Composite conductive agent for positive electrode material, positive electrode material, method for preparing the same, positive electrode, sulfide all-solid-state battery, and power using device

Abstract

The application provides a composite conductive agent for a positive electrode material, a positive electrode material, a preparation method thereof, a positive electrode, a sulfide full-solid-state battery and an electric device, and relates to the technical field of solid-state lithium batteries.The composite conductive agent for the positive electrode material comprises a short-range conductive component and a long-range conductive component, and the short-range conductive component and the long-range conductive component are both one-dimensional fibrous conductive materials; wherein the specific surface area of the short-range conductive component is higher than the specific surface area of the long-range conductive component, and the average length of the short-range conductive component is smaller than the average length of the long-range conductive component. The one-dimensional short-range fibers with relatively high BET in the application are specially used for micro short-range electron injection, and the one-dimensional long-range fibers with low BET are specially used for macro long-range electron bridging, the synergistic decoupling of short-range high contact and long-range low side reaction is realized, and the technical contradiction that the activity and stability of the conductive agent cannot be compatible in a high-voltage sulfide system is solved.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium battery technology, and in particular to a composite conductive agent for cathode materials, cathode materials, their preparation methods, cathode electrodes, sulfide all-solid-state batteries, and electrical devices. Background Technology

[0002] Sulfide-based all-solid-state lithium batteries have become a key pathway for high-energy-density energy storage due to their high ionic conductivity and interface deformability; increasing the loading of positive electrode active material (area capacity ≥ 4 mAh / cm²) is crucial. 2 Thickness (≥100 μm) is an inevitable choice for improving energy density. Currently, liquid system approaches are often used, such as blending zero-dimensional (0D) conductive carbon black with one-dimensional (1D) long-range fibers (such as VGCF), relying on 0D point contacts and 1D bridging to synergistically construct a conductive network. However, the sulfide all-solid-state system has the following drawbacks: 1. The nanopores formed by 0D carbon black agglomeration cannot be filled by the solid electrolyte, becoming ion dead zones that hinder lithium-ion transport and exacerbating interfacial side reactions; 2. 0D and active material only have fragile point contacts, which are easily broken under charge-discharge volume breathing, leading to a cliff-like capacity decay in the early stages of cycling; 3. If 0D is abandoned and low specific surface area long-range fibers are used alone, the microscopic coating is insufficient, the initial contact impedance is high, and conventional blending is difficult to achieve electron / ion synergistic transport across the entire thickness of a thick electrode. Summary of the Invention

[0003] One of the objectives of this invention is to provide a composite conductive agent for positive electrode materials, so as to at least solve one of the technical problems existing in the prior art.

[0004] The second objective of this invention is to provide a positive electrode material.

[0005] The third objective of this invention is to provide a method for preparing a positive electrode material.

[0006] The fourth objective of this invention is to provide a positive electrode.

[0007] The fifth objective of this invention is to provide a sulfide all-solid-state battery.

[0008] The sixth objective of this invention is to provide an electrical device.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a composite conductive agent for positive electrode materials, comprising: a short-range conductive component and a long-range conductive component, wherein both the short-range conductive component and the long-range conductive component are one-dimensional fibrous conductive materials. The specific surface area of ​​the short-range conductive component is higher than that of the long-range conductive component, and the average length of the short-range conductive component is less than that of the long-range conductive component.

[0010] Furthermore, the short-range conductive component includes chopped carbon fibers and / or short carbon nanotubes. Preferably, the specific surface area of ​​the short-range conductive component is 30-150 m². 2 / g; Preferably, the short-range conductive component has a length of 1-5 μm and an aspect ratio greater than 8.

[0011] Furthermore, the long-range conductive component includes long carbon fibers or long carbon nanotubes. Preferably, the specific surface area of ​​the long-range conductive component is 5-30 m². 2 / g; Preferably, the length of the long-range conductive component is 6-30 μm, and the aspect ratio is greater than 40; Preferably, the mass ratio of the short-range conductive component to the long-range conductive component is 2-5:1.

[0012] In a second aspect, the present invention provides a positive electrode material, comprising: a positive electrode active material, a sulfide solid electrolyte, and the aforementioned composite conductive agent.

[0013] Furthermore, the amount of the composite conductive agent added is 0.5%-2.0% of the mass of the positive electrode active material.

[0014] Furthermore, the sulfide solid electrolyte includes Li6PS5Cl and Li 10 GeP2S 12 One or more of the Li2S-P2S5 system glass-ceramic electrolytes; Preferably, the sulfide solid electrolyte comprises a first-size electrolyte and a second-size electrolyte; wherein the D50 of the first-size electrolyte is smaller than the D50 of the second-size electrolyte. Preferably, the D50 of the first particle size electrolyte is 0.2-2 μm; Preferably, the D50 of the second particle size electrolyte is 2-10 μm; Preferably, the mass ratio of the first particle size electrolyte to the second particle size electrolyte is 0.25-1:1; Preferably, the positive electrode active material includes one or more of layered oxides, lithium-rich manganese-based materials, and spinel-type positive electrode materials; Preferably, the areal capacity of the positive electrode material is ≥5.0 mAh / cm². 2 .

[0015] Thirdly, the present invention provides a method for preparing a cathode material, comprising: (a) The positive electrode active material, the first particle size sulfide solid electrolyte, and the short-range conductive component are mixed to obtain a short-range conductive premix. (b) The long-range conductive component and the second-size sulfide solid electrolyte are mixed to obtain a long-range conductive premix. (c) The short-range conductive premix is ​​mixed with the long-range conductive premix to obtain the positive electrode material.

