Bipolar pole piece, bipolar battery and electric equipment

Abstract

The invention provides a bipolar pole piece, a bipolar battery and electric equipment. The bipolar pole piece is provided with the air suction layer and the sealing area at the same time, when the bipolar pole piece is applied to the bipolar battery, the bipolar pole piece and the adjacent bipolar pole piece can form a sealed space, exhaust treatment does not need to be carried out on the bipolar pole piece after formation, and the application difficulty of liquid or gel electrolyte in the bipolar battery is effectively reduced.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a bipolar pole piece, a bipolar battery and an electrical device. Background Art

[0002] Bipolar batteries have advantages such as high voltage, high energy density, and high current capacity, but their structure is more complex than that of conventional batteries. Bipolar batteries include multiple stacked bipolar pole pieces and two unipolar pole pieces at both ends. The opposite sides of the bipolar pole pieces are coated with active materials of different electrode polarities, while the unipolar pole pieces are coated with an active material layer only on one side of the current collector. Conventional bipolar batteries use solid-state electrolytes, but due to the current immaturity of solid-state electrolytes, the performance of the final battery is not as good as that of batteries using liquid or gel electrolytes.

[0003] Bipolar batteries typically consist of multiple independently operating cells, each of which includes a current collector, a positive electrode material layer located on one surface of the current collector, an electrolyte, and a negative electrode material layer and current collector located on the other surface of the current collector. Due to this special structure, if a liquid or gel electrolyte with fluidity is used in a bipolar battery, short circuits often occur due to the electrolytes of different cells coming into contact. To address this technical issue, when using a liquid or gel electrolyte in a bipolar battery, each cell needs to be sealed.

[0004] However, during the battery's formation process, a large amount of gas (e.g., hydrogen, methane, ethane, carbon monoxide, carbon dioxide, etc.) is generated inside the battery. Conventional battery cells need to be resealed after formation to remove the gas. However, for bipolar batteries with multiple sealed cells in a single cell, this is a huge workload. Therefore, liquid electrolytes or gel electrolytes are currently difficult to use in bipolar batteries. Summary of the Invention

[0005] In view of this, embodiments of the present application provide a bipolar pole piece, a bipolar battery, and an electrical device. The bipolar pole piece is provided with both an air-absorbing layer and a sealing area. When used in a bipolar battery, it forms a sealed space with adjacent bipolar pole pieces, eliminating the need for post-formation venting, effectively reducing the difficulty of using liquid or gel electrolytes in bipolar batteries.

[0006] In a first aspect, an embodiment of the present application provides a bipolar electrode sheet, comprising a current collector and dressing layers disposed on opposite sides of the current collector, wherein the electrode polarities of the two dressing layers are different;

[0007] An air-absorbing layer is further provided on at least one side surface of the current collector, and the air-absorbing layer and the dressing layer are both in direct contact with the current collector; the air-absorbing layer comprises a porous material;

[0008] Sealing areas are provided on the edges of the two opposite sides of the current collector, and the dressing layer and the air-absorbing layer are both arranged in the accommodating space formed by the sealing areas.

[0009] The porous material in the air-absorbing layer of the bipolar pole piece can effectively absorb gases generated by the bipolar pole piece's dressing layer during the formation process and subsequent charge-discharge cycles. When the bipolar pole piece is applied to a bipolar battery, there is no need to vent each electrochemical cell after formation, which greatly saves the preparation process and facilitates the commercial application of bipolar batteries using liquid electrolytes / gel electrolytes. In addition, the battery also produces gas during the charge-discharge cycle, and the air-absorbing layer can also absorb this gas, thereby effectively reducing the risk of sealing damage caused by internal inflation of the electrochemical cell due to gas production during the cycle, which is beneficial to improving the battery's cycle performance. Furthermore, the edges of the bipolar pole piece on both opposing sides have an annular sealing area. When multiple bipolar pole pieces are stacked, the sealing area can be used to seal each electrochemical cell, preventing liquid short circuits caused by electrolyte leakage, maintaining the normal operation of the final bipolar battery and ensuring its good safety performance.

[0010] Optionally, the gas absorption amount of the material of the gas absorption layer per unit mass is αg, the total gas production of the bipolar pole piece during the charge and discharge process is expected to be βg, and the single-surface density of the gas absorption layer is A g / m 2 The sum of the surface areas of the getter layers in the bipolar pole piece is S m 2 , the bipolar pole piece satisfies: S≥β / (A*α).

[0011] Optionally, the thickness of the air-absorbing layer is less than or equal to the thickness of the dressing layer.

[0012] Optionally, the specific surface area of ​​the porous material is ≥200m 2 / g.

[0013] Optionally, the porous material includes at least one of modified or unmodified activated carbon, modified or unmodified oxygen vacancy metal oxides, modified or unmodified transition metal oxide materials, modified or unmodified graphene, and modified or unmodified metal-organic framework materials.

[0014] Optionally, a sealing ring is provided on the sealing area, and an outer edge of the sealing ring is flush with an outer edge of the current collector, or the sealing ring has an exposed portion relative to the current collector.

[0015] Optionally, the sealing area includes a first sealing ring portion and a second sealing ring portion, wherein the first sealing ring portion is arranged close to the dressing layer, and the second sealing ring portion is arranged on the periphery of the first sealing ring portion; a first sealing ring is provided on the first sealing ring portion, and a second sealing ring is provided on the second sealing ring portion;

[0016] The compatibility of the material of the first sealing ring with the electrolyte is better than that of the material of the second sealing ring with the electrolyte, and / or the sealing performance of the second sealing ring is better than that of the first sealing ring.

[0017] Optionally, the material of the first sealing ring and the material of the second sealing ring each independently include at least one of modified or unmodified polypropylene, modified or unmodified polyethylene, modified or unmodified epoxy resin, and modified or unmodified polyacrylate.

[0018] Optionally, the width of the first sealing ring portion and the second sealing ring portion are independently 5 mm to 30 mm.

