Shape memory alloy-based negative electrode material, preparation method thereof and all-solid-state battery

Abstract

The invention discloses a shape memory alloy-based negative electrode material, a preparation method thereof and an all-solid-state battery. The negative electrode material comprises a three-dimensional porous skeleton, a negative electrode current collector and a material mixing layer, the three-dimensional porous skeleton comprises a matrix made of a shape memory alloy material and amorphous nano silicon particles uniformly dispersed in pores and the surface of the matrix; the mixed material layer comprises a negative electrode active material, a conductive agent, a solid electrolyte, a binder and an additive, and the mixed material layer is coated on one side or two sides of the negative electrode current collector. The all-solid-state battery comprises a consumable, a positive electrode, an electrolyte membrane and a negative electrode material. Through the layered design of the three-dimensional porous framework and the mixing layer, functional separation and synergistic effect are achieved, the framework is mainly responsible for mechanical supporting and stress buffering, and the mixing layer is mainly responsible for electrochemical reaction. The three-dimensional porous skeleton is used as an intermediate functional layer, so that the electrode-electrolyte interface contact state can be effectively improved, and the interface impedance is reduced.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state batteries and anode materials, specifically to anode materials based on shape memory alloys, their preparation methods, and all-solid-state batteries. Background Technology

[0002] During charging and discharging, the insertion and extraction of lithium ions in the negative electrode of an all-solid-state soft-pack battery causes volume expansion and contraction of the negative electrode material. Long-term cycling leads to structural damage, active material pulverization, and repeated rupture of the solid electrolyte interphase (SEI) film, ultimately resulting in battery capacity decay and shortened lifespan. To maintain good solid-solid interface contact, all-solid-state batteries typically require external application of enormous stacking pressure (several to tens of MPa) to ensure energy density and cycle stability, increasing operating costs.

[0003] Different types of anode materials exhibit varying lithium storage mechanisms and significantly different volumes. Traditional carbon-based anode materials show relatively small volumes (approximately 10%). In lithium metal anodes, lithium ions are electroplated (deposited) onto the anode surface during charging, increasing the volume; during discharge, these ions are stripped away, decreasing the volume. The extent of these volumes depends on the amount of deposition, and uneven deposition can lead to dendrites and voids, resulting in a more pronounced volume effect (up to 300% or more). This massive volume change is not merely a change in physical dimensions; it triggers a series of chain reactions, such as material pulverization and structural collapse, leading to permanent capacity decay; an unstable solid electrolyte interface film continuously consumes electrolyte and active lithium, reducing coulombic efficiency and accelerating capacity decay; and structural damage at the electrode level, causing separation of the coating from the current collector (e.g., copper foil), greatly limiting their practical applications.

[0004] Shape memory alloys (SMAs) are special intermetallic compounds capable of recovering their pre-defined shape under specific conditions, exhibiting unique shape memory effects and superelastic properties. They can actively adapt to volume expansion, effectively buffering stress; maintain structural integrity, self-repair electrodes, and re-establish conductive networks and ion channels; and act as an elastic component, continuously applying uniform pressure to stacked electrodes and electrolyte layers, maintaining good contact between interfaces. Therefore, combining shape memory alloys to address volume changes in battery negative electrodes is an important research direction. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a composite solid electrolyte material and its preparation method. This invention proposes a multilayer composite solid electrolyte material, its controllable construction method, and its applications. This material system achieves a technological breakthrough through the construction of a gradient coating structure of a "halide core-functionalized polymer shell." The organic polymer shell acts as a physical barrier, blocking direct contact between the halide core and water and oxygen components in the environment, suppressing hydrolysis side reactions, and ensuring that the conductivity decay rate is less than 5% after 24 hours of exposure in an environment with humidity >30%. Furthermore, the mechanical flexibility and adaptability of the shell enable close conformal contact with the inner electrolyte material, constructing low-impedance ion channels. Meanwhile, this invention further provides a universal preparation strategy for the composite electrolyte. By controlling the composition of the polymer precursor, the solvent polarity gradient, and the thermal kinetic parameters, the chemical composition (such as a single-layer dense sealing layer + an outer ion-conducting layer), thickness (10-200 nm), and functional characteristics (such as self-healing and dendrite suppression) of the shell can be precisely customized. This breaks through the inverted "stability-conductivity" relationship caused by traditional coating technology and provides a material basis for the industrialization of high-safety, high-energy-density solid-state batteries.

[0006] This invention is achieved through the following technical solution:

[0007] Based on a shape memory alloy anode material, the anode material comprises a three-dimensional porous framework, an anode current collector, and a mixing layer. The three-dimensional porous framework includes a matrix composed of shape memory alloy material and amorphous nano-silicon particles uniformly dispersed in the pores and surface of the matrix. The mixing layer contains an anode active material, a conductive agent, a solid electrolyte, a binder, and additives, and is coated on one or both sides of the anode current collector. In the technical solution of this invention, the three-dimensional porous framework, the anode current collector, and the mixing layer constitute a functionally distinct layered composite structure. Through specific spatial arrangement and functional cooperation, the layers jointly solve a series of problems caused by the volume change of the anode in all-solid-state batteries.

