Pole piece and preparation method thereof, solid-state battery and power utilization device

Abstract

The invention belongs to the technical field of batteries, and discloses a pole piece and a preparation method thereof, a solid-state battery and a power utilization device. The pole piece comprises a current collector and an active material layer arranged on at least one side of the current collector, and the active material layer comprises a solid electrolyte; wherein in the direction far away from the current collector, the mass percentage content of the solid electrolyte in the active material layer is continuously reduced. According to the pole piece, the dosage of the solid electrolyte is reduced on the whole, and the side reaction between the solid electrolyte and the active material in the pole piece is reduced while the capacity of the pole piece is ensured. Therefore, the pole piece has excellent capacity performance, and also has excellent cycle life.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to electrode sheets and their preparation methods, solid-state batteries, and electrical devices. Background Technology

[0002] Solid-state batteries use solid electrolytes instead of liquid electrolytes. Compared to liquid batteries, they reduce the use of electrolytes and separators, avoiding safety issues such as electrolyte leakage. Furthermore, because solid-state batteries incorporate solid electrolyte materials into the positive and negative electrodes, they achieve higher energy density than batteries using organic electrolytes. However, excessive solid electrolyte within the electrodes can cause side reactions with the active materials in the electrodes. Since the solid electrolyte is an inactive component, it can reduce the energy density and affect the battery's cycle life to some extent. Therefore, for solid-state batteries, the distribution of the solid electrolyte within the electrodes is a crucial parameter affecting battery performance. Improving battery performance by precisely controlling the content and distribution of solid electrolyte within the electrodes remains one of the current challenges. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention proposes an electrode, a method for preparing the same, a solid-state battery, and an electrical device. This electrode exhibits fewer side reactions between the active material and the electrolyte, and the solid-state battery using the electrode of this application demonstrates excellent energy density and cycle life.

[0004] A first aspect of this application provides an electrode comprising: a current collector and an active material layer disposed on at least one side of the current collector, the active material layer comprising a solid electrolyte; wherein, in a direction away from the current collector, the mass percentage content of the solid electrolyte in the active material layer continuously decreases.

[0005] In the electrode of this application, the mass percentage of solid electrolyte in the active material layer continuously decreases from the side closer to the current collector to the side farther away from the current collector. Specifically, on the side closer to the current collector, the electrode reaction kinetics are poor. The higher content of solid electrolyte, acting as a channel for ion transport, helps to enhance ion transport, thereby compensating for the insufficient reaction kinetics in this region. On the side of the electrode farther from the current collector, the electrode reaction kinetics are high, meaning the active material itself reacts faster. Therefore, a lower solid electrolyte content can match the stronger reaction kinetics in this region. Thus, the overall amount of solid electrolyte is reduced. While maintaining the electrode capacity, it reduces side reactions between the solid electrolyte and the active material inside the electrode. This not only does not affect the charge / discharge rate performance of the battery, but also reduces the battery production cost due to the reduced solid electrolyte content. It also reduces side reactions between the solid electrolyte and the active material in the early stages of battery cycling, resulting in better mass energy density and cycle life.

[0006] In some embodiments, at a thickness h1 in the active material layer of the electrode, the mass percentage y of the solid electrolyte in the active material layer satisfies: y = x1 - h1(x1 - x2) / h; Where x1 represents the mass percentage of the solid electrolyte in the active material layer at the position where the thickness is 0; x2 represents the mass percentage of the solid electrolyte in the active material layer at a position with thickness h; h is the total thickness of the active material layer; The thickness is the distance between the corresponding position in the active material layer and the current collector.

[0007] In some embodiments, the electrode satisfies at least one of the following conditions: x1 is 10%~50%; x2 is 0%~10%; 0≤h 1≤h.

[0008] In some embodiments, the electrode satisfies at least one of the following conditions: The electrode is a positive electrode, with x1 being 10%~25%; and / or x2 being 0%~5%; The electrode is a negative electrode, with x1 being 20%~50%; and / or x2 being 0%~10%. This helps to further ensure the performance of the electrode.

[0009] In some embodiments, the solid electrolyte includes LPSCl, Li3PS4, and Li7P3S. 11 Li 10 GeP2S 12 It contains at least one of the following: silver-germanium sulfide electrolyte, Li₂InCl₆, and Li₂ZrCl₆. This enables efficient and rapid lithium-ion transport, supporting the high-rate performance of the battery.

[0010] In some embodiments, the electrode is a positive electrode. Based on the total mass of the active material layer, the active material layer comprises: 80-90 parts by weight of positive electrode active material; 5-15 parts by weight of the solid electrolyte; 0.5-2 parts by weight of positive electrode conductive agent; 0.5-1.5 parts by weight of a first binder, the first binder comprising at least one of FKM, PIB, SEBS, and SBS; and 0.5-2 parts by weight of a second binder, the second binder comprising at least one of NBR, HNBR, and SBR. This helps to improve the overall performance of the electrode.

[0011] In some embodiments, the electrode is a negative electrode, and based on the total mass of the active material layer, the active material layer comprises: 65-85 parts by weight of negative electrode active material; 10-30 parts by weight of the solid electrolyte; 0.5-2 parts by weight of negative electrode conductive agent; 0.5-1.5 parts by weight of the first binder; and 0.5-2 parts by weight of the second binder.

[0012] In some embodiments, the electrode satisfies at least one of the following conditions: The surface peel force between the current collector and the active material layer is 2N / m to 10N / m; The current collector includes a carbon-coated metal foil.

