Bipolar battery and preparation method thereof

Abstract

The embodiment of the invention relates to a bipolar battery. The bipolar battery comprises a plurality of battery units which are connected in series, each battery unit comprises two current collectors, and a negative plate, a diaphragm and a positive plate which are arranged between the two current collectors and are sequentially stacked; the negative plate abuts against one of the current collectors, and the positive plate abuts against the other current collector; and two adjacent battery units share one of the current collectors. The invention also provides a preparation method of the bipolar battery. According to the invention, the positive and negative pole pieces are prepared by a dry electrode preparation method, and the assembly mode is optimized, so that the single battery can be boosted in a multi-stage series connection mode through the internal pole pieces. According to the invention, the free setting of the voltage can be realized only by increasing the number of stacked layers according to the voltage requirement, the series connection efficiency is greatly improved, the internal resistance of the battery is effectively reduced, and the performance and consistency of the product are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a bipolar battery and a preparation method thereof. Background Art

[0002] With the development of science and technology, power batteries as an energy device have attracted more and more attention and have been widely used in mobile phones, electric vehicles, power tools, home energy storage and other fields.

[0003] At present, common lithium-ion battery structures include cylindrical, square or soft-pack. Among them, cylindrical batteries are generally assembled in a single string form; square batteries and soft-pack batteries are generally wound in a single string form or stacked in parallel to form a single cell. This internal single string form or stacked in parallel form structure has the problem of low cell voltage. In actual application, the above-mentioned low-voltage cells need to be connected in series to form a battery module to increase the output voltage in order to meet certain load voltage requirements. The series connection of the cells requires external welding to achieve series connection, and a management system is also required for module control. The operation is cumbersome and the cost is high, which makes it difficult to meet the needs of actual applications. Summary of the invention

[0004] Based on this, the present invention provides a bipolar battery and a preparation method thereof, aiming to solve the problems of low voltage of single cells in the prior art, cumbersome series connection operation, the need for a management system for module control, and high cost.

[0005] To achieve the above-mentioned objectives, on the one hand, an embodiment of the present invention proposes the following technical solution: a bipolar battery, comprising a plurality of battery cells connected in series; each of the battery cells comprises two current collectors, and a negative electrode sheet, a separator and a positive electrode sheet arranged between the two current collectors and stacked in sequence; the negative electrode sheet is arranged in abutment with one of the current collectors, and the positive electrode sheet is arranged in abutment with the other current collector; two adjacent battery cells share one of the current collectors.

[0006] As a preferred embodiment, the thickness of the positive electrode sheet is 0.05 mm to 10.0 mm; the thickness of the negative electrode sheet is 0.05 mm to 10.0 mm.

[0007] As a preferred embodiment, each of the battery cells is a mutually isolated and sealed unit. Each battery cell forms a sealed unit, which can effectively avoid the occurrence of electrolyte cross-liquid.

[0008] As a preferred embodiment, the battery cell is a cylindrical battery cell or a square battery cell; when the battery cell is a cylindrical battery cell, the current collector, the negative electrode sheet, the separator and the positive electrode sheet are all configured in a circular shape.

[0009] As a preferred embodiment, the two current collectors have the same radius; the radius of the current collector is greater than the radius of the diaphragm; the radius of the diaphragm is greater than the radius of the negative electrode sheet; the radius of the negative electrode sheet is greater than the radius of the positive electrode sheet.

[0010] As a preferred embodiment, the current collector is one of a stainless steel current collector, a titanium alloy current collector or a nickel sheet current collector.

[0011] As a preferred embodiment, the positive electrode sheet is prepared from the following components by mass percentage: 80% to 98% positive electrode active material powder, 1% to 10% first binder powder and 0.5% to 10% first conductive agent powder;

[0012] The positive electrode active material powder is one or a mixture of at least two of lithium iron phosphate, ternary lithium compound, lithium manganate, sodium iron phosphate, sodium vanadium phosphate, sodium cobalt oxide, lithium ferrite or lithium nickelate;

[0013] The ternary lithium compound is one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide;

[0014] The first binder powder is one or a mixture of at least two of PTFE, PVDF, PEO or short fibers;

[0015] The first conductive agent powder is one or a mixture of at least two of conductive carbon black, carbon nanotubes, graphene or conductive graphite.