[0008] The shape memory alloy material is selected from one or more of titanium-based, copper-based, or iron-based shape memory alloy systems, and the porosity of the three-dimensional porous framework is 20%-60%, with an average pore size of 0.1-5μm.

[0009] The amorphous silicon nanoparticles have a particle size of 5-100 nanometers and are embedded in the pores and surface of the matrix through physical adsorption or chemical bonding.

[0010] The negative electrode active material includes one or more of lithium metal, silicon-based materials, tin-based materials, graphite, or lithium titanate; the conductive agent includes one or more of VGCF or SuperP; the solid electrolyte includes one or more of sulfide electrolyte, halide electrolyte, oxide electrolyte, or polymer electrolyte; and the binder includes one or more of PVDF or PTFE.

[0011] The content of negative electrode active material is 50~90wt%, solid electrolyte is 20~50wt%, conductive agent is 0~4wt%, binder is 0~6wt%, and additive is 0~10wt%, calculated by mass percentage.

[0012] As described above, the shape memory alloy anode material includes the following steps:

[0013] S1. Skeleton prefabrication: Shape memory alloy powder is mixed with a pore-forming agent, and a three-dimensional porous skeleton is prepared by pressing and sintering process. Then, amorphous nano-silicon particles are embedded into the pores and surface of the skeleton by solution impregnation or vapor deposition.

[0014] S2. Mixing and slurry preparation: The negative electrode active material, conductive agent, solid electrolyte, binder and additives are mixed in a solvent to obtain a uniform slurry;

[0015] S3. Composite structure preparation: The three-dimensional porous skeleton is placed on the surface of the negative electrode current collector, and then a mixing layer slurry is coated on the skeleton; or the mixing layer slurry is first coated on the surface of the negative electrode current collector, and then the three-dimensional porous skeleton is pressed onto the surface of the mixing layer.

[0016] S4. Baking: Bake at 60℃-200℃ for 1-24 hours until dry and cured;

[0017] S5. Rolling: Adjust the rolling speed, roll gap width and over-roll pressure to obtain a negative electrode material based on shape memory alloy.

[0018] In step S1, the pressing pressure is 200-500 MPa, the sintering is carried out in an inert atmosphere at a temperature of 600℃-1000℃, and the holding time is 1-5 hours.

[0019] In step S3, the coating is performed using a doctor blade coating or a slot coating method, with a coating thickness of 50-200 μm; in step S5, the roller speed is 0.3-1.5 m / min, the roller gap width is 80-420 μm, and the roller pressure is 0.1-5 MPa.

[0020] An all-solid-state battery includes consumables, a positive electrode, an electrolyte membrane, and a shape memory alloy-based negative electrode material. The method for fabricating the all-solid-state battery includes:

[0021] A1. Transfer the prepared electrolyte membrane to any one or both sides of the negative electrode sheet, and remove the electrolyte membrane current collector.

[0022] A2. Cut the positive electrode sheet and the transferred negative electrode sheet into the design size by die cutting.

[0023] A3. Insulate one or more of the following: positive electrode sheet and negative electrode sheet after transfer.

[0024] A4. Stack the insulating positive and negative electrode sheets together.

[0025] A5. Solder the tabs of the stacked battery cells;

[0026] A6. The battery cells are encapsulated using aluminum-plastic film;

[0027] A7. Densification of the battery cells is carried out in cold or hot isostatic pressing equipment;

[0028] A8. Initialize the densified battery cell with a shape memory metal negative electrode skeleton.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] This invention achieves functional separation and synergy through a layered design of a three-dimensional porous framework and a mixing layer. The framework primarily provides mechanical support and stress buffering, while the mixing layer is mainly responsible for electrochemical reactions. The three-dimensional porous framework, as an intermediate functional layer, effectively improves the electrode-electrolyte interface contact and reduces interfacial impedance. During charging and discharging, the shape memory alloy framework actively adapts to volume changes through phase transition behavior, maintaining the integrity of the electrode structure. Attached Figure Description

[0031] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 This is a schematic diagram of the negative electrode material structure of the present invention;

[0033] Figure 2 This is a schematic diagram of the preparation method of the negative electrode material of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0035] Example 1

[0036] Preparation of shape memory alloy anode materials:

[0037] (1) Weigh 50g of titanium-based shape memory alloy powder (Ti-50.8at%Ni), 20g of ammonium bicarbonate pore-forming agent, and 10g of amorphous nano-silicon powder according to the mass ratio, add them to the ball mill jar, and add 200ml of n-decane dispersant and 500μl of polydimethylsiloxane dispersant at the same time.

