Solid-state battery cell and preparation method therefor, battery device, and electric device

Abstract

Provided are a solid-state battery cell and a preparation method therefor, a battery device, and an electric device. The solid-state battery cell comprises a negative electrode layer, an electrolyte layer, and a positive electrode layer; the electrolyte layer is located between the negative electrode layer and the positive electrode layer; the negative electrode layer comprises a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector; the negative electrode active material layer comprises a silicon-carbon composite material; the silicon-carbon composite material comprises porous carbon and a silicon-based material located in pores of the porous carbon; a region extending from the outer surface of porous carbon particles towards the inside of the particles by an extension distance of 0.5 times the length between any point on the outer surface of the particles and a particle core is denoted as an outer region of the porous carbon, and a region on the inner side of the outer region of the porous carbon is denoted as an inner region of the porous carbon; the total pore area of the inner region of the porous carbon is 0-10% of the total pore area of the outer region of the porous carbon; and a NP ratio of the solid-state battery cell is greater than 0 and less than 1, wherein the NP ratio is the ratio of the capacity per unit area of a negative electrode to the capacity per unit area of a positive electrode. The solid-state battery cell has high energy density, and has high initial coulombic efficiency, good cycle stability, and good kinetic performance at a low external pressure.

Description

Solid-state battery cells and their preparation methods, battery devices and power devices

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese patent application 202411912545.X, filed on December 24, 2024, entitled "Solid-state battery cell and method for preparation thereof, battery device and power supply device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a solid-state battery cell and its preparation method, battery device, and power consumption device. Background Technology

[0004] Compared to battery cells using liquid electrolytes, solid-state battery cells use solid electrolyte materials, making them less prone to combustion and explosion, and offering high reliability and high energy density. Solid-state battery cells using silicon-based materials for the negative electrode can achieve even higher energy density; however, silicon-based materials continuously expand and contract during cycling, which can easily lead to contact failure and cause rapid capacity decay in solid-state battery cells. Summary of the Invention

[0005] This disclosure provides a solid-state battery cell and its preparation method, battery device and power supply device. The solid-state battery cell has high energy density, high initial coulombic efficiency under low external pressure, good cycle stability and good kinetic performance.

[0006] In a first aspect, this disclosure provides a solid-state battery cell, comprising a negative electrode layer, an electrolyte layer, and a positive electrode layer, wherein the electrolyte layer is located between the negative electrode layer and the positive electrode layer, the negative electrode layer comprises a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, the negative electrode active material layer comprises a silicon-carbon composite material, the silicon-carbon composite material comprises porous carbon and silicon-based material located in the pores of the porous carbon, the region formed by extending from the outer surface of the porous carbon particles toward the interior of the particles at a distance of 0.5 times the length between any point on the outer surface of the particles and the core of the particles is denoted as the outer region of the porous carbon, the region inside the outer region of the porous carbon is denoted as the inner region of the porous carbon, and the total pore area of ​​the inner region of the porous carbon is 0%-10% of the total pore area of ​​the outer region of the porous carbon; the NP ratio of the solid-state battery cell is greater than 0 and less than 1, the NP ratio being the ratio of the negative electrode unit area capacity to the positive electrode unit area capacity.

[0007] The negative electrode sheet disclosed herein uses a porous carbon silicon-carbon composite material whose total pore area in the internal region is 0%-10% of the total pore area in the external region. This means the pores of the porous carbon are mainly concentrated in the external region of the particles, and consequently, the Si element in the silicon-carbon composite material is mainly concentrated on the particle surface. This configuration allows lithium to undergo an alloying lithium-intercalation reaction on the surface of the silicon-carbon composite material particles. This reduces the volume expansion of the silicon-carbon composite material and irreversible lithium loss, thereby improving the initial coulombic efficiency and capacity retention of the solid-state battery cell. Furthermore, by ensuring that the total pore area in the internal region of the porous carbon silicon-carbon composite material is 0%-10% of the total pore area in the external region, and by maintaining an NP ratio greater than 0 and less than 1 in the solid-state battery cell, when the solid-state battery cell operates under low external pressure, in addition to some lithium undergoing an alloying lithium-intercalation reaction with the silicon-carbon composite material, excess lithium will accumulate between the silicon-carbon composite material particles and deposit through the negative electrode active material layer onto the surface of the negative electrode current collector, i.e., deposited between the negative electrode active material layer and the negative electrode current collector. The lithium aggregates between the silicon-carbon composite particles can serve as lithium-ion transport channels, improving the lithium-ion transport performance and kinetic performance of the negative electrode. Lithium deposits between the negative electrode active material layer and the negative electrode current collector, which can also cause the negative electrode to change from an alloying lithium intercalation reaction mechanism to a lithium metal deposition / stripping mechanism during subsequent cycle charging and discharging of the solid-state battery cell. At the same time, the negative electrode active material layer can act as a barrier layer, reducing the risk of short circuit between lithium metal and the positive electrode, thereby improving the cycle stability and kinetic performance of the solid-state battery cell.

[0008] Therefore, the solid-state battery cell disclosed herein has high energy density, high initial coulombic efficiency, good cycle stability and good kinetic performance under low external pressure.

[0009] In some embodiments, the total pore area of ​​the internal region of the porous carbon is 0%-2% of the total pore area of ​​the external region of the porous carbon.

[0010] In some embodiments, the total pore area of ​​the outer region of the porous carbon is 1 × 10⁻⁶. 4 cm 2 / g to 30×10 4 cm 2 / g, can be selected as 1×10 4 cm 2 / g to 10×10 4 cm 2 / g. The large total pore area of ​​the outer region of porous carbon allows lithium to undergo an alloying lithium intercalation reaction on the surface of the silicon-carbon composite material. This can better reduce the volume expansion and irreversible lithium loss of the silicon-carbon composite material, thereby improving the cycle stability of solid-state battery cells.

[0011] In some embodiments, the total pore area of ​​the internal regions of the porous carbon is 0 to 3 × 10⁻⁶. 4 cm 2 / g, which can be set to 0. The internal regions of porous carbon are poreless or have a small total pore area, which allows lithium to undergo an alloying lithium intercalation reaction on the surface of the silicon-carbon composite material. This can better reduce the volume expansion and irreversible lithium loss of the silicon-carbon composite material, thereby improving the cycle stability of solid-state battery cells.

[0012] In some embodiments, with the total mass of the negative electrode active material layer being 100%, the mass fraction of Si element in the negative electrode active material layer is greater than or equal to 5% and less than 90%.

[0013] In some embodiments, the mass fraction of Si in the negative electrode active material layer is 5% to 50%, and the NP ratio of the solid-state battery cell is 0.01-0.5. When the NP ratio and the mass fraction of Si in the negative electrode active material layer are within the above ranges, the thickness uniformity of the negative electrode active material layer is good, and lithium is more easily aggregated between silicon-based material particles, thus serving as a better lithium-ion transport channel. Furthermore, lithium can easily penetrate the negative electrode active material layer and deposit between the negative electrode active material layer and the negative electrode current collector, which is more conducive to the stable cycling of the solid-state battery cell under low external pressure. In addition, the solid-state battery cell also has high initial coulombic efficiency and high cycle capacity retention.

[0014] In some embodiments, the mass fraction of Si in the negative electrode active material layer is 20% to 50%, and the NP ratio of the solid-state battery cell is 0.5-0.9. When the NP ratio and the mass fraction of Si in the negative electrode active material layer of the solid-state battery cell are within the above ranges, the negative electrode can exhibit good kinetic performance. Simultaneously, lithium is more easily aggregated between silicon-based material particles, thus serving as a better lithium-ion transport channel. Furthermore, lithium can easily penetrate the negative electrode active material layer and deposit between the negative electrode active material layer and the negative electrode current collector, which is more conducive to the stable cycling of the solid-state battery cell under low external pressure. In addition, the solid-state battery cell also exhibits high initial coulombic efficiency and high cycle capacity retention.

[0015] In some embodiments, the solid-state battery cell operates under an external pressure below 10 MPa. That is, the solid-state battery cell of this disclosure exhibits high initial coulombic efficiency, good cycle stability, and good kinetic performance under an external pressure below 10 MPa.

[0016] In some embodiments, the porosity of the negative electrode active material layer is 10%-20%. A porosity within this range facilitates lithium penetration through the negative electrode active material layer and deposition between the negative electrode active material layer and the negative electrode current collector, thereby reducing the risk of short circuits between the positive and negative electrodes of the solid-state battery cell and improving the cycle stability of the solid-state battery cell.

[0017] In some embodiments, the thickness of the negative electrode active material layer is 2μm-35μm, and can be selected as 11μm-35μm.

[0018] In some embodiments, the silicon-based material includes one or more of silicon, silicon carbon, silicon oxide, silicon nitride, and silicon alloy materials.

[0019] In some embodiments, the silicon-carbon composite material further includes a coating layer located on at least a portion of the surface of the porous carbon, and the coating layer includes one or more of carbon materials, metals, and conductive polymers.

[0020] In some embodiments, the volume distribution particle size Dv50 of the silicon-carbon composite material is 500 nm-20 μm, and can be selected as 2 μm-5 μm.

[0021] In some embodiments, the negative electrode active material layer further includes metal particles located between the silicon-based material particles, the metal particles being capable of forming an alloy or solid solution with lithium. The ability of the metal particles to alloy or form a solid solution with lithium facilitates lithium transfer between the silicon-based material particles, promotes lithium penetration through the negative electrode active material layer, and facilitates lithium deposition between the negative electrode active material layer and the negative electrode current collector.

[0022] In some embodiments, the metal particles include one or more of Ag, Mg, Au, Cu, and Ti.

[0023] In some embodiments, the mass of the metal particles is 1%-10% of the mass of the silicon-based material. A mass fraction of metal particles within this range is beneficial for promoting lithium transfer between silicon-based material particles, facilitating lithium penetration through the negative electrode active material layer and deposition between the negative electrode active material layer and the negative electrode current collector, and also enabling the solid-state battery cell to have better cycle performance.

[0024] In some embodiments, the volume distribution particle size Dv50 of the metal particles is 20nm-100nm.

[0025] In some embodiments, the negative electrode active material layer further includes a negative electrode conductive agent, which includes one or more of linear conductive agents, planar conductive agents, and spherical conductive agents.

[0026] In some embodiments, the negative electrode active material layer further includes a solid electrolyte material, which includes one or more of sulfide solid electrolyte materials, halide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials.

[0027] In some embodiments, the negative electrode active material layer further includes a negative electrode binder.

[0028] In some embodiments, the negative electrode layer further includes a lithium-based metal layer located between the negative electrode current collector and the negative electrode active material layer. The lithium-based metal layer can compensate for irreversible lithium loss from the negative electrode active material layer, thereby improving the cycle stability of the solid-state battery cell.

[0029] In some embodiments, the lithium-based metal layer comprises lithium or a lithium alloy.

[0030] In some embodiments, the thickness of the lithium-based metal layer is 0.5 μm-50 μm.

[0031] In some embodiments, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector. The positive electrode active material layer includes a solid electrolyte material and a positive electrode active material. The positive electrode active material includes one or more of lithium transition metal oxides and their modified materials, lithium phosphates and their modified materials, lithium titanate, lithium niobate, sulfur, selenium, and tellurium. The solid electrolyte material includes one or more of sulfide solid electrolyte materials, halide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials.

