Aluminum-based current collector for solid-state negative electrode-free sodium battery and preparation method thereof
By employing a method of cold pressing with a graded distribution of coarse and fine aluminum particles and an in-situ modified sodium fluoroaluminate layer on the surface in a solid-state sodium-anode-free battery, a gradient aluminum-based composite current collector that balances density and volume buffering was constructed. This solved the problems of poor interfacial contact, sodium trapping, and dendrite growth in the current collector, thereby improving battery performance and reducing manufacturing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGYIN NANOPORE INNOVATIVE MATERIALS TECH LTD
- Filing Date
- 2026-04-03
- Publication Date
- 2026-05-29
AI Technical Summary
Existing solid-state sodium-based negative electrode batteries cannot simultaneously achieve both compactness and volume buffering capacity in their current collectors, leading to problems such as increased interfacial impedance, sodium dendrite growth, poor cycle stability, and complex and costly fabrication processes.
A gradient aluminum substrate with a dense surface and porous inner layer is constructed by using a graded cold pressing process of coarse and fine aluminum particles. A binder-free sodium fluoroaluminate modified layer is grown in situ on the surface to form a gradient pore structure. The preparation process is simplified by combining room temperature cold pressing and in-situ hydrolysis reaction.
It achieves the dual functions of dense fluid and sodium-loving interface, improves the cycle stability, critical current density and coulombic efficiency of battery, reduces manufacturing cost, and is compatible with existing large-scale production lines.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, and more specifically to an aluminum-based current collector for use in solid-state sodium-based batteries without negative electrodes and its preparation method. Background Technology
[0002] Sodium-ion batteries without a negative electrode significantly improve energy density and effectively reduce manufacturing costs by eliminating the sodium metal negative electrode required in traditional batteries, and are widely recognized as the core development direction of next-generation low-cost energy storage technology. In particular, solid-state sodium-ion batteries without a negative electrode have significant advantages such as no leakage, high safety, and high energy density, which can be highly matched with the stability and safety requirements of large-scale energy storage systems, high-end portable electronic devices, and other application scenarios.
[0003] However, this technology is still in a critical breakthrough phase, and its industrial application is largely constrained by the performance of the current collector materials. Traditional current collectors generally employ a single structure, making it difficult to address multiple challenges: on the one hand, dense structures cannot buffer the dramatic volume expansion caused by sodium deposition, easily leading to microcracks and gaps at the solid-solid interface, resulting in a surge in interfacial impedance; on the other hand, while porous structures possess some buffering capacity, excessive porosity can easily cause sodium metal capture, forming irreversible dead sodium and severely impairing coulombic efficiency. Simultaneously, the inherently insufficient sodium affinity of the current collector surface leads to uneven sodium deposition distribution, easily inducing sodium dendrite growth, which can directly penetrate the solid electrolyte layer, causing internal short circuits in the battery and significantly threatening cycle life and operational safety.
[0004] Current mainstream current collector modification technologies have significant limitations: one type is based on three-dimensional porous structure design, which, while mitigating the volume effect to some extent, faces extreme difficulty in controlling porosity and still struggles to eliminate the risk of sodium trapping; moreover, the complex preparation process significantly increases the cost burden. Another type involves modification schemes using surface coating or binder-loaded sodium-loving materials. These methods are prone to introducing impurities and triggering side reactions, and their effect on improving the interfacial compatibility of the solid-state electrolyte is limited, failing to fundamentally optimize interfacial matching. Existing technologies cannot simultaneously achieve both density and volume buffering capacity, making it difficult to meet the core principles of stable electrolyte, tight interface, dense electrolyte, and dense fluid. This has become the main problem hindering the large-scale application of solid-state anode-free sodium batteries. Summary of the Invention
[0005] The purpose of this invention is to solve the technical problems related to interfacial contact, sodium deposition, preparation process and cost of existing solid-state sodium-free battery current collectors, and to provide an aluminum-based composite current collector and its modification method that can realize the dual functions of dense fluid and sodium-loving interface and is adapted to solid-state sodium-free batteries, so as to improve battery performance and promote its industrialization.
[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides an aluminum-based current collector for a solid-state sodium-based battery without a negative electrode, comprising a gradient aluminum-based substrate and a sodium fluoroaluminate modified layer grown in situ on the surface of the gradient aluminum-based substrate; The gradient aluminum-based substrate has a gradient pore structure with a dense surface layer and a porous inner layer, wherein the surface porosity is ≤3% and the inner layer porosity is 5~8%; The thickness of the gradient aluminum substrate is 70~110μm, the thickness of the sodium fluoroaluminate modified layer is 1~3μm, and the sodium fluoroaluminate modified layer is bonded to the gradient aluminum substrate in situ without adhesive.
[0007] To optimize the above technical solution, the specific limitations also include: The gradient aluminum-based substrate is formed by cold pressing a graded mixture of coarse and fine aluminum particles. The coarse aluminum particles have a particle size of 50~100μm, and the fine aluminum particles have a particle size of 5~20μm; The surface material of the gradient aluminum-based substrate is made of only fine aluminum particles, while the inner material is a mixture of coarse and fine aluminum particles in a mass ratio of 3 to 5:1.
