Battery cell, battery device, and electric device

Abstract

The present disclosure provides a battery cell, a battery device, and an electric device. The battery cell comprises an electrolyte layer and a positive electrode layer; a composite positive electrode active material layer in the positive electrode layer comprises a first positive electrode active material layer close to a positive electrode current collector and a second positive electrode active material layer away from the positive electrode current collector, the two layers both comprise positive electrode active material particles and solid-state electrolyte particles, the solid-state electrolyte particles include first solid-state electrolyte particles and second solid-state electrolyte particles, and the Dv50 of the first solid-state electrolyte particles is less than the Dv50 of the second solid-state electrolyte particles; and the mass fraction of the positive electrode active material particles in the first positive electrode active material layer is less than the mass fraction of the positive electrode active material particles in the second positive electrode active material layer, and the mass proportion of the first solid-state electrolyte particles in the solid-state electrolyte particles is less than the mass proportion of the first solid-stare electrolyte particles in the second positive electrode active material layer in the solid-state electrolyte particles. The battery cell of the present disclosure has good cycle performance and rate performance.

Description

Battery cells, battery packs, and electrical devices

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application 202510129894.2, filed on February 5, 2025, entitled “Battery cell, battery device and power supply device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of batteries, and in particular to a battery cell, a battery device, and an electrical device. Background Technology

[0004] Compared to battery cells using liquid electrolytes, solid-state battery cells use solid electrolyte materials, which reduces the risk of combustion and explosion, resulting in high reliability and high energy density. However, the cycle performance and rate performance of solid-state battery cells are still relatively poor. Summary of the Invention

[0005] This disclosure provides a battery cell, a battery device, and an electrical device, wherein the battery cell has good cycle performance and rate performance.

[0006] In a first aspect, this disclosure provides a battery cell comprising an electrolyte layer and a positive electrode layer; the positive electrode layer comprises a positive electrode current collector and a composite positive electrode active material layer located on at least one side of the positive electrode current collector, the composite positive electrode active material layer comprising a first positive electrode active material layer close to the positive electrode current collector and a second positive electrode active material layer away from the positive electrode current collector, both the first and second positive electrode active material layers comprising positive electrode active material particles and solid electrolyte particles, the solid electrolyte particles comprising first solid electrolyte particles and second solid electrolyte particles, the volume distribution particle size Dv50 of the first solid electrolyte particles being smaller than the volume distribution particle size Dv50 of the second solid electrolyte particles; the volume distribution particle size Dv50 of the first solid electrolyte particles being < 1 μm;

[0007] The mass fraction of positive electrode active material particles in the first positive electrode active material layer is less than the mass fraction of positive electrode active material particles in the second positive electrode active material layer; the mass fraction of solid electrolyte particles in the first positive electrode active material layer is greater than the mass fraction of solid electrolyte particles in the second positive electrode active material layer.

[0008] In the first positive electrode active material layer, the mass percentage of the first solid electrolyte particles in the solid electrolyte particles is a%; in the second positive electrode active material layer, the mass percentage of the first solid electrolyte particles in the solid electrolyte particles is b%; where a < b.

[0009] On the one hand, through the gradient design of the composite positive electrode active material layer, the mass fraction of solid electrolyte particles in the first positive electrode active material layer closer to the positive electrode current collector is greater than the mass fraction of the second positive electrode active material layer farther away from the positive electrode current collector. This provides sufficient ion pathways for the first positive electrode active material layer closer to the positive electrode current collector, increases the lithium ion diffusion rate from the electrolyte layer to the first positive electrode active material layer during discharge, improves the uniformity of lithium ion diffusion between the first positive electrode active material layer and the second active material layer, reduces polarization, and improves the structural stability of the positive electrode layer.

[0010] On the other hand, the solid electrolyte particles include relatively small first solid electrolyte particles and relatively large second solid electrolyte particles. In the first positive electrode active material layer, the mass proportion of the first solid electrolyte particles is less than that in the second positive electrode active material layer. The first positive electrode active material layer contains more relatively large second solid electrolyte particles, which reduces ion migration tortuosity, making ion transport paths smoother and improving rate performance. Simultaneously, the high mass fraction of positive electrode active material particles in the second positive electrode active material layer, and the higher mass proportion of the relatively small first solid electrolyte particles, allows for better filling of the gaps between the positive electrode active material particles, forming a denser structure. This further improves the interfacial stability between the positive electrode active material particles and the solid electrolyte, enhancing cycle performance. Therefore, the cycle performance and rate performance of the battery cell disclosed in this invention are improved.

[0011] In some embodiments, the volume distribution particle size Dv50 of the second solid electrolyte particles is 3 μm to 20 μm.

[0012] Therefore, the volume distribution particle size Dv50 of the second solid electrolyte particle is larger than that of the first solid electrolyte particle, which can reduce the tortuosity of lithium ion migration, improve the smoothness of ion transport path, and reduce ion transport resistance.

[0013] In some implementations, 50 ≤ a ≤ 90.

[0014] Therefore, the mass ratio of the first solid electrolyte particles in the first positive electrode active material layer is not less than that of the second solid electrolyte particles, which can increase the contact points with the positive electrode active material particles, which is conducive to building a good ion transport network and improving the ion diffusion capacity of the first positive electrode active material layer.

[0015] In some implementations, 75 ≤ b ≤ 97.

[0016] Therefore, the positive active material particles in the second positive active material layer have a higher mass fraction, and the first solid electrolyte particles in the second positive active material layer account for a larger mass proportion of the solid electrolyte particles. This can improve the ion diffusion capability of the second positive active material layer, allowing more small-diameter first solid electrolyte particles to better fill the gaps between the positive active material particles, increasing solid-solid interface contact, enhancing the mechanical stability of the interface, and promoting capacity utilization.

[0017] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is 40% to 80%.

[0018] In some embodiments, the mass fraction of solid electrolyte particles in the first positive electrode active material layer is 17% to 59%.

[0019] Therefore, with the mass fractions of positive electrode active material particles and solid electrolyte particles in the first positive electrode active material layer within the above-mentioned range, the ion diffusion capability of the first positive electrode active material layer can be improved on the basis of the first positive electrode active material layer having good capacity performance.

[0020] In some embodiments, the mass fraction of the first solid electrolyte particles in the first positive electrode active material layer is 12% to 47%.

[0021] In some embodiments, the mass fraction of the second solid electrolyte particles in the first positive electrode active material layer is 2% to 25%.

[0022] Therefore, if the mass fractions of the first solid electrolyte particles and the second solid electrolyte particles in the first positive electrode active material layer are within the above range, the mass fraction of the solid electrolyte particles in the first positive electrode active material layer can be 17% to 59%.

[0023] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is greater than or equal to 40% and less than 60%, where 50 ≤ a ≤ 80.

[0024] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is 60% to 70%, and 65 ≤ a ≤ 85.

[0025] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is greater than 70% and less than or equal to 80%, where 70 ≤ a ≤ 90.

[0026] Therefore, the gradation effect of the mass fraction of the positive electrode active material particles in the first positive electrode active material layer and the mass ratio of the first solid electrolyte particles in the solid electrolyte particles is better, which is conducive to taking into account cycle performance, rate performance and capacity utilization.

[0027] In some embodiments, the mass fraction of positive electrode active material particles in the second positive electrode active material layer is 80% to 97%.

[0028] In some embodiments, the mass fraction of solid electrolyte particles in the second positive electrode active material layer is 2% to 19%.

[0029] Therefore, the positive electrode active material particles in the second positive electrode active material layer can have a larger mass fraction than those in the first positive electrode active material layer, and it has a high capacity characteristic.

