Thick electrode sheet and lithium ion battery

Abstract

The application provides a thick electrode sheet and a lithium ion battery. The thick electrode sheet comprises a current collector and an active material layer. The active material layer comprises a main active material, a binder, a conductive agent and a conductive liquid storage phase. The conductive liquid storage phase comprises one or more of mesoporous carbon material, graphene aerogel microspheres and nitrogen-doped porous carbon. The mass fraction of the conductive liquid storage phase in the active material layer is 0.05-10.0 wt%. The surface density of the active material layer is greater than or equal to 15 mg / cm2. The conductive and ion diffusion network is constructed by adding the conductive liquid storage phase with conductivity. The porous structure of the conductive liquid storage phase is fully utilized. The addition amount window of the conductive liquid storage phase is determined. The conductive gain effect of the conductive liquid storage phase on the electrode sheet system and the energy density reduction effect are balanced.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a thick electrode sheet and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and environmental friendliness. With the increasing demands of these applications, further improving the energy density of lithium-ion batteries has become an important research direction for the industry.

[0003] One effective way to improve the energy density of lithium-ion batteries is to increase the thickness of the electrode sheets, i.e., to adopt a thick electrode sheet design. Thick electrode sheets can increase the amount of active material used in the electrode while reducing the proportion of inactive materials such as current collectors, thereby improving the overall energy density of the battery. However, to improve the volumetric energy density and maintain structural integrity, thick electrode sheets inevitably require higher compaction density conditions, which also brings new technical challenges: while increasing compaction density reduces electrode porosity and improves volumetric energy density, it significantly increases the tortuosity τ of the ion transport path, thus affecting the effective ion diffusion coefficient. - ²The regular degradation eventually leads to a severe deterioration in the rate performance of the battery.

[0004] Furthermore, excessively high compaction density leads to an overly dense electrode structure, making it difficult for the electrolyte to wet. To improve electrolyte wettability, pore-forming agents are typically introduced to form a porous network. Large-pore (>100 nm) pore-forming agents can significantly improve electrolyte wettability, but they can also reduce the mechanical strength of the electrode, leading to powder shedding and insufficient electrolyte retention, resulting in electrolyte loss during cycling and the inability to form a stable ion transport network. Conventional pore-forming agents (such as mesoporous silica and polymethyl methacrylate microspheres) are mostly insulators, which can block electron conduction paths, causing the conductive agent network to be interrupted, significantly increasing the internal resistance of the electrode, and having a limited effect on improving wettability. In addition, pore-forming agents increase the weight of the inactive material portion of the electrode, thus offsetting the energy density advantage of thicker electrodes.

[0005] Existing technologies typically employ a single strategy to address the aforementioned technical problems. For example, they may optimize the conductive network by increasing the amount of conductive agent, but this fails to solve the wetting problem; or they may improve the pore structure by introducing pore-forming agents, but this sacrifices conductivity; or they may increase both conductive agents and pore-forming agents, which would lower the energy density of the thick electrode sheet. None of these approaches can fundamentally coordinate the multiple performance requirements of the thick electrode sheet.

[0006] Therefore, there is an urgent need in this field for a comprehensive technical solution that can simultaneously resolve the contradictions between the wettability, conductivity, and energy density of thick electrode sheets. Summary of the Invention

[0007] To address the aforementioned issues and meet the requirements for low tortuosity, high conductivity, rapid wetting, and high energy density of electrode sheets, the first aspect of this application provides a thick electrode sheet comprising a current collector and an active material layer coated on the current collector. The active material layer comprises a main active material, a binder, a conductive agent, and a conductive reservoir phase. The conductive reservoir phase comprises one or more of mesoporous carbon materials, graphene aerogel microspheres, and nitrogen-doped porous carbon. The conductive reservoir phase accounts for 0.05-10.0 wt% of the mass of the active material layer; the areal density of the active material layer is ≥15 mg / cm².

[0008] Furthermore, the areal density of the active substance layer is ≥20 mg / cm², preferably 20-50 mg / cm².

[0009] In some optional embodiments, the conductive reservoir phase accounts for 0.1-5 wt% of the active material layer, and the conductive reservoir phase satisfies at least one of the following characteristics: a: at a compaction pressure of 10 MPa, the total pore volume of the conductive reservoir phase powder is ≥0.2 cm³ / g; b: at a compaction pressure of 10 MPa, the electronic conductivity of the conductive reservoir phase powder is ≥10 S / m; c: at a compaction pressure of 0.01-3.0 V (vs. Li / Li + Within the voltage range of ), the reversible specific capacity of the conductive liquid phase is ≥100mAh / g.

[0010] Preferably, the conductive liquid phase accounts for 0.1-5 wt% of the active material layer, and the conductive liquid phase simultaneously meets the following characteristics: a: at a compaction pressure of 10 MPa, the total pore volume of the conductive liquid phase powder is ≥0.2 cm³ / g; b: at a compaction pressure of 10 MPa, the electronic conductivity of the conductive liquid phase powder is ≥10 S / m; c: at a compaction pressure of 0.01-3.0 V (vs. Li / Li + Within the voltage range of ), the reversible specific capacity of the conductive liquid phase is ≥100mAh / g; Furthermore, the conductive liquid phase accounts for 0.5-3.0 wt% of the mass of the active material layer.

[0011] Furthermore, the total pore volume of the conductive liquid phase powder is ≥0.3 cm³ / g, preferably 0.5-2.5 cm³ / g.

[0012] Furthermore, at 0.01 -3.0 V (vs. Li / Li + Within the voltage range of ), the reversible specific capacity of the conductive liquid phase is ≥150 mAh / g, preferably ≥200 mAh / g.

[0013] Furthermore, the electronic conductivity of the thick electrode sheet is ≥0.4 S / cm, preferably ≥0.5 S / cm.

[0014] In some optional embodiments, the compaction density D of the thick electrode sheet is related to the theoretical maximum compaction density D of the main active material. max Satisfy: D≥80%D max .

[0015] Furthermore, the compaction density D of the thick electrode sheet is similar to the theoretical maximum compaction density D of the main active material. max Satisfy: D≥85%D max .

[0016] In some alternative embodiments, the theoretical maximum compaction density D of the main active material is... max The range is 3.5 g / cm³. 3 -4.0g / cm 3 .