[0032] In some embodiments, the electrolyte layer comprises one or more of sulfide solid electrolyte materials, halide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials.

[0033] Secondly, this disclosure provides a method for preparing a solid-state battery cell, comprising the following steps: providing a negative electrode layer, an electrolyte layer, and a positive electrode layer; assembling the negative electrode layer, the electrolyte layer, and the positive electrode layer; and pressing them to obtain a solid-state battery cell. The electrolyte layer is located between the negative electrode layer and the positive electrode layer. The negative electrode layer includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon-based material located in the pores of the porous carbon. The region formed by extending from the outer surface of the porous carbon particles to the interior of the particles at a distance 0.5 times the length between any point on the outer surface of the particles and the core of the particles is denoted as the outer region of the porous carbon. The region inside the outer region of the porous carbon is denoted as the inner region of the porous carbon. The total pore area of ​​the inner region of the porous carbon is 0%-10% of the total pore area of ​​the outer region of the porous carbon. The NP ratio of the solid-state battery cell is greater than 0 and less than 1, where the NP ratio is the ratio of the negative electrode unit area capacity to the positive electrode unit area capacity.

[0034] Thirdly, this disclosure provides a battery device comprising a plurality of solid-state battery cells as described in the first aspect.

[0035] Fourthly, this disclosure provides an electrical device that includes a solid-state battery cell (as described in the first aspect) or a battery device (as described in the third aspect). Attached Figure Description

[0036] 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 described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0037] Figure 1 shows a schematic diagram of a solid-state battery cell provided in some embodiments of this disclosure.

[0038] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure.

[0039] Figure 3 shows a schematic diagram of the structure of porous carbon provided in some embodiments of this disclosure.

[0040] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0041] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the solid-state battery cell, its preparation method, battery device, 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.

[0042] 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.

[0043] Unless otherwise specified, all embodiments and optional embodiments of this disclosure may be combined with each other to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0044] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0045] Unless otherwise specified, all steps in this disclosure may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates 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.

[0046] 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.

[0047] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0048] 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.

[0049] In this disclosure, Dv50 represents the particle size corresponding to a cumulative volume distribution percentage of 50%, which can be measured using a laser particle size analyzer according to GB / T 19077-2016. During testing, 1g of the sample to be tested is added to a clean small beaker, followed by 20ml of deionized water. The mixture is sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer is then turned on, and after cleaning the optical path system, the background is automatically measured. The sonicated solution is stirred to ensure uniform dispersion, then placed into the sample cell as required, and particle size measurement begins. The testing instrument can be a MasterSizer 3000 laser particle size analyzer.

[0050] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0051] The solid-state battery cells mentioned in the embodiments of this disclosure can independently perform charging and discharging functions. Solid-state battery cells can be cylindrical, cuboid, or other shapes, and the embodiments of this disclosure are not limited in this respect. Figure 1 shows a cuboid solid-state battery cell 5 as an example.

[0052] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple solid-state battery cells, which are connected in series, parallel, or mixed connections via busbars.

[0053] In some embodiments, a battery cell assembly is typically formed by arranging multiple solid-state battery cells.

[0054] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple solid-state battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple solid-state battery cells together with cable ties.

[0055] 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.

[0056] 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.

[0057] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple solid-state battery cells to the housing.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] The technical solutions described in this disclosure are applicable to various electrical devices that use solid-state 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. Solid-state battery cells and battery devices are used to store or provide electrical energy.

[0062] 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.

[0063] The solid-state battery cells disclosed herein may include coin cells, molded cells, hard-case cells, pouch cells, etc.

[0064] Silicon-based materials can provide high capacity, which is beneficial for achieving high energy density in solid-state battery cells. However, silicon-based materials continuously expand and contract during cycling, and this expansion and contraction can easily lead to interfacial contact failure. Therefore, solid-state battery cells using silicon-based materials as the negative electrode usually require significant external pressure during charge-discharge cycles to maintain effective interfacial contact between materials. However, high cycle pressure increases the overall weight of the battery device and sacrifices energy density; while low cycle pressure, such as external pressure below 10 MPa, usually leads to insufficient interfacial contact and rapid capacity decay, thus limiting the practical application of solid-state battery cells.

[0065] In view of this, embodiments of the present disclosure provide a solid-state battery cell that has high energy density, good cycle stability and good kinetic performance under low external pressure.

[0066] The solid-state battery cell provided in this embodiment includes a negative electrode layer, an electrolyte layer, and a positive electrode layer, with the electrolyte layer located between the negative electrode layer and the positive electrode layer.

[0067] The negative electrode layer includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon-based material located in the pores of the porous carbon. The region defined by the outer surface of the porous carbon particles extending into the particle from a distance of 0.5 times the length between any point on the outer surface of the particles and the particle core is denoted as the outer region of the porous carbon. The region inside the outer region of the porous carbon is denoted as the inner region of the porous carbon. The total pore area of ​​the inner region of the porous carbon is 0%-10% of the total pore area of ​​the outer region of the porous carbon.

[0068] In solid-state battery cells, the NP ratio is greater than 0 and less than 1. The NP ratio (Negative / Positive Ratio) is the ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area, i.e., negative electrode capacity per unit area / positive electrode capacity per unit area. The negative electrode capacity per unit area refers to the capacity per unit area of ​​the negative electrode active material layer.

[0069] The NP ratio can be tested using the following method.

[0070] The negative electrode layer was removed from a solid-state battery cell and placed in a solid-state battery mold for testing. The counter electrode was a lithium-indium alloy sheet separated by an electrolyte layer. The battery was discharged to 0.01V (vs. Li) at a current density of 0.1C. + / Li), and then charged to 2V at a current density of 0.1C (vs. Li). + The resulting charging capacity ( / Li) is the negative electrode capacity. Negative electrode capacity per unit area = negative electrode capacity / negative electrode layer area.

[0071] The positive electrode layer is removed from a solid-state battery cell and placed in a solid-state battery mold for testing. A lithium-indium alloy sheet is used as the counter electrode, separated by an electrolyte layer. The battery is charged at a current density of 0.1C to the upper cutoff voltage, and then discharged at a current density of 0.1C to the lower cutoff voltage. The resulting discharge capacity is the positive electrode capacity. Positive electrode capacity per unit area = Positive electrode capacity / Positive electrode layer area.

[0072] NP ratio = negative electrode unit area capacity / positive electrode unit area capacity.

[0073] Both the upper and lower cutoff voltages are known in the art, and the voltages recommended in the product specifications can be used. For example, the positive electrode active material is a lithium transition metal oxide or its modified form, such as LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.96 Co 0.02 Mn 0.02O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 O2, the upper limit cutoff voltage can be 4.3V (vs. Li). + / Li), the lower cutoff voltage can be 2V (vs.Li). + / Li).

[0074] Currently, solid-state battery cells using silicon anodes are designed with an NP ratio greater than or equal to 1, and these cells are typically charged and discharged under high external pressure to minimize the risk of lithium ion deposition and dendrite formation on the anode surface due to insufficient anode capacity. However, when these solid-state battery cells operate under low external pressure, such as below 10 MPa, the capacity rapidly decreases due to insufficient contact at the silicon-based anode interface. Simultaneously, lithium ions are more likely to deposit and form lithium dendrites on the anode surface, increasing the risk of short circuits between the positive and negative electrodes.

[0075] During solid-state battery cell operation, lithium undergoes an alloying lithium-intercalation reaction with the silicon-carbon composite material. During discharge, some lithium is difficult to extract from the silicon-carbon composite material. Simultaneously, the volume expansion of the silicon-carbon composite material during cycling also causes irreversible lithium loss. The negative electrode sheet of this disclosure uses porous carbon in a silicon-carbon composite material where the total pore area of ​​the internal region is 0%-10% of the total pore area of ​​the external region. This means the pores of the porous carbon are mainly concentrated in the external region of the particles, and consequently, the Si element in the silicon-carbon composite material is mainly concentrated on the particle surface. This configuration allows lithium to undergo an alloying lithium-intercalation reaction on the surface of the silicon-carbon composite material particles, thereby reducing both the volume expansion of the silicon-carbon composite material and irreversible lithium loss, and improving the initial coulombic efficiency and capacity retention of the solid-state battery cell. Furthermore, by ensuring that the total pore area of ​​the porous carbon in the silicon-carbon composite material is 0%-10% of the total pore area in the external region, and by ensuring that the NP ratio of the solid-state battery cell is greater than 0 and less than 1, when the solid-state battery cell operates under low external pressure, in addition to some lithium undergoing alloying and lithium intercalation reactions with the silicon-carbon composite material, excess lithium will accumulate between the silicon-carbon composite material particles and deposit across the negative electrode active material layer on the surface of the negative electrode current collector, i.e., deposited between the negative electrode active material layer and the negative electrode current collector. This lithium accumulated between the silicon-carbon composite material particles can serve as lithium-ion transport channels, improving the lithium-ion transport performance and kinetic performance of the negative electrode. The lithium deposited across the negative electrode active material layer between the negative electrode active material layer and the negative electrode current collector can also promote a shift from the alloying and lithium intercalation reaction mechanism to a lithium metal deposition / stripping mechanism during subsequent charge-discharge cycles of the solid-state battery cell. Simultaneously, the negative electrode active material layer can act as a barrier layer, reducing the risk of short circuits between lithium metal and the positive electrode, thereby improving the cycle stability and kinetic performance of the solid-state battery cell.

[0076] Therefore, the solid-state battery cell disclosed herein has high energy density, high initial coulombic efficiency, good cycle stability and good kinetic performance under low external pressure.

[0077] The solid-state battery cell disclosed herein can operate under external pressures below 10 MPa. That is, the solid-state battery cell disclosed herein exhibits high initial coulombic efficiency, good cycle stability, and good kinetic performance under external pressures below 10 MPa.

[0078] Optionally, the solid-state battery cell of this disclosure can operate under an external pressure below 5 MPa. That is, the solid-state battery cell of this disclosure exhibits high initial coulombic efficiency, good cycle stability, and good kinetic performance under an external pressure below 5 MPa.

[0079] The total pore area of ​​the internal region of porous carbon is 0%-10% of the total pore area of ​​the external region of porous carbon. For example, it can be 0, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of the above values. 0% indicates that the internal region of porous carbon is non-porous.

[0080] Optionally, the total pore area of ​​the internal region of the porous carbon can be 0%-8%, 0%-7%, 0%-6%, 0%-5%, 0%-4%, 0%-3%, 0%-2%, or 0%-1% of the total pore area of ​​the external region of the porous carbon.

[0081] In some embodiments, the total pore area of ​​the outer region of the porous carbon can be 1 × 10⁻⁶. 4 cm 2 / g to 30×10 4 cm 2 / g, for example, can be 1×10 4 cm 2 / g, 2×10 4 cm 2 / g, 4×10 4 cm 2 / g, 6×10 4 cm 2 / g, 8×10 4 cm 2 / g, 10×10 4 cm 2 / g, 12×10 4 cm 2 / g, 14×10 4cm 2 / g, 16×10 4 cm 2 / g, 16×10 4 cm 2 / g, 20×10 4 cm 2 / g, 22×10 4 cm 2 / g, 24×10 4 cm 2 / g, 26×10 4 cm 2 / g, 28×10 4 cm 2 / g, 30×10 4 cm 2 / g, or any range of the above values.