[0030] In some embodiments, the mass fraction of the first solid electrolyte particles in the second positive electrode active material layer is 1.5% to 18.4%.

[0031] In some embodiments, the mass fraction of the second solid electrolyte particles in the second positive electrode active material layer is 0.1% to 4.3%.

[0032] Therefore, if the mass fractions of the first and second solid electrolyte particles in the second positive electrode active material layer are within the above range, the mass fraction of the solid electrolyte particles in the second positive electrode active material layer can be 2% to 19%.

[0033] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is 60% to 70%, and the mass fraction of positive electrode active material particles in the second positive electrode active material layer is 85% to 95%.

[0034] Therefore, when the mass fraction of the positive electrode active material particles is within the above range, the polarization between the two layers can be reduced, the interfacial compatibility and stability between the two layers can be improved, and the cycle performance can be better.

[0035] In some embodiments, the first solid electrolyte particle has an ionic conductivity of 1 mS / cm to 5 mS / cm at 25°C.

[0036] In some embodiments, the second solid electrolyte particles have an ionic conductivity of 5 mS / cm to 50 mS / cm at 25°C.

[0037] Therefore, the second solid electrolyte particle has a higher ionic conductivity than the first solid electrolyte particle, resulting in a stronger ion transport capability.

[0038] In some embodiments, the ionic conductivity of the first solid electrolyte particle at 25°C is less than that of the second solid electrolyte particle at 25°C.

[0039] In some embodiments, the thickness of the composite positive electrode active material layer is 50 μm to 200 μm.

[0040] In some embodiments, the thicknesses of the first positive electrode active material layer and the second positive electrode active material layer are each independently 20 μm to 50 μm.

[0041] In some embodiments, the solid electrolyte particles include one or more of sulfide electrolytes and halide electrolytes.

[0042] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material particles is 2 μm to 10 μm.

[0043] Therefore, the volume distribution particle size Dv50 of the positive electrode active material particles is within the above range, which results in a better gradation effect with the first solid electrolyte particles and the second solid electrolyte particles, thereby improving the mechanical stability and structural integrity of the positive electrode layer.

[0044] In some embodiments, the positive electrode active material particles include one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds.

[0045] In some embodiments, the first positive electrode active material layer and the second positive electrode active material layer each independently include a conductive agent and a binder.

[0046] In some embodiments, the mass fraction of the conductive agent in the first positive electrode active material layer or the second positive electrode active material layer is independently 1% to 3%.

[0047] In some embodiments, the mass fraction of the binder in the first positive electrode active material layer or the second positive electrode active material layer is independently 1% to 2%.

[0048] Secondly, embodiments of this disclosure provide a battery device comprising a plurality of battery cells according to any embodiment of the first aspect of this disclosure.

[0049] Thirdly, embodiments of this disclosure provide an electrical device comprising a plurality of battery cells according to any embodiment of the first aspect of this disclosure, or electrical energy provided by a battery device according to any embodiment of the second aspect of this disclosure. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0051] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present disclosure;

[0052] Figure 2 is a schematic diagram of an electrical device according to an embodiment of the present disclosure.

[0053] The following is an explanation of the reference numerals in the attached diagram: 5. Battery cell;

[0054] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0055] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery module, battery cell, battery assembly, and power-consuming device of this disclosure. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0056] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0057] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0058] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0059] Unless otherwise specified, all steps of this disclosure may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if it is mentioned that the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0060] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0061] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0062] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0063] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0064] The battery cells mentioned in the embodiments of this disclosure are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and this disclosure does not limit this. Figure 1 shows a cuboid battery cell 5 as an example.

[0065] The battery cells provided in the embodiments of this disclosure may include, but are not limited to, lithium battery cells and sodium battery cells, such as lithium-ion battery cells, sodium-ion battery cells, lithium metal battery cells, sodium metal battery cells, etc. The battery cells provided in the embodiments of this disclosure include electrode assemblies.

[0066] The electrode assembly can be a wound structure or a stacked structure, and this disclosure does not limit this. The battery cell also includes an outer packaging, which can be used to encapsulate the electrode assembly. The outer packaging can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0067] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar. In some embodiments, the battery cell assembly is typically formed by arranging multiple battery cells.

[0068] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0069] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0070] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0071] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0072] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0073] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0074] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0075] The technical solutions described in this disclosure are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Battery cells and battery devices are used to store or provide electrical energy.

[0076] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0077] The battery cell disclosed herein may be a solid-state battery cell.

[0078] In solid-state battery cells, the areal capacity density of the positive electrode can be improved by preparing a composite positive electrode active material layer. However, as the areal capacity density of the positive electrode increases, the thickness of the composite positive electrode active material layer also increases, resulting in an uneven distribution of the internal electric field. The degree of lithium insertion / extraction in the positive electrode varies at different thicknesses of the positive electrode active material layer. As cycling progresses, this difference at different thicknesses gradually increases, leading to intensified polarization during charging and discharging of the positive electrode and poor cycle performance.

[0079] Meanwhile, due to the non-uniformity of the electric field, the number of lithium ions diffusing from the electrolyte layer to the positive electrode active material layer during discharge decreases as the discharge progresses. This results in a lack of lithium ion pathways in the positive electrode active material layer that is far from the electrolyte layer, leading to poor rate performance.

[0080] In view of the above problems, this disclosure proposes a battery cell with good cycle performance and rate performance.

[0081] The battery cell provided in this disclosure includes an electrolyte layer and a positive electrode layer. The positive electrode layer includes a positive electrode current collector and a composite positive electrode active material layer located on at least one side of the positive electrode current collector. The composite positive electrode active material layer includes a first positive electrode active material layer close to the positive electrode current collector and a second positive electrode active material layer away from the positive electrode current collector. Both the first and second positive electrode active materials layers include positive electrode active material particles and solid electrolyte particles. The solid electrolyte particles include first solid electrolyte particles and second solid electrolyte particles. The volume distribution particle size Dv50 of the first solid electrolyte particles is smaller than that of the second solid electrolyte particles. Particle size Dv50; Volume distribution of the first solid electrolyte particles: particle size Dv50 < 1 μm; Mass fraction of positive electrode active material particles in the first positive electrode active material layer is less than that in the second positive electrode active material layer; Mass fraction of solid electrolyte particles in the first positive electrode active material layer is greater than that in the second positive electrode active material layer; Mass percentage of the first solid electrolyte particles in the first positive electrode active material layer is a%; Mass percentage of the first solid electrolyte particles in the second positive electrode active material layer is b%; where a < b.

[0082] On the one hand, through the gradient design of the composite positive electrode active material layer, the mass fraction of solid electrolyte particles in the first positive electrode active material layer closer to the positive electrode current collector is greater than the mass fraction of the second positive electrode active material layer farther away from the positive electrode current collector. This provides sufficient ion pathways for the first positive electrode active material layer closer to the positive electrode current collector, increases the lithium ion diffusion rate from the electrolyte layer to the first positive electrode active material layer during discharge, improves the uniformity of lithium ion diffusion between the first positive electrode active material layer and the second active material layer, reduces polarization, and improves the structural stability of the positive electrode layer.

[0083] On the other hand, the solid electrolyte particles include relatively small first solid electrolyte particles and relatively large second solid electrolyte particles. In the first positive electrode active material layer, the mass proportion of the first solid electrolyte particles is less than that in the second positive electrode active material layer. The first positive electrode active material layer contains more relatively large second solid electrolyte particles, which reduces ion migration tortuosity, making ion transport paths smoother and improving rate performance. Simultaneously, the high mass fraction of positive electrode active material particles in the second positive electrode active material layer, and the higher mass proportion of the relatively small first solid electrolyte particles, allows for better filling of the gaps between the positive electrode active material particles, forming a denser structure. This further improves the interfacial stability between the positive electrode active material particles and the solid electrolyte, enhancing cycle performance. Therefore, the cycle performance and rate performance of the battery cell disclosed in this invention are improved.