[0016] Furthermore, the mixing time in step (a) is 2-6 hours, and the rotation speed is 200-500 rpm; Preferably, the mixing time in step (b) is 10-30 minutes and the rotation speed is 300-600 rpm; Preferably, the mixing time in step (c) is 15-40 minutes and the rotation speed is 100-300 rpm; Preferably, the preparation method further includes: molding and rolling the mixture obtained in step c to obtain an areal capacity ≥ 5.0 mAh / cm³. 2 The positive electrode.

[0017] Fourthly, the present invention provides a positive electrode, comprising the aforementioned positive electrode material or a positive electrode material prepared by the aforementioned preparation method.

[0018] Fifthly, the present invention provides a sulfide all-solid-state battery, comprising: a negative electrode, a solid electrolyte membrane, and the aforementioned positive electrode.

[0019] In a sixth aspect, the present invention provides an electrical device comprising the aforementioned sulfide all-solid-state battery.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The composite conductive agent for cathode materials provided by this invention achieves dense coating and flexible anchoring on the surface of active materials through the high specific surface area and short size characteristics of the short-range component, effectively overcoming the problem of microscopic electronic contact failure caused by volume expansion or contraction in solid systems. At the same time, the low specific surface area and long-axis characteristics of the long-range component suppress interfacial side reactions between it and sulfide solid electrolytes, and construct a cross-scale bridging framework between particles, undertaking the functions of macroscopic electron transport and stress buffering. The two complement each other in space and function, fundamentally avoiding the ion insulation dead zone formed by zero-dimensional conductive agents in the solid environment and the resulting local concentration polarization and interfacial passivation. Thus, in the case of thick electrode configuration, it simultaneously ensures efficient ion transport and continuity of electronic pathways as well as the stability of the cycling structure. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the solid-state battery provided by the present invention; Figure 2 This is a schematic diagram of the electrical device provided by the present invention. Detailed Implementation

[0023] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The first aspect of this invention provides a composite conductive agent for positive electrode materials, comprising: a short-range conductive component and a long-range conductive component, both of which are one-dimensional fibrous conductive materials; wherein the specific surface area of ​​the short-range conductive component is higher than that of the long-range conductive component, and the average length of the short-range conductive component is less than that of the long-range conductive component. The short-range conductive component is anchored and coated on the surface of the positive electrode active material and the gaps between small-particle-size sulfide solid electrolytes, forming a short-range conductive network; the long-range conductive component is distributed in the gaps between composite particles, spanning multiple particles to construct a long-range conductive framework that penetrates the entire thickness of the electrode, and the short-range conductive network and the long-range conductive framework constitute a two-level, three-dimensional nested conductive network.

[0026] This invention provides a dual one-dimensional (short 1D + long 1D) composite conductive agent system, which eliminates 0D ineffective nanopores, constructs open mesoscopic pores that are conducive to solid electrolyte filling, and constructs an efficient electron transport path under the premise of strictly limiting the area of ​​side reactions with sulfide electrolytes, thereby reducing the initial polarization voltage and interfacial impedance of thick cathodes. This overcomes the technical defects of existing 0D conductive agents in solid systems, such as the formation of ion-insulating dead zones and the aggravation of interfacial side reactions by high specific surface areas.

[0027] This invention utilizes one-dimensional short-range fibers with relatively high specific surface area (BET) for microscopic short-range electron injection and one-dimensional long-range fibers with low BET for macroscopic long-range electron bridging, achieving a synergistic effect of high short-range contact and low long-range side reactions. Simultaneously, this invention constructs a dual-level network of microscopic dynamic anchoring and macroscopic static bridging. The short 1D (1D) network forms a microscopic anchoring layer on the surface of the active material, utilizing the flexibility of its one-dimensional morphology to tightly grip the surface of the active material, maintaining dynamic contact during the expansion and contraction of the cathode material's volume during charging and discharging. This ensures capacity stability in the early stages of cycling and solves the technical problem of 0D point contacts easily failing during solid-state volume changes, leading to low capacity in the early stages of cycling. The long 1D network serves as a long-range conductive channel, providing cross-particle bridging and stress buffering.

[0028] Specifically, the composite conductive agent for cathode materials provided by this invention consists of two types of one-dimensional (1D) conductive components, whose BET, morphology, and size strictly correspond to their electron / mechanical transport functions: (1) Regarding the short-range conductive component (high BET short 1D): One-dimensional short-range carbon nanofibers with relatively high BET (such as chopped CNTs or short carbon fibers) are used, characterized by their fine diameter and short length. Unlike traditional 0D carbon black, which easily forms dense chain-like agglomerates and internal ineffective nanopores, the overlapping of one-dimensional short-range fibers forms more open mesopores, allowing sulfide solid electrolyte particles to enter smoothly and fill uniformly, completely eliminating ion insulation dead zones. This component mainly undertakes the function of short-range electron transport, tightly coating the positive electrode active material particles through a high interfacial contact area; at the same time, utilizing the flexibility and tensile strength of its one-dimensional morphology, it anchors itself to the micro-unevennesses on the surface of the active material when the positive electrode particles expand / contract, maintaining micro-electron contact in dynamic cycling.

