Bipolar battery and electric apparatus

Abstract

Provided in the present application are a bipolar battery and an electric apparatus. The bipolar battery comprises n stacked bipolar electrodes, where n>1. Each of the bipolar electrodes comprises: a current collector, and a positive-electrode film layer provided on one side of the current collector, wherein the side of the current collector on which the positive-electrode film layer is provided is a positive side, and the side opposite to the positive side is a negative side; and the negative side is optionally provided with a negative electrode film layer or a conductive layer.

Description

Bipolar battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application 202311368246.x, filed on October 20, 2023, entitled “Bipolar Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a bipolar battery and an electrical device. Background Art

[0004] A typical secondary battery structure consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The conversion of chemical energy into electrical energy is achieved through the exchange of ions and electrons between the positive and negative electrodes. In traditional electrode preparation, the same active material is coated on both sides of the metal current collector to prepare a positive electrode sheet or a negative electrode sheet. A separator is used to prevent mutual contact, and the cells are assembled to form a single cell. Electric vehicles require high voltage to drive the motor. Due to the limited voltage of a single cell, it is necessary to connect dozens or even hundreds of single cells in series to maintain a high operating voltage. Such high voltage and high current density output require a large number of external control devices, which complicates the battery pack structure and reduces the battery's specific energy and power.

[0005] Summary of the Invention

[0006] The present application provides a bipolar battery and an electrical device to simplify the battery structure.

[0007] The first aspect of the present application provides a bipolar battery, comprising n stacked bipolar electrodes where n>1, the bipolar electrodes comprising: a current collector; a positive electrode film layer arranged on one side of the current collector, the side of the current collector provided with the positive electrode film layer being the positive electrode side, and the side opposite to the positive electrode side being the negative electrode side; the negative electrode side being optionally provided with a negative electrode film layer or a conductive layer.

[0008] Compared to the conventional method of increasing the lower limit voltage through external series connection, bipolar batteries reduce the mechanical structural units required for multiple battery cells in series to achieve high voltage. This not only simplifies the battery pack structure but also improves the specific power and specific energy of the single battery pack. This is especially true for sodium-ion batteries, which are not suitable for high-power devices due to their wide voltage range and low lower limit voltage. A higher lower limit voltage is required. Using bipolar structural units is equivalent to connecting two or more batteries in series within the battery, which is more conducive to achieving a higher lower limit voltage and broadens the application scenarios of sodium-ion batteries.

[0009] According to any embodiment of the first aspect of the present application, when the bipolar electrode has a negative electrode film layer, the CB value of the bipolar electrode is 1.05 (n-1) ~1.1 n CB value = (A × T1 × S1) / (C × T2 × S2), where A is the areal density of the negative electrode film, T1 is the gram capacity of the negative electrode active material in the negative electrode film (i.e., the conventionally referred to charge gram capacity), S1 is the loading of the negative electrode active material in the negative electrode film, C is the areal density of the positive electrode film, T2 is the gram capacity of the positive electrode active material in the positive electrode film (i.e., the conventionally referred to charge gram capacity), and S2 is the loading of the positive electrode active material in the positive electrode film. Reduce safety risks and improve cycle performance.

[0010] According to any embodiment of the first aspect of the present application, the above 1<n≤200.

[0011] According to any embodiment of the first aspect of the present application, the bipolar electrode has a negative electrode film layer, and the bipolar electrode further includes: a first insulating layer, disposed on the negative electrode side of the current collector, the first insulating layer extending from the negative electrode film layer toward the edge of the current collector; a second insulating layer, disposed on the positive electrode side of the current collector, the second insulating layer extending from the positive electrode film layer toward the edge of the current collector; optionally, the thickness of the negative electrode film layer is a, the thickness of the positive electrode film layer is c, the thickness of the first insulating layer is d1, the thickness of the second insulating layer is d2, a≤d1≤1.1a and / or c≤d2≤1.1c. The provision of the first insulating layer and the second insulating layer facilitates retaining as much electrolyte as possible within the active area during hot pressing.

[0012] According to any embodiment of the first aspect of the present application, the above-mentioned bipolar electrode is a negative-pole bipolar electrode, and the bipolar electrode includes a conductive layer arranged on the negative electrode side of the current collector. The bipolar electrode also includes: a first insulating layer, arranged on the negative electrode side of the current collector, and the first insulating layer extends from the conductive layer to the edge of the current collector; a second insulating layer, arranged on the positive electrode side of the current collector, and the second insulating layer extends from the positive electrode film layer to the edge of the current collector; optionally, the thickness of the positive electrode film layer is c, and the thickness of the conductive layer is less than c; optionally, the thickness of the first insulating layer is d1, and the thickness of the second insulating layer is d2, c≤d1≤1.1c and / or c≤d2≤1.1c. The provision of the first insulating layer and the second insulating layer, on the one hand, is conducive to retaining as much electrolyte as possible in the active area during hot pressing, and on the other hand, leaves space for the volume changes of the positive electrode film layer and the conductive layer and the deposited negative electrode active layer caused by the deintercalation of active ions, for example, alleviating the problem of active ions being squeezed out due to insufficient space after being deposited on the negative electrode side, resulting in a decrease in battery cycle performance and reliability.

[0013] According to any embodiment of the first aspect of the present application, the bipolar electrode is a negative-pole-free bipolar electrode, wherein a negative-pole sodium deposition region is provided on the negative-pole side of the bipolar electrode. The bipolar electrode further comprises: a first insulating layer disposed on the negative-pole side of the current collector, the first insulating layer extending from the negative-pole sodium deposition region toward the edge of the current collector; a second insulating layer disposed on the positive-pole side of the current collector, the second insulating layer extending from the positive-pole film layer toward the edge of the current collector; the thickness of the positive-pole film layer is c, the thickness of the first insulating layer is d1, and the thickness of the second insulating layer is d2, wherein c≤d1≤2c and / or c≤d2≤2c. This not only reserves sufficient space for volume changes in the bipolar electrode but also avoids deformation of the bipolar pole pieces and unnecessary reduction in battery energy density due to excessive bipolar electrode spacing.

[0014] According to any embodiment of the first aspect of the present application, the electrolyte is a liquid electrolyte. Optionally, the bipolar battery further includes a first insulating layer and a second insulating layer, wherein the first insulating layer is disposed on the negative electrode side of the current collector, and the second insulating layer is disposed on the positive electrode side of the current collector, and the projected area of ​​the first insulating layer on the positive electrode side is smaller than the area of ​​the second insulating layer. Optionally, the extension direction from the positive electrode film layer to the edge of the current collector is defined as the width direction of the first insulating layer and the second insulating layer, and the projected width M1 of the first insulating layer on the positive electrode side is smaller than the width M2 of the second insulating layer. Further, M2-M1 is optionally between 2 mm and 10 mm. This provides ample space for negative electrode sodium deposition, more accurately limits the deposition position of active ions on the negative electrode side, limits their deposition in the negative electrode lead-out tab region, and more effectively improves the cyclic intercalation and deintercalation efficiency of active ions.