[0084] For example, the volume distribution particle size Dv50 of the first solid electrolyte particles can be any two of the above values, which are 0.01 μm, 0.02 μm, 0.03 μm, 0.04, 0.05 μm, 0.055 μm, 0.06 μm, 0.065 μm, 0.07 μm, 0.075 μm, 0.08 μm, 0.085 μm, 0.09 μm, 0.095 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 0.95 μm, or <1 μm.

[0085] In some embodiments, the volume distribution particle size Dv50 of the first solid electrolyte particles is greater than or equal to 0.05 μm.

[0086] For example, the volume distribution particle size Dv50 of the first solid electrolyte particles can be 0.05μm, 0.055μm, 0.06μm, 0.065μm, 0.07μm, 0.075μm, 0.08μm, 0.085μm, 0.09μm, 0.095μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 0.95μm, or <1μm, which is a range consisting of any two of the above values.

[0087] For example, the volume distribution particle size Dv50 of the first solid electrolyte particles can be 0.05μm~0.99μm, 0.1μm~0.95μm, 0.2μm~0.90μm, or 0.3μm~0.8μm.

[0088] The technical solutions of the embodiments disclosed herein will now be described in detail.

[0089] [Positive electrode layer]

[0090] In some embodiments, the positive electrode layer includes a positive electrode current collector and a composite positive electrode active material layer located on at least one side of the positive electrode current collector. The composite positive electrode active material layer includes a first positive electrode active material layer close to the positive electrode current collector and a second positive electrode active material layer away from the positive electrode current collector. Both the first and second positive electrode active material layers include positive electrode active material particles and solid electrolyte particles. The solid electrolyte particles include first solid electrolyte particles and second solid electrolyte particles. The volume distribution particle size Dv50 of the first solid electrolyte particles is smaller than the volume distribution particle size Dv50 of the second solid electrolyte particles. The volume distribution particle size Dv50 of the first solid electrolyte particles is < 1 μm.

[0091] The mass fraction of positive electrode active material particles in the first positive electrode active material layer is less than the mass fraction of positive electrode active material particles in the second positive electrode active material layer; the mass fraction of solid electrolyte particles in the first positive electrode active material layer is greater than the mass fraction of solid electrolyte particles in the second positive electrode active material layer.

[0092] In the first positive electrode active material layer, the mass percentage of the first solid electrolyte particles in the solid electrolyte particles is a%; in the second positive electrode active material layer, the mass percentage of the first solid electrolyte particles in the solid electrolyte particles is b%; where a < b.

[0093] In this embodiment, the positive electrode layer to be tested can be taken and continuously peeled off using a tensile testing machine until the positive electrode current collector and the composite positive electrode active material layer are completely separated. Samples can be taken from a thickness range of no more than 20 μm on the side of the composite positive electrode active material layer near the positive electrode current collector to test the mass fraction of positive electrode active material particles and solid electrolyte particles in the first positive electrode active material layer, as well as the mass ratio of the first and second solid electrolyte particles in the solid electrolyte particles. Samples can also be taken from a thickness range of no more than 20 μm on the side of the composite positive electrode active material layer away from the positive electrode current collector to test the mass fraction of positive electrode active material particles and solid electrolyte particles in the second positive electrode active material layer, as well as the mass ratio of the first and second solid electrolyte particles in the solid electrolyte particles.

[0094] In some embodiments, the volume distribution particle size Dv50 of the second solid electrolyte particles is 3 μm to 20 μm.

[0095] The volume distribution particle size Dv50 of the second solid electrolyte particles is larger than that of the first solid electrolyte particles. The larger particle size can reduce the tortuosity of lithium ion migration, improve the smoothness of ion transport path, and reduce ion transport resistance.

[0096] For example, the volume distribution particle size Dv50 of the second solid electrolyte particles can be 3μm, 6μm, 9μm, 12μm, 15μm, 17μm, 18μm, 19μm, 20μm, or any range of two of the above values.

[0097] For example, the volume distribution particle size Dv50 of the second solid electrolyte particles can be 3μm~19μm, 6μm~18μm, 9μm~17μm, 9μm~15μm, or 9μm~12μm.

[0098] In this embodiment, Dv50 can be determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The specific principle involves dispersing the particle sample at an appropriate concentration in a suitable liquid and gas, allowing it to pass through a monochromatic beam (usually a laser). When the light encounters the particles, it scatters at different angles. A multi-element detector measures the scattered light, storing these values ​​related to the scattering pattern for subsequent analysis. Through appropriate optical models and mathematical processes, these quantified scattering data are converted to obtain a series of discrete particle size ranges representing the percentage of particle volume relative to the total particle volume, thus yielding the particle size volume distribution. Dv50 represents the particle size corresponding to a cumulative volume distribution percentage of 50%.

[0099] In some implementations, 40 ≤ a ≤ 90.

[0100] For example, 'a' can be 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or a range of any two of the above values.

[0101] In some implementations, 50 ≤ a ≤ 90.

[0102] For example, 'a' can be 50-85, 55-85, 65-85, 70-85, or 70-80.

[0103] The mass percentage of the first solid electrolyte particles in the first positive electrode active material layer is not less than that of the second solid electrolyte particles. This increases the contact points with the positive electrode active material particles, which is beneficial for building a good ion transport network and improving the ion diffusion capability of the first positive electrode active material layer.

[0104] In some implementations, 55≤b≤97, and optionally 75≤b≤97.

[0105] Therefore, the positive active material particles in the second positive active material layer have a higher mass fraction, and the first solid electrolyte particles in the second positive active material layer account for a larger mass proportion of the solid electrolyte particles. This can improve the ion diffusion capability of the second positive active material layer, allowing more small-diameter first solid electrolyte particles to better fill the gaps between the positive active material particles, increasing solid-solid interface contact, enhancing the mechanical stability of the interface, and promoting capacity utilization.

[0106] For example, b can be 55, 60, 65, 70, 75, 78, 81, 84, 87, 90, 93, 96, 97, 95 or a range of any two of the above values.

[0107] For example, b can be 75-97, 80-97, 85-97, 90-97, or 93-95.

[0108] In some embodiments, the mass fraction of the positive electrode active material particles in the first positive electrode active material layer is 40% to 80%.

[0109] In some embodiments, the mass fraction of the solid electrolyte particles in the first positive electrode active material layer is 17% to 59%.

[0110] When the mass fractions of positive electrode active material particles and solid electrolyte particles in the first positive electrode active material layer are within the above-mentioned range, the ion diffusion capability of the first positive electrode active material layer can be improved on the basis of the first positive electrode active material layer having good capacity performance.

[0111] For example, the mass fraction of the positive electrode active material particles in the first positive electrode active material layer can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any range of two of the above values.

[0112] For example, the mass fraction of the positive electrode active material particles in the first positive electrode active material layer can be 45%–80%, 50%–80%, 55%–80%, 60%–80%, 45%–75%, 50%–75%, 55%–75%, or 60%–75%.

[0113] For example, the mass fraction of solid electrolyte particles in the first positive electrode active material layer can be 17%, 21%, 25%, 29%, 33%, 37%, 41%, 45%, 49%, 53%, 57%, 59%, or any range of two of the above values.