[0017] In some alternative embodiments, the areal density ρ of the active material layer 面 The total pore volume of the conductive liquid phase powder is 0.5-2.5 cm³ / g, with a density of 20-50 mg / cm² and a compaction pressure of 10 MPa.

[0018] In some alternative embodiments, the main active substance accounts for 88.0-98.9 wt% of the mass of the active substance layer.

[0019] In some alternative embodiments, when the conductive reservoir phase comprises a mesoporous carbon material, the mesoporous carbon material has a most probable pore size of 10-50 nm.

[0020] Specifically, the conductive storage liquid phase including mesoporous carbon material can be understood as the conductive storage liquid phase being mesoporous carbon material, or the conductive storage liquid phase being a mixture of mesoporous carbon material and graphene aerogel microspheres, a mixture of mesoporous carbon material and nitrogen-doped porous carbon, or a mixture of mesoporous carbon material, graphene aerogel microspheres (e.g., porous graphene aerogel microspheres) and nitrogen-doped porous carbon.

[0021] Furthermore, the mesoporous carbon material has a most probable pore size of 10-50 nm, a total pore volume of 0.5-2.5 cm³ / g, and an electronic conductivity of ≥100 S / m at 0.01-3.0 V (vs. Li / Li). + The reversible specific capacity within the voltage range is ≥200 mAh / g.

[0022] In some alternative embodiments, the liquid retention rate of the thick electrode sheet is ≥20 μL / mg.

[0023] In some alternative embodiments, the global tortuosity of the thick electrode sheet is ≤3.5, preferably ≤3.0.

[0024] A second aspect of this application provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is a thick electrode sheet as described in any one of the preceding claims.

[0025] In some alternative embodiments, the electrolyte is completely immersed in the thick electrode sheet for ≤40 min.

[0026] Furthermore, the duration for which the electrolyte completely wets the thick electrode sheet is preferably ≤30 min.

[0027] In some optional embodiments, the energy density of the battery is ≥260 Wh / kg, and the battery has a capacity retention rate of >84% at 2C / 0.5C rate and a capacity retention rate of >84% after 500 cycles at 1C rate.

[0028] This application has at least the following technical effects: 1) The first aspect of this application provides a thick electrode sheet comprising a conductive liquid storage phase (one or more of mesoporous carbon material, graphene aerogel microspheres, and nitrogen-doped porous carbon), which can achieve the following technical effects: First, the porous structure of the conductive reservoir phase can connect with the conductive agent to form a continuous conductive network, ensuring efficient electron transport. Simultaneously, its internal channels form low-torsion ion diffusion channels, enabling rapid ion migration. Since the conductive reservoir phase itself is conductive, rather than an insulating pore-forming agent, it does not disrupt the conductive network while constructing ion channels, thus solving the problem of decreased conductivity caused by traditional insulating pore-forming agents. Second, by rationally controlling the content of the conductive reservoir phase, the conductivity and energy density of the electrode can be balanced: when the content of the conductive reservoir phase is too low, the conductive network is incomplete, resulting in insufficient conductivity; when the content is too high, the proportion of active material decreases, leading to a decrease in energy density. Furthermore, the porous structure of the conductive reservoir phase also assists in the rapid wetting of the electrode by the electrolyte, significantly shortening the electrode wetting time and improving production efficiency.

[0029] The thick electrode sheet of this application, under high compaction and high areal density conditions, can simultaneously meet the comprehensive requirements of high conductivity, rapid wetting, and high energy density, achieving multi-objective optimization of thick electrode performance. 2) A second aspect of this application also provides a lithium-ion battery that uses the aforementioned thick electrode sheet as a positive electrode and / or negative electrode. Due to the beneficial effects of the thick electrode sheet as described above, the lithium-ion battery provided by this application has a higher upper limit of energy density and better rate performance. Detailed Implementation

[0030] The embodiments of this implementation are described in detail below. In the description of this implementation, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" and "second" are mentioned, they are only used to distinguish technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0031] In the description of this embodiment, unless otherwise explicitly limited, terms such as setting, installing, and connecting should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this embodiment in conjunction with the specific content of the technical solution.

[0032] In the description of the embodiments of this application, it should be noted that all ranges disclosed in this application are to be understood to encompass any and all subranges included therein. For example, the stated range "0.05-10.0wt%" should be considered to include any and all subranges that begin with a minimum value of 0.05wt% or greater and end with a maximum value of 10.0wt% or less, such as 0.05-3.5wt%, or 1.5-5.5wt%, or 7.5-10.0wt%. Furthermore, all ranges disclosed in this application are also considered to include the endpoints of the ranges, unless otherwise expressly stated. For example, the ranges "between 0.01 and 3.0", "0.01 to 3.0", or "0.01-3.0" should generally be considered to include the endpoints 0.01 and 3.0.

[0033] Thick electrode sheets with high areal density and high compaction density are one of the effective ways to significantly improve battery energy density. However, the high areal density and compaction density also bring about problems such as poor wetting, poor conductivity, and low ion diffusion efficiency. The fragmented coping strategies adopted by existing technologies, such as increasing the amount of conductive agent to improve conductivity and using pore-forming agents to improve wetting and ion transport effects, cannot fundamentally coordinate the multiple performance requirements of thick electrode sheets.

[0034] Based on this, this application proposes a novel approach to modifying thick electrode sheets by adding a conductive reservoir phase with a specific pore size range to construct a conductive and ion diffusion network. This approach fully utilizes the porous characteristics of the conductive reservoir phase material and clarifies the addition amount window of the conductive reservoir phase, thus balancing the conductivity gain and energy density reduction effects of the conductive reservoir phase on the electrode system.

[0035] This application provides a thick electrode sheet, comprising a current collector and an active material layer coated on the current collector. The active material layer comprises a main active material, a binder, a conductive agent, and a conductive reservoir phase. The conductive reservoir phase comprises one or more of mesoporous carbon materials, graphene aerogel microspheres, and nitrogen-doped porous carbon. The conductive reservoir phase accounts for 0.05-10.0 wt% of the mass of the active material layer. The areal density of the thick electrode sheet is ≥15 mg / cm².