[0015] According to any embodiment of the first aspect of the present application, the above-mentioned electrolyte is an all-solid-state electrolyte or a gel electrolyte; optionally, the electrolyte is a gel polymer electrolyte; further optionally, the electrolyte includes any one or more of polyethylene oxide gel electrolyte, polyacrylonitrile gel electrolyte, polymethyl methacrylate gel electrolyte, and polyvinylidene fluoride gel electrolyte.

[0016] According to any embodiment of the first aspect of the present application, the above p1 is the compaction of the negative electrode powder used in the negative electrode film layer under a pressure of 2t; p2 is the compaction of the positive electrode powder used in the positive electrode film layer under a pressure of 3t, and p min is the minimum value between P1 and P2, p max is the maximum value between P1 and P2, the compaction of the bipolar electrode is p, and p satisfies p min ≤p≤1.2p max .

[0017] According to any embodiment of the first aspect of the present application, the above-mentioned bipolar battery is a sodium ion battery, and the current collector of the bipolar electrode includes aluminum foil, stainless steel foil, and a polymer material substrate or copper foil with a double-sided metal layer; optionally, the positive electrode active material in the positive electrode film layer is sodium vanadium phosphate; optionally, in the bipolar electrode, the negative electrode side of the current collector is uncoated and the negative electrode side is a rough surface, or the negative electrode side of the current collector has a conductive layer, or the negative electrode side of the current collector has a negative electrode film layer, and optionally the negative electrode active material in the negative electrode film layer is hard carbon; or the bipolar battery is a lithium ion battery, and the current collector of the bipolar electrode includes stainless steel foil, aluminum-copper composite foil, or polymer foil with aluminum or copper plated on both ends.

[0018] A second aspect of the present application provides an electrical device, comprising a secondary battery, wherein the secondary battery is any one of the bipolar batteries provided in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0020] FIG1 is an exploded cross-sectional view of a bipolar battery provided in one embodiment of the present application.

[0021] FIG2 is a cross-sectional exploded view of a bipolar battery provided in another embodiment of the present application.

[0022] FIG3 is a cross-sectional exploded view of a bipolar battery provided in another embodiment of the present application.

[0023] FIG. 4 is a schematic side view of the bipolar electrode structure of the bipolar battery provided in FIG. 1 .

[0024] FIG5 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0025] FIG. 6 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 5 .

[0026] FIG7 is a schematic diagram of a battery module according to an embodiment of the present application.

[0027] FIG8 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0028] FIG. 9 is an exploded view of the battery pack shown in FIG. 8 according to an embodiment of the present application.

[0029] FIG. 10 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0030] In the drawings, the drawings are not drawn to scale.

[0031] Description of reference numerals:

[0032] 10 end positive electrode sheet; 20 bipolar electrode; 21 positive electrode film layer; 22 negative electrode film layer; 23 current collector; 24 conductive layer; 25 first insulating layer; 26 second insulating layer; 30 end negative electrode sheet; 40 separator;

[0033] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0034] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0035] Below, embodiments of the bipolar battery and electrical device of the present application are described in detail, with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary length in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0036] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0040] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0041] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0042] [Bipolar battery]

[0043] In order to simplify the battery structure, the first embodiment of the present application proposes a bipolar battery, as shown in Figure 1, which includes n stacked bipolar electrodes 20 and n>1, the bipolar electrode 20 includes a current collector 23, a positive electrode film layer 21 and optionally a negative electrode film layer 22 or a conductive layer 24, the positive electrode film layer 21 is arranged on one side of the current collector 23, the side of the current collector 23 provided with the positive electrode film layer 21 is the positive electrode side, and the side opposite to the positive electrode side is the negative electrode side, and the negative electrode side of the current collector 23 is optionally provided with a negative electrode film layer 22 or a conductive layer 24.

[0044] Compared to the conventional method of increasing the lower limit voltage through external series connection, bipolar batteries reduce the mechanical structural units required for multiple battery cells in series to achieve high voltage, which not only simplifies the battery structure but also increases the power consumption and energy density of each cell. This is especially true for sodium-ion batteries, which are not suitable for high-power devices due to their wide voltage range and low lower limit voltage. The use of bipolar structural units is equivalent to connecting two or more batteries in series within the battery, which is more conducive to achieving a higher lower limit voltage.

[0045] In the above-described embodiments, the negative electrode side of the bipolar electrode 20 can be disposed in a variety of ways. It can be provided without any coating, provided with only the conductive layer 24, or provided with the negative electrode film layer 22. The bipolar electrodes 20 formed in the above-described three ways can be divided into two categories: one is a bipolar electrode 20 provided with a negative electrode film layer 22, referred to as a "negative bipolar electrode"; the other is a bipolar electrode 20 not provided with a negative electrode film layer 22, referred to as a "negative bipolar electrode." In the negative electrode-free bipolar electrode, one side of the current collector 23 is coated with a positive electrode film layer 21 and the other side is composed of no active material. This negative electrode-free bipolar electrode has the following advantages over the existing negative electrode-free sodium secondary battery: the negative electrode-free sodium secondary battery uses a thin layer of current collector 23 or a thin layer of conductive layer 24 coated on the surface of the current collector 23 as the negative electrode. The disadvantage is that the electrode sheet is thin and wrinkled during the winding production. The negative electrode-free bipolar electrode has an increased composite thickness of the negative electrode-free current collector 23 and the positive electrode and is not easy to wrinkle. At the same time, the positive and negative electrodes share the same current collector 23, which saves half of the current collector volume and electrons can be conducted more quickly.

[0046] In order to enable those skilled in the art to better understand the negative electrode-free bipolar electrode, the following explanation is given using a negative electrode-free sodium secondary battery as an example. A negative electrode-free sodium secondary battery refers to a battery that does not actively set a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery (Note: This is mainly to avoid conflict with the setting of a small amount of negative electrode active material below). For example, during the manufacturing process of the battery, a sodium metal or carbonaceous active material layer is not set at the negative electrode through processes such as coating or deposition to form a negative electrode active material layer. During the first charge, sodium ions obtain electrons on the negative electrode side and metallic sodium is deposited on the surface of the current collector to form a sodium metal phase. During discharge, metallic sodium can be converted into sodium ions and return to the positive electrode to achieve cyclic charge and discharge. Compared with other sodium secondary batteries, negative electrode-free sodium secondary batteries can achieve higher energy density due to the lack of a negative electrode active material layer. Corresponding to the negative electrode-free bipolar electrode of the above-mentioned embodiment of the present application, it also means that no negative electrode film layer containing negative electrode active material is provided on the negative electrode side of the current collector. During the first charge, sodium ions are deposited on the negative electrode side surface of the current collector or on the conductive layer of the current collector. The deposited area is the negative electrode sodium deposition area, and the projection of this area on the positive electrode side overlaps with or covers the positive electrode film layer 21. During the sodium ion insertion and extraction process of the negative electrode-free bipolar electrode, there is no problem of volume expansion and contraction of the negative electrode active material, and the conductive layer 24 can improve the sodium ion transmission power, thereby improving the cycle performance of the bipolar battery.