[0008] Furthermore, the surface layer thickness of the gradient aluminum substrate is 20~30μm, and the inner layer thickness is 50~80μm.
[0009] Furthermore, both the surface material and the inner material contain 0.5-1% aluminum powder dispersant by mass; the aluminum powder dispersant is at least one of zinc stearate or magnesium stearate.
[0010] The second aspect of this application provides a method for preparing an aluminum-based current collector for a solid-state sodium-based negative electrode battery, comprising the following steps: S1: Using a layered feeding cold pressing molding process, inner layer material is fed into the bottom layer of the mold, and a separator is set on the surface of the inner layer material to divide the mold cavity into an inner layer area and a surface area; surface material is fed into the surface area, and then cold pressing is performed to obtain an aluminum base with a gradient porosity structure; after removing the separator and shaping, the formed gradient aluminum base is demolded. S2: Immerse the gradient aluminum-based substrate obtained in step S1 into an aqueous solution containing fluoride, so that the aluminum particles on the surface of the substrate undergo an in-situ hydrolysis reaction with the fluoride to generate a sodium fluoroaluminate modified layer; after the reaction is completed, clean and vacuum dry to obtain an aluminum-based current collector for solid-state sodium-based batteries without negative electrodes.
[0011] Further, the specific process parameters for cold pressing in step S1 are as follows: the cold pressing temperature is controlled at 25~30℃; after feeding, the material is first pre-pressed at a pre-pressure of 5~8MPa for 2~3 minutes, then pressurized to the rated pressure of 12~15MPa and held for 5~10 minutes; after removing the separator, the pressure is first increased to the rated pressure of 10~13MPa and held for 5~10 minutes, then slowly increased to 17~22MPa and held for 8~15 minutes before demolding; the pressure fluctuation during the holding process is controlled within ±0.5MPa.
[0012] Furthermore, in step S1, after demolding, the surface layer thickness, inner layer thickness, and porosity of the substrate are measured: If the surface porosity is >3%, increase the cold pressing pressure or extend the holding time and then re-cold press; If the inner layer porosity is <5%, reduce the cold pressing pressure or reduce the holding time and then re-cold press; If the inner layer porosity is >8%, adjust the mass ratio of coarse and fine aluminum particles in the inner layer material and then re-cold press. The surface layer thickness is controlled at 20~30μm, the inner layer thickness at 50~80μm, the surface porosity is ≤3%, and the inner layer porosity is 5~8%.
[0013] Further, in step S2, the concentration of fluoride in the aqueous solution containing fluoride is 0.1~0.3 mol / L, and the fluoride is one or a mixture of two of NH4F and NaF. The gradient aluminum-based substrate is immersed in the aqueous solution containing fluoride and reacted at 30~50℃ for 2~4 h. The vacuum drying conditions are: temperature 80~100℃, vacuum degree 0.08~0.1MPa, and drying time 2~3 h.
[0014] A third aspect of this application provides a solid-state sodium-based battery without a negative electrode, comprising the aforementioned aluminum-based current collector for a solid-state sodium-based battery without a negative electrode as the negative electrode current collector.
[0015] The battery also includes an NBH solid electrolyte and a NaCrO2 cathode.
[0016] Compared with the prior art, the beneficial effects of the present invention are: The solution of this invention addresses the core technical problems of existing solid-state sodium-based anode-free batteries, such as poor contact at the current collector interface, unreasonable porosity, sodium dendrite growth, and complex and costly fabrication processes. The present invention employs a cold-pressing process with graded coarse and fine aluminum particles to construct a gradient aluminum substrate with a dense surface and a porous inner layer, thus resolving the contradiction between density and volume buffering capacity in traditional current collectors. The dense surface structure effectively prevents sodium metal capture, reduces dead sodium generation, and addresses the issue of decreased coulombic efficiency in porous current collectors. The porous inner structure efficiently buffers volume expansion during sodium deposition, overcoming the inability of a single uniformly dense current collector to cope with volume changes, and significantly improving battery cycle stability. Simultaneously, a sodium fluoroaluminate modified layer is grown in situ on the surface of the gradient aluminum substrate without the need for binders. This avoids side reactions caused by impurities introduced by binders, significantly improves the interfacial compatibility between the current collector and the solid electrolyte, reduces interfacial impedance, and guides uniform sodium nucleation, effectively inhibiting sodium dendrite growth and eliminating the risk of short circuits caused by dendrites piercing the solid electrolyte.
[0017] At the process level, this invention adopts a combination of room temperature cold pressing molding and in-situ hydrolysis reaction, which eliminates the need for high-temperature sintering. The preparation process is simple and the equipment cost is low. It can be directly adapted to existing large-scale production lines for aluminum-based current collectors, significantly reducing the preparation cost and facilitating industrialization.