[0036] The porous structure of the conductive reservoir phase can connect with the conductive agent to form a continuous conductive network, ensuring efficient electron transport. Simultaneously, its internal channels form low-torsion ion diffusion channels, enabling rapid ion migration. Since the conductive reservoir phase itself is conductive, rather than an insulating pore-forming agent, it does not disrupt the conductive network while constructing ion channels, thus solving the problem of decreased conductivity caused by traditional insulating pore-forming agents. Secondly, by rationally controlling the content of the conductive reservoir phase, the conductivity and energy density of the electrode can be balanced: when the content of the conductive reservoir phase is too low, the conductive network is incomplete, resulting in insufficient conductivity; when the content is too high, the proportion of active material decreases, leading to a decrease in energy density. Experimental tests showed that electrodes with the required amount of conductive reservoir phase only experienced a 5% increase in DCR, while replacing the conductive reservoir phase with a traditional pore-forming agent resulted in a dramatic 32% increase in DCR. Furthermore, the porous structure of the conductive reservoir phase also assists in the rapid wetting of the electrode by the electrolyte, significantly shortening the electrode wetting time and improving production efficiency. Furthermore, experimental tests have shown that, under the same areal density, the immersion time is reduced from 145 minutes to 15 minutes, which helps to improve the production efficiency of batteries.

[0037] In summary, the thick electrode sheet of this application can simultaneously meet the comprehensive requirements of high conductivity, rapid wetting and high energy density under the condition of high areal density, thus achieving multi-objective optimization of the performance of thick electrodes.

[0038] Furthermore, the areal density ρ of the active material layer 面 ≥20 mg / cm², preferably 20-50 mg / cm². High areal density ρ 面 It delivers high single-sided area capacity, providing more abundant power to external electrical devices and improving battery life.

[0039] Furthermore, the main active substance accounts for 88.0-98.9 wt% of the mass of the active substance layer.

[0040] In some optional embodiments, the compaction density D of the thick electrode sheet is related to the theoretical maximum compaction density D of the main active material. max Satisfy: D≥80%D max .

[0041] Preferably, the above relationship satisfies: D ≥ 85%D max。

[0042] Using a density close to the theoretical maximum compaction density D max The compaction density D, at an areal density ≥15 mg / cm², ensures the structural integrity and mechanical strength of the active material layer, while maximizing the electrical contact between particles and reducing interfacial resistance. Specifically, the theoretical maximum compaction density D of the main active material... max The range is 3.5 g / cm³. 3 -4.0g / cm 3 In some optional embodiments, the conductive reservoir phase accounts for 0.1-5 wt% of the active material layer, and the conductive reservoir phase satisfies at least one of the following characteristics: a: at a compaction pressure of 10 MPa, the total pore volume of the conductive reservoir phase powder is ≥0.2 cm³ / g; b: at a compaction pressure of 10 MPa, the electronic conductivity of the conductive reservoir phase powder is ≥10 S / m; c: at a compaction pressure of 0.01-3.0 V (vs. Li / Li + Within the voltage range of ), the reversible specific capacity of the conductive liquid phase is ≥100mAh / g.

[0043] Further, the mass ratio of the conductive liquid phase in the active material layer is optimized to 0.1-5 wt%. According to specific examples, within this range, as the amount of conductive liquid phase added increases, the tortuosity of the thick electrode sheet gradually decreases and the electrical performance gradually improves, but the energy density of the battery tends to weaken. Therefore, selecting this range can balance ion transport and energy density, resulting in better overall battery performance.

[0044] Furthermore, the conductive reservoir phase accounts for 0.5-3.0 wt% of the mass of the active material layer. When the conductive reservoir phase is within this range, the global tortuosity, wetting time, and liquid retention rate of the thick electrode sheet reach an optimal balance.

[0045] Furthermore, the total pore volume of the conductive liquid phase powder is ≥0.3 cm³ / g, preferably 0.5-2.5 cm³ / g.

[0046] Furthermore, at 0.01 -3.0 V (vs. Li / Li + Within the voltage range of ), the reversible specific capacity of the conductive liquid phase is ≥150 mAh / g, preferably ≥200 mAh / g.

[0047] Furthermore, the thick electrode sheet has an electronic conductivity ≥ 0.5 S / cm. The high conductivity of the conductive storage phase effectively improves the continuity of the conductive network within the electrode sheet, and the electrical performance of the battery is also significantly enhanced.

[0048] Furthermore, under a compaction pressure of 10 MPa, the total pore volume of the conductive liquid phase powder is 0.5-2.5 cm³ / g. A larger total pore volume of the conductive liquid phase powder results in a faster wetting rate and a correspondingly higher liquid retention rate, significantly improving the electrode performance.

[0049] Furthermore, when the conductive liquid phase comprises a mesoporous carbon material, the mesoporous carbon material has a most probable pore size of 10-50 nm.

[0050] Specifically, the conductive storage liquid phase including mesoporous carbon material can be understood as the conductive storage liquid phase being mesoporous carbon material, or the conductive storage liquid phase being a mixture of mesoporous carbon material and graphene aerogel microspheres, a mixture of mesoporous carbon material and nitrogen-doped porous carbon, or a mixture of mesoporous carbon material, graphene aerogel microspheres (e.g., porous graphene aerogel microspheres) and nitrogen-doped porous carbon.

[0051] Furthermore, the mesoporous carbon material has a most probable pore size of 10-50 nm, a total pore volume of 0.5-2.5 cm³ / g, and an electronic conductivity of ≥100 S / m at 0.01-3.0 V (vs. Li / Li). + The reversible specific capacity within the voltage range is ≥200 mAh / g.

[0052] It should be noted that mesoporous phases with pore sizes of 10-50 nm possess stronger mechanical strength than macropores with pore sizes >100 nm. Even after the thick electrode sheet is compacted, they remain open and interconnected. The porous structure of the conductive liquid reservoir can supplement the construction of highly reliable, low-torsion ion diffusion channels, helping to mitigate the decrease in the effective ion diffusion coefficient and ensuring rate performance. Furthermore, the 10-50 nm pore size maintains sufficient capillary force and specific surface area, which is beneficial for accelerating wetting and stabilizing liquid retention.