[0047] In some embodiments, as shown in Figure 1, the above-mentioned bipolar battery includes an electrolyte, an end positive electrode sheet 10, an end negative electrode sheet 30 and the above-mentioned n stacked bipolar electrodes 20, a separator 40 is arranged between adjacent stacked bipolar electrodes 20, and the bipolar electrode 20 is arranged between the end positive electrode sheet 10 and the end negative electrode sheet 30.

[0048] When there is a negative bipolar electrode, the current collector 23 is coated with a positive electrode film layer 21 on one side and a negative electrode film layer 22 on the other side. When multiple bipolar electrodes 20 are stacked, there is loss in the electron transfer process. In order to more effectively control the sodium or lithium deposition of the negative electrode, reduce the safety risk of the bipolar battery, and improve the cycle performance of the bipolar battery.

[0049] In some embodiments of the present application, when the bipolar electrode 20 has a negative electrode film layer 22, the CB value of the bipolar electrode 20 is 1.05. (n-1) ~1.1 n , CB value = (A×T1×S1) / (C×T2×S2), where A is the surface density of the negative electrode film layer 22, T1 is the gram capacity of the negative electrode active material in the negative electrode film layer 22, S1 is the loading amount of the negative electrode active material in the negative electrode film layer 22, C is the surface density of the positive electrode film layer 21, T2 is the gram capacity of the positive electrode active material in the positive electrode film layer 21, and S2 is the loading amount of the positive electrode active material in the positive electrode film layer 21.

[0050] The loading amount of the positive electrode active material in the positive electrode film layer refers to the mass content of the positive electrode active material in the positive electrode film layer; the loading amount of the negative electrode active material in the negative electrode film layer refers to the mass content of the negative electrode active material in the negative electrode film layer.

[0051] The above-mentioned design is performed on the CB value of the negative bipolar electrode 20, that is, the CB value is adaptively set according to the number of bipolar electrodes in the bipolar battery, so that the negative electrode capacity has a more appropriate capacity excess design relative to the positive electrode capacity, ensuring that there is sufficient capacity on the negative electrode side to meet the embedding of sodium ions / lithium ions released from the positive electrode, and to meet the positive electrode capacity as much as possible, effectively reducing the sodium dendrites / lithium dendrites generated during the charging process, or the sodium dendrites / lithium dendrites generated during the cycle process, thereby reducing safety risks and improving cycle performance.

[0052] The present application does not particularly limit the form of the bipolar battery, which can be either a laminated battery or a wound battery.

[0053] The bipolar battery of the present application has no particular requirement for the number of bipolar electrodes 20. In some embodiments, 1 < n ≤ 200 to accommodate the voltage settings of different electrical devices. The number of bipolar electrodes 20 can be adjusted within the above range, such as to 5, 10, 20, 50, 100, 150, or 200, depending on the voltage setting requirements of the different electrical devices.

[0054] In some embodiments, the n bipolar electrodes adopt the same design, that is, each bipolar electrode adopts the same positive electrode film layer and negative electrode film layer design.

[0055] In some embodiments of the present application, as shown in FIG4 , bipolar electrode 20 includes a negative electrode film layer 22 . That is, bipolar electrode 20 is the aforementioned negative electrode bipolar electrode 20 . Bipolar electrode 20 also includes a first insulating layer 25 and a second insulating layer 26 . First insulating layer 25 is disposed on the negative electrode side of current collector 23 , extending from negative electrode film layer 22 toward the edge of current collector 23 . Second insulating layer 26 is disposed on the positive electrode side of current collector 23 , extending from positive electrode film layer 21 toward the edge of current collector 23 . The provision of first insulating layer 25 and second insulating layer 26 facilitates retaining as much electrolyte as possible within the active area during hot pressing.

[0056] In some embodiments of the present application, optionally, the thickness of the negative electrode film layer 22 is a, the thickness of the positive electrode film layer 21 is c, the thickness of the first insulating layer 25 is d1, and the thickness of the second insulating layer 26 is d2, where a≤d1≤1.1a and / or c≤d2≤1.1c. This not only reserves sufficient space for the volume change of the bipolar electrodes 20 but also avoids deformation of the bipolar pole pieces and unnecessary reduction in battery energy density caused by excessive spacing between the bipolar electrodes 20.

[0057] In some embodiments of the present application, refer to Figure 4 and replace the negative electrode film layer 22 in Figure 4 with the following conductive layer 24, the bipolar electrode 20 is a bipolar electrode 20 without a negative electrode, and the bipolar electrode 20 includes a current collector 23 and a positive electrode film layer 21 arranged on the positive electrode side of the current collector 23 and a conductive layer 24 arranged on the negative electrode side of the current collector 23. The bipolar electrode 20 also includes a first insulating layer 25 and a second insulating layer 26. The first insulating layer 25 is arranged on the negative electrode side of the current collector 23, and the first insulating layer 25 extends from the conductive layer 24 to the edge of the current collector 23; the second insulating layer 26 is arranged on the positive electrode side of the current collector 23, and the second insulating layer 26 extends from the positive electrode film layer 21 to the edge of the current collector 23. The provision of the first insulating layer 25 and the second insulating layer 26, on the one hand, facilitates retaining as much electrolyte as possible within the active area during hot pressing. On the other hand, it leaves room for volume changes in the positive electrode film layer 21 and the conductive layer 24, as well as the deposited negative electrode active layer, caused by the deintercalation of active ions. For example, this alleviates the problem of active ions being squeezed out due to insufficient space after being deposited on the negative electrode side, leading to reduced battery cycle performance and reliability. Moreover, the first insulating layer 25 provided in the negative-electrode-free bipolar electrode 20 can effectively reduce the deposition of active ions in areas outside the conductive layer 24 during charging, thereby allowing the deposited active ions to be released during discharge, achieving sufficient circulation of the active ions and improving the battery's cycle performance.

[0058] Regarding the above-mentioned embodiment with a conductive layer 24, in some embodiments of the present application, optionally, the thickness of the positive electrode film layer 21 is c, and the thickness of the conductive layer 24 is less than c, so as to avoid the conductive layer 24 being too thick, resulting in a reduction in the energy density of the bipolar battery.

