Negative electrode substrate of sodium metal battery as well as preparation method and application of negative electrode substrate

Abstract

The invention provides a sodium metal battery negative electrode substrate and a preparation method and application thereof. The preparation method comprises the following steps: providing mixed slurry, wherein the mixed slurry comprises a phosphorus-containing polymer precursor, a cross-linking agent, a conductive filler and a photoinitiator; the phosphorus-containing polymer precursor contains a nucleophilic functional group; and coating a negative electrode current collector with the mixed slurry, and then sequentially carrying out photopolymerization curing and thermocuring to form a polymer coating, so as to obtain the sodium metal battery negative electrode substrate. According to the invention, a polymer coating with a hard shell-soft core gradient structure is constructed on a current collector through a phosphorus-containing polymer precursor and a light-heat dual-curing process, and a nucleophilic functional group induces uniform nucleation of sodium through a strong coordination effect so as to inhibit dendritic crystals; a phosphorus group can effectively quench free radicals, so that the flame retardance and the interface stability are improved; the surface layer of the gradient structure is compact to inhibit dendritic crystal puncture, the bottom layer is porous to buffer volume change, and uniform deposition, interface stability and volume buffering are synchronously achieved.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a sodium metal battery anode substrate, its preparation method, and its application. Background Technology

[0002] Sodium metal batteries, as a promising next-generation high-energy-density energy storage system, have attracted much attention due to the abundant reserves of sodium, low raw material costs, and the theoretical specific capacity of sodium metal anodes reaching 1166 mAh / g. In particular, electroplated sodium metal anode batteries, by completely removing the sodium metal from the initial anode side, further improve the overall energy density of the battery, reduce processing difficulty and cost, and demonstrate great application potential. However, problems such as sodium dendrite growth, interfacial side reactions, and volume expansion severely limit their practical application. Electroplated anode battery structures can further improve energy density, but they place higher demands on the interfacial control capabilities of the anode.

[0003] To address these challenges, existing technologies often employ polymers to construct the negative electrode substrate to regulate metal deposition behavior. However, current polymer coatings used in sodium metal batteries still suffer from several inherent defects. For example, their inherent flammability significantly increases the safety risk of battery thermal runaway; the inhomogeneity of the polymer structure leads to uneven sodium metal deposition, easily inducing dendrite growth and local current density imbalance; furthermore, insufficient interfacial stability between the coating and the electrode makes them prone to chemical side reactions or contact failures during long-term battery cycling, limiting the battery's cycle life and overall reliability. These limitations collectively make it difficult for existing polymer coatings to meet the comprehensive requirements of high efficiency, safety, and long-cycle operation for electroplated sodium metal negative electrodes.

[0004] Therefore, how to develop a negative electrode substrate that can simultaneously achieve uniform sodium deposition, volume buffering, and interface stability is a technical challenge that urgently needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a sodium metal battery anode substrate, its preparation method, and its applications. This invention introduces a phosphorus-containing polymer precursor and combines it with a photo-thermal dual-curing process, thereby successfully constructing a polymer coating with a gradient structure of "dense surface layer - porous bottom layer" on the current collector, achieving multiple benefits: Firstly, the nucleophilic functional groups in the phosphorus-containing polymer precursor bind to sodium ions through strong coordination, effectively reducing the nucleation barrier for sodium metal deposition, inducing the formation of uniform and dense sodium nuclei, thereby inhibiting dendrite growth, improving deposition morphology, and enhancing interface stability. Secondly, its phosphorus-oxygen double bond flame-retardant groups can efficiently quench highly reactive free radicals in the electrolyte, blocking chain reactions and enhancing flame retardant performance. Simultaneously, it can stabilize the electrode / electrolyte interface, reduce side reactions, inhibit electrolyte decomposition and dendrite formation, further improving the safety and cycle life of the sodium metal battery. Furthermore, the gradient structure formed through photo-thermal curing synergistic regulation utilizes the oxygen inhibition effect to retain reactive double bonds on the material surface. Simultaneously, thermal gradient regulation induces preferential secondary cross-linking reactions on the surface and delayed foaming in the underlying layer, achieving the fabrication of a negative electrode substrate with a "hard shell-soft core" gradient structure. This gradient structure combines high surface modulus to suppress dendrite penetration with underlying flexibility to buffer volume changes during sodium deposition / exfoliation, thereby simultaneously improving the device's mechanical adaptability and electrochemical performance. In summary, this fabrication process provides a negative electrode substrate for high-performance sodium metal batteries that combines uniform sodium deposition, volume buffering, and interface stability.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a sodium metal battery anode substrate, the method comprising the following steps:

[0008] A mixed slurry is provided, the mixed slurry comprising a phosphorus-containing polymer precursor, a crosslinking agent, a conductive filler, and a photoinitiator; the phosphorus-containing polymer precursor contains nucleophilic functional groups.

[0009] The mixed slurry is coated onto the negative electrode current collector, and then photopolymerization and thermal curing are performed sequentially to form a polymer coating, thereby obtaining the sodium metal battery negative electrode substrate.

[0010] It should be noted that phosphorus-containing polymers have excellent flame retardant properties and metal coordination ability, but their application in batteries is mostly concentrated in electrolyte additives or positive electrode coatings, while their integrated structural and functional design as a negative electrode substrate has not been reported.