[0019] A second aspect of the embodiment of the present application provides a bipolar battery, comprising a plurality of bipolar pole pieces provided in the first aspect of the embodiment of the present application, wherein the plurality of bipolar pole pieces are stacked;

[0020] The first pole piece and the second pole piece are defined as any two adjacent pole pieces among the plurality of bipolar pole pieces; wherein a diaphragm and an electrolyte are further provided between the first pole piece and the second pole piece;

[0021] The sealing ring on the side surface of the first pole piece facing the second pole piece and the sealing ring on the side surface of the second pole piece facing the first pole piece form a sealed receiving space, and the receiving space has at least one getter layer.

[0022] A third aspect of the embodiments of the present application provides an electrical device, including the bipolar battery provided in the second aspect of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A top view of a bipolar pole piece provided in one embodiment of the present application;

[0024] Figure 2A A top view of a bipolar pole piece provided in another embodiment of the present application;

[0025] Figure 2B for Figure 2A A schematic diagram of the cross section of the bipolar pole piece;

[0026] Figure 2C is a schematic structural diagram of a cross section of a bipolar pole piece provided in another embodiment of the present application;

[0027] Figure 3 is a top view of a bipolar pole piece provided in yet another embodiment of the present application;

[0028] Figures 4A to 4C Schematic diagram of different getter layer distributions provided by different embodiments of the present application;

[0029] Figure 5 1 is a schematic structural diagram of a cross section of an electrochemical unit in a bipolar battery provided in one embodiment of the present application.

[0030] Explanation of the accompanying figures: 1-bipolar pole piece; 10-current collector; 20-dressing layer; 30-intake layer; 40-sealing area; 41-sealing ring; 42-first sealing ring; 43-second sealing ring. DETAILED DESCRIPTION

[0031] Currently, the difficulty in using liquid or gel electrolytes in bipolar batteries lies in the fact that any two adjacent bipolar pole pieces in a bipolar battery must form an independently operating electrochemical unit, requiring each electrochemical unit to be sealed. However, during the battery formation process, each electrochemical unit generates gas, requiring each electrochemical unit to be individually vented and resealed after formation, a significant workload.

[0032] It is understood that a bipolar battery must include multiple bipolar pole pieces stacked in layers. In the embodiments of the present application, the first pole piece and the second pole piece are defined as any two adjacent pole pieces in a plurality of adjacent stacked bipolar pole pieces. In the embodiments of the present application, the electrochemical unit includes: a current collector of the first pole piece, a structure on the surface of the first pole piece facing the second pole piece, and a current collector of the second pole piece, a structure on the surface of the second pole piece facing the first pole piece.

[0033] In order to solve the above-mentioned technical problems, an embodiment of the present application provides a bipolar pole piece, including a current collector, and a dressing layer arranged on opposite sides of the current collector, the electrode polarities of the two dressing layers are different; at least one side surface of the current collector is also provided with an air absorption layer, and the air absorption layer and the dressing layer are directly in contact with the current collector; the air absorption layer includes a porous material; sealing areas are provided on the edges of the opposite side surfaces of the current collector, and the dressing layer and the air absorption layer are both arranged in the accommodating space formed by the sealing area.

[0034] For details, please refer to Figure 1An embodiment of the present application provides a bipolar electrode 1, including a current collector 10, and dressing layers 20 arranged on opposite sides of the current collector 10, and the electrode polarities of the two dressing layers 20 are different; it can be understood that here it means that the dressing layer on the surface of one side of the current collector is a positive electrode material layer, and the dressing layer on the surface of the other side is a negative electrode material layer.

[0035] An air-absorbing layer 30 is further provided on at least one side of the current collector 10. The air-absorbing layer 30 and the dressing layer 20 are both in direct contact with the current collector. Here, the air-absorbing layer 30 and the dressing layer 20 are arranged side by side on the surface of the current collector, rather than being stacked. The air-absorbing layer 30 comprises a porous material.

[0036] The edges of the two opposite sides of the current collector are both provided with sealing areas 40, and the dressing layer 20 and the air-absorbing layer 30 are both provided in the accommodation space formed by the sealing areas 40 ( Figure 1 The area enclosed by the two black dotted boxes).

[0037] A bipolar pole piece can have an air absorption layer on one surface of the current collector, or on both opposing surfaces. This choice can be made by those skilled in the art based on practical needs. When a bipolar pole piece has an air absorption layer on only one surface, the layer can be located on either the surface with the positive electrode material layer or the surface with the negative electrode material layer, as long as the layer is present in each electrochemical unit after multiple bipolar pole pieces are stacked. Furthermore, given that the positive electrode material layer is generally thicker than the negative electrode material layer, the air absorption layer can be preferentially located on the positive electrode material layer.

[0038] The porous material in the air absorption layer of the bipolar pole piece provided in the embodiments of the present application can effectively absorb the gas generated by the bipolar pole piece's dressing layer during the formation process and subsequent charge-discharge cycles. When the bipolar pole piece is applied to a bipolar battery, there is no need to further exhaust the electrochemical cells after formation, which greatly saves the preparation process and facilitates the commercial application of bipolar batteries using liquid electrolytes / gel electrolytes. In addition, the battery also produces gas during the charge-discharge cycle, and the air absorption layer can also absorb this gas, thereby effectively reducing the risk of damage to the seal due to internal inflation of the electrochemical cells caused by gas production during the cycle, which helps to improve the battery's cycle performance.

[0039] Furthermore, the edges of the two opposite surfaces of the bipolar pole pieces are provided with an annular sealing area. When multiple bipolar pole pieces are stacked, the sealing area can be used to seal each electrochemical unit they constitute, avoiding liquid short circuits caused by leakage of liquid electrolyte / gel electrolyte, maintaining the normal operation of the final bipolar battery and ensuring its good safety performance.

[0040] In some embodiments of the present application, both opposite surfaces of the bipolar electrode have gettering layers.

[0041] Considering that in actual production, when the bipolar pole pieces are stacked, liquid glue may be used for sealing. Therefore, in the embodiment of the present application, the sealing area of ​​the bipolar pole piece may be a divided area, and the sealing area is used to carry the sealing ring. The sealing ring may be formed on the corresponding sealing area by selecting a specific material according to the needs during the subsequent stacking process of the bipolar pole pieces. In other embodiments, please refer to Figure 2A , a sealing ring 41 is provided on the sealing area 40. The above two situations do not affect the sealing of the final electrochemical unit, and those skilled in the art can choose according to actual needs.