[0013] In a second aspect of this application, a method for preparing the aforementioned electrode is provided, comprising: The active material layer raw material, the first solvent, and the second solvent are mixed to obtain a slurry. The active material layer raw material includes an active material, a solid electrolyte, a first binder, and a second binder. The slurry is applied to at least one surface of the substrate to form a slurry layer on the substrate; The slurry layer is subjected to a first baking, a second baking, and a third baking in sequence, wherein the temperature of the first baking is lower than the temperature of the second baking and the temperature of the third baking, to obtain an active material layer; At least one surface of the current collector is bonded to the surface of the active material layer away from the substrate, and the substrate is then peeled off to obtain the electrode sheet; Wherein, the saturated vapor pressure of the first solvent is higher than that of the second solvent, and the boiling point of the first solvent is lower than that of the second solvent.

[0014] Therefore, this method has simple preparation steps, is convenient to operate, and produces electrodes with excellent performance.

[0015] In some embodiments, the electrode satisfies at least one of the following conditions: The first solvent has a saturated vapor pressure of 0.5 kPa to 3 kPa at 25°C and a boiling point of 60°C to 100°C. The second solvent has a saturated vapor pressure of 0.05 kPa to 0.15 kPa at 25°C and a boiling point of 140°C to 220°C. Under the same conditions, the solubility of the first adhesive in the first solvent is greater than the solubility of the second adhesive in the first solvent; Under the same conditions, the solubility of the first adhesive in the first solvent is greater than the solubility of the first adhesive in the second solvent; The first solvent includes at least one of ethyl acetate, isopropyl acetate, ethyl isopropionate, heptane, cyclohexane, hexane, and ethylene glycol dimethyl ether; The second solvent includes at least one of isopentyl isovalerate, amyl valerate, hexyl octanoate, benzyl acetate, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and anisole.

[0016] In some embodiments, the electrode satisfies at least one of the following conditions: The first baking temperature is 60℃~100℃, and the first baking time is 1min~10min; The second baking temperature is 140℃~180℃, and the second baking time is 1min~10min; The temperature of the third baking is 140℃~180℃, and the baking time is 2h~12h.

[0017] In some embodiments, the electrode satisfies at least one of the following conditions: The surface peel force between the substrate and the active material layer is 0.1 N / m to 1 N / m; The substrate includes at least one of release foil and release film.

[0018] A third aspect of this application proposes a solid-state battery, including the aforementioned electrode. Therefore, this solid-state battery exhibits excellent capacity performance and cycle life.

[0019] A fourth aspect of this application provides an electrical device comprising the aforementioned electrode or the aforementioned solid-state battery. This electrical device exhibits excellent energy density and cycle life. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of an electrode sheet according to an embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the electrode preparation process according to an embodiment of this application. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] This application is based on the inventor's following discoveries and understandings: In related technologies, during charging and discharging, the electrochemical reaction kinetics of the positive and negative electrodes in solid-state batteries exhibit a significant gradient change along the thickness direction. This is especially true at high rates, where the reaction kinetics of the active material layer near the current collector are poor, while those further away are high. This characteristic significantly affects the utilization rate of the battery's active materials, rate performance, and cycle stability. Addressing the aforementioned electrode reaction kinetics characteristics of solid-state batteries and the aforementioned effect of excessive solid electrolyte in the electrodes on battery performance, the inventors considered designing an electrode with a continuously distributed electrolyte and high areal capacity. This allows the electrolyte to continuously change within the electrode, thereby improving the electrochemical performance of the solid-state battery.

[0024] In view of this, the first aspect of this application proposes an electrode, referring to Figure 1 It includes: a current collector 1 and an active material layer 2 disposed on at least one side of the current collector, wherein the active material layer includes a solid electrolyte 2-1. The mass percentage of the solid electrolyte in the active material layer continuously decreases in the direction away from the current collector.

[0025] In the electrode of this application, the mass percentage of solid electrolyte in the active material layer continuously decreases from the side closer to the current collector to the side farther away from the current collector. Specifically, on the side closer to the current collector, the electrode reaction kinetics are poor. The higher content of solid electrolyte, acting as a channel for ion transport, helps to enhance ion transport, thereby compensating for the insufficient reaction kinetics in this region. On the side of the electrode farther from the current collector, the electrode reaction kinetics are high, meaning the active material itself reacts faster. Therefore, a lower solid electrolyte content can match the stronger reaction kinetics in this region. Thus, the overall amount of solid electrolyte is reduced. While maintaining the electrode capacity, it reduces side reactions between the solid electrolyte and the active material inside the electrode. This not only does not affect the charge / discharge rate performance of the battery, but also reduces the battery production cost due to the reduced solid electrolyte content. It also reduces side reactions between the solid electrolyte and the active material in the early stages of battery cycling, resulting in better mass energy density and cycle life.

[0026] In this paper, the continuous decrease in the mass percentage of solid electrolyte in the active material layer in the direction away from the current collector means that the mass percentage curve of solid electrolyte in the active material layer decreases continuously and smoothly in the direction away from the current collector, without abrupt changes or inflection points. In other words, the continuous distribution of solid electrolyte within the active material layer does not have any obvious interface layer. Therefore, not only is there no obvious interface layer within the active material layer as in multilayer coating schemes, thus avoiding significant interfacial impedance, but the continuous distribution of solid electrolyte also avoids abrupt changes and inflection points in mass distribution, ensuring the optimal distribution of electrolyte within the active material layer.

[0027] In this paper, the mass percentage of solid electrolyte in the active material layer refers to the mass percentage of solid electrolyte in a unit mass of the active material layer at a corresponding thickness position. This can be detected by the following method: Prepare slices of the electrode along its thickness direction, perform SEM and elemental analysis. SEM can measure the thickness, and elemental analysis can obtain the mass percentage of solid electrolyte at the corresponding position, thus obtaining the mass percentage of solid electrolyte at different thicknesses of the active material layer.