[0029] (2) Regarding the long-range conductive component (low BET long 1D): Low BET one-dimensional long-range conductive fibers (such as long-range VGCF or long CNFs) are used, characterized by a longitudinal dimension that is significantly larger than that of the short-range component. This component mainly undertakes the functions of long-range electron transport and macroscopic mechanical support. With its low specific surface area, it greatly reduces the ineffective contact area with the sulfide electrolyte and suppresses high-voltage interface side reactions. At the same time, as a three-dimensional macroscopic framework, it provides a bridging effect across multiple active materials and electrolyte particles, and as a stress buffer framework, it absorbs the mechanical stress generated by volume changes, bridging and connecting the dispersed short-range conductive network clusters to form a continuous electron transport channel that runs through the entire thickness of the thick electrode.

[0030] To further explain, this invention establishes a nested, interpenetrating network configuration of microscopic dynamic anchoring and macroscopic static bridging. Two types of one-dimensional conductive components construct a cohesive-external bi-level conductive network within the thick electrode: the short-range network is responsible for microscopic-scale surface anchoring and efficient electron injection; the long-range network is responsible for macroscopic-scale cross-particle bridging and low-loss electron transport. These two networks are spatially gradient-nested, which not only effectively reduces the overall conductive permeation threshold but also, through the synergistic dissipation of stress by short-range microscopic sliding anchoring and long-range macroscopic flexible bridging during charge-discharge volume breathing, eliminates the deep electron transport dead zone of the thick electrode and maintains the structural integrity of the long-cycle structure.

[0031] In some preferred embodiments, the short-range conductive component comprises one-dimensional short-cut carbon fibers and / or short carbon nanotubes. Preferably, the specific surface area of ​​the short-range conductive component is 30-150 m². 2 / g, for example, could be 30 m 2 / g, 50m 2 / g, 100 m 2 / g, 150 m 2 / g etc.

[0032] Preferably, the length of the short-range conductive component is 1-5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., and the aspect ratio is greater than 8.

[0033] In some preferred embodiments, the long-range conductive component comprises one-dimensional long carbon fibers or long carbon nanotubes.

[0034] Preferably, the specific surface area of ​​the long-range conductive component is 5-30 m². 2 / g, for example, could be 5 m 2 / g、10 m 2 / g、15 m 2 / g、20 m 2 / g、25 m 2 / g、30 m 2 / g etc.

[0035] Preferably, the length of the long-range conductive component is 6-30 μm, for example, it can be 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, etc., and the aspect ratio is greater than 40.

[0036] Preferably, the mass ratio of the short-range conductive component to the long-range conductive component is 2-5:1, for example, it can be 2:1, 3:1, 4:1, 5:1, etc.

[0037] A second aspect of the present invention provides a positive electrode material, comprising: a positive electrode active material, a sulfide solid electrolyte, and the aforementioned composite conductive agent.

[0038] In some preferred embodiments, the amount of the composite conductive agent added is 0.5%-2.0% of the mass of the positive electrode active material, for example, it can be 0.5%, 1%, 1.5%, 2.0%, etc.

[0039] In some preferred embodiments, the sulfide solid electrolyte includes Li6PS5Cl, Li 10 GeP2S 12 One or more of the Li2S-P2S5 system glass-ceramic electrolytes.

[0040] Preferably, the sulfide solid electrolyte includes a first-size electrolyte and a second-size electrolyte; wherein the D50 of the first-size electrolyte is smaller than the D50 of the second-size electrolyte.

[0041] Preferably, the D50 of the first particle size electrolyte is 0.2-2 μm, for example, it can be 0.2 μm, 0.5 μm, 1.5 μm, 2 μm, etc.

[0042] Preferably, the D50 of the second particle size electrolyte is 2-10 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0043] Preferably, the mass ratio of the first particle size electrolyte to the second particle size electrolyte is 0.25-1:1, for example, it can be 0.25:1, 0.5:1, 0.75:1, 1:1, etc.

[0044] Preferably, the positive electrode active material includes one or more of layered oxides, lithium-rich manganese-based materials, and spinel-type positive electrode materials.

[0045] Preferably, the areal capacity of the positive electrode material is ≥5.0 mAh / cm². 2 .

[0046] A third aspect of the present invention provides a method for preparing a cathode material, comprising: (a) The positive electrode active material, the first particle size sulfide solid electrolyte, and the short-range conductive component are mixed to obtain a short-range conductive premix. (b) The long-range conductive component and the second-size sulfide solid electrolyte are mixed to obtain a long-range conductive premix. (c) The short-range conductive premix is ​​mixed with the long-range conductive premix to obtain the positive electrode material.

[0047] Specifically, this invention employs a fully dry, step-by-step construction process, combined with sulfide electrolyte particle gradation to achieve precise spatial control, wherein: Step a specifically involves: short-range network construction, which involves dry high-BET short-range one-dimensional conductive agent, positive electrode active material, and small-particle-size sulfide electrolyte through high-energy ball milling / mixing. Utilizing mechanical force and the surface adsorption characteristics of the high-BET component, the short-range conductive agent is uniformly anchored and coated onto the surface of the active material and the gaps between small-particle electrolyte particles, forming a dense short-range ionic / electronic conductive matrix.

