Pole core, battery, battery pack and electric device

Abstract

This invention provides an electrode core, a battery, a battery pack, and an electrical device. The electrode core comprises N1 stacked units arranged sequentially along the thickness direction, where N1 ≥ 2. Each stacked unit includes a positive electrode sheet and a negative electrode sheet stacked on top of each other. Along the thickness direction of the electrode core, it is divided into a central region and edge regions located on opposite sides of the central region. The positive electrode sheet in the central region is the first positive electrode sheet, and the positive electrode sheet in the edge regions is the second positive electrode sheet. The areal density of the first positive electrode sheet is higher than that of the second positive electrode sheet. This invention can effectively improve the uniformity of stress distribution between electrode core layers, reduce the protrusion height of the electrode core edges, and strengthen the adhesion of the interfaces within the electrode core, thereby significantly improving the cycle performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to an electrode core, a battery, a battery pack, and an electrical device. Background Technology

[0002] Solid-state batteries, as a new generation of high-energy-density energy storage devices, are widely used in new energy electric vehicles, aerospace, energy storage systems, and consumer electronics with high safety requirements. Their core advantage lies in replacing liquid electrolytes with solid electrolytes, significantly improving battery safety (avoiding the risks of thermal runaway and electrolyte leakage), while also supporting the application of higher energy density (>400 Wh / kg) electrode materials (such as high-nickel cathodes and lithium metal anodes). In the design of all-solid-state batteries with multi-layer electrode stacking, densification of the electrode core is achieved through lamination processes (such as isostatic pressing) to reduce interfacial impedance and improve electrochemical performance. However, in the process of multi-layer electrode stacking, existing technologies suffer from uneven interlayer stress distribution and poor interfacial contact due to unreasonable electrode areal density design, which severely restricts the cycle life and assembly yield of solid-state batteries. Summary of the Invention

[0003] This invention provides an electrode core, a battery, a battery pack, and an electrical device, which can at least solve problems such as uneven interlayer stress distribution, electrode core edge protrusion, and poor interface contact caused by unreasonable electrode surface density design during the multi-layer electrode stacking process.

[0004] This invention provides an electrode core comprising N1 stacked units stacked sequentially along the thickness direction, wherein N1 ≥ 2, and each stacked unit includes a positive electrode sheet and a negative electrode sheet stacked on top of each other; along the thickness direction of the electrode core, the electrode core is divided into a central region and edge regions located on opposite sides of the central region; the positive electrode sheet in the central region is a first positive electrode sheet, and the positive electrode sheet in the edge regions is a second positive electrode sheet; the areal density of the first positive electrode sheet is higher than that of the second positive electrode sheet.

[0005] According to one embodiment of the present invention, the edge region includes a first edge region and a second edge region, the first edge region and the second edge region being symmetrically arranged with the middle region as the center of symmetry; and / or, the ratio of the single-sided surface density of the first positive electrode to the single-sided surface density of the second positive electrode is (1.05~1.25):(0.85~0.95).

[0006] According to one embodiment of the present invention, the areal density of the first positive electrode sheet is 23~25 mg / cm³. 2 ; and / or, the areal density of the second positive electrode is 17~22 mg / cm³. 2; and / or, the thickness of the first positive electrode is 120~300μm; and / or, the thickness of the second positive electrode is 90~225μm; and / or, the thickness of the negative electrode is 20~200μm.

[0007] According to one embodiment of the present invention, the ratio of the total number of layers of the first positive electrode to the total number of layers of the first positive electrode and the second positive electrode is 1:(2.5~5).

[0008] According to one embodiment of the present invention, the ratio of the total number of layers of the first positive electrode to the total number of layers of the first positive electrode and the second positive electrode is 1:(3.5~4.5).

[0009] According to one embodiment of the present invention, the edge region includes N2 sub-edge regions distributed along the thickness direction of the electrode core, wherein N2≥1, and the surface density of the positive electrode sheet in the sub-edge regions decreases sequentially along the direction from the middle region to the edge region.

[0010] According to one embodiment of the present invention, the stacked unit further includes an electrolyte layer located between the positive electrode and the negative electrode; preferably, the thickness of the electrolyte layer is 10~40μm.

[0011] The present invention also provides a battery, including the above-described electrode core; preferably, the battery is a solid-state battery.

[0012] The present invention also provides a battery pack comprising at least two batteries as described above that are interconnected.

[0013] The present invention also provides an electrical device, including the battery or the battery pack described above.

[0014] This invention provides an electrode core, a battery, a battery pack, and an electrical device. The electrode core comprises N1 alternately stacked units, where N1 ≥ 2. Each stacked unit includes a positive electrode sheet and a negative electrode sheet stacked on top of each other. Along the thickness direction of the electrode core, it is divided into a central region and edge regions located on opposite sides of the central region. The positive electrode sheet in the central region is a first positive electrode sheet, and the positive electrode sheet in the edge regions is a second positive electrode sheet. The areal density of the first positive electrode sheet is higher than that of the second positive electrode sheet. On the one hand, the use of a high areal density first positive electrode sheet in the central region allows for sufficient compression space to absorb the excessive shrinkage of the low areal density second positive electrode sheet in the edge regions during the isostatic pressing process, thus compensating for the difference in interlayer shrinkage rate in different regions of the electrode core and effectively suppressing edge bulging defects that occur after isostatic pressing. On the other hand, the second positive electrode sheet in the edge regions can be matched with a formulation design with a higher binder ratio, which can improve the edge anti-detachment ability and reduce the probability of slippage and folding of the outer electrode sheet and electrolyte membrane during isostatic pressing. Therefore, the present invention can effectively improve the uniformity of stress distribution between electrode core layers, reduce the protrusion height of electrode core edges, and strengthen the tightness of the bonding between various interfaces inside the electrode core, thereby significantly improving the cycle performance of the battery. Attached Figure Description

[0015] Figure 1 This is a regional distribution diagram of the electrode core in one embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of the electrode core in one embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of the pole core structure in Embodiment 5 of the present invention;

[0018] Figure 4 These are graphs showing the height of the protrusions at the edge of the electrode core in Embodiments 1, 2, 6, and 7 of the present invention.