[0042] In some implementations of this application, please see Figure 2A-2C A sealing ring 41 is provided on the sealing area. The outer edge of the sealing ring is flush with the outer edge of the current collector, or the sealing ring has an exposed portion relative to the current collector. In this way, when multiple bipolar pole pieces are stacked, the risk of contact between the current collectors of different bipolar pole pieces can be effectively reduced, thereby reducing the risk of short circuit during battery cycling. In some specific embodiments, see Figure 2C The sealing ring has an exposed portion relative to the current collector. This effectively prevents short circuits caused by contact between the current collectors of different bipolar pole pieces. The size of the exposed portion can be selected based on actual production needs. In some embodiments, the size of the exposed portion is 1mm-5mm in a direction perpendicular to the thickness of the bipolar pole piece. Specifically, the size of the exposed portion in a direction perpendicular to the thickness of the bipolar pole piece can be, but is not limited to, 1mm, 2mm, 3mm, 4mm, 5mm, etc.

[0043] It is understandable that during the assembly process of the battery cell, the electrode sheets are stacked and then subjected to a hot pressing process. In some embodiments of the present application, the thickness of the sealing ring is less than or equal to the thickness of the dressing layer and less than or equal to the thickness of the air absorption layer. In this way, during the hot pressing process of the battery cell manufacturing process, it is possible to achieve the sealing of each electrochemical unit and also facilitate the stacking of multiple bipolar electrode sheets in the corresponding position of the sealing ring without the problem of excessive thickness of the sealing ring affecting the assembly of the battery cell and the volume energy density of the final battery. In some specific embodiments, the thickness of the sealing width is less than the thickness of the dressing layer and less than the thickness of the air absorption layer; it is sufficient to achieve the sealing of the electrochemical unit.

[0044] In the embodiment of the present application, the sealing ring may be adjacent to the dressing layer and the air absorption layer, or a gap may be left between the sealing ring and the dressing layer and the air absorption layer. It can be understood that in order to make full use of the space and improve the energy density of the battery, the size of the gap between the sealing ring and the dressing layer or the air absorption layer is ≤1mm. Generally, during the formation and subsequent circulation of the battery, the liquid electrolyte in the battery cell will penetrate into the dressing layer, and there will be very little free liquid electrolyte. However, when there is a gap between the sealing ring and the dressing layer and the air absorption layer, it can serve as a buffer zone for accommodating liquid electrolytes, and it can also accommodate gas production that has not been absorbed by the air absorption layer in time during the formation and circulation of the battery.

[0045] See Figure 3 In some embodiments of the present application, the sealing area includes a first sealing ring portion and a second sealing ring portion, the first sealing ring portion is arranged on a side close to the dressing layer, and the second sealing ring portion is arranged on the periphery of the first sealing ring portion; a first sealing ring 42 is provided on the first sealing ring portion, and a second sealing ring 43 is provided on the second sealing ring portion; the compatibility of the first sealing ring material with the electrolyte is better than the compatibility of the second sealing ring material with the electrolyte, and / or the sealing performance of the second sealing ring is better than the sealing performance of the first sealing ring. In this way, it can meet the sealing needs of the bipolar battery in the production process and the use requirements of the final bipolar battery in the long-term charge and discharge cycle process. Even if a small amount of leakage occurs in the first sealing ring during the subsequent long-term charge and discharge cycle, it will not affect the performance of the battery, thereby improving the cycle stability and safety performance of the battery. Of course, considering that the electrochemical unit needs to be sealed during the subsequent stacking process of the bipolar pole pieces, at this time, the first sealing ring materials of the two adjacent bipolar pole pieces will form a complete sealing structure under the action of the external environment (for example, force field and thermal field). Considering the time required for this process, in order to save process time and improve the production efficiency of bipolar batteries, the processing time of the first sealing ring to form the seal is less than the processing time of the second sealing ring to form the sealing structure.

[0046] Similarly, the first and second sealing rings on the first and second sealing ring portions can be independently pre-installed on the bipolar pole piece, or can be provided on the bipolar pole piece before lamination. When liquid glue is selected as the raw material for forming the first and / or second sealing rings, the first and second sealing rings can be provided on the first and second sealing ring portions before lamination of the bipolar pole pieces.

[0047] In some specific embodiments, liquid glue is used as the raw material for forming the first sealing ring, and solid glue is used as the material for forming the second sealing ring.

[0048] In some embodiments of the present application, the material of the first sealing ring and the material of the second sealing ring each independently include at least one of modified or unmodified polypropylene (e.g., micro-foamed polypropylene, abbreviated as MPP), modified or unmodified polyethylene, modified or unmodified epoxy resin, and modified or unmodified polyacrylate.

[0049] In some specific embodiments of the present application, the material of the first sealing ring is selected from a low-melting-point MPP solid film material, and the material of the second sealing ring is selected from a high-melting-point MPP solid film material. It should be noted that the melting points of the low-melting-point MPP and high-melting-point MPP solid films are both within the range of 100°C-168°C, but the melting point of the low-melting-point MPP solid film material can be lower than the melting point of the high-melting-point MPP solid film material.

[0050] In some embodiments of the present application, when the first sealing ring portion and the second sealing ring portion are not separately provided, the material of the sealing ring on the sealing area is selected from the material of the above-mentioned second sealing ring.

[0051] In the embodiment of the present application, the first sealing ring portion and the second sealing ring portion may be adjacent to each other or there may be a gap between them. It is understandable that in order to fully utilize the space and improve the energy density of the battery, the size of the gap between the first sealing ring and the second sealing ring is ≤1mm.

[0052] In some embodiments of the present application, the outer edge of the second sealing ring is flush with the outer edge of the current collector, or the second sealing ring has an exposed portion relative to the current collector.

[0053] The size of the sealing ring can be adjusted according to the electrolyte to be used in the subsequent bipolar battery, as well as the material of the sealing ring and the height of the electrochemical unit, but the width of the sealing ring is within the range of 5mm-60mm. In some embodiments of the present application, the width of the first sealing ring and the second sealing ring are each independently 5mm-30mm. This is conducive to taking into account the sealing performance of the electrochemical unit and the energy density of the final battery. Specifically, the width of the first sealing ring can be, but is not limited to, 5mm, 8mm, 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 28mm, and 30mm. The width of the second sealing ring can be, but is not limited to, 5mm, 8mm, 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 28mm, and 30mm.