[0016] As a preferred embodiment, the positive electrode sheet is prepared by the following method: in an environment with a dew point temperature of ≤-30°C, 80% to 98% of positive electrode active material powder, 1% to 10% of a first binder powder and 0.5% to 10% of a first conductive agent powder are uniformly mixed and dispersed to obtain a mixed powder; the mixed powder is rolled and then die-cut to obtain a positive electrode sheet, the thickness of the positive electrode sheet is 0.05mm to 10.0mm.

[0017] As a preferred embodiment, the dispersion temperature is 50° C. to 180° C., and the dispersion line speed is 10 m / s to 30 m / s.

[0018] The temperature of the roller pressing is 80° C. to 200° C.; the pressure of the roller pressing is 10T to 500T.

[0019] As a preferred embodiment, the negative electrode sheet is prepared from the following components by mass percentage: 80% to 98% negative electrode active material powder, 1% to 10% second binder powder and 0.5% to 10% second conductive agent powder;

[0020] The negative electrode active material powder is one or a mixture of at least two of graphite, lithium titanate or silicon negative electrode;

[0021] The graphite is hard carbon or soft carbon;

[0022] The second binder powder is one or a mixture of at least two of PTFE, PVDF, PEO or short fibers;

[0023] The second conductive agent powder is one or a mixture of at least two of conductive carbon black, carbon nanotubes, graphene or conductive graphite.

[0024] As a preferred embodiment, the negative electrode sheet is prepared by the following method: in an environment with a dew point temperature of ≤-30°C, 80% to 98% of negative electrode active material powder, 1% to 10% of a second binder powder and 0.5% to 10% of a second conductive agent powder are uniformly mixed and dispersed to obtain a mixed powder; the mixed powder is rolled and then die-cut to obtain a negative electrode sheet, and the thickness of the negative electrode sheet is 0.05mm to 10.0mm.

[0025] As a preferred embodiment, the dispersion temperature is 50° C. to 180° C., and the dispersion line speed is 10 m / s to 30 m / s. This is beneficial to the fiberization of the second binder powder and can evenly disperse the powders.

[0026] The temperature of the roller pressing is 80° C. to 200° C.; the pressure of the roller pressing is 10T to 500T.

[0027] As a preferred embodiment, the bipolar battery is a lithium ion battery, a sodium ion battery or a zinc ion battery.

[0028] On the other hand, an embodiment of the present application also provides a method for preparing the bipolar battery, comprising the following steps: in an environment with a dew point temperature ≤-30°C, stacking two current collectors, a negative electrode sheet, a separator and a positive electrode sheet in the order of current collector, negative electrode sheet, separator, positive electrode sheet, current collector to obtain a battery unit; connecting a plurality of the battery units in series to obtain a bipolar battery.

[0029] The beneficial effects achieved by the present invention are:

[0030] (1) The present application changes the internal parallel or single string structure of the existing battery, prepares the positive and negative electrodes by a dry electrode preparation method, and optimizes the assembly method so that two adjacent battery cells are isolated by only one current collector and are completely sealed, thereby allowing the single battery to be boosted by a multi-stage series connection through the internal electrode, which can effectively solve the problem of low voltage of the single battery.

