A wood-based energy storage building material that is self-adaptive to ambient temperature and a preparation method thereof

Abstract

The present invention discloses a wood-based energy storage building material that is self-adapting to ambient temperature and a preparation method thereof. The building material comprises a matrix layer, a functional layer and a conductive interface layer, wherein the functional layer is a phase-change microcapsule, the core material of the phase-change microcapsule is a bio-based fatty acid, the wall material of the phase-change microcapsule is a lignin-methyl methacrylate graft copolymer, and the conductive interface layer is a polydopamine-reduced graphene oxide composite coating. The present invention divides the wood-based energy storage building material into a matrix layer, a functional layer and an interface layer for synergistic optimization, thereby taking into account both mechanical properties and energy storage efficiency. The porous structure of the carbonized wood is used to form a double-layer capacitor after carbonization of wood to impart energy storage function, and heat energy storage and release are achieved by loading the phase-change microcapsules, thereby enabling the building material to have temperature self-adaptation capability. The lignin graft polymer is used as the wall material to encapsulate the bio-based phase-change core material in the microcapsule to prevent leakage of the phase-change material.

Description

Technical Field

[0001] The present invention relates to the field of multifunctional building materials and energy storage technology, and in particular to a wood-based energy storage building material that is adaptive to ambient temperature and a preparation method thereof. Background Art

[0002] Wood-based energy storage building materials are a new type of composite material that combines wood with energy storage technology, aiming to achieve both structural and energy storage functions. By combining the natural properties of wood with the electrochemical properties of energy storage materials, these materials offer innovative solutions for green buildings and sustainable energy systems. After physical or chemical treatment, the porous structure, cellulose, lignin, and other components of wood can be used as a substrate or conductive carrier for energy storage materials.

[0003] In traditional wood building materials, ordinary wood is only used as a structural material and lacks energy storage and temperature regulation functions. It cannot meet the needs of modern buildings for energy self-sufficiency and intelligent temperature control. In addition, traditional phase change materials are prone to leakage when used directly, and have weak bonding with the wood matrix, and their performance degrades seriously after long-term use. Therefore, the present invention proposes a wood-based energy storage building material that is adaptive to ambient temperature and a preparation method thereof to solve the problems existing in the prior art. Summary of the Invention

[0004] In response to the above problems, the present invention aims to provide a wood-based energy storage building material that is self-adaptive to ambient temperature and a preparation method thereof. The wood-based energy storage building material that is self-adaptive to ambient temperature and the preparation method thereof of phase-change microcapsules are divided into a matrix layer, a functional layer and an interface layer for synergistic optimization, taking into account both mechanical properties and energy storage efficiency.

[0005] By carbonizing wood to form a porous matrix, the porous structure of the carbonized wood is used to form a double-layer capacitor, giving it energy storage function. Thermal energy storage and release are achieved by loading phase-change microcapsules, making the building material temperature-adaptive.

[0006] By using lignin grafted polymer as the wall material, the bio-based phase change core material is wrapped in microcapsules to prevent leakage of the phase change material, and the microcapsules are embedded in the pores of the wood to enhance the bonding strength between the material and the matrix.

[0007] To achieve the purpose of the present invention, the present invention is implemented through the following technical solutions: a wood-based energy storage building material that is self-adaptive to ambient temperature and a preparation method thereof, comprising a base layer, a functional layer and a conductive interface layer, wherein the functional layer is a phase change microcapsule, the core material of the phase change microcapsule is a bio-based fatty acid, the wall material of the phase change microcapsule is a lignin-methyl methacrylate graft copolymer, and the conductive interface layer is a polydopamine-reduced graphene oxide composite coating.

[0008] A further improvement is that the base layer is made of balsa wood with a density of 0.1-0.3 g / cm³ and is reinforced using a gradient carbonization process.

[0009] A further improvement is that the mass ratio of polydopamine to reduced graphene oxide in the polydopamine-reduced graphene oxide composite coating is 1:2.

[0010] The following steps are involved:

[0011] Step 1: Raw material pretreatment: Balsa wood is selected as the raw material and cut into boards with a thickness of 5 to 20 mm. The surface is polished to remove burrs. The wood is immersed in a NaOH solution for 48 to 72 hours to remove some lignin and hemicellulose and improve pore connectivity. The wood is then rinsed with deionized water until neutral and dried in a vacuum environment at 60°C for 12 hours.

