Lithium ion secondary battery

Abstract

The invention relates to the technical field of lithium ion batteries, and provides a lithium ion secondary battery which comprises a battery cell, and the battery cell comprises a positive plate, a diaphragm and a negative plate which are stacked; the positive plates comprise two first positive plates and a plurality of second positive plates, the first positive plates are located on the two sides of the battery cell stacking direction, the second positive plates are located between the two first positive plates, and each first positive plate comprises a first positive current collector and a first positive active layer which is arranged on the first positive current collector and faces the inner side of the battery cell; the second positive plate comprises a second positive current collector as well as a second positive active layer and a third positive active layer which are positioned on two opposite sides of the second positive current collector in the thickness direction; the first positive electrode active layer includes a positive electrode active material and first inorganic ceramic particles. The first inorganic ceramic particles are mixed in the first positive plate, so that the dynamics of the battery can be improved, the heat dissipation of the battery is facilitated, the problem of easy lithium precipitation caused by a single-sided structure of the positive electrode in the stacked lithium ion battery is effectively improved, and the safety and the service life of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and particularly relates to a lithium ion secondary battery. Background Art

[0002] Lithium ion batteries have become the main energy choice in fields such as modern electronic devices and electric vehicles due to their high energy density, long cycle life, and good environmental adaptability. However, with the continuous expansion of the application range of lithium ion batteries, the problem of lithium plating during their use has become increasingly prominent. Lithium plating refers to the phenomenon that lithium ions precipitate on the negative electrode surface to form lithium metal during the charge and discharge process of the battery. This process not only reduces the capacity and life of the battery, but may also cause safety hazards such as battery overheating and even fire.

[0003] In a stacked lithium ion battery, the top and bottom of the traditional structure are respectively a layer of single-sided positive electrode. This structural design has certain defects. First, the area of the single-sided positive electrode is relatively small, resulting in a relatively large current density during the charge and discharge process, which is likely to generate local overpotential on the positive electrode surface, thereby causing lithium ions to precipitate on the negative electrode surface. Second, due to the relatively small contact area between the edge region of the single-sided positive electrode and the negative electrode, the current distribution is uneven, making the lithium ion transmission rate in the edge region faster, further exacerbating the lithium plating phenomenon. In addition, during the charge and discharge process of the middle region of the single-sided positive electrode, due to the influence of the edge region, lithium plating also occurs. In the prior art, a ceramic layer is provided on the outer surface of the outermost single-sided positive electrode sheet of the stacked lithium battery away from the battery core. Although it can improve the stability of the positive electrode sheet to a certain extent, reduce the risk of burr short circuit, and play an insulating role, lithium plating mainly occurs on the negative electrode surface caused by lithium ion deposition. The ceramic layer is located on the outer surface of the single-sided positive electrode sheet, reducing the reaction kinetics of the lithium battery, hindering the dissipation of heat inside the battery, and causing local overheating, deteriorating the safety and service life of the battery. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above problems existing in the prior art, and provide a battery, which includes a battery core. The battery core includes two first positive electrode sheets and a plurality of second positive electrode sheets. The first positive electrode sheets are located on both sides in the stacking direction of the battery core. First inorganic ceramic particles are incorporated into the positive electrode active layer of the first positive electrode sheet, reducing the proportion of the positive electrode active material directly in contact with the electrolyte in the first positive electrode sheet, inhibiting and reducing interfacial side reactions, reducing the problem of blocked lithium intercalation paths after lithium deintercalation from the positive electrode, improving the kinetics of the battery, and facilitating heat dissipation of the battery, effectively improving the problem of easy lithium plating caused by the single-sided positive electrode structure in the stacked lithium ion battery, thereby enhancing the safety and service life of the battery.

[0005] To achieve the above purpose, the present invention provides a lithium ion secondary battery, including a battery core, and the battery core includes a positive electrode sheet, a separator, and a negative electrode sheet stacked together;

[0006] The positive electrode sheet includes two first positive electrode sheets and a plurality of second positive electrode sheets. The first positive electrode sheets are located on both sides in the stacking direction of the battery cell, and the second positive electrode sheets are located between the two first positive electrode sheets.

[0007] The first positive electrode sheet includes a first positive electrode current collector and a first positive electrode active layer provided on the side of the first positive electrode current collector facing the inside of the battery cell.

[0008] The second positive electrode sheet includes a second positive electrode current collector and a second positive electrode active layer and a third positive electrode active layer located on opposite sides in the thickness direction of the second positive electrode current collector.

[0009] The first positive electrode active layer includes a positive electrode active material and first inorganic ceramic particles.

[0010] The present invention adopts the above technical solutions and has the following beneficial effects:

[0011] (1) For the battery provided by the present invention, first inorganic ceramic particles are admixed in the positive electrode active layer of the first positive electrode sheet in the battery cell, so that the proportion of the positive electrode active material directly contacting the electrolyte in the first positive electrode sheet is reduced, the interfacial side reactions are inhibited and reduced, the problem that the lithium intercalation path is blocked after the positive electrode is de-lithiated is reduced, the kinetics of the battery is improved, and it is beneficial to the heat dissipation of the battery. The problem of easy lithium deposition caused by the single-sided structure of the positive electrode in the stacked lithium-ion battery is effectively improved, and thus the cycle performance, safety and service life of the battery are improved.

[0012] (2) For the battery provided by the present invention, the first inorganic ceramic particles are distributed on the surface of the positive electrode active material to form a "protective film", which can inhibit the occurrence of interfacial side reactions, and the cross-linked network formed with the positive electrode active material can further accelerate the lithium ion transmission rate, thereby further improving the cycle performance and rate performance of the battery.

[0013] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In this article, unless otherwise specified, the data ranges include endpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Shown is a schematic structural diagram of a stacked battery cell in an embodiment of the present invention.

[0015] Figure 2 Shown is a schematic diagram of the surface structure of the negative electrode active layer in an embodiment of the present invention.

[0016] Reference numerals: 1 - first positive electrode sheet; 2 - negative electrode sheet; 3 - second positive electrode sheet; 4 - positive electrode current collector; 5 - first positive electrode active layer; 6 - negative electrode current collector; 7 - negative electrode active layer; 8 - separator; 9 - second positive electrode active layer; 10 - third positive electrode active layer; 11 - tab; 12 - first recessed groove; 13 - second recessed groove. Detailed embodiments

[0017] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0018] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention pertains.

[0019] In the present invention, the terms "battery", "lithium battery", "lithium ion battery", and "lithium ion secondary battery" all have the same meaning, and generally include an electrode assembly (such as a positive electrode sheet, a negative electrode sheet, and a separator), a container (housing) for accommodating the electrode assembly, and an electrolyte.

[0020] In the present invention, the term "Dv50" refers to the particle size corresponding to when the cumulative volume particle size distribution percentage of a sample (in the present invention, it refers to the first inorganic ceramic particles or the second inorganic ceramic particles) reaches 50%. The Dv50 of the first inorganic ceramic particles or the second inorganic ceramic particles can be measured by a laser particle size analyzer.

[0021] In the present invention, the term "Dv99" refers to the particle size corresponding to when the cumulative volume particle size distribution percentage of a sample (in the present invention, it refers to the first inorganic ceramic particles or the second inorganic ceramic particles) reaches 99%. The Dv99 of the first inorganic ceramic particles or the second inorganic ceramic particles can be measured by a laser particle size analyzer.

[0022] The present invention provides a battery, including an electric core, and the electric core includes a positive electrode sheet, a separator, and a negative electrode sheet stacked together;

[0023] The positive electrode sheet includes two first positive electrode sheets and a plurality of second positive electrode sheets. The first positive electrode sheets are located on both sides in the stacking direction of the electric core, and the second positive electrode sheets are located between the two first positive electrode sheets.

[0024] The first positive electrode sheet includes a first positive electrode current collector and a first positive electrode active layer provided on the inner side of the first positive electrode current collector facing the electric core;

[0025] The second positive electrode sheet includes a second positive electrode current collector and a second positive electrode active layer and a third positive electrode active layer located on opposite sides in the thickness direction of the second positive electrode current collector;

[0026] The first positive electrode active layer includes a positive electrode active material and first inorganic ceramic particles.