[0048] Step b specifically involves long-range network embedding. A low-BET long-range one-dimensional conductive agent and a large-particle-size sulfide electrolyte are added to the matrix and dry-mixed using a low-shear force method. Utilizing the steric hindrance effect and graded porous network generated by the large-particle electrolyte, the long-range conductive agent is directionally distributed between the composite particles, forming a macroscopic bridging network spanning the particle gaps, thus avoiding over-coating of active materials or blocking ion channels.

[0049] The cathode material preparation method provided by this invention employs a fully dry, stepwise process of high-energy ball milling to construct a short-range matrix followed by low-shear mixing and embedding into a long-range framework, thus avoiding the corrosive effects of polar solvents on the sulfide electrolyte. A gradation system of sulfide electrolytes with varying particle sizes is introduced. Utilizing the steric hindrance and graded pore channels created by the large particles, the long-range conductive agent is directionally guided to distribute between the particles, and the high-BET conductive agent is precisely enriched around the active material.

[0050] Meanwhile, this invention synergistically achieves a comprehensive leap in the first-cycle efficiency, rate capability, cycle life, and energy density of thick electrodes. Specifically, (1) Interface and pore optimization: Eliminating 0D ineffective voids and isolating low-BET long-range components significantly reduces the generation of the interface passivation layer under high voltage; in addition, the formed open mesopores greatly promote the uniform filling of sulfide electrolytes, while providing rapid ion / electron transfer to the surface of cathode material particles, achieving a significant improvement in the first-cycle coulombic efficiency. (2) Dynamic contact maintenance: The short 1D micro-anchoring effect completely solves the problem of capacity drop in the early stage of solid thick electrode cycling, ensuring mechanical stability in long-cycle cycling. (3) High-rate kinetic guarantee: The dual-grade network and open pores eliminate the bottleneck of mass transfer at the thick scale. (4) Reduced load without reduced efficiency: The total amount of conductive agent added can be reduced to 30%~50% of the traditional system, and the reduction of the proportion of inactive materials directly improves the energy density of thick cathodes, which is in line with the trend of continuous manufacturing of dry electrodes.

[0051] In some preferred embodiments, the mixing time in step (a) is 2-6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc., and the rotation speed is 200-500 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, etc.

[0052] Preferably, the mixing time in step (b) is 10-30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc., and the rotation speed is 300-600 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, etc.

[0053] Preferably, the mixing time in step (c) is 15-40 minutes, for example, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, etc., and the rotation speed is 100-300 rpm, for example, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, etc.

[0054] Preferably, the preparation method further includes: molding and rolling the mixture obtained in step c to obtain an areal capacity of ≥5.0 mAh / cm³. 2 The positive electrode.

[0055] A fourth aspect of the present invention provides a positive electrode, comprising the aforementioned positive electrode material or a positive electrode material prepared by the aforementioned preparation method.

[0056] The positive electrode provided by this invention is preferably a thick positive electrode for a sulfide all-solid-state battery. The thick positive electrode does not contain nanoscale ineffective voids formed by the agglomeration of zero-dimensional conductive carbon black. The short-range conductive component overlaps with the long-range conductive component to form open mesopores, and the sulfide solid electrolyte fills these open mesopores.

[0057] In a preferred embodiment of the present invention, the method for preparing the positive electrode includes the following steps: Step 1: Pre-construction of the short-range conductive network (ball milling coating and micro-anchoring): In an inert atmosphere glove box with a dew point ≤ -50℃ and a water oxygen content < 0.1 ppm, weigh the positive electrode active material, small-particle-size sulfide solid electrolyte, and high BET one-dimensional short-range conductive component according to the set ratio, and place them in a ball mill jar. Add inert ball milling media, seal, and place in a planetary ball mill. Ball mill for 2-6 hours at 200-500 rpm. During this process, the one-dimensional short-range conductive component, with its high specific surface area and small average length, uniformly anchors and coats the surface of the positive electrode active material particles under mechanical shearing, and tightly fills the gaps between the small-particle-size electrolyte particles. The overlapping of the one-dimensional short-range fibers avoids the ineffective nanopores generated by the agglomeration of traditional 0D carbon black, forming open mesopores that are conducive to subsequent solid electrolyte filling, thus constructing a highly dense, low interfacial resistance short-range conductive network.

[0058] Step 2, Long-range conductive framework premixing: Large-particle-size sulfide solid electrolyte and one-dimensional long-range conductive component are added to a three-dimensional mixer in a specific ratio and dry-mixed at 300-600 rpm for 10-30 minutes under an inert atmosphere. This ensures uniform dispersion of the low-BET one-dimensional long-range conductive component and the large-particle-size electrolyte, preventing agglomeration and preparing for the subsequent construction of macroscopic long-range transport channels.

[0059] Step 3: Two-stage dry compounding: The short-range conductive premixed powder obtained in Step 1 and the long-range conductive premixed powder obtained in Step 2 are transferred to a low-shear dry mixing device in proportion and gently mixed at 100-300 rpm for 15-40 minutes. This step strictly controls the mixing shear force to protect the short-range anchoring coating structure formed in Step 1 from damage. After mixing, the one-dimensional long-range conductive component is uniformly distributed in the macroscopic gaps between the composite particles, forming macroscopic bridges across multiple particles. It intertwines with the short-range network in three-dimensional space, constructing a two-stage three-dimensional nested conductive network with microscopic dynamic anchoring and macroscopic static bridging.