[0019] Figure 5 This is a schematic diagram of the edge protrusion height of the electrode core in an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures:

[0021] 1-Second positive electrode plate; 2-First positive electrode plate; 3-Negative electrode plate; 4-First edge region; 5-Middle region; 6-Second edge region; 7-Third sub-edge region; 8-Fourth sub-edge region; 9-Fifth sub-edge region; 10-Sixth sub-edge region; 11-Seventh sub-edge region; 12-Eighth sub-edge region; h-Edge core edge protrusion height. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In related technologies, during the stacking of multi-layer electrodes, problems such as uneven stress distribution and poor interface contact between electrode cores due to unreasonable electrode surface density design seriously restrict the cycle life and assembly yield of solid-state batteries, which urgently need to be solved.

[0024] In view of this, embodiments of the present invention provide an electrode core comprising N1 stacked units sequentially stacked along the thickness direction, where N1 ≥ 2, and each stacked unit comprising a positive electrode sheet and a negative electrode sheet stacked together; as shown Figure 1 As shown, along the thickness direction of the electrode core, the electrode core is divided into a central region 5 and two edge regions located on either side of the central region 5 (i.e., Figure 1 The first edge region 4 and the second edge region 6 are in the middle region 5. The positive electrode in the middle region 5 is the first positive electrode 2, and the positive electrode in the edge region is the second positive electrode 1. The surface density of the first positive electrode 2 is higher than that of the second positive electrode 1.

[0025] Based on the above-mentioned core structure design, the uniformity of stress distribution between core layers can be effectively improved, the edge protrusion height of the core can be reduced, and the adhesion of interfaces within the core can be strengthened, thereby significantly improving the cycle performance of the battery. The reasons are as follows: 1) The high areal density of the first positive electrode sheet in the middle region allows for sufficient compression space to absorb the excessive shrinkage of the low areal density second positive electrode sheet in the edge region during the isostatic pressing process, compensating for the difference in interlayer shrinkage rates in different regions of the core, thus effectively suppressing edge protrusion defects that occur after isostatic pressing. 2) The low areal density of the second positive electrode sheet in the edge region can be matched with a formulation design with a higher binder ratio, improving the edge region's resistance to detachment, while reducing the risk of material accumulation and detachment at the edge of the high areal density first positive electrode sheet. 3) The gradient design of the areal density on one side can effectively reduce the interlayer height difference (i.e., the edge protrusion height of the core), reducing the probability of slippage and folding of the outer electrode sheet and electrolyte membrane during isostatic pressing, and avoiding material loss and protrusion caused by interface separation. Therefore, the present invention can effectively improve the uniformity of stress distribution between electrode core layers and strengthen the adhesion of interfaces inside the electrode core, thereby significantly improving the cycle performance of the battery.

[0026] For example, N1 can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, etc.

[0027] In this embodiment of the invention, the areal density of the first positive electrode refers to the total mass of the positive active material layer on one side per unit coating area in the first positive electrode. The areal density of the second positive electrode refers to the total mass of the positive active material layer on one side per unit coating area in the second positive electrode.

[0028] In embodiments of the present invention, such as Figure 1 As shown, the edge region includes a first edge region 4 and a second edge region 6, which are symmetrically arranged with the middle region 5 as the center of symmetry. The symmetrical arrangement of the two edge regions on either side of the middle region ensures that stress is uniformly transmitted in the direction of the electrode core thickness, avoiding the problem of relative expansion of the middle region due to excessive contraction of the edge regions, reducing interface impedance fluctuations, and thus further improving the cycle performance of the battery.

[0029] In this embodiment of the invention, each stacked unit in the middle region 5 of the electrode core includes a first positive electrode 2 and a negative electrode 3 stacked on top of each other. In the first edge region 4 and the second edge region 6 of the electrode core, each stacked unit includes a second positive electrode 1 and a negative electrode 3 stacked on top of each other. The negative electrode 3 in the first edge region 4, the second edge region 6, and the middle region 5 all have the same structural composition.

[0030] In some implementations, such as Figure 2 As shown, the first edge region 4 contains two stacked units (each stacked unit includes a second positive electrode 1 and a negative electrode 3 stacked on top of each other), the second edge region 6 contains two stacked units (each stacked unit includes a first positive electrode 2 and a negative electrode 3 stacked on top of each other), and the middle region 5 contains two stacked units (each stacked unit includes a second positive electrode 1 and a negative electrode 3 stacked on top of each other).

[0031] In this embodiment of the invention, the ratio of the single-sided areal density of the first positive electrode to the single-sided areal density of the second positive electrode is (1.05~1.25):(0.85~0.95), which helps to better improve the uniformity of stress distribution between the electrode core layers, strengthen the tightness of the bonding between the interfaces inside the electrode core, and further improve the cycle performance of the battery.