[0114] For example, the mass fraction of solid electrolyte particles in the first positive electrode active material layer can be 21%–59%, 21%–57%, 21%–49%, 21%–45%, 21%–41%, 21%–37%, 21%–33%, 25%–45%, 25%–41%, 25%–37%, or 25%–33%.

[0115] In some embodiments, the mass fraction of the first solid electrolyte particles in the first positive electrode active material layer is 10% to 47%, optionally 12% to 47%.

[0116] In some embodiments, the mass fraction of the second solid electrolyte particles in the first positive electrode active material layer is 2% to 25%.

[0117] If the mass fractions of the first and second solid electrolyte particles in the first positive electrode active material layer are within the above range, the mass fraction of the solid electrolyte particles in the first positive electrode active material layer can be 17% to 59%.

[0118] For example, the mass fraction of the first solid electrolyte particles in the first positive electrode active material layer can be 10%, 11%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 47%, or any range of two of the above values.

[0119] For example, the mass fraction of the first solid electrolyte particles in the first positive electrode active material layer can be 14%–42%, 16%–40%, 18%–40%, 18%–38%, 18%–36%, 18%–34%, 18%–30%, 18%–28%, 18%–26%, 18%–24%, or 18%–22%.

[0120] For example, the mass fraction of the second solid electrolyte particles in the first positive electrode active material layer can be 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 25%, or any combination of two of the above values.

[0121] For example, the mass fraction of the second solid electrolyte particles in the first positive electrode active material layer can be 4%–24%, 4%–22%, 4%–20%, 4%–18%, 4%–16%, 4%–12%, 4%–10%, or 4%–8%.

[0122] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is greater than or equal to 40% and less than 60%, where 50 ≤ a ≤ 80.

[0123] For example, the mass fraction of the positive electrode active material particles in the first positive electrode active material layer can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 59%, or any range of two of the above values, and a can be 50, 55, 60, 65, 70, 75, 80, 72, 78, 80, or any range of two of the above values.

[0124] In some embodiments, the mass fraction of the positive electrode active material particles in the first positive electrode active material layer is 60% to 70%, and 65 ≤ a ≤ 85.

[0125] The gradation effect of the mass fraction of the positive electrode active material particles in the first positive electrode active material layer and the mass ratio of the first solid electrolyte particles in the solid electrolyte particles is better, which is conducive to taking into account cycle performance, rate performance and capacity utilization.

[0126] For example, the mass fraction of the positive electrode active material particles in the first positive electrode active material layer can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, or any range of two of the above values, and 'a' can be 65, 68, 70, 72, 75, 78, 80, 82, 84, 85, or any range of two of the above values.

[0127] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is greater than 70% and less than or equal to 80%, where 70 ≤ a ≤ 90.

[0128] For example, the mass fraction of the positive electrode active material particles in the first positive electrode active material layer can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or any range of two of the above values, and 'a' can be 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90%, or any range of two of the above values.

[0129] In some embodiments, the mass fraction of the positive electrode active material particles in the second positive electrode active material layer is 80% to 97%.

[0130] The positive electrode active material particles in the second positive electrode active material layer can have a larger mass fraction than those in the first positive electrode active material layer, and it also has a high capacity characteristic.

[0131] For example, the mass fraction of the positive electrode active material particles in the second positive electrode active material layer can be 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 97%, or any range of two of the above values.

[0132] For example, the mass fraction of the positive electrode active material particles in the second positive electrode active material layer can be 82%–97%, 82%–96%, 82%–94%, 82%–92%, 84%–96%, 84%–94%, 86%–96%, 86%–94%, or 88%–94%.

[0133] In some embodiments, the mass fraction of solid electrolyte particles in the second positive electrode active material layer is 2% to 19%.

[0134] For example, the mass fraction of solid electrolyte particles in the second positive electrode active material layer can be 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 19%, or any combination of two of the above values.

[0135] For example, the mass fraction of solid electrolyte particles in the second positive electrode active material layer can be 4%–18%, 4%–16%, 4%–14%, 4%–12%, 4%–10%, or 4%–8%.

[0136] In some embodiments, the mass fraction of the first solid electrolyte particles in the second positive electrode active material layer is 1.5% to 18.4%.

[0137] For example, the mass fraction of the first solid electrolyte particles in the second positive electrode active material layer can be 1.5%, 3.5%, 5.5%, 7.5%, 9.5%, 11.5%, 13.5%, 15.5%, 17.5%, 18.4%, or any range of two of the above values.

[0138] For example, the mass fraction of the first solid electrolyte particles in the second positive electrode active material layer can be 3.5% to 17.5%, 3.5% to 15.5%, 3.5% to 11.5%, 3.5% to 9.5%, or 3.5% to 7.5%.

[0139] In some embodiments, the mass fraction of the second solid electrolyte particles in the second positive electrode active material layer is 0.1% to 4.3%.

[0140] For example, the mass fraction of the second solid electrolyte particles in the second positive electrode active material layer can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, 2.1%, 2.3%, 2.5%, 2.7%, 2.9%, 3.1%, 3.3%, 3.5%, 3.7%, 3.9%, 4.1%, 4.3%, or any range of two of the above values.

[0141] For example, the mass fraction of the second solid electrolyte particles in the second positive electrode active material layer can be 0.1%–3.5%, 0.1%–2.5%, 0.1%–1.5%, 0.1%–1.1%, 0.1%–0.9%, or 0.1%–0.5%.

[0142] In some embodiments, the mass fraction of positive electrode active material particles in the first positive electrode active material layer is 60% to 70%, and the mass fraction of positive electrode active material particles in the second positive electrode active material layer is 85% to 95%.

[0143] When the mass fraction of the positive electrode active material particles is within the above range, the polarization between the two layers can be reduced, the interfacial compatibility and stability between the two layers can be improved, and the cycle performance can be better.

[0144] In some embodiments, the first solid electrolyte particle has an ionic conductivity of 1 mS / cm to 5 mS / cm at 25°C.

[0145] For example, the ionic conductivity of the first solid electrolyte particle at 25°C can be 1 mS / cm, 1.5 mS / cm, 2 mS / cm, 2.5 mS / cm, 3 mS / cm, 3.5 mS / cm, 4 mS / cm, 4.5 mS / cm, 4.8 mS / cm, 5 mS / cm, or any combination of two of the above values.

[0146] In some embodiments, the second solid electrolyte particles have an ionic conductivity of 5 mS / cm to 50 mS / cm at 25°C.

[0147] The second solid electrolyte particles have a higher ionic conductivity than the first solid electrolyte particles, resulting in stronger ion transport capabilities.

[0148] For example, the ionic conductivity of the second solid electrolyte particles at 25°C can be 5 mS / cm, 10 mS / cm, 15 mS / cm, 20 mS / cm, 25 mS / cm, 30 mS / cm, 35 mS / cm, 40 mS / cm, 45 mS / cm, 50 mS / cm, or any combination of two of the above values.

[0149] For example, the ionic conductivity of the second solid electrolyte particles at 25°C can be 5mS / cm~40mS / cm, 5mS / cm~30mS / cm, 5mS / cm~20mS / cm, 5mS / cm~15mS / cm, 10mS / cm~35mS / cm, 10mS / cm~30mS / cm, or 10mS / cm~20mS / cm.

[0150] In some embodiments, the ionic conductivity of the first solid electrolyte particle at 25°C is less than that of the second solid electrolyte particle at 25°C.

[0151] In this embodiment of the disclosure, the ionic conductivity can be tested as follows: using the blocking electrode method, the blocking electrode is prepared by preparing a solid electrolyte particle sheet with a diameter of 6 mm and a thickness of about 1.3 mm. The blocking electrode is a metal thin film with a diameter of 6 mm formed by magnetron sputtering. A Solartron 1260A frequency response analyzer is used, and the test frequency range is usually 1 MHz to 1 Hz, the voltage amplitude is 10 mV, and the temperature is 25 °C.