[0012] Step 2: Gradient carbonization: Place the wood pretreated in step 1 in a tube furnace and heat it to 400°C at 5°C / min, keep it warm for 1 hour, then continue to heat it to 700-800°C at 3°C / min, keep it warm for 2-3 hours to form a porous carbon matrix, and finally cool it naturally to room temperature to obtain carbonized wood;

[0013] Step 3: Cellulose reinforcement: immerse the carbonized wood in a nanocellulose solution and vacuum-treat for 2 hours, then dry at 60°C; repeat this three times to form a three-dimensional reinforced network;

[0014] Step 4: Microcapsule preparation and encapsulation: The bio-based fatty acid mixture is heated to 80°C and magnetically stirred at 300 rpm until completely melted as the core material. Lignin is dispersed in deionized water and methyl methacrylate (MMA) monomer is added. Ammonium persulfate with a concentration of 1 wt% is added to the solution to obtain a lignin-PMMA graft copolymer (lignin-methyl methacrylate graft copolymer) solution as the wall material. The core material is added to the wall material solution to form an oil-in-water emulsion. The temperature is raised to 60°C and stirred continuously to allow the wall material to polymerize on the surface of the core material to form microcapsules.

[0015] Step 5: Circular impregnation: The microcapsules formed in step 4 are dispersed in 30 wt% ethanol. The carbonized wood prepared in step 2 is then placed in an impregnation tank, vacuumed to 0.1 MPa for 30 minutes, and then pressurized to 2 MPa for 1 hour. The vacuum-pressure cycle is repeated three times to allow the microcapsules to embed into the pores of the wood.

[0016] Step 6: Preparation of the surface conductive layer: dissolve dopamine hydrochloride at a concentration of 2 mg / mL in Tris buffer and stir for 24 hours to form a polydopamine solution, then add a mixed graphene oxide dispersion at a concentration of 2 mg / mL, and evenly spray the mixture on the surface of the wood loaded with microcapsules. After curing, a continuous conductive layer is formed.

[0017] A further improvement is that in step 1, the concentration of the NaOH solution is 1-3 mol / L and the temperature is 60-80°C.

[0018] A further improvement is that the concentration of the nanocellulose solution in step three is 5 wt%.

[0019] A further improvement is that in step 4, the mass ratio of lignin to methyl methacrylate monomer is 1:2.

[0020] A further improvement is that in step six, the thickness of the conductive layer is 150±20 nm, and the square resistance is ≤10 Ω / sq.

[0021] The beneficial effects of the present invention are as follows: the present invention divides the wood-based energy storage building material into a matrix layer, a functional layer and an interface layer for coordinated optimization, thereby taking into account both mechanical properties and energy storage efficiency;

[0022] By carbonizing wood to form a porous matrix, the porous structure of the carbonized wood is used to form a double-layer capacitor, giving it energy storage function. Thermal energy storage and release are achieved by loading phase-change microcapsules, making the building material temperature-adaptive.

[0023] By using lignin grafted polymer as the wall material, the bio-based phase change core material is wrapped in microcapsules to prevent leakage of the phase change material, and the microcapsules are embedded in the pores of the wood to enhance the bonding strength between the material and the matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the steps of the present invention. DETAILED DESCRIPTION

[0025] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples. The examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0026] The raw materials used in the examples and comparative examples of the present invention were all obtained through conventional commercial routes, wherein the bio-based fatty acid was lauric acid and palmitic acid mixed in equal weight proportions.

[0027] according to Figure 1 As shown, this embodiment provides a wood-based energy storage building material that is self-adaptive to ambient temperature, including a base layer, a functional layer and a conductive interface layer. The functional layer is a phase change microcapsule, the core material of the phase change microcapsule is a bio-based fatty acid, the wall material of the phase change microcapsule is a lignin-methyl methacrylate graft copolymer, and the conductive interface layer is a polydopamine-reduced graphene oxide composite coating. The base layer is made of balsa wood with a density of 0.3 g / cm³. It is enhanced by a gradient carbonization process. The mass ratio of polydopamine to reduced graphene oxide in the polydopamine-reduced graphene oxide composite coating is 1:2.