[0053] In some alternative embodiments, the electronic conductivity of the thick electrode sheet is ≥0.4 S / cm, preferably ≥0.5 S / cm.

[0054] In some optional embodiments, the liquid retention rate of the thick electrode sheet is ≥20 μL / mg. This ensures the continuity of the electrode conductive network and constructs a stable ion transport network.

[0055] In some optional embodiments, the global tortuosity of the thick electrode sheet is ≤3.5, preferably ≤3.0. Low tortuosity can maintain a high effective ion diffusion coefficient of the battery, ensuring the rate performance of the battery.

[0056] A second aspect of this application provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is a thick electrode sheet as described in any of the preceding claims.

[0057] Furthermore, the time for the electrolyte to completely immerse the thick electrode sheet is ≤40 min, preferably ≤30 min.

[0058] Specifically, the wetting time test method is as follows: a thick electrode sheet with a diameter of 14 mm is cut, and the thick electrode sheet is placed horizontally on an electronic balance. 10 μL of electrolyte is added to the center of the electrode sheet, and the mass-time curve is recorded. The point at which the mass stops increasing is the complete wetting time. The electrolyte composition is: 1.0 M LiPF6 dissolved in a mixed solvent with a volume ratio of EC:DMC:EMC=1:1:1, and 2 wt% vinylene carbonate (VC) is added as an additive.

[0059] Furthermore, the energy density of the battery is ≥260 Wh / kg. The conductive liquid phase contributes a reversible specific capacity (≥150 mAh / g), offsetting the decrease in the proportion of active material due to its addition. Calculations show that the NCM cathode with 2 wt% conductive liquid phase (capacity 250 mAh / g) has an actual energy density 8-12% higher than the electrode with 2 wt% insulating pore-forming agent.

[0060] Furthermore, the battery retains a capacity of >84% at 2C / 0.5C rates.

[0061] Furthermore, the battery retains >84% of its capacity after 500 cycles at 1C rate.

[0062] The technical solution of this application will be described below with reference to Examples 1-10 and Comparative Examples 1-4. Examples 2-10 and all comparative examples were prepared with some parameters modified from Example 1: Source of materials The main raw materials used in the embodiments and comparative examples of this application are sourced from the following: NCM811 cathode material: commercially available; Mesoporous carbon materials: prepared in the laboratory (using the soft template method) or commercially available; Polyvinylidene fluoride (PVDF): Commercially available; Carbon nanotubes (CNTs): Commercially available; Conductive carbon black (Super-P): Commercially available; Aluminum foil current collector: commercially available, 12 μm thick.

[0063] Example 1 This embodiment 1 provides a thick electrode sheet and a lithium-ion battery made from the thick electrode sheet: Preparation and characterization of conductive storage liquid phase Mesoporous carbon material MC-1 was prepared using a soft template method: A phenolic resin precursor and triblock copolymer F127 (soft template agent) were dissolved in ethanol at a mass ratio of 1:1 and stirred at 40°C for 2 hours to form a homogeneous solution. The solution was transferred to a petri dish, and the solvent was evaporated at room temperature for 48 hours, followed by pre-curing at 100°C for 12 hours. The cured sample was placed in a tube furnace and carbonized at 800°C under a nitrogen atmosphere by heating at 5°C / min for 3 hours. After cooling, the sample was ground to obtain mesoporous carbon MC-1. The physicochemical parameters of mesoporous carbon MC-1 were tested and are as follows: Most probable pore size: 25 nm; Total pore volume: 1.2 cm³ / g; Powder conductivity (10 MPa): 350 S / m; Reversible specific capacity (0.01-1.5 V vs. Li / Li) + ): 285 mAh / g.

[0064] Preparation of thick electrode sheets (positive electrode sheets) NCM811 cathode material, mesoporous carbon MC-1, carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 96.5:2.0:0.5:1.0. An appropriate amount of N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was dispersed and stirred in a vacuum mixer to control the slurry viscosity at 4000-6000 mPa·s and the solid content at 55-60%, forming a uniform and stable cathode slurry.

[0065] The above slurry was uniformly coated on both surfaces of an aluminum foil current collector (12 μm thick), with the coating density controlled at 25 mg / cm². The coated electrode was dried in a 120°C oven to remove the solvent, and then subjected to a rolling process to adjust the compaction density to 3.4 g / cm³ (approximately 94% of the theoretical maximum compaction density of NCM811, 3.6 g / cm³). Finally, the positive electrode was obtained through a die-cutting process.

[0066] Preparation of negative electrode Artificial graphite, conductive carbon black (Super-P), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 96:1:1.5:1.5. Deionized water was added as a solvent, and the mixture was stirred until homogeneous to obtain a negative electrode slurry. The slurry was coated onto the surface of a copper foil current collector, dried at 100℃, rolled, and slit to obtain the negative electrode sheet. The compaction density was controlled to be 1.6 g / cm³.

[0067] Battery assembly The prepared positive electrode, negative electrode, and separator (PP / PE / PP three-layer composite microporous membrane, 16 μm thick) were assembled into a bare battery cell using a winding process. The bare battery cell was placed in an aluminum-plastic film shell, and the electrolyte was injected in an argon-filled glove box with a dew point below -45°C. The electrolyte composition was: 1.0 M LiPF6 dissolved in a mixed solvent with a volume ratio of EC:DMC:EMC = 1:1:1, with 2 wt% vinylene carbonate (VC) added as an additive.

[0068] After being injected with electrolyte, the battery undergoes a 24-hour resting period, formation (0.05C constant current charging to 3.5V, then 0.1C constant current charging to 3.9V, and finally 0.2C constant current charging to 4.2V), aging, and capacity testing processes to finally obtain a soft-pack lithium-ion battery with a rated capacity of 2.5 Ah.

[0069] Performance test results Electrode physicochemical properties: Distribution of conductive liquid phase: SEM-EDS analysis showed that MC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 65%. The specific testing method was as follows: first, two-dimensional imaging of the electrode cross-section was performed using a scanning electron microscope, and then the NCM811 particles, conductive liquid phase particles (MC-1 particles), and free voids were distinguished by image segmentation. The area ratio of conductive liquid phase particles in the original gap region of NCM was directly counted to obtain the gap filling rate data.