[0027] In the battery provided by the present invention, first inorganic ceramic particles are admixed in the first positive electrode active layer of the first positive electrode sheets located on the outermost sides in the stacking direction of the battery core. On the one hand, the proportion of the active material directly contacting the electrolyte on the surface of the first positive electrode active layer is reduced, inhibiting and reducing interfacial side reactions, reducing the problem of blocked lithium intercalation paths after lithium deintercalation from the positive electrode, improving the kinetics of the battery, and being beneficial to battery heat dissipation, effectively improving the problem of easy lithium deposition caused by the single-sided structure of the positive electrode in the stacked lithium-ion battery, thereby enhancing the safety and service life of the battery; on the other hand, the first inorganic ceramic particles are distributed on the surface of the positive electrode active material to form a "protective film" (or protective layer), which can inhibit interfacial side reactions. The first inorganic ceramic particles can form a cross-linked network and can further accelerate the lithium ion transmission rate, reducing the resistance of the lithium intercalation path after lithium deintercalation from the first positive electrode sheet, thereby improving the cycle performance and rate performance of the battery.

[0028] In the present invention, the positive electrode sheet includes two first positive electrode sheets and multiple second positive electrode sheets. The first positive electrode sheets are located on the outermost two sides in the stacking direction of the battery core, and the second positive electrode sheets are located between the two first positive electrode sheets. Among them, "multiple second positive electrode sheets" can be understood as at least one, preferably two or more, and the number of second positive electrode sheets can be adjusted according to the specification requirements of the battery. In addition, the first positive electrode sheet is provided with a positive electrode active layer only on the surface of the positive electrode current collector facing the inside of the battery core (only one-sided positive electrode active layer); the second positive electrode sheet is provided with positive electrode active layers on both opposite sides in the thickness direction of the positive electrode current collector (with two-sided positive electrode active layers). That is, it can be understood that the first positive electrode sheet is a single-sided positive electrode sheet and the second positive electrode sheet is a double-sided positive electrode sheet.

[0029] Specifically, in some embodiments, as Figure 1 shown is a schematic diagram of the battery core structure in an embodiment. Along the stacking direction of the battery core (as shown by the arrow in the figure), the outermost layers on both sides of the battery core include first positive electrode sheets 1, and the intermediate layer includes multiple negative electrode sheets 2 and multiple second positive electrode sheets 3; the first positive electrode sheet 1 includes a positive electrode current collector 4 and a first positive electrode active layer 5 provided on one surface of the positive electrode current collector 4. The first positive electrode active layer 5 is located inside the battery core and is close to the negative electrode sheet 2; the negative electrode sheet 2 includes a negative electrode current collector 6 and negative electrode active layers 7 located on both surfaces of the negative electrode current collector 6; the second positive electrode sheet 3 includes second positive electrode active layers 9 and third positive electrode active layers 10 located on both surfaces of the positive electrode current collector 4; the first inorganic ceramic particles are admixed in the first positive electrode active layer 5, which can alleviate the problem of lithium deposition on the surface of the negative electrode sheet 2 opposite to the first positive electrode sheet 1, and can improve the lithium ion deintercalation and intercalation performance of the first positive electrode sheet 1, and improve the cycle performance and rate performance of the battery.

[0030] In some embodiments, the first inorganic ceramic particles include an inorganic particle matrix and an organics coating on the surface, and the organics includes at least one group selected from amino group, vinyl group, propenyl group, epoxy group, methyl group, ethyl group, propyl group, acryloyloxy group, 1,3-butadienyl group, alkoxy group, acyloxy group, and ester group.

[0031] In the battery provided by the present invention, the first inorganic ceramic particles are admixed in the first positive electrode active layer of the first positive electrode sheet. The surface of the first inorganic ceramic particles is coated with the organics containing the above groups, which can make the first inorganic ceramic particles better distributed on the surface of the positive electrode active material to form a protective layer. On the one hand, it can reduce the proportion of the active material directly contacting the electrolyte on the surface of the first positive electrode active layer, inhibit and reduce interfacial side reactions, reduce the problem of the lithium intercalation path being blocked after the positive electrode is de-lithiated, effectively improve the problem of easy lithium precipitation caused by the single-sided structure of the positive electrode, improve the kinetics of the battery, and is conducive to the heat dissipation of the battery, thereby enhancing the safety and service life of the battery; on the other hand, the cross-linked network formed by the first inorganic ceramic particles more easily can further accelerate the lithium ion transport rate, thereby improving the cycle performance and rate performance of the battery.

[0032] In some embodiments, based on the total mass of the first positive electrode active layer, the mass ratio of the first inorganic ceramic particles is denoted as a, and a satisfies: 0.05% ≤ a ≤ 2%. For example, the mass ratio of the first inorganic ceramic particles can be 0.05%, 0.08%, 0.1%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0% or any value within the range composed of any two of the above values. By controlling the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer to satisfy the above range in the present invention, when a < 0.05%, the cross-linked network formed by the first inorganic ceramic particles in the first positive electrode active layer is too sparse, and it is easy to cause the collapse of the cross-linked network structure during the lithiation / delithiation process of the first positive electrode sheet, resulting in the first inorganic ceramic particles being difficult to play their original cross-linked network role and being unfavorable for the improvement of lithium precipitation at the negative electrode interface; when a > 2.0%, the cross-linked network formed by the first inorganic ceramic particles in the first positive electrode active layer is too dense, which hinders the delithiation process of the first positive electrode sheet, making the specific capacity of the first positive electrode sheet unable to be fully exerted, resulting in a decrease in the battery capacity.

[0033] Exemplarily, when the first inorganic ceramic particles contain silicon elements, the mass ratio (a) of the first inorganic ceramic particles in the first positive electrode active layer can be tested by an energy dispersive X-ray spectroscopy (EDS) method or an inductively coupled plasma (ICP) test method. Among them, the specific steps for testing by EDS include: scanning the sample in multiple regions (at least 5 random regions) to obtain the average mass percentage content of silicon (Si) elements in the positive electrode active layer, denoted as C Si, due to the Si element in the positive electrode sheet being the first inorganic ceramic particles and the occupancy ratio of silicon atoms in the first inorganic ceramic particles remaining unchanged, the mass ratio (a) of the first inorganic ceramic particles in the first positive electrode active layer can be approximately obtained using the average mass percentage content of silicon (Si) element. For example, if the first inorganic ceramic particles include SiO2 coated with functional silane on the surface, the mass ratio (a) of the first inorganic ceramic particles in the first positive electrode active layer can be approximately calculated by the following formula: a = C Si / W Si , where W Si is the theoretical mass percentage of silicon element in pure SiO2.

[0034] In some embodiments, the second positive electrode active layer and / or the third positive electrode active layer include second inorganic ceramic particles; the second inorganic ceramic particles include an inorganic particle matrix and an organic substance coated on the surface, and the organic substance includes at least one group among amino group, vinyl group, propenyl group, epoxy group, methyl group, ethyl group, propyl group, acryloyloxy group, 1,3-butadienyl group, alkoxy group, acyloxy group, and ester group.

[0035] In some embodiments, the first inorganic ceramic particles and the second inorganic ceramic particles are the same or different, preferably the same.

[0036] In a battery design pursuing high energy density, in order to meet specific energy density and areal density requirements, it is often necessary to highly compact the positive and negative electrode materials. Although this method can effectively control the thickness of the battery cell, the highly compacted electrode sheet makes the molecular packing extremely dense, and it may be difficult for lithium ions to embed or escape in the tight molecular structure. The resistance increases when lithium ions embed into the negative electrode sheet, which may further lead to an increased risk of overall lithium deposition at the negative electrode interface of the battery. Referring to Figure 1 the structure of the stacked battery cell shown, the present invention can further incorporate second inorganic ceramic particles into the second positive electrode sheet 3 located inside the stacked battery cell. The second inorganic ceramic particles can form a cross-linked network in the second positive electrode active layer 9 and / or the third positive electrode active layer 10 in the second positive electrode sheet 3, and play the role of an "interface bridge" during the process of lithium salt deintercalation from the second positive electrode sheet 3 to exchanging lithium ions with the electrolyte, accelerating the transmission of lithium ions, and to a certain extent, alleviating the problem of lithium deposition at the negative electrode interface caused by excessive compaction of the electrode sheet.