[0152] In some embodiments, the thickness of the composite positive electrode active material layer is 50 μm to 200 μm.

[0153] For example, the thickness of the composite positive electrode active material layer can be 50μm, 75μm, 100μm, 125μm, 150μm, 175μm, 200μm, 110μm, 130μm, 190μm or any range of two of the above values.

[0154] For example, the thickness of the composite positive electrode active material layer can be 50μm~190μm, 50μm~110μm, 50μm~90μm, 55μm~175μm, 55μm~150μm, 55μm~130μm, 55μm~90μm, 60μm~110μm, 60μm~90μm, or 65μm~90μm.

[0155] In some embodiments, the thickness of the first positive electrode active material layer and the second positive electrode active material layer are each independently 10 μm to 100 μm, and can be selected as 20 μm to 50 μm.

[0156] For example, the thickness of the first positive electrode active material layer and the second positive electrode active material layer can each be independently 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, 34μm, 36μm, 38μm, 40μm, 42μm, 44μm, 46μm, 48μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm or any range of two of the above values.

[0157] For example, the thicknesses of the first positive electrode active material layer and the second positive electrode active material layer can be independently 20μm~80μm, 20μm~70μm, 20μm~60μm, 20μm~55μm, 20μm~50μm, 20μm~40μm, 30μm~80μm, 30μm~70μm, and 30μm~60μm.

[0158] In this embodiment, the thickness of the positive electrode active material layer can be obtained by taking the average value of multiple measurements with a micrometer.

[0159] In some embodiments, the solid electrolyte particles include one or more of sulfide electrolytes and halide electrolytes.

[0160] In some embodiments, the sulfide electrolyte may include, but is not limited to, one or more of the following sulfide solid electrolyte materials: silver-germanium sulfide type, LGPS type, lithium sulfide-phosphorus pentasulfide complex type.

[0161] Optionally, the argyrodite-type sulfide solid electrolyte material may include a material with the chemical formula Li 6±s P 1-j A j S 5±s- t B t X 1±s , where 0 ≤ j < 1, 0 ≤ t < 1, 0 ≤ s < 1, A includes one or more elements selected from Ge, Si, Sn, and Sb, B includes one or more elements selected from O, Se, and Te, and X includes one or more elements selected from Cl, Br, I, and F.

[0162] Optionally, the LGPS-type sulfide solid electrolyte material may include a material with the chemical formula Li 10±δ5 Ge 1-g G g P 2-q Q q S 12- w Ww, where 0 ≤ δ5 < 1, 0 ≤ g ≤ 1, 0 ≤ q ≤ 2, 0 ≤ w < 1, G includes one or two elements selected from Si and Sn, Q includes Sb, and W includes one or more elements selected from O, Se, Te, Cl, Br, I, and F.

[0163] Optionally, the lithium sulfide - phosphorus pentasulfide composite-type sulfide solid electrolyte material may include a material with the chemical formula (100 - u - v)Li2S·uP2S5·vM m N n , where 0 < u < 100, 0 ≤ v < 100, 0 ≤ u + v < 100, 0 ≤ m < 4, 0 ≤ n < 6, M includes one or more elements selected from Li, B, Ge, Si, Sn, and Sb, and N includes one or more elements selected from S, Se, Te, O, Cl, Br, I, and F.

[0164] In some embodiments, by way of example, the sulfide solid electrolyte material may include one or more of Li6PS5Cl, Li6PS5Br, Li 10 GeP2S 12 , Li3PS4, Li7P3S 11 , Li2S - GeS2, Li2S - P2S5, Li2S - SiS 2、 Li2S - MeS2 - P2S5 (Me = Si, Ge, Sn, Al, etc.). <{

[0165] In some embodiments, the halide electrolyte may include one or more of Li3YCl6, Li3YBr6, Li3ErCl6, Li3InCl6, Li3InBr6.

[0166] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material particles is 2 μm to 10 μm.

[0167] The positive electrode active material particles with a volume distribution particle size Dv50 within the above range have a better gradation effect with the first and second solid electrolyte particles, which can improve the mechanical stability and structural integrity of the positive electrode layer.

[0168] For example, the volume distribution particle size Dv50 of the positive electrode active material particles can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any range of two of the above values.

[0169] In some embodiments, the positive electrode active material particles include one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds.

[0170] Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures.

[0171] Examples of metal chalcogenides may include, but are not limited to, one or more of iron sulfide, cobalt sulfide, nickel sulfide, manganese sulfide, copper sulfide, molybdenum disulfide, tungsten disulfide, antimony sulfide, bismuth sulfide, lead sulfide, and their respective modified compounds.

[0172] Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and one or more of their respective modified compounds.

[0173] In some embodiments, the first positive electrode active material layer and the second positive electrode active material layer each independently include a conductive agent and a binder.

[0174] In some embodiments, the mass fraction of the conductive agent in the first positive electrode active material layer or the second positive electrode active material layer is independently 1% to 3%.

[0175] For example, the mass fraction of the conductive agent can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, or any range of two of the above values.

[0176] In some embodiments, the mass fraction of the binder in the first positive electrode active material layer or the second positive electrode active material layer is independently 1% to 2%.

[0177] For example, the mass fraction of the adhesive can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any range of two of the above values.

[0178] In some embodiments, the conductive agent may be one or more of the following: conductive graphite (such as KS-6, SFG-6), superconducting carbon, acetylene black, carbon black (such as SP), Ketjen black (such as ECP), carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0179] In some embodiments, the adhesive may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, water-soluble unsaturated resin SR-1B, methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-butadiene rubber (SBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, cis-8 butadiene rubber (BR), ethyl cellulose, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), fluororubber, and acrylate rubber.

[0180] In some embodiments, the positive current collector can be a metal foil or a composite current collector. Examples of metal foils include stainless steel foil, carbon-coated aluminum foil, aluminum foil, nickel foil, and titanium foil. The composite current collector can include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0181] [Negative electrode layer]

[0182] In some embodiments, the battery cell further includes a negative electrode layer, which may include one or more of lithium, lithium alloy, natural graphite, artificial graphite, mesophase micro carbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and metal oxides.

[0183] Optionally, the mass fraction of lithium in the lithium alloy can be above 90%.

[0184] Optionally, other elements in the lithium alloy may include, but are not limited to, one or more of In, Mg, Al, Zn, Sn, Ag, Au, Ga, Pt, and Fe.

[0185] Alternatively, the lithium alloy may include, but is not limited to, Li-In alloy, Li-Mg alloy, Li-Al alloy, Li-Zn alloy, Li-Fe alloy, etc.

[0186] Optionally, the silicon-based material may include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.

[0187] Optionally, the tin-based material may include, but is not limited to, one or more of elemental tin, tin oxide, and tin alloy materials.

[0188] Optionally, the metal oxide may be one or more of TiO2, MoO2, In2O3, Al2O3, Cu2O, VO2, Ga2O3, Sb2O5, and Bi2O5.

[0189] In some embodiments, the negative electrode layer may further include a negative electrode binder, which may include, but is not limited to, one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS), methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, cis-butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0190] In some embodiments, the negative electrode layer may include a negative electrode conductive agent, which may include, but is not limited to, one or more of conductive graphite (such as KS-6, SFG-6), superconducting carbon, acetylene black, carbon black (such as SP), Ketjen black (such as ECP), carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0191] In some embodiments, the negative electrode current collector can be a metal foil, a three-dimensional porous current collector, or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, and aluminum foam. A composite current collector can include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer material substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0192] [Electrolyte layer]

[0193] In some embodiments, the electrolyte layer includes solid electrolyte particles, which can be referenced to the solid electrolyte particles in the positive electrode layer, and will not be described in detail here.