[0028] Furthermore, refer to Figure 1 The electrode in this application has a thickness of h1 ( Figure 1 At the position indicated by the dashed line, the mass percentage y of the solid electrolyte in the active material layer satisfies: y = x1 - h1(x1 - x2) / h. Here, x1 represents the mass percentage of the solid electrolyte in the active material layer at a thickness of 0 (i.e., the surface of the active material layer near the current collector); x2 represents the mass percentage of the solid electrolyte in the active material layer at a thickness of h; h is the total thickness of the active material layer; and the thickness is the distance between the corresponding position in the active material layer and the current collector. By satisfying the above formula, the mass percentage of the solid electrolyte in the active material layer decreases linearly away from the current collector, resulting in a smoother transition. Consequently, the performance transition of the electrode is smoother, without abrupt changes, and the matching is better, which can further improve the battery's mass energy density and cycle life.

[0029] In some embodiments, 0 ≤ h1 ≤ h. Therefore, the above formula requirements are satisfied throughout the entire thickness range of the active material layer, which further improves the overall performance of the solid-state battery.

[0030] In some embodiments, x1 is 10% to 50%. Specifically, x1 can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any combination thereof. Having the mass percentage of solid electrolyte near the current collector within the above range greatly enhances ion transport in that region, ensuring strong reaction kinetics. Simultaneously, it avoids the problems of excessively high solid electrolyte content leading to increased side reactions, thus preventing increased costs or impact on electrode capacity.

[0031] In some embodiments, x2 is 0% to 10%. Specifically, x2 can be 0%, 2%, 4%, 6%, 8%, 10%, or any combination thereof. Maintaining the mass percentage of the solid electrolyte away from the current collector within the above range ensures ion transport in that region, thereby further guaranteeing the reaction kinetics in that region. Simultaneously, it reduces the amount of solid electrolyte used, minimizing side reactions between the solid electrolyte and the positive and negative electrode active materials during the initial stages of battery cycling, thus enhancing battery performance while reducing battery cost.

[0032] Specifically, when the electrode is a positive electrode, x1 is 10%~25% (specifically, x1 can be 10%, 15%, 20%, 25%, or any two of these ranges), and x2 is 0%~5% (specifically, x2 can be 0%, 2%, 5%, or any two of these ranges). When the electrode is a negative electrode, x1 is 20%~50% (specifically, x1 can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any two of these ranges), and x2 is 0%~10% (specifically, x2 can be 0%, 2%, 5%, 8%, 10%, or any two of these ranges). Therefore, better matching of the positive and negative electrode requirements improves the overall performance of the battery.

[0033] In some embodiments, the solid electrolyte includes LPSCl, Li3PS4, and Li7P3S. 11 Li 10 GeP2S 12 At least one of the following: silver-germanium sulfide electrolyte, Li₂InCl₆, and Li₂ZrCl₆. These solid electrolytes have high conductivity, are less prone to side reactions, and are beneficial for improving battery cycle life and safety. Among them, LPSCl has particularly high conductivity (up to 10⁻⁶ at room temperature). -2 (S / cm) enables efficient and rapid lithium-ion transport, supporting high-rate performance of the battery. Simultaneously, its stable voltage range covers the operating potentials of common positive electrodes (such as ternary materials) and negative electrodes (such as graphite), minimizing side reactions with the electrodes and further improving battery cycle life and safety.

[0034] In some embodiments, the active material layer includes a solid electrolyte and an active material ( Figure 1 The components include 2-2) conductive agents and binders. This ensures not only the electrochemical performance of the electrode but also its structural stability.

[0035] In some embodiments, the electrode is a positive electrode, and based on the total mass of the active material layer, the active material layer includes: 80-90 parts by weight of positive electrode active material; 5-15 parts by weight of the solid electrolyte; 0.5-2 parts by weight of positive electrode conductive agent; 0.5-1.5 parts by weight of first binder; and 0.5-2 parts by weight of second binder.

[0036] For example, the positive electrode active material can be in the range of 80 parts by weight, 82 parts by weight, 85 parts by weight, 88 parts by weight, 90 parts by weight, or any two of these ranges. The above-mentioned parts by weight of positive electrode active material ensure that the electrode has high capacity performance.

[0037] For example, the solid electrolyte can be in the range of 5 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight, 15 parts by weight, or any two of these ranges. The solid electrolyte in the above-mentioned weight proportions can effectively improve ion transport efficiency.

[0038] For example, the positive electrode conductive agent can be 0.5 parts by weight, 0.8 parts by weight, 1.0 parts by weight, 1.2 parts by weight, 1.5 parts by weight, 1.8 parts by weight, 2.0 parts by weight, or any combination thereof. The above-mentioned parts by weight of positive electrode conductive agent help to build an electron transport network, improve the rate performance of the battery, and avoid insufficient capacity utilization of the positive electrode active material due to poor electron conductivity.

[0039] For example, the first binder can be in the range of 0.5 parts by weight, 0.7 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.2 parts by weight, 1.5 parts by weight, or any two of these amounts; the second binder can be in the range of 0.5 parts by weight, 0.7 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.2 parts by weight, 1.5 parts by weight, 1.7 parts by weight, 2 parts by weight, or any two of these amounts. This allows the positive electrode active material, solid electrolyte, and positive electrode conductive agent to be bonded together and fixed on the current collector, preventing the active material layer from detaching from the current collector surface and preventing the active material layer from pulverizing. In some embodiments, the positive electrode conductive agent includes at least one selected from SuperP, carbon black, carbon fiber, graphene, and carbon nanotubes. The aforementioned positive electrode conductive agent can form dense conductive contact points between the active material particles, which helps to reduce the internal resistance of the electrode, improve electron transport efficiency, and thus enhance the rate performance of the battery.