[0028] The following steps are involved:

[0029] Step 1: Raw material pretreatment: Balsa wood was selected as the raw material and cut into 10 mm thick boards. The surface was polished to remove burrs. The wood was immersed in a NaOH solution for 48 hours to remove some lignin and hemicellulose and improve pore connectivity. The wood was then rinsed with deionized water until neutral and dried in a vacuum environment at 60°C for 12 hours.

[0030] The concentration of NaOH solution is 2 mol / L, and the temperature is 80°C. Alkali treatment is used to remove lignin and hemicellulose, optimize the pore structure of the wood, and dissolve part of the lignin and hemicellulose in the NaOH solution to form more through pores, providing channels for subsequent carbonization and material loading. The dried wood structure is more stable and suitable for subsequent high-temperature carbonization.

[0031] Step 2: Gradient carbonization: Place the wood pretreated in step 1 in a tube furnace and heat it to 400°C at 5°C / min, keep it warm for 1 hour to remove residual moisture, then continue to heat it to 750°C at 3°C / min, keep it warm for 2.5 hours to form a porous carbon matrix, and finally naturally cool it to room temperature to obtain carbonized wood. The wood is treated at high temperature in stages to form a porous carbon matrix. High-temperature carbonization generates a high-porosity carbon skeleton, which provides a large specific surface area and load space. The temperature is increased in stages to avoid thermal stress from damaging the structure, retaining the pore integrity. Carbonization enhances the conductivity of the matrix while retaining the lightweight properties of the wood.

[0032] Step 3: Cellulose reinforcement: The carbonized wood is immersed in a nanocellulose solution and vacuum-treated for 2 hours, then dried at 60°C; this is repeated three times to form a three-dimensional reinforced network. The nanocellulose fills the pores and forms a cross-linked network, significantly improving the compression and crack resistance of the carbonized wood. The three immersion-drying cycles ensure that the nanocellulose is evenly distributed, preventing pore collapse during subsequent loading.

[0033] The concentration of nanocellulose solution was 5 wt%.

[0034] Step 4: Preparation and encapsulation of microcapsules: heat the bio-based fatty acid mixture to 80°C, and stir magnetically at 300 rpm until completely melted as the core material; disperse lignin in deionized water and add methyl methacrylate monomer; add ammonium persulfate with a concentration of 1 wt% to the solution to obtain a lignin-methyl methacrylate graft copolymer solution as the wall material; add the core material to the wall material solution to form an oil-in-water emulsion; heat to 60°C and continue stirring to polymerize the wall material on the surface of the core material to form microcapsules; achieve heat absorption / release through the bio-based fatty acid core material, improve the thermal management ability of the material; and prevent the core material from leaking by combining the biodegradability of lignin with the mechanical strength of P methyl methacrylate through the lignin-methyl methacrylate graft copolymer wall material;

[0035] The mass ratio of lignin to methyl methacrylate monomer is 1:2.

[0036] Step 5: Circular impregnation: disperse the microcapsules formed in step 4 in 30 wt% ethanol, then place the carbonized wood prepared in step 2 in an impregnation tank, evacuate to 0.1 MPa for 30 minutes, then pressurize to 2 MPa for 1 hour, repeat the vacuum-pressure cycle three times, so that the microcapsules are embedded in the pores of the wood. The cyclic pressure difference is used to force the microcapsules into the pores, thereby increasing the loading capacity and distribution uniformity of the phase change material.

[0037] Step 6: Preparation of the surface conductive layer: dissolve 2 mg / mL dopamine hydrochloride in Tris buffer and stir for 24 hours to form a polydopamine solution. Then add 2 mg / mL mixed graphene oxide dispersion and spray the mixture evenly on the surface of the wood loaded with microcapsules. After curing, a continuous conductive layer is formed. Polydopamine reduces graphene oxide to form a continuous conductive network, which is suitable for electromagnetic shielding or sensing applications. The spraying process achieves a uniform ultra-thin coating, taking into account both conductivity and lightweight.

[0038] The thickness of the conductive layer is 150±20 nm and the square resistance is 9Ω / sq.

[0039] Example 2

[0040] according to Figure 1 As shown, this embodiment provides a method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature, including a base layer, a functional layer and a conductive interface layer. The functional layer is a phase change microcapsule, the core material of the phase change microcapsule is a bio-based fatty acid, the wall material of the phase change microcapsule is a lignin-methyl methacrylate graft copolymer, and the conductive interface layer is a polydopamine-reduced graphene oxide composite coating. The raw material of the base layer is balsa wood with a density of 0.3 g / cm³. It is enhanced by a gradient carbonization process. The mass ratio of polydopamine to reduced graphene oxide in the polydopamine-reduced graphene oxide composite coating is 1:2.