[0032] For example, the ratio of the areal density of the first positive electrode to the areal density of the second positive electrode can be 1.05:0.85, 1.05:0.9, 1.05:0.95, 1.1:0.85, 1.1:0.9, 1.1:0.95, 1.15:0.85, 1.15:0.9, 1.15:0.95, 1.2:0.85, 1.2:0.9, 1.2:0.95, 1.25:0.85, 1.25:0.9, or 1.25:0.95, etc.

[0033] In some embodiments, the areal density of the first positive electrode is 23~25 mg / cm³. 2 The areal density of the second positive electrode is 17~22 mg / cm³. 2 This helps to improve the uniformity of stress distribution between electrode core layers, strengthen the adhesion of interfaces inside the electrode core, and further improve the cycle performance of the battery.

[0034] For example, the areal density of the first positive electrode can be 23 mg / cm³. 2 23.5 mg / cm 2 24mg / cm 2 24.5 mg / cm 2 Or 25mg / cm 2 wait.

[0035] For example, the areal density of the second positive electrode can be 17 mg / cm³. 2 18mg / cm 2 19mg / cm 2 20mg / cm 2 21mg / cm 2 Or 22mg / cm 2 wait.

[0036] In this embodiment of the invention, the surface density of the positive electrode sheet can be controlled by conventional processes in the art. Exemplary adjustment methods include adjusting the coating flow rate of the positive electrode slurry and optimizing the solid content of the positive electrode slurry.

[0037] In this embodiment of the invention, by adjusting the thickness of the first positive electrode, the second positive electrode, and the negative electrode, the uniformity of stress distribution between the electrode core layers is improved, the adhesion between the interfaces inside the electrode core is strengthened, and the cycle performance of the battery is further enhanced. In some embodiments, the thickness of the first positive electrode is 120~300μm, the thickness of the second positive electrode is 90~225μm, and the thickness of the negative electrode is 20~200μm.

[0038] For example, the thickness of the first positive electrode can be 120μm, 150μm, 200μm, 250μm or 300μm, etc.

[0039] For example, the thickness of the second positive electrode can be 90μm, 100μm, 150μm, 200μm or 225μm, etc.

[0040] For example, the thickness of the negative electrode can be 20μm, 50μm, 100μm, 150μm or 200μm, etc.

[0041] In this embodiment of the invention, the first positive electrode sheet includes a first positive current collector and a first positive active material layer. The thickness of the first positive electrode sheet refers to the sum of the thickness of the first positive current collector and the thickness of the first positive active material layer.

[0042] In this embodiment of the invention, the second positive electrode sheet includes a second positive current collector and a second positive active material layer. The thickness of the second positive electrode sheet refers to the sum of the thickness of the second positive current collector and the thickness of the second positive active material layer.

[0043] In this embodiment of the invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the thickness of the negative electrode sheet refers to the sum of the thickness of the negative electrode current collector and the thickness of the negative electrode active material layer.

[0044] In some embodiments, the ratio of the total number of layers of the first positive electrode to the total number of layers of the first and second positive electrode is 1:(2.5~5). This helps to better improve the uniformity of stress distribution between electrode core layers, strengthen the adhesion of interfaces within the electrode core, and further improve the cycle performance of the battery.

[0045] For example, the ratio of the total number of layers of the first positive electrode to the total number of layers of the first positive electrode and the second positive electrode can be 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, etc.

[0046] In some embodiments, the ratio of the total number of layers of the first positive electrode to the total number of layers of the first positive electrode and the second positive electrode can be 1:(3.5~4.5).

[0047] For example, the ratio of the total number of layers of the first positive electrode to the total number of layers of the first positive electrode and the second positive electrode can be 1:3.5, 1:3.7, 1:3.9, 1:4.1, 1:4.3 or 1:4.5, etc.

[0048] In some embodiments, the edge region includes N2 sub-edge regions distributed along the thickness direction of the electrode core, where N2≥1, and the surface density of the positive electrode sheet in the sub-edge regions decreases sequentially from the middle region to the edge region.

[0049] For example, N2 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, etc.

[0050] In this embodiment of the invention, in two adjacent sub-edge regions, the difference between the surface density of the positive electrode sheet near the center and the surface density of the positive electrode sheet far from the center is ≤2%. This is beneficial for improving the uniformity of stress distribution between electrode core layers, strengthening the adhesion of interfaces within the electrode core, and further improving the cycle performance of the battery. The surface density difference percentage = (|ρ1-ρ2| / ρ1) × 100%, where ρ1 is the surface density of the positive electrode sheet in the sub-edge region near the center, and ρ2 is the surface density of the positive electrode sheet in the sub-edge region far from the center.

[0051] In this embodiment of the invention, the stacked unit further includes an electrolyte layer, which is located between the positive electrode and the negative electrode.

[0052] In some implementations, the electrolyte layer and the negative electrode sheet are collectively referred to as the negative electrode composite sheet.