[0059] Regarding the aforementioned embodiment with the conductive layer 24, in some embodiments of the present application, the thickness of the first insulating layer 25 is d1, the thickness of the second insulating layer 26 is d2, and c≤d1≤1.1c and / or c≤d2≤1.1c. This not only reserves sufficient space for the volume change of the bipolar electrodes 20, but also avoids deformation of the bipolar pole pieces and unnecessary reduction in battery energy density caused by excessive spacing between the bipolar electrodes 20.

[0060] In some embodiments of the present application, referring to Figure 4 and removing the negative electrode film layer 22 in Figure 4, the bipolar electrode 20 is a bipolar electrode 20 without a negative electrode, and the bipolar electrode 20 includes a current collector 23 and a positive electrode film layer 21 arranged on the positive electrode side of the current collector 23, and a negative electrode sodium deposition area is provided on the negative electrode side of the bipolar electrode 20. The bipolar electrode 20 also includes a first insulating layer 25 and a second insulating layer 26. The first insulating layer 25 is arranged on the negative electrode side of the current collector 23, and the first insulating layer 25 extends from the negative electrode sodium deposition area to the edge of the current collector 23; the second insulating layer 26 is arranged on the positive electrode side of the current collector 23, and the second insulating layer 26 extends from the positive electrode film layer 21 to the edge of the current collector 23.

[0061] The provision of the first insulating layer 25 and the second insulating layer 26, on the one hand, facilitates retaining as much electrolyte as possible within the active area during hot pressing, and on the other hand, leaves room for volume changes in the positive electrode film layer 21 and the deposited negative electrode active layer caused by the deintercalation of active ions. For example, this alleviates the problem of active ions being squeezed out due to insufficient space after being deposited on the negative electrode side, resulting in reduced battery cycle performance and reliability. Moreover, the provision of the first insulating layer 25 in the negative electrode-free bipolar electrode 20 can effectively reduce the deposition of active ions in areas outside the negative electrode sodium deposition area during the charging process, reducing sodium dendrites, and thus allowing the deposited active ions to be released during discharge, achieving full circulation of the active ions and improving the battery's cycle performance.

[0062] Regarding the aforementioned embodiment of the bipolar electrode 20 without a negative electrode, in some embodiments of the present application, the thickness of the positive electrode film layer 21 is c, the thickness of the first insulating layer 25 is d1, and the thickness of the second insulating layer 26 is d2, where c≤d1≤2c and / or c≤d2≤2c. This not only reserves sufficient space for the volume change of the bipolar electrode 20 but also avoids deformation of the bipolar pole pieces and unnecessary reduction in battery energy density caused by excessive spacing between the bipolar electrodes 20.

[0063] The bipolar battery of the present application can be used in a battery structure design with a tab, and can also be used in a battery structure design without a tab. In some embodiments of the present application, the bipolar battery further includes tabs, and a positive electrode lead-out tab region is provided on the positive electrode side, and a negative electrode lead-out tab region is provided on the negative electrode side. There are no special requirements for the position setting of the positive electrode lead-out tab region and the negative electrode lead-out tab region, and conventional designs can be referred to, such as being provided on the short side of the current collector. The setting of the tabs also refers to the prior art, and this application will not elaborate on them. Since the first insulating layer 25 and the second insulating layer 26 are provided in the bipolar electrodes of some of the above embodiments of the present application, the setting of the first insulating layer 25 and the second insulating layer 26 effectively prevents the deposition of sodium ions in the lead-out tab region.

[0064] The primary function of the first and second insulating layers 25, 26 is insulation. Therefore, any insulating material used for battery cells in secondary batteries can be considered for use as the first and second insulating layers 25, 26. In some embodiments, the insulating materials for the first and second insulating layers 25, 26 include, but are not limited to, polyvinylidene fluoride, a composite of polyvinylidene fluoride and aluminum oxide, and polyimide. The first and second insulating layers 26 can be applied by coating, for example, after applying the corresponding active material.

[0065] In some embodiments of the present application, the above-mentioned bipolar electrode without a negative electrode is more suitable for sodium ion battery systems. The bipolar electrode with a negative electrode is suitable for both sodium ion battery systems and lithium ion battery systems.

[0066] In some embodiments of the present application, the bipolar battery is a sodium ion battery, and the current collector of the bipolar electrode includes aluminum foil, stainless steel foil, a polymer substrate with a double-sided metallization layer, or copper foil. In some embodiments, the polymer substrate includes, but is not limited to, substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0067] In some embodiments where the bipolar battery is a sodium-ion battery, the positive electrode active material in the positive electrode film layer can be selected from conventional positive electrode active materials used in sodium-ion batteries, such as at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0068] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0069] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence.

[0070] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0071] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0072] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0073] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0<a≤2, 0<b<1, and 0<c<1. In some embodiments, the positive electrode active material in the positive electrode film layer is optionally sodium vanadium phosphate.

[0074] The positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0075] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] When the bipolar battery is a sodium ion battery, it can be a sodium ion battery with a negative electrode or a sodium ion battery without a negative electrode. The so-called sodium ion battery without a negative electrode is a method in which the negative electrode adopts a current collector with a rough surface on the negative electrode side or a current collector with a conductive layer. In some embodiments of the present application, optionally, in the bipolar electrode, the negative electrode side of the current collector is uncoated and has a rough surface, or has a conductive layer. The roughness and formation method of the rough surface can refer to conventional settings and will not be repeated in this application.

[0077] In some embodiments, the conductive layer includes a conductive agent and a binder. Further optionally, the conductive agent includes any one or more of conductive carbon, conductive polymer, and conductive ceramic material. The conductive carbon includes but is not limited to graphite, graphene, carbon fiber, carbon black, carbon dots, soft carbon, hard carbon, multi-walled carbon nanotubes, or single-walled carbon nanotubes.

[0078] In some embodiments, the conductive layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0079] In some embodiments of the present application, the bipolar battery is a sodium ion battery with a negative electrode, that is, in the bipolar electrode, the negative electrode side of the current collector has a negative electrode film layer.

[0080] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more. In some embodiments, considering that hard carbon has a small volume expansion when fully charged, the negative electrode active material in the negative electrode film layer is selected from hard carbon.

[0081] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0082] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0084] In some embodiments of the present application, the bipolar battery is a lithium-ion battery, and the current collector of the bipolar electrode includes stainless steel foil, aluminum-copper composite foil, or polymer foil with aluminum or copper plated on both ends.