[0082] The large total pore area of ​​the outer region of porous carbon allows lithium to undergo an alloying lithium intercalation reaction on the surface of silicon-carbon composite materials. This can better reduce the volume expansion and irreversible lithium loss of silicon-carbon composite materials, thereby improving the cycle stability of solid-state battery cells.

[0083] Optionally, the total pore area of ​​the outer region of the porous carbon can be 1×10⁻⁶. 4 cm 2 / g to 30×10 4 cm 2 / g, 1×10 4 cm 2 / g up to 26×10 4 cm 2 / g, 1×10 4 cm 2 / g up to 24×10 4 cm 2 / g, 1×10 4 cm 2 / g to 20×10 4 cm 2 / g, 1×10 4 cm 2 / g up to 18×10 4 cm 2 / g, 1×10 4 cm 2 / g up to 16×10 4 cm 2 / g, 1×10 4 cm 2 / g up to 14×10 4 cm 2 / g, 1×10 4 cm2 / g to 12×10 4 cm 2 / g, 1×10 4 cm 2 / g to 10×10 4 cm 2 / g, 1×10 4 cm 2 / g to 8×10 4 cm 2 / g, 1×10 4 cm 2 / g to 6×10 4 cm 2 / g.

[0084] In some embodiments, the total pore area of ​​the internal regions of porous carbon can be from 0 to 3 × 10⁻⁶. 4 cm 2 / g, for example, can be 0, 1cm 2 / g、2cm 2 / g, 5cm 2 / g, 10cm 2 / g, 50cm 2 / g, 100cm 2 / g、200cm 2 / g、500cm 2 / g, 1000cm 2 / g、2000cm 2 / g、5000cm 2 / g, 1×10 4 cm 2 / g, 2×10 4 cm 2 / g, 3×10 4 cm 2 / g, or any range of the above values.

[0085] The absence of pores or a small total pore area in the internal regions of porous carbon allows lithium to undergo an alloying lithium intercalation reaction on the surface of silicon-carbon composite materials. This can better reduce the volume expansion and irreversible lithium loss of silicon-carbon composite materials, thereby improving the cycle stability of solid-state battery cells.

[0086] Optionally, the total pore area of ​​the internal region of the porous carbon can be from 0 to 2 × 10⁻⁶. 4 cm 2 / g, 0 to 1×10 4 cm 2 / g, 0 to 5000cm 2 / g, 0 to 2000cm 2 / g, 0 to 1000cm 2 / g, 0 to 500cm 2 / g, 0 to 200cm 2 / g, 0 to 100cm 2 / g, 0 to 50cm 2 / g, 0 to 10cm 2 / g.

[0087] Optionally, the total pore area of ​​the internal region of porous carbon is 0, that is, the internal region of porous carbon is poreless.

[0088] The total pore area of ​​the outer region and the total pore area of ​​the inner region of porous carbon, as well as their ratio, can be obtained by testing a cross-sectional image of a silicon-carbon composite material. The cross-sectional image of the silicon-carbon composite material passes through the particle core. Here, "passing through the particle core" means passing through a radius of 0.1 μm extending from the geometric center of the particle towards the particle surface.

[0089] The cross-section of silicon-carbon composite material can be prepared using a cross-section polisher (such as the IB-09010CP argon ion cross-section polisher from JEOL Corporation, Japan). Then, the cross-section of the silicon-carbon composite material is scanned using a scanning electron microscope (SEM), transmission electron microscope (TEM), or high-resolution transmission electron microscope (HRTEM). Finally, image processing software (such as AVIZO) is used to calculate the total pore area of ​​the outer region of the porous carbon in the cross-section image, the total pore area of ​​the inner region of the porous carbon, and the ratio between the two. Because silicon-based materials and porous carbon have different image characteristics, the pore structure of porous carbon can be easily identified from the cross-sectional image of the silicon-carbon composite material.

[0090] The length between any point on the outer surface of a porous carbon particle and the particle core is denoted as L.

[0091] When porous carbon is an ideal sphere, the length L between any point on the outer surface of the porous carbon particle and the particle core is the same, L = R, where R represents the radius. In this case, the outer region of porous carbon refers to the region formed by extending 0.5R from the outer surface of the porous carbon particle to the inside of the particle.

[0092] When porous carbon has a regular or irregular morphology other than an ideal sphere, the length L between different positions on the outer surface of the porous carbon particles and the particle core is different or not exactly the same. The distance 0.5L is a constantly changing value, which is the distance 0.5 times the length between any point on the outer surface of the porous carbon particles and the particle core. The outer region refers to the area enclosed by all points obtained by extending the corresponding distance of 0.5L from all points on the outer surface of the porous carbon particles into the particle core and the outer surface of the particles.

[0093] Figure 3 shows a schematic diagram of a cross-sectional image of porous carbon. As shown in Figure 3, when the porous carbon is an ideal sphere, the distance between any point A in the cross-sectional image and the particle core O is the same; when the porous carbon has a regular or irregular morphology other than an ideal sphere, the distance between any two points B1 and B2 in the cross-sectional image and the particle core O is not the same. In this case, the outer region of the porous carbon has a non-uniform size.

[0094] The NP ratio of a solid-state battery cell is greater than 0 and less than 1, for example, it can be 0.9, 0.86, 0.84, 0.82, 0.8, 0.78, 0.76, 0.74, 0.72, 0.7, 0.68, 0.66, 0.64, 0.62, 0.6, 0.58, 0.56, 0.54, 0.52, 0.5, 0.48, 0.46, 0.44, 0.42, 0.4, 0.38, 0.36, 0.34, 0.32. 0.3, 0.29, 0.28, 0.27, 0.26, 0.25, 0.24, 0.23, 0.22, 0.21, 0.2, 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.11, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, or any range of the above values.

[0095] Optionally, the NP ratio of a solid-state battery cell can be greater than 0 and less than or equal to 0.7, greater than 0 and less than or equal to 0.6, greater than 0 and less than or equal to 0.5, greater than 0 and less than or equal to 0.4, greater than 0 and less than or equal to 0.3, greater than 0 and less than or equal to 0.2, greater than 0 and less than or equal to 0.1, 0.01-0.9, 0.01-0.8, 0.01-0.7, 0.01-0.68, 0.01-0.64, 0.01-0.6, 0.01-0.58, 0.01-0.56, 0.01-0.54, 0.01-0.52, 0.01-0.5, 0.01-0.48, 0.01-0.46, 0.01-0.44, or 0. 01-0.42, 0.01-0.4, 0.01-0.38, 0.01-0.36, 0.01-0.34, 0.01-0.32, 0.01-0.3, 0.1-0.9, 0.1-0.8, 0.1-0.7, 0.1-0.68, 0.1-0.64, 0.1-0.6, 0.1-0.58, 0.1-0.56, 0.1-0.54, 0.1-0.52, 0.1-0.5, 0.1-0.48, 0.1-0.46, 0.1-0.44, 0.1-0.42, 0.1-0.4, 0.1-0.38, 0.1-0.36, 0.1-0.34, 0.1-0. 32, 0.1-0.3, 0.2-0.9, 0.2-0.8, 0.2-0.7, 0.2-0.68, 0.2-0.64, 0.2-0.6, 0.2-0.58, 0.2-0.56, 0.2-0.54, 0.2-0.52, 0.2-0.5, 0.2-0.48, 0.2-0.46, 0.2-0.44, 0.2-0.42, 0.2-0.4, 0.2-0.38, 0.2-0.36, 0.2-0.34, 0.2-0.32, 0.2-0.3, 0.3-0.9, 0.3-0.8, 0.3-0.7, 0.3-0.68, 0.3-0.64, 0. 3-0.6, 0.3-0.58, 0.3-0.56, 0.3-0.54, 0.3-0.52, 0.3-0.5, 0.3-0.48, 0.3-0.46, 0.3-0.44, 0.3-0.42, 0.3-0.4, 0.4-0.9, 0.4-0.8, 0.4-0.7, 0.4-0.68, 0.4-0.64, 0.4-0.6, 0.4-0.58, 0.4-0.56, 0.4-0.54, 0.4-0.52, 0.4-0.5, 0.5-0.9, 0.5-0.8, 0.5-0.7, 0.5-0.68, 0.5-0.64, 0.5-0.6.

[0096] In some embodiments, based on the total mass of the negative electrode active material layer as 100%, the mass fraction of Si element in the negative electrode active material layer is greater than or equal to 5% and less than 90%, for example, it can be 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, or any range of the above values.

[0097] Optionally, based on the total mass of the negative electrode active material layer as 100%, the mass fraction of Si element in the negative electrode active material layer can be 5%-84%, 10%-84%, 14%-84%, 18%-84%, 22%-84%, 26%-84%, 30%-84%, 5%-78%, 10%-78%, 14%-78%, 18%-78%, 22%-78%, 26%-78%, 30%-78%, 5%-72%, 10%-72%, 14%-72%, 18%-72%, 2 ... %-72%, 26%-72%, 30%-72%, 5%-66%, 10%-66%, 14%-66%, 18%-66%, 22%-66%, 26%-66%, 30%-66%, 5%-60%, 10%-60%, 14%-60%, 18%-60%, 22%-60%, 26%-60%, 30%-60%, 5%-50%, 10%-50%, 14%-50%, 18%-50%, 22%-50%, 26%-50%, 30%-50%.

[0098] In some embodiments, the mass fraction of Si element in the negative electrode active material layer is 5%-50%, and the NP ratio of the solid-state battery cell is 0.01-0.5.

[0099] Optionally, the mass fraction of Si element in the negative electrode active material layer is 5%-50%, and the NP ratio of the solid-state battery cell is 0.1-0.5.

[0100] Optionally, the mass fraction of Si element in the negative electrode active material layer is 5%-50%, and the NP ratio of the solid-state battery cell is 0.2-0.5.

[0101] Optionally, the mass fraction of Si element in the negative electrode active material layer is 10%-50%, and the NP ratio of the solid-state battery cell is 0.2-0.4.

[0102] When the NP ratio of the solid-state battery cell and the mass fraction of Si in the negative electrode active material layer are within the above range, the thickness uniformity of the negative electrode active material layer is good, and lithium is more likely to accumulate between silicon-based material particles, thus serving as a better lithium-ion transport channel. Lithium can also easily pass through the negative electrode active material layer and deposit between the negative electrode active material layer and the negative electrode current collector, which is more conducive to the stable cycling of the solid-state battery cell under low external pressure. In addition, the solid-state battery cell also has high initial coulombic efficiency and high cycle capacity retention.

[0103] In some embodiments, the mass fraction of Si element in the negative electrode active material layer is 20%-50%, and the NP ratio of the solid-state battery cell is 0.5-0.9.

[0104] Optionally, the mass fraction of Si in the negative electrode active material layer is 20%-50%, and the NP ratio of the solid-state battery cell is 0.5-0.7.

[0105] Optionally, the mass fraction of Si in the negative electrode active material layer is 20%-50%, and the NP ratio of the solid-state battery cell is 0.5-0.6.

[0106] When the NP ratio of a solid-state battery cell and the mass fraction of Si in the negative electrode active material layer are within the above-mentioned range, the negative electrode can have good kinetic performance. At the same time, lithium is more likely to accumulate between silicon-based material particles, thus serving as a better lithium-ion transport channel. Lithium can also easily pass through the negative electrode active material layer and deposit between the negative electrode active material layer and the negative electrode current collector, which is more conducive to the stable cycling of solid-state battery cells under low external pressure. In addition, solid-state battery cells also have high initial coulombic efficiency and high cycle capacity retention.