[0053] Generally, the electrolyte layer includes a solid electrolyte, which includes a sulfide solid electrolyte. The sulfide solid electrolyte can be a conventional sulfide solid electrolyte in the art, such as Li3PS4, but is not limited to Li3PS4; it can also be other binary sulfide electrolytes, ternary sulfide electrolytes, sulfide-germanium sulfide electrolytes, etc. Specifically, the sulfide solid electrolyte can also be Li6PS5X (where X is one or more of Cl, Br, and I), lithium sulfide superionic conductors, Li... 11-x M 2-x P 1+x S 12 (Where M is one or more of Ge, Sn, and Si). Li6PS5X may include, for example, [missing information - likely related to alloy composition]. .

[0054] The present invention also provides a battery comprising the electrode core as described above, which has advantages corresponding to the electrode core described above, and will not be described in detail hereafter.

[0055] Generally, the electrode sheet includes a current collector and an electrode active material layer disposed on at least one side of the current collector. The electrode active material layer includes the binder described above or a binder prepared according to the preparation method described above. Specifically, the electrode active material layer may be located only on one side of the current collector, or it may be disposed on both opposite sides of the current collector (i.e., on both the front and back surfaces of the current collector).

[0056] Generally, the electrode active material layer also includes a binder, a solid electrolyte, and a conductive agent. The binder in the electrode active material layer has a mass percentage of 1% to 2.5%, for example, 1%, 1.3%, 1.5%, 1.7%, 1.9%, 2.1%, 2.3%, or 2.5%. The mass percentage of the electrode active material can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof. The mass percentage of the solid electrolyte can be 10% to 30%, for example, 10%, 15%, 20%, 25%, 30%, or any combination thereof.

[0057] When the electrode sheet is a positive electrode sheet, the electrode current collector is a positive electrode current collector, the electrode active material layer is a positive electrode active material layer, and the electrode active material is a positive electrode active material.

[0058] In this embodiment of the invention, the solid electrolyte in the positive electrode active material layer includes a sulfide solid electrolyte. The sulfide solid electrolyte can be a conventional sulfide solid electrolyte in the art, such as Li3PS4, but not limited to Li3PS4; it can also be other binary sulfide electrolytes, ternary sulfide electrolytes, sulfogermanium sulfide electrolytes, etc. Specifically, the sulfide solid electrolyte can also be Li6PS5X (where X is one or more of Cl, Br, and I), lithium sulfide superionic conductors, Li... 11-x M 2-x P 1+x S 12 (where M is one or more of Ge, Sn, and Si).

[0059] The positive electrode active material in the positive electrode active material layer can be a ternary material, lithium iron phosphate, or lithium manganese iron phosphate, etc. The binder includes one or more of the following: polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0060] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0061] In this embodiment of the invention, the first positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the positive electrode active material layer, such as the first positive electrode active material, solid electrolyte, conductive agent, and binder, can be dispersed in a solvent (i.e., homogenized) to prepare a first positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the first positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0062] In this embodiment of the invention, the second positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the positive electrode active material layer, such as the second positive electrode active material, solid electrolyte, conductive agent, and binder, can be dispersed in a solvent (i.e., homogenized) to prepare a second positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the second positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0063] In this embodiment of the invention, the solid content of the first positive electrode slurry is 50%~80%.

[0064] For example, the solid content of the first positive electrode slurry can be 50%, 55%, 60%, 65%, 70%, 75%, or 80%, etc.

[0065] In this embodiment of the invention, the solid content of the second positive electrode slurry is 50%~80%.

[0066] For example, the solid content of the second positive electrode slurry can be 50%, 55%, 60%, 65%, 70%, 75%, or 80%, etc.

[0067] In this embodiment of the invention, during the preparation of the first positive electrode sheet, the coating flow rate of the first positive electrode slurry is 210~230g / min, which is beneficial to adjust the surface density of the first positive electrode sheet, thereby better improving the uniformity of stress distribution between the core layers, strengthening the tightness of the bonding between the interfaces inside the core, and further improving the cycle performance of the battery.

[0068] In this embodiment of the invention, during the preparation of the second positive electrode sheet, the coating flow rate of the second positive electrode slurry is 160~200g / min, which is beneficial to adjust the single-sided surface density of the second positive electrode sheet, thereby better improving the uniformity of stress distribution between the core layers, strengthening the tightness of the bonding between the interfaces inside the core, and further improving the cycle performance of the battery.

[0069] In this embodiment of the invention, the coating tolerance of the single-sided surface density of the positive electrode sheet is controlled to be ±1.5% during the coating process. The single-sided surface density coating tolerance refers to the relative deviation between the actual single-sided surface density of the positive electrode sheet and the preset single-sided surface density, that is, the single-sided surface density coating tolerance = (|actual single-sided surface density of the positive electrode sheet - preset single-sided surface density| ÷ preset single-sided surface density) × 100%.

[0070] When the electrode sheet is a negative electrode sheet, the electrode current collector is a negative electrode current collector, the electrode active material layer is a negative electrode active material layer, and the electrode active material is a negative electrode active material.

[0071] In this embodiment of the invention, the negative electrode active material layer may include a metal element-type negative electrode active material layer, for example, a lithium metal layer.

[0072] In this embodiment of the invention, the binder in the negative electrode active material layer may include at least one of polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), tetrafluoroethylene and its multi-component copolymers, polyvinylidene fluoride and its multi-component copolymers, polyolefins and their multi-component copolymers (e.g., polyethylene, polypropylene, polyethylene-polyethylene glycol block copolymers, etc.), polyvinyl alcohol, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, nitrile rubber, polyacrylic acid (PAA), and polyacrylates (such as sodium polyacrylate).