[0038] (2) Ball milling for 8 hours, ball milling ball ratio: Φ1mm (30g); Φ3mm (50g); Φ5mm (20g). After ball milling, the slurry is filtered through a 100-mesh sieve.

[0039] (3) Press the filtered slurry into shape at a pressure of 400 MPa for 5 minutes.

[0040] (4) The sintering process is divided into three stages:

[0041] In the first sintering stage, the temperature is increased to 600℃ at a heating rate of 5℃ / min, and sintered for 2 hours to remove the pore-forming agent.

[0042] In the second sintering stage, the temperature was increased from 600℃ to 800℃ at a rate of 3℃ / min, and sintered for 3 hours to complete the initial densification.

[0043] In the third sintering stage, the temperature was increased from 800℃ to 950℃ at a rate of 2℃ / min, and sintered for 4 hours to achieve complete alloying.

[0044] (5) After the heat treatment, the temperature was reduced from 950℃ to room temperature at a cooling rate of 1℃ / min to obtain a three-dimensional porous skeleton material.

[0045] (6) Amorphous nano-silicon particles were deposited on the pore surface of the three-dimensional porous framework by vapor deposition at a temperature of 500℃ for 2 hours.

[0046] (7) Preparation of the mixed layer slurry: Weigh 70wt% silicon-based negative electrode active material, 25wt% sulfide solid electrolyte, 2wt% SuperP conductive agent, and 3wt% PVDF binder by mass percentage, using N-methylpyrrolidone as solvent, and control the solid content at 50%.

[0047] (8) The mixture layer slurry is coated on the surface of the copper foil current collector with a coating thickness of 150 μm, and then the three-dimensional porous skeleton is pressed onto the surface of the mixture layer with a skeleton thickness of 80 μm.

[0048] (9) Bake at 120°C for 12 hours, and then roll at a speed of 1.0 m / min and a pressure of 2 MPa to obtain composite negative electrode material.

[0049] Reference manual attached Figure 1 , Figure 1 This is a schematic diagram of the negative electrode material structure of the present invention. The negative electrode material includes a three-dimensional porous framework, a negative electrode current collector, and a mixing layer. The three-dimensional porous framework consists of a matrix composed of shape memory alloy material and amorphous nano-silicon particles uniformly dispersed in the pores and surface of the matrix.

[0050] Example 2

[0051] Preparation of anode materials in different shape memory alloy systems:

[0052] (1) A copper-based shape memory alloy (Cu-Zn-Al) was used instead of a titanium-based alloy, and other preparation conditions were the same as in Example 1.

[0053] (2) Adjust the sintering process: the maximum sintering temperature is 850℃ and the holding time is 3h.

[0054] (3) SEM observation revealed that the three-dimensional porous framework formed by copper-based shape memory alloy has a more uniform pore size distribution.

[0055] Example 3

[0056] Iron-based shape memory alloy anode materials:

[0057] (1) Use iron-based shape memory alloy (Fe-Mn-Si), adjust the pore-forming agent ratio to 30%, and other conditions are the same as in Example 1.

[0058] (2) The sintering process is adjusted to: maximum temperature 1000℃, holding time 5h.

[0059] Comparative Example 1:

[0060] Similar to Example 1, a negative electrode material without a three-dimensional porous framework is used.

[0061] (1) Prepare a slurry directly according to the mixing layer formula of Example 1 and coat it on the copper foil current collector.

[0062] (2) The baking and rolling processes are the same as in Example 1.

[0063] (3) The obtained negative electrode material does not contain a three-dimensional porous framework structure.

[0064] Comparative Example 2:

[0065] The difference from Example 1 is that a skeleton material without shape memory function is used.

[0066] (1) Use ordinary stainless steel powder instead of shape memory alloy powder.

[0067] (2) Other preparation processes are the same as in Example 1.

[0068] (3) The obtained three-dimensional porous skeleton does not have shape memory effect.

[0069] Structural characterization analysis:

[0070] The morphology of the three-dimensional porous skeleton prepared in Example 1 was observed using a scanning electron microscope (SEM).

[0071] The observation results show that the three-dimensional porous framework exhibits a uniform three-dimensional interconnected pore structure with pore size distribution concentrated in the range of 1-3 μm, and amorphous nano-silicon particles are uniformly distributed on the surface of the framework pores.

[0072] The interfacial impedance of the negative electrode materials prepared in each embodiment and comparative example was tested using the AC impedance method. The results are shown in Table 1.