[0107] The silicon-based material is located within the pores of porous carbon. In some embodiments, the silicon-based material may include one or more of silicon, silicon-carbon, silicon oxide, silicon nitride, and silicon alloy materials.

[0108] In some embodiments, the silicon-carbon composite material may further include a coating layer located on at least a portion of the surface of the porous carbon.

[0109] Optionally, the coating layer may include one or more of carbon materials, metals, and conductive polymers.

[0110] In some embodiments, the preparation method of silicon-carbon composite material may include the following steps: coating asphalt onto the surface of a non-asphalt carbon source, and then performing heat treatment under a protective gas atmosphere to obtain a carbon material intermediate; mixing the obtained carbon material intermediate with an activator for activation treatment, acid washing, and drying to obtain porous carbon; and dispersing silicon-based materials into the pores of the porous carbon to obtain a silicon-carbon composite material.

[0111] Compared to non-asphalt carbon sources, carbon materials after asphalt carbonization react more readily with activators to form porous structures. This allows the prepared porous carbon to have porous outer regions while having no or few pores in the inner regions.

[0112] In some embodiments, the non-asphalt carbon source may include one or more of biomass precursors and resin precursors. For example, biomass precursors may include one or more of coconut shells, straw, walnut shells, sugar, and starch. For example, resin precursors may include one or more of phenolic resins and epoxy resins.

[0113] In some embodiments, asphalt may include one or more of coal tar pitch and petroleum asphalt.

[0114] In some embodiments, the temperature for heat treatment of asphalt and non-asphalt carbon sources can be 400℃-800℃, and the treatment time at the heat treatment temperature can be 1h-12h.

[0115] In some embodiments, the protective gas may include one or more of nitrogen, argon, and helium.

[0116] Porous carbon can be obtained by activating carbon material intermediates and activators.

[0117] In some embodiments, the activator may include one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, calcium oxide, magnesium oxide, magnesium hydroxide, melamine, aluminum oxide, sodium carbonate, and potassium carbonate.

[0118] In some embodiments, the mass ratio of the carbon material intermediate to the activator can be from 1:1 to 1:4.

[0119] Adjusting the mass ratio of non-asphalt carbon source to asphalt and the mass ratio of carbon material intermediate to activator can regulate the total pore area of ​​the external region and the total pore area of ​​the internal region of porous carbon.

[0120] It is understandable that a higher mass ratio of bitumen results in a higher total pore area in the external region of the prepared porous carbon; similarly, a higher mass ratio of activator results in a higher total pore area in the external region of the prepared porous carbon.

[0121] In some embodiments, the activation temperature can be 600℃-900℃, and the treatment time at the activation temperature can be 1h-12h.

[0122] In some embodiments, pickling may employ hydrochloric acid solution, sulfuric acid solution, acetic acid solution, or a mixture of at least two of these acid solutions.

[0123] In some embodiments, the method for dispersing silicon-based materials into the pores of porous carbon can be a vapor deposition method.

[0124] Vapor deposition methods can include chemical vapor deposition and physical vapor deposition, and can be selected as chemical vapor deposition, such as any one of thermochemical vapor deposition, plasma-enhanced chemical vapor deposition, and microwave plasma-assisted chemical vapor deposition.

[0125] In some embodiments, the step of dispersing silicon-based materials into the pores of porous carbon may include the following steps: placing the porous carbon in a vapor deposition chamber of a rotary kiln or fluidized bed, introducing a protective gas to replace the air, and then introducing a first mixed gas containing silicon source gas and protective gas at a first temperature for vapor deposition to obtain a silicon-carbon composite material.

[0126] In some embodiments, the first temperature can be 500°C-1000°C.

[0127] "Silicon source gas" refers to the gas that can form silicon-based materials.

[0128] In some embodiments, when the silicon source itself is solid or liquid, the silicon source can be vaporized or evaporated into gas before being introduced into the vapor deposition chamber.

[0129] In some embodiments, the silicon source gas may include silicon gas and / or silicon oxide gas, etc.

[0130] In some embodiments, the silicon source gas may include, but is not limited to, silane H4Si, silane H6Si2, propane H8Si3, silicon tetrachloride Cl4Si, trichlorosilane Cl3HSi, dichlorosilane Cl2H2Si, chlorosilane ClH3Si, silicon tetrafluoride F4Si, trifluorosilane F3HSi, difluorosilane F2H2Si, fluorosilane FH3Si, hexachlorodisilane Cl6Si2, pentachlorodisilane Cl5HSi2, 1,1,2,2-tetrachlorodisilane, 1,1,1,2-tetrachlorodisilane, 1,1,2-trichlorodisilane, 1,1,1-trichlorodisilane, 1,1-dichlorodisilane, 1,2-dichlorodisilane, monochlorodisilane ClH5Si2, and hexachlorodisilane. One or more of the following: disilane F6Si2, pentafluorodisilane F5HSi2, 1,1,2,2-tetrafluorodisilane F4H2Si2, 1,1,1-trifluorodisilane F3H3Si2, 1,1-difluorodisilane, 1,2-difluorodisilane, monofluorodisilane FH5Si2, methylsilane, ethylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, methyldisilane, dimethyldisilane, trimethyldisilane, tetramethyldisilane, hexamethylsilane, methyltrichlorosilane, methylchlorosilane, chloroethylsilane, dichlorodimethylsilane, dichlorodiethylsilane, dichlorodiethylsilane, tri(trimethylsilyl)silane, hexamethyldisilane, methylvinyldichlorosilane, dimethylvinylchlorosilane, and vinyltrichlorosilane.

[0131] In some embodiments, the protective gas in the first mixture may include one or more of nitrogen, argon, and helium.

[0132] In some embodiments, the volume percentage of silicon source gas in the first mixture can be 10%-50%.

[0133] In some embodiments, the first mixture may further include a carbon source gas. Optionally, the carbon source gas may include, but is not limited to, one or more of methane, ethane, propane, isopropane, butane, isobutane, ethylene, propylene, butene, acetylene, chloroethane, fluoroethane, difluoroethane, chloromethane, fluoromethane, difluoromethane, trifluoromethane, vinyl chloride, vinyl fluoride, difluoroethylene, methylamine, formaldehyde, benzene, toluene, xylene, styrene, and phenol.

[0134] In some embodiments, the pressure in the vapor deposition chamber can be a slightly positive pressure; alternatively, the pressure in the vapor deposition chamber can be 200 Pa to 600 Pa higher than atmospheric pressure.

[0135] In some embodiments, the step of dispersing silicon-based materials into the pores of porous carbon may further include the following steps: placing the porous carbon in a vapor deposition chamber of a rotary kiln or fluidized bed, introducing a protective gas to replace the air, then introducing a first mixed gas containing silicon source gas and protective gas at a first temperature for vapor deposition, then stopping the introduction of the first mixed gas, and introducing a second mixed gas containing carbon source gas and protective gas at a second temperature for carbon deposition coating to obtain a silicon-carbon composite material.

[0136] Optionally, the protective gas in the second mixture may include one or more of nitrogen, argon, and helium.

[0137] Optionally, the second temperature can be 600℃-800℃.

[0138] Optionally, the volume percentage of the carbon source gas in the second mixture can be 10%-50%.

[0139] Optionally, the carbon source gas in the second mixture may be one or more of the following: methane, ethane, propane, isopropane, butane, isobutane, ethylene, propylene, butene, acetylene, chloroethane, fluoroethane, difluoroethane, chloromethane, fluoromethane, difluoromethane, trifluoromethane, vinyl chloride, vinyl fluoride, difluoroethylene, methylamine, formaldehyde, benzene, toluene, xylene, styrene, and phenol.

[0140] In some embodiments, the volumetric particle size Dv50 of the silicon-carbon composite material can be 500 nm to 20 μm, for example, it can be 500 nm, 800 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or any range of the above values.

[0141] Optionally, the volume distribution particle size Dv50 of the silicon-carbon composite material can be 500nm-10μm, 500nm-8μm, 500nm-5μm, 1μm-10μm, 1μm-8μm, 1μm-5μm, 2μm-10μm, 2μm-8μm, or 2μm-5μm.

[0142] In some embodiments, the negative electrode active material layer may further include metal particles located between silicon-based material particles, which can form an alloy or solid solution with lithium.

[0143] Metal particles can alloy with lithium or form solid solutions, which facilitates lithium transfer between silicon-based material particles, facilitates lithium penetration through the negative electrode active material layer and deposition between the negative electrode active material layer and the negative electrode current collector.

[0144] Optionally, the metal particles may include one or more of Ag, Mg, Au, Cu, and Ti.

[0145] Optionally, the mass of the metal particles can be 1% to 10% of the mass of the silicon-based material, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of the above values.

[0146] Understandably, increasing the mass fraction of metal particles is more conducive to promoting lithium transfer between silicon-based material particles and facilitating lithium penetration through the negative electrode active material layer and deposition between the negative electrode active material layer and the negative electrode current collector. However, when the mass fraction of metal particles is too high, a voltage plateau will appear in the charge-discharge curve of the solid-state battery cell, which will actually accelerate the capacity decay of the solid-state battery cell. Therefore, a metal particle mass fraction within the aforementioned range is beneficial for promoting lithium transfer between silicon-based material particles, facilitating lithium penetration through the negative electrode active material layer and deposition between the negative electrode active material layer and the negative electrode current collector, and also allows the solid-state battery cell to have better cycle performance.

[0147] Alternatively, the mass of the metal particles can be 2%-10%, 3%-10%, 4%-10%, 5%-10%, 2%-9%, 3%-9%, 4%-9%, or 5%-9% of the mass of the silicon-based material.

[0148] In some embodiments, the volume distribution particle size Dv50 of the metal particles can be 20nm-100nm, for example, it can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or any range of the above values.

[0149] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent.

[0150] The negative electrode conductive agent may include one or more of the following: linear conductive agent, planar conductive agent, and spherical conductive agent.

[0151] Optionally, the negative electrode conductive agent may include a linear conductive agent. A linear conductive agent facilitates the formation of a better electronic conductive network in the negative electrode active material layer, thereby promoting rapid lithium transfer between silicon-based material particles, and promoting rapid lithium penetration through the negative electrode active material layer and deposition between the negative electrode active material layer and the negative electrode current collector.

[0152] Optionally, the linear conductive agent may include one or more of carbon nanotubes (CNTs), carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0153] Alternatively, the planar conductive agent may include graphene.

[0154] Optionally, the spherical conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, and carbon dots.

[0155] Optionally, the mass fraction of the negative electrode conductive agent in the negative electrode active material layer can be greater than or equal to 0 and less than or equal to 5%.

[0156] In some embodiments, the negative electrode active material layer may further include a negative electrode binder.

[0157] Optionally, the negative electrode binder 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, 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, butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0158] In some embodiments, the negative electrode active material layer may further include a solid electrolyte material.

[0159] Optionally, the solid electrolyte material in the negative electrode active material layer may include one or more of the following: sulfide solid electrolyte material, halide solid electrolyte material, oxide solid electrolyte material, and polymer solid electrolyte material.