[0040] In some embodiments, the positive electrode active material includes ternary positive electrode active materials (lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, etc.), lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium-rich manganese-based materials, etc. Specifically, the active material can be a ternary positive electrode active material, including but not limited to NCM111, NCM532, etc. NCM111 refers to a ternary material with a molar ratio of nickel, cobalt, and manganese of 1:1:1 (i.e., Ni...).1 / 3 Co 1 / 3 Mn 1 / 3 O2). NCM532 refers to a ternary material with a nickel, cobalt, and manganese molar ratio of 5:3:2 (i.e., Ni). 0.5 Co 0.3 Mn 0.2 O2). NCM111 and NCM532 strike a good balance between energy density, structural stability and cost.

[0041] In some embodiments, the positive current collector can be a metal current collector or a composite current collector. For example, metal current collectors include, but are not limited to, aluminum foil current collectors, carbon-coated metal foils, etc.; composite current collectors may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0042] In some embodiments, the first binder includes at least one selected from FKM (fluororubber), PIB (polyisobutylene), SEBS (hydrogenated styrene-butadiene block copolymer), and SBS (styrene-butadiene block copolymer). The aforementioned first binder helps improve the bonding performance between active material particles and between solid electrolyte particles, thereby improving the structural stability of the active material layer and effectively preventing the pulverization of the active material layer.

[0043] In some embodiments, the second binder includes at least one of NBR (nitrile butadiene rubber), HNBR (hydrogenated nitrile butadiene rubber), and SBR (styrene-butadiene rubber). The aforementioned second binder helps improve the adhesion between the active material and the current collector, thereby improving the structural stability of the electrode and preventing the active material layer from detaching.

[0044] In some embodiments, the electrode is a negative electrode, and based on the total mass of the active material layer, the active material layer comprises: 65-85 parts by weight of negative electrode active material; 10-30 parts by weight of the solid electrolyte; 0.5-2 parts by weight of negative electrode conductive agent; 0.5-1.5 parts by weight of the first binder; and 0.5-2 parts by weight of the second binder.

[0045] For example, the positive electrode active material can be 65 parts by weight, 68 parts by weight, 70 parts by weight, 72 parts by weight, 75 parts by weight, 78 parts by weight, 80 parts by weight, 82 parts by weight, 85 parts by weight, or any combination thereof. The above-mentioned parts by weight of negative electrode active material ensure that the electrode has high capacity performance.

[0046] For example, the solid electrolyte can be in the range of 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, or any two of these ranges. The solid electrolyte in the above-mentioned weight proportions can effectively improve ion transport efficiency.

[0047] For example, the negative electrode conductive agent can be in the range of 0.5 parts by weight, 0.8 parts by weight, 1.0 parts by weight, 1.2 parts by weight, 1.5 parts by weight, 1.8 parts by weight, 2.0 parts by weight, or any two of these ranges. The aforementioned parts by weight of the negative electrode conductive agent help to build an electron transport network, improve the rate performance of the battery, and avoid insufficient capacity utilization of the negative electrode active material due to poor electron conductivity.

[0048] For example, the first binder can be in the range of 0.5 parts by weight, 0.7 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.2 parts by weight, 1.5 parts by weight, or any two of these amounts; the second binder can be in the range of 0.5 parts by weight, 0.7 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.2 parts by weight, 1.5 parts by weight, 1.7 parts by weight, 2 parts by weight, or any two of these amounts. This allows the negative electrode active material, solid electrolyte, and negative electrode conductive agent to be bonded together and fixed on the current collector, preventing the active material layer from detaching from the current collector surface and preventing the active material layer from pulverizing. In some embodiments, the negative electrode active material can be graphite, porous carbon, porous silicon-carbon, silicon-oxygen materials, micron-sized silicon, etc. These negative electrode active materials possess excellent capacity performance and low cost, and different active materials can be selected according to actual needs.

[0049] In some embodiments, the negative electrode current collector may be a metal foil, a carbon-coated metal foil, etc. For example, the metal foil may be a copper foil.

[0050] In some embodiments, the negative electrode conductive agent, the first binder, and the second binder may be the same as the positive electrode conductive agent, the first binder, and the second binder described above, and will not be repeated here.

[0051] In some embodiments, the surface peel force between the current collector and the active material layer is 2 N / m to 10 N / m. This improves the structural stability of the electrode.

[0052] A second aspect of this application provides a method for preparing the aforementioned electrode sheet, comprising: S10: Mix the active material layer raw material, the first solvent, and the second solvent to obtain a slurry. The active material layer raw material includes an active material, a solid electrolyte, a first binder, and a second binder.

[0053] In this step, the active material, solid electrolyte, first binder, second binder, first solvent, and second solvent are mixed according to target weight parts to obtain a slurry. Specifically, the first binder is mainly dissolved in the first solvent, and the second binder is mainly dissolved in the second solvent.

[0054] The mixing method here is not limited. For example, the above raw materials and solvents can be placed in a mixer and stirred.

[0055] In some embodiments, the saturated vapor pressure of the first solvent is higher than that of the second solvent, and the boiling point of the first solvent is lower than that of the second solvent. The high saturated vapor pressure and low boiling point of the first solvent allow it to easily evaporate at lower baking temperatures. The first binder dissolved therein rises to the surface as the first solvent evaporates, simultaneously carrying the solid electrolyte to the surface, thereby facilitating the formation of an electrode with a continuous distribution of the solid electrolyte.