[0037] Furthermore, the present invention continuously adjusts the mass ratio a of the first inorganic ceramic particles in the first positive electrode active layer, and the mass ratio f of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer to satisfy a specific value range according to the areal density and compaction density of the second positive electrode sheet, and the areal density and compaction density of the negative electrode sheet. The specific adjustment is as follows:

[0038] In some embodiments, the areal density b of the second positive electrode sheet satisfies 0.15 mg / cm 2 ≤b≤40 mg / cm 2 , the areal density c of the negative electrode sheet satisfies 0.1 mg / cm 2 ≤c≤16 mg / cm 2 , the tap density d of the second positive electrode sheet satisfies 3.8 g / cm 3 ≤d≤4.5 g / cm 3 , the tap density e of the negative electrode sheet satisfies 1.3 g / cm 3 ≤e≤1.90 g / cm 3 ; the mass ratio a of the first inorganic ceramic particles in the first positive electrode active layer satisfies 0.2% ≤ a ≤ 2%, and the mass ratio f of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer satisfies 0.1%a ≤ f ≤ 95%a. Further, the lithium ion insertion / extraction capabilities of the first positive electrode sheet and the second positive electrode sheet are different. Since there is only a single layer of positive electrode active layer in the first positive electrode sheet, the lithium ion insertion / extraction ability is relatively poor. To make the lithium ion insertion / extraction rates of the first positive electrode sheet and the second positive electrode sheet at a similar level and avoid the problem of lithium metal deposition at the negative electrode interface caused by uneven lithium ion insertion / extraction rates, when the areal densities and tap densities of the positive and negative electrode sheets are adjusted within the above ranges in the present invention, the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer in the first positive electrode sheet is higher than the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer in the second positive electrode sheet, which can make the lithium ions have similar insertion / extraction rates in the first positive electrode sheet and the second positive electrode sheet, thereby reducing the problem of lithium metal deposition at the negative electrode interface.

[0039] Further, in order to more specifically define the relationship between the areal density and tap density of the second positive electrode sheet, the areal density and tap density of the negative electrode sheet, and the contents of the mass ratio a of the first inorganic ceramic particles and the mass ratio f of the second inorganic ceramic particles, the present invention also proposes the following solution:

[0040] In some embodiments, the areal density b of the second positive electrode sheet satisfies 0.15 mg / cm 2 ≤b≤18 mg / cm 2 , the areal density c of the negative electrode sheet satisfies 0.1 mg / cm 2 ≤c≤7.5 mg / cm 2 , the tap density d of the second positive electrode sheet satisfies 4.0 g / cm 3 ≤d≤4.13 g / cm 3 , the tap density e of the negative electrode sheet satisfies 1.5 g / cm 3 ≤e≤1.70 g / cm 3; The mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a1. When 0.2% ≤ a1 ≤ 0.5%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f1, and f1 satisfies 0.1%a1 ≤ f1 ≤ 50%a1. Among them, the mass ratio a1 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.2%, 0.3%, 0.4%, 0.5% or any value in the range composed of the above two values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 0.1%a1, 10%a1, 20%a1, 30%a1, 40%a1, 50%a1 or any value in the range composed of the above two values.

[0041] In some embodiments, the areal density b of the second positive electrode sheet satisfies 18 mg / cm 2 <b ≤ 24 mg / cm 2 , the areal density c of the negative electrode sheet satisfies 7.5 mg / cm 2 <c ≤ 10 mg / cm 2 , the tap density d of the second positive electrode sheet satisfies 4.11 g / cm 3 ≤ d ≤ 4.16 g / cm 3 , the tap density e of the negative electrode sheet satisfies 1.71 g / cm 3 ≤ e ≤ 1.74 g / cm 3 ; The mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a2. When 0.4% ≤ a2 ≤ 0.9%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f2, and f2 satisfies 15%a2 ≤ f2 ≤ 65%a2. Among them, the mass ratio a2 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or any value in the range composed of the above two values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 15%a2, 20%a2, 30%a2, 40%a2, 50%a2, 60%a2, 65%a2 or any value in the range composed of the above two values.

[0042] In some embodiments, the areal density b of the second positive electrode sheet satisfies 24 mg / cm 2 <b ≤ 30 mg / cm 2 , the areal density c of the negative electrode sheet satisfies 9.5 mg / cm 2 <c ≤ 13 mg / cm 2 , the tap density d of the second positive electrode sheet satisfies 4.13 g / cm 3 ≤ d ≤ 4.20 g / cm 3, the compaction density e of the negative electrode sheet satisfies 1.65 g / cm 3 ≤e≤1.76 g / cm 3 , the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a3. When 0.6% ≤ a3 ≤ 1.5%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f3, and f3 satisfies 25%a3 ≤ f3 ≤ 85%a3. Among them, the mass ratio a3 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or any value in the range composed of any two of the above values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 25%a3, 30%a3, 40%a3, 50%a3, 60%a3, 70%a3, 80%a3, 85%a3 or any value in the range composed of any two of the above values.

[0043] In some embodiments, the areal density b of the second positive electrode sheet satisfies 30 mg / cm 2 <b≤40 mg / cm 2 , the areal density c of the negative electrode sheet satisfies 11.5 mg / cm 2 <c≤16.0 mg / cm 2 , the compaction density d of the second positive electrode sheet satisfies 4.10 g / cm 3 ≤d≤4.23 g / cm 3 , the compaction density e of the negative electrode sheet satisfies 1.60 g / cm 3 ≤e≤1.78 g / cm 3 , the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a4. When 0.8% ≤ a4 ≤ 1.8%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f4, and f4 satisfies 30%a4 ≤ f4 ≤ 95%a4. Among them, the mass ratio a4 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or any value in the range composed of any two of the above values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 30%a4, 40%a4, 50%a4, 60%a4, 70%a4, 80%a4, 90%a4, 95%a4 or any value in the range composed of any two of the above values.

[0044] In the manufacturing of battery cells, the areal density directly affects the lithium plating window of the electrode sheet and the stacking layers of the electrode sheets inside the battery cell. The smaller the areal density, the better the electrode kinetics and the less likely to plate lithium. However, the stacking layers of the electrode sheets will be more, resulting in more stacking layers of the current collector and the separator, increasing the thickness of the battery cell and reducing the energy density of the battery cell. When improving the lithium plating window of the battery by reducing the areal density without affecting the energy density of the battery cell, the general direction is to appropriately increase the compaction density while reducing the areal density. The present invention further adjusts the blending amount of the first inorganic ceramic particles and the second inorganic ceramic particles according to the differences in the areal density and compaction degree of the second positive electrode sheet and the negative electrode sheet. The higher the areal density of the second positive electrode sheet, the higher the blending amount of the first inorganic ceramic particles and the second inorganic ceramic particles, which is more conducive to accelerating the transmission of lithium ions and alleviating the problems of lithium plating at the negative electrode interface and poor kinetic performance caused by too high areal density of the positive electrode sheet.

[0045] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active layer provided on at least one side of the negative current collector; the negative active layer includes a negative active material, and the negative active material includes a silicon-based material and a carbon-based material; based on the total mass of the negative active material, the content of silicon element is 3%-80%, for example, it can be 3%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or any point value within the range composed of the above two point values, preferably 3%-35%. The theoretical specific capacity of silicon (4200 mAh / g) is much higher than that of traditional graphite negative electrode materials. Adding silicon to the negative electrode sheet can significantly improve the energy density of the battery.

[0046] Exemplarily, the content of silicon element in the negative active material can be tested by an energy dispersive X-ray spectrometer (EDS) or an inductively coupled plasma (ICP) test method.

[0047] In some embodiments, the silicon-based material includes at least one of silicon-carbon material, silicon-oxygen material, elemental silicon-based material, and silicon alloy material.

[0048] In some embodiments, the carbon-based material includes at least one of artificial graphite, natural graphite, hard carbon, soft carbon, and mesophase carbon microspheres.

[0049] In some embodiments, the silicon-based material is preferably a silicon-carbon material, and the silicon-carbon material includes a porous carbon matrix and silicon material located within the porous carbon matrix. The silicon-carbon material has a fast lithium ion insertion / extraction rate, which can effectively improve the fast charging performance of the battery; the expansion rate of the silicon-carbon material is relatively low. The silicon-carbon material can limit the volume change of silicon within the porous carbon matrix during charge and discharge, avoiding pulverization caused by uneven stress due to volume expansion of silicon, having good structural stability, and not easily occurring safety problems such as short circuit or combustion, which is beneficial to improving the safety performance of the battery.