[0070] Global tortuosity: 2.8; Electronic conductivity: 0.65 S / cm; Electrolyte wetting time: 22 min; Liquid retention rate: 28 μL / mg; Porosity: 32%, of which 78% are interconnected pores.

[0071] Battery electrochemical performance: Energy density: 268 Wh / kg; Capacity retention at 2C / 0.5C rates: 91.2%; Capacity retention after 500 cycles at 1C rate: 87.5%; After 500 cycles, the DCR growth rate was 18%.

[0072] Example 2 This embodiment 2 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 2 and embodiment 1 is that the proportion of the conductive storage liquid phase added is 0.1 wt%, and the rest of the preparation process is the same as that of embodiment 1.

[0073] Electrode formulation: NCM811 98.4 wt%, MC-1 0.1 wt%, CNT 0.5 wt%, PVDF 1.0 wt%. Performance test results: Conductive liquid phase distribution: SEM-EDS analysis showed that MC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 5%; Porosity: 30%, of which interconnected pores account for 55%; Global tortuosity: 3.5; Electronic conductivity: 0.52 S / cm; Soaking time: 38 min; Liquid retention rate: 22 μL / mg; Energy density: 266 Wh / kg; 2C rate retention rate: 84.5%; Retention rate after 500 cycles: 84.2%; The results show that even with a conductive liquid phase addition as low as 0.1 wt%, the electrode can still maintain a relatively low tortuosity and a fast wetting rate, and the battery performance is better than that of the control sample 1 without the addition of a conductive liquid phase.

[0074] Example 3 This embodiment 3 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 3 and embodiment 1 is that the proportion of the conductive storage liquid phase added is 0.5 wt%, and the rest of the preparation process is the same as that of embodiment 1.

[0075] Electrode formulation: NCM811 97.5 wt%, MC-1 0.5 wt%, CNT 0.5 wt%, PVDF 1.0 wt%. Performance test results: Conductive liquid phase distribution: SEM-EDS analysis showed that MC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 17%. Porosity: 30%, of which interconnected pores account for 57%; Global tortuosity: 3.1; Electronic conductivity: 0.58 S / cm; Soaking time: 28 min; Liquid retention rate: 25 μL / mg; Energy density: 267 Wh / kg; 2C rate retention rate: 88.3% Retention rate after 500 cycles: 86.1%; The results show that when the amount of conductive liquid phase added is 0.5 wt%, it can significantly improve the wettability and conductivity of the electrode, and the overall performance of the battery is close to that of Example 1.

[0076] Example 4 This embodiment 4 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 4 and embodiment 1 is that the proportion of the conductive storage liquid phase added is 3.0 wt%, and the rest of the preparation process is the same as that of embodiment 1.

[0077] Electrode formulation: NCM811 95.0 wt%, MC-1 3.0 wt%, CNT 0.5 wt%, PVDF 1.0 wt%. Performance test results: Conductive liquid phase distribution: SEM-EDS analysis showed that MC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 73%. Porosity: 33%, of which interconnected pores account for 82%; Global tortuosity: 2.6; Electronic conductivity: 0.72 S / cm; Soaking time: 18 min; Liquid retention rate: 31 μL / mg; Energy density: 270 Wh / kg; 2C rate retention rate: 92.5%; Retention rate after 500 cycles: 88.2%; The results show that appropriately increasing the content of the conductive reservoir phase can further reduce the tortuosity, shorten the wetting time and improve the liquid retention rate. Meanwhile, due to the capacity contribution of MC-1 itself, the energy density does not decrease significantly.

[0078] Example 5 This embodiment 5 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 5 and embodiment 1 is that the proportion of the conductive storage liquid phase added is 5.0 wt%. Electrode formulation: NCM811 93.0 wt%, MC-1 5.0 wt%, CNT 0.5 wt%, PVDF 1.0 wt%; The remaining preparation process is the same as in Example 1.

[0079] Performance test results: Distribution of conductive liquid phase: SEM-EDS analysis showed that MC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 85%; Porosity: 34%, of which interconnected pores account for 87%; Global tortuosity: 2.5; Electronic conductivity: 0.78 S / cm; Soaking time: 15 min; Liquid retention rate: 35 μL / mg; Energy density: 265 Wh / kg; 2C rate retention rate: 93.1%; Retention rate after 500 cycles: 89.5%; The results show that even with a high concentration of conductive reservoir phase (5.0 wt%), the electrode maintains excellent electrochemical performance. Although the proportion of the main active material decreases, the energy density remains high due to the significant contribution of MC-1 to the reversible specific capacity.

[0080] Example 6 This embodiment 6 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 6 and embodiment 1 is that the proportion of the conductive storage liquid phase added is 3.0 wt%. Electrode formulation: NCM811 95.0 wt%, MC-1 3.0 wt%, CNT 0.5 wt%, PVDF 1.0 wt%; Electrode parameters: Surface density: 35 mg / cm²; Compacted density: 3.4 g / cm³; The remaining preparation process is the same as in Example 1.

[0081] Performance test results: Conductive liquid phase distribution: SEM-EDS analysis showed that MC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 74%. Porosity: 32%, of which interconnected pores account for 78%; Global tortuosity: 2.9; Electronic conductivity: 0.68 S / cm; Soaking time: 26 min; Liquid retention rate: 31 μL / mg; Energy density: 278 Wh / kg; 2C ratio retention rate: 88.5%; Retention rate after 500 cycles: 85.2%; The results show that, under high areal density (35 mg / cm²), the addition of 3.0 wt% of conductive storage liquid phase can still achieve excellent rate performance and cycle stability, while obtaining higher energy density (278 Wh / kg).

[0082] Meanwhile, compared with Example 6 and Example 4, even with the areal density increased to 35 mg / cm², it still has a high 2C rate retention rate and 500-cycle retention rate.

[0083] Example 7 This embodiment 7 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 7 and embodiment 1 is that low-pore-volume porous carbon PC-1 (total pore volume 0.3 cm³ / g, conductivity 150 S / m, reversible specific capacity 220 mAh / g) is used instead of MC-1, and the rest of the preparation process is the same as that of embodiment 1.