[0056] In some embodiments, under the same conditions, the solubility of the first binder in the first solvent is greater than that of the second binder in the first solvent. Therefore, the first binder primarily dissolves in the first solvent, which is more conducive to the rise of the solid electrolyte through the first binder during the evaporation of the first solvent, forming a continuous distribution.

[0057] In some embodiments, under the same conditions, the solubility of the first binder in the first solvent is greater than that in the second solvent. This facilitates the upward movement of the solid electrolyte via the first binder during the evaporation of the first solvent, resulting in a continuous distribution.

[0058] It should be noted that the above-mentioned "same conditions" refers to other environmental conditions such as temperature.

[0059] In some embodiments, the saturated vapor pressure (at 25°C) of the first solvent is 0.5 kPa to 3 kPa, specifically within the range of 0.5 kPa, 1 kPa, 1.5 kPa, 2 kPa, 2.5 kPa, 3 kPa, or any two thereof. The boiling point of the first solvent is 60°C to 100°C, specifically within the range of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any two thereof. Exemplarily, the first solvent may be at least one selected from ethyl acetate, isopropyl acetate, ethyl isopropionate, heptane, cyclohexane, hexane, and ethylene glycol dimethyl ether.

[0060] In some embodiments, the saturated vapor pressure (at 25°C) of the second solvent is 0.05 kPa to 0.15 kPa, specifically within the range of 0.05 kPa, 0.08 kPa, 0.1 kPa, 0.12 kPa, 0.15 kPa, or any two thereof. The boiling point of the second solvent is 140°C to 220°C, specifically within the range of 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 190°C, 200°C, 210°C, 220°C, or any two thereof. For example, the second solvent may be at least one of isoamyl isovalerate, amyl valerate, hexyl octanoate, benzyl acetate, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and anisole.

[0061] In some embodiments, the mass ratio of the first solvent to the second solvent is 1:(1~4). Specifically, it can be 1:1, 1:2, 1:3, 1:4, or any range between two of them. This ensures that the first binder, the second binder, and other active material layer raw materials are completely dissolved, and that all active material layer raw materials are uniformly dispersed in the slurry.

[0062] In some embodiments, the solid content of the slurry is 60% to 65%, specifically 60%, 61%, 62%, 63%, 64%, 65%, or any two of these ranges. A solid content within this range helps balance the slurry's flowability with its particle dispersibility, thereby further improving the uniformity of the active material layer. This essentially avoids particle agglomeration caused by excessively high solid content in the active material layer slurry, as well as reduced subsequent baking efficiency caused by excessively low solid content.

[0063] S20: The slurry is applied to at least one side surface of the substrate to form a slurry layer on the substrate.

[0064] In this step, the slurry prepared above is coated onto at least one surface of the substrate to form a slurry layer. At this point, the solid electrolyte in the slurry is uniformly distributed, as shown in the reference. Figure 2 .

[0065] There are no particular restrictions on the specific coating operation; different coating processes can be selected according to actual conditions.

[0066] S30: The slurry layer is subjected to a first baking, a second baking and a third baking in sequence, wherein the temperature of the first baking is lower than the temperature of the second baking and the temperature of the third baking, to obtain an active material layer.

[0067] In this step, during the first baking at a lower temperature, the first binder dissolved in the first solvent evaporates and floats to the surface, carrying the solid electrolyte to the surface as well. The solid electrolyte in the slurry layer is continuously distributed from the side closer to the substrate to the side farther from the substrate, with the solid electrolyte content continuously increasing. Next, a second baking is performed at a higher temperature. As the second solvent evaporates, the second binder dissolved in the second solvent is uniformly distributed. After the second baking, the distribution of the active material, solid electrolyte, first binder, and second binder is basically finalized. Specifically, the active material and second binder are uniformly distributed, while the first binder and solid electrolyte both exhibit continuously varying distribution patterns, with the content increasing from the side closer to the substrate to the side farther from the substrate. Finally, a third baking is performed at a higher temperature for drying and further shaping, resulting in a structurally stable active material layer, in which the mass percentage of solid electrolyte continuously varies, referring to... Figure 2 .

[0068] In some embodiments, the solid electrolyte in the electrode can float up with the first binder to form a continuous distribution, possibly because: the particle size of the solid electrolyte (about 0.2~0.5μm) is much smaller than the particles of the positive electrode active material (about 3~10μm), and before the solid electrolyte is densified, it is in a loose small particle state. Under the influence of gravity and the adsorption of the first binder, it floats up and eventually forms a continuous distribution of solid electrolyte.

[0069] In some embodiments, the temperature of the first baking is 60°C to 100°C, specifically 60°C, 70°C, 80°C, 90°C, 100°C, or any range between two of these. This temperature allows the first solvent to begin evaporating, indirectly causing the solid electrolyte to float to the surface, ultimately forming a continuously varying active material layer. Simultaneously, it prevents the simultaneous evaporation of the second solvent from affecting the distribution of the solid electrolyte.

[0070] In some embodiments, the first baking time is 1 min to 10 min, specifically 1 min, 2 min, 4 min, 6 min, 8 min, 10 min, or any range between two of these. This ensures that the buoyancy of the solid electrolyte remains within the target range, avoiding problems such as complete buoyancy due to excessively long baking times or insufficient buoyancy due to excessively short baking times.

[0071] In some embodiments, the second baking temperature is 140°C to 180°C, specifically 140°C, 150°C, 160°C, 170°C, 180°C, or any range between two of these. This temperature allows the second binder to distribute evenly as the second solvent evaporates, preventing it from depositing at the bottom during baking and thus affecting subsequent lamination processes.