[0011] This invention introduces a phosphorus-containing polymer precursor and combines it with a photo-thermal dual-curing process to successfully construct a polymer coating with a gradient structure of "dense surface layer - porous bottom layer" on the current collector, achieving multiple effects: On the one hand, the nucleophilic functional groups in the phosphorus-containing polymer precursor bind to sodium ions through strong coordination, effectively reducing the nucleation barrier of sodium metal deposition, inducing the formation of uniform and dense sodium nuclei, thereby inhibiting dendrite growth, improving deposition morphology, and enhancing interface stability; on the other hand, its phosphorus-oxygen double bond flame-retardant groups can efficiently quench highly active free radicals in the electrolyte, block chain reactions, enhance flame retardant performance, and at the same time stabilize the electrode / electrolyte interface, reduce side reactions, inhibit electrolyte decomposition and dendrite formation, further improving the safety and cycle life of sodium metal batteries. Furthermore, the gradient structure formed through photo-thermal curing synergistic regulation utilizes the oxygen inhibition effect to retain reactive double bonds on the material surface. Simultaneously, thermal gradient regulation induces preferential secondary cross-linking reactions on the surface and delayed foaming in the underlying layer, achieving the fabrication of a negative electrode substrate with a "hard shell-soft core" gradient structure. This gradient structure combines high surface modulus to suppress dendrite penetration with underlying flexibility to buffer volume changes during sodium deposition / exfoliation, thereby simultaneously improving the device's mechanical adaptability and electrochemical performance. In summary, this fabrication process provides a negative electrode substrate for high-performance sodium metal batteries that combines uniform sodium deposition, volume buffering, and interface stability.

[0012] Preferably, the negative electrode current collector comprises a metal foil. For example, it may be aluminum foil, etc.

[0013] Preferably, the molecular formula of the phosphorus-containing polymer precursor is: CH2=CR1-COO-(CH2)nP=(X)R2R3, where R1 is selected as a hydrogen atom or a methyl group, n is in the range of 1-4, for example, it can be 1, 2, 3 or 4, X is an oxygen atom or a sulfur atom, and R2 and R3 are each independently selected from any one of alkyl, aryl or polyether chains.

[0014] Preferably, the phosphorus-containing polymer precursor includes any one or a combination of at least two of the following: dimethyl methacryloyloxyethylphosphonate, 2-acrylamidoethylphosphonic acid, methyl 2-(diethylthiophosphoryl)acrylate, propyl 3-(diphenylthiophosphoryl)methacrylate, or butyl 4-(methylphenylphosphoryl)acrylate.

[0015] Preferably, the method for preparing the mixed slurry includes:

[0016] Under an inert atmosphere, the phosphorus-containing polymer precursor and crosslinking agent are mixed and dissolved in a solvent, and then conductive filler and photoinitiator are added and stirred to obtain a mixed slurry.

[0017] For example, the gas in the inert atmosphere can be, for example, nitrogen or argon.

[0018] Preferably, based on the total mass of the phosphorus-containing polymer precursor and the crosslinking agent, the mass percentage of the phosphorus-containing polymer precursor is 20-50 wt%, for example, it can be 20 wt%, 30 wt%, 40 wt%, or 50 wt%.

[0019] In this invention, a suitable mass ratio is key to balancing flame retardancy and polymerization efficiency. If the mass ratio of the phosphorus-containing polymer precursor is too small, the subsequently formed polymer will fail to achieve a flame-retardant effect; if the mass ratio of the phosphorus-containing polymer precursor is too large, too many free radicals will be reacted, greatly slowing down the subsequent polymerization and curing process.

[0020] Preferably, the mass ratio of the phosphorus-containing polymer precursor to the crosslinking agent is (1-4):(4-7), wherein the phosphorus-containing polymer precursor is selected from the range of "1-4", for example, it can be 1, 2, 3 or 4, etc., and the crosslinking agent is selected from the range of "4-7", for example, it can be 4, 5, 6 or 7, etc.

[0021] Preferably, the total mass of the phosphorus-containing polymer precursor and the crosslinking agent accounts for 40-80 wt% of the mass of the mixed slurry, for example, it can be 40 wt%, 50 wt%, 60 wt%, 70 wt% or 80 wt%, etc., preferably 40-60 wt%.

[0022] In this invention, if the total mass ratio of the phosphorus-containing polymer precursor and the crosslinking agent is too small, the viscosity of the polymer coating will be too low, and it will be unable to adhere stably to the surface of the current collector; if the total mass ratio of the phosphorus-containing polymer precursor and the crosslinking agent is too large, the viscosity of the polymer coating will be too high, and it will be difficult to achieve a uniform coating effect.

[0023] Preferably, the crosslinking agent comprises any one or a combination of at least two of the following: trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethylene glycol diacrylate, trimethylolpropane triallyl ether, pentaerythritol triallyl ether, or pentaerythritol tetraallyl ether.

[0024] Preferably, based on the mass of the polymer in the polymer coating, the mass percentage of the conductive filler is 10-30 wt%, for example, it can be 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0025] In this invention, a suitable conductive filler is key to achieving a balance between high conductivity and structural integrity. If the mass proportion of the conductive filler is too large, it will lead to the destruction of the porous structure in the subsequently formed polymer; if the mass proportion of the conductive filler is too small, it will lead to insufficient conductivity of the negative electrode substrate and excessive battery polarization.