[0031] (2) Compared with traditional batteries, the bipolar battery of the present application can remove solvents (NMP, deionized water, etc.), thickeners (CMC, etc.), copper foil, aluminum foil and other raw materials at the raw material end, greatly reducing solvent recovery and avoiding environmental pollution, while effectively reducing the cost of the battery cell. In terms of voltage, the bipolar battery of the present application can freely set the voltage according to voltage requirements by simply increasing the number of stacking layers; at the same time, because there is no need to use external switching accessories of traditional single cells, the series efficiency can be greatly improved, the internal resistance of the battery is effectively reduced, and the performance and consistency of the product are improved. In terms of capacity, the bipolar battery of the present application adopts a dry electrode preparation method to increase the electrode thickness of the traditional battery from the micron level to the millimeter level electrode thickness of the present application, which can ensure a higher energy density.

[0032] (3) Compared with the preparation process of traditional batteries, the bipolar battery of the present application can save coating machines, ultrasonic welding machines, laser welding machines, coating machines, shelling machines, baking machines and other equipment on the equipment side, which can effectively reduce the investment in equipment; in terms of process flow, it can save coating, ultrasonic welding, laser welding, coating, baking, assembly and other processes, which can effectively shorten the delivery cycle and effectively improve the production efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0034] Figure 1 Schematic diagram of the overall structure of a bipolar battery according to an embodiment of the present invention;

[0035] Figure 2 for Figure 1 Schematic diagram of the exploded structure of a bipolar battery;

[0036] Figure 3 for Figure 1 Schematic diagram of the cross-sectional structure of a bipolar battery.

[0037] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, top, bottom...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0040] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0042] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0043] In the prior art, there are high-voltage single cells that are constructed by horizontal series connection, which requires additional materials to form different sealed cavities, and in principle is still the series connection method of traditional single cells. The existing battery structure that adopts the soft-pack method and realizes horizontal series connection inside the battery through connecting sheets still needs to use connecting sheets in series, and occupies a large area, has a long sealing dimension, has high limitations in series connection, and is costly. The traditional battery structure that adopts wet coating of the rear electrode has high restrictions on compaction density and energy density, cannot meet the needs of higher energy density, and is difficult to promote in batches. Based on this, the present application provides a bipolar battery and a preparation method thereof to solve the above-mentioned technical problems.

[0044] Specifically, on the one hand, Figures 1 to 3 As shown, an embodiment of the present invention proposes the following technical solution: a bipolar battery, comprising a plurality of battery cells 10 connected in series; each of the battery cells 10 comprises two current collectors 11, and a negative electrode sheet 12, a separator 13 and a positive electrode sheet 14 which are arranged between the two current collectors 11 and stacked in sequence; the negative electrode sheet 12 is arranged in abutment with one of the current collectors 11, and the positive electrode sheet 14 is arranged in abutment with the other current collector 11; two adjacent battery cells 10 share one of the current collectors 11.

[0045] like Figures 2 to 3 As shown, in this embodiment, there are two battery cells 10 connected in series. It is understandable that in other embodiments, according to actual use needs, the number of battery cells 10 connected in series can also be set to 3, or 4, or 10, or 15 or even more.

[0046] As a preferred embodiment, the thickness of the positive electrode sheet 14 is 0.05 mm to 10.0 mm (depending on the actual use needs, it can be 0.05 mm, or 0.1 mm, or 3.0 mm, or 6.0 mm, or 10.0 mm); the thickness of the negative electrode sheet 12 is 0.05 mm to 10.0 mm (depending on the actual use needs, it can be 0.05 mm, or 0.1 mm, or 3.0 mm, or 6.0 mm, or 10.0 mm).

[0047] As a preferred embodiment, each of the battery cells 10 is a mutually isolated and sealed unit. Each battery cell forms a sealed unit, which can effectively avoid the occurrence of electrolyte cross-liquid.

[0048] As a preferred embodiment, the battery cell 10 is a cylindrical battery cell or a square battery cell; when the battery cell 10 is a cylindrical battery cell, the two current collectors 11, the negative electrode sheet 12, the separator 13 and the positive electrode sheet 14 are all arranged in a circular shape. Figures 1 to 3As shown, taking a cylindrical battery cell as an example, when two current collectors 11, the negative electrode sheet 12, the separator 13 and the positive electrode sheet 14 are stacked to form a battery cell, the centers of the two current collectors 11, the negative electrode sheet 12, the separator 13 and the positive electrode sheet 14 are on the same vertical line, and the vertical line is perpendicular to the center of the circle. It can be understood that in other embodiments, the battery cell 10 can also adopt a square battery cell.