[0073] Furthermore, the negative electrode active material can be a conventional negative electrode active material in the art. For example, conventional negative electrode active materials may include one or more of graphite, pure silicon, and silicon carbide, but are not limited thereto.

[0074] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0075] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the negative electrode active layer, such as the negative electrode active material, solid electrolyte, conductive agent, and binder, can be dispersed in the solvent toluene (i.e., homogenized) to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0076] In addition, the conductive agent in the electrode active material layer (positive electrode active material layer, negative electrode active material layer) can be a conventional conductive material in the art. For example, the conductive agent may include one or more of carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber.

[0077] This invention also provides a battery comprising the electrode sheet and / or the electrolyte membrane described above. This battery has advantages corresponding to the electrode core described above, which will not be elaborated further.

[0078] In this embodiment of the invention, the battery includes a solid-state battery. Generally, a solid-state battery includes a cell and a casing for encapsulating the cell. The cell includes a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive and negative electrode. The cell can be a stacked cell, meaning the cell is formed by alternating layers of the positive electrode, solid electrolyte layer, and negative electrode; or it can be a wound cell, meaning the cell is formed by stacking and winding the positive electrode, solid electrolyte layer, and negative electrode.

[0079] This invention also provides a method for preparing a solid-state battery, comprising the following steps: sequentially stacking a positive electrode sheet, a solid electrolyte layer, and a negative electrode sheet to obtain a stacked cell. After the cell stacking is completed, the cell is pressed into shape under a certain pressure, and then tabs are welded to obtain a solid-state battery.

[0080] In this embodiment of the invention, the alignment accuracy between layers is strictly controlled during the stacking process to ensure that the alignment deviation of each layer of positive electrode sheet and negative electrode composite sheet is ≤ ±0.3mm, resulting in an unpressed electrode core. The alignment deviation of the positive electrode sheet and negative electrode composite sheet ≤ ±0.3mm means that the maximum offset between any layer of positive electrode sheet (including the first positive electrode sheet and the second positive electrode sheet) and the negative electrode composite sheet cannot exceed 0.3mm.

[0081] This invention also provides a battery pack comprising at least two batteries as described above that are interconnected. This battery pack has advantages corresponding to the batteries described above, which will not be elaborated further.

[0082] The battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0083] This invention also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the battery described above, which will not be elaborated further.

[0084] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0085] The present invention will be further described below through specific embodiments.

[0086] Example 1

[0087] 1. Preparation of negative electrode composite sheet

[0088] A layer of metallic lithium (i.e., the negative electrode active material layer) is electroplated on both sides of the copper foil of the negative electrode current collector. A first negative electrode active material layer and a second negative electrode active material layer are formed on the two surfaces of the copper foil, respectively. Then, a roller dry coating machine is used to form a layer on the side of the first negative electrode active material layer away from the copper foil through a dry coating process (coating speed of 2m / min). The first electrolyte layer is formed on the side of the second negative electrode active material layer opposite to the copper foil. The second electrolyte layer is then dried at 80°C for 10 minutes to obtain the negative electrode composite sheet.

[0089] The negative electrode composite sheet comprises a first electrolyte layer, a first negative electrode active material layer, a copper foil, a second negative electrode active material layer, and a second electrolyte layer, which are stacked sequentially. The thickness of the first negative electrode active material layer is 40 μm, the thickness of the second negative electrode active material layer is 40 μm, the thickness of the first electrolyte layer is 20 μm, and the thickness of the second electrolyte layer is 20 μm.

[0090] 2. Preparation of the positive electrode sheet

[0091] The first positive electrode (i.e., the high-area-density positive electrode): The positive electrode active material... Sulfide electrolytes PVDF is dispersed in NMP at a mass ratio of 95:4:1 and stirred under vacuum for 2 hours to form the first positive electrode slurry (solid content of 52%). The first positive electrode slurry is uniformly coated on both sides of the positive electrode current collector aluminum foil, and then dried, rolled, and die-cut to obtain the first positive electrode sheet.

[0092] The first positive electrode sheet has a single-sided areal density of 23 mg / cm², and comprises a first sub-positive electrode active material layer, an aluminum foil, and a second sub-positive electrode active material layer stacked sequentially. The thickness of the first sub-positive electrode active material layer is 100 μm, the thickness of the aluminum foil is 13 μm, and the thickness of the second sub-positive electrode active material layer is 100 μm. The coating flow rate of the first positive electrode slurry is 220 g / min.

[0093] The second positive electrode (i.e., the low-area-density positive electrode): The positive electrode active material... Sulfide electrolytes PVDF was dispersed in NMP at a mass ratio of 95:4:1 and stirred under vacuum for 2 hours to form a second positive electrode slurry (solid content of 52%). This second positive electrode slurry was uniformly coated onto both sides of the aluminum foil used as the positive electrode current collector. After drying, rolling, and die-cutting, a second positive electrode sheet was obtained. The single-sided areal density of the second positive electrode sheet was 18 mg / cm². The second positive electrode sheet consisted of a third sub-positive electrode active material layer, an aluminum foil, and a fourth sub-positive electrode active material layer, stacked sequentially. The thickness of the third sub-positive electrode active material layer was 80 μm, the thickness of the aluminum foil was 13 μm, and the thickness of the fourth sub-positive electrode active material layer was 80 μm. The coating flow rate of the second positive electrode slurry was 170 g / min.