[0054] In the embodiment of the present application, the arrangement of the air absorption layer can be selected according to actual production needs. Specifically, the single-side surface of the bipolar electrode and the orthographic projection of the dressing layer on the current collector are rectangular as an example for explanation:

[0055] Please also see Figure 3 as well as Figures 4A-4C, The gas absorption layer can be disposed only on one side of the dressing layer, or can be separately disposed on both sides of the dressing layer, or can surround three sides of the dressing layer, or can be disposed around the periphery of the dressing layer. When the gas absorption layers are separately disposed on both sides of the dressing layer, they can be separately disposed on the opposite sides of the long side of the dressing layer, or can be separately disposed on the opposite sides of the short side of the dressing layer, or can be respectively located on one side of the adjacent long side and one side of the short side of the dressing layer. Those skilled in the art can make a choice according to the coating difficulty, the symmetry requirement of the electrode, the shape of the electrode, and considering the subsequent assembly difficulty.

[0056] Considering the process accuracy during the preparation of the bipolar electrode, in the embodiments of the present application, the gas absorption layer can be adjacent to the dressing layer, or there can be a certain gap between the gas absorption layer and the dressing layer. However, in order to make full use of the space and ensure a relatively high energy density of the final battery, it is recommended that the gap width between the gas absorption layer and the dressing layer ≤ 1 mm.

[0057] For the convenience of description, the first direction is defined as the direction from the dressing layer to the gas absorption layer, and the second direction is perpendicular to the above-mentioned first direction. Taking Figure 3 as an example, the dimension L1 of the gas absorption layer in the second direction can be equal to the dimension L2 of the dressing layer in the second direction (L1 = L2), or L1 < L2, or L1 > L2. The embodiments of the present application do not limit this.

[0058] Considering that there are various arrangement modes of the gas absorption layer on the current collector, for different arrangement modes, the difference in the dimension of the gas absorption layer in the first direction may be relatively large. In addition, the gas absorption layer mainly relies on the porous material to adsorb the gas generated during the formation and cycling of the battery, and the dimension parameters of the gas absorption layer are also related to the single-sided surface density of the gas absorption layer and the mass ratio of the porous material in the gas absorption layer. In some embodiments of the present application, the total gas absorption amount of the gas absorption layer in the bipolar electrode ≥ the estimated total gas generation amount during the charge and discharge process of the bipolar electrode. In some specific embodiments, the gas absorption amount of the material per unit mass of the gas absorption layer is α g, the estimated total gas generation amount during the charge and discharge process of the bipolar electrode is β g, and the single-sided surface density of the gas absorption layer is A g / m 2 , The sum of the surface areas of the gas absorption layers in the bipolar electrode is S m 2, the bipolar pole piece satisfies: S≥β / (A*α). It is understandable that when multiple bipolar pole pieces are assembled, although the positive electrode layer and the negative electrode layer in the same electrochemical unit belong to different bipolar pole pieces, the parameters of the multiple bipolar pole pieces are consistent. Therefore, it is appropriate and reasonable to measure the parameters of the air absorption layer by the estimated gas production of a single bipolar pole piece during the charge and discharge process. It is understandable that the estimated total gas production β of the electrochemical unit during the charge and discharge process is related to the size of the dressing layer, the compaction density of the active material in the dressing layer, and the final electrolyte formula used, but these are parameters well known to technicians in the field and can be selected according to the final use needs. In some embodiments of the present application, 0.01≤β≤0.6.

[0059] Specifically, when only one side of the bipolar pole piece has an air absorption layer, and the air absorption layer is located only on one side of the dressing layer, the above formula can be directly substituted. It can be understood that when the two opposite surfaces of the bipolar pole piece have air absorption layers, the single-sided surface density of the air absorption layers on the two opposite surfaces is generally equal. Therefore, in this case, S is the sum of the surface areas of the air absorption layers on the two opposite surfaces of the bipolar pole piece. It should also be noted that when one side of the bipolar pole piece is on opposite sides of the dressing layer, it can be regarded as having two air absorption layers on one side of the bipolar pole piece. In this case, S is the sum of the surface areas of the two air absorption layers, and the sizes of the two air absorption layers can be the same or different.

[0060] When encountering some special cases, those skilled in the art can adapt the above formulas and principles to determine the parameters of the getter layer. For example, when the two opposite surfaces of the bipolar pole piece have a first getter layer and a second getter layer, the single-sided surface density of the first getter layer is A1 g / m 2 , the surface area is S1 m 2 The single-surface density of the second air-absorbing layer is A2 g / m 2 , the surface area is S2m 2 , then the bipolar pole piece satisfies:

[0061] If there are other special cases, for example, different α values ​​for multiple getter layers, those skilled in the art can adapt them according to the above principles, which are all within the scope of the embodiments of this application and will not be described in detail here.

[0062] In the following example, a bipolar pole piece having an air-intake layer on only one surface side, the air-intake layer being located only on one side of the dressing layer, and the dimension L1 of the air-intake layer in the second direction being equal to the dimension L2 of the dressing layer in the second direction, then the dimension L1' of the air-intake layer in the first direction satisfies: L1' ≥ β / (A*α*L1).

[0063] It is understandable that during the preparation of the electrode, it is generally necessary to roll-press the current collector coated with the dressing layer. In some embodiments of the present application, it is also necessary to roll-press the current collector coated with the dressing layer and the air absorption layer. In the embodiment of the present application, the thickness of the air absorption layer can be the same as the thickness of the dressing layer, that is, the surface of the dressing layer facing away from the current collector is flush with the surface of the air absorption layer facing away from the current collector; or, the thickness of the air absorption layer can be less than the thickness of the dressing layer, that is, the surface of the dressing layer facing away from the current collector is higher than the surface of the air absorption layer facing away from the current collector. In this way, the problem of excessive gravitational force damaging the current collector during the rolling process due to the thick air absorption layer can be avoided. In addition, when the above-mentioned bipolar electrode is applied to a bipolar battery, the surfaces of the dressing layer and the air absorption layer are generally provided with a diaphragm. The thickness of the air absorption layer is less than or equal to the thickness of the dressing layer, which also facilitates the diffusion of gas production into the air absorption layer and facilitates the rapid absorption of gas production.