[0084] Performance test results: Distribution of conductive liquid phase: SEM-EDS analysis showed that PC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 14%. Porosity: 30%, of which interconnected pores account for 55%; Global tortuosity: 3.2; Electronic conductivity: 0.61 S / cm; Soaking time: 32 min; Liquid retention rate: 24 μL / mg; Energy density: 269 Wh / kg; 2C ratio retention rate: 86.2%; Retention rate after 500 cycles: 85.8%; The results show that even when the total pore volume is 0.3 cm³ / g (close to the lower limit of 0.2 cm³ / g), the conductive liquid phase can still improve wettability and conductivity, and the battery performance is better than that of the comparative example.

[0085] Example 8 This embodiment 8 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 8 and embodiment 1 is that high-pore-volume porous carbon PC-2 (total pore volume 2.0 cm³ / g, conductivity 80 S / m, reversible specific capacity 180 mAh / g) is used instead of MC-1, and the rest of the preparation process is the same as that of embodiment 1.

[0086] Performance test results: Distribution of conductive liquid phase: SEM-EDS analysis showed that PC-2 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 79%. Porosity: 35%, of which interconnected pores account for 83%; Global tortuosity: 2.7; Electronic conductivity: 0.55 S / cm; Soaking time: 20 min; Liquid retention rate: 33 μL / mg; Energy density: 262 Wh / kg; 2C ratio retention rate: 89.8%; Retention rate after 500 cycles: 87.1%; The results show that the high-porosity conductive liquid phase provides superior liquid storage capacity and faster wetting rate. Although the conductivity is relatively low (80 S / m), it can still meet the conductivity requirements of thick electrode sheets.

[0087] Example 9 This embodiment 9 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 9 and embodiment 1 is that nitrogen-doped porous carbon NC-1 (total pore volume 0.8 cm³ / g, conductivity 50 S / m, reversible specific capacity 260 mAh / g, nitrogen content 5 at%) is used instead of MC-1. The rest of the preparation process is the same as that of embodiment 1.

[0088] Performance test results: Distribution of conductive liquid phase: SEM-EDS analysis showed that NC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 58%. Porosity: 31%, of which interconnected pores account for 75%; Global tortuosity: 3.0; Electronic conductivity: 0.48 S / cm; Soaking time: 25 min; Liquid retention rate: 27 μL / mg; Energy density: 267 Wh / kg; 2C ratio retention rate: 87.5%; Retention rate after 500 cycles: 86.3%; The results show that even under conditions where the conductivity is at the lower limit (50 S / m), nitrogen-doped porous carbon can still effectively improve the overall performance of thick electrode sheets. The defect sites introduced by nitrogen doping are beneficial to lithium-ion transport, compensating for the relatively low conductivity.

[0089] Example 10 This embodiment 10 provides a thick electrode sheet and a lithium-ion battery. The difference between embodiment 10 and embodiment 1 is that, except for the use of graphene aerogel microspheres (total pore volume 0.5 cm³ / g, conductivity 200 S / m, specific surface area 350 m² / g) to replace MC-1, the rest of the preparation process is the same as that of embodiment 1.

[0090] Performance test results: Distribution of conductive liquid phase: SEM-EDS analysis showed that graphene aerogel microspheres were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 22%. Porosity: 30%, of which interconnected pores account for 71%; Global tortuosity: 2.9; Electronic conductivity: 0.70 S / cm; Soaking time: 24 min; Liquid retention rate: 26 μL / mg; Energy density: 271 Wh / kg; 2C rate retention rate: 90.1%; Retention rate after 500 cycles: 87.8%; The results show that graphene aerogel microspheres, as a conductive liquid reservoir, can also significantly improve the performance of thick electrode sheets, verifying the universality of the technical solution in this application.

[0091] Comparative Example 1 (non-conductive reservoir phase) Comparative Example 1 provides a thick electrode sheet and a lithium-ion battery. The difference between Comparative Example 1 and Example 1 is that the electrode sheet formulation is: NCM811 98.5 wt%, CNT 0.5 wt%, PVDF 1.0 wt%. The remaining preparation process is the same as in Example 1.

[0092] Performance test results: Porosity: 30%; Global tortuosity: 4.8; Electronic conductivity: 0.45 S / cm; Soaking time: 145 min; Liquid retention rate: 18 μL / mg; Percentage of interconnected pores: 45%; Energy density: 265 Wh / kg; 2C ratio retention rate: 78.5%; Retention rate after 500 cycles: 79.3%; Compared to Example 1, the electrode without the added conductive reservoir phase exhibited extremely high tortuosity (4.8) and extremely long immersion time (145 min), resulting in a significant decrease in battery rate performance and cycle stability.

[0093] Comparative Example 2 (Insulating Pore-forming Agent) Comparative Example 2 provides a thick electrode sheet and a lithium-ion battery. The difference between Comparative Example 2 and Example 1 is that the electrode sheet formulation is: NCM811 95.5 wt%, mesoporous SiO2 3.0 wt%, CNT 0.5 wt%, PVDF 1.0 wt%. Mesoporous SiO2 has a pore volume of 1.0 cm³ / g, but it is an insulator (conductivity ≈ 0) and does not contribute to electrochemical capacity.

[0094] The remaining preparation process is the same as in Example 1.

[0095] Performance test results: Mesoporous SiO2 distribution: SEM-EDS analysis showed that mesoporous SiO2 particles filled the gaps between NCM811 particles, with a gap filling rate of approximately 60%. Porosity: 30%, of which interconnected pores account for 70%; Global tortuosity: 4.2; Electronic conductivity: 0.28 S / cm (significantly reduced); Soaking time: 35 min; Liquid retention rate: 22 μL / mg; Energy density: 248 Wh / kg (SiO2 does not contribute to capacity); 2C ratio retention rate: 72.3%; Retention rate after 500 cycles: 76.8%; Compared to Example 4 (also with an addition of 3.0 wt%), while the use of an insulating pore-forming agent improved wettability, it severely compromised conductivity, leading to a significant decrease in electrode conductivity and a substantial reduction in battery energy density and power performance. This fully demonstrates the technical advantages of conductive storage phases over traditional insulating pore-forming agents.

[0096] Comparative Example 3 (Non-porous conductive agent) Comparative Example 3 provides a thick electrode sheet and a lithium-ion battery. The difference between Comparative Example 3 and Example 1 is that non-porous graphene (conductivity 500 S / m, no liquid storage capacity) is used instead of MC-1, and the rest of the preparation process is the same as that of Example 1.