[0026] Preferably, the conductive filler comprises any one or a combination of at least two of graphene oxide, carbon nanotubes, Ketjen black, or acetylene black.

[0027] Preferably, the photoinitiator has a mass percentage of 0.5-6 wt%, based on the polymer mass in the polymer coating, for example, it can be 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or 6 wt%.

[0028] Preferably, the temperature for heat curing is 80-120℃, such as 80℃, 90℃, 100℃, 110℃ or 120℃, and the time is 0.5-2h, such as 0.5h, 1h, 1.5h or 2h.

[0029] In this invention, a suitable thermosetting temperature is crucial for achieving full cross-linking of the polymer and stable molding of the gradient structure. If the thermosetting temperature is too low, the polymer cannot be fully polymerized; if the thermosetting temperature is too high, the surface curing is too fast, the polymer gelation is uneven, and energy consumption is high.

[0030] Preferably, the polymer coating has a gradient structure, which consists of a porous underlayer and a dense surface layer.

[0031] The polymer coating designed in this invention has a gradient structure of "dense surface layer - porous bottom layer". It utilizes the oxygen inhibition effect to retain reactive double bonds on the surface of the material. At the same time, it induces secondary cross-linking reaction preferentially on the surface layer and delayed foaming in the bottom layer through thermal gradient regulation, realizing the preparation of a negative electrode substrate with a "hard shell - soft core" gradient structure. This gradient structure has both high modulus of the surface layer to suppress dendrite penetration and flexibility of the bottom layer to buffer the volume change during sodium deposition / stripping, thereby simultaneously improving the mechanical adaptability and electrochemical performance of the device.

[0032] Preferably, the thickness of the polymer coating is 50-100 μm, for example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0033] Preferably, the preparation method includes the following steps:

[0034] (1) Preparation of mixed slurry, the specific steps include:

[0035] Under an inert atmosphere, the phosphorus-containing polymer precursor and crosslinking agent are mixed and dissolved in a solvent, and then conductive filler and photoinitiator are added and stirred to obtain a mixed slurry.

[0036] The mass ratio of the phosphorus-containing polymer precursor to the crosslinking agent is (1-4):(4-7); the total mass of the phosphorus-containing polymer precursor and the crosslinking agent accounts for 40-80 wt% of the total mass of the mixed slurry; the phosphorus-containing polymer precursor includes any one or a combination of at least two of the following: dimethyl methacryloyloxyethylphosphonate, 2-acrylamidoethylphosphonic acid, methyl 2-(diethylthiophosphoryl)acrylate, propyl methacrylate-3-(diphenylthiophosphoryl)methacrylate, or butyl 4-(methylphenylphosphoryl)acrylate; the solvent is any one or a combination of at least two of the following: water, acetone, n-hexane, dimethyl sulfoxide, N,N-dimethylformamide, isopropanol, tetrahydrofuran, or dichloromethane; the photoinitiator includes any one or a combination of at least two of the following: 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, diphenyliodohexafluorophosphate, or α-hydroxyisobutyroxene.

[0037] (2) The mixed slurry is coated on the surface of the negative electrode current collector, and then subjected to light intensity of 2-10 mW / cm. 2 (For example, it could be 2mW / cm) 2 4mW / cm 2 6mW / cm 2 8mW / cm 2 or 10mW / cm 2 The sodium metal battery anode substrate is obtained by photopolymerization curing under ultraviolet light irradiation for 10-20 minutes (e.g., 10 minutes, 15 minutes, or 20 minutes), followed by thermal curing at 80-120°C for 0.5-2 hours to form a polymer coating with a thickness of 50-100 μm.

[0038] In a second aspect, the present invention provides a sodium metal battery anode substrate, which is prepared by the preparation method described in the first aspect.

[0039] Thirdly, the present invention provides a sodium metal battery, the sodium metal battery comprising the sodium metal battery negative electrode substrate as described in the second aspect.

[0040] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) This invention introduces a phosphorus-containing polymer precursor and combines it with a photo-thermal dual curing process, thereby successfully constructing a polymer coating with a "dense surface layer - porous bottom layer" gradient structure on the current collector, achieving multiple effects: On the one hand, the nucleophilic functional groups in the phosphorus-containing polymer precursor bind to sodium ions through strong coordination, effectively reducing the nucleation barrier of sodium metal deposition, inducing the formation of uniform and dense sodium nuclei, thereby inhibiting dendrite growth, improving deposition morphology, and enhancing interface stability; on the other hand, its phosphorus-oxygen double bond flame-retardant groups can efficiently quench highly active free radicals in the electrolyte, block chain reactions, enhance flame retardant performance, and at the same time stabilize the electrode / electrolyte interface, reduce side reactions, inhibit electrolyte decomposition and dendrite formation, further improving the safety and cycle life of sodium metal batteries. Furthermore, the gradient structure formed by photo-thermal curing synergistic regulation utilizes the oxygen inhibition effect to retain reactive double bonds on the material surface. Simultaneously, thermal gradient regulation induces preferential secondary cross-linking reactions on the surface and delayed foaming in the bottom layer, thus realizing the preparation of a negative electrode substrate with a "hard shell-soft core" gradient structure. This gradient structure combines the high modulus of the surface layer to suppress dendrite penetration with the flexibility of the bottom layer to buffer volume changes during sodium deposition / exfoliation, thereby simultaneously improving the mechanical adaptability and electrochemical performance of the device.