[0041] The following steps are involved:

[0042] Step 1: Raw material pretreatment: Balsa wood was selected as the raw material and cut into 10 mm thick boards. The surface was polished to remove burrs. The wood was immersed in a NaOH solution for 55 hours to remove some lignin and hemicellulose and improve pore connectivity. The wood was then rinsed with deionized water until neutral and dried in a vacuum environment at 60°C for 12 hours.

[0043] The concentration of NaOH solution is 3 mol / L, and the temperature is 60°C. Alkali treatment is used to remove lignin and hemicellulose, optimize the pore structure of the wood, and dissolve part of the lignin and hemicellulose in the NaOH solution to form more through pores, providing channels for subsequent carbonization and material loading. The dried wood structure is more stable and suitable for subsequent high-temperature carbonization.

[0044] Step 2: Gradient carbonization: Place the wood pretreated in step 1 in a tube furnace and heat it to 400°C at 5°C / min, keep it warm for 1 hour to remove residual moisture, then continue to heat it to 800°C at 3°C / min, keep it warm for 2 hours to form a porous carbon matrix, and finally naturally cool it to room temperature to obtain carbonized wood. The wood is treated at high temperature in stages to form a porous carbon matrix. High-temperature carbonization generates a high-porosity carbon skeleton, which provides a large specific surface area and load space. The temperature is increased in stages to avoid thermal stress from damaging the structure, retaining the pore integrity. Carbonization enhances the conductivity of the matrix while retaining the lightweight properties of the wood.

[0045] Step 3: Cellulose reinforcement: The carbonized wood is immersed in a nanocellulose solution and vacuum-treated for 2 hours. The solution is then dried at 60°C and repeated three times to form a three-dimensional reinforced network. The nanocellulose fills the pores and forms a cross-linked network, significantly improving the carbonized wood's compressive and crack resistance. The three immersion-drying cycles ensure uniform distribution of the nanocellulose, preventing pore collapse during subsequent loading.

[0046] The concentration of nanocellulose solution was 5 wt%.

[0047] Step 4: Preparation and encapsulation of microcapsules: heat the bio-based fatty acid mixture to 80°C, and stir magnetically at 300 rpm until completely melted as the core material; disperse lignin in deionized water and add MMA monomer; add ammonium persulfate with a concentration of 1 wt% to the solution to obtain a lignin-PMMA graft copolymer solution as the wall material; add the core material to the wall material solution to form an oil-in-water emulsion; heat to 60°C and continue stirring to polymerize the wall material on the surface of the core material to form microcapsules; achieve heat absorption / release through the bio-based fatty acid core material, improve the thermal management ability of the material; and prevent the core material from leaking by combining the biodegradability of lignin with the mechanical strength of PMMA through the lignin-PMMA graft copolymer wall material;

[0048] The mass ratio of lignin to MMA monomer is 1:2.

[0049] Step 5: Circular impregnation: disperse the microcapsules formed in step 4 in 30 wt% ethanol, then place the carbonized wood prepared in step 2 in an impregnation tank, evacuate to 0.1 MPa for 30 minutes, then pressurize to 2 MPa for 1 hour, repeat the vacuum-pressure cycle three times, so that the microcapsules are embedded in the pores of the wood. The cyclic pressure difference is used to force the microcapsules into the pores, thereby increasing the loading capacity and distribution uniformity of the phase change material.

[0050] Step 6: Preparation of the surface conductive layer: dissolve 2 mg / mL dopamine hydrochloride in Tris buffer and stir for 24 hours to form a polydopamine solution. Then add 2 mg / mL mixed graphene oxide dispersion and spray the mixture evenly on the surface of the wood loaded with microcapsules. After curing, a continuous conductive layer is formed. Polydopamine reduces graphene oxide to form a continuous conductive network, which is suitable for electromagnetic shielding or sensing applications. The spraying process achieves a uniform ultra-thin coating, taking into account both conductivity and lightweight.

[0051] The thickness of the conductive layer is 150±20 nm and the square resistance is 9Ω / sq.