[0194] In some embodiments, the electrolyte layer may further include an adhesive. Optionally, the adhesive may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, water-soluble unsaturated resin SR-1B, methyl vinyl silicone rubber, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), styrene-butadiene rubber (SBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, butadiene rubber (BR), ethyl cellulose, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), fluororubber, and acrylate rubber.

[0195] Example

[0196] The following embodiments describe the contents disclosed in this disclosure in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0197] Example 1

[0198] 1. Preparation of the positive electrode layer

[0199] Provides positive electrode active material particles LiNi 0.8 Co 0.1 Mn 0.1 O2, with a volume distribution particle size Dv50 of 3 μm; the first solid electrolyte particle Li6PS5Cl, with a volume distribution particle size Dv50 of 0.9 μm and an ionic conductivity of 5 mS / cm at 25℃; the second solid electrolyte particle Li6PS5Cl, with a volume distribution particle size Dv50 of 10 μm and an ionic conductivity of 12 mS / cm at 25℃.

[0200] Preparation of the first positive electrode active material layer: The above-mentioned positive electrode active material particles, the above-mentioned two types of sulfide solid electrolyte particles with different particle sizes (i.e., the first solid electrolyte particles and the second solid electrolyte particles), and conductive agent carbon black particles are uniformly mixed for 20 minutes to obtain a composite positive electrode powder. Then, polyvinylidene fluoride binder is added, and it is rolled into a positive electrode film. In the first positive electrode active material layer, the mass fractions of positive electrode active material particles, sulfide solid electrolyte particles, conductive agent, and binder are 70%, 26%, 2%, and 2%, respectively; the mass ratio of the first solid electrolyte particles to the second solid electrolyte particles is 80:20.

[0201] Preparation of the second positive electrode active material layer: The above-mentioned positive electrode active material particles are uniformly mixed with the above-mentioned two types of sulfide solid electrolyte particles of different particle sizes (i.e., the first solid electrolyte particles and the second solid electrolyte particles) and conductive agent carbon black particles for 20 minutes to obtain a composite positive electrode powder. Then, polyvinylidene fluoride binder is added and rolled into a positive electrode film. In the second positive electrode active material layer, the mass fractions of positive electrode active material particles, sulfide solid electrolyte particles, conductive agent and binder are 90%, 6%, 2% and 2%, respectively; the mass ratio of the first solid electrolyte particles to the second solid electrolyte particles is 95:5.

[0202] Preparation of the positive electrode layer: The two positive electrode active material layers are stacked sequentially between the positive electrode current collector aluminum foil and the electrolyte layer, wherein the first positive electrode active material layer is close to the positive electrode current collector aluminum foil and the second positive electrode active material layer is far away from the positive electrode current collector aluminum foil.

[0203] 2. Preparation of the negative electrode layer

[0204] The negative electrode layer is a lithium-indium alloy, in which the molar ratio of Li to In is 1:3.

[0205] 3. Preparation of the electrolyte layer

[0206] It is made by pressing the sulfide electrolyte Li6PS5Cl into sheets.

[0207] 4. Preparation of solid-state battery cells

[0208] In the molded battery system, solid-state battery cells are pressed into layers of positive electrode, electrolyte, and negative electrode in the order from top to bottom under a pressure of 10 MPa and then encapsulated in a molded battery fixture with an external pressure of 50 MPa.

[0209] Examples 2-5

[0210] Solid-state battery cells were prepared using a method similar to that of Example 1, with the different parameters shown in Table 1.

[0211] Comparative Example 1

[0212] 1. Preparation of the positive electrode layer

[0213] Provides positive electrode active material particles LiNi 0.8 Co 0.1 Mn 0.1 O2 has a volume distribution particle size Dv50 of 3 μm; the first solid electrolyte particle, Li6PS5Cl, has a volume distribution particle size Dv50 of 0.90 μm and an ionic conductivity of 5 mS / cm.

[0214] Preparation of the positive electrode active material layer: The above-mentioned positive electrode active material particles, the above-mentioned first solid electrolyte particles, and conductive agent carbon black particles were uniformly mixed for 20 min to obtain a composite positive electrode powder. Then, polyvinylidene fluoride (PVDF) binder was added, and the mixture was rolled into a positive electrode film. In the positive electrode active material layer, the mass fractions of the positive electrode active material particles, the first solid electrolyte particles, the conductive agent, and the binder were 80%, 16%, 2%, and 2%, respectively.

[0215] Preparation of the positive electrode layer: The above-mentioned positive electrode active material layers are stacked sequentially between the positive electrode current collector aluminum foil and the electrolyte layer.

[0216] 2. Preparation of the negative electrode layer

[0217] The negative electrode layer is a lithium-indium alloy, in which the molar ratio of Li to In is 1:3.

[0218] 3. Preparation of the electrolyte layer

[0219] It is made by pressing the sulfide electrolyte Li6PS5Cl into sheets.

[0220] 4. Preparation of solid-state battery cells

[0221] In the molded battery system, solid-state battery cells are pressed into layers of positive electrode, electrolyte, and negative electrode in the order from top to bottom under a pressure of 10 MPa and then encapsulated in a molded battery fixture with an external pressure of 50 MPa.

[0222] Comparative Example 2

[0223] 1. Preparation of the positive electrode layer

[0224] Provides positive electrode active material particles LiNi 0.8 Co 0.1 Mn 0.1 O2 has a volume distribution particle size Dv50 of 3 μm; the second solid electrolyte particle, Li6PS5Cl, has a volume distribution particle size Dv50 of 10 μm and an ionic conductivity of 12 mS / cm at 25 °C.

[0225] Preparation of the positive electrode active material layer: The above-mentioned positive electrode active material particles, the above-mentioned second solid electrolyte particles, and conductive agent carbon black particles were uniformly mixed for 20 min to obtain a composite positive electrode powder. Then, polyvinylidene fluoride (PVDF) binder was added, and the mixture was rolled into a positive electrode film. In the positive electrode active material layer, the mass fractions of the positive electrode active material particles, the second solid electrolyte particles, the conductive agent, and the binder were 80%, 16%, 2%, and 2%, respectively.

[0226] Preparation of the positive electrode layer: The above-mentioned positive electrode active material layers are stacked sequentially between the positive electrode current collector aluminum foil and the electrolyte layer.

[0227] 2. Preparation of the negative electrode layer

[0228] The negative electrode layer is a lithium-indium alloy, in which the molar ratio of Li to In is 1:3.

[0229] 3. Preparation of the electrolyte layer

[0230] It is made by pressing the sulfide electrolyte Li6PS5Cl into sheets.

[0231] 4. Preparation of solid-state battery cells

[0232] In the molded battery system, solid-state battery cells are pressed into layers of positive electrode, electrolyte, and negative electrode in the order from top to bottom under a pressure of 10 MPa and then encapsulated in a molded battery fixture with an external pressure of 50 MPa.

[0233] Comparative Example 3

[0234] 1. Preparation of the positive electrode layer

[0235] Provides positive electrode active material particles LiNi 0.8 Co 0.1 Mn 0.1 O2, with a volume distribution particle size Dv50 of 3 μm; the first solid electrolyte particle Li6PS5Cl, with a volume distribution particle size Dv50 of 0.9 μm and an ionic conductivity of 5 mS / cm at 25℃; the second solid electrolyte particle Li6PS5Cl, with a volume distribution particle size Dv50 of 10 μm and an ionic conductivity of 12 mS / cm at 25℃.