[0050] In some embodiments, the Dv50 of the silicon-carbon material is 1 μm - 15 μm, and can be, for example, 1 μm, 2 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any value within the range formed by any two of the above values. When the Dv50 of the silicon-carbon material is within the above range, the volume change of the silicon-carbon material during charge and discharge can be reduced, lithium deposition on the negative electrode can be reduced, and the safety of the battery can be improved.

[0051] In some embodiments, in the silicon-carbon material, the mass content of silicon element is 20% - 80%, and can be, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or any value within the range formed by any two of the above values.

[0052] In some embodiments, the mass ratio a of the first inorganic ceramic particles in the first positive electrode active layer satisfies 0.4% ≤ a ≤ 2%, and the mass ratio f of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer satisfies f ≤ a.

[0053] By adding a silicon-based material to the negative electrode active material in the negative electrode active layer, the ability of the negative electrode sheet to insert and extract lithium ions is also improved. To ensure that the rate of inserting and extracting lithium ions in the first positive electrode sheet and the second positive electrode sheet matches the rate of inserting and extracting lithium ions in the negative electrode sheet, and to avoid the problem of lithium deposition on the negative electrode interface caused by uneven lithium ion insertion and extraction rate, the present invention further adjusts the content range of the first inorganic ceramic particles blended in the first positive electrode sheet to increase, and the content of the second inorganic ceramic particles blended in the second positive electrode sheet is not higher than the content of the first inorganic ceramic particles, so that the lithium ion insertion and extraction rates of the first positive electrode sheet, the second positive electrode sheet, and the negative electrode sheet are at a similar level, thereby reducing the problem of lithium deposition on the negative electrode interface.

[0054] In some embodiments, the present invention further adjusts the silicon element content in the negative electrode active material, the blending amounts of the first inorganic ceramic particles and the second inorganic ceramic particles according to the surface densities of the second positive electrode sheet and the negative electrode sheet. The higher the surface densities of the second positive electrode sheet and the negative electrode sheet, the higher the silicon element content in the negative electrode active material, and the higher the blending amounts of the first inorganic ceramic particles and the second inorganic ceramic particles, which is more beneficial to accelerating the transmission of lithium ions and alleviating the problems of lithium deposition on the negative electrode interface and poor kinetic performance caused by too high surface densities of the positive electrode sheet and the negative electrode sheet. Specific embodiments are as follows:

[0055] In some embodiments, the surface density b of the second positive electrode sheet satisfies 0.15 mg / cm 2 ≤ b ≤ 18 mg / cm 2 and the surface density c of the negative electrode sheet satisfies 0.1 mg / cm 2 ≤ c ≤ 7.5 mg / cm2 ; When the silicon element content g in the negative electrode active material satisfies 3% ≤ g ≤ 7%, the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a5, and when 0.4% ≤ a5 ≤ 0.8%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f5, and f5 satisfies 0.1%a5 ≤ f5 ≤ 60%a5. Among them, the silicon element content g in the negative electrode active material can be, for example, 3%, 4%, 5%, 6%, 7% or any point value in the range composed of two-point values; the mass ratio a5 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or any point value in the range composed of two-point values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 0.1%a5, 10%a5, 20%a5, 30%a5, 40%a5, 50%a5, 60%a5 or any point value in the range composed of two-point values.

[0056] In some embodiments, the second positive electrode surface density b satisfies 18mg / cm 2 <b ≤ 24mg / cm 2 , the negative electrode surface density c satisfies 3mg / cm 2 ≤ c ≤ 8.5mg / cm 2 ; When the silicon element content g in the negative electrode active material satisfies 7% < g ≤ 12.5%, the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a6, and when 0.5% ≤ a6 ≤ 1.1%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f6, and f6 satisfies 10%a6 ≤ f6 ≤ 80%a6. Among them, the silicon element content g in the negative electrode active material can be, for example, 7.5%, 8%, 9%, 10%, 11%, 12%, 12.5% or any point value in the range composed of two-point values, and the mass ratio a6 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1% or any point value in the range composed of two-point values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 10%a6, 20%a6, 30%a6, 40%a6, 50%a6, 60%a6, 70%a6, 80%a6 or any point value in the range composed of two-point values.

[0057] In some embodiments, the second positive electrode surface density b satisfies 24mg / cm 2 <b ≤ 30mg / cm 2 , the negative electrode surface density c satisfies 4mg / cm 2 ≤ c ≤ 11mg / cm 2, the content of silicon element g in the negative electrode active material satisfies 12.5% < g ≤ 17.5%; when the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a7 and a7 satisfies 0.6% ≤ a7 ≤ 1.4%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f7, and f7 satisfies 20%a7 ≤ f7 ≤ 90%a7. Among them, the content of silicon element g in the negative electrode active material can be, for example, 13%, 14%, 14.5%, 15%, 15.5%, 16%, 17.5% or any point value within the range composed of two-point values; the mass ratio a7 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4% or any point value within the range composed of two-point values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 20%a7, 30%a7, 40%a7, 50%a7, 60%a7, 70%a7, 80%a7, 90%a7 or any point value within the range composed of two-point values.

[0058] In some embodiments, the areal density b of the second positive electrode satisfies 30 mg / cm 2 <b ≤ 40 mg / cm 2 , the areal density c of the negative electrode satisfies 4 mg / cm 2 ≤ c ≤ 15 mg / cm 2 , the content of silicon element g in the negative electrode active material satisfies 17.5% < g ≤ 40%; when the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer is denoted as a8 and a8 satisfies 0.7% ≤ a8 ≤ 1.8%, the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer is denoted as f8, and f8 satisfies 20%a8 ≤ f8 ≤ 100%a8. Among them, the content of silicon element g in the negative electrode active material can be, for example, 18%, 20%, 25%, 30%, 35%, 40% or any point value within the range composed of two-point values; the mass ratio a8 of the first inorganic ceramic particles in the first positive electrode active layer can be, for example, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or any point value within the range composed of two-point values; the mass ratio of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer can be, for example, 20%a8, 30%a8, 40%a8, 50%a8, 60%a8, 70%a8, 80%a8, 90%a8, 100%a8 or any point value within the range composed of two-point values.

[0059] In some embodiments, the first inorganic ceramic particle matrix and / or the second inorganic ceramic particle matrix includes one or more of silica, alumina, boehmite, magnesia, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, and calcium carbonate. The first inorganic ceramic particle matrix and the second inorganic ceramic particle matrix are not limited thereto, and inorganic ceramic particles coated with an organic substance can all be applied to the battery of the present invention.

[0060] In some embodiments, the first inorganic ceramic particle and / or the second inorganic ceramic particle matrix includes silica; the silicon element content in the first inorganic ceramic particle and / or the second inorganic ceramic particle is 20%-30%, for example, it can be 20%, 21%, 21.47%, 22%, 22.57%, 23%, 25%, 26%, 28%, 30%, or any point value within the range composed of any two of the above values.

[0061] In some embodiments, the first inorganic ceramic particle and / or the second inorganic ceramic particle includes SiO2 coated with a functional silane on the surface.

[0062] In some embodiments, the chemical formula of the first inorganic ceramic particle and / or the second inorganic ceramic particle is R-Si-X; R includes at least one of amino, vinyl, propenyl, epoxy, methyl, ethyl, propyl, acryloyloxypropyl, 1,3-butadienyl; X includes at least one of halogen, alkoxy, acyloxy, ester group. Among them, the R group can react with the functional group in the electrolyte organic matter, and the X group is a group capable of hydrolysis, which can improve the adhesion strength between the organic matter and the inorganic matter. The presence of the R group and the X group can make the first inorganic ceramic particle and / or the second inorganic ceramic particle distribute on the surface of the positive electrode active material to form a protective layer. In addition, the first inorganic ceramic particle and / or the second inorganic ceramic particle is mainly composed of Si in the structure, and can form a cross-linked network with the positive electrode active material during the charge and discharge process of the battery, so that the first inorganic ceramic particle and / or the second inorganic ceramic particle play the role of an "interface bridge" in the process of exchanging lithium ions with the electrolyte after the inorganic lithium salt in the positive electrode sheet is de-lithiated, and fully participate in the lithiation / delithiation reaction of the positive electrode sheet, thereby reducing the lithium concentration level on the surface of the negative electrode, reducing the range of the locally supersaturated lithium concentration region of the SEI solid-liquid interface of the negative electrode sheet, effectively improving the lithium deposition problem of the negative electrode sheet, and enhancing the cycle performance of the battery.