[0018] Performance tests show that the solid-state sodium-anode-free battery assembled using this composite current collector exhibits significantly better overall performance than existing single dense or porous aluminum current collectors. In summary, the solution of this invention achieves the dual functions of a dense current collector and a sodium-loving interface, highly meeting the requirements of stable electrolyte, dense interface, dense electrolyte, and dense current collector in solid-state sodium-anode-free batteries. This effectively improves the battery's cycle stability, critical current density, and high areal capacity adaptability, providing an efficient and low-cost current collector foundation for the industrial application of solid-state sodium-anode-free batteries. Detailed Implementation
[0019] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.
[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.
[0021] This invention provides an aluminum-based current collector for solid-state sodium-based batteries without negative electrodes, comprising a gradient aluminum-based substrate and a sodium fluoroaluminate modified layer grown in situ on the surface of the gradient aluminum-based substrate. The gradient aluminum-based substrate has a gradient pore structure with a dense surface layer and a porous inner layer, wherein the surface porosity is ≤3% and the inner layer porosity is 5~8%; The thickness of the gradient aluminum substrate is 70~110μm, the thickness of the sodium fluoroaluminate modified layer is 1~3μm, and the sodium fluoroaluminate modified layer is bonded to the gradient aluminum substrate in situ without adhesive.
[0022] This invention breaks through the technical bottleneck of existing solid-state sodium-based battery current collectors without negative electrodes, and prepares a high-density gradient aluminum-based composite current collector. It adopts coarse and fine aluminum particle gradation and cold pressing to construct a gradient pore structure with a dense surface layer and a porous inner layer, thus solving the contradiction between density and volume buffer. A binder-free sodium fluoroaluminate modified layer is grown in situ on the surface of the current collector to improve interfacial compatibility and inhibit sodium dendrite growth.
[0023] The dense surface layer effectively prevents sodium metal capture, reduces dead sodium formation, and solves the problem of decreased coulombic efficiency caused by excessive porosity in porous current collectors. The porous inner layer buffers the volume expansion during sodium deposition, overcoming the challenge of single, uniformly dense fluids failing to cope with volume changes, achieving a dual balance between density and volume buffering. The binder-free in-situ sodium fluoroaluminate modified layer avoids side reactions caused by impurities introduced by binders, improves the interfacial compatibility between the current collector and the solid electrolyte, reduces interfacial impedance, guides uniform sodium nucleation, inhibits sodium dendrite growth, and eliminates the risk of short circuits caused by dendrites piercing the solid electrolyte, significantly improving the battery's cycle stability, safety, and critical current density. Furthermore, the limited overall thickness and modified layer thickness ensure that the current collector is compatible with the structural design of solid-state sodium-based batteries without negative electrodes, balancing energy density and structural stability.
[0024] In some embodiments, the gradient aluminum substrate is cold-pressed from a graded mix of coarse and fine aluminum particles; The coarse aluminum particles have a particle size of 50~100μm, and the fine aluminum particles have a particle size of 5~20μm. The surface material of the gradient aluminum base is made of only fine aluminum particles, while the inner material is a mixture of coarse and fine aluminum particles in a mass ratio of 3 to 5:1.
[0025] Fine aluminum particles, with their small size, can form a dense surface layer upon stacking, preventing sodium capture. Coarse aluminum particles, with their larger size, can create appropriate gaps within the structure after being graded with fine aluminum particles, controlling the inner layer porosity and achieving a volume buffering function. Furthermore, the particle gradation design allows for differentiation between surface and inner layer porosity without complex processes, avoiding the problems of complex fabrication processes and difficulty in controlling porosity in existing three-dimensional porous structures. This simplifies the fabrication process, reduces production costs, and ensures the stability and consistency of the gradient structure.
[0026] The surface layer of the gradient aluminum substrate has a thickness of 20~30μm, and the inner layer has a thickness of 50~80μm.
[0027] The surface layer thickness is controlled at 20-30 μm to ensure both surface density (sufficient packing of fine aluminum particles) and prevent insufficient density and increased sodium trapping risk due to an excessively thin surface layer, while also preventing excessive space occupation and impact on battery energy density due to an excessively thick surface layer. The inner layer thickness is controlled at 50-80 μm to ensure sufficient pore space to buffer the volume expansion of sodium deposition, preventing insufficient buffering capacity and current collector deformation due to an excessively thin inner layer, while also preventing an increase in the overall weight of the current collector and a decrease in energy density due to an excessively thick inner layer. This thickness range makes the structure of the gradient aluminum substrate more reasonable, balancing density, buffering capacity, and energy density.
[0028] Both the surface material and the inner material contain 0.5% to 1% aluminum powder dispersant by mass; the aluminum powder dispersant is at least one of zinc stearate or magnesium stearate.