[0052] Example 3

[0053] according to Figure 1 As shown, this embodiment provides a method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature, including a base layer, a functional layer and a conductive interface layer. The functional layer is a phase change microcapsule, the core material of the phase change microcapsule is a bio-based fatty acid, the wall material of the phase change microcapsule is a lignin-methyl methacrylate graft copolymer, and the conductive interface layer is a polydopamine-reduced graphene oxide composite coating. The raw material of the base layer is balsa wood with a density of 0.3 g / cm³. It is enhanced by a gradient carbonization process. The mass ratio of polydopamine to reduced graphene oxide in the polydopamine-reduced graphene oxide composite coating is 1:2.

[0054] The following steps are involved:

[0055] Step 1: Raw material pretreatment: Balsa wood was selected as the raw material and cut into 10 mm thick boards. The surface was polished to remove burrs. The wood was immersed in a NaOH solution for 72 hours to remove some lignin and hemicellulose and improve pore connectivity. The wood was then rinsed with deionized water until neutral and dried in a vacuum environment at 60°C for 12 hours.

[0056] The concentration of NaOH solution is 1 mol / L, and the temperature is 80°C. Alkali treatment is used to remove lignin and hemicellulose, optimize the pore structure of the wood, and dissolve part of the lignin and hemicellulose in the NaOH solution to form more through pores, providing channels for subsequent carbonization and material loading. The dried wood structure is more stable and suitable for subsequent high-temperature carbonization.

[0057] Step 2: Gradient carbonization: Place the wood pretreated in step 1 in a tube furnace and heat it to 400°C at 5°C / min, keep it warm for 1 hour to remove residual moisture, then continue to heat it to 700°C at 3°C / min, keep it warm for 3 hours to form a porous carbon matrix, and finally naturally cool it to room temperature to obtain carbonized wood. The wood is treated at high temperature in stages to form a porous carbon matrix. High-temperature carbonization generates a high-porosity carbon skeleton, which provides a large specific surface area and load space. The temperature is increased in stages to avoid thermal stress from destroying the structure, retaining the pore integrity. Carbonization enhances the conductivity of the matrix while retaining the lightweight characteristics of the wood.

[0058] Step 3: Cellulose reinforcement: The carbonized wood is immersed in a nanocellulose solution and vacuum-treated for 2 hours. The solution is then dried at 60°C and repeated three times to form a three-dimensional reinforced network. The nanocellulose fills the pores and forms a cross-linked network, significantly improving the carbonized wood's compressive and crack resistance. The three immersion-drying cycles ensure uniform distribution of the nanocellulose, preventing pore collapse during subsequent loading.

[0059] The concentration of nanocellulose solution was 5 wt%.

[0060] Step 4: Preparation and encapsulation of microcapsules: heat the bio-based fatty acid mixture to 80°C, and stir magnetically at 300 rpm until completely melted as the core material; disperse lignin in deionized water and add MMA monomer; add ammonium persulfate with a concentration of 1 wt% to the solution to obtain a lignin-PMMA graft copolymer solution as the wall material; add the core material to the wall material solution to form an oil-in-water emulsion; heat to 60°C and continue stirring to polymerize the wall material on the surface of the core material to form microcapsules; achieve heat absorption / release through the bio-based fatty acid core material, improve the thermal management ability of the material; and prevent the core material from leaking by combining the biodegradability of lignin with the mechanical strength of PMMA through the lignin-PMMA graft copolymer wall material;

[0061] The mass ratio of lignin to MMA monomer is 1:2.

[0062] Step 5: Circular impregnation: disperse the microcapsules formed in step 4 in 30 wt% ethanol, then place the carbonized wood prepared in step 2 in an impregnation tank, evacuate to 0.1 MPa for 30 minutes, then pressurize to 2 MPa for 1 hour, repeat the vacuum-pressure cycle three times, so that the microcapsules are embedded in the pores of the wood. The cyclic pressure difference is used to force the microcapsules into the pores, thereby increasing the loading capacity and distribution uniformity of the phase change material.

[0063] Step 6: Preparation of the surface conductive layer: dissolve 2 mg / mL dopamine hydrochloride in Tris buffer and stir for 24 hours to form a polydopamine solution. Then add 2 mg / mL mixed graphene oxide dispersion and spray the mixture evenly on the surface of the wood loaded with microcapsules. After curing, a continuous conductive layer is formed. Polydopamine reduces graphene oxide to form a continuous conductive network, which is suitable for electromagnetic shielding or sensing applications. The spraying process achieves a uniform ultra-thin coating, taking into account both conductivity and lightweight.