[0085] The positive electrode film layer of the bipolar electrode of the lithium-ion battery includes a positive electrode active material. In some embodiments, the positive electrode active material may be a positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0086] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0087] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] The negative electrode film layer of the bipolar electrode of the lithium-ion battery includes a negative electrode active material, and the negative electrode active material can be a negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0089] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0090] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0091] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0092] [Electrolytes]

[0093] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0094] In some embodiments of the present application, the electrolyte is a liquid electrolyte, and the bipolar battery is a liquid battery. Due to the fluidity of the electrolyte in the liquid battery, the lateral diffusion of the active ions makes it difficult to control the position when deposited on the negative electrode side. Optionally, the bipolar electrolyte further includes a first insulating layer 25 and a second insulating layer 26. The specific arrangement of the first insulating layer 25 and the second insulating layer 26 can refer to the aforementioned embodiments. The first insulating layer 25 and the second insulating layer 26 effectively control the active area for the deintercalation of the active ions, thereby effectively improving the cycle performance of the bipolar battery.

[0095] Furthermore, in some embodiments of the liquid battery, the projected area of ​​the first insulating layer 25 on the positive electrode side is smaller than the area of ​​the second insulating layer 26. Optionally, the direction from the positive electrode film layer to the positive electrode lead-out tab region is defined as the width direction of the first insulating layer 25 and the second insulating layer 26. The projected width M1 of the first insulating layer 25 on the positive electrode side is smaller than the width M2 of the second insulating layer 26. Further, M2-M1 is optionally between 2 mm and 10 mm. The above design provides ample space for negative electrode sodium deposition, more precisely limits the deposition location of active ions on the negative electrode side, limits their deposition in the negative electrode lead-out tab region, and more effectively improves the cyclic intercalation and deintercalation efficiency of active ions.

[0096] The above-mentioned embodiments of the present application have no special requirements for liquid electrolytes, and conventional liquid electrolytes used in lithium-ion batteries or sodium-ion batteries can be considered for application in the present application.

[0097] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0098] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0099] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0100] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0101] In some embodiments of the present application, the above-mentioned electrolyte is a solid electrolyte or a semi-solid electrolyte, that is, the bipolar battery is a solid-state battery. When it is a solid-state battery, the fluidity of the solid electrolyte or semi-solid electrolyte therein is small, so the lateral diffusion of active ions is limited, and the deposition position on the negative electrode side is easier to control. In some embodiments, the first insulating layer 25 and the second insulating layer 26 may not be provided; and the solid electrolyte has a high mechanical strength, which can support the isolation membrane and improve the mechanical stability of the battery.

[0102] In the above-mentioned solid-state battery scheme, in some embodiments, the above-mentioned electrolyte is a gel polymer electrolyte, which has both certain flow buffering properties and certain mechanical strength. Therefore, while achieving efficient ion conduction, it can also avoid the problem of uncontrolled deposition caused by lateral diffusion of active ions due to excessive flow, and its mechanical strength provides effective support for the isolation membrane.

[0103] In some embodiments, the electrolyte includes any one or more of polyethylene oxide (PEO) gel electrolyte, polyacrylonitrile (PAN) gel electrolyte, polymethyl methacrylate (PMMA) gel electrolyte, and polyvinylidene fluoride (PVDF) gel electrolyte.

[0104] In some embodiments of the present application, the above-mentioned solid electrolyte includes but is not limited to polyethylene oxide (PEO)-based solid electrolytes, oxide-based sodium ion conductors, sulfur-based sodium ion conductors, and composite solid electrolytes formed by combining any two or more of the above.

[0105] In some embodiments of the present application, p1 represents the compaction of the negative electrode powder used in the negative electrode film layer under a pressure of 2t; p2 represents the compaction of the positive electrode powder used in the positive electrode film layer under a pressure of 3t; pmin represents the minimum of P1 and P2, and pmax represents the maximum of P1 and P2. The compaction of the bipolar electrode is p, where p satisfies pmin ≤ p ≤ 1.2pmax. This compaction control effectively mitigates overpressure damage to the powders on both the positive and negative sides of the bipolar electrode. The compaction of each of the above powders was tested using an electronic pressure testing machine.

[0106] For the end positive electrode sheet and the end negative electrode sheet, their composition can refer to the positive side composition and negative side composition of the corresponding bipolar electrode, and the end positive electrode sheet can be a single-sided electrode or a double-sided electrode with film layers on both sides similar to the conventional positive electrode sheet; the end negative electrode sheet can also be a current collector without a negative electrode, or a current collector with a conductive layer or a current collector with a negative electrode film layer, and can be a single-sided electrode or a double-sided electrode.

[0107] In some embodiments of the present application, a bipolar electrode can be prepared by the following method:

[0108] coating an insulating layer on a predetermined position of the current collector;

[0109] The components for preparing the positive electrode film are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on one side of a current collector, and after drying, cold pressing, and other processes, a current collector having a positive electrode film layer can be obtained;

[0110] The above-mentioned components for preparing the negative electrode film layer or the conductive layer are dispersed in a solvent (such as N-methylpyrrolidone) to form a negative electrode slurry or a conductive slurry; the negative electrode slurry or the conductive slurry is coated on one side of the current collector, and after drying, cold pressing and other processes, a current collector having a negative electrode film layer or a conductive layer can be obtained, and the preparation of the bipolar electrode is completed; of course, if the negative electrode has a rough surface, the above process of preparing the negative electrode film layer or the conductive layer is not required.

[0111] [Isolation film]

[0112] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0113] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0114] In some embodiments, the end positive electrode sheet, the bipolar electrode, the end negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0115] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0116] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0117] The present application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square, or any other shape. For example, FIG5 shows a secondary battery cell 5 with a square structure as an example.

[0118] In some embodiments, referring to Figure 6, the outer packaging may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The end positive electrode sheet, the bipolar electrode, and the end negative electrode sheet can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0119] In some embodiments, secondary battery cells may be assembled into a battery module. The battery module may contain one or more secondary batteries, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0120] Figure 7 shows an example battery module 4. Referring to Figure 7 , within the battery module 4, multiple secondary battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple secondary battery cells 5 may be secured together using fasteners.

[0121] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary battery cells 5 are accommodated in the accommodation space.

[0122] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0123] Figures 8 and 9 illustrate an example battery pack 1. Referring to Figures 8 and 9 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0124] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0125] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0126] Figure 10 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0127] [Example]

[0128] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0129] Example 1

[0130] Preparation process of bipolar electrodes

[0131] Aluminum foil is used as the current collector, and one side is coated with a 150μm thick positive electrode film layer, wherein the positive electrode active material in the positive electrode film layer is sodium iron pyrophosphate, the conductive agent is conductive carbon, and the binder is PDVF; the mass ratio of the three is 95:2:3; the other side is coated with a 200μm thick negative electrode film layer, wherein the negative electrode active material in the negative electrode film layer is hard carbon, the conductive agent is conductive carbon, and the binder is CMC; the mass ratio of the three is 95:2:3; polyvinylidene fluoride is used as the insulating layer raw material, and a first insulating layer is provided on the negative electrode side, which is arranged around the negative electrode film layer, and the projection width M1 of the first insulating layer on the negative electrode side on the positive electrode side is 4mm; a second insulating layer is provided on the positive electrode side, which is arranged around the positive electrode film layer, and the width M2 of the second insulating layer on the positive electrode side is 10mm, the negative electrode film layer coating area on the negative electrode side is 100mm wide, and the positive electrode film layer coating area on the positive electrode side is 88mm wide.