[0029] The addition of dispersants effectively prevents the agglomeration of coarse and fine aluminum particles, ensuring uniform accumulation of fine aluminum particles on the surface and guaranteeing that the surface porosity meets requirements, thus avoiding uneven surface density caused by particle agglomeration. Simultaneously, it ensures uniform mixing of coarse and fine aluminum particles in the inner layer, controlling the porosity and preventing excessively high or low local porosity from affecting the buffering effect. Furthermore, dispersants can improve the integrity and adhesion of the substrate after cold pressing, preventing delamination and powdering during demolding.
[0030] This invention also provides a method for preparing an aluminum-based current collector for a solid-state sodium-based negative electrode battery, comprising the following steps: S1: A layered feeding cold pressing process is adopted. Inner layer material is fed into the bottom layer of the mold, and a separator is set on the surface of the inner layer material to divide the mold cavity into an inner layer area and a surface area. Surface material is fed into the surface area, and then cold pressing is performed to obtain an aluminum base with a gradient porosity structure. After removing the separator and shaping, the formed gradient aluminum base is demolded. S2: Immerse the gradient aluminum-based substrate obtained in step S1 into an aqueous solution containing fluoride, so that the aluminum particles on the surface of the substrate undergo an in-situ hydrolysis reaction with the fluoride to generate a sodium fluoroaluminate modified layer; after the reaction is completed, clean and vacuum dry to obtain a high-density gradient aluminum-based composite current collector for solid-state sodium-based batteries without negative electrodes.
[0031] Among them, the layered feeding and isolation component separation settings can accurately control the distribution of surface and inner layer materials, avoid material mixing leading to gradient structure failure, and combined with cold pressing molding process, no high-temperature sintering is required, resulting in low energy consumption and simple equipment requirements, which can be directly adapted to existing aluminum-based current collector mass production lines.
[0032] The specific process parameters for cold pressing in step S1 are as follows: the cold pressing temperature is controlled at 25~30℃; after feeding, the material is first pre-pressed at a pre-pressure of 5~8MPa for 2~3 minutes, then the pressure is increased to the rated pressure of 12~15MPa and held for 5~10 minutes; after removing the separator, the pressure is first increased to the rated pressure of 10~13MPa and held for 5~10 minutes, then the pressure is slowly increased again to 17~22MPa and held for 8~15 minutes for demolding; the pressure fluctuation during the holding process is controlled within ±0.5MPa.
[0033] In step S1, after demolding, the surface layer thickness, inner layer thickness, and porosity of the substrate are measured: If the surface porosity is >3%, increase the cold pressing pressure or extend the holding time and then re-cold press; If the inner layer porosity is <5%, reduce the cold pressing pressure or reduce the holding time and then re-cold press; If the inner layer porosity is >8%, adjust the mass ratio of coarse and fine aluminum particles in the inner layer material and then re-cold press. The surface layer thickness is controlled at 20~30μm, the inner layer thickness at 50~80μm, the surface porosity is ≤3%, and the inner layer porosity is 5~8%.
[0034] This step, by establishing a detection and correction mechanism, addresses the issue of product non-compliance caused by parameter deviations during cold pressing, ensuring that all parameters of the gradient aluminum substrate meet the preset requirements: for excessive surface porosity, increasing the cold pressing pressure or extending the holding time can further improve surface density; for excessively low inner layer porosity, reducing the cold pressing pressure or shortening the holding time can increase the inner layer pore space; for excessively high inner layer porosity, adjusting the ratio of coarse to fine particles can optimize the inner layer pore distribution.
[0035] In step S2, the concentration of fluoride in the aqueous solution containing fluoride is 0.1~0.3mol / L, and the fluoride is one or a mixture of two of NH4F and NaF. The gradient aluminum-based substrate is immersed in the aqueous solution containing fluoride and reacted at 30~50℃ for 2~4h. The vacuum drying conditions are: temperature 80~100℃, vacuum degree 0.08~0.1MPa, and drying time 2~3h.
[0036] The present invention also provides a solid-state sodium-free negative electrode battery, comprising the above-mentioned high-density gradient aluminum-based composite current collector for solid-state sodium-free negative electrode batteries as the negative electrode current collector.
[0037] The battery also includes an NBH solid electrolyte and a NaCrO2 cathode.
[0038] Using the high-density gradient aluminum-based composite current collector of the present invention as the negative electrode current collector can solve the problems of poor interfacial contact, sodium dendrite growth, and poor cycle stability of existing solid-state sodium-free negative electrode current collectors: the gradient pore structure of the current collector can buffer sodium volume expansion and avoid sodium capture, and the modified layer can reduce interfacial impedance and suppress sodium dendrites. The two work together to significantly improve the cycle stability, critical current density and coulombic efficiency of the battery.