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

[0161] Optionally, the sulfide solid electrolyte material of the silver-germanium sulfide type may include Li 6±s P 1-j A j S 5±s-t B t X 1±s The material has the following properties: 0≤j<1, 0≤t<1, 0≤s<1, A includes one or more elements from Ge, Si, Sn and Sb, B includes one or more elements from O, Se and Te, and X includes one or more elements from Cl, Br, I and F.

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

[0163] Optionally, the sulfide solid electrolyte material of the lithium sulfide - phosphorus pentasulfide composite type 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] As an example, the sulfide solid electrolyte material may include, but is not limited to, Li6PS5Cl, Li6PS5Br, Li 10 GeP2S 12 、Li3PS4、Li7P3S 11 and one or more of them. <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​In some embodiments, the polymer solid electrolyte material may be formed by complexing a polymer matrix material with a lithium salt. Optionally, the polymer matrix material may be one or more of, but not limited to, polyethylene oxide (PEO) and its derivatives, polypropylene oxide (PPO) and its derivatives, polycarbonate (PPC), polyacrylonitrile (PAN), polysiloxane (PDMS), polyvinylidene fluoride (PVDF), and polymethyl methacrylate (PMMA). Optionally, the lithium salt may be one or more of, but not limited to, LiClO4, LiAsF4, LiPF6, LiBF4, LiTFSI, and LiFSI.

[0169] Optionally, the polymer solid electrolyte material may also include an inert filler, which can reduce the crystallinity of the polymer and improve its mechanical properties. Optionally, the inert filler may include, but is not limited to, one or more of TiO2, Al2O3, ZrO2, and SiO2.

[0170] Optionally, the mass fraction of the solid electrolyte material in the negative electrode active material layer can be greater than 0 and less than or equal to 15%.

[0171] In some embodiments, the porosity of the negative electrode active material layer can be 10%-20%, for example, it can be 10%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any range of the above values.

[0172] When the porosity of the negative electrode active material layer is within the above range, the silicon-carbon composite material has good electronic contact, which is beneficial to improving the lithium-ion transport performance of the negative electrode and enhancing the cycle stability and kinetic performance of the solid-state battery cell.

[0173] Solid-state battery cells require pressing processes during fabrication, such as hot pressing, cold isostatic pressing, or warm isostatic pressing. The porosity range of the negative electrode active material layer mentioned above refers to the porosity of the negative electrode active material layer after pressing, and the porosity of the negative electrode active material layer mentioned above refers to the porosity of the negative electrode active material layer after the solid-state battery cell has been discharged. The porosity test results of the negative electrode active material layer will change after the solid-state battery cell has been fully charged.

[0174] The porosity of the negative electrode active material layer can be tested as follows: After fully discharging a fresh solid-state battery cell, the negative electrode layer is removed and prepared as a single-sided coated negative electrode layer (if it is a double-sided coated negative electrode layer, the negative electrode active material layer on one side can be wiped off first). This is then cut into small circular samples of a certain area, and the apparent volume V1 of the sample is calculated. Referring to GB / T24586-2009, using inert nitrogen gas as the medium, the true volume V2 of the sample is measured using a gas displacement method and a true density meter. The porosity of the negative electrode active material layer = (V1-V2) / V1×100%. Multiple samples (e.g., 30 samples) with good appearance and no powder shedding at the edges can be tested, and the average value of the results is taken, which can improve the accuracy of the test results. The testing instrument can be a Micromeritics AccuPyc II 1340 true density meter.

[0175] In some embodiments, the thickness of the negative electrode active material layer can be 2μm-35μm, for example, it can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, 34μm, 35μm, or any range of the above values.

[0176] Optionally, the thickness of the negative electrode active material layer can be 2μm-30μm, 2μm-25μm, 2μm-20μm, 2μm-15μm, 4μm-30μm, 4μm-25μm, 4μm-20μm, or 4μm-15μm.

[0177] In some embodiments, the negative electrode layer may further include a lithium-based metal layer located between the negative electrode current collector and the negative electrode active material layer.

[0178] The lithium-based metal layer can compensate for the irreversible lithium loss from the negative electrode active material layer, thereby improving the cycle stability of solid-state battery cells. When a solid-state battery cell is working, in addition to some lithium undergoing alloying and lithium intercalation reactions with the silicon-carbon composite material, excess lithium will accumulate between the silicon-carbon composite material particles and deposit on the surface of the lithium-based metal layer, that is, deposited between the lithium-based metal layer and the negative electrode active material layer.

[0179] In some embodiments, the lithium-based metal layer may include lithium or a lithium alloy, optionally including lithium.

[0180] In some embodiments, the lithium-based metal layer can continuously cover the surface of the negative electrode current collector.

[0181] In some embodiments, the lithium-based metal layer is discontinuous in the length and / or width direction of the negative electrode current collector, that is, the surface of the negative electrode current collector has intermittent regions where no lithium-based metal layer is disposed.

[0182] In some embodiments, the thickness of the lithium-based metal layer can be 0.5μm-50μm, for example, it can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, 34μm, 36μm, 38μm, 40μm, 42μm, 44μm, 46μm, 48μm, 50μm, or any range of the above values.

[0183] Optionally, the thickness of the lithium-based metal layer can be 1μm-30μm, 1μm-20μm, 1μm-15μm, 1μm-10μm, 3μm-30μm, 3μm-20μm, 3μm-15μm, 3μm-10μm, 5μm-30μm, 5μm-20μm, 5μm-15μm, or 5μm-10μm.

[0184] In some embodiments, the lithium-based metal layer may be a lithium-based metal layer with a passivation layer on its surface.

[0185] Optionally, the passivation layer may include one or more of Li2O, Li2O2, Li2CO3, and LiOH.

[0186] Optionally, the thickness of the passivation layer can be greater than 0 and less than or equal to 30 nm, for example, it can be 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, 30 nm, or any range of the above values. More preferably, the thickness of the passivation layer can be 2 nm-30 nm, 4 nm-30 nm, 6 nm-30 nm, 8 nm-30 nm, or 10 nm-30 nm.

[0187] The negative electrode current collector has two surfaces opposite each other in its thickness direction, and the negative electrode active material layer is disposed on one or both of the two opposite surfaces of the negative electrode current collector.

[0188] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The metal foil may be a pure metal, an alloy, or a surface-treated metal, such as, but not limited to, stainless steel foil, copper foil, and nickel foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal layer may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0189] The negative electrode layer can be prepared by either a dry process or a wet process.

[0190] [Positive electrode layer]

[0191] The positive electrode layer can be prepared by either a dry process or a wet process.

[0192] In some embodiments, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a solid electrolyte material and a positive electrode active material.

[0193] In some embodiments, the positive current collector may be a metal foil or a composite current collector. The metal foil may be a pure metal, an alloy, or a surface-treated metal, such as, but not limited to, stainless steel foil, carbon-coated aluminum foil, or aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal layer may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0194] In some embodiments, the positive electrode layer may not require an additional positive electrode current collector; for example, the stainless steel sheet of the mold battery can be directly used as the positive electrode current collector.

[0195] In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides and their modified forms, lithium phosphates and their modified forms, lithium titanate, lithium niobate, sulfur, selenium, and tellurium.

[0196] Optionally, 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, and lithium-rich manganese-based materials.

[0197] Optionally, examples of lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0198] In some embodiments, to further improve the energy density of a solid-state battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e A f One or more of lithium transition metal oxides and their modified materials. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A may include one or more of N, F, S and Cl.

[0199] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 One or more of O2, LiFePO4, LiMnPO4 and their respective modified materials.

[0200] The modified materials for the above-mentioned positive electrode active materials can be doped and / or surface coated.

[0201] During the charging and discharging process, solid-state battery cells undergo Li insertion / extraction and consumption, resulting in varying Li molar content at different discharge states. In this disclosure, the Li molar content listed for positive electrode active materials represents the initial state of the material, i.e., the state before material addition. As the positive electrode active material is applied to a solid-state battery cell, the Li molar content changes after charge-discharge cycles. Similarly, the O molar content listed for positive electrode active materials in this disclosure is only a theoretical value; lattice oxygen release causes changes in the O molar content, leading to fluctuations in the actual O molar content.

[0202] In some embodiments, the solid electrolyte material in the positive electrode layer may include one or more of the following: sulfide solid electrolyte material, halide solid electrolyte material, oxide solid electrolyte material, and polymer solid electrolyte material.

[0203] In some embodiments, the sulfide solid electrolyte material may include, but is not limited to, one or more of the following: silver-germanium sulfide type, LGPS type, lithium sulfide-phosphorus pentasulfide complex type sulfide solid electrolyte materials.

[0204] Optionally, the sulfide solid electrolyte material of the silver-germanium sulfide type may include Li 6±s P 1-j A j S 5±s-t B t X 1±s The material has the following properties: 0≤j<1, 0≤t<1, 0≤s<1, A includes one or more elements from Ge, Si, Sn and Sb, B includes one or more elements from O, Se and Te, and X includes one or more elements from Cl, Br, I and F.

[0205] Optionally, LGPS-type sulfide solid electrolyte materials may include those with the chemical formula Li 10±δ5 Ge 1-g G g P 2-q Q q S 12- w W w The material has the following properties: 0≤δ5<1, 0≤g≤1, 0≤q≤2, 0≤w<1, G includes one or two elements from Si and Sn, Q includes Sb, and W includes one or more elements from O, Se, Te, Cl, Br, I, and F.

[0206] 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.

[0207] As an example, the sulfide solid electrolyte material may include, but is not limited to, Li6PS5Cl, Li6PS5Br, Li 10 GeP2S 12 、Li3PS4、Li7P3S 11 and one or more of the above.

[0208] In some embodiments, the halide solid electrolyte material may include, but is not limited to, one or more of Li3YCl6, Li3YBr6, Li3ErCl6, Li3InCl6, and Li3InBr6.

[0209] In some embodiments, the oxide solid electrolyte material may include one or more of NASICON - type solid electrolytes, LISICON - type solid electrolytes, perovskite - type solid electrolytes, and garnet - type solid electrolytes.

[0210] As an example, the oxide solid electrolyte material may include, but is not limited to, Li5La3Ti2O 12 、Li7La3Zr2O 12 、Li4Ti5O 12 、Li 14 Zn(GeO4)4、LiTi2(PO4)3、Li 1+x Al x Ti 2-x (PO4)3、Li 1+y Al y Ge 2-y (PO4)3, and one or more of the above, where 0 < x < 2, 0 < y < 2.

[0211] ​In some embodiments, the polymer solid electrolyte material may be formed by complexing a polymer matrix material with a lithium salt. Optionally, the polymer matrix material may be one or more of, but not limited to, polyethylene oxide (PEO) and its derivatives, polypropylene oxide (PPO) and its derivatives, polycarbonate (PPC), polyacrylonitrile (PAN), polysiloxane (PDMS), polyvinylidene fluoride (PVDF), and polymethyl methacrylate (PMMA). Optionally, the lithium salt may be one or more of, but not limited to, LiClO4, LiAsF4, LiPF6, LiBF4, LiTFSI, and LiFSI.

[0212] Optionally, the polymer solid electrolyte material may also include an inert filler, which can reduce the crystallinity of the polymer and improve its mechanical properties. Optionally, the inert filler may include, but is not limited to, one or more of TiO2, Al2O3, ZrO2, and SiO2.

