Pole piece, battery monomer, battery and electric device

Abstract

The utility model relates to a pole piece, a battery monomer, a battery and an electric device. The pole piece comprises a current collector; the active material layers and the thermal expansion layers are stacked on at least one side, arranged in the thickness direction, of the current collector, and the active material layers and the thermal expansion layers are alternately arranged in the length direction of the current collector. According to the pole piece, the battery monomer, the battery and the electric device provided by the invention, the thermal runaway risk of the battery monomer can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a pole piece, a battery monomer, a battery and a power utilization device. BACKGROUND

[0002] With the rapid development of the new energy industry, as an important part of the new energy industry, the safety of batteries has gradually attracted attention. The heat diffusion of batteries is one of the key contents of battery safety research. Generally, the thermal runaway of batteries starts from a small location, and after heating, it triggers a chain reaction in other areas, resulting in serious consequences. How to suppress the thermal runaway of batteries in the smallest area has a great impact on battery safety.

[0003] The prior art usually makes a smoke exhaust channel at the module level, and the pressure relief valve of the battery monomer is opened to quickly dissipate heat through the smoke exhaust channel. In addition, a heat insulation pad is added between each adjacent two battery monomers to prevent heat diffusion and ignition of adjacent battery monomers after the battery monomer thermal runaway.

[0004] That is, the main research direction of the prior art is the heat insulation and heat diffusion outside the battery monomer in the battery, but there is not enough research on the heat diffusion inside the battery monomer. If the heat spreads inside the battery monomer, it is easy to cause a chain reaction, leading to battery monomer thermal runaway, and more likely to cause a fire explosion. Utility model content

[0005] Therefore, it is necessary to provide a pole piece, a battery monomer, a battery and a power utilization device which can reduce the risk of battery monomer thermal runaway by researching the inside of the battery monomer.

[0006] A pole piece, the pole piece comprising:

[0007] a current collector;

[0008] an active material layer and a thermal expansion layer, both of which are stacked on at least one side of the current collector in the thickness direction of the current collector, and the active material layer and the thermal expansion layer are alternately arranged along the length direction of the current collector.

[0009] In some embodiments, the active material layer and the thermal expansion layer are both stacked on each side of the current collector in the thickness direction of the current collector.

[0010] In some embodiments, the expansion temperature of the thermal expansion layer is T, T≥80℃.

[0011] In some embodiments, the pole piece further comprises a ceramic layer;

[0012] The current collector has a coating surface arranged along the thickness direction thereof, the coating surface includes a first coating area and a second coating area arranged along the width direction of the current collector in sequence, the active material layer and the thermal expansion layer are alternately coated in the first coating area, and the ceramic layer is coated in the second coating area.

[0013] In some embodiments, the coating surface further includes a blank area, the blank area is arranged on the side of the second coating area away from the first coating area along the width direction of the current collector.

[0014] In some embodiments, the thermal expansion layer is a composite expansion material layer, the composite expansion material layer is composed of one or more of a binder, a conductive additive, a flame retardant, a heat insulating agent and a polymer modifier, and an expansion agent.

[0015] A battery cell includes an electrode assembly, the electrode assembly is wound or stacked by the separator film and the tab of any one of the above embodiments;

[0016] The battery cell has a first state and a second state, when the battery cell is in the first state, the active material layer and the thermal expansion layer are arranged flush on the surface of the current collector, when the battery cell is in the second state, the thermal expansion layer protrudes from the active material layer, is located on the same side of the current collector and each two adjacent thermal expansion layers define a gas guide channel.

[0017] When the temperature inside the battery cell reaches the expansion temperature of the thermal expansion layer, the battery cell switches from the first state to the second state.

[0018] In some embodiments, the battery cell further includes a shell, the shell has an end cover, the end cover is provided with a pressure relief valve; the electrode assembly is arranged in the shell, and the electrode assembly is wound by the separator film and the tab;

[0019] When the battery cell is in the second state, the gas guide channel and the projection of the pressure relief valve in the height direction of the battery cell at least partially overlap.

[0020] A battery includes the battery cell of any one of the above embodiments.