[0097] Electrode formulation: NCM811 96.5 wt%, non-porous graphene 2.0 wt%, CNT 0.5 wt%, PVDF 1.0 wt%.

[0098] Performance test results: Distribution of non-porous graphene: SEM-EDS analysis showed that non-porous graphene filled the gaps between NCM811 particles, with a gap filling rate of approximately 7%. Porosity: 29%, of which interconnected pores account for 43%; Global tortuosity: 4.5; Electronic conductivity: 0.82 S / cm (relatively high); Soaking time: 125 min; Liquid retention rate: 19 μL / mg; Energy density: 269 Wh / kg 2C ratio retention rate: 80.2%; Retention rate after 500 cycles: 81.5%; Compared to Example 1, while non-porous graphene provides excellent conductivity, its lack of liquid storage capacity severely reduces electrode wettability and liquid retention, resulting in poor battery rate performance and cycle stability. This indicates that materials with only conductivity but no porosity cannot meet the requirements for synergistically optimizing the electrical and wettability properties of thick electrode sheets.

[0099] Comparative Example 4 (Low Areal Density - Thin Electrode Sheet) Comparative Example 4 provides a thick electrode sheet and a lithium-ion battery. The difference between Comparative Example 4 and Example 1 is that, except that the coating surface density is adjusted to 12 mg / cm², the rest of the preparation process is the same as that of Example 1.

[0100] Performance test results: Conductive liquid phase distribution: SEM-EDS analysis showed that MC-1 particles were uniformly filled in the gaps between NCM811 particles, with a gap filling rate of approximately 72%. Porosity: 33%, of which interconnected pores account for 87%; Global tortuosity: 2.2; Electronic conductivity: 0.70 S / cm; Soaking time: 15 min; Liquid retention rate: 20 μL / mg; Energy density: 245 Wh / kg; 2C rate retention rate: 94.5%; Retention rate after 500 cycles: 88.8%; Under low areal density conditions (12 mg / cm² < 15 mg / cm²), even with the addition of a conductive storage phase, the electrode itself exhibits low tortuosity and good wettability due to its low areal density. However, due to the relatively increased proportion of inactive materials such as current collectors, the battery energy density (245 Wh / kg) is significantly lower than that of Example 1 (268 Wh / kg), failing to demonstrate the advantages of thick electrode technology.

[0101] Experimental Examples The main testing methods involved in this application are as follows: (1) Parameter testing of conductive liquid phase powder Pore ​​volume testing: The pore volume and pore size distribution of the powder were tested using mercury intrusion porosimetry or nitrogen adsorption-desorption (BET). Before testing, the sample was degassed under vacuum at 150°C for 4 hours.

[0102] Conductivity test: The powder sample was placed into an insulating mold and compacted with a pressure of 10 MPa. The resistivity was measured using the four-probe method, and the conductivity was calculated as σ = 1 / ρ.

[0103] Reversible specific capacity test: A coin cell (with lithium metal as the counter electrode) was prepared by a conductive liquid phase and charged and discharged at a rate of 0.1C within a voltage range of 0.01V to 3.0V. The reversible specific capacity was recorded.

[0104] (2) Electrode performance testing Global tortuosity test (DC limiting current method): Assemble a symmetrical battery: stainless steel | electrode | electrolyte | electrode | stainless steel. Apply a 10 mV DC voltage and record the steady-state current I_lim. Calculate the tortuosity: τ = (I_lim × L) / (n × F × D × C × A), where L is the electrode thickness, D is the ion diffusion coefficient, C is the electrolyte concentration, and A is the electrode area.

[0105] Electronic conductivity test (four-probe method): Cut the electrode into 40 mm × 40 mm pieces, use a four-probe instrument to measure the surface resistance R_s, and calculate the conductivity: σ = 1 / (R_s × t), where t is the electrode thickness.

[0106] Wetting time test: Cut a thick electrode sheet with a diameter of 14 mm, an areal density of 25 mg / cm², and a compaction density of 3.4 g / cm³. Place the thick electrode sheet horizontally on an electronic balance and add 10 μL of electrolyte (1.0 M LiPF6 dissolved in a mixed solvent with a volume ratio of EC:DMC:EMC=1:1:1, with an additional 2 wt% of vinylene carbonate (VC) as an additive) to the center of the electrode sheet. Record the mass-time curve. The point at which the mass stops increasing is the complete wetting time.

[0107] Liquid retention rate test: Weigh the dry electrode mass m0, immerse it in the electrolyte for 24 hours, remove it and use filter paper to absorb the surface droplets, weigh m1, liquid retention rate = (m1- m0) / m0 (μL / mg).

[0108] (3) Battery performance test Energy density test: The battery is charged at a constant current rate of 0.5C to the cutoff voltage, then charged at a constant voltage rate to the cutoff current, and finally discharged at a constant current rate of 0.5C to the cutoff voltage. The energy density is calculated based on the discharge capacity, discharge voltage plateau, and battery mass.

[0109] Rate performance test: At 25℃, the battery is fully charged at a rate of 0.5C, and then discharged to the cutoff voltage at rates of 0.5C, 1C, and 2C respectively. The discharge capacity at different rates is recorded, and the rate capacity retention rate is calculated as (2C capacity / 0.5C capacity) × 100%.

[0110] Cyclic performance test: Referring to GB / T 31484-2015 standard, under a constant temperature environment of 25℃ or 45℃, the battery is charged at a constant current rate of 1C to the cutoff voltage, then charged at a constant voltage rate to 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 1C to the cutoff voltage. The above steps are repeated for cyclic testing. Capacity retention rate = (Discharge capacity of the Nth cycle / Discharge capacity of the 1st cycle) × 100%.

[0111] DCR test: Adjust the battery to 50% SOC state and discharge it with a 1C current pulse for 10 seconds at 25℃. Calculate the DC internal resistance R = ΔV / I1 based on the voltage drop ΔV.