[0072] In some embodiments, the second baking time is 1 to 10 minutes, specifically 1 minute, 2 minutes, 4 minutes, 6 minutes, 8 minutes, 10 minutes, or any combination thereof. This ensures a relatively uniform distribution of the second adhesive within the active material layer.

[0073] In some embodiments, the temperature of the third baking is 140°C to 180°C, specifically 140°C, 150°C, 160°C, 170°C, or any combination thereof. These temperatures essentially ensure the complete evaporation of the first and second solvents and guarantee the tight bonding between the raw materials in the active material layer, thereby obtaining a structurally stable active material layer.

[0074] In some embodiments, the third baking time is 2 h to 12 h, specifically 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, etc. This ensures that a structurally stable active material layer is obtained.

[0075] In some embodiments, the substrate includes a release aluminum foil and a release film. The aluminum foil has good heat resistance and can provide stable support during electrode coating and heating to prevent slurry deformation. The surface has a release coating, so the electrode can be easily peeled off from the aluminum foil after preparation and will not stick to the substrate.

[0076] S40: At least one side surface of the current collector is bonded to the surface of the active material layer away from the substrate, and the substrate is peeled off to obtain the electrode.

[0077] In this step, at least one surface of the current collector is laminated with the surface of the previously prepared active material layer away from the substrate. Specifically, the previously prepared sheet can be laminated with the side containing the active material layer to the current collector using a roller lathe with pressure parameters of 0.1~5MPa. Subsequently, the substrate is directly peeled off to obtain the electrode sheet. This method can perform lamination and transfer in a roll-to-roll manner to improve efficiency.

[0078] Specifically, the surface peel force between the substrate and the active material layer is 0.1 N / m to 1 N / m. This low peel force indicates that the slurry layer can be easily peeled from the substrate without damaging the structure of the active material layer. The surface peel force between the current collector and the active material layer is 2 N / m to 10 N / m, thereby improving the structural stability of the electrode.

[0079] In some embodiments, the current collector includes a carbon-coated metal foil. For example, it can be carbon-coated aluminum foil or carbon-coated copper foil. Different current collectors can be selected based on actual needs.

[0080] In some embodiments, the areal capacity of the electrode is 6 mAh / cm².2 ~8mAh / cm 2 Specifically, it can be 6mAh / cm 2 7mAh / cm 2 8 mAh / cm 2 Or a range between either or both. Therefore, the electrode in this application exhibits excellent capacity performance.

[0081] In a third aspect of this application, a solid-state battery is proposed, including the aforementioned electrode. Therefore, this solid-state battery exhibits excellent capacity performance and cycle life.

[0082] In some embodiments, the solid-state battery can be cylindrical, square, blade, or any other shape, and according to its outer packaging, it can be a hard-shell battery, a pouch battery, etc.

[0083] Typically, a solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte layer. The positive and negative electrodes are stacked alternately, and the solid electrolyte layer is disposed between adjacent positive and negative electrodes. During the charging and discharging process, active ions move back and forth between the positive and negative electrodes, inserting and extracting.

[0084] In a fourth aspect of this application, an electrical device is proposed. According to an embodiment of this application, the electrical device includes the aforementioned electrode or the aforementioned solid-state battery. This electrical device possesses excellent battery life and cycle life.

[0085] According to embodiments of this application, the specific type of electrical device is not particularly limited and can be any device that uses a solid-state battery as a power source or energy storage unit. As examples, electrical devices include, but are not limited to, 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.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, and so on.

[0086] It is understood that, in addition to the aforementioned electrode plates or solid-state batteries, the electrical device also includes other necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be elaborated here.

[0087] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0088] Example 1 Preparation of positive electrode sheet: Active material NCM811, LPSCl, conductive agent CNT, first binder FKM and second binder NBR are mixed in a mass ratio of 80:15:3:1:2 to obtain positive electrode raw material mixture; The first solvent, heptane, and the second solvent, amyl valerate, were mixed in a mass ratio of 1:2 and added to the above-mentioned cathode raw material mixture to obtain a cathode slurry with a solid content of 60%. The positive electrode slurry was coated onto the release aluminum foil, and the thickness of the scraper was adjusted to achieve an areal capacity of 6 mAh / cm². 2 The following baking steps are performed in sequence: baking at 60℃ for 2 minutes, baking at 140℃ for 2 minutes, and baking at 160℃ for 8 hours. Then, the side of the active material layer away from the release aluminum foil is laminated onto the carbon-coated aluminum foil current collector. The release aluminum foil is then peeled off to finally obtain a positive electrode with a continuous electrolyte distribution, where x1=25% and x2=5%.

[0089] Preparation of negative electrode sheet: Porous silicon carbon, electrolyte LPSCl, conductive agent VGCF, first binder FKM and second binder NBR are mixed in a mass ratio of 70:25:3:1:2 to obtain a negative electrode raw material mixture; The first solvent, heptane, and the second solvent, pentyl valerate, were added to the negative electrode raw material mixture in a mass ratio of 1:2 to obtain a negative electrode slurry with a solid content of 55%. The negative electrode slurry was coated onto release aluminum foil, and the thickness of the scraper was adjusted to achieve an areal capacity of 6.5 mAh / cm². 2 The baking process is carried out in sequence as follows: baking at 60°C for 2 minutes, baking at 140°C for 2 minutes, and baking at 160°C for 8 hours. Then, the side of the active material layer away from the release aluminum foil is laminated onto the carbon-coated copper foil current collector. The release aluminum foil is then peeled off to finally obtain a negative electrode sheet with continuous electrolyte distribution, where x1=40% and x2=10%.