[0021] An electric device includes the battery of the above embodiments.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The above polar sheet, battery cell, battery and electric device, when the polar sheet is applied in the battery cell, the isolation film and the polar sheet are wound or stacked to form an electrode assembly of the battery cell. Specifically, the electrode assembly wound is a wound structure, and the electrode assembly stacked is a stacked structure. When the internal temperature of the battery cell reaches the expansion temperature of the thermal expansion layer, the thermal expansion layer expands and protrudes from the active material layer on the same side, and pushes open the isolation film, resulting in a gap between the isolation film and the polar sheet, thereby cutting off the ion conduction between the positive polar sheet and the negative polar sheet, delaying the thermal runaway caused by chemical cross-talk. Moreover, the part of the two thermal expansion layers on the same side of the current collector and arranged adjacent to each other protruding from the active material layer defines a gas guide channel, and the arrangement of the gas guide channel can slow down the spread of heat in the battery cell, guide the directional flow of high-temperature smoke, and finally discharge through the pressure relief valve of the battery cell, reducing the risk of thermal runaway of the battery cell. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a top view of the polar sheet in an embodiment of the present application;

[0025] Figure 2 is a top view of the polar sheet in an embodiment of the present application; Figure 1 is a top view of the polar sheet in an embodiment of the present application;

[0026] Figure 3 is a top view of the polar sheet in an embodiment of the present application; Figure 1 is a front view of the polar sheet in the first state;

[0027] Figure 4 is a front view of the polar sheet in the second state. Figure 1

[0028] REFERENCE NUMERALS:

[0029] 100, polar sheet; 10, current collector; 11, first coating area; 12, second coating area; 13, blank area; 20, active material layer; 30, thermal expansion layer; 40, ceramic layer;

[0030] X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings. In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0032] ​In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0033] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0034] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0035] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be the first feature directly above or obliquely above the second feature, or only indicate that the first feature is higher than the second feature in horizontal height. The first feature "below", "below" and "below" the second feature can be the first feature directly below or obliquely below the second feature, or only indicate that the first feature is lower than the second feature in horizontal height.

[0036] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0037] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing.

[0038] Existing technologies typically involve creating exhaust channels at the module level, allowing for rapid heat dissipation through these channels after the pressure relief valves of individual battery cells open. Furthermore, thermal insulation pads are added between each pair of adjacent battery cells to prevent thermal runaway from causing heat diffusion and igniting adjacent cells.

[0039] In other words, current research mainly focuses on the external heat insulation and heat diffusion of battery cells, but there is insufficient research on the internal heat diffusion of battery cells. If heat spreads and propagates inside the battery cell, it can easily cause a chain reaction, leading to thermal runaway and increasing the risk of fire and explosion.

[0040] Please see Figures 1 to 4 To mitigate the problem of thermal runaway, the applicant conducted in-depth research on the internal structure of the battery cell and designed an electrode 100 that can reduce the risk of thermal runaway. This electrode 100 is used to form both the positive and negative electrode. The electrode 100 includes a current collector 10, an active material layer 20, and a thermal expansion layer 30. The active material layer 20 and the thermal expansion layer 30 are both stacked on at least one side of the current collector 10 along its thickness direction Z, and the active material layer 20 and the thermal expansion layer 30 are alternately arranged along the length direction X of the current collector 10.

[0041] The current collector 10 is used to collect current and serves as a carrier to support the active material layer 20 and the thermal expansion layer 30. The active material layer 20 is used to generate current, and the thermal expansion layer 30 is used to expand when it reaches its expansion temperature. Both the active material layer 20 and the thermal expansion layer 30 are stacked with the current collector 10.

[0042] Taking a lithium-ion battery as an example, for the positive electrode, the current collector 10 can be made of aluminum, and the active material layer 20 can be made of lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. For the negative electrode, the current collector 10 can be made of copper, and the active material layer 20 can be made of carbon or silicon, etc.

[0043] Both the positive and negative electrode sheets can have a single expansion material layer or a composite expansion material layer. A single expansion material layer refers to a coating layer formed by applying and drying a single expansion agent, while a composite expansion material layer refers to a coating layer formed by applying and drying a material composed of one expansion agent and one or more non-expansion agents, or multiple expansion agents, or multiple expansion agents and one or more non-expansion agents.