[0132] Electrolyte: The electrolyte contains 0.5 mol / L NaPF6, the solvent is EC+DMC, and the volume ratio of EC to DMC is 1:1.

[0133] Diaphragm: PE porous polymer film is used as the isolation membrane.

[0134] The above-mentioned bipolar electrodes, diaphragm and electrolyte are assembled into a button battery in a button battery box.

[0135] Use a micrometer to measure the thickness of the positive electrode film layer, the thickness of the negative electrode film layer, the width and thickness of the first insulating layer, and the width and thickness of the second insulating layer;

[0136] Take a specific area of ​​the film layer and weigh its mass, and divide the mass of the film layer by the taken area to calculate the surface density.

[0137] The compaction of the positive electrode active material and the compaction of the negative electrode active material were tested using an electronic pressure testing machine model UTM7305, and the measurements were performed under specified pressures, wherein the compaction of the positive electrode active material was tested under a pressure of 3t, and the compaction of the negative electrode active material was tested under a pressure of 2t.

[0138] Compression of bipolar pole piece: The calculated surface density is divided by the thickness of the film layer to obtain the compression of the pole piece.

[0139] Test of gram capacity T1 of negative electrode active material in negative electrode film layer:

[0140] The negative electrode sheet, separator, and sodium sheet were assembled and charged to conduct a gram capacity test of the negative electrode active material.

[0141] Within the rated charge and discharge range (generally 0.005V~2.5V), charge at a constant current rate of 0.33C to the full charge voltage (0.005V), and then charge at a constant voltage (full charge voltage) until the current reaches 0.05C. Integrate the charging current and charging time to obtain the charging capacity, and then divide it by the mass of the negative electrode active material (negative electrode coating mass * negative electrode active material loading) to obtain the gram capacity of the negative electrode active material.

[0142] Test of gram capacity T2 of positive electrode active material in positive electrode film layer:

[0143] The above-mentioned positive electrode sheet, separator, and sodium sheet were assembled into a battery and the gram capacity of the positive electrode active material was tested. Within the rated charge and discharge range (the upper and lower limits vary depending on the specific positive electrode material), the battery was charged at a constant current rate of 0.33C to the full charge voltage. Then, the battery was charged at a constant voltage (full charge voltage) until the current reached 0.05C. The charge capacity was obtained by integrating the charge current and charge time. This was then divided by the mass of the positive electrode active material in the battery (positive electrode coating mass * positive electrode active material loading) to obtain the gram capacity of the positive electrode active material.

[0144] The test results are recorded in Table 1.

[0145] The compositions of the bipolar electrodes of Examples 2 to 13, 16 to 17 are slightly adjusted relative to Example 1, as shown in Table 1 for details.

[0146] Example 14

[0147] The bipolar electrode is the same as that in Example 1, and the electrolyte is polyethylene oxide gel electrolyte: the ratio of PEO to Na ion is 15:1. PEO and sodium hexafluorophosphate are mixed and dissolved in tetrahydrofuran, dried to form an electrolyte film, spread on the surface of the electrode to form it, and then further dried.

[0148] Example 15

[0149] The first insulating layer and the second insulating layer are not provided in the bipolar electrode, and the rest is the same as in Example 14.

[0150] Examples 18 and 19

[0151] The compositions of the bipolar electrodes of Examples 18 and 19 are slightly adjusted relative to those of Example 15, as shown in Table 1.

[0152] Cyclic performance test: Charge at a constant current rate of 0.33C to the full charge voltage on a charge and discharge tester, then charge at a constant voltage rate of 0.05C (full charge voltage), let it stand for 10 minutes, and discharge at a constant current rate of 1C to the cut-off voltage; repeat the above charge and discharge until the capacity decays to 80%, and record the number of cycles.

[0153] The test results are recorded in Table 1.

[0154] According to the data of Example 1, Example 4, 5, 16 and 17 in Table 1, it can be seen that the cycle performance of the battery can be adjusted by adjusting the CB value, especially when the CB value meets 1.05. (n- 1) ~1.1 n The cycle performance is significantly improved.

[0155] According to the data comparison of Examples 6 to 9 in Table 1, it can be seen that the thickness design of the first insulating layer and the second insulating layer will also affect the cycle performance of the battery.

[0156] According to the data comparison of Examples 10 to 13, it can be seen that the width design of the first insulating layer and the second insulating layer will also affect the cycle performance of the battery.

[0157] Example 20

[0158] Preparation process of bipolar electrodes

[0159] Aluminum foil is used as the current collector, and one side is coated with a 150μm thick positive electrode film layer, wherein the positive electrode active material in the positive electrode film layer is sodium iron pyrophosphate, the conductive agent is conductive carbon, and the binder is PDVF; the mass ratio of the three is 95:2:3, and the formed positive electrode film layer is the same as the positive electrode film layer of Example 1; the other side is a rough substrate, and is coated with a conductive layer of carbon nanotubes with a thickness of 0.002μm; polyvinylidene fluoride is used as the insulating layer raw material, and a first insulating layer 25 is provided on the negative electrode side, which is arranged around the conductive layer, and the projection width M1 of the first insulating layer on the negative electrode side on the positive electrode side is 4mm; a second insulating layer is provided on the positive electrode side, which is arranged around the positive electrode film layer, and the width M2 of the second insulating layer on the positive electrode side is 10mm, the conductive layer coating area on the negative electrode side is 100mm wide, and the positive electrode film coating area on the positive electrode side is 88mm wide.

[0160] Electrolyte: The electrolyte is 0.5 mol / L NaPF6 / (EC+DMC, volume ratio is 1:1).

[0161] Diaphragm: PE porous polymer film is used as the isolation membrane.

[0162] The above-mentioned bipolar electrodes, diaphragm and electrolyte are assembled into a button battery in a button battery box.

[0163] Compression of bipolar pole pieces: Take a film layer of a specific area and weigh its mass, divide the mass of the film layer by the taken area to calculate the surface density; divide the calculated surface density by the thickness of the film layer to get the compression of the pole piece.

[0164] The compositions of the bipolar electrodes of Examples 21 to 25 are slightly adjusted relative to Example 20, as shown in Table 2.