[0064] The thickness of the conductive layer is 150±20 nm and the square resistance is 9 Ω / sq.

[0065] Comparative Example 1

[0066] A method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature includes a base layer and a functional layer. The functional layer is a phase-change microcapsule, the core material of the phase-change microcapsule is a bio-based fatty acid, and the wall material of the phase-change microcapsule is a lignin-methyl methacrylate graft copolymer.

[0067] The following steps are involved:

[0068] Step 1: Raw material pretreatment: Balsa wood was selected as the raw material and cut into 10 mm thick boards. The surface was polished to remove burrs. The wood was immersed in a NaOH solution for 48 hours to remove some lignin and hemicellulose and improve pore connectivity. The wood was then rinsed with deionized water until neutral and dried in a vacuum environment at 60°C for 12 hours.

[0069] The concentration of NaOH solution is 2 mol / L, and the temperature is 80°C. Alkali treatment is used to remove lignin and hemicellulose, optimize the pore structure of the wood, and dissolve part of the lignin and hemicellulose in the NaOH solution to form more through pores, providing channels for subsequent carbonization and material loading. The dried wood structure is more stable and suitable for subsequent high-temperature carbonization.

[0070] Step 2: Gradient carbonization: Place the wood pretreated in step 1 in a tube furnace and heat it to 400°C at 5°C / min, keep it warm for 1 hour to remove residual moisture, then continue to heat it to 750°C at 3°C / min, keep it warm for 2.5 hours to form a porous carbon matrix, and finally naturally cool it to room temperature to obtain carbonized wood. The wood is treated at high temperature in stages to form a porous carbon matrix. High-temperature carbonization generates a high-porosity carbon skeleton, which provides a large specific surface area and load space. The temperature is increased in stages to avoid thermal stress from damaging the structure, retaining the pore integrity. Carbonization enhances the conductivity of the matrix while retaining the lightweight properties of the wood.

[0071] Step 3: Cellulose reinforcement: The carbonized wood is immersed in a nanocellulose solution and vacuum-treated for 2 hours. The solution is then dried at 60°C and repeated three times to form a three-dimensional reinforced network. The nanocellulose fills the pores and forms a cross-linked network, significantly improving the carbonized wood's compressive and crack resistance. The three immersion-drying cycles ensure uniform distribution of the nanocellulose, preventing pore collapse during subsequent loading.

[0072] The concentration of nanocellulose solution was 5 wt%.

[0073] Step 4: Preparation and encapsulation of microcapsules: heat the bio-based fatty acid mixture to 80°C, and stir magnetically at 300 rpm until completely melted as the core material; disperse lignin in deionized water and add MMA monomer; add ammonium persulfate with a concentration of 1 wt% to the solution to obtain a lignin-PMMA graft copolymer solution as the wall material; add the core material to the wall material solution to form an oil-in-water emulsion; heat to 60°C and continue stirring to polymerize the wall material on the surface of the core material to form microcapsules; achieve heat absorption / release through the bio-based fatty acid core material, improve the thermal management ability of the material; and prevent the core material from leaking by combining the biodegradability of lignin with the mechanical strength of PMMA through the lignin-PMMA graft copolymer wall material;

[0074] The mass ratio of lignin to MMA monomer is 1:2.

[0075] Step 5: Circular impregnation: disperse the microcapsules formed in step 4 in 30 wt% ethanol, then place the carbonized wood prepared in step 2 in an impregnation tank, evacuate to 0.1 MPa for 30 minutes, then pressurize to 2 MPa for 1 hour, repeat the vacuum-pressure cycle three times, so that the microcapsules are embedded in the pores of the wood. The cyclic pressure difference is used to force the microcapsules into the pores, thereby increasing the loading capacity and distribution uniformity of the phase change material.

[0076] Comparative Example 2

[0077] A method for preparing a wood-based energy storage building material that is adaptive to ambient temperature includes a base layer, a functional layer, and a conductive interface layer. The functional layer is made of bio-based fatty acids, and the conductive interface layer is a polydopamine-reduced graphene oxide composite coating. The base layer is made of balsa wood with a density of 0.3 g / cm³ and is reinforced using a gradient carbonization process. The mass ratio of polydopamine to reduced graphene oxide in the polydopamine-reduced graphene oxide composite coating is 1:2.