[0063] In some embodiments, the first inorganic ceramic particles include Si element. Based on the total mass of the first positive electrode active layer, the content G of Si element is 100 ppm - 3000 ppm. For example, it can be 100 ppm, 200 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2500 ppm, 2800 ppm, 3000 ppm or any value within the range composed of any two of the above values. In the first positive electrode active layer, when the Si element content G satisfies the above range, it has the following effects: First, the Si element can promote the diffusion of lithium ions. The introduction of the Si element significantly improves the chemical coordination environment between the transition metal element and O in the positive electrode active material, which is beneficial to promoting the diffusion of lithium ions, can effectively improve the charge-discharge efficiency of the battery, and enhance the cycle performance of the battery; Second, the Si element can stabilize the lattice structure. In the highly delithiated state, the positive electrode active material containing silicon element has a more stable lattice oxygen framework structure, which helps to inhibit the degradation of the lattice structure, thereby enhancing the structural stability of the battery, improving the cycle performance of the battery, and reducing lithium plating.

[0064] Furthermore, when the Si element content G satisfies the above range, it can also reduce the oxygen loss of the positive electrode active material. The positive electrode active material containing silicon element has a lower oxygen release amount in the delithiated state, which helps to reduce the accumulation of electrolyte decomposition products, thereby reducing the oxygen vacancy concentration on the electrode surface and improving the cycle stability of the battery.

[0065] The present invention further controls the mass ratio of the Si element in the positive electrode active layer to satisfy the above range, which can improve the cycle stability of the battery, and enhance the cycle performance and rate performance of the battery.

[0066] In some embodiments, the first inorganic ceramic particles and / or the second inorganic ceramic particles include halogen; preferably, the halogen includes at least one of F, Cl, Br, and I.

[0067] Preferably, in the first inorganic ceramic particles and / or the second inorganic ceramic particles, the content of F element is 2%-3% (for example, it can be 2%, 2.07%, 2.53%, 3% or any value within the range composed of the above two values), and / or the content of Cl element is 3%-5% (for example, it can be 3%, 3.23%, 4.37%, 5% or any value within the range composed of the above two values), and / or the content of Br element is 2%-4% (for example, it can be 2%, 2.95%, 3%, 3.26%, 4% or any value within the range composed of the above two values), and / or the content of I element is 1%-2% (for example, it can be 1%, 1.06%, 1.34%, 1.5%, 1.8%, 2% or any value within the range composed of the above two values). When the first inorganic ceramic particles and the second inorganic ceramic particles contain halogens and the content of halogen elements is adjusted within the above range, the distribution of the first inorganic ceramic particles on the surface of the positive electrode active material is more uniform, effectively reducing the direct contact area between the positive electrode active material and the electrolyte, and inhibiting lithium deposition and side reactions.

[0068] In some embodiments, the first inorganic ceramic particles include at least one of Si element, C element, O element, H element, and N element.

[0069] In some embodiments, based on the total mass of the first inorganic ceramic particles, the mass proportion of N element is 13%-15%, for example, it can be 13%, 13.94%, 14%, 14.66%, 15% or any value within the range composed of the above two values; and / or, the mass proportion of O element is 23%-26%, for example, it can be 23%, 23.81%, 24%, 25.03%, 26% or any value within the range composed of the above two values; and / or, the mass proportion of C element is 22%-24%, for example, it can be 22%, 22.73%, 23%, 23.89%, 24% or any value within the range composed of the above two values. And / or, the mass proportion of H element is 5%-6%, for example, it can be 5%, 5.41%, 5.5%, 5.69%, 6% or any value within the range composed of the above two values. The present invention defines that the proportions of C element, O element, H element, and N element in the first inorganic ceramic particles satisfy the above range, which can ensure the stable distribution of the first inorganic ceramic particles on the surface of the positive electrode active material, form a cross-linked network with the positive electrode active material, play the role of an "interface bridge", and further improve lithium deposition at the negative electrode interface and increase the lithium ion transmission rate.

[0070] Exemplarily, the mass proportion of each element in the first inorganic ceramic particles can be tested by an energy dispersive X-ray spectrometer (EDS) or ICP.

[0071] In some embodiments, the first inorganic ceramic particles include N element, and / or F element, and / or Cl element; based on the total mass of the first positive electrode active layer, the content of N element is 60 ppm - 2000 ppm (for example, it can be 60 ppm, 100 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm or any value within the range composed of any two of the above values); and / or, the content of F element is 10 ppm - 300 ppm (10 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm or any value within the range composed of any two of the above values); and / or, the content of Cl element is 15 ppm - 1000 ppm (15 ppm, 100 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm or any value within the range composed of any two of the above values). The present invention defines that the proportions of N element, F element, and Cl element in the first modified ceramic satisfy the above ranges, which can avoid the situation that the proportions of N element, F element, and Cl element as substituents are too small, resulting in a weakened cross-linking effect of the first modified ceramic on the positive electrode active material, an inability to effectively reduce the direct contact area between the positive electrode active material and the electrolyte, and a poor effect of suppressing lithium deposition and side reactions.

[0072] Exemplarily, the mass proportion of each element in the positive electrode active layer of the present invention can be obtained by multiplying the mass proportion of the first inorganic ceramic particles in the first positive electrode active layer by the proportion of each element in the first inorganic ceramic particles.

[0073] In some embodiments, the particle sizes of the first inorganic ceramic particles and / or the second inorganic ceramic particles independently satisfy: 50 nm ≤ Dv50 ≤ 500 nm, 300 nm ≤ Dv99 ≤ 1000 nm. The Dv50 of the first inorganic ceramic particles and the second inorganic ceramic particles can be, for example, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 500 nm or any value within the range composed of any two of the above values; the Dv99 of the first inorganic ceramic particles and the second inorganic ceramic particles can be, for example, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or any value within the range composed of any two of the above values. When the particle sizes of the first inorganic ceramic particles and the second inorganic ceramic particles are within the above ranges, it can avoid the situation that the particle sizes of the first inorganic ceramic particles and / or the second inorganic ceramic particles are too small, making it difficult for lithium ions to be inserted and extracted; and it can avoid the situation that the particle sizes of the first inorganic ceramic particles and / or the second inorganic ceramic particles are too large, resulting in a weakened effect of the first inorganic ceramic particles and / or the second inorganic ceramic particles in forming a protective layer on the positive electrode active material.

[0074] Exemplarily, the particle sizes Dv50 and Dv99 of the first inorganic ceramic particles and the second inorganic ceramic particles can both be tested using a laser particle size analyzer.

[0075] In some embodiments, the positive electrode active material includes at least one of lithium cobaltate, ternary nickel cobalt manganese lithium oxide, ternary nickel cobalt aluminum lithium oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium vanadate, lithium manganate, and lithium nickelate.

[0076] In some preferred embodiments, the particle sizes of the first inorganic ceramic particles and the second inorganic ceramic particles independently satisfy: 220 nm ≤ Dv50 ≤ 320 nm, 340 nm ≤ Dv99 ≤ 440 nm. Among them, the Dv50 of the first inorganic ceramic particles and the second inorganic ceramic particles can be, for example, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, or any value within the range formed by any two of the above values; the Dv99 of the first inorganic ceramic particles and the second inorganic ceramic particles can be, for example, 340 nm, 360 nm, 380 nm, 400 nm, 420 nm, 440 nm, or any value within the range formed by any two of the above values. The larger the particle size of the ceramic particles, the more space they occupy in the positive electrode active layer, and the greater the resistance to the insertion and extraction paths of lithium ions in the positive electrode sheet. Conversely, the smaller the particle size of the ceramic particles, the larger the specific surface area, which is more conducive to the insertion and extraction of lithium ions. Further optimizing the particle size range of the first inorganic ceramic particles and the second inorganic ceramic particles is beneficial for the stable distribution of the first inorganic ceramic particles and the second inorganic ceramic particles on the surface of the positive electrode active material to form a protective layer, as well as improving the lithium ion transport in the positive electrode sheet and enhancing the cycle performance of the battery.

[0077] In some embodiments, in the thickness direction of the negative electrode sheet, a recess is provided on the negative electrode active layer in the negative electrode sheet; the depth of the recess is j μm; the relationship between the depth j of the recess and the content G of Si element in the first positive electrode active layer satisfies: 0.0043 ≤ j / G ≤ 1. The ratio of j / G can be, for example, 0.0043, 0.005, 0.008, 0.01, 0.05, 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, 0.9, 1, or any value within the range formed by any two of the above values, and preferably 0.05 ≤ j / G ≤ 1.