[0073] Table 1. Interfacial Impedance Test Results for Examples and Comparative Examples

[0074]

[0075] This invention successfully solves the problems of poor interfacial contact and capacity decay caused by negative electrode volume changes in all-solid-state batteries through optimized design of a three-dimensional porous framework, a negative electrode current collector, and a mixing layer. The three-dimensional porous framework, as a functional layer, effectively buffers the stress caused by volume changes and maintains the integrity of the electrode structure through the superelasticity and shape memory effect of shape memory alloys, while simultaneously improving the electrode-electrolyte interface contact. Performance test results of various embodiments fully demonstrate the superiority and practicality of this technical solution.

[0076] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A shape memory alloy anode material, characterized in that, The negative electrode material includes a three-dimensional porous framework, a negative electrode current collector, and a mixing layer; the three-dimensional porous framework includes a matrix composed of shape memory alloy material and amorphous nano-silicon particles uniformly dispersed in the pores and surface of the matrix; the mixing layer contains a negative electrode active material, conductive agent, solid electrolyte, binder, and additives, and the mixing layer is coated on one or both sides of the negative electrode current collector.

2. The shape memory alloy-based anode material according to claim 1, characterized in that, The shape memory alloy material is selected from one or more of titanium-based, copper-based, or iron-based shape memory alloy systems, and the porosity of the three-dimensional porous framework is 20%-60%, with an average pore size of 0.1-5μm.

3. The shape memory alloy-based anode material according to claim 1, characterized in that, The substrate is made of shape memory alloy using powder metallurgy, template method or 3D printing technology to form a three-dimensional interconnected conductive network.

4. The shape memory alloy-based anode material according to claim 1, characterized in that, The amorphous silicon nanoparticles have a particle size of 5-100 nanometers and are embedded in the pores and surface of the matrix through physical adsorption or chemical bonding.

5. The shape memory alloy-based anode material according to claim 1, characterized in that, The negative electrode active material includes one or more of lithium metal, silicon-based materials, tin-based materials, graphite, or lithium titanate; the conductive agent includes one or more of VGCF or SuperP; the solid electrolyte includes one or more of sulfide electrolyte, halide electrolyte, oxide electrolyte, or polymer electrolyte; and the binder includes one or more of PVDF or PTFE.

6. The shape memory alloy-based anode material according to claim 5, characterized in that, The content of negative electrode active material is 50~90 wt.%, solid electrolyte is 20~50 wt.%, conductive agent is 0~4 wt.%, binder is 0~6 wt.%, and additive is 0~10 wt.% by mass percentage.

7. A method for preparing a shape memory alloy anode material as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Skeleton prefabrication: Shape memory alloy powder is mixed with a pore-forming agent, and a three-dimensional porous skeleton is prepared by pressing and sintering process. Then, amorphous nano-silicon particles are embedded into the pores and surface of the skeleton by solution impregnation or vapor deposition. S2. Mixing and slurry preparation: The negative electrode active material, conductive agent, solid electrolyte, binder and additives are mixed in a solvent to obtain a uniform slurry; S3. Composite structure preparation: The three-dimensional porous skeleton is placed on the surface of the negative electrode current collector, and then a mixing layer slurry is coated on the skeleton; or the mixing layer slurry is first coated on the surface of the negative electrode current collector, and then the three-dimensional porous skeleton is pressed onto the surface of the mixing layer. S4. Baking: Bake at 60℃-200℃ for 1-24 hours until dry and cured; S5. Rolling: Adjust the rolling speed, roll gap width and over-roll pressure to obtain a negative electrode material based on shape memory alloy.

8. The method for preparing shape memory alloy anode material according to claim 7, characterized in that, In step S1, the pressing pressure is 200-500 MPa, the sintering is carried out in an inert atmosphere at a temperature of 600℃-1000℃, and the holding time is 1-5 hours.

9. The method for preparing shape memory alloy anode material according to claim 7, characterized in that, In step S3, the coating is performed using a doctor blade coating or a slot coating method, with a coating thickness of 50-200 μm; in step S5, the roller speed is 0.3-1.5 m / min, the roller gap width is 80-420 μm, and the roller pressure is 0.1-5 MPa.

10. An all-solid-state battery, characterized in that, The method for preparing the all-solid-state battery, including the shape memory alloy anode material as described in any one of claims 1-6, comprises: A1. Transfer the prepared electrolyte membrane to any one or both sides of the negative electrode sheet, and remove the electrolyte membrane current collector. A2. Cut the positive electrode sheet and the transferred negative electrode sheet into the design size by die cutting. A3. Insulate one or more of the following: positive electrode sheet and negative electrode sheet after transfer. A4. Stack the insulating positive and negative electrode sheets together. A5. Solder the tabs of the stacked battery cells; A6. The battery cells are encapsulated using aluminum-plastic film; A7. Densification of the battery cells is carried out in cold or hot isostatic pressing equipment; A8. Initialize the densified battery cell with a shape memory metal negative electrode skeleton.

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