[0043] (2) The preparation process provided by the present invention provides a negative electrode substrate with uniform sodium deposition, volume buffer and interface stability for the preparation of sodium metal batteries, and finally realizes the high efficiency, safety and long cycle operation of sodium metal batteries. Detailed Implementation

[0044] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing a sodium metal battery negative electrode substrate, the method comprising the following steps:

[0047] (1) Preparation of mixed slurry, the specific steps include:

[0048] Under a nitrogen atmosphere, 1g of dimethyl methacryloyloxyethylphosphonate and 4g of trimethylolpropane triacrylate were mixed and dissolved in 7.5g of N,N-dimethylformamide. Then, 100mg / g of Kejen black (each gram of slurry system (before the addition of Kejen black) contains 100mg of Kejen black) and 5mg / g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide were added and stirred to obtain a mixed slurry.

[0049] Specifically, based on the total mass of the mixture of dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate, the mass percentage of dimethyl methacryloyloxyethylphosphonate is 20 wt%; the mass ratio of dimethyl methacryloyloxyethylphosphonate to trimethylolpropane triacrylate is 1:4; the total mass of dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate accounts for 40% of the total mass of the mixed slurry; based on the polymer mass in the polymer coating, the mass percentage of Ketjen Black is 10 wt%; and based on the polymer mass in the polymer coating, the mass percentage of 2,4,6-trimethylbenzoyl diphenylphosphine oxide is 0.5 wt%.

[0050] (2) The mixed slurry is coated on the surface of aluminum foil, and then subjected to light intensity of 2mW / cm. 2 The substrate is photopolymerized and cured by irradiation with ultraviolet light for 20 minutes, and then thermally cured at 80°C for 2 hours to form a polymer coating with a thickness of 50 μm, thus obtaining the sodium metal battery anode substrate; wherein, the polymer coating has a gradient structure, which consists of a porous bottom layer and a dense surface layer.

[0051] Example 2

[0052] This embodiment provides a method for preparing a sodium metal battery negative electrode substrate, the method comprising the following steps:

[0053] (1) Preparation of mixed slurry, the specific steps include:

[0054] Under a nitrogen atmosphere, 2g of dimethyl methacryloyloxyethylphosphonate and 2g of trimethylolpropane triacrylate were mixed and dissolved in 2.6g of N,N-dimethylformamide. Then, 300mg / g of graphene oxide (each mL of slurry system (before the addition of graphene oxide) contains 300mg of graphene oxide) and 60mg / g of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide were added and stirred to obtain a mixed slurry.

[0055] Specifically, based on the total mass of the mixture of dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate, the mass percentage of dimethyl methacryloyloxyethylphosphonate is 50 wt%; the mass ratio of dimethyl methacryloyloxyethylphosphonate to trimethylolpropane triacrylate is 1:1; the total mass of dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate accounts for 60% of the total mass of the mixed slurry; based on the polymer mass in the polymer coating, the mass percentage of graphene oxide is 30 wt%; and based on the polymer mass in the polymer coating, the mass percentage of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 6 wt%.

[0056] (2) The mixed slurry is coated on the surface of aluminum foil, and then subjected to light intensity of 10mW / cm. 2 The substrate is photopolymerized and cured by irradiation with ultraviolet light for 10 minutes, and then thermally cured at 120°C for 0.5 hours to form a polymer coating with a thickness of 100 μm, thus obtaining the sodium metal battery anode substrate; wherein, the polymer coating has a gradient structure, which consists of a porous bottom layer and a dense surface layer.

[0057] Example 3

[0058] This embodiment provides a method for preparing a sodium metal battery negative electrode substrate, the method comprising the following steps:

[0059] (1) Preparation of mixed slurry, the specific steps include:

[0060] Under a nitrogen atmosphere, 2g of 3-(diphenylthiophosphoryl) methacrylate and 3g of trimethylolpropane triacrylate were mixed and dissolved in 5g of tetrahydrofuran. Then, 200mg / g of Kejen black (each mL of slurry system (before the addition of Kejen black) contains 200mg of Kejen black) and 15mg / g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide were added and stirred to obtain a mixed slurry.

[0061] Specifically, based on the total mass of the mixture of 3-(diphenylthiophosphoryl) propyl methacrylate and trimethylolpropane triacrylate, the mass percentage of 3-(diphenylthiophosphoryl) propyl methacrylate is 40 wt%; the mass ratio of 3-(diphenylthiophosphoryl) propyl methacrylate to trimethylolpropane triacrylate is 4:6; the total mass of 3-(diphenylthiophosphoryl) propyl methacrylate and trimethylolpropane triacrylate accounts for 50% of the total mass of the mixed slurry; based on the polymer mass in the polymer coating, the mass percentage of Ketjen Black is 20 wt%; and based on the polymer mass in the polymer coating, the mass percentage of 2,4,6-trimethylbenzoyl diphenylphosphine oxide is 1.5 wt%.