[0090] Preparation of sulfide electrolyte layer: Li6PS5Cl electrolyte, nitrile rubber and xylene in a weight ratio of 97:3:80 were mixed by ball mill dispersion to prepare an electrolyte slurry with a solid content of 55.6wt%, which was then coated and dried to obtain Li6PS5Cl electrolyte layer. Solid-state battery preparation: The positive electrode, electrolyte layer and negative electrode prepared above are assembled to obtain an all-solid-state battery.

[0091] Example 2 Similar to Example 1, the main difference is that when preparing the positive electrode, it is first baked at 70°C for 4 minutes, then at 140°C for 1 minute, and finally at 180°C for 2 hours. In the end, x1=25% and x2=0% in the positive electrode.

[0092] When preparing the negative electrode, it is first baked at 70℃ for 4 minutes, then at 140℃ for 2 minutes, and finally at 180℃ for 2 hours. In the end, x1=50% and x2=0% in the negative electrode.

[0093] Example 3 Same as Example 1, the main difference is that the porous silicon carbon of the negative electrode, LPSCl electrolyte, VGCF conductive agent, first binder FKM and second binder NBR are mixed in a mass ratio of 80:15:3:1:2, and the final negative electrode contains x1=30% and x2=0%.

[0094] Example 4 Same as Example 1, the main difference being: the areal capacity of the positive electrode is 7 mAh / cm². 2 The surface capacity of the negative electrode is 7.7 mAh / cm². 2 .

[0095] Example 5: Same as Example 1, the main difference is that: the active material NCM811, electrolyte LPSCl, conductive agent CNT, first binder SEBS, and second binder HNBR in the positive electrode sheet are mixed in a mass ratio of 80:15:3:1:2, first baked at 80°C for 5 min, then baked at 160°C for 3 min, and finally baked at 180°C for 12 h, resulting in x1=25% and x2=5% in the final positive electrode; In the negative electrode, porous silicon carbon, LPSCl electrolyte, VGCF conductive agent, first binder SEBS, and second binder HNBR are mixed in a mass ratio of 70:25:3:1:2, and the final negative electrode contains x1=40% and x2=10%.

[0096] Example 6: Same as Example 1, the main difference is that: the negative electrode micron silicon, porous silicon carbon, LPSCl electrolyte, VGCF conductive agent, first binder FKM and second binder NBR are mixed in a mass ratio of 50:20:25:3:1:2, and the final negative electrode contains x1=40% and x2=10%.

[0097] Example 7 Similar to Example 1, the main difference is that: active material NCM811, LPSCl, conductive agent CNT, first binder FKM, and second binder NBR are mixed in a mass ratio of 85:9:3:1:2 to obtain a positive electrode raw material mixture. After baking at 70°C for 2 min, at 150°C for 3 min, and at 160°C for 8 h, a positive electrode sheet with continuous electrolyte distribution is obtained, where x1=16% and x2=2%.

[0098] Comparative Example 1 Same as Example 1, the main difference is: NCM811 active material, LPSCl electrolyte, CNT conductive agent, first binder FKM and second binder NBR are mixed in a mass ratio of 80:15:3:1:2 to obtain a positive electrode raw material mixture, and the second solvent is mixed with the positive electrode raw material mixture to obtain a positive electrode slurry; Porous silicon carbon, LPSCl electrolyte, VGCF conductive agent, FKM, and NBR are mixed in a mass ratio of 70:25:3:1:2 to obtain a negative electrode raw material mixture. The second solvent is then mixed with the negative electrode raw material mixture to obtain a negative electrode slurry.

[0099] Detection methods 1. The mass percentage content of solid electrolyte at different locations on the positive and negative electrode sheets prepared in Examples 1-7 was determined: The specific steps include: preparing slices of the electrode along its thickness direction, performing SEM and elemental content analysis tests. SEM can measure the thickness, and elemental content analysis can obtain the mass percentage of solid electrolyte at corresponding locations, thus obtaining the mass percentage of solid electrolyte at different thicknesses of the active material layer. In each embodiment, two different thickness locations (i.e., test site 1 and test site 2) are selected for testing of the positive and negative electrode sheets to obtain the measured y-values. The theoretical y-value is then calculated based on x1, x2, and the formula y=x1-h1(x1-x2) / h.

[0100] The test results are shown in Table 1 below: Table 1

[0101] As can be seen from the data in Table 1, the measured y value is basically consistent with the theoretical y value, indicating that the content distribution of solid electrolyte in the electrode of this application conforms to y=x1-h1(x1-x2) / h.

[0102] 2. Rate performance and cycle performance of the all-solid-state lithium-ion batteries prepared in Examples 1-7 and Comparative Example 1 were tested, and the test results are shown in Table 1.

[0103] (1) Rate performance: The test conditions are: 5MPa, 60℃. The specific steps are: using the solid-state batteries of the example and the comparative example as the test objects, under the voltage of 2.5V-4.25V, charge to 4.25V at a rate of 0.1C, let stand for 5 minutes, and then discharge to 2.5V at a rate of 0.1C. The discharge capacity at this time is the rate discharge performance of 0.1C. The same steps can be used to obtain the rate discharge performance of 0.3C, 0.5C, and 1C. (2) Cycling performance: Under the conditions of 10MPa and 30℃, the voltage range is 2.5~4.25V, 0.5C cycle, 300 cycles, and the capacity retention rate is measured. The capacity retention rate is expressed as the percentage of the actual battery discharge capacity after the 300th cycle at 30℃ relative to the discharge capacity of the first cycle.