[0165] The cycle performance test is the same as the above method.

[0166] The test results are recorded in Table 2.

[0167] Table 2

[0168] Comparing the data in Table 2, it can be seen that the provision of a first insulating layer and a second insulating layer can significantly improve the cycling performance of the battery, and the improvement in cycling performance is particularly significant when the width of the first insulating layer is smaller than that of the second insulating layer. However, in Example 23, the widths of the first insulating layer and the second insulating layer are both larger, and the difference is also large. Although the cycling performance is significantly improved, the energy density of the battery decreases due to the increased proportion of the insulating layer.

[0169] Example 26

[0170] Aluminum foil is used as the current collector, and a 150 μm thick positive electrode film is coated on one side. In the positive electrode film, the positive electrode active material is sodium iron pyrophosphate, the conductive agent is conductive carbon, and the binder is PDVF; the mass ratio of the three is 95:2:3, and the formed positive electrode film is the same as the positive electrode film in Example 1; the other side is a rough surface with a roughness of It has a negative electrode sodium deposition area; polyvinylidene fluoride is used as the insulating layer raw material, and a first insulating layer is provided on the negative electrode side, which is arranged around the negative electrode sodium deposition area, and the projection width M1 of the first insulating layer on the negative and positive electrode sides on the positive electrode side is 4mm; a second insulating layer is provided on the positive electrode side, which is arranged around the positive electrode film layer, and the width M2 of the second insulating layer on the positive and negative electrode sides is 10mm, the negative electrode sodium deposition area on the negative electrode side is 100mm wide, and the positive electrode film layer coating area on the positive electrode side is 88mm wide.

[0171] Electrolyte: The electrolyte contains 0.5 mol / L NaPF6, the solvent is EC+DMC, and the volume ratio of EC to DMC is 1:1.

[0172] Diaphragm: PE porous polymer film is used as the isolation membrane.

[0173] The above-mentioned bipolar electrodes, diaphragm and electrolyte are assembled into a button battery in a button battery box.

[0174] Compression of bipolar pole pieces: Take a film layer of a specific area and weigh its mass, divide the mass of the film layer by the taken area to calculate the surface density; divide the calculated surface density by the thickness of the film layer to get the compression of the pole piece.

[0175] The compositions of the bipolar electrodes of Examples 27 to 31 are slightly adjusted relative to Example 26, as shown in Table 3.

[0176] The cyclic performance test is the same as the above method.

[0177] The test results are recorded in Table 3.

[0178] Table 3

[0179] According to the comparison of the data in Table 2 and Table 3, it can be found that the cycle performance of Table 2 is better, but the rules of Table 2 and Table 3 are the same.

[0180] Example 32

[0181] One side of the Al current collector is plated with nickel and then plated with Cu to form a composite current collector. A 150 μm thick positive electrode film layer is coated on one side of the current collector with a surface density of 0.200 mg / mm 2 , lithium-free gram capacity is 150mAh / g, and positive electrode loading is 98%; the coating surface on the other side is 200μm thick, the negative electrode active material of the negative electrode film layer is hard carbon, the conductive agent is conductive carbon, and the binder is CMC; the mass ratio of the three is 95:2:3; polyvinylidene fluoride is used as the insulating layer raw material, and a first insulating layer is provided on the negative electrode side, which is arranged around the negative electrode film layer, and the projection width M1 of the first insulating layer on the negative electrode side on the positive electrode side is 4mm; a second insulating layer is provided on the positive electrode side, which is arranged around the positive electrode film layer, and the width M2 of the second insulating layer on the positive electrode side is 10mm, the coating area of ​​the negative electrode film layer on the negative electrode side is 100mm wide, and the coating area of ​​the positive electrode film layer on the positive electrode side is 88mm wide.

[0182] Electrolyte: The electrolyte contains 0.5 mol / L LiPF6, the solvent is EC+DMC, and the volume ratio of EC to DMC is 1:1.

[0183] Diaphragm: PE porous polymer film is used as the isolation membrane.

[0184] The above-mentioned bipolar electrodes, diaphragm and electrolyte are assembled into a button battery in a button battery box.

[0185] Use a micrometer to measure the thickness of the positive electrode film layer, the width and thickness of the first insulating layer, and the width and thickness of the second insulating layer;

[0186] Take a specific area of ​​the film layer and weigh its mass, and divide the mass of the film layer by the taken area to calculate the surface density.

[0187] The compaction of the positive electrode active material and the compaction of the negative electrode active material were tested using an electronic pressure testing machine model UTM7305, and the measurements were performed under specified pressures, wherein the compaction of the positive electrode active material was tested under a pressure of 3t, and the compaction of the negative electrode active material was tested under a pressure of 2t.

[0188] Compression of bipolar pole piece: The calculated surface density is divided by the thickness of the film layer to obtain the compression of the pole piece.

[0189] Test of gram capacity T1 of negative electrode active material in negative electrode film layer:

[0190] The above-mentioned negative electrode plate, separator, and lithium sheet were assembled and charged to perform a gram capacity test of the negative electrode active material.

[0191] Within the rated charge and discharge range (generally 0.005V~2.5V), charge at a constant current rate of 0.33C to the full charge voltage (0.005V), and then charge at a constant voltage (full charge voltage) until the current reaches 0.05C. Integrate the charging current and charging time to obtain the charging capacity, and then divide it by the mass of the negative electrode active material (negative electrode coating mass * negative electrode active material loading) to obtain the gram capacity of the negative electrode active material.

[0192] Test of gram capacity T2 of positive electrode active material in positive electrode film layer:

[0193] The above-mentioned positive electrode plate, separator, and lithium plate are assembled and charged to perform a gram capacity test of the positive electrode active material.

[0194] Within the rated charge and discharge range (the upper and lower limits are determined by the specific positive electrode material), charge at a constant current rate of 0.33C to the full charge voltage, and then charge at a constant voltage (full charge voltage) until the current reaches 0.05C. Integrate the charging current and charging time to obtain the charging capacity, and then divide it by the mass of the positive electrode active material (positive electrode coating mass * positive electrode active material loading) to obtain the gram capacity of the positive electrode active material.

[0195] The compositions of the bipolar electrodes of Examples 33 to 38, Examples 41 and 42 are slightly adjusted relative to Example 32, as shown in Table 4 for details.

[0196] Example 39

[0197] The bipolar electrode is the same as that in Example 32. The insulating layer parameters M1 and M2 are shown in Table 4. The electrolyte is a polyethylene oxide gel electrolyte: the ratio of PEO to Na ions is 15:1. PEO and sodium hexafluorophosphate are mixed and dissolved in tetrahydrofuran, dried to form an electrolyte membrane, spread flat on the surface of the electrode to shape it, and then further dried.

