so the higher the passing rate of the external short-circuit test of the secondary battery. When the specific heat capacity of the first heat-absorbing member is less than 3000 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab is not obvious. By setting the specific heat capacity of the first heat-absorbing member ≥ 3000 J / (kg·K), the ability of the first heat-absorbing member to absorb the heat of the first tab can be improved, and then the problem of thermal runaway caused by overheating of the first tab during high-current discharge of the secondary battery can be improved, and the passing rate of the external short-circuit test of the secondary battery can be increased.

[0085] The above are only embodiments of the present application, and thus do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present application.

Claims

1. A secondary battery, comprising a first pole piece and a second pole piece with opposite polarities, wherein the first pole piece comprises a first current collector and a first active layer disposed on a surface of the first current collector, the first current collector comprises a first polymer layer, a first metal layer and a second metal layer, and the first metal layer and the second metal layer are disposed on opposite surfaces of the first polymer layer, respectively; It is characterized in that A first pole tab is disposed on a surface of the first metal layer facing away from the first polymer layer, the first pole tab includes a first connecting portion electrically connected to the first metal layer, a first heat absorbing member is disposed on a surface of the first pole tab facing away from the first metal layer, and along a thickness direction of the first pole tab, a projection of the first heat absorbing member overlaps with at least a portion of the first connecting portion.

2. The secondary battery according to claim 1, characterized in that: Along the thickness direction of the tab, the first heat absorption member covers the first connection portion.

3. The secondary battery according to claim 2, characterized in that: The first heat absorption member covers the first electrode tab along the thickness direction of the electrode tab.

4. The secondary battery according to claim 1, characterized in that: The surface of the first metal layer facing away from the first polymer layer includes a connected coating area and a hollow foil area, the coating area is provided with the first active layer, and the hollow foil area is provided with the first electrode tab.

5. The secondary battery according to claim 1, characterized in that: The first heat absorbing member includes graphite, and the specific heat capacity of the first heat absorbing member is ≥1300 J / (kg·K).

6. The secondary battery according to claim 1, characterized in that: The first heat sink includes a phase change material.

7. The secondary battery according to claim 6, characterized in that: The first heat absorbing element includes paraffin, and the specific heat capacity of the first heat absorbing element is ≥3000 J / (kg·K).

8. The secondary battery according to claim 1, characterized in that: The first heat absorbing member is a metal foil.

9. The secondary battery according to claim 8, characterized in that: The first heat absorbing member is aluminum foil.

10. The secondary battery according to any one of claims 5 to 9, characterized in that: The first heat absorbing member has a thickness of 10 μm to 50 μm.

11. The secondary battery according to claim 1, characterized in that: The first connecting portion, the first metal layer and the second metal layer are connected by riveting or roller welding.

12. The secondary battery according to claim 1, characterized in that: A second pole lug is provided on a surface of the second metal layer facing away from the first polymer layer, the second pole lug is connected to the first pole lug, the second pole lug includes a second connecting portion electrically connected to the second metal layer, a second heat absorbing member is provided on a surface of the second pole lug facing away from the second metal layer, and along the thickness direction of the second pole lug, a projection of the second heat absorbing member overlaps with at least part of the second connecting portion.

13. The secondary battery according to any one of claims 1 to 9, characterized in that: The second pole piece includes a second current collector and a second active layer disposed on the surface of the second current collector, the second current collector includes a second polymer layer, a third metal layer and a fourth metal layer, and the third metal layer and the fourth metal layer are disposed on two opposite surfaces of the second polymer layer respectively; A third pole tab is disposed on a surface of the third metal layer facing away from the second polymer layer, the third pole tab includes a third connecting portion electrically connected to the third metal layer, and a third heat absorbing member is disposed on a surface of the third pole tab facing away from the third metal layer, and along a thickness direction of the third pole tab, a projection of the third pole tab of the third heat absorbing member overlaps with at least a portion of the third connecting portion.

14. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 13.

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