[0094] The ratio of the areal density of the first positive electrode to that of the second positive electrode is 1.15:0.9. The coating tolerance for the areal density of the first and second positive electrodes is ±1.5% during the coating process.

[0095] 3. Preparation of the electrode core

[0096] 1) Unpressed electrode core: The electrode core is assembled by stacking in a symmetrical sequence. The electrode core includes a central region, a first edge region, and a second edge region. The first edge region and the second edge region are located on both sides of the central region.

[0097] The first edge region comprises 15 sequentially stacked units, each consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet. The middle region comprises 10 sequentially stacked units, each consisting of alternating layers of a first positive electrode sheet and a negative electrode composite sheet. The second edge region comprises 15 sequentially stacked units, each consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet. The ratio of the total number of layers of the first positive electrode sheet to the total number of layers of the first and second positive electrode sheets is 1:4.

[0098] During the lamination process, the alignment accuracy between layers is strictly controlled to ensure that the alignment deviation of each positive electrode sheet and negative electrode composite sheet is ≤ ±0.3mm, thus obtaining an unpressed electrode core.

[0099] 2) Core Pressing: The unpressed cores are subjected to isostatic pressing and interfacial hot pressing treatments in sequence. Isostatic Pressing: Oil is used as the pressure transmitting medium, with a pressure of 200 MPa, a temperature of 70°C, and a holding time of 5 minutes. Interfacial Hot Pressing: The isostatically pressed cores are placed in a flatbed hot press, with a temperature of 80°C, a pressure of 30 MPa, and a holding time of 30 minutes. After pressing, a densified core is obtained.

[0100] 4. Solid-state battery fabrication

[0101] The aforementioned electrode cores were transferred to an argon-filled glove box for encapsulation, with the water content strictly controlled to be ≤0.1ppm. The bare cell components were then heat-sealed using a vacuum aluminum-plastic film to obtain a solid-state battery.

[0102] Example 2

[0103] The difference between this embodiment and Embodiment 1 is that the first edge region includes 14 sequentially stacked units, each unit consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet; the middle region includes 12 sequentially stacked units, each unit consisting of alternating layers of a first positive electrode sheet and a negative electrode composite sheet; and the second edge region includes 14 sequentially stacked units, each unit consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet. The ratio of the total number of layers of the first positive electrode sheet to the total number of layers of the first and second positive electrode sheets is 1:3.33. All other steps and conditions are the same as in Embodiment 1.

[0104] Example 3

[0105] The difference between this embodiment and Embodiment 1 is that the first edge region includes 17 sequentially stacked units, each unit consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet; the middle region includes 6 sequentially stacked units, each unit consisting of alternating layers of a first positive electrode sheet and a negative electrode composite sheet; the second edge region includes 17 sequentially stacked units, each unit consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet. The ratio of the total number of layers of the first positive electrode sheet to the total number of layers of the first and second positive electrode sheets is 1:6.67. All other steps and conditions are the same as in Embodiment 1.

[0106] Example 4

[0107] The difference between this embodiment and Embodiment 1 is that the areal density of each first positive electrode is 25 mg / cm², and the areal density of each second positive electrode is 17 mg / cm², with the ratio of the areal density of the first positive electrode to that of the second positive electrode being 1.25:0.85. The specific preparation methods for the first and second positive electrodes include the following steps:

[0108] Preparation of the first positive electrode: The positive electrode active material is... Sulfide electrolytes PVDF was dispersed in NMP at a mass ratio of 95:4:1 and stirred under vacuum for 2 hours to form a first positive electrode slurry (solid content of 52%). The first positive electrode slurry was uniformly coated on both sides of the aluminum foil for the positive electrode current collector. After drying, rolling, and die-cutting, the first positive electrode sheet was obtained. The surface density of the first positive electrode sheet was 23 mg / cm². The first positive electrode sheet consisted of a first sub-positive electrode active material layer, an aluminum foil, and a second sub-positive electrode active material layer stacked sequentially.

[0109] The thickness of the first sub-positive electrode active material layer is 108 μm, the thickness of the aluminum foil is 13 μm, and the thickness of the second sub-positive electrode active material layer is 108 μm. The coating flow rate of the first positive electrode slurry is 240 g / min.

[0110] Preparation of the second positive electrode: The positive electrode active material is... Sulfide electrolytes PVDF was dispersed in NMP at a mass ratio of 95:4:1 and stirred under vacuum for 2 hours to form a second positive electrode slurry (solid content of 52%). The second positive electrode slurry was uniformly coated on both sides of the aluminum foil used as the positive electrode current collector. After drying, rolling, and die-cutting, the second positive electrode sheet was obtained. The surface density of the second positive electrode sheet was 18 mg / cm². The second positive electrode sheet consisted of a third sub-positive electrode active material layer, an aluminum foil, and a fourth sub-positive electrode active material layer stacked sequentially.

[0111] The thickness of the third positive electrode active material layer is 75 μm, the thickness of the aluminum foil is 13 μm, and the thickness of the fourth positive electrode active material layer is 75 μm. The coating flow rate of the second positive electrode slurry is 160 g / min.

[0112] The remaining steps and conditions are the same as in Example 1.

[0113] Example 5

[0114] The difference between this embodiment and Embodiment 1 is that, as Figure 3 As shown, the electrode core includes a central region 5, a first edge region, and a second edge region. The first edge region and the second edge region are located on both sides of the central region, respectively. The first edge region includes a third sub-edge region 7, a fourth sub-edge region 8, and a fifth sub-edge region 9, and the second edge region includes a sixth sub-edge region 10, a seventh sub-edge region 11, and an eighth sub-edge region 12.