[0112] The test results are shown in Table 1: Table 1-1 Summary of Performance of Examples 1-7 Table 1-2 Performance Summary Table of Examples 8-10 and Comparative Examples 1-4 The following conclusions can be drawn from the data in Tables 1-1 and 1-2: (1) Effect of conductive liquid phase content Comparing Examples 1-5, it can be seen that as the content of the conductive liquid phase increases (0.1-5.0 wt%), the global tortuosity of the electrode gradually decreases from 3.5 to 2.5, the immersion time shortens from 38 min to 15 min, and the liquid retention rate increases from 22 μL / mg to 35 μL / mg. When the content is in the range of 0.5-3.0 wt%, the overall performance of the battery reaches the optimal balance; when the content is too low (0.1 wt%), the improvement effect is limited, and when the content is too high (5.0 wt%), although the performance is excellent, the proportion of active material decreases.

[0113] (2) Influence of physical property parameters of conductive liquid phase Comparing Examples 1, 7, 8, and 9, it can be seen that the pore volume and conductivity of the conductive reservoir phase have a significant impact on electrode performance. The high-pore-volume material (Example 8, 2.0 cm³ / g) provides faster wetting speed and higher liquid retention; the high-conductivity material (Example 1, 350 S / m) provides better electronic conductivity. Even under boundary conditions (pore volume 0.3 cm³ / g in Example 7, conductivity 50 S / m in Example 9), the conductive reservoir phase still significantly improves electrode performance, with a 2C rate retention rate >84% and a 500-cycle retention rate >84%.

[0114] (3) Comparative Analysis Compared with Comparative Example 1 (without conductive reservoir phase), all examples containing conductive reservoir phase exhibited significantly lower tortuosity (2.5-3.5 vs. 4.8) and shorter immersion time (15-38 min vs. 145 min), resulting in a substantial improvement in battery rate performance and cycle stability.

[0115] Compared with Comparative Example 2 (insulating pore-forming agent SiO2), Example 4 (also with an addition amount of 3.0 wt%) showed significant advantages in conductivity, energy density and electrochemical performance, proving that "conductivity" is a key feature that distinguishes conductive reservoir phases from traditional pore-forming agents.

[0116] Compared with Comparative Example 3 (non-porous conductive agent), Example 1 is significantly superior to the non-porous conductive agent in terms of wettability and liquid retention, demonstrating that "porosity" is a key feature that distinguishes conductive reservoir phases from conventional conductive agents.

[0117] Compared with Comparative Example 4 (electrode sheet of ordinary thickness), when the areal density is below the threshold defined in this invention (<15 mg / cm²), even the addition of a conductive reservoir phase cannot demonstrate the high energy density advantage of the thick electrode sheet. This verifies that the addition of a conductive reservoir phase in this application is a technical solution for the specific technical problem of "thick electrode sheet".

[0118] In summary, this application effectively solves the impossible triangle problem of "high energy density-high power density-long cycle life" in thick electrode technology by introducing a conductive reservoir phase that simultaneously possesses porosity, conductivity, and electrochemical activity into a high-pressure, thick electrode sheet. This has significant technological advancements and industrial application value.

[0119] The thick electrode sheet containing a conductive liquid phase provided in this application can be widely used in the field of lithium-ion battery manufacturing, and is particularly suitable for power batteries and energy storage batteries with high requirements for energy density and power density. Lithium-ion batteries manufactured using the technical solution of this application can achieve an energy density of 260-280 Wh / kg, while maintaining good rate performance and long cycle life, meeting the dual requirements of electric vehicle range and fast charging performance.

[0120] Although embodiments of this implementation have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this implementation, the scope of which is defined by the claims and their equivalents.

Claims

1. A thick electrode sheet, comprising a current collector and an active material layer coated on the current collector, characterized in that, The active material layer includes a main active material, a binder, a conductive agent, and a conductive reservoir phase. The conductive reservoir phase includes one or more of mesoporous carbon materials, graphene aerogel microspheres, and nitrogen-doped porous carbon. The conductive reservoir phase accounts for 0.05-10.0 wt% of the mass of the active material layer. The areal density of the active material layer is ≥15 mg / cm².

2. The thick electrode sheet according to claim 1, characterized in that, The conductive liquid phase accounts for 0.1-5 wt% of the active material layer, and the conductive liquid phase satisfies at least one of the following characteristics: a: under a compaction pressure of 10 MPa, the total pore volume of the conductive liquid phase powder is ≥0.2 cm³ / g; b: under a compaction pressure of 10 MPa, the electronic conductivity of the conductive liquid phase powder is ≥10 S / m. c: in 0.01 V-3.0 V (vs. Li / Li) + Within the voltage range of ), the reversible specific capacity of the conductive liquid phase is ≥100mAh / g.

3. The thick electrode sheet according to claim 1 or 2, characterized in that, The compaction density D of the thick electrode sheet is similar to the theoretical maximum compaction density D of the main active material. max Satisfy: D≥80%D max .

4. The thick electrode sheet according to claim 1, characterized in that, The main active substance accounts for 88.0-98.9 wt% of the mass of the active substance layer.

5. The thick electrode sheet according to claim 2, characterized in that, The surface density ρ of the active material layer 面 The total pore volume of the conductive liquid phase powder is 0.5-2.5 cm³ / g under a compaction pressure of 10 MPa, which is 20-50 mg / cm².

6. The thick electrode sheet according to claim 1 or 2, characterized in that, When the conductive liquid phase comprises a mesoporous carbon material, the mesoporous carbon material has a most probable pore size of 10-50 nm.

7. The thick electrode sheet according to claim 1 or 2, characterized in that, The thick electrode sheet satisfies at least one of the following characteristics: d: The electronic conductivity of the thick electrode sheet is ≥0.4 S / cm; e: the liquid retention rate of the thick electrode sheet is ≥20μL / mg; f: the global tortuosity of the thick electrode sheet is ≤3.

5.

8. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, At least one of the positive electrode and the negative electrode is a thick electrode sheet as described in any one of claims 1-7.

9. The lithium-ion battery according to claim 8, characterized in that, The electrolyte must completely immerse the thick electrode sheet for ≤40 min.

10. The lithium-ion battery according to claim 8, characterized in that, The energy density of the battery is ≥260 Wh / kg, and the capacity retention rate of the battery is >84% at 2C / 0.5C rate and >84% after 500 cycles at 1C rate.

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