[0044] For example, the thermal expansion layer 30 is a composite expansion material layer, which may be, but is not limited to, composed of one or more of an adhesive, conductive additive, flame retardant, heat insulation agent and polymer modifier, as well as an expansion agent.

[0045] Expanding agents include, but are not limited to, thermally expandable microspheres, expanded graphite, and chemically expanded flame retardants. They are characterized by being solid at room temperature, suitable for slurry coating, and not participating in the internal chemical reactions of the battery cells. The expanding agent content in the composite expanding material layer ranges from 60% to 100%.

[0046] The adhesive includes, but is not limited to, one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylic acid, and styrene-butadiene copolymer rubber (SBR). The adhesive can increase the adhesion of the thermal expansion layer 30, prevent powdering, and is itself resistant to electrolyte corrosion. The adhesive content in the composite expansion material layer is 0 to 10%.

[0047] The conductive additive includes, but is not limited to, one or more materials such as conductive carbon black, graphite particles, carbon nanotubes, graphene, and metal powder. The conductive additive is dispersed within the thermal expansion layer 30 to increase its electrical conductivity. The content of the conductive additive in the composite expansion material layer is 0% to 30%.

[0048] The flame retardant may be, but is not limited to, one or more of halogenated flame retardants, organophosphorus flame retardants, etc., and the heat insulation agent may be, but is not limited to, one or more of ultrafine silica (SiO2), aerogel, etc. The content of flame retardant and heat insulation agent in the composite expansion material layer is 0 to 15%.

[0049] Polymer modifiers include, but are not limited to, one or more materials such as dispersants and softeners, which can meet the process conditions of stirring or rolling or improve production yield during processing. The content of polymer modifier in the composite expandable material layer is 0 to 5%.

[0050] As an example, the composite thermal expansion material layer is formed using 96% expanded graphite + 2% carbon nanotubes + 1.5% polyvinylidene fluoride (PVDF) + 0.5% halogen flame retardant, or the composite expansion material is formed using 85% thermal expansion microspheres + 3% conductive carbon black + 2% carbon nanotubes + 5% PVDF + 5% organophosphorus flame retardant.

[0051] When the electrode 100 is applied within a battery cell, the separator and the electrode 100 are wound or stacked to form the electrode assembly of the battery cell. Specifically, the wound electrode assembly is a wound structure, and the stacked electrode assembly is a stacked structure. When the internal temperature of the battery cell reaches the expansion temperature of the thermal expansion layer 30, the thermal expansion layer 30 expands and protrudes beyond the active material layer 20 on the same side, pushing open the separator and creating a gap between the separator and the electrode 100. This cuts off the conduction of ions between the positive and negative electrode plates, delaying thermal runaway caused by chemical crosstalk. Furthermore, the portions of the two thermal expansion layers 30 located on the same side of the current collector 10 and adjacent to each other, protruding from the active material layer 20, define a gas guiding channel. The gas guiding channel can slow down the spread of heat throughout the battery cell, guide the directional flow of high-temperature flue gas, and ultimately discharge it through the pressure relief valve of the battery cell, reducing the risk of thermal runaway of the battery cell.

[0052] In some embodiments, the active material layer 20 and the thermal expansion layer 30 are both stacked on each side of the current collector 10 along its thickness direction Z. The active material layer 20 on both sides of the current collector 10 can significantly improve the energy density of the battery cell. When the thermal expansion layer 30 is disposed on both sides of the current collector 10 and expands, it can push open the separator on both sides of the current collector 10 and form a gas-conducting channel on both sides of the current collector 10. This gas-conducting and blocking effect is better, thereby slowing the spread of heat along the length direction X of the electrode 100 and further reducing the risk of thermal runaway of the battery cell.

[0053] In some embodiments, the expansion temperature of the thermal expansion layer 30 is T, where T ≥ 80°C. That is, when the internal temperature of the battery cell reaches 80°C or higher, the expansion of the thermal expansion layer 30 will push open the separator and form a gas-conducting channel. With T ≥ 80°C, the expansion temperature of the thermal expansion layer 30 is not too high, allowing the battery cell to dissipate heat promptly through the gas-conducting channel formed by the expansion of the thermal expansion layer 30 in the early stages of thermal runaway. This effectively suppresses subsequent side reactions, delays the heat release of the battery cell, and protects the battery cell from fire and localized high-temperature accumulation.