[0213] In some embodiments, the positive electrode active material layer may further include a positive electrode conductive agent.

[0214] Optionally, the positive electrode conductive agent may be one or more of the following, including but not limited to superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes (CNTs), graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0215] In some embodiments, the positive electrode active material layer may or may not include a positive electrode binder, and can be adjusted according to the positive electrode composition and the preparation process of the solid-state battery cell.

[0216] Optionally, the positive electrode binder 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, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, 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.

[0217] [Electrolyte layer]

[0218] The electrolyte layer can be prepared by a dry process or a wet process.

[0219] In some embodiments, the electrolyte layer comprises a solid electrolyte material.

[0220] Optionally, the solid-state electrolyte material may include one or more of sulfide solid-state electrolyte materials, halide solid-state electrolyte materials, oxide solid-state electrolyte materials, and polymer solid-state electrolyte materials.

[0221] In some embodiments, the sulfide solid-state electrolyte material may include, but is not limited to, one or more of argyrodite-type, LGPS-type, and lithium sulfide diphosphorus pentasulfide composite-type sulfide solid-state electrolyte materials.

[0222] Optionally, the argyrodite-type sulfide solid-state 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.

[0223] Optionally, the LGPS-type sulfide solid-state 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 W w , 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.

[0224] Optionally, the lithium sulfide diphosphorus pentasulfide composite-type sulfide solid-state 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.

[0225] As an example, the sulfide solid-state electrolyte material may include, but is not limited to, one or more of Li6PS5Cl, Li6PS5Br, Li 10 GeP2S 12 , Li3PS4, Li7P3S 11 .

[0226] In some embodiments, the halide solid electrolyte material may include, but is not limited to, one or more of Li3YCl6, Li3YBr6, Li3ErCl6, Li3InCl6, and Li3InBr6.

[0227] In some embodiments, the oxide solid electrolyte material may include one or more of the following: NASICON type solid electrolyte, LISICON type solid electrolyte, perovskite type solid electrolyte, and garnet type solid electrolyte.

[0228] As an example, oxide solid electrolyte materials may include, but are not limited to, Li5La3Ti2O 12 Li7La3Zr2O 12 Li4Ti5O 12 Li 14 Zn(GeO4)4, LiTi2(PO4)3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+y Al y Ge 2-y One or more of (PO4)3, 0 < x < 2, 0 < y < 2.

[0229] In some embodiments, the polymer solid electrolyte material may be formed by complexing a polymer matrix material with a lithium salt. Optionally, the polymer matrix material may be one or more of, but not limited to, polyethylene oxide (PEO) and its derivatives, polypropylene oxide (PPO) and its derivatives, polycarbonate (PPC), polyacrylonitrile (PAN), polysiloxane (PDMS), polyvinylidene fluoride (PVDF), and polymethyl methacrylate (PMMA). Optionally, the lithium salt may be one or more of, but not limited to, LiClO4, LiAsF4, LiPF6, LiBF4, LiTFSI, and LiFSI.

[0230] Optionally, the polymer solid electrolyte material may also include an inert filler, which can reduce the crystallinity of the polymer and improve its mechanical properties. Optionally, the inert filler may include, but is not limited to, one or more of TiO2, Al2O3, ZrO2, and SiO2.

[0231] In some embodiments, the electrolyte layer may or may not include a binder, depending on the manufacturing process of the solid-state battery cell. Optionally, the binder 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, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0232] In some embodiments, the solid-state battery cell may further include an outer packaging for accommodating the electrode assembly formed by assembling the negative electrode layer, electrolyte layer, and positive electrode layer. The outer packaging may be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging may also be a flexible package, such as a pouch. The material of the flexible package may be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0233] [Preparation Method]

[0234] The methods for preparing solid-state battery cells are well known. For example, the assembly methods of solid-state battery cells include, but are not limited to, coin cells, mold cells, hard-case cells, and pouch cells.

[0235] In some embodiments, the method for preparing a solid-state battery cell includes the following steps: providing a negative electrode layer, an electrolyte layer, and a positive electrode layer; assembling the negative electrode layer, electrolyte layer, and positive electrode layer; and pressing them to obtain a solid-state battery cell. The electrolyte layer is located between the negative electrode layer and the positive electrode layer. The negative electrode layer includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon-based material located in the pores of the porous carbon. The region formed by extending from the outer surface of the porous carbon particles to the interior of the particles at a distance of 0.5 times the length between any point on the outer surface of the particles and the particle core is denoted as the outer region of the porous carbon. The region inside the outer region of the porous carbon is denoted as the inner region of the porous carbon. The total pore area of ​​the inner region of the porous carbon is 0%-10% of the total pore area of ​​the outer region of the porous carbon. The NP ratio of the solid-state battery cell is greater than 0 and less than 1. The NP ratio is the ratio of the unit area capacity of the negative electrode to the unit area capacity of the positive electrode.

[0236] Alternatively, the pressing process can be flat hot pressing, cold isostatic pressing, or warm isostatic pressing.

[0237] Example

[0238] The following embodiments describe the disclosure of 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 this 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.

[0239] Example 1

[0240] Preparation of silicon-carbon composite materials

[0241] Asphalt was used as a coating layer to coat clean, dry coconut shell granules, with a coating thickness of 1 μm. The granules were then placed in a box furnace and heated to 700°C under a nitrogen atmosphere for 8 hours to obtain a carbon material intermediate. The obtained carbon material intermediate was mixed with potassium hydroxide at a mass ratio of 1:3 and then placed in a box furnace and heated to 800°C under a nitrogen atmosphere for 6 hours. The material was then removed and mixed thoroughly in a 0.1 mol / L hydrochloric acid aqueous solution to remove residual potassium hydroxide. Afterward, it was heated and dried to obtain porous carbon with a total pore area of ​​10 × 10⁻⁶ pores in the external region. 4 cm 2 / g, with no pores in the internal region. Porous carbon was placed in the vapor deposition chamber of a rotary kiln, and argon gas was introduced to replace the air. The temperature of the vapor deposition chamber was then heated to 500℃, and a silane / argon mixture with 70% argon and 30% silane was introduced while maintaining a slightly positive pressure inside the furnace for silicon vapor deposition. The silane / argon mixture was then stopped, and the temperature of the vapor deposition chamber was adjusted to 750℃. An acetylene / argon mixture with 80% argon and 20% acetylene was then introduced for carbon deposition and coating. After completion, the silicon-carbon composite material was obtained by sieving. The volumetric particle size distribution (Dv50) of the silicon-carbon composite material was 2 μm.

[0242] Preparation of negative electrode layer

[0243] The silicon-carbon composite material, polyvinylidene fluoride (PVDF) as the negative electrode binder, and vapor-grown carbon fiber (VGCF) as the negative electrode conductive agent were uniformly dispersed in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel current collector, and subsequently baked in an oven to remove the solvent. Finally, it was cut to a suitable size and electrode tabs were welded to obtain the negative electrode layer. The negative electrode capacity per unit area was 2.7 mAh / cm². 2 With the total mass of the negative electrode active material layer as 100%, the mass fraction of Si element in the negative electrode active material layer is 32%.

[0244] Preparation of positive electrode layer

[0245] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, solid electrolyte material Li6PS5Cl, positive electrode conductive agent vapor-grown carbon fiber VGCF, and positive electrode binder polytetrafluoroethylene (PTFE) are mixed uniformly at a solid mass ratio of 70:25.5:2.5:2. The mixture is heated on an 80°C heating platform and repeatedly rolled to form a dry-process positive electrode active material layer. This layer is then laminated with aluminum foil as a positive electrode current collector using a hot roller, cut to the appropriate size, and welded with tabs to obtain the positive electrode layer. The positive electrode's unit area capacity is 3 mAh / cm². 2 .

[0246] Preparation of electrolyte layer

[0247] The solid electrolyte material Li6PS5Cl and the binder polytetrafluoroethylene (PTFE) were mixed evenly at a solid mass ratio of 98:2, heated on a heating table at 80°C, and rolled back and forth to form a dry electrolyte layer.

[0248] Preparation of solid-state battery cells

[0249] The prepared positive electrode layer, electrolyte layer, and negative electrode layer were assembled in an alternating stacked manner and hot-pressed. Then, they were encapsulated under negative pressure with an aluminum-plastic film to obtain a soft-pack solid-state battery cell. The NP ratio of the solid-state battery cell was 0.9. After hot-pressing, the porosity of the negative electrode active material layer was 15%.

[0250] Example 2

[0251] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0252] The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 2.1 mAh / cm². 2 The NP ratio of a solid-state battery cell is 0.7.

[0253] Example 3

[0254] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0255] The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 1.8 mAh / cm². 2 The NP ratio of a solid-state battery cell is 0.6.

[0256] Example 4

[0257] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0258] The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 1.5 mAh / cm². 2 The NP ratio of a solid-state battery cell is 0.5.

[0259] Example 5

[0260] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0261] The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 1.2 mAh / cm². 2 The NP ratio of a solid-state battery cell is 0.4.

[0262] Example 6

[0263] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0264] The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 0.9 mAh / cm². 2 The NP ratio of a solid-state battery cell is 0.3.

[0265] Comparative Example 1

[0266] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0267] Preparation of negative electrode layer

[0268] Commercially available silicon-carbon material (negative electrode active material), polyvinylidene fluoride (PVDF) binder, and vapor-grown carbon fiber (VGCF) conductive agent were dispersed evenly in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel negative electrode current collector, baked in an oven to remove the solvent, and finally cut to the appropriate size and welded with tabs to obtain the negative electrode layer. The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 3 mAh / cm². 2 The NP ratio of the solid-state battery cell is 1. Taking the total mass of the negative electrode active material layer as 100%, the mass fraction of Si in the negative electrode active material layer is 32%. The mass fraction of Si in the silicon-carbon material is 33%, and the mass fraction of C is 67%. The volumetric particle size Dv50 of the silicon-carbon material is 2 μm. The total pore area of ​​the outer region of the porous carbon in the silicon-carbon material is 9 × 10⁻⁶. 4 cm 2 / g, the total pore area of ​​the internal region is 3.2×10 4 cm 2 / g.

[0269] Performance testing

[0270] (1) First coulombic efficiency test of solid-state battery cell

[0271] At 25°C, solid-state battery cells were charged to 4.3V (vs. Li) at a current density of 0.1C. + / Li), let stand for 10 minutes, then discharge at a current density of 0.1C to 2V (vs. Li). + / Li), to obtain the specific capacity of the first charge and the specific capacity of the first discharge.

[0272] The initial coulombic efficiency (%) of a solid-state battery cell = first discharge specific capacity / first charge specific capacity × 100%.

[0273] (2) Rate performance test of solid-state battery cells

[0274] At 25°C, the solid-state battery cells were first charged to 4.3V (vs. Li) at a current density of 0.1C. + / Li), let stand for 10 minutes, then discharge at a current density of 0.1C to 2V (vs. Li). + / Li), and the capacity obtained by 3 cycles of charge and discharge is recorded as the discharge specific capacity at a rate of 0.1C;

[0275] The solid-state battery cells were then charged to 4.3V (vs. Li) at a current density of 0.33C. + / Li), let stand for 10 minutes, then discharge to 2V at a current density of 0.33C (vs. Li). + / Li), the obtained capacity is recorded as the discharge specific capacity at a rate of 0.33C;

[0276] The solid-state battery cells are then charged to 4.3V (vs. Li) at a current density of 0.5C. + / Li), let stand for 10 minutes, then discharge at a current density of 0.5C to 2V (vs. Li). + / Li), the obtained capacity is recorded as the discharge specific capacity at a rate of 0.5C;

[0277] The solid-state battery cells are then charged to 4.3V (vs. Li) at a current density of 1C. + / Li), let stand for 10 minutes, then discharge at a current density of 1C to 2V (vs. Li). + The capacity obtained is denoted as the discharge specific capacity at a 1C rate ( / Li).