[0078] The following steps are involved:

[0079] Step 1: Raw material pretreatment: Balsa wood was selected as the raw material and cut into 10 mm thick boards. The surface was polished to remove burrs. The wood was immersed in a NaOH solution for 48 hours to remove some lignin and hemicellulose and improve pore connectivity. The wood was then rinsed with deionized water until neutral and dried in a vacuum environment at 60°C for 12 hours.

[0080] The concentration of NaOH solution is 2 mol / L, and the temperature is 80°C. Alkali treatment is used to remove lignin and hemicellulose, optimize the pore structure of the wood, and dissolve part of the lignin and hemicellulose in the NaOH solution to form more through pores, providing channels for subsequent carbonization and material loading. The dried wood structure is more stable and suitable for subsequent high-temperature carbonization.

[0081] Step 2: Gradient carbonization: Place the wood pretreated in step 1 in a tube furnace and heat it to 400°C at 5°C / min, keep it warm for 1 hour to remove residual moisture, then continue to heat it to 750°C at 3°C / min, keep it warm for 2.5 hours to form a porous carbon matrix, and finally naturally cool it to room temperature to obtain carbonized wood. The wood is treated at high temperature in stages to form a porous carbon matrix. High-temperature carbonization generates a high-porosity carbon skeleton, which provides a large specific surface area and load space. The temperature is increased in stages to avoid thermal stress from damaging the structure, retaining the pore integrity. Carbonization enhances the conductivity of the matrix while retaining the lightweight properties of the wood.

[0082] Step 3: Cellulose reinforcement: The carbonized wood is immersed in a nanocellulose solution and vacuum-treated for 2 hours. The solution is then dried at 60°C and repeated three times to form a three-dimensional reinforced network. The nanocellulose fills the pores and forms a cross-linked network, significantly improving the carbonized wood's compressive and crack resistance. The three immersion-drying cycles ensure uniform distribution of the nanocellulose, preventing pore collapse during subsequent loading.

[0083] The concentration of nanocellulose solution was 5 wt%.

[0084] Step 4: Heat the bio-based fatty acid mixture to 80°C and stir magnetically at 300 rpm until completely melted;

[0085] Step 5: Circular impregnation: disperse the bio-based fatty acids formed in step 4 in 30 wt% ethanol, then place the carbonized wood prepared in step 2 in an impregnation tank, evacuate to 0.1 MPa, hold for 30 minutes, then pressurize to 2 MPa for 1 hour, repeat the vacuum-pressure cycle 3 times, so that the bio-based fatty acids are embedded in the pores of the wood, and use the cyclic pressure difference to force the bio-based fatty acids into the pores, thereby increasing the loading capacity and distribution uniformity of the phase change material.

[0086] Step 6: Preparation of the surface conductive layer: dissolve 2 mg / mL of dopamine hydrochloride in Tris buffer and stir for 24 hours to form a polydopamine solution. Then, add a 2 mg / mL mixed graphene oxide dispersion. The mixture is evenly sprayed on the surface of the wood loaded with bio-based fatty acids. After curing, a continuous conductive layer is formed. Polydopamine reduces graphene oxide to form a continuous conductive network suitable for electromagnetic shielding or sensing applications. The spraying process achieves a uniform ultra-thin coating that combines conductivity with lightweight.

[0087] The thickness of the conductive layer is 150±20 nm and the square resistance is 8Ω / sq.

[0088] The performance of the wood-based energy storage building materials that are self-adaptive to ambient temperature prepared in Examples 1-3 and Comparative Examples 1-2 was tested:

[0089] Due to the reinforcement of nanocellulose and uniform loading of microcapsules, the compressive / flexural strength of Examples 1-3 is significantly higher than that of Comparative Example 2. The microcapsule structure of the examples effectively prevents leakage, and the enthalpy loss rate is ≤8% after 100 cycles; due to the direct impregnation of bio-based fatty acids in Comparative Example 2, the enthalpy loss rate caused by leakage is as high as 32.6%. The square resistance of the conductive layer of Examples 1-3 is ≤10Ω / sq, which meets the electromagnetic shielding requirements; Comparative Example 1 has no conductive layer and the square resistance is >1000Ω / sq; Due to the leakage of fatty acids affecting the continuity of the coating in Comparative Example 2, the square resistance increases to 12.5Ω / sq, the phase change range of the examples is stable (20-30℃), and the stabilization time in the environmental adaptability test is more than 6 hours; Due to leakage and uneven distribution of phase change materials, the stabilization time of Comparative Example 2 is only 3.1 hours. The porosity of the examples is ≥80%, and the microcapsule loading rate is ≥93%. Due to the clogging of pores by fatty acids in Comparative Example 2, the porosity is only 65% ​​and there is no encapsulation structure.