[0049] As a preferred embodiment, the two current collectors 11 have the same radius; the radius of the current collector 11 is greater than the radius of the diaphragm 13; the radius of the diaphragm 13 is greater than the radius of the negative electrode sheet 12; the radius of the negative electrode sheet 12 is greater than the radius of the positive electrode sheet 14.

[0050] As a preferred embodiment, the current collector 11 is a stainless steel current collector, a titanium alloy current collector or a nickel sheet current collector.

[0051] As a preferred embodiment, the positive electrode sheet 14 is prepared from the following components by mass percentage: 80% to 98% (depending on the actual use requirements, it can be 80%, or 82%, or 85%, or 90%, or 98%) of positive electrode active material powder, 1% to 10% (depending on the actual use requirements, it can be 1%, or 3%, or 5%, or 8%, or 10%) of the first binder powder and 0.5% to 10% (depending on the actual use requirements, it can be 0.5%, or 3%, or 5%, or 8%, or 10%) of the first conductive agent powder;

[0052] The positive electrode active material powder is one or a mixture of at least two of lithium iron phosphate, ternary lithium compound, lithium manganate, sodium iron phosphate, sodium vanadium phosphate, sodium cobalt oxide, lithium ferrite or lithium nickelate;

[0053] The ternary lithium compound is one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide;

[0054] The first binder powder is one or a mixture of at least two of PTFE, PVDF, PEO or short fibers;

[0055] The first conductive agent powder is one or a mixture of at least two of conductive carbon black, carbon nanotubes, graphene or conductive graphite.

[0056] The moisture content of the positive electrode active material powder, the first binder powder and the first conductive agent powder is less than 400ppm. In this way, the first binder powder can be softened well, so that it can better play a bonding role, and can promote the release of stress in the pole piece during rolling, thereby improving the mechanical strength and stability of the electrode. If the moisture content of each powder is too high, it will affect the bonding effect of the binder, so that the mechanical strength and stability of the electrode will be reduced; if the moisture content of each powder is too low, it will affect the bonding effect of the binder and affect the release of stress in the pole piece. The specific components of each raw material powder of the positive electrode sheet can be selected according to the above range, and the present application scheme can be realized.

[0057] As a preferred embodiment, the positive electrode sheet 14 is prepared by the following method: in an environment with a dew point temperature ≤-30°C, 80% to 98% of positive electrode active material powder, 1% to 10% of a first binder powder and 0.5% to 10% of a first conductive agent powder are uniformly mixed and dispersed to obtain a mixed powder; the mixed powder is rolled and then die-cut to obtain a positive electrode sheet, the thickness of the positive electrode sheet is 0.05mm to 10.0mm.

[0058] As a preferred embodiment, the dispersion temperature is 50°C to 180°C (depending on the actual needs, it can be 50°C, or 80°C, or 90°C, or 150°C, or 180°C), and the dispersion linear speed is 10m / s to 30m / s (depending on the actual needs, it can be 10m / s, or 15m / s, or 20m / s, or 23m / s, or 26m / s, or 30m / s, etc.); in this way, it is beneficial to the fiberization of the first binder powder and can evenly disperse the powders.

[0059] The temperature of the rolling is 80°C to 200°C (depending on the actual use requirements, it can be 80°C, or 100°C, or 120°C, or 150°C, or 200°C); the pressure of the rolling is 10T to 500T (depending on the actual use requirements, it can be 10T, or 50T, or 200T, or 350T, or 500T, etc.). Rolling is generally performed by a roller press, a tablet press or an extruder; controlling the rolling temperature at 80°C to 200°C can better soften the first binder powder, so that it can better play a bonding role, and can promote the release of stress in the pole piece during the rolling process, thereby improving the mechanical strength and stability of the electrode.