[0064] In order to improve the structural stability of the air absorption layer and its interfacial bonding strength with the current collector, in some embodiments of the present application, the air absorption layer also includes a binder. Furthermore, in order to take into account the air absorption capacity and structural stability of the air absorption layer, in some specific embodiments of the present application, the mass proportion of the porous material in the air absorption layer is 80%-99%. In the embodiments of the present application, the above-mentioned binder can be any binder suitable for the positive electrode or negative electrode in the field. Furthermore, when the air absorption layer is coplanar with the positive electrode material layer, the binder is preferably selected from the binder suitable for the positive electrode; when the air absorption layer is coplanar with the negative electrode material layer, the binder is preferably selected from the binder suitable for the negative electrode. In other embodiments, the air absorption layer is also dispersed with a material that disperses the electrolyte, which is more conducive to the absorption of gas production and more conducive to the concentration of the electrolyte in the dressing layer area.

[0065] In some embodiments of the present application, the specific surface area of ​​the porous material is ≥200m 2 In some specific embodiments, the specific surface area of ​​the porous material is ≥1000 m 2 / g. This is beneficial to improve the air absorption capacity of the air absorption layer. Specifically, the specific surface area of ​​the porous material can be but is not limited to 200m 2 / g、500m 2 / g、800m 2 / g、1000m 2 / g、1200m 2 / g、1500m 2 / g、1800m 2 / g、2000m 2 / g、2200m 2 / g、2500m 2 / g、2800m 2 / g、3000m 2 / g、3200m 2 / g、3500m 2 In the embodiments of the present application, the specific surface area of ​​the porous material is the BET specific surface area, which can be measured by gas adsorption-desorption test.

[0066] In some embodiments of the present application, the porous material includes at least one of modified or unmodified activated carbon, modified or unmodified transition metal oxide materials, modified or unmodified graphene, and modified or unmodified metal-organic framework materials. These materials have a relatively rich pore structure and have good adsorption properties for gases (including hydrogen, methane, propylene, ethylene, etc.) generated during the battery's charge and discharge processes. In some specific embodiments, the porous material is selected from activated carbon.

[0067] In the embodiments of the present application, the current collector can be any current collector known in the art and suitable for bipolar pole pieces. For example, the current collector can be a copper foil-aluminum foil composite current collector, which is not limited in the present application.

[0068] It is understood that the dressing layer in the embodiments of the present application includes a positive electrode material layer and a negative electrode material layer. The embodiments of the present application do not impose any restrictions on the positive electrode material layer and the negative electrode material layer, and any positive electrode material layer and negative electrode material layer known in the art can be used. The positive electrode material layer and the negative electrode material layer can be a positive electrode material layer and a negative electrode material layer suitable for lithium-ion batteries, or a positive electrode material layer and a negative electrode material layer suitable for other alkali metal ion batteries such as sodium-ion batteries.

[0069] Specifically, the positive electrode material layer generally includes a positive electrode active material, a conductive agent and a binder. The above materials can be selected from any material known in the art. For example, taking the positive electrode for lithium-ion batteries as an example, the positive electrode active materials include but are not limited to nickel-cobalt-manganese ternary materials, lithium iron phosphate, lithium cobalt oxide, lithium manganate, etc. Conductive agents include but are not limited to graphene, carbon black, carbon nanotubes, carbon microspheres, etc. Binders include but are not limited to polyvinylidene fluoride (PVDF), polyvinyl pyrrolidone (PVP), etc. The positive electrode material layer may also include a dispersant, for example, sodium carboxymethyl cellulose (CMC), etc.

[0070] In some specific embodiments, the positive electrode active material is selected from nickel-cobalt-manganese ternary material, the conductive agent is selected from carbon black, and the binder is PVDF.

[0071] Specifically, the negative electrode material layer generally includes a positive electrode active material, a conductive agent and a binder. The above materials can be selected from any material known in the art. For example, taking the negative electrode for lithium-ion batteries as an example, the negative electrode active material includes but is not limited to graphite, silicon element, silicon alloy, silicon-carbon composite material, lithium metal, etc. The conductive agent includes but is not limited to graphene, carbon black, carbon nanotubes, carbon microspheres, etc. The binder includes but is not limited to polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), etc. The negative electrode material layer may also include a dispersant, for example, CMC, etc.

[0072] In some specific embodiments, the positive electrode active material is selected from graphite, the conductive agent is selected from carbon black, and the binder is SBR.

[0073] In the embodiment of the present application, the dressing layer can be prepared by a wet method.

[0074] An embodiment of the present application also provides a bipolar battery, comprising a plurality of bipolar pole pieces provided in the embodiment of the present application, wherein the plurality of bipolar pole pieces are stacked; a first pole piece and a second pole piece are defined as any two adjacent ones of the plurality of bipolar pole pieces; wherein a diaphragm and an electrolyte are further provided between the first pole piece and the second pole piece; a sealing ring on a side surface of the first pole piece facing the second pole piece and a sealing ring on a side surface of the second pole piece facing the first pole piece form a sealed receiving space, and the receiving space has at least one of the air absorption layers.

[0075] For details, see Figure 5 , Figure 5 This is a schematic structural diagram of a cross section of an electrochemical unit in a bipolar battery according to an embodiment of the present application, wherein the number, position, and size of the dressing layer and the air-absorbing layer are for illustrative purposes only. Figure 5 The diaphragm is not shown. Due to the use of the bipolar pole piece provided in the embodiment of the present application, each electrochemical unit of the battery cell has an air absorption layer that can absorb the gas produced by the electrode, and there is no need to exhaust and reseal the electrochemical unit after formation, and each electrochemical unit is independent of each other and can operate independently. The above-mentioned battery cell can have good cycle performance and has a good market prospect. It can be understood that in the same electrochemical unit, the electrode polarity of the dressing layer of the first pole piece and the dressing layer of the second pole piece are different, one is a positive electrode material layer and the other is a negative electrode material layer.