[0078] In some embodiments, the recess can be at least one of a circular hole, a regular polygon hole, an irregular polygon hole, a linear groove, and a strip groove.

[0079] Doping the first positive electrode sheet with the first inorganic ceramic particles can accelerate the rate of lithium ion extraction from the first positive electrode sheet during charging. The corresponding negative electrode sheet should have the ability to receive lithium ions that matches the lithium deintercalation ability of the first positive electrode sheet, so as to improve the fast charging performance of the battery and avoid the problem of lithium deposition on the negative electrode interface caused by uneven lithium ion deintercalation rate. In the present invention, by further providing recesses on the negative electrode active layer of the negative electrode sheet and adjusting the depth j of the recesses to satisfy the above relationship with the content G of Si element in the first positive electrode active layer (the content of Si element is directly related to the blending amount of the first inorganic ceramic particles), more rapid lithium ion transmission channels can be provided in the negative electrode active layer, the specific surface area of the negative electrode active layer can be increased, and more lithium ion embedding areas can be provided on the surface of the negative electrode active layer, which matches the lithium ion extraction performance of the first positive electrode sheet during charging, enables the negative electrode sheet to receive the lithium ions rapidly detached from the first positive electrode sheet, improves the lithium deposition window, makes lithium deposition less likely to occur, thereby suppressing lithium deposition on the negative electrode interface, enhancing the charging kinetics, and improving the fast charging performance of the battery.

[0080] In some embodiments, the spacing between the recesses is 0.5 mm - 5 mm, and can be, for example, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, or any value within the range formed by any two of the above values. The width of the recess is 0.001 mm - 0.5 mm, such as 0.001 mm, 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, or any value within the range formed by any two of the above values.

[0081] In some preferred embodiments, the recess includes a first recessed groove and a second recessed groove. The present invention further provides a plurality of first recessed grooves and a plurality of second recessed grooves on the negative electrode active layer of the negative electrode sheet, which can provide more rapid lithium ion transmission channels in the negative electrode active layer, increase the specific surface area of the negative electrode active layer, and by adjusting the content G of Si element in the first positive electrode active layer to be adapted to the depths j of the first recessed groove and the second recessed groove, the transmission path of lithium ions during charge and discharge can be optimized, enabling the negative electrode sheet to better receive the lithium ions rapidly detached from the first positive electrode sheet, improving the lithium deposition window, thereby suppressing lithium deposition on the negative electrode interface and enhancing the cycle performance of the battery.

[0082] In some embodiments, referring to Figure 2In the schematic diagram shown, in the thickness direction of the negative electrode sheet, a plurality of first recessed grooves 12 and a plurality of second recessed grooves 13 are provided on the negative electrode active layer 7; the widths of the first recessed grooves 12 and the second recessed grooves 13 are independently h mm, the spacing between the first recessed grooves 12 and the second recessed grooves 13 is independently i mm, the depths of the first recessed grooves 12 and the second recessed grooves 13 are independently j μm, and the distances from the ends of the first recessed grooves 12 and the second recessed grooves 13 to the edge of the negative electrode sheet closest to the ends are independently k mm. The angle between the first recessed groove and the side of the negative electrode sheet with the tab 11 is l°, and the angle between the second recessed groove 13 and the first recessed groove 12 is m°.

[0083] In some embodiments, the mass ratio a of the first inorganic ceramic particles in the first positive electrode active layer satisfies 0.05% ≤ a ≤ 0.20%. In the first recessed groove and the second recessed groove, h satisfies 0.001 mm ≤ h ≤ 0.2 mm, i satisfies 1 mm ≤ i ≤ 5 mm, j satisfies 1 μm ≤ j ≤ 25 μm, k satisfies 0 mm ≤ k ≤ 10 mm, l satisfies 0° ≤ l ≤ 90°, and m satisfies 0° ≤ m ≤ 90°. Among them, h can be 0.001 mm, 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, or any value within the range composed of any two of the above values; i can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, or any value within the range composed of any two of the above values; j can be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, or any value within the range composed of any two of the above values; k can be 0 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, or any value within the range composed of any two of the above values.

[0084] Furthermore, according to the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer, adjusting parameters such as the widths, spacings, and depths of the first recessed groove and the second recessed groove can provide more rapid lithium-ion transport channels in the negative electrode active layer. As the mass ratio of the first inorganic ceramic particles in the first positive electrode active layer increases, the spacing between the first recessed groove and the second recessed groove provided on the negative electrode active layer becomes smaller, the depth of the recessed groove becomes deeper, and the distance from the end of the recessed groove to the edge of the negative electrode sheet closest to the end becomes smaller (as shown in the following listed embodiments), so as to provide more lithium-ion embeddable areas on the surface of the negative electrode active layer, enable the negative electrode sheet to better receive the lithium ions rapidly detached from the first positive electrode sheet, improve the lithium deposition window, inhibit lithium deposition at the negative electrode interface, enhance the kinetics of the battery, and improve the cycle performance of the battery.

[0085] In some embodiments, 0.20% < a ≤ 0.60%, 0.005 mm ≤ h ≤ 0.3 mm, 0.5 mm ≤ i ≤ 5 mm, 10 μm ≤ j ≤ 40 μm, 0 mm ≤ k ≤ 8 mm, 0° ≤ l ≤ 90°, 0° ≤ m ≤ 90°. Among them, h can be 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm or any point value within the range formed by any two of the above values; i can be 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm or any point value within the range formed by any two of the above values; j can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm or any point value within the range formed by any two of the above values; k can be 0 mm, 2 mm, 4 mm, 6 mm, 8 mm or any point value within the range formed by any two of the above values.

[0086] In some embodiments, 0.60% < a ≤ 1.20%, 0.01 mm ≤ h ≤ 0.35 mm, 0.7 mm ≤ i ≤ 4 mm, 15 μm ≤ j ≤ 50 μm, 0 mm ≤ k ≤ 6 mm, 0° ≤ l ≤ 90°, 0° ≤ m ≤ 90°. Among them, h can be 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm or any point value within the range formed by any two of the above values; i can be 0.7 mm, 1 mm, 2 mm, 3 mm, 4 mm or any point value within the range formed by any two of the above values; j can be 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any point value within the range formed by any two of the above values; k can be 0 mm, 2 mm, 4 mm, 6 mm or any point value within the range formed by any two of the above values.

[0087] In some embodiments, 1.20% < a ≤ 1.80%, 0.05 mm ≤ h ≤ 0.5 mm, 0.7 mm ≤ i ≤ 3 mm, 15 μm ≤ j ≤ 100 μm, 0 mm ≤ k ≤ 5 mm, 0° ≤ l ≤ 90°, 0° ≤ m ≤ 90°. Among them, h can be 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.50 mm or any point value within the range composed of any two of the above values; i can be 0.7 mm, 1 mm, 2 mm, 3 mm or any point value within the range composed of any two of the above values; j can be 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 100 μm or any point value within the range composed of any two of the above values; k can be 0 mm, 2 mm, 4 mm, 5 mm or any point value within the range composed of any two of the above values.

[0088] In the present invention, pore-forming treatment can also be performed on the negative electrode active layer in the negative electrode sheet, and a number of concave holes are formed on the surface of the negative electrode active layer. The function is similar to that of providing a number of first concave grooves and a number of second concave grooves on the negative electrode active layer, which can improve the fast charging performance of the battery and reduce lithium plating.

[0089] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0090] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions.

[0091] The present invention will be described in detail below with specific embodiments, and these embodiments are for understanding rather than limiting the present invention.

[0092] Example 1-1

[0093] (1) Prepare the positive electrode sheet

[0094] Preparation of the first positive electrode sheet:

[0095] Lithium cobalt oxide as the positive electrode active material, binder (PVDF), conductive agent (carbon black), and the first inorganic ceramic particles are put into a vacuum mixer according to a mass ratio of 97.6:0.8:1:0.6, and N-methylpyrrolidone (NMP) is added. Under the action of the vacuum mixer, they are fully mixed until a uniform and good-fluidity positive electrode slurry is formed, with a solid content of 73 wt%; the above positive electrode slurry is evenly coated on one side surface of an aluminum foil with a thickness of 20 μm, dried, rolled, slit, and punched to obtain the first positive electrode sheet.