[0060] As a preferred embodiment, the negative electrode sheet 12 is prepared from the following components by mass percentage: 80% to 98% (depending on the actual use requirements, it can be 80%, or 82%, or 85%, or 90%, or 98%) of negative electrode active material powder, 1% to 10% (depending on the actual use requirements, it can be 1%, or 3%, or 5%, or 8%, or 10%) of the second binder powder and 0.5% to 10% (depending on the actual use requirements, it can be 0.5%, or 3%, or 5%, or 8%, or 10%) of the second conductive agent powder;

[0061] The negative electrode active material powder is one or a mixture of at least two of graphite, lithium titanate or silicon negative electrode;

[0062] The graphite is hard carbon or soft carbon;

[0063] The second binder powder is one or a mixture of at least two of PTFE, PVDF, PEO or short fibers;

[0064] The second conductive agent powder is one or a mixture of at least two of conductive carbon black, carbon nanotubes, graphene or conductive graphite.

[0065] The moisture content of the negative electrode active material powder, the second binder powder and the second conductive agent powder is less than 400ppm. In this way, the second binder powder can be softened better, so that it can better play a bonding role, and can promote the release of stress in the pole piece during rolling, and improve the mechanical strength and stability of the electrode. If the moisture content of each powder is too high, it will affect the bonding effect of the binder, so that the mechanical strength and stability of the electrode are reduced; if the moisture content of each powder is too low, it will affect the bonding effect of the binder and affect the release of stress in the pole piece. The specific components of each raw material powder of the negative electrode sheet can be selected according to the above range, and the present application scheme can be realized.

[0066] As a preferred embodiment, the negative electrode sheet 12 is prepared by the following method: in an environment with a dew point temperature ≤-30°C, 80% to 98% of negative electrode active material powder, 1% to 10% of a second binder powder and 0.5% to 10% of a second conductive agent powder are uniformly mixed and dispersed to obtain a mixed powder; the mixed powder is rolled and then die-cut to obtain a negative electrode sheet, and the thickness of the negative electrode sheet is 0.05mm to 10.0mm.

[0067] The present application changes the internal parallel or single string structure of the existing battery, prepares the positive and negative electrodes by a dry electrode preparation method, and optimizes the assembly method so that two adjacent battery cells are isolated by only one current collector and are completely sealed, so that the single battery can be boosted by multi-stage series connection through the internal electrode, which can effectively solve the problem of low voltage of the single battery.

[0068] As a preferred embodiment, the dispersion temperature is 50°C to 180°C (depending on the actual needs, it can be 50°C, or 80°C, or 90°C, or 150°C, or 180°C), and the dispersion linear speed is 10m / s to 30m / s (depending on the actual needs, it can be 10m / s, or 15m / s, or 20m / s, or 23m / s, or 26m / s, or 30m / s, etc.); in this way, it is beneficial to the fiberization of the second binder powder and can evenly disperse the powders.

[0069] The temperature of the roller pressing is 80°C to 200°C (depending on the actual needs, it can be 80°C, 100°C, 120°C, 150°C, or 200°C); the pressure of the roller pressing is 10T to 500T (depending on the actual needs, it can be 10T, 50T, 200T, 350T, 500T, etc.).

[0070] Roll pressing is generally performed by a roller press, a tablet press or an extruder; controlling the rolling temperature at 80°C to 200°C can better soften the second binder powder, so that it can better play a bonding role, and can promote the release of stress in the electrode during the rolling process, thereby improving the mechanical strength and stability of the electrode.

[0071] As a preferred embodiment, the bipolar battery is a lithium ion battery, a sodium ion battery or a zinc ion battery.