[0115] The first positive electrode has a single-sided areal density of 23 mg / cm². The second positive electrode includes a third, fourth, and fifth sub-positive electrode. The single-sided areal density of each third sub-positive electrode is 22 mg / cm², that of each fourth sub-positive electrode is 19 mg / cm², and that of each fifth sub-positive electrode is 18 mg / cm².

[0116] The preparation method of the first positive electrode is the same as that of the first positive electrode in Example 1, and the preparation method of the fifth sub-positive electrode is the same as that of the second positive electrode in Example 1. The preparation methods of the third and fourth sub-positive electrodes specifically include the following steps:

[0117] Preparation of the third positive electrode: The positive electrode active material is... Sulfide electrolytes PVDF was dispersed in NMP at a mass ratio of 95:4:1 and vacuum stirred for 2 hours to form a third positive electrode slurry (solid content of 52%). This third positive electrode slurry was uniformly coated onto both sides of the aluminum foil used as the positive electrode current collector. After drying, rolling, and die-cutting, a third sub-positive electrode sheet was obtained. The single-sided areal density of the third sub-positive electrode sheet was 22 mg / cm². The third sub-positive electrode sheet consisted of sequentially stacked layers of positive active material, aluminum foil, and another positive active material layer. The thickness of each of the two positive active material layers was 95 μm, and the thickness of the aluminum foil was 13 μm. The coating flow rate of the third positive electrode slurry was 210 g / min.

[0118] Preparation of the fourth positive electrode: The positive electrode active material is prepared... Sulfide electrolytes PVDF was dispersed in NMP at a mass ratio of 95:4:1 and vacuum stirred for 2 hours to form a fourth positive electrode slurry (solid content of 52%). This fourth positive electrode slurry was uniformly coated onto both sides of the aluminum foil used as the positive electrode current collector. After drying, rolling, and die-cutting, a fourth sub-positive electrode sheet was obtained. The single-sided areal density of the fourth sub-positive electrode sheet was 19 mg / cm². The fourth sub-positive electrode sheet consisted of sequentially stacked layers of positive electrode active material, aluminum foil, and another positive electrode active material layer. The thickness of each of the two positive electrode active material layers was 83 μm, and the thickness of the aluminum foil was 13 μm. The coating flow rate of the fourth positive electrode slurry was 181 g / min.

[0119] The third sub-edge region comprises 10 sequentially stacked units, each consisting of an alternating layer of one third-sub positive electrode sheet and one negative electrode composite sheet. The fourth sub-edge region comprises 10 sequentially stacked units, each consisting of an alternating layer of one fourth-sub positive electrode sheet and one negative electrode composite sheet. The fifth sub-edge region comprises 10 sequentially stacked units, each consisting of an alternating layer of one fifth-sub positive electrode sheet and one negative electrode composite sheet. The middle region comprises 10 sequentially stacked units, each consisting of an alternating layer of one first positive electrode sheet and one negative electrode composite sheet; the sixth sub-edge region comprises 10 sequentially stacked units, each consisting of an alternating layer of one third-sub positive electrode sheet and one negative electrode composite sheet; the seventh sub-edge region comprises 10 sequentially stacked units, each consisting of an alternating layer of one fourth-sub positive electrode sheet and one negative electrode composite sheet. The eighth sub-edge region comprises 10 stacked units stacked sequentially, each stacked unit consisting of an alternating layer of a fifth sub-positive electrode sheet and a negative electrode composite sheet. The remaining steps and conditions are the same as in Example 1.

[0120] The ratio of the total number of layers in the first positive electrode to the total number of layers in the first and second positive electrodes is 1:7.

[0121] Example 6

[0122] The difference between this embodiment and Embodiment 1 is that the first edge region includes nine sequentially stacked units, each consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet; the middle region includes eight sequentially stacked units, each consisting of alternating layers of a first positive electrode sheet and a negative electrode composite sheet; and the second edge region includes nine sequentially stacked units, each consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet. The ratio of the total number of layers of the first positive electrode sheet to the total number of layers of the first and second positive electrode sheets is 1:3.33. All other steps and conditions are the same as in Embodiment 1.

[0123] Example 7

[0124] The difference between this embodiment and Embodiment 1 is that the first edge region includes six sequentially stacked units, each consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet; the middle region includes eight sequentially stacked units, each consisting of alternating layers of a first positive electrode sheet and a negative electrode composite sheet; and the second edge region includes six sequentially stacked units, each consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet. The ratio of the total number of layers of the first positive electrode sheet to the total number of layers of the first and second positive electrode sheets is 1:2.5. All other steps and conditions are the same as in Embodiment 1.

[0125] Example 8

[0126] The difference between this embodiment and Embodiment 1 is that the first edge region includes 10 sequentially stacked units, each unit consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet; the middle region includes 20 sequentially stacked units, each unit consisting of alternating layers of a first positive electrode sheet and a negative electrode composite sheet; the second edge region includes 10 sequentially stacked units, each unit consisting of alternating layers of a second positive electrode sheet and a negative electrode composite sheet. The ratio of the total number of layers of the first positive electrode sheet to the total number of layers of the first and second positive electrode sheets is 1:2. All other steps and conditions are the same as in Embodiment 1.