[0104] Table 2

[0105] Note: In Table 2, " / " indicates a short circuit.

[0106] As can be seen from the data in Table 2 above, compared with Comparative Example 1, the rate performance and capacity retention of Examples 1-7 are significantly improved, indicating that the electrode of this application can significantly improve the rate performance and cycle performance of the battery.

[0107] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0108] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0109] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An electrode sheet, characterized in that, include: A current collector and an active material layer disposed on at least one side of the current collector, the active material layer comprising a solid electrolyte; In particular, the mass percentage of the solid electrolyte in the active material layer decreases continuously in the direction away from the current collector.

2. The electrode sheet according to claim 1, characterized in that, At a position with thickness h1, the mass percentage y of the solid electrolyte in the active material layer satisfies: y = x1 - h1(x1 - x2) / h; Where x1 represents the mass percentage of the solid electrolyte in the active material layer at the position where the thickness is 0; x2 represents the mass percentage of the solid electrolyte in the active material layer at a position with thickness h; h is the total thickness of the active material layer; The thickness is the distance between the corresponding position in the active material layer and the current collector.

3. The electrode sheet according to claim 2, characterized in that, At least one of the following conditions must be met: x1 is 10%~50%; x2 is 0%~10%; 0≤h 1≤h.

4. The electrode sheet according to claim 3, characterized in that, If any of the following conditions are met: The electrode is a positive electrode, with x1 being 10%~25%; and / or x2 being 0%~5%; The electrode is a negative electrode, with x1 being 20%~50%; and / or x2 being 0%~10%.

5. The electrode sheet according to claim 1, characterized in that, The solid electrolyte includes LPSCl, Li3PS4, and Li7P3S. 11 Li 10 GeP2S 12 At least one of the following: silver-germanium sulfide electrolyte, Li2InCl6, and Li2ZrCl6.

6. The electrode sheet according to claim 1, characterized in that, If any of the following conditions are met: (1) The electrode is a positive electrode, and based on the total mass of the active material layer, the active material layer comprises: 80-90 parts by weight of positive electrode active material; 5-15 parts by weight of the solid electrolyte; Positive electrode conductive agent 0.5~2 parts by weight; The first adhesive comprises 0.5 to 1.5 parts by weight, wherein the first adhesive comprises at least one of fluororubber, polyisobutylene, hydrogenated styrene-butadiene block copolymer, and styrene-butadiene block copolymer; The second adhesive is 0.5 to 2 parts by weight, and the second adhesive includes at least one of nitrile rubber, hydrogenated nitrile rubber, and styrene-butadiene rubber; (2) The electrode is a negative electrode, and based on the total mass of the active material layer, the active material layer comprises: 65-85 parts by weight of negative electrode active material; The solid electrolyte is 10-30 parts by weight; the negative electrode conductive agent is 0.5-2 parts by weight. The first adhesive is 0.5 to 1.5 parts by weight; The second adhesive is 0.5 to 2 parts by weight.

7. The electrode sheet according to claim 1, characterized in that, At least one of the following conditions must be met: The surface peel force between the current collector and the active material layer is 2N / m to 10N / m; The current collector includes a carbon-coated metal foil.

8. A method for preparing an electrode sheet according to any one of claims 1 to 7, characterized in that, include: The active material layer raw material, the first solvent, and the second solvent are mixed to obtain a slurry. The active material layer raw material includes an active material, a solid electrolyte, a first binder, and a second binder. The slurry is applied to at least one surface of the substrate to form a slurry layer on the substrate; The slurry layer is subjected to a first baking, a second baking, and a third baking in sequence, wherein the temperature of the first baking is lower than the temperature of the second baking and the temperature of the third baking, to obtain an active material layer; At least one surface of the current collector is bonded to the surface of the active material layer away from the substrate, and the substrate is then peeled off to obtain the electrode sheet; Wherein, the saturated vapor pressure of the first solvent is higher than that of the second solvent, and the boiling point of the first solvent is lower than that of the second solvent.

9. The method according to claim 8, characterized in that, At least one of the following conditions must be met: The first solvent has a saturated vapor pressure of 0.5 kPa to 3 kPa at 25°C and a boiling point of 60°C to 100°C. The second solvent has a saturated vapor pressure of 0.05 kPa to 0.15 kPa at 25°C and a boiling point of 140°C to 220°C. Under the same conditions, the solubility of the first adhesive in the first solvent is greater than the solubility of the second adhesive in the first solvent; Under the same conditions, the solubility of the first adhesive in the first solvent is greater than the solubility of the first adhesive in the second solvent; The first solvent includes at least one of ethyl acetate, isopropyl acetate, ethyl isopropionate, heptane, cyclohexane, hexane, and ethylene glycol dimethyl ether; The second solvent includes at least one of isopentyl isovalerate, amyl valerate, hexyl octanoate, benzyl acetate, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and anisole.

10. The method according to claim 8, characterized in that, At least one of the following conditions must be met: The first baking temperature is 60℃~100℃, and the first baking time is 1min~10min; The second baking temperature is 140℃~180℃, and the second baking time is 1min~10min; The temperature of the third baking is 140℃~180℃, and the baking time is 2h~12h.

11. The method according to claim 8, characterized in that, At least one of the following conditions must be met: The surface peel force between the substrate and the active material layer is 0.1 N / m to 1 N / m; The substrate includes at least one of release foil and release film.

12. A solid-state battery, characterized in that, The electrode includes any one of claims 1 to 7.

13. An electrical appliance, characterized in that, Includes the electrode sheet according to any one of claims 1 to 7 or the solid-state battery according to claim 12.

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