[0062] (2) The mixed slurry is coated on the surface of aluminum foil, and then subjected to light intensity of 10mW / cm. 2 The substrate is photopolymerized and cured by irradiation with ultraviolet light for 15 minutes, and then thermally cured at 100°C for 1.5 hours to form a polymer coating with a thickness of 75 μm, thus obtaining the sodium metal battery anode substrate; wherein, the polymer coating has a gradient structure, which consists of a porous bottom layer and a dense surface layer.

[0063] Example 4

[0064] This embodiment provides a method for preparing a sodium metal battery negative electrode substrate, the method comprising the following steps:

[0065] (1) Preparation of mixed slurry, the specific steps include:

[0066] Under a nitrogen atmosphere, 1.5 g of dimethyl methacryloyloxyethylphosphonate and 4 g of pentaerythritol triallyl ether were mixed and dissolved in 4 g of dichloromethane. Then, 150 mg / mL of carbon nanotubes (each mL of slurry system (before the addition of carbon nanotubes) contains 150 mg of carbon nanotubes) and 25 mg / g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide were added and stirred to obtain a mixed slurry.

[0067] Specifically, based on the total mass of the mixture of dimethyl methacryloyloxyethylphosphonate and pentaerythritol triallyl ether, the mass percentage of dimethyl methacryloyloxyethylphosphonate is 27 wt%; the mass ratio of dimethyl methacryloyloxyethylphosphonate to pentaerythritol triallyl ether is 1.5:4; the total mass of dimethyl methacryloyloxyethylphosphonate and pentaerythritol triallyl ether accounts for 58% of the total mass of the mixed slurry; based on the polymer mass in the polymer coating, the mass percentage of carbon nanotubes is 15 wt%; and based on the polymer mass in the polymer coating, the mass percentage of 2,4,6-trimethylbenzoyl diphenylphosphine oxide is 2.5 wt%.

[0068] (2) The mixed slurry is coated on the surface of aluminum foil, and then subjected to light intensity of 8mW / cm. 2 The substrate is photopolymerized and cured by irradiation with ultraviolet light for 15 minutes, and then thermally cured at 90°C for 1 hour to form a polymer coating with a thickness of 80 μm, thus obtaining the sodium metal battery anode substrate; wherein, the polymer coating has a gradient structure, which consists of a porous bottom layer and a dense surface layer.

[0069] Example 5

[0070] This embodiment provides a method for preparing a sodium metal battery negative electrode substrate, the method comprising the following steps:

[0071] (1) Preparation of mixed slurry, the specific steps include:

[0072] Under a nitrogen atmosphere, 1 g of 4-(methylphenylphospho)butyl acrylate and 4 g of ethylene glycol diacrylate were mixed and dissolved in 7.5 g of isopropanol. Then, 120 mg / g of Kejen black (containing 350 mg of Kejen black per mL of slurry system (before the addition of Kejen black) and 20 mg / g of 2,4,6-trimethylbenzoyl diphenylphosphine oxide were added and stirred to obtain a mixed slurry.

[0073] Specifically, based on the total mass of the mixture of 4-(methylphenylphospho)butyl acrylate and ethylene glycol diacrylate, the mass percentage of 4-(methylphenylphospho)butyl acrylate is 20 wt%; the mass ratio of 4-(methylphenylphospho)butyl acrylate to ethylene glycol diacrylate is 1:4; the total mass of 4-(methylphenylphospho)butyl acrylate and ethylene glycol diacrylate accounts for 40% of the total mass of the mixed slurry; based on the polymer mass in the polymer coating, the mass percentage of Ketjen Black is 12 wt%; and based on the polymer mass in the polymer coating, the mass percentage of 2,4,6-trimethylbenzoyl diphenylphosphine oxide is 2 wt%.

[0074] (2) The mixed slurry is coated on the surface of aluminum foil, and then subjected to light intensity of 5mW / cm. 2 The substrate is photopolymerized and cured by irradiation with ultraviolet light for 20 minutes, and then thermally cured at 95°C for 1 hour to form a polymer coating with a thickness of 50 μm, thus obtaining the sodium metal battery anode substrate; wherein, the polymer coating has a gradient structure, which consists of a porous bottom layer and a dense surface layer.

[0075] Example 6

[0076] This embodiment provides a method for preparing a sodium metal battery negative electrode substrate, the method comprising the following steps:

[0077] (1) Preparation of mixed slurry, the specific steps include:

[0078] Under a nitrogen atmosphere, 2g of 3-(diphenylthiophosphoryl) methacrylate and 4g of pentaerythritol triallyl ether were mixed and dissolved in 7g of acetone. Then, 250mg / g of Ketjen black (containing 250mg of Ketjen black per mL of slurry system (before the addition of Ketjen black)) and 20mg / g of graphene oxide were added, followed by 20mg / g of α-hydroxyisobutyroxene and stirred to obtain a mixed slurry.

[0079] Based on the total mass of the mixture of 3-(diphenylthiophosphoryl) propyl methacrylate and pentaerythritol trially ether, the mass percentage of 3-(diphenylthiophosphoryl) propyl methacrylate is 33 wt%; the mass ratio of 3-(diphenylthiophosphoryl) propyl methacrylate to pentaerythritol trially ether is 2:4; the total mass of 3-(diphenylthiophosphoryl) propyl methacrylate and pentaerythritol trially ether accounts for 54% of the total mass of the mixed slurry; based on the polymer mass in the polymer coating, the total mass percentage of Ketjen Black and graphene oxide is 27 wt%; based on the polymer mass in the polymer coating, the mass percentage of α-hydroxyisobutyrylbenzene is 2 wt%.