[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 A method for modifying aluminum-based current collectors for solid-state sodium-based batteries without negative electrodes, the specific steps of which are as follows: 1. Gradient Aluminum Substrate Preparation: The surface layer material consists only of fine aluminum particles with a particle size of 12μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80μm and fine aluminum particles with a particle size of 12μm, mixed at a mass ratio of 4:1. 0.8% magnesium stearate dispersant is added. A layered feeding and cold pressing process is employed. The inner layer material is fed into the bottom layer of the mold. Movable separators are placed on the surface of the inner layer material to divide the mold cavity into an inner layer area and a surface layer area. Fine aluminum particles are then fed into the surface layer. The cold pressing temperature is set at 27℃, initially with a pre-pressure of 5MPa. Pre-press for 2 minutes to allow the surface and inner layers to initially form and adhere tightly, preventing delamination; then slowly increase the pressure to the rated pressure of 12 MPa, hold for 8 minutes, remove the separator, and then slowly increase the pressure to 10 MPa, hold for 5 minutes to ensure a tight bond between the surface and inner layers; finally, slowly increase the pressure to 20 MPa, hold for 10 minutes, and demold to obtain the gradient aluminum-based substrate. The pressure was kept stable during the holding process. The gradient aluminum-based substrate has a surface layer thickness of 25 μm, an inner layer thickness of 65 μm, a surface porosity of 2.0%, and an inner layer porosity of 6.5%. 2. In-situ modification treatment: Prepare a NaF aqueous solution with a concentration of 0.2 mol / L, immerse the gradient aluminum-based substrate in the aqueous solution, react at 40℃ for 3 h, wash with deionized water 4 times after the reaction, and then dry at 90℃ and 0.09 MPa vacuum to obtain a composite current collector with a sodium fluoroaluminate modified layer thickness of 2 μm. 3. Battery assembly: Using this composite current collector as the negative electrode current collector, combined with NBH solid electrolyte and NaCrO2 positive electrode, a CR2032 type sodium-free solid battery is assembled under a pressure of 10MPa, with the water and oxygen content controlled at ≤1ppm.
[0040] Example 2 1. Preparation of gradient aluminum-based substrate: The surface layer material consists only of fine aluminum particles with a particle size of 12 μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 3:1. 0.8% magnesium stearate dispersant is added, and the mixture is cold-pressed in layers. The cold-pressing parameters are the same as in Example 1. The surface layer thickness of the gradient aluminum-based substrate is 25 μm, the inner layer thickness is 65 μm, the surface layer porosity is 2.4%, and the inner layer porosity is 6.2%. 2. In-situ modification treatment: completely consistent with Example 1, the thickness of the sodium fluoroaluminate modified layer is 2μm; 3. Battery assembly: Completely consistent with Example 1.
[0041] Example 3 1. Preparation of gradient aluminum-based substrate: The surface layer material consists only of fine aluminum particles with a particle size of 12 μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 5:1. 0.8% magnesium stearate dispersant is added, and the mixture is cold-pressed in layers. The cold-pressing parameters are the same as in Example 1. The surface layer thickness of the gradient aluminum-based substrate is 25 μm, the inner layer thickness is 65 μm, the surface layer porosity is 2.2%, and the inner layer porosity is 6.7%. 2. In-situ modification treatment: completely consistent with Example 1, the thickness of the sodium fluoroaluminate modified layer is 2μm; 3. Battery assembly: Completely consistent with Example 1.
[0042] Example 4 1. Preparation of gradient aluminum-based substrate: The surface layer material consists only of fine aluminum particles with a particle size of 12 μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 4:1. 0.8% magnesium stearate dispersant is added, and the mixture is cold-pressed in layers. The cold-pressing parameters are the same as in Example 1. The surface layer thickness of the gradient aluminum-based substrate is 25 μm, the inner layer thickness is 65 μm, the surface layer porosity is 3.0%, and the inner layer porosity is 6.5%. 2. In-situ modification treatment: completely consistent with Example 1, the thickness of the sodium fluoroaluminate modified layer is 2μm; 3. Battery assembly: Completely consistent with Example 1.
[0043] Example 5 1. Preparation of gradient aluminum-based substrate: The surface layer material consists only of fine aluminum particles with a particle size of 12 μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 4:1. 0.8% magnesium stearate dispersant is added, and the mixture is cold-pressed in layers. The cold-pressing parameters are the same as in Example 1. The gradient aluminum-based substrate has a surface layer thickness of 20 μm, an inner layer thickness of 65 μm, a surface layer porosity of 2.6%, and an inner layer porosity of 6.5%. 2. In-situ modification treatment: completely consistent with Example 1, the thickness of the sodium fluoroaluminate modified layer is 2μm; 3. Battery assembly: Completely consistent with Example 1.
[0044] Example 6 1. Preparation of gradient aluminum-based substrate: The surface layer material consists only of fine aluminum particles with a particle size of 12 μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 4:1. 0.8% magnesium stearate dispersant is added, and the mixture is cold-pressed in layers. The cold-pressing parameters are the same as in Example 1. The gradient aluminum-based substrate has a surface layer thickness of 30 μm, an inner layer thickness of 65 μm, a surface layer porosity of 2.4%, and an inner layer porosity of 6.5%. 2. In-situ modification treatment: completely consistent with Example 1, the thickness of the sodium fluoroaluminate modified layer is 2μm; 3. Battery assembly: Completely consistent with Example 1.