[0236] Preparation of the positive electrode active material layer: The above-mentioned positive electrode active material particles were uniformly mixed with the above-mentioned two types of sulfide solid electrolyte particles of different particle sizes (i.e., the first solid electrolyte particles and the second solid electrolyte particles) and conductive carbon black particles for 20 min to obtain a composite positive electrode powder. Then, polyvinylidene fluoride (PVDF) binder was added, and the mixture was rolled into a positive electrode film. In the positive electrode active material layer, the mass fractions of the positive electrode active material particles, sulfide solid electrolyte particles, conductive agent, and binder were 80%, 16%, 2%, and 2%, respectively; the mass ratio of the first solid electrolyte particles to the second solid electrolyte particles was 80:20.

[0237] Preparation of the positive electrode layer: The above-mentioned positive electrode active material layers are stacked sequentially between the positive electrode current collector aluminum foil and the electrolyte layer.

[0238] 2. Preparation of the negative electrode layer

[0239] The negative electrode layer is a lithium-indium alloy, in which the molar ratio of Li to In is 1:3.

[0240] 3. Preparation of the electrolyte layer

[0241] It is made by pressing the sulfide electrolyte Li6PS5Cl into sheets.

[0242] 4. Preparation of solid-state battery cells

[0243] In the molded battery system, solid-state battery cells are pressed into layers of positive electrode, electrolyte, and negative electrode in the order from top to bottom under a pressure of 10 MPa and then encapsulated in a molded battery fixture with an external pressure of 50 MPa.

[0244] Comparative Example 4

[0245] 1. Preparation of the positive electrode layer

[0246] Provides positive electrode active material particles LiNi 0.8 Co 0.1 Mn 0.1 O2 has a volume distribution particle size Dv50 of 3 μm; the first solid electrolyte particle, Li6PS5Cl, has a volume distribution particle size Dv50 of 0.9 μm and an ionic conductivity of 5 mS / cm at 25 °C.

[0247] Preparation of the first positive electrode active material layer: The above-mentioned positive electrode active material particles, the above-mentioned first solid electrolyte particles, and conductive agent carbon black particles were uniformly mixed for 20 minutes to obtain a composite positive electrode powder. Then, polyvinylidene fluoride (PVDF) binder was added, and the mixture was rolled into a positive electrode film. In the first positive electrode active material layer, the mass fractions of the positive electrode active material particles, the first solid electrolyte particles, the conductive agent, and the binder were 70%, 26%, 2%, and 2%, respectively.

[0248] Preparation of the second positive electrode active material layer: The above-mentioned positive electrode active material particles, the above-mentioned first solid electrolyte particles, and conductive agent carbon black particles are uniformly mixed for 20 minutes to obtain a composite positive electrode powder. Then, polyvinylidene fluoride (PVDF) binder is added, and the mixture is rolled into a positive electrode film. In the second positive electrode active material layer, the mass fractions of the positive electrode active material particles, the first solid electrolyte particles, the conductive agent, and the binder are 90%, 6%, 2%, and 2%, respectively.

[0249] Preparation of the positive electrode layer: The two positive electrode active material layers are stacked sequentially between the positive electrode current collector aluminum foil and the electrolyte layer, wherein the first positive electrode active material layer is close to the positive electrode current collector aluminum foil and the second positive electrode active material layer is far away from the positive electrode current collector aluminum foil.

[0250] 2. Preparation of the negative electrode layer

[0251] The negative electrode layer is a lithium-indium alloy, in which the molar ratio of Li to In is 1:3.

[0252] 3. Preparation of the electrolyte layer

[0253] It is made by pressing the sulfide electrolyte Li6PS5Cl into sheets.

[0254] 4. Preparation of solid-state battery cells

[0255] In the molded battery system, solid-state battery cells are pressed into layers of positive electrode, electrolyte, and negative electrode in the order from top to bottom under a pressure of 10 MPa and then encapsulated in a molded battery fixture with an external pressure of 50 MPa.

[0256] Comparative Example 5

[0257] 1. Preparation of the positive electrode layer

[0258] Provides positive electrode active material particles LiNi 0.8 Co 0.1 Mn 0.1 O2 has a volume distribution particle size Dv50 of 3 μm; the second solid electrolyte particle, Li6PS5Cl, has a volume distribution particle size Dv50 of 10 μm and an ionic conductivity of 12 mS / cm at 25 °C.

[0259] Preparation of the first positive electrode active material layer: The above-mentioned positive electrode active material particles, the above-mentioned second solid electrolyte particles, and conductive agent carbon black particles are uniformly mixed for 20 minutes to obtain a composite positive electrode powder. Then, polyvinylidene fluoride (PVDF) binder is added, and the mixture is rolled into a positive electrode film. In the first positive electrode active material layer, the mass fractions of the positive electrode active material particles, the second solid electrolyte particles, the conductive agent, and the binder are 70%, 26%, 2%, and 2%, respectively.

[0260] Preparation of the second positive electrode active material layer: The above-mentioned positive electrode active material particles, the above-mentioned second solid electrolyte particles, and conductive agent carbon black particles were uniformly mixed for 20 minutes to obtain a composite positive electrode powder. Then, polyvinylidene fluoride (PVDF) binder was added, and the mixture was rolled into a positive electrode film. In the second positive electrode active material layer, the mass fractions of the positive electrode active material particles, the second solid electrolyte particles, the conductive agent, and the binder were 90%, 6%, 2%, and 2%, respectively.

[0261] Preparation of the positive electrode layer: The two positive electrode active material layers are stacked sequentially between the positive electrode current collector aluminum foil and the electrolyte layer, wherein the first positive electrode active material layer is close to the positive electrode current collector aluminum foil and the second positive electrode active material layer is far away from the positive electrode current collector aluminum foil.

[0262] 2. Preparation of the negative electrode layer

[0263] The negative electrode layer is a lithium-indium alloy, in which the molar ratio of Li to In is 1:3.

[0264] 3. Preparation of the electrolyte layer

[0265] It is made by pressing the sulfide electrolyte Li6PS5Cl into sheets.

[0266] 4. Preparation of solid-state battery cells

[0267] In the molded battery system, solid-state battery cells are pressed into layers of positive electrode, electrolyte, and negative electrode in the order from top to bottom under a pressure of 10 MPa and then encapsulated in a molded battery fixture with an external pressure of 50 MPa.

[0268] Comparative Example 6

[0269] Solid-state battery cells were prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass ratio of the first solid electrolyte particles to the second solid electrolyte particles in the second positive electrode active material layer was 75:25. Specific parameters are shown in Table 1.

[0270] Table 1

[0271] The meanings of each parameter in Table 1 are as follows:

[0272] M1 represents the mass fraction of positive electrode active material particles in the first positive electrode active material layer;

[0273] L1 represents the total mass fraction of sulfide solid electrolyte particles in the first positive electrode active material layer;

[0274] L 11: L 12 This indicates the mass ratio of the first solid electrolyte particles to the second solid electrolyte particles in the first positive electrode active material layer;

[0275] M2 represents the mass fraction of positive electrode active material particles in the second positive electrode active material layer;

[0276] L2 represents the total mass fraction of sulfide solid electrolyte particles in the second positive electrode active material layer;

[0277] L 21: L 22 This indicates the mass ratio of the first solid electrolyte particles to the second solid electrolyte particles in the second positive electrode active material layer;

[0278] H represents the total thickness of the composite positive electrode active material layer.

[0279] Performance testing

[0280] Charge and discharge tests were conducted on the Blue Battery test platform at a temperature of 25°C and a charge and discharge voltage range of 2.6V to 4.3V vs. Li+ / Li.