[0076] In some embodiments of the present application, the battery may also contain other bipolar pole pieces. Other bipolar pole pieces refer to bipolar pole pieces that do not contain an air absorption layer. It is sufficient to ensure that each electrochemical unit has an air absorption layer and the air absorption capacity of the air absorption layer can achieve the expected effect.

[0077] It is understood that a bipolar battery also contains two unipolar pole pieces, which are located at opposite ends of a stack of multiple bipolar pole pieces. One unipolar pole piece is a negative pole piece, and the other is a positive pole piece. The unipolar pole pieces can be any positive or negative pole piece known in the art. It should also be noted that if a unipolar pole piece and its adjacent bipolar pole piece also form a closed electrochemical unit, the electrochemical unit should also have at least one air absorption layer.

[0078] In some embodiments of the present application, when assembling multiple bipolar pole pieces to prepare a bipolar battery, the following steps may be included:

[0079] The material of the first sealing layer in the first sealing ring part of the first pole piece is filled with the material of the second sealing layer in the second sealing ring part of the first pole piece, and the second pole piece is covered so that the MPP solid film material is also located in the first sealing ring part of the second pole piece and in the second sealing ring part of the second pole piece; then a frame-type welding head is used to hot-press the first sealing ring part of the first pole piece and the second sealing ring part of the second pole piece in sequence, and the three sides of the first sealing ring part and the second sealing ring part are sealed, leaving one side as the liquid injection port, injecting the electrolyte, and then using a straight-line hot pressing welding head to weld the first sealing ring part and the unsealed side of the second sealing ring part.

[0080] In some specific embodiments of the present application, the conditions for sequentially hot-pressing the first sealing ring portion of the first and second electrode pieces using a frame-type welding head are: hot pressing at a pressure of 50 kg to 1000 kg and 50° C. to 200° C. for 3 seconds to 10 seconds. The conditions for sequentially hot-pressing the second sealing ring portion of the first and second electrode pieces using a frame-type welding head are: hot pressing at a pressure of 50 kg to 1000 kg and 50° C. to 200° C. for 3 seconds to 10 seconds.

[0081] In some specific embodiments of the present application, after injecting the electrolyte, a parallel restraint method is used to weld the unsealed side of the first and second sealing ring portions using a straight hot press welding head. The welding conditions for the first sealing ring portion are: hot pressing at a pressure of 50-1000 kg and a temperature of 50-200°C for 3-10 seconds. The welding conditions for the second sealing ring portion are: hot pressing at a pressure of 50-1000 kg and a temperature of 50-200°C for 3-10 seconds.

[0082] In other embodiments, the material of the second sealing layer is selected from materials that can undergo room temperature self-polymerization, such as epoxy resin.

[0083] It can be understood that the diaphragm is used to prevent short circuits caused by direct contact between the active material layers of the positive and negative electrodes. Therefore, in some embodiments of the present application, in the same electrochemical unit, a diaphragm is provided on the surface of both the dressing layer and the air absorption layer. In some embodiments of the present application, in the electrochemical unit composed of the first electrode and the second electrode, the maximum thickness of the sealing ring (herein, including the sealing ring on one side of the first electrode and the sealing ring on one side of the second electrode) is equal to the sum of the thicknesses of the dressing layer of the first electrode, the dressing layer of the second electrode, and the diaphragm.

[0084] In other embodiments, the sealing area of ​​the bipolar pole piece includes a first sealing ring portion and a second sealing ring portion. In this case, the diaphragm can extend to the first sealing ring portion, and the diaphragm is fixed by the first sealing ring of the bipolar pole piece.

[0085] In the embodiment of the present application, the diaphragm can be any diaphragm known in the art that is suitable for bipolar battery cells.

[0086] In some embodiments of the present application, the electrolyte is a liquid electrolyte and / or a gel electrolyte. In some specific embodiments, the electrolyte is a gel electrolyte.

[0087] It is understandable that although the use of a solid electrolyte does not require sealing of the electrochemical unit, if desired by those skilled in the art, the electrolyte may also be a solid electrolyte.

[0088] In the embodiment of the present application, the above-mentioned liquid electrolyte can be any liquid electrolyte known in the art. Generally, the liquid electrolyte includes an electrolyte salt, a solvent and an additive. Taking the liquid electrolyte for lithium-ion batteries as an example, the electrolyte salt includes but is not limited to LiPF6, LiDFOB, LiFSI, LiTFSI, etc. The solvent includes but is not limited to at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, etc. The additive includes but is not limited to at least one of vinylene carbonate (VC), trimethylsilyl phosphate (TMSP), LiFSI, LiTFSI, LiPO2F2, etc.

[0089] In the embodiments of the present application, the gel electrolyte can be any known gel electrolyte in the art. For example, the gel electrolyte includes a polymer monomer, an initiator, and a liquid electrolyte, wherein the polymer monomer includes at least one of 1,3-dioxolane, 1,4-dioxane, polyethylene glycol acrylate, ethoxylated trimethylolpropane triacrylate, and pentaerythritol tetraacrylate; and the initiator includes at least one of 2,2-azobisisobutyronitrile, dibenzoyl peroxide, an α-hydroxyketone derivative, and a benzoin ether.

[0090] The present invention also provides an electric device including the bipolar battery provided in the present invention. The bipolar battery provided in the present invention provides power to the electric device, thereby making the electric device more competitive in the market.

[0091] The technical solution of this application is further illustrated below with multiple embodiments.

[0092] Example 1

[0093] The bipolar pole piece includes a current collector (specifically an aluminum foil-copper foil composite current collector) and dressing layers arranged on opposite sides of the current collector, one of which is a positive electrode material layer arranged on the surface of the aluminum foil; the other is a negative electrode material layer arranged on the surface of the copper foil.

[0094] The length and width of the positive electrode material layer are 14.0 cm and 10.0 cm respectively, and the single-sided density is 200 g / cm 2 The length and width of the negative electrode material layer are 14.1 cm and 10.1 cm respectively, and the single-sided surface density is 100 g / cm 2 ; Among them, the distance between any side edge of the negative electrode material layer and the current collector is 12 mm, and the positive projection of the positive electrode material layer falls into the negative electrode material layer.