[0127] Comparative Example 1:

[0128] The difference between this comparative example and Example 1 is that, during the preparation of the positive electrode, the areal density of all positive electrode sheets was 20 mg / cm². All other steps and conditions were the same as in Example 1.

[0129] Comparative Example 2:

[0130] The difference between this comparative example and Example 1 is that the electrode core includes a central region, a first edge region, and a second edge region. The first edge region and the second edge region are located on both sides of the central region, respectively. Specifically, the first edge region includes 15 sequentially stacked units, each consisting of alternating layers of a first positive electrode sheet (with a single-sided areal density of 23 mg / cm²) and a negative electrode composite sheet; the central region includes 10 sequentially stacked units, each consisting of alternating layers of a second positive electrode sheet (with a single-sided areal density of 18 mg / cm²) and a negative electrode composite sheet; the second edge region includes 15 sequentially stacked units, each consisting of alternating layers of a first positive electrode sheet and a negative electrode composite sheet. All other steps and conditions are the same as in Example 1.

[0131] The batteries in the above embodiments and comparative examples were tested as follows, and the results are shown in Table 1:

[0132] 1) Edge protrusion height of the electrode core: A Keyence LJ-X8000 laser profilometer was used, with a scanning resolution of 1μm and a scanning interval of 0.1mm. The scanning path was adjusted according to the size and edge position of the electrode core to ensure the laser line covered the entire protruding area of ​​the electrode core's edge. Using the reference plane of the electrode core edge as a reference, the height of each scanning point relative to the reference plane was calculated. The average value obtained was the edge protrusion height of the electrode core. Figure 5 The 'h' in the example. Figure 4 As shown, the height of the protrusion at the edge of the electrode core ( Figure 4 The height of the convexity (abbreviated as convexity height) decreases first and then increases as the ratio of the total number of layers of the first positive electrode to the total number of layers of the first and second positive electrodes increases.

[0133] 2) Peel strength of the electrode core: The Instron 5967 tester was used to test the peel strength in 180° peel mode. The peel rate was set to 10 mm / min. The test was conducted at a position 2 mm inward offset from the physical outer edge of the electrode core.

[0134] 3) 100-cycle capacity retention: The 100-cycle capacity retention of the battery was measured using a Neware BTS-4000 testing system. A constant current charge / discharge mode was set, with a charge / discharge rate of 0.5C. The voltage range was limited to 2.8~4.3V; charging was stopped when the battery reached 4.3V, and discharging was stopped when it reached 2.8V, completing one full charge / discharge cycle. This charge / discharge process was repeated for 100 cycles. The discharge capacity of the first week and the discharge capacity of the 100th week were recorded. 100-cycle capacity retention = (Discharge capacity of the 100th week / Discharge capacity of the first week) × 100%.

[0135] Table 1

[0136]

[0137] As can be seen from Table 1, compared with Comparative Examples 1-2, the electrode cores in Examples 1-8 have lower edge protrusion heights, and the interfaces inside the electrode cores are more tightly bonded, resulting in better cycle performance of the batteries.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrode core, characterized in that, It includes N1 stacked units stacked sequentially along the thickness direction, where N1≥2, and each stacked unit contains a positive electrode and a negative electrode stacked on top of each other; Along the thickness direction of the electrode core, the electrode core is divided into a central region and edge regions located on opposite sides of the central region; The positive electrode in the middle region is the first positive electrode, and the positive electrode in the edge region is the second positive electrode; the surface density of the first positive electrode is higher than that of the second positive electrode.

2. The electrode core according to claim 1, characterized in that, The edge region includes a first edge region and a second edge region, and the first edge region and the second edge region are symmetrically arranged with the middle region as the center of symmetry. And / or, the ratio of the areal density of the first positive electrode to the areal density of the second positive electrode is (1.05~1.25):(0.85~0.95).

3. The electrode core according to claim 1 or 2, characterized in that, The areal density of the first positive electrode is 23~25 mg / cm³. 2 ; And / or, the areal density of the second positive electrode is 17~22 mg / cm³. 2 ; And / or, the thickness of the first positive electrode is 120~300μm; And / or, the thickness of the second positive electrode is 90~225μm; And / or, the thickness of the negative electrode sheet is 20~200μm.

4. The electrode core according to any one of claims 1-3, characterized in that, The ratio of the total number of layers of the first positive electrode to the total number of layers of the first positive electrode and the second positive electrode is 1:(2.5~5).

5. The electrode core according to claim 4, characterized in that, The ratio of the total number of layers of the first positive electrode to the total number of layers of the first positive electrode and the second positive electrode is 1:(3.5~4.5).

6. The electrode core according to any one of claims 1-5, characterized in that, The edge region includes N2 sub-edge regions distributed along the thickness direction of the electrode core, where N2 ≥ 1. Along the direction from the middle region to the edge region, the single-sided surface density of the positive electrode sheet in the sub-edge regions decreases sequentially.

7. The electrode core according to any one of claims 1-6, characterized in that, The stacked unit further includes an electrolyte layer located between the positive electrode and the negative electrode; preferably, the thickness of the electrolyte layer is 10~40μm.

8. A battery, characterized in that, Includes the electrode core as described in any one of claims 1-7; preferably, the battery is a solid-state battery.

9. A battery pack, characterized in that, It includes at least two batteries as described in claim 8 that are interconnected.

10. An electrical appliance, characterized in that, It includes the battery of claim 8 or the battery pack of claim 9.

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