[0080] (2) The mixed slurry is coated on the surface of aluminum foil, and then subjected to light intensity of 5mW / cm. 2 The substrate is photopolymerized and cured by irradiation with ultraviolet light for 15 minutes, and then thermally cured at 110°C for 1.5 hours to form a polymer coating with a thickness of 75 μm, thus obtaining the sodium metal battery anode substrate; wherein, the polymer coating has a gradient structure, which consists of a porous bottom layer and a dense surface layer.

[0081] Example 7

[0082] The difference between this embodiment and Embodiment 1 is that, based on the total mass of the mixture of dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate, the mass percentage of dimethyl methacryloyloxyethylphosphonate is 15 wt%.

[0083] The remaining preparation methods and parameters are consistent with those in Example 1.

[0084] Example 8

[0085] The difference between this embodiment and Embodiment 1 is that, based on the total mass of the mixture of dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate, the mass percentage of dimethyl methacryloyloxyethylphosphonate is 55 wt%.

[0086] The remaining preparation methods and parameters are consistent with those in Example 1.

[0087] Example 9

[0088] The difference between this embodiment and Embodiment 1 is that the total mass of the dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate accounts for 35% of the total mass of the mixed slurry.

[0089] The remaining preparation methods and parameters are consistent with those in Example 1.

[0090] Example 10

[0091] The difference between this embodiment and Embodiment 1 is that the total mass of the dimethyl methacryloyloxyethylphosphonate and trimethylolpropane triacrylate accounts for 85% of the total mass of the mixed slurry.

[0092] The remaining preparation methods and parameters are consistent with those in Example 1.

[0093] Example 11

[0094] The difference between this embodiment and Embodiment 1 is that, based on the mass of the polymer in the polymer coating, the mass percentage of the graphene oxide is 5 wt%.

[0095] The remaining preparation methods and parameters are consistent with those in Example 1.

[0096] Example 12

[0097] The difference between this embodiment and Embodiment 1 is that, based on the mass of the polymer in the polymer coating, the mass percentage of graphene oxide is 35 wt%.

[0098] The remaining preparation methods and parameters are consistent with those in Example 1.

[0099] Example 13

[0100] The difference between this embodiment and Embodiment 1 is that the thermosetting temperature is 70°C.

[0101] The remaining preparation methods and parameters are consistent with those in Example 1.

[0102] Example 14

[0103] The difference between this embodiment and Embodiment 1 is that the thermosetting temperature is 130°C.

[0104] The remaining preparation methods and parameters are consistent with those in Example 1.

[0105] Comparative Example 1

[0106] This comparative example provides a method for preparing a sodium metal battery anode substrate, the method comprising the following steps:

[0107] (1) Under a nitrogen atmosphere, 2g of butyl acrylate and 2g of triethylene glycol dimethacrylate were mixed, and then 20μL / mL of azobisisobutyronitrile was added to obtain a mixed slurry.

[0108] (2) The mixed slurry is coated on the surface of aluminum foil and then heat-cured at 80°C for 2 hours to form a polymer coating, thereby obtaining a sodium metal battery negative electrode substrate.

[0109] Comparative Example 2

[0110] The difference between this comparative example and Example 1 is that the dimethyl methacryloyloxyethylphosphonate is replaced with an equal mass of butyl acrylate.

[0111] The remaining preparation methods and parameters are consistent with those in Example 1.

[0112] Comparative Example 3

[0113] The difference between this comparative example and Example 1 is that the mixed slurry does not contain Ketjen Black.

[0114] The remaining preparation methods and parameters are consistent with those in Example 1.

[0115] Comparative Example 4

[0116] The difference between this comparative example and Example 1 is that the thermosetting process is not performed.

[0117] The remaining preparation methods and parameters are consistent with those in Example 1.

[0118] Comparative Example 5

[0119] The difference between this comparative example and Example 1 is that the photopolymerization curing is not performed.

[0120] The remaining preparation methods and parameters are consistent with those in Example 1.

[0121] Performance testing

[0122] I. Combustion experiments were conducted on the sodium metal battery negative electrode substrates provided in the above embodiments and comparative examples. The specific steps included:

[0123] The negative electrode substrate of the sodium metal battery was ignited by a jet flame, and the time it took for the combustion to extinguish was recorded.

[0124] II. Using the sodium metal battery negative electrode substrate provided in the above embodiments and comparative examples as the negative electrode, sodium metal as the positive electrode, and a 1 mol / L NaPF6 solution (the solvent is diethylene glycol dimethyl ether, abbreviated as G2) as the electrolyte, a sodium metal battery is assembled.

[0125] The sodium metal battery was subjected to a constant current sodium metal deposition cycle test to obtain the number of cycles and the average coulombic efficiency. The specific test conditions were as follows: 1 mAh of sodium metal was deposited at a current density of 1 mA / cm², and the charging cutoff voltage was 1 V. The charging capacity and discharging capacity of each cycle were recorded. The coulombic efficiency was calculated by the ratio of the discharging capacity to the charging capacity of each cycle, and the average coulombic efficiency was the arithmetic mean of all coulombic efficiencies within the number of cycles.