[0045] Example 7 1. Preparation of gradient aluminum-based substrate: The surface layer material consists only of fine aluminum particles with a particle size of 12 μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 4:1. 0.8% magnesium stearate dispersant is added, and the mixture is cold-pressed in layers. The cold-pressing parameters are the same as in Example 1. The gradient aluminum-based substrate has a surface layer thickness of 25 μm, an inner layer thickness of 50 μm, a surface layer porosity of 2.5%, and an inner layer porosity of 6.3%. 2. In-situ modification treatment: completely consistent with Example 1, the thickness of the sodium fluoroaluminate modified layer is 2μm; 3. Battery assembly: Completely consistent with Example 1.
[0046] Example 8 1. Preparation of gradient aluminum-based substrate: The surface layer material consists only of fine aluminum particles with a particle size of 12 μm, while the inner layer material consists of coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 4:1. 0.8% magnesium stearate dispersant is added, and the mixture is cold-pressed in layers. The cold-pressing parameters are the same as in Example 1. The gradient aluminum-based substrate has a surface layer thickness of 25 μm, an inner layer thickness of 80 μm, a surface layer porosity of 2.5%, and an inner layer porosity of 6.8%. 2. In-situ modification treatment: completely consistent with Example 1, the thickness of the sodium fluoroaluminate modified layer is 2μm; 3. Battery assembly: Completely consistent with Example 1.
[0047] Comparative Example 1 1. Preparation of gradient aluminum-based substrate: The surface material is the same as in Example 1. The inner layer uses coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 2:1, and 0.8% magnesium stearate dispersant is added. The material is fed in layers and cold-pressed. The cold-pressing parameters are the same as in Example 1. The surface layer thickness of the gradient aluminum-based substrate is 25 μm, the inner layer thickness is 65 μm, the surface porosity is 2.7%, and the inner layer porosity is 7.6%. 2. In-situ modification and assembly testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are the same as in Example 1.
[0048] Comparative Example 2 1. Preparation of gradient aluminum-based substrate: The surface material is the same as in Example 1. The inner layer uses coarse aluminum particles with a particle size of 80 μm and fine aluminum particles with a particle size of 12 μm, mixed at a mass ratio of 6:1, and 0.8% magnesium stearate dispersant is added. The material is fed in layers and cold-pressed. The cold-pressing parameters are the same as in Example 1. The surface layer thickness of the gradient aluminum-based substrate is 25 μm, the inner layer thickness is 65 μm, the surface porosity is 2.3%, and the inner layer porosity is 7.7%. 2. In-situ modification and assembly testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are the same as in Example 1.
[0049] Comparative Example 3 1. Preparation of Gradient Aluminum Substrate: The preparation process is the same as in Example 1, except that the cold pressing parameters are adjusted to increase the surface porosity of the gradient aluminum substrate to 4.0% and the inner porosity to 6.5%. Layered feeding and cold pressing are used at 27°C. Pre-pressing is performed at 5 MPa for 2 minutes, followed by increasing the pressure to 8 MPa and holding for 8 minutes. After removing the separator, the pressure is directly increased to 15 MPa and held for 15 minutes before demolding. The resulting substrate has a surface thickness of 25 μm, an inner layer thickness of 65 μm, and an inner layer coarse-to-fine particle mass ratio of 4:1. The dispersant is 0.8% magnesium stearate. 2. In-situ Modification and Assembly Testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are also the same as in Example 1.
[0050] Comparative Example 4 1. Preparation of gradient aluminum-based substrate: The preparation process is the same as in Example 1, except that the surface layer feed amount is adjusted to achieve a surface layer thickness of 18 μm and an inner layer thickness of 65 μm. The cold pressing parameters are the same as in Example 1. The mass ratio of coarse to fine particles in the inner layer is 4:1, and the dispersant is 0.8% magnesium stearate. The surface porosity of the gradient aluminum-based substrate is 3.2%, and the inner layer porosity is 6.6%. 2. In-situ modification and assembly testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are the same as in Example 1.
[0051] Comparative Example 5 1. Preparation of gradient aluminum-based substrate: The preparation process is the same as in Example 1, except that the surface layer feed amount is adjusted to achieve a surface layer thickness of 32 μm and an inner layer thickness of 65 μm. The cold pressing parameters are the same as in Example 1. The mass ratio of coarse to fine particles in the inner layer is 4:1, and the dispersant is 0.8% magnesium stearate. The surface porosity of the gradient aluminum-based substrate is 1.9%, and the inner layer porosity is 6.5%. 2. In-situ modification and assembly testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are the same as in Example 1.