[0054] In some embodiments, the electrode 100 further includes a ceramic layer 40; the current collector 10 has a coating surface disposed along its thickness direction Z, the coating surface including a first coating area 11 and a second coating area 12 sequentially disposed along the width direction Y of the current collector 10, the active material layer 20 and the thermal expansion layer 30 being alternately coated in the first coating area 11, and the ceramic layer 40 being coated in the second coating area 12. The coating surface also includes a blank area 13, which is disposed along the width direction Y of the current collector 10 on the side of the second coating area 12 away from the first coating area 11. The blank area 13 refers to an uncoated area, and the blank area 13 is used for die-cutting to form an electrode tab.

[0055] Specifically, the current collector 10 has two coated surfaces along its thickness direction Z, and each coated surface is coated with an active material layer 20, a thermal expansion layer 30 and a ceramic layer 40.

[0056] Since the current collectors 10 of both the positive and negative electrodes are made of metal, burrs are easily generated at the edges of the current collectors 10 during the die-cutting and tab formation process in the blank area 13. Therefore, by coating a ceramic layer 40 in the second coating area 12, the generation of burrs can be reduced during die-cutting. Moreover, when the electrode 100 is wound or stacked with the separator, the ceramic layer 40, due to its certain thickness, will protrude from the burrs in the thickness direction Z of the current collector 10 and contact the separator. This design is equivalent to the ceramic layer 40 separating the separator and the burrs to prevent the burrs from piercing the separator, thereby reducing the risk of short circuit caused by burr piercing and further improving the safety performance of the battery.

[0057] This application also provides a battery cell, which includes an electrode assembly formed by winding or stacking a separator and the electrode sheet 100 described in any of the above embodiments. The battery cell has a first state and a second state. When the battery cell is in the first state, the active material layer 20 and the thermal expansion layer 30 are flush with the surface of the current collector 10 facing away from each other. When the battery cell is in the second state, the thermal expansion layer 30 protrudes from the active material layer 20, and the portions of two adjacent thermal expansion layers 30 protruding from the active material layer 20 on the same side of the current collector 10 define a gas guiding channel. When the internal temperature of the battery cell reaches the expansion temperature of the thermal expansion layer 30, the battery cell switches from the first state to the second state.

[0058] The separator can be made of PP (polypropylene) or PE (polyethylene), etc. Furthermore, the electrode assembly can be a wound structure or a stacked structure; the embodiments of this application are not limited to these.

[0059] The first state represents the normal operating state of the battery cell. In this state, the active material layer 20 and the thermal expansion layer 30, located on the same side of the current collector 10, have the same thickness and are flush, not affecting the electrochemical reaction of the battery cell. When the battery cell is abused and its internal heat dissipation is insufficient, heat accumulates inside the battery cell, causing the temperature to reach the expansion temperature of the thermal expansion layer 30. In this state, the battery cell switches to the second state. In the second state, the thermal expansion layer 30 expands and increases in thickness, protruding beyond the active material layer 20 on the same side. This creates a gap between the separator and the electrode 100, thereby interrupting ion conduction between the positive and negative electrode plates and delaying thermal runaway caused by chemical crosstalk. Furthermore, the portions of the two adjacent thermal expansion layers 30 on the same side of the current collector 10 that protrude from the active material layer 20 define a gas-guiding channel. This channel slows the spread of heat throughout the battery cell, guides the directional flow of high-temperature flue gas, and ultimately discharges it through the battery cell's pressure relief valve, reducing the risk of thermal runaway.

[0060] The battery cell in this application has the effects of any of the above embodiments, so it will not be described again here.

[0061] In some embodiments, the battery cell further includes a housing with an end cap and a pressure relief valve. An electrode assembly is disposed within the housing and is formed by winding a separator and an electrode sheet 100. When the battery cell is in the second state, the projections of the gas guide channel and the pressure relief valve in the height direction of the battery cell at least partially overlap. In this way, the high-temperature flue gas can flow almost in a straight line under the guidance of the gas guide channel and force open the pressure relief valve to be discharged. This method can reduce the diffusion and spread of high-temperature flue gas in the direction where it intersects with the gas guide channel, improve pressure relief efficiency, and effectively mitigate the occurrence of thermal runaway.