[0060] Step 4, Thick Electrode Forming and Rolling: The compounded positive electrode powder is evenly spread on the surface of the current collector. First, it is cold-pressed under an isostatic press at 50-150 MPa for pre-forming, followed by temperature-controlled rolling on a roller press. The rolling temperature is controlled at 20-40℃, and the roller gap is finely adjusted multiple times until the target surface capacity is ≥5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0061] The fifth aspect of the present invention provides a sulfide all-solid-state battery, comprising: a negative electrode, a solid electrolyte membrane, and the positive electrode.

[0062] The present invention may employ a flexible or rectangular structure; for example, Figure 1 It is a solid-state battery structure.

[0063] In some embodiments, the battery includes a casing, within which electrode assemblies are encapsulated. The battery may contain one or more electrode assemblies, which can be selected by those skilled in the art according to specific practical needs.

[0064] In a sixth aspect, the present invention provides an electrical device comprising the above-described sulfide all-solid-state battery.

[0065] According to another aspect of the present invention, an electrical device is provided, comprising at least one of the above-described solid-state battery or battery module. The solid-state battery or battery module can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include mobile devices (typically mobile phones, laptops, etc.), electric vehicles (typically pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, or energy storage systems, etc.

[0066] Figure 2 This is an example of an electrical device. The device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used. The invention is further illustrated below through embodiments. Unless otherwise specified, the materials in the embodiments are prepared according to existing methods or purchased directly from the market.

[0067] Example 1 This embodiment provides a positive electrode, the preparation process of which is as follows: Step 1: Short-range conductive network preconstruction: In an inert atmosphere glove box with a dew point ≤ -50℃ and a water oxygen content < 0.1 ppm, weigh out the positive electrode active material (NCM811), small-particle-size sulfide solid electrolyte Li6PS5Cl (D50 = 0.5 μm), and a high-BET one-dimensional short-range conductive component (using BET of 50 μm) according to the set ratio. 2 Carbon nanofibers (with an average length of 2 μm and an aspect ratio of 40) were placed in a ball mill jar. Inert grinding media were added, and the jar was sealed and placed in a planetary ball mill. The mixture was then ball-milled at 350 rpm for 4 hours.

[0068] Step 2, Long-range conductive framework premixing: The large-particle-size sulfide solid electrolyte Li6PS5Cl (D50 = 6 μm) is mixed with a one-dimensional long-range conductive component (using a BET of 10 m). 2 (Short-range conductive carbon fibers with an average length of 15 μm and an aspect ratio of 75) were added to a three-dimensional mixer in proportion and dry-mixed at 450 rpm for 20 minutes under an inert atmosphere. The mass ratio of short-range conductive components to long-range conductive components was 3:1, the total amount of composite conductive agent added was 1 wt% of the positive electrode active material, and the mass ratio of small-particle-size sulfide solid electrolyte to large-particle-size sulfide solid electrolyte was 0.5:1.

[0069] Step 3: Two-stage dry mixing: The short-range conductive premixed powder obtained in Step 1 and the long-range conductive premixed powder obtained in Step 2 are transferred to a low-shear dry mixing device in proportion and gently mixed at 200 rpm for 30 minutes. The masses corresponding to the different components are shown in Table 1 below. The specific masses involved in all subsequent examples and comparative examples are also shown in Table 1.

[0070] Step 4, Thick Electrode Forming and Rolling: The compounded positive electrode powder is evenly spread on the surface of the current collector. First, it is cold-pressed at 100 MPa using an isostatic press for pre-forming, followed by temperature-controlled rolling on a roller press. The rolling temperature is controlled at 30℃, and the roller gap is finely adjusted multiple times until the target surface capacity reaches 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0071] Example 2 This embodiment provides a positive electrode, the preparation process of which differs from that of Embodiment 1 in that: In step 1, the positive electrode active material (NCM811), the small-particle-size sulfide solid electrolyte Li6PS5Cl (D50=0.5 μm), and the high BET one-dimensional short-range conductive component (BET=30 μm) are weighed according to the set ratio. 2 (g, average length 2 μm and aspect ratio 26), placed in a ball mill jar.

[0072] In step 2, the large-particle-size sulfide solid electrolyte Li6PS5Cl (D50 = 6 μm) is combined with a one-dimensional long-range conductive component (BET = 6 μm). 2 The components (g, average length 15 μm, and aspect ratio 50) were added to a three-dimensional mixer in proportion. The mass ratio of the short-range conductive component to the long-range conductive component was 3:1, the total amount of composite conductive agent added was 0.5 wt% of the positive electrode active material, and the mass ratio of small-particle-size sulfide solid electrolyte to large-particle-size sulfide solid electrolyte was 0.5:1.

[0073] In step 3, the short-range conductive premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred to a low-shear dry mixing device in proportion.

[0074] The final surface capacity obtained is 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0075] Example 3 This embodiment provides a positive electrode, the preparation process of which differs from that of Embodiment 1 in that: In step 1, the following components are weighed: positive electrode active material (NCM811), small-particle-size sulfide solid electrolyte Li6PS5Cl (D50 = 0.5 μm), and high-BET one-dimensional short-range conductive component (BET = 150 μm). 2 (g, average length 2 μm and aspect ratio 100), placed in a ball mill jar.