[0072] The bipolar battery of the present application can remove raw materials such as solvents (NMP, deionized water, etc.), thickeners (CMC, etc.), copper foil, aluminum foil, etc. at the raw material end, which greatly reduces solvent recovery and can avoid environmental pollution, while effectively reducing the cost of the battery cell. In terms of voltage, the bipolar battery of the present application can freely set the voltage according to the voltage requirements by simply increasing the number of stacking layers; at the same time, because there is no need to use external switching accessories of traditional single cells, the series efficiency can be greatly improved, the internal resistance of the battery is effectively reduced, and the performance and consistency of the product are improved. In terms of capacity, the bipolar battery of the present application adopts a dry electrode preparation method to increase the electrode thickness of the traditional battery from the micron level to the millimeter level electrode thickness of the present application, which can ensure a higher energy density.

[0073] On the other hand, an embodiment of the present application also provides a method for preparing the bipolar battery, comprising the following steps: in an environment with a dew point temperature ≤-30°C, stacking two current collectors, a negative electrode sheet, a separator and a positive electrode sheet in the order of current collector, negative electrode sheet, separator, positive electrode sheet, current collector to obtain a battery unit; connecting a plurality of the battery units in series to obtain a bipolar battery.

[0074] In this way, the bipolar battery is assembled in series according to the current collector (total negative electrode), negative electrode sheet, separator, positive electrode sheet, current collector, negative electrode sheet, separator, positive electrode sheet, current collector, negative electrode sheet... separator, positive electrode sheet, current collector (total positive electrode). Two adjacent battery cells are isolated by only one current collector and are completely sealed, which can effectively ensure that there is no electrolyte cross-contamination between the battery cells.

[0075] Because the workshop environment controls the dew point temperature, the prepared bipolar battery can be directly injected, and then activated by electrolyte infiltration for 2h to 10h. After activation, the battery can be charged and activated for the first time using a high-voltage test cabinet. Because the formation process will produce gas and cause battery fluid loss, it is necessary to replenish the fluid to ensure that the battery has sufficient electrolyte. After the replenishment meets the standard, the sealing helium test is carried out, and then an aging is carried out to allow the activated battery cell electrode to be further infiltrated. Then high-voltage capacity separation is carried out to screen out batteries with standard capacity, and then secondary aging is carried out. The K value is calculated by the voltage drop value before and after aging, that is, (voltage after aging - voltage before aging) / aging time, and batteries with large self-discharge are screened out; finally, inspection and shipment are carried out according to customer requirements.

[0076] The dew point temperature of the present application is ≤-30°C. By controlling the dew point temperature, the ambient humidity can be less than 400ppm, which is consistent with the moisture content of the raw materials of the positive electrode sheet and the raw materials of the negative electrode sheet. The binder powder can be softened well to better play its bonding role, and can promote the release of stress in the electrode sheet during rolling, improve the mechanical strength and stability of the electrode, and meet the needs of the operation process of the present application.

[0077] The bipolar battery of the present application can save coating machines, ultrasonic welding machines, laser welding machines, coating machines, shelling machines, baking and other equipment on the equipment side, which can effectively reduce the investment in equipment; in terms of process flow, it can save coating, ultrasonic welding, laser welding, coating, baking, assembly and other processes, which can effectively shorten the delivery cycle and effectively improve the production efficiency of the battery.

[0078] In the description of this specification, the description with reference to the terms "an embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0079] In addition, it should be understood that although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0080] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A bipolar battery, characterized in that: It comprises a plurality of battery cells connected in series; each of the battery cells comprises two current collectors, and a negative electrode sheet, a separator and a positive electrode sheet which are arranged between the two current collectors and stacked in sequence; the negative electrode sheet is arranged in abutment with one of the current collectors, and the positive electrode sheet is arranged in abutment with the other current collector; two adjacent battery cells share one of the current collectors.

2. The bipolar battery according to claim 1, characterized in that: The thickness of the positive electrode sheet is 0.05 mm to 10.0 mm; the thickness of the negative electrode sheet is 0.05 mm to 10.0 mm; Each of the battery cells is a mutually isolated and sealed unit; The battery cell is a cylindrical battery cell or a square battery cell; when the battery cell is a cylindrical battery cell, the two current collectors, the negative electrode sheet, the separator and the positive electrode sheet are all arranged in a circular shape.