[0052] Comparative Example 6 1. Preparation of gradient aluminum-based substrate: The preparation process is the same as in Example 1, except that the inner layer feed amount is adjusted to make the inner layer thickness 48μm and the surface layer thickness 25μm. The cold pressing parameters are the same as in Example 1. The mass ratio of coarse to fine particles in the inner layer is 4:1, and the dispersant is 0.8% magnesium stearate. The surface porosity of the gradient aluminum-based substrate is 2.5%, and the inner layer porosity is 6.1%. 2. In-situ modification and assembly testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are the same as in Example 1.
[0053] Comparative Example 7 1. Preparation of gradient aluminum substrate: The preparation process is the same as in Example 1, except that the inner layer feed amount is adjusted to make the inner layer thickness 85μm and the surface layer thickness 25μm. The cold pressing parameters are the same as in Example 1. The mass ratio of coarse to fine particles in the inner layer is 4:1, and the dispersant is 0.8% magnesium stearate. The surface porosity of the gradient aluminum substrate is 2.7%, and the inner layer porosity is 7.4%. 2. In-situ modification and assembly testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are the same as in Example 1.
[0054] Comparative Example 8 The current collector is prepared using pure fine aluminum particles with a particle size of 5-20 μm. 0.8% magnesium stearate dispersant is added, and the mixture is stirred at high speed. It is then cold-pressed under 12 MPa pressure and held for 8 min. The overall thickness is 90 μm and the overall porosity is 2.8%. The surface is not subjected to sodium-affinity modification treatment.
[0055] Comparative Example 9 The current collector is made by mixing coarse aluminum particles and fine aluminum particles at a mass ratio of 2:1, adding 0.8% magnesium stearate dispersant, mixing at high speed, cold pressing under 8MPa pressure, holding pressure for 8min, with an overall thickness of 90μm and an overall porosity of 11%. The surface is not subjected to sodium affinity modification treatment.
[0056] Comparative Example 10 1. Gradient aluminum substrate preparation: The preparation process is the same as in Example 1, with a surface porosity of 2.0%, an inner layer porosity of 6.5%, a surface layer thickness of 25 μm, an inner layer thickness of 65 μm, an inner layer coarse-to-fine particle mass ratio of 4:1, and 0.8% magnesium stearate as the dispersant. 2. Modification and assembly testing: No in-situ modification steps were performed. The current collector surface was pure aluminum. Battery assembly and performance testing conditions were the same as in Example 1.
[0057] Comparative Example 11 1. Gradient aluminum substrate preparation: The preparation process is the same as in Example 1, except that no dispersant is added. The surface layer thickness is 25 μm, the inner layer thickness is 65 μm, and the mass ratio of coarse to fine particles in the inner layer is 4:1. The surface layer porosity is 3.8%, and the inner layer porosity is 7.9%, indicating uneven pore distribution. 2. In-situ modification and assembly testing: The in-situ modification process is the same as in Example 1, and the battery assembly and performance testing are the same as in Example 1.
[0058] Table 1
[0059] Experimental conclusion: The test results show that Examples 1 to 8, in which key parameters such as particle size distribution, porosity, surface thickness, and inner layer thickness were adjusted respectively, can achieve stable and excellent electrochemical performance. The gradient structure and the in-situ modified layer have obvious synergistic effects, and the overall performance is balanced and reliable.
[0060] Comparative Examples 1 and 2 suffered from significantly reduced battery performance due to the uncontrolled internal pore structure caused by the excessive ratio of coarse to fine aluminum particles in the inner layer, which compromised both buffering effect and structural stability. Comparative Example 3 exhibited high surface porosity, leading to sodium trapping and consequently reduced performance. Comparative Examples 4 and 5 suffered from insufficient compactness or structural redundancy due to surface thickness deviating from the appropriate range. Comparative Examples 6 and 7 suffered from insufficient buffering space or uneven pore distribution due to inner layer thickness outside the reasonable range, resulting in electrochemical performance inferior to the examples. Comparative Example 8, employing a single, uniformly compact structure without gradients, struggled to adapt to changes in sodium deposition volume. Comparative Example 9, with its overall porous structure, experienced increased dead sodium and side reactions, both exhibiting significant performance defects. Comparative Example 10 lacked an in-situ sodium-affinity modified layer, resulting in high interfacial impedance, uneven sodium deposition, and insufficient dendrite suppression, significantly lower performance than the examples. Comparative Example 11, without the addition of a dispersant, suffered from easy agglomeration of aluminum particles, uncontrolled porosity and structural uniformity, failure of the gradient structure, and ultimately, a substantial decline in battery performance.
[0061] In summary, the present invention utilizes a gradient aluminum substrate formed by cold pressing coarse and fine aluminum particle gradation to create a dense surface layer and a porous inner layer. Combined with an in-situ grown, binder-free sodium fluoroaluminate modified layer on the surface, this effectively solves the core problems of existing solid-state sodium-based batteries without a negative electrode, such as poor current collector interface contact, sodium trapping, sodium dendrite growth, high interface impedance, and complex and costly preparation. It balances density and volume buffering capacity while improving the interfacial compatibility between the current collector and the solid electrolyte, significantly enhancing battery cycle stability, critical current density, and high areal capacity adaptability. Furthermore, the preparation process is simple, cost-controllable, and compatible with existing large-scale production lines, resulting in excellent overall battery performance.