[0076] In step 2, the large-particle-size sulfide solid electrolyte Li6PS5Cl (D50 = 6 μm) is combined with a one-dimensional long-range conductive component (BET = 30 m). 2 The components (g, average length 15 μm, and aspect ratio 200) were added to a three-dimensional mixer in proportion. The mass ratio of the short-range conductive component to the long-range conductive component was 3:1, the total amount of the composite conductive agent added was 2 wt% of the positive electrode active material, and the mass ratio of the small-particle-size sulfide solid electrolyte to the large-particle-size sulfide solid electrolyte was 0.5:1.

[0077] In step 3, the short-range conductive premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred to a low-shear dry mixing device in proportion.

[0078] The final surface capacity obtained is 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0079] Example 4 This embodiment provides a positive electrode, the preparation process of which differs from that of Embodiment 1 in that: In step 1, the positive electrode active material (NCM811), the small-particle-size sulfide solid electrolyte Li6PS5Cl (D50=0.5 μm), and the high-BET one-dimensional short-range conductive component (BET=50 μm) are weighed according to the set ratio. 2 (g, average length 1.0 μm and aspect ratio 20), placed in a ball mill jar.

[0080] In step 2, the large-particle-size sulfide solid electrolyte Li6PS5Cl (D50 = 6 μm) is combined with a one-dimensional long-range conductive component (BET = 10 m). 2 The components (g, average length 5μm, and aspect ratio 40) were added to a three-dimensional mixer in proportion. The mass ratio of the short-range conductive component to the long-range conductive component was 2:1, the total amount of composite conductive agent added was 1.0wt% of the positive electrode active material, and the mass ratio of small-particle-size sulfide solid electrolyte to large-particle-size sulfide solid electrolyte was 0.5:1.

[0081] In step 3, the short-range conductive premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred to a low-shear dry mixing device in proportion.

[0082] The final surface capacity obtained is 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0083] Example 5 This embodiment provides a positive electrode, the preparation process of which differs from that of Embodiment 1 in that: In step 1, the positive electrode active material (NCM811), the small-particle-size sulfide solid electrolyte Li6PS5Cl (D50=0.5 μm), and the high-BET one-dimensional short-range conductive component (BET=50 μm) are weighed according to the set ratio. 2 (g, average length 5.0 μm and aspect ratio 100), placed in a ball mill jar.

[0084] In step 2, the large-particle-size sulfide solid electrolyte Li6PS5Cl (D50 = 6 μm) is combined with a one-dimensional long-range conductive component (BET = 10 m). 2 The components (g, average length 30 μm, and aspect ratio 240) were added to a three-dimensional mixer in proportion. The mass ratio of the short-range conductive component to the long-range conductive component was 5:1, the total amount of composite conductive agent added was 1.0 wt% of the positive electrode active material, and the mass ratio of small-particle-size sulfide solid electrolyte to large-particle-size sulfide solid electrolyte was 0.5:1.

[0085] In step 3, the short-range conductive premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred to a low-shear dry mixing device in proportion.

[0086] The final electrode surface capacity was 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0087] Example 6 This embodiment provides a positive electrode, the preparation process of which differs from that of Embodiment 2 in that: In step 1, the positive electrode active material (NCM811), small-particle-size sulfide solid electrolyte, and high-BET one-dimensional short-range conductive component (D50=0.2 μm) and high-BET one-dimensional short-range conductive component (using BET=50 μm) are weighed according to the set ratio. 2 Carbon nanofibers (with an average length of 2 μm and an aspect ratio of 40) were placed in a ball mill jar.

[0088] In step 2, a large-particle-size sulfide solid electrolyte (D50 = 2 μm) is mixed with a one-dimensional long-range conductive component (using a BET of 10 m). 2 Long-range conductive carbon fibers (with an average length of 15 μm and an aspect ratio of 75) are added to a three-dimensional mixer in proportion. The mass ratio of short-range conductive components to long-range conductive components is 3:1, the total amount of composite conductive agent added is 1 wt% of the mass of the positive electrode active material, and the mass ratio of small-particle-size sulfide solid electrolyte to large-particle-size sulfide solid electrolyte is 0.25:1.

[0089] In step 3, the short-range conductive premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred in a low-shear dry mixing device in a specific ratio. The final electrode areal capacity is 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0090] Example 7 This embodiment provides a positive electrode, the preparation process of which differs from that of Embodiment 1 in that: In step 1, the positive electrode active material (NCM811), small-particle-size sulfide solid electrolyte, and high-BET one-dimensional short-range conductive component (D50=2μm) and high-BET one-dimensional short-range conductive component (with BET of 50 μm) are weighed according to the set proportions. 2 Carbon nanofibers (with an average length of 2 μm and an aspect ratio of 40) were placed in a ball mill jar.

[0091] In step 2, a large-particle-size sulfide solid electrolyte (D50 = 10 μm) is mixed with a one-dimensional long-range conductive component (using a BET of 10 m). 2(Short-range conductive carbon fibers with an average length of 15 μm and an aspect ratio of 75) are added to a three-dimensional mixer in proportion. The mass ratio of short-range conductive components to long-range conductive components is 3:1, the total amount of composite conductive agent added is 1 wt% of the mass of the positive electrode active material, and the mass ratio of small-particle-size sulfide solid electrolyte to large-particle-size sulfide solid electrolyte is 1:1.

[0092] In step 3, the short-range conductive premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred in a low-shear dry mixing device in a specific ratio. The final electrode areal capacity is 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0093] Comparative Example 1 This comparative example provides a positive electrode, the preparation process of which differs from that of Example 1 in that: In step 1, the positive electrode active material and the small-particle-size sulfide solid electrolyte (D50=0.5μm) are weighed according to the set ratio and placed in a ball mill jar.