[0198] Example 40

[0199] The first insulating layer and the second insulating layer are not provided in the bipolar electrode, and the rest is the same as in Example 47.

[0200] Examples 43 and 44

[0201] The compositions of the bipolar electrodes of Examples 43 and 44 are slightly adjusted relative to those of Example 39, as shown in Table 4.

[0202] Performance testing:

[0203] The test methods for cycle performance are the same as the above methods.

[0204] The test results are recorded in Table 4.

[0205] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A bipolar battery, comprising n stacked bipolar electrodes, where n>1, the bipolar electrodes comprising: current collector; A positive electrode film layer is arranged on one side of the current collector, the side of the current collector provided with the positive electrode film layer is the positive electrode side, and the side opposite to the positive electrode side is the negative electrode side; The negative electrode side is optionally provided with a negative electrode film layer or a conductive layer.

2. The bipolar battery according to claim 1, wherein: When the bipolar electrode has the negative electrode film layer, the CB value of the bipolar electrode is 1.05 (n-1) ~1.1 n , CB value = (A × T1 × S1) / (C × T2 × S2), Among them, A is the surface density of the negative electrode film layer, T1 is the gram capacity of the negative electrode active material in the negative electrode film layer, S1 is the loading amount of the negative electrode active material in the negative electrode film layer, C is the surface density of the positive electrode film layer, T2 is the gram capacity of the positive electrode active material in the positive electrode film layer, and S2 is the loading amount of the positive electrode active material in the positive electrode film layer.

3. The bipolar battery according to claim 2, wherein: 1＜n≤200。 4. The bipolar battery according to any one of claims 1 to 3, wherein: The bipolar electrode has the negative electrode film layer, and the bipolar electrode further comprises: A first insulating layer is arranged on the negative electrode side of the current collector, and the first insulating layer extends from the negative electrode film layer to the edge of the current collector; The second insulating layer is arranged on the positive electrode side of the current collector, and the second insulating layer extends from the positive electrode film layer to the edge of the current collector.

5. The bipolar battery according to claim 4, wherein: The thickness of the negative electrode film layer is a, the thickness of the positive electrode film layer is c, the thickness of the first insulating layer is d1, the thickness of the second insulating layer is d2, a≤d1≤1.1a and / or c≤d2≤1.1c.

6. The bipolar battery according to claim 1, wherein: The bipolar electrode is a bipolar electrode without a negative electrode, and the bipolar electrode includes a conductive layer arranged on the negative electrode side of the current collector, and the bipolar electrode further includes: A first insulating layer, disposed on the negative electrode side of the current collector, the first insulating layer extending from the conductive layer to the edge of the current collector; The second insulating layer is arranged on the positive electrode side of the current collector, and the second insulating layer extends from the positive electrode film layer to the edge of the current collector.

7. The bipolar battery according to any one of claims 1 to 6, wherein: The thickness of the positive electrode film layer is c, and the thickness of the conductive layer is less than c.

8. The bipolar battery according to claim 6, wherein: The thickness of the positive electrode film layer is c, the thickness of the first insulating layer is d1, the thickness of the second insulating layer is d2, c≤d1≤1.1c and / or c≤d2≤1.1c.

9. The bipolar battery according to claim 1, wherein: The bipolar electrode is a bipolar electrode without a negative electrode, a negative electrode sodium deposition area is provided on the negative electrode side of the bipolar electrode, and the bipolar electrode further comprises: A first insulating layer is disposed on the negative electrode side of the current collector, and the first insulating layer extends from the negative electrode sodium deposition area to the edge of the current collector; A second insulating layer is disposed on the positive electrode side of the current collector, and the second insulating layer extends from the positive electrode film layer to the edge of the current collector; The thickness of the positive electrode film layer is c, the thickness of the first insulating layer is d1, the thickness of the second insulating layer is d2, c≤d1≤2c and / or c≤d2≤2c.

10. The bipolar battery according to any one of claims 1 to 9, wherein: The electrolyte is a liquid electrolyte.

11. The bipolar battery according to claim 10, wherein: The bipolar battery further includes a first insulating layer and a second insulating layer, wherein the first insulating layer is disposed on the negative electrode side of the current collector, and the second insulating layer is disposed on the positive electrode side of the current collector, and a projected area of ​​the first insulating layer on the positive electrode side is smaller than an area of ​​the second insulating layer.

12. The bipolar battery according to claim 11, wherein: The extension direction from the positive electrode film layer to the edge of the current collector is defined as the width direction of the first insulating layer and the second insulating layer, and the projection width M1 of the first insulating layer on the positive electrode side is smaller than the width M2 of the second insulating layer.

13. The bipolar battery according to claim 12, wherein: M2-M1 is between 2mm and 10mm.

14. The bipolar battery according to any one of claims 1 to 9, wherein: The electrolyte is a fully solid electrolyte or a gel electrolyte.

15. The bipolar battery according to claim 14, wherein: The electrolyte is a gel polymer electrolyte.

16. The bipolar battery according to claim 15, wherein: The electrolyte includes any one or more of polyethylene oxide gel electrolyte, polyacrylonitrile gel electrolyte, polymethyl methacrylate gel electrolyte, and polyvinylidene fluoride gel electrolyte.

17. The bipolar battery according to any one of claims 1 to 16, wherein: p1 is the compaction of the negative electrode powder used in the negative electrode film layer under a pressure of 2t; p2 is the compaction of the positive electrode powder used in the positive electrode film layer under a pressure of 3t, min is the minimum value between P1 and P2, p max is the maximum value of P1 and P2, the compaction of the bipolar electrode is p, p satisfies p min ≤p≤1.2p max .

18. The bipolar battery according to any one of claims 1 to 17, wherein: The bipolar battery is a sodium ion battery, and the current collector of the bipolar electrode comprises aluminum foil, stainless steel foil, and a polymer material substrate or copper foil with a double-sided metal coating; or The bipolar battery is a lithium ion battery, and the current collector of the bipolar electrode comprises a stainless steel foil, an aluminum-copper composite foil, or a polymer foil with aluminum or copper plated at both ends.

19. The bipolar battery according to claim 18, wherein: The sodium ion battery has one or more of the following characteristics: 1) The positive electrode active material in the positive electrode film layer is sodium vanadium phosphate; 2) In the bipolar electrode, the negative electrode side of the current collector is uncoated and the negative electrode side is rough. The conductive layer is provided on the negative electrode side of the current collector, or the negative electrode side of the current collector has a negative electrode film layer; 3) When the negative electrode side of the current collector has a negative electrode film layer, the negative electrode active material in the negative electrode film layer is hard carbon.

20. An electrical device comprising a secondary battery, wherein: The secondary battery is the bipolar battery according to any one of claims 1 to 19.

Images