[0062] It is understandable that in a single battery cell, the width direction Y of the electrode 100 when it is unfolded coincides with the axial direction of the electrode assembly formed by the winding of the electrode 100, and the axial direction of the electrode assembly coincides with the height direction of the single battery cell.

[0063] This application also provides a battery comprising a single battery cell as described in any of the foregoing embodiments. The battery in this application has the effects of any of the foregoing embodiments, and therefore will not be described again here.

[0064] This application also provides an electrical device comprising a battery as described in the above embodiments. The electrical device in this application has the effects of any of the above embodiments, and therefore will not be repeated here.

[0065] The electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0066] It should be understood that the technical solutions described in the embodiments of this application are not limited to the electrical devices described above.

[0067] The aforementioned electrode 100, battery cell, battery, and electrical device, when the electrode 100 is applied within the battery cell, form an electrode assembly of the battery cell by winding or stacking the separator and electrode 100. Specifically, the winding electrode assembly is a wound structure, and the stacking electrode assembly is a stacked structure. When the internal temperature of the battery cell reaches the expansion temperature of the thermal expansion layer 30, the thermal expansion layer 30 expands and protrudes beyond the active material layer 20 located on the same side, pushing open the separator and creating a gap between the separator and the electrode 100. This cuts off the conduction of ions between the positive and negative electrode plates, delaying thermal runaway caused by chemical crosstalk. Furthermore, the portions of the two thermal expansion layers 30 located on the same side of the current collector 10 and adjacent to each other, protruding from the active material layer 20, define a gas guiding channel. The gas guiding channel can slow down the spread of heat throughout the battery cell, guide the directional flow of high-temperature flue gas, and ultimately discharge it through the pressure relief valve of the battery cell, reducing the risk of thermal runaway of the battery cell.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A pole piece, characterized in that, The pole piece comprises: a current collector (10) having a coating surface arranged along a thickness direction (Z) thereof, the coating surface comprising a first coating area (11) and a second coating area (12) arranged along a width direction (Y) of the current collector (10) in sequence, and a blank area (13) arranged on a side of the second coating area (12) away from the first coating area (11) along the width direction (Y) of the current collector (10); an active material layer (20) and a thermal expansion layer (30) both arranged on at least one side of the current collector (10) along the thickness direction (Z) thereof, and the active material layer (20) and the thermal expansion layer (30) being alternately coated on the first coating area (11) along a length direction (X) of the current collector (10); a ceramic layer (40) coated on the second coating area (12).

2. The pole piece of claim 1, wherein The active material layer (20) and the thermal expansion layer (30) are both arranged on each side of the current collector (10) along the thickness direction (Z) thereof.

3. The pole piece of claim 1, wherein The thermal expansion layer (30) has an expansion temperature T, and T≥80℃.

4. A battery cell characterized by, The battery cell comprises an electrode assembly, the electrode assembly being wound or stacked by the separator film and the pole piece according to any one of claims 1 to 3; The battery cell has a first state and a second state, when the battery cell is in the first state, the active material layer (20) and the thermal expansion layer (30) are arranged flush with the surface of the current collector (10) in a back-to-back manner, when the battery cell is in the second state, the thermal expansion layer (30) protrudes from the active material layer (20), is located on the same side of the current collector (10), and each adjacent two thermal expansion layers (30) protruding from the active material layer (20) define a gas guide channel; When the temperature inside the battery cell reaches the expansion temperature of the thermal expansion layer (30), the battery cell switches from the first state to the second state.

5. The battery cell of claim 4, wherein, The battery cell further comprises a shell having an end cover provided with a pressure relief valve; the electrode assembly is arranged in the shell, and the electrode assembly is wound by the separator film and the pole piece; When the battery cell is in the second state, the gas guide channel and the projection of the pressure relief valve in the height direction of the battery cell at least partially overlap.

6. A battery, characterized by The battery cell according to claim 4 or 5.

7. An electrical device, characterized by The battery according to claim 6.

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