[0278] (3) Cyclic performance test of solid-state battery cells

[0279] At 25°C, the solid-state battery cells were first charged to 4.3V (vs. Li) at a current density of 0.1C. + / Li), let stand for 10 minutes, then discharge at a current density of 0.1C to 2V (vs. Li).+ / Li), cycle charge and discharge 3 times, the discharge specific capacity at this time is recorded as C1. Cycle charge and discharge a solid-state battery cell 50 times at a current density of 0.33C, the discharge specific capacity at this time is recorded as C2.

[0280] The capacity retention rate of a solid-state battery cell after 50 cycles at a current density of 0.33C is calculated as C2 / C1 × 100%.

[0281] During the above test, an external pressure of 5 MPa was applied to the solid-state battery cell.

[0282] Table 1

[0283] The test results above show that by making the total pore area of ​​the internal region of porous carbon 0%-10% of the total pore area of ​​the external region of porous carbon, and by making the NP ratio of the solid-state battery cell greater than 0 and less than 1, the solid-state battery cell has high initial coulombic efficiency, good cycle stability and good rate performance under low external pressure.

[0284] In Comparative Example 1, the total pore area of ​​the internal region of the porous carbon is more than 10% greater than the total pore area of ​​the external region. This results in a higher deposition of silicon in the internal region of the porous carbon, which reduces the initial coulombic efficiency and capacity retention of the solid-state battery cell. Furthermore, the NP ratio of the solid-state battery cell in Comparative Example 1 is 1. When the solid-state battery cell operates under low external pressure, lithium is difficult to deposit between the negative electrode active material layer and the negative electrode current collector, leading to significant volume expansion of the negative electrode active material layer and rapid capacity decay after multiple cycles.

[0285] Example 7

[0286] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0287] Preparation of silicon-carbon composite materials

[0288] Asphalt was used as a coating layer to coat clean, dry coconut shell granules, with a coating thickness of 1 μm. The granules were then placed in a box furnace and heated to 700°C under a nitrogen atmosphere for 8 hours to obtain a carbon material intermediate. The obtained carbon material intermediate was mixed with potassium hydroxide at a mass ratio of 1:2.5 and then placed in a box furnace and heated to 800°C under a nitrogen atmosphere for 6 hours. The material was then removed and mixed thoroughly in a 0.1 mol / L hydrochloric acid aqueous solution to remove residual potassium hydroxide. After heating and drying, porous carbon was obtained. The total pore area of ​​the outer region of the porous carbon was 8 × 10⁻⁶. 4 cm 2 / g, with no pores in the internal region. Porous carbon was placed in the vapor deposition chamber of a rotary kiln, and argon gas was introduced to replace the air. The temperature of the vapor deposition chamber was then heated to 500℃, and a silane / argon mixture with 70% argon and 30% silane was introduced while maintaining a slightly positive pressure inside the furnace for silicon vapor deposition. The silane / argon mixture was then stopped, and the temperature of the vapor deposition chamber was adjusted to 750℃. An acetylene / argon mixture with 80% argon and 20% acetylene was then introduced for carbon vapor deposition. After completion, the carbon was sieved to obtain a silicon-carbon composite material. The volumetric particle size distribution (Dv50) of the silicon-carbon composite material was 2 μm.

[0289] Preparation of negative electrode layer

[0290] The silicon-carbon composite material, polyvinylidene fluoride (PVDF) as the negative electrode binder, and vapor-grown carbon fiber (VGCF) as the negative electrode conductive agent were uniformly dispersed in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel current collector and baked in an oven to remove the solvent. Finally, it was cut to a suitable size and electrode tabs were welded to obtain the negative electrode layer. The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 0.9 mAh / cm². 2 The NP ratio of the solid-state battery cell is 0.3. Based on the total mass of the negative electrode active material layer as 100%, the mass fraction of Si in the negative electrode active material layer is 25.6%.

[0291] Example 8

[0292] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0293] Preparation of silicon-carbon composite materials

[0294] Asphalt was used as a coating layer to coat clean, dry coconut shell granules, with a coating thickness of 1 μm. The granules were then placed in a box furnace and heated to 700°C under a nitrogen atmosphere for 8 hours to obtain a carbon material intermediate. The obtained carbon material intermediate was mixed with potassium hydroxide at a mass ratio of 1:2 and then placed in a box furnace and heated to 800°C under a nitrogen atmosphere for 6 hours. The material was then removed and mixed thoroughly in a 0.1 mol / L hydrochloric acid aqueous solution to remove residual potassium hydroxide. Afterward, it was heated and dried to obtain porous carbon with a total pore area of ​​6 × 10⁻⁶ pores in the outer region. 4 cm 2 / g, with no pores in the internal region. Porous carbon was placed in the vapor deposition chamber of a rotary kiln, and argon gas was introduced to replace the air. The temperature of the vapor deposition chamber was then heated to 500℃, and a silane / argon mixture with 70% argon and 30% silane was introduced while maintaining a slightly positive pressure inside the furnace for silicon vapor deposition. The silane / argon mixture was then stopped, and the temperature of the vapor deposition chamber was adjusted to 750℃. An acetylene / argon mixture with 80% argon and 20% acetylene was then introduced for carbon vapor deposition. After completion, the carbon was sieved to obtain a silicon-carbon composite material. The volumetric particle size distribution (Dv50) of the silicon-carbon composite material was 2 μm.

[0295] Preparation of negative electrode layer

[0296] The silicon-carbon composite material, polyvinylidene fluoride (PVDF) as the negative electrode binder, and vapor-grown carbon fiber (VGCF) as the negative electrode conductive agent were uniformly dispersed in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel current collector and baked in an oven to remove the solvent. Finally, it was cut to a suitable size and electrode tabs were welded to obtain the negative electrode layer. The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 0.9 mAh / cm². 2 The NP ratio of the solid-state battery cell is 0.3. Based on the total mass of the negative electrode active material layer as 100%, the mass fraction of Si in the negative electrode active material layer is 19.2%.

[0297] Example 9

[0298] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0299] Preparation of silicon-carbon composite materials

[0300] Asphalt was used as a coating layer to coat clean, dry coconut shell granules, with a coating thickness of 1 μm. The granules were then placed in a box furnace and heated to 700°C under a nitrogen atmosphere for 8 hours to obtain a carbon material intermediate. The obtained carbon material intermediate was mixed with potassium hydroxide at a mass ratio of 1:1.8 and then placed in a box furnace and heated to 800°C under a nitrogen atmosphere for 6 hours. The material was then removed and mixed thoroughly in a 0.1 mol / L hydrochloric acid aqueous solution to remove residual potassium hydroxide. After heating and drying, porous carbon was obtained. The total pore area of ​​the outer region of the porous carbon was 4 × 10⁻⁶. 4 cm 2 / g, with no pores in the internal region. Porous carbon was placed in the vapor deposition chamber of a rotary kiln, and argon gas was introduced to replace the air. The temperature of the vapor deposition chamber was then heated to 500℃, and a silane / argon mixture with 70% argon and 30% silane was introduced while maintaining a slightly positive pressure inside the furnace for silicon vapor deposition. The silane / argon mixture was then stopped, and the temperature of the vapor deposition chamber was adjusted to 750℃. An acetylene / argon mixture with 80% argon and 20% acetylene was then introduced for carbon vapor deposition. After completion, the carbon was sieved to obtain a silicon-carbon composite material. The volumetric particle size distribution (Dv50) of the silicon-carbon composite material was 2 μm.

[0301] Preparation of negative electrode layer

[0302] The silicon-carbon composite material, polyvinylidene fluoride (PVDF) as the negative electrode binder, and vapor-grown carbon fiber (VGCF) as the negative electrode conductive agent were uniformly dispersed in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel current collector and baked in an oven to remove the solvent. Finally, it was cut to a suitable size and electrode tabs were welded to obtain the negative electrode layer. The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 0.9 mAh / cm². 2 The NP ratio of the solid-state battery cell is 0.3. Based on the total mass of the negative electrode active material layer as 100%, the mass fraction of Si in the negative electrode active material layer is 16.8%.

[0303] Example 10

[0304] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0305] Preparation of silicon-carbon composite materials

[0306] Asphalt was used as a coating layer to coat clean, dry coconut shell granules, with a coating thickness of 1 μm. The granules were then placed in a box furnace and heated to 700°C under a nitrogen atmosphere for 8 hours to obtain a carbon material intermediate. The obtained carbon material intermediate was mixed with potassium hydroxide at a mass ratio of 1:1.6 and then placed in a box furnace and heated to 800°C under a nitrogen atmosphere for 6 hours. The material was then removed and mixed thoroughly in a 0.1 mol / L hydrochloric acid aqueous solution to remove residual potassium hydroxide. After heating and drying, porous carbon was obtained. The total pore area of ​​the outer region of the porous carbon was 1 × 10⁻⁶. 4 cm 2 / g, with no pores in the internal region. Porous carbon was placed in the vapor deposition chamber of a rotary kiln, and argon gas was introduced to replace the air. The temperature of the vapor deposition chamber was then heated to 500℃, and a silane / argon mixture with 70% argon and 30% silane was introduced while maintaining a slightly positive pressure inside the furnace for silicon vapor deposition. The silane / argon mixture was then stopped, and the temperature of the vapor deposition chamber was adjusted to 750℃. An acetylene / argon mixture with 80% argon and 20% acetylene was then introduced for carbon vapor deposition. After completion, the carbon was sieved to obtain a silicon-carbon composite material. The volumetric particle size distribution (Dv50) of the silicon-carbon composite material was 2 μm.

[0307] Preparation of negative electrode layer

[0308] The silicon-carbon composite material, polyvinylidene fluoride (PVDF) as the negative electrode binder, and vapor-grown carbon fiber (VGCF) as the negative electrode conductive agent were uniformly dispersed in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel current collector and baked in an oven to remove the solvent. Finally, it was cut to a suitable size and electrode tabs were welded to obtain the negative electrode layer. The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 0.9 mAh / cm². 2 The NP ratio of the solid-state battery cell is 0.3. Based on the total mass of the negative electrode active material layer as 100%, the mass fraction of Si in the negative electrode active material layer is 15.4%.