[0095] The positive electrode material layer is composed of a positive electrode active material (specifically lithium iron phosphate), a conductive agent (specifically carbon black), and a binder (specifically PVDF) in a mass ratio of 98:1:1; the negative electrode material layer is composed of a negative electrode active material (specifically graphite), a conductive agent (specifically carbon black), a binder (specifically PVDF), and a dispersant (specifically CMC) in a mass ratio of 97:2:0.5:0.5.

[0096] An air absorption layer is provided on one side of the positive electrode material layer. Each 1g of the material in the air absorption layer can absorb 1g of battery gas. The single-sided surface density of the air absorption layer is 300g / m 2 The thickness of the positive electrode absorption layer is the same as that of the positive electrode dressing area, which is 100 μm. The gas production during the life cycle of the bipolar unit is 0.15 g, so β / (A*α)=0.15 / (300*1)=0.0005m 2 The size of the side of the absorption layer adjacent to the positive electrode material layer is 10.0 cm, and the short side size is 5 mm.

[0097] The surface of the current collector not covered by the dressing layer and the getter layer is the sealing zone. The sealing zone is provided with a first sealing ring and a second sealing ring. The first sealing ring is 5 mm wide, and the second sealing ring is 5 mm wide. The first sealing ring is made of a low-melting-point MPP solid film material, while the second sealing ring is made of a high-melting-point MPP solid film material.

[0098] Example 2

[0099] The difference between Example 2 and Example 1 is that the adsorption layer is respectively arranged on the side adjacent to the positive electrode material layer and the side adjacent to the negative electrode material layer.

[0100] The bipolar pole piece includes a current collector (specifically an aluminum foil-copper foil composite current collector) and dressing layers arranged on opposite sides of the current collector, one of which is a positive electrode material layer arranged on the surface of the aluminum foil; the other is a negative electrode material layer arranged on the surface of the copper foil.

[0101] The length and width of the positive electrode material layer are 14.0 cm and 10.0 cm respectively, and the single-sided density is 200 g / cm 2 The length and width of the negative electrode material layer are 14.1 cm and 10.1 cm respectively, and the single-sided surface density is 100 g / cm 2 ; Among them, the distance between any side edge of the negative electrode material layer and the current collector is 12 mm, and the positive projection of the positive electrode material layer falls into the negative electrode material layer.

[0102] The positive electrode material layer is composed of a positive electrode active material (specifically lithium iron phosphate), a conductive agent (specifically carbon black), and a binder (specifically PVDF) in a mass ratio of 98:1:1; the negative electrode material layer is composed of a negative electrode active material (specifically graphite), a conductive agent (specifically carbon black), a binder (specifically PVDF), and a dispersant (specifically CMC) in a mass ratio of 97:2:0.5:0.5.

[0103] An air absorption layer is provided on one side of the short side of the positive electrode material layer and the negative electrode material layer. Each 1g of the air absorption layer material can absorb 1g of battery gas. The single-sided surface density of the air absorption layer is 300g / m 2 The thickness of the positive electrode absorption layer is the same as that of the positive electrode dressing area, which is 100 μm. The thickness of the negative electrode absorption layer is the same as that of the negative electrode dressing area, which is 80 μm. The gas production during the life cycle of the bipolar unit is 0.15 g. Then β / (A*α)=0.15 / (300*1)=0.0005m 2 The size of the side of the air-absorbing layer adjacent to the positive electrode material layer is 10.0 cm, the size of the side of the air-absorbing layer adjacent to the negative electrode material layer is 10.1 cm, and the short side dimensions of the two air-absorbing layers are both 2.5 mm.

[0104] The surface of the current collector not covered by the dressing layer and the getter layer is the sealing zone. The sealing zone is provided with a first sealing ring and a second sealing ring. The first sealing ring is 5 mm wide, and the second sealing ring is 5 mm wide. The first sealing ring is made of a low-melting-point MPP solid film material, while the second sealing ring is made of a high-melting-point MPP solid film material.

[0105] Example 3

[0106] The difference between Example 3 and Example 2 is that the size of the side of the air absorption layer adjacent to the positive electrode material layer is 6.0 cm, the size of the side of the air absorption layer adjacent to the negative electrode material layer is 10.1 cm, the short side size of the two air absorption layers is 2.5 mm, and the adsorption layer area S is less than 0.0005 m 2 .

[0107] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0108] Comparative Example 1

[0109] The only difference from Example 1 is that the bipolar pole piece does not contain a getter layer.

[0110] Performance Testing

[0111] Preparation of an electrochemical cell sealing structure including the bipolar pole pieces of Examples 1 to 3 and Comparative Example 1:

[0112] Take a bipolar pole piece of Example 1-Example 3 (Comparative Example 1), cover it with another identical bipolar pole piece, and use a frame-shaped welding head to hot press the first sealing ring part, and the process conditions are: hot pressing at 60°C for 5s and a pressure of 900kg; then use a frame-shaped welding head to hot press the second sealing ring part, and the process conditions are: hot pressing at 180°C for 5s and a pressure of 900kg; inject 1.5g of electrolyte from the temporarily unsealed side, and use a parallel restraint method. Use a straight-line hot pressing welding head to weld, first applying hot pressing at 60°C for 5s and a pressure of 900kg to seal the first sealing ring part, and then use hot pressing at 180°C for 5s and a pressure of 900kg to seal the second sealing ring part.

[0113] After assembly, the exposed dressing layer, the air-absorbing layer, the first sealing layer, and the second sealing layer were removed. The samples were then sealed with aluminum-plastic film for final sealing. The positive and negative electrode tabs (aluminum for the positive electrode tab and nickel for the negative electrode tab) were welded to the positive and negative electrode current collectors, respectively. The vacuum seal was performed at a pressure of -90 kPa. Eight test battery groups were prepared for each of Examples 1 to 3 and Comparative Example 1, designated S11-S18 (Example 1), S21-S28 (Example 2), S31-S38 (Example 3), and DS11-DS18 (Comparative Example 1).

[0114] Leakage test

[0115] Some of the example batteries and comparative example batteries described above were respectively inserted into a sealing device with a gas leakage detection device and placed in a gas detection electrode. They were then placed in an oven at 45°C (S11-S12, S21-S22, S31-S32, DS11-DS12), 60°C (S13-S14, S23-S24, S33-S34, DS13-DS14), and 80°C (S15-S16, S25-S26, S35-S36, DS15-DS16) for 1 month, 2 months, 3 months, 4 months, 5 months, and 6 months, respectively. Accelerated life tests were performed to record the time when liquid vapor was detected by the dedicated gas detection electrode. The results are summarized in Table 1, where √ indicates that the test passed and X indicates that the test failed.