[0096] Among them, the preparation method of the first inorganic ceramic particles includes: using a solution to solidify SiO2 in a high-temperature furnace, cooling it into particles, and then coating a layer of hydrophobic functional silane material with the chemical formula R-Si-X on the surface of the SiO2 particles, where R is CHCl=CH-CH=CHCl; X is monobromomethyl methacrylate monobromide. The first inorganic ceramic particles are SiO2 with a functional silane coated on the surface. The particle size of the first inorganic ceramic particles satisfies: Dv50 is 280 nm, and Dv99 is 360 nm.

[0097] Preparation of the second positive electrode sheet: Lithium cobalt oxide as the positive electrode active material, binder (PVDF), and conductive agent (carbon black) are put into a vacuum mixer according to a mass ratio of 98.2:0.8:1, and N-methylpyrrolidone (NMP) is added. Under the action of the vacuum mixer, they are fully mixed until a uniform and good-fluidity positive electrode slurry is formed, with a solid content of 77 wt%; the above positive electrode slurry is evenly coated on both side surfaces of an aluminum foil with a thickness of 10 μm, dried, rolled, slit, and punched to obtain the second positive electrode sheet.

[0098] (2) Preparation of the negative electrode sheet

[0099] Graphite, silicon-carbon material (mass content of silicon element is 80%), styrene-butadiene rubber (binder), sodium carboxymethyl cellulose (thickener), and acetylene black (conductive agent) are put into a vacuum mixer according to a mass ratio of 84.09:12.01:3.3:0.4:0.2, and deionized water is added. Under the action of the vacuum mixer, they are fully mixed to finally form a uniform and good-fluidity negative electrode slurry, with a solid content of 30 wt%; the above negative electrode slurry is evenly coated on both side surfaces of a copper foil with a thickness of 6 μm, dried, rolled, and die-cut to obtain the negative electrode sheet. Among them, the content g of silicon element in the negative electrode active material is 10%.

[0100] (3) Electrolyte

[0101] The electrolyte is a commercial electrolyte, the solute is lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, the solvent includes ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, and the additives are vinylene carbonate and ethylene sulfate. Among them, the concentration of lithium hexafluorophosphate is 0.6 M, the concentration of lithium bis(fluorosulfonyl)imide is 0.6 M, the mass ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 1:1:1, the mass percentage of vinylene carbonate is 1%, and the mass percentage of ethylene sulfate is 2%.

[0102] (4) Fabricate the battery

[0103] Obtain a bare battery cell by using the positive electrode sheet obtained in step (1), the negative electrode sheet obtained in step (2) and a separator (the separator uses an 8-μm-thick polyethylene separator) according to the conventional (E-stack battery cell) manufacturing process; weld the tabs on the bare battery cell, place it in the battery case, inject the electrolyte prepared in step (3) into the dried and qualified battery cell, and obtain the battery through processes such as standing, aging, formation, degassing, aging and sorting.

[0104] (5) Test the battery

[0105] i) 25°C cycle test: Perform cycle tests on the batteries prepared in the examples and comparative examples. The specific test method is as follows: At 25°C, perform constant current charge and discharge cycling 800T on the battery at a rate of 2.5C (charge) / 1C (discharge) within the charge and discharge cut-off range (3.0V to 4.55V); record the discharge capacity Q1 in the first week and the discharge capacity Q800 in the 800th week, and calculate the capacity retention rate and thickness expansion rate after 800 cycles at 25°C through Q800 / Q1×100%.

[0106] ii) 45°C cycle test: Perform cycle tests on the batteries prepared in the examples and comparative examples. The specific test method is as follows: At 45°C, perform constant current charge and discharge cycling 600T on the battery at a rate of 2.5C (charge) / 1C (discharge) within the charge and discharge cut-off range (3.0V to 4.55V); record the discharge capacity Q1 in the first week and the discharge capacity Q600 in the 600th week, and calculate the capacity retention rate and thickness expansion rate after 600 cycles at 45°C through Q600 / Q1×100%.

[0107] iii) Determine the degree of lithium plating

[0108] Disassemble the fully charged batteries that have been cycled 800T at 25°C and cycled 600T at 45°C, and observe the degree of lithium plating.

[0109] Definition of lithium deposition degree: Observe the lithium deposition situation of the negative electrode sheet. If there is no lithium deposition on the negative electrode sheet, it is recorded as no lithium deposition; if lithium deposition occurs only in the four corner areas of the small sheet, it is recorded as slight lithium deposition; if lithium deposition occurs in the four corner areas and the four sides of the small sheet, it is recorded as lithium deposition; if lithium deposition occurs in the four corner areas, the four sides and the entire surface of the small sheet, it is recorded as severe lithium deposition.

[0110] The first group of Example 1 was carried out with reference to Example 1-1, and the main differences are shown in Table 1. Among them, in the first group of Example 1, the mass ratio a of the first inorganic ceramic particles was adjusted (no inorganic ceramic particles were added to the second positive electrode sheet in the first group of Example 1). No first inorganic ceramic particles were added to the first positive electrode sheet in Comparative Example 1. In Comparative Example 2, a ceramic layer was provided on the outer surface of the first positive electrode sheet away from the battery cell, and the components of the ceramic layer included alumina and PVDF (mixed at a mass ratio of 8:2), and the thickness of the ceramic layer was about 48 μm.

[0111] Table 1

[0112]

[0113] Note: "*" indicates that the corresponding parameter is the same as that in Example 1-1, and " / " indicates that the corresponding component is not added or the parameter cannot be tested.

[0114] As can be seen from Table 1, when the first inorganic ceramic particles are blended in the first positive electrode sheet and the mass ratio of the first inorganic ceramic particles is adjusted to meet the protection scope of the present invention, the problem of easy lithium deposition caused by the single-sided structure of the positive electrode in the stacked lithium-ion battery can be improved, and the cycle performance of the battery can be enhanced.

[0115] The second to fifth groups of Example 2 were carried out with reference to Example 1-1. According to the surface density and compaction density of the second positive electrode sheet, and the surface density and compaction density of the negative electrode sheet, the mass ratio a of the first inorganic ceramic particles and the mass ratio f of the second inorganic ceramic particles were adjusted. The main differences are shown in Table 2. Among them, in the second group of Example 2, the mass ratio of the first inorganic ceramic particles was a1; in the third group of Example 3, the mass ratio of the first inorganic ceramic particles was a2; in the fourth group of Example 4, the mass ratio of the first inorganic ceramic particles was a3; in the fifth group of Example 5, the mass ratio of the first inorganic ceramic particles was a4.

[0116] Table 2

[0117]

[0118]

[0119] As can be seen from Table 2, according to the different surface densities and compaction degrees of the second positive electrode sheet and the negative electrode sheet, the blending amounts of the first inorganic ceramic particles and the second inorganic ceramic particles are adjusted. The higher the surface density and compaction of the electrode sheet, the higher the blending amounts of the first inorganic ceramic particles and the second inorganic ceramic particles, which is more conducive to accelerating the transmission of lithium ions and can alleviate the problem of lithium deposition at the negative electrode interface.

[0120] Examples 6 - 10 were carried out with reference to Example 1 - 1. According to the surface densities of the second positive electrode sheet and the negative electrode sheet, the silicon element content in the negative electrode active material, and the blending amounts of the first inorganic ceramic particles and the second inorganic ceramic particles were adjusted. The main differences are shown in Table 3. Among them, in Example 6, the mass ratio of the first inorganic ceramic particles is a5; in Example 7, the mass ratio of the first inorganic ceramic particles is a6; in Example 8, the mass ratio of the first inorganic ceramic particles is a7; in Example 9, the mass ratio of the first inorganic ceramic particles is a8; in Example 10, the mass ratio of the first inorganic ceramic particles is a9. Comparative Example 3 was carried out with reference to Example 9 - 1, but the first inorganic ceramic particles were not added to the first positive electrode sheet.

[0121] Table 3

[0122]

[0123] The test data of Examples 6 - 10 and Comparative Example 3 are shown in Table 4.

[0124] Table 4

[0125]

[0126] As can be seen from Table 4, the higher the surface densities of the second positive electrode sheet and the negative electrode sheet, the higher the silicon element content in the negative electrode active material, and the higher the blending amounts of the first inorganic ceramic particles and the second inorganic ceramic particles, which can alleviate the lithium deposition at the negative electrode interface caused by the too high surface densities of the positive electrode sheet and the negative electrode sheet, and can also alleviate the problem of the expansion of the negative electrode sheet.