[0126] The test results are shown in Table 1.

[0127] Table 1

[0128]

[0129] analyze:

[0130] As shown in Table 1, this invention introduces a phosphorus-containing polymer precursor and combines it with a photo-thermal dual-curing process, thereby successfully constructing a polymer coating with a "dense surface layer - porous bottom layer" gradient structure on the current collector, achieving multiple effects: On the one hand, the nucleophilic functional groups in the phosphorus-containing polymer precursor bind to sodium ions through strong coordination, effectively reducing the nucleation barrier of sodium metal deposition, inducing the formation of uniform and dense sodium nuclei, thereby inhibiting dendrite growth, improving deposition morphology, and enhancing interface stability; on the other hand, its phosphorus-oxygen double bond flame-retardant groups can efficiently quench highly active free radicals in the electrolyte, block chain reactions, enhance flame retardant performance, and at the same time stabilize the electrode / electrolyte interface, reduce side reactions, inhibit electrolyte decomposition and dendrite formation, further improving the safety and cycle life of sodium metal batteries. Furthermore, the gradient structure formed through photo-thermal curing synergistic regulation utilizes the oxygen inhibition effect to retain reactive double bonds on the material surface. Simultaneously, thermal gradient regulation induces preferential secondary cross-linking reactions on the surface and delayed foaming in the underlying layer, achieving the fabrication of a negative electrode substrate with a "hard shell-soft core" gradient structure. This gradient structure combines high surface modulus to suppress dendrite penetration with underlying flexibility to buffer volume changes during sodium deposition / exfoliation, thereby simultaneously improving the device's mechanical adaptability and electrochemical performance. The fabrication process provided by this invention offers a negative electrode substrate for sodium metal batteries that combines uniform sodium deposition, volume buffering, and interface stability, ultimately achieving high efficiency, safety, and long-cycle operation of sodium metal batteries.

[0131] As can be seen from the comparison between Example 1 and Examples 7-8, if the mass proportion of dimethyl methacryloyloxyethylphosphonate (i.e., phosphorus-containing polymer precursor) is too small, the polymer formed subsequently will not achieve the flame retardant effect and will not be conducive to the sodium metal deposition effect in the battery; if the mass proportion of dimethyl methacryloyloxyethylphosphonate (i.e., phosphorus-containing polymer precursor) is too large, too many free radicals will be reacted, which will greatly slow down the subsequent polymerization and curing process and will not be conducive to the formation of a uniform polymer coating.

[0132] A comparison of Examples 1 and 9-10 shows that if the total mass of dimethyl methacryloyloxyethyl phosphonate and trimethylolpropane triacrylate (i.e., the total mass of the phosphorus-containing polymer precursor and crosslinking agent) is too small to account for the total mass of the mixed slurry, the viscosity of the polymer coating will be too low, making it unable to adhere stably to the surface of the current collector and thus preventing the formation of an applicable substrate. Conversely, if the total mass of dimethyl methacryloyloxyethyl phosphonate and trimethylolpropane triacrylate (i.e., the total mass of the phosphorus-containing polymer precursor and crosslinking agent) is too large to account for the total mass of the mixed slurry, the viscosity of the polymer coating will be too high, making it difficult to achieve a uniform coating effect and resulting in an uneven polymer coating.

[0133] As can be seen from the comparison between Example 1 and Examples 11-12, if the mass ratio of graphene oxide (conductive filler) is too small, the porous structure in the subsequently formed polymer will be destroyed, which is not conducive to the sodium metal deposition effect; if the mass ratio of graphene oxide (conductive filler) is too large, the conductivity of the negative electrode substrate will be insufficient and the battery polarization will be too large, which is not conducive to the sodium metal deposition effect.

[0134] As can be seen from the comparison between Example 1 and Examples 13-14, if the thermosetting temperature is too low, the polymer cannot be fully polymerized, which is not conducive to forming a uniform and flat polymer coating; if the thermosetting temperature is too high, the surface curing is too fast, the polymer gelation is uneven, which is not conducive to forming a porous bottom layer and a dense surface layer.

[0135] As can be seen from the comparison between Example 1 and Comparative Example 1, the sodium metal deposition performance of the negative electrode substrate provided by the present invention is significantly higher than that of the negative electrode substrate of Comparative Example 1, showing full application potential in sodium metal batteries; furthermore, the negative electrode substrate prepared by the present invention extinguishes after burning briefly for a few seconds after being ignited by a flame, indicating that the negative electrode substrate has a significant inhibitory effect on the combustion reaction.

[0136] As can be seen from the comparison between Example 1 and Comparative Example 2, if the polymer precursor does not contain phosphorus groups, the substrate lacks flame retardant effect.

[0137] As can be seen from the comparison between Example 1 and Comparative Example 3, the sodium metal deposition effect is significantly worse if no conductive filler is added.

[0138] As can be seen from the comparison between Example 1 and Comparative Example 4, the sodium metal deposition effect is significantly worse if thermal curing is not performed.

[0139] As can be seen from the comparison between Example 1 and Comparative Example 5, the sodium metal deposition effect is significantly worse without photopolymerization curing.