[0309] Example 11

[0310] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0311] Preparation of silicon-carbon composite materials

[0312] Asphalt was used as a coating layer to coat clean, dry coconut shell granules, with a coating thickness of 0.5 μm. The mixture was then placed in a box furnace and heated to 700 °C under a nitrogen atmosphere for 8 hours to obtain a carbon material intermediate. The obtained carbon material intermediate was mixed with potassium hydroxide at a mass ratio of 1:3.5, and then placed in a box furnace and heated to 800 °C under a nitrogen atmosphere for 6 hours. The material was then removed and mixed thoroughly in a 0.1 mol / L hydrochloric acid aqueous solution to remove residual potassium hydroxide, followed by heating and drying to obtain porous carbon. The total pore area of ​​the outer region of the porous carbon was 20 × 10⁻⁶. 4 cm 2 / g, the total pore area of ​​the internal region is 0.4×10 4 cm 2 / g. Porous carbon was placed in the vapor deposition chamber of a rotary kiln, and argon gas was introduced to replace the air. The temperature of the vapor deposition chamber was then heated to 500℃, and a silane / argon mixture with an argon gas fraction of 70% and a silane volume fraction of 30% was introduced while maintaining a slightly positive pressure inside the furnace for silicon vapor deposition. The silane / argon mixture was then stopped, and the temperature of the vapor deposition chamber was adjusted to 750℃. An acetylene / argon mixture with an argon gas fraction of 80% and an acetylene volume fraction of 20% was then introduced for carbon vapor deposition. After completion, the carbon was obtained by sieving. The silicon-carbon composite material had a volume distribution particle size (Dv50) of 2 μm.

[0313] Preparation of negative electrode layer

[0314] The silicon-carbon composite material, polyvinylidene fluoride (PVDF) as the negative electrode binder, and vapor-grown carbon fiber (VGCF) as the negative electrode conductive agent were uniformly dispersed in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel current collector and baked in an oven to remove the solvent. Finally, it was cut to a suitable size and electrode tabs were welded to obtain the negative electrode layer. The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 0.9 mAh / cm². 2 The NP ratio of the solid-state battery cell is 0.3. Taking the total mass of the negative electrode active material layer as 100%, the mass fraction of Si in the negative electrode active material layer is 42%.

[0315] Example 12

[0316] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0317] Preparation of silicon-carbon composite materials

[0318] Asphalt was used as a coating layer to coat clean, dry coconut shell granules, with a coating thickness of 0.5 μm. The granules were then placed in a box furnace and heated to 700 °C under a nitrogen atmosphere for 8 hours to obtain a carbon material intermediate. The obtained carbon material intermediate was mixed with potassium hydroxide at a mass ratio of 1:4, and then placed in a box furnace and heated to 800 °C under a nitrogen atmosphere for 6 hours. The material was then removed and mixed thoroughly in a 0.1 mol / L hydrochloric acid aqueous solution to remove residual potassium hydroxide, followed by heating and drying to obtain porous carbon. The total pore area of ​​the outer region of the porous carbon was 30 × 10⁻⁶. 4 cm 2 / g, the total pore area of ​​the internal region is 3×10 4 cm 2 / g. Porous carbon was placed in the vapor deposition chamber of a rotary kiln, and argon gas was introduced to replace the air. The temperature of the vapor deposition chamber was then heated to 500℃, and a silane / argon mixture with an argon gas fraction of 70% and a silane volume fraction of 30% was introduced while maintaining a slightly positive pressure inside the furnace for silicon vapor deposition. The silane / argon mixture was then stopped, and the temperature of the vapor deposition chamber was adjusted to 750℃. An acetylene / argon mixture with an argon gas fraction of 80% and an acetylene volume fraction of 20% was then introduced for carbon vapor deposition. After completion, the carbon was obtained by sieving. The silicon-carbon composite material had a volume distribution particle size (Dv50) of 2 μm.

[0319] Preparation of negative electrode layer

[0320] The silicon-carbon composite material, polyvinylidene fluoride (PVDF) as the negative electrode binder, and vapor-grown carbon fiber (VGCF) as the negative electrode conductive agent were uniformly dispersed in deionized water at a solid mass ratio of 97:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a stainless steel current collector and baked in an oven to remove the solvent. Finally, it was cut to a suitable size and electrode tabs were welded to obtain the negative electrode layer. The parameters of the negative electrode active material layer were adjusted to achieve a negative electrode capacity of 0.9 mAh / cm². 2 The NP ratio of the solid-state battery cell is 0.3. Taking the total mass of the negative electrode active material layer as 100%, the mass fraction of Si in the negative electrode active material layer is 51%.

[0321] Table 2

[0322] The test results above show that with a fixed NP ratio, by further adjusting the total pore area of ​​the outer region of the porous carbon and the mass fraction of Si in the negative electrode active material layer, the solid-state battery cell can have higher initial coulombic efficiency, better cycle performance, and better rate performance.

[0323] Example 1-1

[0324] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0325] The heat treatment parameters were adjusted so that the porosity of the negative electrode active material layer after hot pressing was 10%.

[0326] Examples 1-2

[0327] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0328] The heat treatment parameters were adjusted so that the porosity of the negative electrode active material layer after hot pressing was 20%.

[0329] Examples 1-3

[0330] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 6.

[0331] The heat treatment parameters were adjusted so that the porosity of the negative electrode active material layer after hot pressing was 25%.

[0332] Table 3

[0333] The test results above show that further adjusting the porosity of the negative electrode active material layer is beneficial to improving the cycle performance and rate performance of solid-state battery cells.

[0334] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this disclosure are included within the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included within the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A solid-state battery cell, comprising a negative electrode layer, an electrolyte layer, and a positive electrode layer, wherein the electrolyte layer is located between the negative electrode layer and the positive electrode layer, wherein, The negative electrode layer includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon-based material located in the pores of the porous carbon. The region formed by extending from the outer surface of the porous carbon particles to the interior of the particles at a distance of 0.5 times the length between any point on the outer surface of the particles and the particle core is denoted as the outer region of the porous carbon. The region inside the outer region of the porous carbon is denoted as the inner region of the porous carbon. The total pore area of ​​the inner region of the porous carbon is 0%-10% of the total pore area of ​​the outer region of the porous carbon. The NP ratio of the solid-state battery cell is greater than 0 and less than 1. The NP ratio is the ratio of the unit area capacity of the negative electrode to the unit area capacity of the positive electrode.

2. The solid-state battery cell according to claim 1, wherein, The total pore area of ​​the internal region of the porous carbon is 0%-2% of the total pore area of ​​the external region of the porous carbon.

3. The solid-state battery cell according to any one of claims 1-2, wherein, The total pore area of ​​the outer region of the porous carbon is 1×10⁻⁶. 4 cm 2 / g to 30×10 4 cm 2 / g; and / or, The total pore area of the internal region of the porous carbon is 0 to 3 x 10 4 cm 2 / g.

4. The solid-state battery cell according to claim 3, wherein, The total pore area of ​​the outer region of the porous carbon is 1×10⁻⁶. 4 cm 2 / g to 10×10 4 cm 2 / g; and / or, The total pore area of ​​the internal region of the porous carbon is 0.

5. The solid-state battery cell according to any one of claims 1-4, wherein, With the total mass of the negative electrode active material layer as 100%, the mass fraction of Si element in the negative electrode active material layer is greater than or equal to 5% and less than 90%.

6. The solid-state battery cell according to any one of claims 1-5, wherein, The mass fraction of Si element in the negative electrode active material layer is 5% to 50%, and the NP ratio of the solid-state battery cell is 0.01-0.

5.

7. The solid-state battery cell according to any one of claims 1-5, wherein, The mass fraction of Si element in the negative electrode active material layer is 20% to 50%, and the NP ratio of the solid-state battery cell is 0.5-0.

9.

8. The solid-state battery cell according to any one of claims 1-7, wherein, The solid-state battery cell operates under an external pressure of less than 10 MPa.

9. The solid-state battery cell according to any one of claims 1-8, wherein, The porosity of the negative electrode active material layer is 10%-20%; and / or, The thickness of the negative electrode active material layer is 2μm-35μm.

10. The solid-state battery cell according to claim 9, wherein, The thickness of the negative electrode active material layer is 11μm-35μm.

11. The solid-state battery cell according to any one of claims 1-10, wherein, The silicon-based material includes one or more of silicon, silicon carbon, silicon oxide, silicon nitride, and silicon alloy materials.

12. The solid-state battery cell according to any one of claims 1-11, wherein, The silicon-carbon composite material further includes a coating layer located on at least a portion of the surface of the porous carbon, and the coating layer includes one or more of carbon materials, metals, and conductive polymers.

13. The solid-state battery cell according to any one of claims 1-12, wherein, The volumetric particle size distribution (Dv50) of the silicon-carbon composite material is 500 nm to 20 μm.

14. The solid-state battery cell according to claim 13, wherein, The volumetric particle size Dv50 of the silicon-carbon composite material is 2μm-5μm.

15. The solid-state battery cell according to any one of claims 1-14, wherein, The negative electrode active material layer also includes metal particles, which are located between the silicon-based material particles and can form an alloy or solid solution with lithium.

16. The solid-state battery cell according to claim 15, wherein, The metal particles include one or more of Ag, Mg, Au, Cu, and Ti; and / or, The mass of the metal particles is 1%-10% of the mass of the silicon-based material; and / or, The volume distribution particle size Dv50 of the metal particles is 20nm-100nm.

17. The solid-state battery cell according to any one of claims 1-16, wherein, The negative electrode active material layer further includes a negative electrode conductive agent, which includes one or more of linear conductive agents, planar conductive agents, and spherical conductive agents; and / or, The negative electrode active material layer further includes a solid electrolyte material, which includes one or more of sulfide solid electrolyte materials, halide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials; and / or, The negative electrode active material layer also includes a negative electrode binder.

18. The solid-state battery cell according to any one of claims 1-17, wherein, The negative electrode layer also includes a lithium-based metal layer located between the negative electrode current collector and the negative electrode active material layer.

19. The solid-state battery cell according to claim 18, wherein, The lithium-based metal layer comprises lithium or a lithium alloy; and / or, The thickness of the lithium-based metal layer is 0.5μm-50μm.

20. The solid-state battery cell according to any one of claims 1-19, wherein, The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector. The positive electrode active material layer includes a solid electrolyte material and a positive electrode active material. The positive electrode active material includes one or more of lithium transition metal oxides and their modified materials, lithium phosphates and their modified materials, lithium titanate, lithium niobate, sulfur, selenium, and tellurium. The solid electrolyte material includes one or more of sulfide solid electrolyte materials, halide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials; and / or, The electrolyte layer includes one or more of the following: sulfide solid electrolyte material, halide solid electrolyte material, oxide solid electrolyte material, and polymer solid electrolyte material.

21. A method for preparing a solid-state battery cell, comprising the following steps: providing a negative electrode layer, an electrolyte layer, and a positive electrode layer; assembling the negative electrode layer, the electrolyte layer, and the positive electrode layer; and pressing them to obtain a solid-state battery cell. The electrolyte layer is located between the negative electrode layer and the positive electrode layer. The negative electrode layer includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon-based material located in the pores of the porous carbon. The region formed by extending from the outer surface of the porous carbon particles to the interior of the particles at a distance 0.5 times the length between any point on the outer surface of the particles and the core of the particles is denoted as the outer region of the porous carbon. The region inside the outer region of the porous carbon is denoted as the inner region of the porous carbon. The total pore area of ​​the inner region of the porous carbon is 0%-10% of the total pore area of ​​the outer region of the porous carbon. The NP ratio of the solid-state battery cell is greater than 0 and less than 1, where the NP ratio is the ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area.

22. A battery device comprising a plurality of solid-state battery cells as described in any one of claims 1-20.

23. An electrical device comprising a solid-state battery cell as described in any one of claims 1-20 or a battery device as described in claim 22.

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