[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.
Claims
1. An aluminum-based current collector for solid-state sodium-based batteries without negative electrodes, characterized in that, It includes a gradient aluminum-based substrate and a sodium fluoroaluminate modified layer grown in situ on the surface of the gradient aluminum-based substrate; The gradient aluminum-based substrate has a gradient pore structure with a dense surface layer and a porous inner layer, wherein the surface porosity is ≤3% and the inner layer porosity is 5~8%; The thickness of the gradient aluminum substrate is 70~110μm, the thickness of the sodium fluoroaluminate modified layer is 1~3μm, and the sodium fluoroaluminate modified layer is bonded to the gradient aluminum substrate in situ without adhesive.
2. The aluminum-based current collector for a solid-state sodium-based battery without a negative electrode according to claim 1, characterized in that, The gradient aluminum-based substrate is formed by cold pressing a graded mixture of coarse and fine aluminum particles. The coarse aluminum particles have a particle size of 50~100μm, and the fine aluminum particles have a particle size of 5~20μm; The surface material of the gradient aluminum-based substrate is made of only fine aluminum particles, while the inner material is a mixture of coarse and fine aluminum particles in a mass ratio of 3 to 5:
1.
3. The aluminum-based current collector for a solid-state sodium-based negative electrode-free battery according to claim 1, characterized in that, The surface layer of the gradient aluminum substrate has a thickness of 20-30 μm, and the inner layer has a thickness of 50-80 μm.
4. The aluminum-based current collector for a solid-state sodium-based negative electrode-free battery according to claim 2, characterized in that, Both the surface material and the inner material contain 0.5-1% aluminum powder dispersant by mass; the aluminum powder dispersant is at least one of zinc stearate or magnesium stearate.
5. A method for preparing an aluminum-based current collector for a solid-state sodium-based negative electrode-free battery as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: The layered feeding cold pressing molding process is adopted. The inner layer material is fed into the bottom layer of the mold, and the isolation part is set on the surface of the inner layer material to divide the mold cavity into an inner layer area and a surface area. Surface material is applied to the surface area, followed by cold pressing to obtain an aluminum-based substrate with a gradient pore structure. After removing the separators and shaping, the formed gradient aluminum base is demolded. S2: Immerse the gradient aluminum-based substrate obtained in step S1 into an aqueous solution containing fluoride, so that the aluminum particles on the surface of the substrate undergo an in-situ hydrolysis reaction with the fluoride to generate a sodium fluoroaluminate modified layer; after the reaction is completed, clean and vacuum dry to obtain an aluminum-based current collector for solid-state sodium-based batteries without negative electrodes.
6. The preparation method according to claim 5, characterized in that, The specific process parameters for cold pressing in step S1 are as follows: the cold pressing temperature is controlled at 25~30℃; after feeding, the material is first pre-pressed at a pre-pressure of 5~8MPa for 2~3 minutes, then the pressure is increased to the rated pressure of 12~15MPa and held for 5~10 minutes. After removing the separator, first increase the pressure to the rated pressure of 10~13MPa, hold the pressure for 5~10 minutes, then slowly increase the pressure again to 17~22MPa, hold the pressure for 8~15 minutes to demold; during the holding pressure process, the pressure fluctuation should be controlled within ±0.5MPa.
7. The preparation method according to claim 5, characterized in that, In step S1, after demolding, the surface layer thickness, inner layer thickness, and porosity of the substrate are checked: if the surface layer porosity is >3%, the cold pressing pressure is increased or the holding time is extended before re-cold pressing; if the inner layer porosity is <5%, the cold pressing pressure is reduced or the holding time is shortened before re-cold pressing; if the inner layer porosity is >8%, the mass ratio of coarse and fine aluminum particles in the inner layer material is adjusted before re-cold pressing; until the surface layer thickness is controlled at 20~30μm, the inner layer thickness is controlled at 50~80μm, the surface layer porosity is ≤3%, and the inner layer porosity is 5~8%.
8. The preparation method according to claim 5, characterized in that, In step S2, the concentration of fluoride in the aqueous solution containing fluoride is 0.1~0.3 mol / L, and the fluoride is one or a mixture of two of NH4F and NaF. The gradient aluminum-based substrate is immersed in the aqueous solution containing fluoride and reacted at 30~50℃ for 2~4 h. The vacuum drying conditions are: temperature 80~100℃, vacuum degree 0.08~0.1MPa, and drying time 2~3 h.
9. A solid-state sodium battery without a negative electrode, characterized in that, The aluminum-based current collector for a solid-state sodium-based battery without a negative electrode, as described in any one of claims 1 to 4, is used as the negative electrode current collector.
10. The solid-state sodium-based battery without a negative electrode according to claim 9, characterized in that, The battery also includes an NBH solid electrolyte and a NaCrO2 cathode.