[0094] In step 2, a large-particle-size sulfide solid electrolyte (D50 = 6 μm) is mixed with a one-dimensional long-range conductive component (using a BET of 10 m). 2 Long-range conductive carbon fibers (with an average length of 15 μm and an aspect ratio of 75) are added to a three-dimensional mixer in proportion. The amount of long-range conductive component added is 1 wt% of the mass of the positive electrode active material, and the particle size mass ratio of small-particle-size sulfide solid electrolyte to large-particle-size sulfide solid electrolyte is 0.5:1.

[0095] In step 3, the premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred in a low-shear dry mixing device in a specific ratio. The final electrode areal capacity is 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0096] Comparative Example 2 This comparative example provides a positive electrode, the preparation process of which differs from that of Example 1 in that: In step 1, the positive electrode active material, small-particle-size sulfide solid electrolyte (D50=0.5μm), and high-BET one-dimensional short-range conductive component (with BET of 50 μm) are weighed according to the set ratio. 2 Carbon nanofibers (with an average length of 2 μm and an aspect ratio of 40) were placed in a ball mill jar.

[0097] In step 2, the large-particle-size sulfide solid electrolyte is added to a three-dimensional mixer. The amount of the short-range conductive component added is 1 wt% of the mass of the positive electrode active material, and the particle size mass ratio of the small-particle-size sulfide solid electrolyte to the large-particle-size sulfide solid electrolyte is 0.5:1.

[0098] In step 3, the premixed powder obtained in step 1 and the long-range conductive premixed powder obtained in step 2 are transferred in a low-shear dry mixing device in a specific ratio. The final electrode areal capacity is 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0099] Comparative Example 3 This comparative example provides a positive electrode, the preparation process of which differs from that of Example 1 in that: Short-range and long-range conductive agents, all electrolytes, and active materials were mixed in a high-energy ball mill (400 rpm for 4 hours) in a single process, followed by direct roll forming. The final electrode surface capacity was 5.0 mAh / cm². 2 The thick electrode of the positive electrode in a sulfide-based all-solid-state battery.

[0100] Comparative Example 4 This comparative example provides a positive electrode, the preparation process of which differs from that of Example 1 in that: The 0D conductive carbon black (Super P, BET 65 m) commonly used in traditional liquid systems is employed. 2 / g) replaces the one-dimensional short-range conductive agent in Example 1, the long-range conductive component, the mass ratio and total addition amount are the same as in Example 1, and the rest of the process is the same as in Example 1.

[0101] The positive electrode electrodes prepared using the above-described embodiments and comparative examples were then used to assemble the battery in the following manner: The solid electrolyte is Li6PS5Cl; the negative electrode is an In-Li composite negative electrode (the molar ratio of In to Li is 1:0.4); the mold battery operates at a pressure of 200 mPa; the battery assembly is carried out in a glove box (Ar atmosphere, water and oxygen content <1 ppm). Assembly process: Weigh 0.1000g of E09 electrolyte and pour it into the mold. Then, gently vibrate to make the surface of the electrolyte powder relatively flat. Apply a pressure of 1t (125MPa) for 1 minute. Weigh out the positive electrode sheet that meets the quality requirements (area capacity of 5.0±0.2mAh / cm²). 2Place it in the mold, apply a pressure of 3.2t (400MPa), and hold for 2 minutes; place the indium sheet in the mold, then attach the lithium sheet to the middle of the long electrode post, and finally place the long electrode post with the lithium sheet attached into the mold, apply a pressure of 0.4t (50MPa), and hold for 1 minute; finally, place the mold into the fixture, apply a pressure of 2.8t, and use a 9 N·m torque wrench to tighten the screws clockwise multiple times until the screws are locked.

[0102] Test conditions: room temperature (25±2℃), voltage range 1.9~3.7 V, constant 1C rate (1C=200 mAh / g).

[0103] Test method: First, let it stand for 2 hours, then charge it at 0.1C to 3.7V and let it stand for 5 minutes; then discharge it at 0.1C to 1.9V and let it stand for 5 minutes; repeat 3 times; then charge it at 1C to 3.7V and let it stand for 5 minutes; then discharge it at 1C to 1.9V and let it stand for 5 minutes, repeat 1000 times.

[0104] The masses of different components in the examples and comparative examples are shown in Table 1 and Table 2, respectively: Table 1. Mass of different components in the examples

[0105] Table 2. Mass of different components in the comparative examples

[0106] The test results are shown in Table 3.

[0107] Table 3 Electrical performance results for different embodiments

[0108] The data in Table 3 shows that: The performance fluctuations in Examples 1-7 were minimal (initial efficiency ≤ 1.8%, specific capacity ≤ 2.0%), confirming that short-range and long-range fibers synergistically constructed a three-dimensional electronic framework spanning the entire thickness. Comparative Example 2 (without long-range fibers) experienced a dramatic 21.5% rate drop, while Comparative Example 1 (without short-range fibers) only saw an 11.8% drop. This quantitatively demonstrates that the long-range fibers are dedicated to cross-scale bridging, while the short-range fibers ensure interface coverage; their functions are not interchangeable, completely overcoming the technical shortcomings of high percolation threshold and poor network connectivity of single conductive agents in thick electrodes. Therefore, the dual one-dimensional conductive agent system effectively eliminates electron transport dead zones in thick electrodes.