[0116] Gas absorption test

[0117] The oil bath method was used to test the gas volume generated after 100, 500 and 1000 cycles respectively.

[0118] The test conditions of the oil bath method are as follows: immerse S17-S18, S27-S28, S37-S38 and DS17-DS18 in silicone oil, maintain a constant temperature of 25°C for 2 hours, weigh them, and record the data m0; after 100 cycles, weigh the weight as m1; after 500 cycles, weigh the weight as m2; after 1000 cycles, weigh the weight as m3, and calculate the difference m respectively. (0-1) , m (0-2) , m (0-3) The results are summarized in Table 2. The battery composition is the same, and the gas production of the embodiment battery and the comparative example battery during the battery charge and discharge cycle is equal. However, since the comparative example battery does not have an air absorption layer, the gas produced by the battery is all free in the battery, causing the battery to bulge, thereby increasing the buoyancy of the battery. At this time, m (0-1) , m (0-2) , m (0-3) It reflects the weight change caused by buoyancy, so m (0-1) , m (0-2) , m (0-3) The larger the value, the greater the amount of free gas in the battery.

[0119] Table 1

[0120]

[0121] Table 2

[0122] <![CDATA[m0]]> <![CDATA[m1]]> <![CDATA[m2]]> <![CDATA[m3]]> <![CDATA[m (0-1) ]]> <![CDATA[m (0-2) ]]> <![CDATA[m (0-3) ]]> S17 10.1 10.09 10.07 10.05 0.01 0.03 0.05 S18 10.15 10.13 10.12 10.1 0.02 0.03 0.05 S27 10.05 10.02 9.98 9.92 0.03 0.07 0.13 S28 10.01 9.99 9.95 9.9 0.02 0.06 0.11 S37 10.01 9.85 9.79 9.76 0.16 0.22 0.25 S38 10.02 9.83 9.78 9.75 0.19 0.24 0.27 DS17 9.95 9.55 9.46 9.4 0.4 0.49 0.55 DS18 10.11 9.7 9.6 9.54 0.41 0.51 0.57

[0123] Combining the data in Table 1 and Table 2, it can be seen that the bipolar pole piece provided in the embodiment of the present application can achieve good sealing performance, and the air absorption layer can effectively reduce the gas production of the electrochemical unit.

[0124] Comparing the data for the example battery and the comparative example battery in Table 2 shows that the gas absorption layer can effectively absorb the gases generated during the battery's charge and discharge cycles. Furthermore, when the surface area S of the gas absorption layer is within the range further recommended in this application, the gas absorption effect of the gas absorption layer is significantly improved.

[0125] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A bipolar pole piece, characterized in that: It comprises a current collector and dressing layers arranged on two opposite sides of the current collector, wherein the electrode polarities of the two dressing layers are different; An air absorption layer is also provided on at least one side surface of the current collector, and the air absorption layer and the dressing layer are both in direct contact with the current collector; the air absorption layer comprises a porous material; Sealing areas are arranged on the edges of the two opposite sides of the current collector, and the dressing layer and the air absorption layer are arranged in the accommodating space formed by the sealing areas.

2. The bipolar pole piece according to claim 1, characterized in that: The gas absorption amount per unit mass of the material of the getter layer is αg, The total gas production of the bipolar pole piece during the charge and discharge process is expected to be βg, and the single-sided surface density of the gas absorption layer is Ag / m 2 The sum of the surface areas of the air absorption layers in the bipolar pole piece is Sm 2 , The bipolar pole piece satisfies: S≥β / (A*α).

3. The bipolar pole piece according to claim 1 or 2, characterized in that: The thickness of the air-intake layer is less than or equal to the thickness of the dressing layer.

4. The bipolar pole piece according to claim 1, characterized in that: The specific surface area of ​​the porous material is ≥200m 2 / g.

5. The bipolar pole piece according to claim 1, characterized in that: The porous material includes at least one of modified or unmodified activated carbon, modified or unmodified transition metal oxide materials, modified or unmodified graphene and modified or unmodified metal organic framework materials.

6. The bipolar pole piece according to claim 1, characterized in that: A sealing ring is provided on the sealing area, and the outer edge of the sealing ring is flush with the outer edge of the current collector, or the sealing ring has an exposed portion relative to the current collector.

7. The bipolar pole piece according to claim 1, characterized in that: The sealing area comprises a first sealing ring portion and a second sealing ring portion, wherein the first sealing ring portion is arranged close to the dressing layer, and the second sealing ring portion is arranged on the periphery of the first sealing ring portion; a first sealing ring is arranged on the first sealing ring portion, and a second sealing ring is arranged on the second sealing ring portion; The compatibility of the material of the first sealing ring with the electrolyte is better than that of the material of the second sealing ring with the electrolyte, and / or the sealing performance of the second sealing ring is better than that of the first sealing ring.

8. The bipolar pole piece according to claim 7, characterized in that: The material of the first sealing ring and the material of the second sealing ring each independently include at least one of modified or unmodified polypropylene, modified or unmodified polyethylene, modified or unmodified epoxy resin, and modified or unmodified polyacrylate.

9. The bipolar pole piece according to claim 7 or 8, characterized in that: The widths of the first sealing ring portion and the second sealing ring portion are independently 5 mm to 30 mm.

10. A bipolar battery, characterized in that: Comprising a plurality of bipolar pole pieces according to any one of claims 1 to 9, wherein the plurality of bipolar pole pieces are stacked; The first pole piece and the second pole piece are defined as any two adjacent pole pieces among the plurality of bipolar pole pieces; wherein a diaphragm and an electrolyte are further provided between the first pole piece and the second pole piece; The sealing ring on the side surface of the first pole piece facing the second pole piece and the sealing ring on the side surface of the second pole piece facing the first pole piece form a sealed receiving space, and the receiving space has at least one air gettering layer.

11. An electrical device, characterized in that: Comprising the bipolar battery as claimed in claim 10.

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