3. The bipolar battery according to claim 2, characterized in that: The two current collectors have the same radius; the radius of the current collector is greater than the radius of the diaphragm; the radius of the diaphragm is greater than the radius of the negative electrode sheet; the radius of the negative electrode sheet is greater than the radius of the positive electrode sheet; The current collector is one of a stainless steel current collector, a titanium alloy current collector or a nickel sheet current collector.

4. The bipolar battery according to claim 1, characterized in that: The positive electrode sheet is prepared from the following components by mass percentage: 80% to 98% positive electrode active material powder, 1% to 10% first binder powder and 0.5% to 10% first conductive agent powder; The positive electrode active material powder is one or a mixture of at least two of lithium iron phosphate, ternary lithium compound, lithium manganate, sodium iron phosphate, sodium vanadium phosphate, sodium cobalt oxide, lithium ferrite or lithium nickelate; The ternary lithium compound is one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide; The first binder powder is one or a mixture of at least two of PTFE, PVDF, PEO or short fibers; The first conductive agent powder is one or a mixture of at least two of conductive carbon black, carbon nanotubes, graphene or conductive graphite.

5. The bipolar battery according to claim 4, characterized in that: The positive electrode sheet is prepared by the following method: in an environment with a dew point temperature of ≤-30°C, 80% to 98% of positive electrode active material powder, 1% to 10% of first binder powder and 0.5% to 10% of first conductive agent powder are uniformly mixed and dispersed to obtain a mixed powder; the mixed powder is rolled and then die-cut to obtain a positive electrode sheet, wherein the thickness of the positive electrode sheet is 0.05 mm to 10.0 mm; The dispersion temperature is 50°C to 180°C, and the dispersion line speed is 10m / s to 30m / s; The temperature of the roller pressing is 80° C. to 200° C.; the pressure of the roller pressing is 10T to 500T.

6. The bipolar battery according to claim 1, characterized in that: The negative electrode sheet is prepared from the following components by mass percentage: 80% to 98% of negative electrode active material powder, 1% to 10% of second binder powder and 0.5% to 10% of second conductive agent powder; The negative electrode active material powder is one or a mixture of at least two of graphite, lithium titanate or silicon negative electrode; The graphite is hard carbon or soft carbon; The second binder powder is one or a mixture of at least two of PTFE, PVDF, PEO or short fibers; The second conductive agent powder is one or a mixture of at least two of conductive carbon black, carbon nanotubes, graphene or conductive graphite.

7. The bipolar battery according to claim 6, characterized in that: The negative electrode sheet is prepared by the following method: in an environment with a dew point temperature of ≤-30°C, 80% to 98% of negative electrode active material powder, 1% to 10% of second binder powder and 0.5% to 10% of second conductive agent powder are uniformly mixed and dispersed to obtain a mixed powder; the mixed powder is rolled and then die-cut to obtain a negative electrode sheet, and the thickness of the negative electrode sheet is 0.05mm to 10.0mm.

8. The bipolar battery according to claim 7, characterized in that: The dispersion temperature is 50° C. to 180° C., the dispersion line speed is 10 m / s to 30 m / s; the roller pressing temperature is 80° C. to 200° C.; and the roller pressing pressure is 10T to 500T.

9. The bipolar battery according to claim 1, characterized in that: The bipolar battery is a lithium ion battery, a sodium ion battery or a zinc ion battery.

10. The method for preparing a bipolar battery according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: in an environment with a dew point temperature of ≤-30°C, stacking two current collectors, a negative electrode sheet, a separator and a positive electrode sheet in the order of current collector, negative electrode sheet, separator, positive electrode sheet and current collector to obtain a battery unit; and connecting a plurality of the battery units in series to obtain a bipolar battery.

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