[0109] The initial efficiency of Examples 1-7 remained stable at 89.2%-91.0%, significantly higher than the 85.2% of Comparative Example 4 (sp-substituted), while Comparative Example 4 showed a 11.2% decrease in g-capacity and a 27.2% decrease in rate capability. This comparison verifies that one-dimensional fibers have a lower specific surface area than 0d carbon black, significantly reducing the contact area with the sulfide electrolyte. This fundamentally suppresses interfacial oxidation side reactions and the formation of a high-resistivity layer, resolving the core contradiction that high specific surface area conductive agents exacerbate interfacial degradation. Therefore, low specific surface area fibers can suppress sulfide interfacial side reactions at their source.

[0110] Examples 6-7 represent the upper and lower limits of dual-particle-size gradation, respectively. The results of Examples 6-7 show that, within the preferred range, small-particle-size filling ensures interfacial ion pathways, while the large-particle-size framework provides rapid transport channels, achieving a rate capability ≥87.8% and a specific capacity ≥206.0 mAh / g. This design overcomes the problems of prolonged mass transfer paths and severe polarization in thick electrodes caused by simple physical blending, achieving ion / electron synergistic transport at high packing density. These results confirm that dual-particle-size electrolyte gradation is the key structural basis for achieving ion / electron synergistic transport in thick electrodes.

[0111] Comparative Example 3 had the same formulation as Example 1, except for the ball milling process, resulting in a 6.5% decrease in the ratio and a 2.6% decrease in the specific capacity. This confirms that the stepwise premixing process is key to achieving multiphase homogeneous dispersion and avoiding local enrichment. Conventional stirring cannot meet the requirements for the full-thickness network connectivity of thick electrodes. Therefore, the three-step mixing method is a necessary process support for thick electrodes.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite conductive agent for positive electrode materials, characterized in that, include: The short-range conductive component and the long-range conductive component are both one-dimensional fibrous conductive materials. The specific surface area of ​​the short-range conductive component is higher than that of the long-range conductive component, and the average length of the short-range conductive component is less than that of the long-range conductive component.

2. The composite conductive agent for positive electrode materials according to claim 1, characterized in that, The short-range conductive component includes short-cut carbon fibers and / or short carbon nanotubes; Preferably, the specific surface area of ​​the short-range conductive component is 30-150 m². 2 / g; Preferably, the length of the short-range conductive component is 1-5 μm, and the aspect ratio is greater than 8; Preferably, the long-range conductive component comprises long carbon fibers or long carbon nanotubes; Preferably, the specific surface area of ​​the long-range conductive component is 5-30 m². 2 / g; Preferably, the length of the long-range conductive component is 6-30 μm, and the aspect ratio is greater than 40; Preferably, the mass ratio of the short-range conductive component to the long-range conductive component is 2-5:

1.

3. A positive electrode material, characterized in that, include: Positive electrode active material, sulfide solid electrolyte and composite conductive agent as described in claim 1 or 2.

4. The cathode material according to claim 3, characterized in that, The amount of the composite conductive agent added is 0.5%-2.0% of the mass of the positive electrode active material.

5. The positive electrode material according to claim 3, characterized in that, The sulfide solid electrolyte includes Li6PS5Cl, Li 10 GeP2S 12 One or more of the Li2S-P2S5 system glass-ceramic electrolytes; Preferably, the sulfide solid electrolyte comprises a first-size electrolyte and a second-size electrolyte; wherein the D50 of the first-size electrolyte is smaller than the D50 of the second-size electrolyte. Preferably, the D50 of the first particle size electrolyte is 0.2-2 μm; Preferably, the D50 of the second particle size electrolyte is 2-10 μm; Preferably, the mass ratio of the first particle size electrolyte to the second particle size electrolyte is 0.25-1:1; Preferably, the positive electrode active material includes one or more of layered oxides, lithium-rich manganese-based materials, and spinel-type positive electrode materials; Preferably, the areal capacity of the positive electrode material is ≥5.0 mAh / cm². 2 .

6. The method for preparing the cathode material according to any one of claims 3-5, characterized in that, include: (a) The positive electrode active material, the first particle size sulfide solid electrolyte, and the short-range conductive component are mixed to obtain a short-range conductive premix. (b) The long-range conductive component and the second-size sulfide solid electrolyte are mixed to obtain a long-range conductive premix. (c) The short-range conductive premix is ​​mixed with the long-range conductive premix to obtain the positive electrode material.

7. The preparation method according to claim 6, characterized in that, The mixing time in step (a) is 2-6 hours, and the rotation speed is 200-500 rpm; Preferably, the mixing time in step (b) is 10-30 minutes and the rotation speed is 300-600 rpm; Preferably, the mixing time in step (c) is 15-40 minutes and the rotation speed is 100-300 rpm; Preferably, the preparation method further includes: molding and rolling the mixture obtained in step c to obtain an areal capacity ≥ 5.0 mAh / cm³. 2 The positive electrode.

8. A positive electrode, characterized in that, This includes the cathode material as described in any one of claims 3-5 or the cathode material prepared by the preparation method described in any one of claims 6-7.

9. A sulfide all-solid-state battery, characterized in that, include: The negative electrode, the solid electrolyte membrane, and the positive electrode as described in claim 8.

10. An electrical device, characterized in that, Including the sulfide all-solid-state battery as described in claim 9.

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