[0127] Examples 11 - 12 were carried out with reference to Example 1 - 1. The difference is that the first concave groove and the second concave groove are provided in the negative electrode sheet, and the widths h, spacings i, depths j, edge distances k of the first concave groove and the second concave groove, as well as the mass ratio a of the first modified ceramic particles and the Si element content G in the first positive electrode active layer are adjusted. See Table 5 for details.

[0128] Table 5

[0129]

[0130]

[0131] As can be seen from Table 5, the first and second recessed grooves provided on the negative electrode active layer are adjusted such that the content G of Si element in the first positive electrode active layer is adapted to the depth j of the first and second recessed grooves, and the width h, spacing i, depth j, and edge distance k of the first and second recessed grooves are adjusted to be adapted to the mass ratio a of the first modified ceramic, which can effectively inhibit lithium deposition at the negative electrode interface and improve the cycling performance of the battery.

[0132] Examples 13 and 14 were carried out with reference to Example 1-1, and the differences are shown in Table 6. Among them, in Example 13, the silicon element content in the first modified ceramic particles was adjusted; in Example 14, the content G of Si element in the first positive electrode active layer was adjusted (changed by adjusting the addition amount a of the first modified ceramic particles).

[0133] Table 6

[0134]

[0135] As can be seen from Table 6, when the silicon element content in the first modified ceramic particles is within the protection scope of the present invention, the problem of lithium deposition on the negative electrode sheet can be improved, and the cycling performance of the battery can be enhanced. In the first positive electrode active layer, when the content G of Si element meets the protection scope of the present invention, it is beneficial to promote the diffusion of lithium ions, enhance the cycling performance of the battery, and reduce lithium deposition.

[0136] Example 15 was carried out with reference to Example 1-1, and the differences are shown in Table 7.

[0137] Table 7

[0138]

[0139] As can be seen from Table 7, changing the types of organic groups coated on the first inorganic ceramic particles can all exert the effects of forming a protective layer and a stable cross-linked network on the surface of the positive electrode active material, effectively improving the problem of lithium deposition on the negative electrode sheet and enhancing the cycling performance of the battery.

[0140] It should be noted that in this text, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or device comprising such element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in a reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0141] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lithium ion secondary battery, characterized in that, It includes a battery cell, and the battery cell includes a stacked positive electrode sheet, a separator, and a negative electrode sheet; The positive electrode sheet includes two first positive electrode sheets and a plurality of second positive electrode sheets. The first positive electrode sheets are located on both sides in the stacking direction of the battery cell, and the second positive electrode sheets are located between the two first positive electrode sheets. The first positive electrode sheet includes a first positive electrode current collector and a first positive electrode active layer provided on the inner side of the first positive electrode current collector facing the battery cell; The second positive electrode sheet includes a second positive electrode current collector and a second positive electrode active layer and a third positive electrode active layer located on opposite sides in the thickness direction of the second positive electrode current collector; The first positive electrode active layer includes a positive electrode active material and first inorganic ceramic particles.

2. The battery according to claim 1, wherein, The first inorganic ceramic particles include an inorganic particle matrix and an organic substance coated on the surface. The organic substance includes at least one group among amino group, vinyl group, propenyl group, epoxy group, methyl group, ethyl group, propyl group, propenyl acryloxy group, 1,3-butadienyl group, alkoxy group, acyloxy group, and ester group; Preferably, based on the total mass of the first positive electrode active layer, the mass ratio of the first inorganic ceramic particles is denoted as a, and a satisfies: 0.05% ≤ a ≤ 2.0%.

3. The battery according to claim 2, wherein, The second positive electrode active layer and / or the third positive electrode active layer include second inorganic ceramic particles; the second inorganic ceramic particles include an inorganic particle matrix and an organic substance coated on the surface. The organic substance includes at least one group among amino group, vinyl group, propenyl group, epoxy group, methyl group, ethyl group, propyl group, propenyl acryloxy group, 1,3-butadienyl group, alkoxy group, acyloxy group, and ester group.

4. The battery according to claim 3, wherein The second positive electrode surface density b satisfies 0.15 mg / cm 2 ≤ b ≤ 40 mg / cm 2 , The single-sided density c of the negative electrode satisfies 0.1 mg / cm 2 ≤ c ≤ 16 mg / cm 2 , The compaction density d of the second positive electrode sheet satisfies 3.8 g / cm 3 ≤ d ≤ 4.5 g / cm 3 , The compaction density e of the negative electrode sheet satisfies 1.3 g / cm 3 ≤ e ≤ 1.90 g / cm 3 ; the mass ratio a of the first inorganic ceramic particles in the first positive electrode active layer satisfies 0.2% ≤ a ≤ 2%, and the mass ratio f of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer satisfies 0.1%a ≤ f ≤ 95%a.

5. The battery according to claim 3, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on at least one side of the negative electrode current collector; the negative electrode active layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material and a carbon-based material; based on the total mass of the negative electrode active material, the content g of silicon element is 3% - 80%, preferably 3% - 35%; Preferably, the silicon-based material includes at least one of silicon-carbon material, silicon-oxygen material, elemental silicon-based material, and silicon alloy material; Preferably, the carbon-based material includes at least one of artificial graphite, natural graphite, hard carbon, soft carbon, and mesophase carbon microspheres; Preferably, the silicon-based material includes silicon-carbon material; the silicon-carbon material includes a porous carbon matrix and a silicon material located in the porous carbon matrix; Preferably, the Dv50 of the silicon-carbon material is 1 μm - 15 μm; Preferably, in the silicon-carbon material, the mass content of silicon element is 20% - 80%.

6. The battery according to claim 5, characterized in that, The mass ratio a of the first inorganic ceramic particles in the first positive electrode active layer satisfies 0.4% ≤ a ≤ 2%, and the mass ratio f of the second inorganic ceramic particles in the second positive electrode active layer and / or the third positive electrode active layer satisfies f ≤ a.

7. The battery according to any one of claims 1-6, characterized in that, The first inorganic ceramic particle matrix and / or the second inorganic ceramic particle matrix includes one or more of silica, alumina, boehmite, magnesia, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, and calcium carbonate; Preferably, the first inorganic ceramic particle matrix and / or the second inorganic ceramic particle matrix includes silica; the silicon element content in the first inorganic ceramic particle and / or the second inorganic ceramic particle is 20%-30%; Preferably, the first inorganic ceramic particle includes Si element, and the content G of Si element is 100 ppm - 3000 ppm based on the total mass of the first positive electrode active layer.

8. The battery according to claim 7, characterized in that, The first inorganic ceramic particle and / or the second inorganic ceramic particle includes a halogen; Preferably, the halogen includes at least one of F, Cl, Br, and I; Preferably, in the first inorganic ceramic particle and / or the second inorganic ceramic particle, the content of F element is 2%-3%, and / or the content of Cl element is 3%-5%, and / or the content of Br element is 2%-4%, and / or the content of I element is 1%-2%; Preferably, the first inorganic ceramic particle includes N element, and / or F element, and / or Cl element; based on the total mass of the first positive electrode active layer, the content of N element is 60 ppm - 2000 ppm; and / or, the content of F element is 10 ppm - 300 ppm; and / or, the content of Cl element is 15 ppm - 1000 ppm.

9. The battery according to any one of claims 1-6, characterized in that, The particle size of the first inorganic ceramic particle and / or the second inorganic ceramic particle independently satisfies: 50 nm ≤ Dv50 ≤ 500 nm, 300 nm ≤ Dv99 ≤ 1000 nm; Preferably, the positive electrode active material includes at least one of lithium cobaltate, ternary lithium nickel cobalt manganate, ternary lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium manganate, and lithium nickelate.

10. The battery according to claim 7, characterized in that, In the thickness direction of the negative electrode sheet, a recess is provided on the negative electrode active layer in the negative electrode sheet, and the depth of the recess is j μm; the relationship between the depth j of the recess and the Si element content G in the first positive electrode active layer satisfies: 0.0043 ≤ j / G ≤ 1; Preferably, the depth j of the recess satisfies: 1 ≤ j ≤ 100; Preferably, the spacing of the recesses is 0.5 mm - 5 mm; Preferably, the width of the recess is 0.001 mm - 0.5 mm.

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