[0281] Capacity and rate testing procedure: Solid-state battery cells are charged and discharged in the order of 0.1C charge / discharge - 0.3C charge / discharge - 0.5C charge / discharge - 1C charge / discharge, with one cycle at each rate. The discharge specific capacity at 0.1C, 0.3C, 0.5C and 1C rates are obtained respectively. The rate performance of the solid-state battery cell is characterized by the ratio of the discharge specific capacity at 1C rate to the discharge specific capacity at 0.3C rate.

[0282] Cyclic testing procedure: After charging and discharging a single solid-state battery cell at 0.1C for one cycle, the discharge specific capacity C1 at 0.1C rate is obtained; then, it is charged and discharged at 0.3C for 200 cycles, and the discharge specific capacity C2 at 0.3C rate for 200 cycles is obtained. The capacity retention rate of a single solid-state battery cell after 200 cycles = C2 / C1 × 100%.

[0283] The performance test results are shown in Table 2.

[0284] Table 2

[0285] As can be seen from the data in Tables 1 and 2, the embodiments of this disclosure design a composite positive electrode active material layer with multiple gradient distributions. The mass fraction of positive electrode active material particles in the first positive electrode active material layer is less than that in the second positive electrode active material layer, and the mass fraction of solid electrolyte particles is greater than that in the second positive electrode active material layer. The solid electrolyte particles include a gradation of first and second solid electrolyte particles with different particle sizes. Furthermore, the mass proportion of the first solid electrolyte particles in the first positive electrode active material layer is less than that in the second positive electrode active material layer, thereby improving the cycle performance and rate performance of the battery cell.

[0286] Among them, Comparative Examples 1-3 are single-layer positive electrode active material layers, with no gradient distribution between the positive electrode active material particles and solid electrolyte particles. Their cycle performance, rate performance, and discharge capacity performance are all inferior to Examples 1-5. Comparative Examples 4-5 are composite positive electrode active material layers, but only one type of solid electrolyte particle is present. There is no gradient distribution of solid electrolyte particles in the composite positive electrode active material layer, and their cycle performance and rate performance are inferior to Examples 1-5. In Comparative Example 6, the mass ratio of the first solid electrolyte particles in the first positive electrode active material layer is greater than that in the second positive electrode active material layer, and its cycle performance and rate performance are inferior to Examples 1-5.

[0287] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present disclosure, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present disclosure.

Claims

1. A battery cell, wherein, The device includes an electrolyte layer and a positive electrode layer. The positive electrode layer includes a positive electrode current collector and a composite positive electrode active material layer located on at least one side of the positive electrode current collector. The composite positive electrode active material layer includes a first positive electrode active material layer close to the positive electrode current collector and a second positive electrode active material layer away from the positive electrode current collector. Both the first and second positive electrode active material layers include positive electrode active material particles and solid electrolyte particles. The solid electrolyte particles include first solid electrolyte particles and second solid electrolyte particles. The volume distribution particle size Dv50 of the first solid electrolyte particles is smaller than that of the second solid electrolyte particles. The volume distribution particle size Dv50 of the first solid electrolyte particles is < 1 μm. The mass fraction of the positive electrode active material particles in the first positive electrode active material layer is less than the mass fraction of the positive electrode active material particles in the second positive electrode active material layer; the mass fraction of the solid electrolyte particles in the first positive electrode active material layer is greater than the mass fraction of the solid electrolyte particles in the second positive electrode active material layer. In the first positive electrode active material layer, the mass percentage of the first solid electrolyte particles in the solid electrolyte particles is a%; in the second positive electrode active material layer, the mass percentage of the first solid electrolyte particles in the solid electrolyte particles is b%; where a < b.

2. The battery cell according to claim 1, wherein, The volume distribution particle size Dv50 of the second solid electrolyte particles is 3μm to 20μm.

3. The battery cell according to claim 1 or 2, wherein, The mass percentage of the first solid electrolyte particle in the solid electrolyte particles must satisfy at least one of the following conditions: (1)50≤a≤90； (2)75≤b≤97。 4. The battery cell according to any one of claims 1 to 3, wherein, The first positive electrode active material layer must satisfy at least one of the following conditions: (1) The mass fraction of the positive electrode active material particles in the first positive electrode active material layer is 40% to 80%; (2) The mass fraction of the solid electrolyte particles in the first positive electrode active material layer is 17% to 59%; (3) The mass fraction of the first solid electrolyte particles in the first positive electrode active material layer is 12% to 47%; (4) The mass fraction of the second solid electrolyte particles in the first positive electrode active material layer is 2% to 25%.

5. The battery cell according to claim 4, wherein, The first positive electrode active material layer satisfies one of the following conditions: (1) The mass fraction of the positive electrode active material particles in the first positive electrode active material layer is greater than or equal to 40% and less than 60%, and 50≤a≤80; (2) The mass fraction of the positive electrode active material particles in the first positive electrode active material layer is 60% to 70%, and 65 ≤ a ≤ 85; (3) The mass fraction of the positive electrode active material particles in the first positive electrode active material layer is greater than 70% and less than or equal to 80%, and 70≤a≤90.

6. The battery cell according to any one of claims 1 to 5, wherein, The second positive electrode active material layer must satisfy at least one of the following conditions: (1) The mass fraction of the positive electrode active material particles in the second positive electrode active material layer is 80% to 97%; (2) The mass fraction of the solid electrolyte particles in the second positive electrode active material layer is 2% to 19%; (3) The mass fraction of the first solid electrolyte particles in the second positive electrode active material layer is 1.5% to 18.4%; (4) The mass fraction of the second solid electrolyte particles in the second positive electrode active material layer is 0.1% to 4.3%.

7. The battery cell according to any one of claims 1 to 4, wherein, The mass fraction of the positive electrode active material particles in the first positive electrode active material layer is 60% to 70%; the mass fraction of the positive electrode active material particles in the second positive electrode active material layer is 85% to 95%.

8. The battery cell according to any one of claims 1 to 7, wherein, The first solid electrolyte particle and the second solid electrolyte particle satisfy at least one of the following conditions: (1) The ionic conductivity of the first solid electrolyte particle at 25°C is 1 mS / cm to 5 mS / cm; (2) The ionic conductivity of the second solid electrolyte particles at 25°C is 5 mS / cm to 50 mS / cm; (3) The ionic conductivity of the first solid electrolyte particle at 25°C is less than that of the second solid electrolyte particle at 25°C.

9. The battery cell according to any one of claims 1 to 8, wherein, The thickness of the composite positive electrode active material layer is 50 μm to 200 μm.

10. The battery cell according to any one of claims 1 to 9, wherein, The solid electrolyte particles include one or more of sulfide electrolytes and halide electrolytes.

11. The battery cell according to any one of claims 1 to 10, wherein, The volume distribution particle size Dv50 of the positive electrode active material particles is 2μm to 10μm.

12. The battery cell according to any one of claims 1 to 11, wherein, The positive electrode active material particles include one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds.

13. The battery cell according to any one of claims 1 to 12, wherein, The first positive electrode active material layer and the second positive electrode active material layer each independently also include a conductive agent and a binder; The mass fraction of the conductive agent in the first positive electrode active material layer or the second positive electrode active material layer is independently 1% to 3%; The mass fraction of the binder in the first positive electrode active material layer or the second positive electrode active material layer is independently 1% to 2%.

14. A battery device, wherein, It includes multiple battery cells as described in any one of claims 1 to 13.

15. An electrical appliance, wherein, Includes a battery cell according to any one of claims 1 to 13 or a battery device according to claim 14.

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