[0140] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method of preparing a sodium metal battery anode substrate, characterized by, The preparation method comprises the following steps: Providing a mixed slurry, wherein the mixed slurry comprises a phosphorus-containing polymer precursor, a crosslinking agent, a conductive filler and a photoinitiator; the phosphorus-containing polymer precursor comprises a nucleophilic functional group; Coating the mixed slurry on a negative electrode current collector, and then sequentially performing photopolymerization curing and thermal curing to form a polymer coating, thereby obtaining the sodium metal battery negative electrode substrate.

2. The production method according to claim 1, characterized by, The molecular formula of the phosphorus-containing polymer precursor is CH2=CR1-COO-(CH2)n-P=(X)R2R3, wherein R1 is selected from a hydrogen atom or a methyl group, n is in a range of 1-4, X is an oxygen atom or a sulfur atom, and R2 and R3 are each independently selected from any one of an alkyl group, an aryl group or a polyether chain.

3. The production method according to claim 1 or 2, characterized by, The phosphorus-containing polymer precursor comprises any one of dimethyl methacryloyloxyethyl phosphonate, 2-acrylamidoethyl phosphonate, acrylic acid-2-(diethylthiophosphoryl) methyl ester, methacrylic acid-3-(diphenylthiophosphoryl) propyl ester or acrylic acid-4-(methylphenylphosphoryl) butyl ester or a combination of at least two thereof.

4. The production method according to any one of claims 1 to 3, characterized by, The configuration method of the mixed slurry comprises: In an inert atmosphere, the phosphorus-containing polymer precursor and the crosslinking agent are mixed and dissolved in a solvent, and then the conductive filler and the photoinitiator are added and stirred and mixed to obtain the mixed slurry.

5. The method of any one of claims 1-4, wherein, The mass percentage of the phosphorus-containing polymer precursor is 20-50wt% based on the total mass of the mixed phosphorus-containing polymer precursor and the crosslinking agent; Preferably, the mass ratio of the phosphorus-containing polymer precursor and the crosslinking agent is (1-4):(4-7); Preferably, the total mass of the phosphorus-containing polymer precursor and the crosslinking agent accounts for 40-80wt%, preferably 40-60wt%, of the total mass of the mixed slurry; Preferably, the crosslinking agent comprises any one of trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethylene glycol diacrylate, trimethylolpropane triallyl ether, pentaerythritol triallyl ether or pentaerythritol tetraallyl ether or a combination of at least two thereof.

6. The method of any one of claims 1-5, wherein, The mass percentage of the conductive filler is 10-30wt% based on the mass of the polymer in the polymer coating; Preferably, the conductive filler comprises any one of graphene oxide, carbon nanotube, ketjen black or acetylene black or a combination of at least two thereof; Preferably, the mass percentage of the photoinitiator is 0.5-6wt% based on the mass of the polymer in the polymer coating.

7. The method of any one of claims 1-6, wherein, The temperature of the thermal curing is 80-120℃, and the time is 0.5-2h; Preferably, the polymer coating has a gradient structure, and the gradient structure comprises a porous bottom layer and a dense surface layer; Preferably, the thickness of the polymer coating is 50-100μm.

8. The method of any one of claims 1-7, wherein, The preparation method comprises the following steps: (1) preparing a mixed slurry, and the specific steps comprise: In an inert atmosphere, the phosphorus-containing polymer precursor and the crosslinking agent are mixed and dissolved in a solvent, and then the conductive filler and the photoinitiator are added and stirred and mixed to obtain the mixed slurry; The mass ratio of the phosphorus-containing polymer precursor and the crosslinking agent is (1-4):(4-7); the total mass of the phosphorus-containing polymer precursor and the crosslinking agent accounts for 40-80wt% of the total mass of the mixed slurry; the phosphorus-containing polymer precursor comprises any one or a combination of at least two of dimethyl methacryloyloxyethyl phosphonate, 2-acrylamidoethyl phosphonic acid, acrylic acid-2-(diethylthiophosphoryl) methyl ester, methacrylic acid-3-(diphenylthiophosphoryl) propyl ester or acrylic acid-4-(methylphenylphosphoryl) butyl ester; the solvent is any one or a combination of at least two of water, acetone, n-hexane, dimethyl sulfoxide, N,N-dimethylformamide, isopropyl alcohol, tetrahydrofuran or dichloromethane; and the photoinitiator comprises any one or a combination of at least two of 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, bis(2,4,6-trimethylbenzoyl) phenyl phosphine oxide, diphenyl iodonium hexafluorophosphate or alpha-hydroxyisobutyryl benzene. (2) The mixed slurry is coated on the surface of the negative current collector, and then photo-polymerization curing is performed by irradiation with ultraviolet light having an intensity of 2-10 mW / cm 2 for 10-20 min, followed by thermal curing at a temperature of 80-120 °C for 0.5-2 h to form a polymer coating layer having a thickness of 50-100 μm, thereby obtaining a sodium metal battery negative electrode substrate.

9. A sodium metal battery anode substrate, characterized by, The sodium metal battery negative electrode substrate is prepared by the preparation method in any one of claims 1-8.

10. A sodium metal battery, characterized by, The sodium metal battery comprises the sodium metal battery negative electrode substrate in claim 9.

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