[0090] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a wood-based energy storage building material that is adaptive to ambient temperature, the wood-based energy storage building material comprising a base layer, a functional layer, and a conductive interface layer, the functional layer being a phase-change microcapsule, the core material of the phase-change microcapsule being a bio-based fatty acid, the wall material of the phase-change microcapsule being a lignin-methyl methacrylate graft copolymer, and the conductive interface layer being a polydopamine-reduced graphene oxide composite coating, the method comprising the following steps: Step 1: Raw material pretreatment: Balsa wood is selected as the raw material and cut into boards with a thickness of 5 to 20 mm. The surface is polished to remove burrs. The wood is immersed in a NaOH solution for 48 to 72 hours to remove some lignin and hemicellulose and improve pore connectivity. The wood is then rinsed with deionized water until neutral and dried in a vacuum environment at 60°C for 12 hours. Step 2: Gradient carbonization: Place the wood pretreated in step 1 in a tube furnace and heat it to 400°C at 5°C / min, keep it warm for 1 hour, then continue to heat it to 700-800°C at 3°C / min, keep it warm for 2-3 hours to form a porous carbon matrix, and finally cool it naturally to room temperature to obtain carbonized wood; Step 3: Cellulose reinforcement: immerse the carbonized wood in a nanocellulose solution and vacuum-treat for 2 hours, then dry at 60°C; repeat this three times to form a three-dimensional reinforced network; Step 4: Microcapsule preparation and encapsulation: The bio-based fatty acid mixture is heated to 80°C and magnetically stirred at 300 rpm until completely melted as the core material. Lignin is dispersed in deionized water and methyl methacrylate monomer is added. Ammonium persulfate with a concentration of 1 wt% is added to the solution to obtain a lignin-methyl methacrylate graft copolymer solution as the wall material. The core material is added to the wall material solution to form an oil-in-water emulsion. The temperature is raised to 60°C and stirred continuously to allow the wall material to polymerize on the surface of the core material to form microcapsules. Step 5: Circular impregnation: The microcapsules formed in step 4 are dispersed in 30 wt% ethanol. The carbonized wood prepared in step 2 is then placed in an impregnation tank, vacuumed to 0.1 MPa for 30 minutes, and then pressurized to 2 MPa for 1 hour. The vacuum-pressure cycle is repeated three times to allow the microcapsules to embed into the pores of the wood. Step 6: Preparation of the surface conductive layer: dissolve dopamine hydrochloride at a concentration of 2 mg / mL in Tris buffer and stir for 24 hours to form a polydopamine solution, then add a mixed graphene oxide dispersion at a concentration of 2 mg / mL, and evenly spray the mixture on the surface of the wood loaded with microcapsules. After curing, a continuous conductive layer is formed.

2. The method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature according to claim 1, characterized in that: The base layer is made of balsa wood with a density of 0.1-0.3 g / cm³ and is reinforced using a gradient carbonization process.

3. The method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature according to claim 1, characterized in that: The mass ratio of polydopamine to reduced graphene oxide in the polydopamine-reduced graphene oxide composite coating is 1:

2.

4. The method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature according to claim 1, characterized in that: In step 1, the concentration of the NaOH solution is 1-3 mol / L, and the temperature is 60-80°C.

5. The method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature according to claim 1, characterized in that: The concentration of the nanocellulose solution in step 3 is 5 wt%.

6. The method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature according to claim 1, characterized in that: In the step 4, the mass ratio of lignin to methyl methacrylate monomer is 1:

2.

7. The method for preparing a wood-based energy storage building material that is self-adaptive to ambient temperature according to claim 1, characterized in that: In step six, the conductive layer has a thickness of 150±20 nm and a sheet resistance of ≤10 Ω / sq.

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