Gradient pore structure composite electrode material based on 3D printing technology and preparation method thereof

Abstract

The invention discloses a gradient pore structure composite electrode based on a 3D printing technology and a preparation method thereof. The method comprises the steps that (1) a 3D printing technology is adopted to construct a three-dimensional porous framework, the three-dimensional porous framework is composed of a plurality of pore layers and supporting layers located between every two adjacent pore layers and playing a supporting role, pores in the pore layers are arranged in an array mode, the pores in the upper layer and the pores in the lower layer are opposite, and the supporting layers are arranged in an array mode; the pore size is in gradient change from the bottom layer to the top layer in the thickness direction of the material, the supporting layer is composed of a plurality of vertical stand columns, is connected with the pores of the upper pore layer and the lower pore layer and jointly forms a cubic three-dimensional pore structure, and the size of the three-dimensional pores in the thickness direction of the material is in gradient change; (2) carrying out carbonization treatment or coating a conductive coating; and (3) electrochemically depositing a zinc layer. By regulating and controlling the pore structure and distribution of the three-dimensional skeleton, the deposition behavior of the zinc ions is regulated, and efficient transmission and uniform deposition of the zinc ions are realized, so that the performance of the zinc negative electrode is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage materials and advanced manufacturing technologies, and particularly relates to a gradient structure composite electrode of 3D printing technology and a preparation method thereof. Background Art

[0002] With the rapid development of renewable energy sources (such as wind energy, solar energy, tidal energy, and geothermal energy), constructing an efficient and stable electrochemical energy storage system has become the key to realizing the transformation of the energy structure. Among various secondary battery systems, aqueous zinc-ion batteries have attracted much attention due to their intrinsic safety characteristics, low manufacturing cost, and environmental friendliness. As a negative electrode material, Zn metal not only has a high theoretical capacity and a low redox potential but also exhibits excellent compatibility with aqueous electrolytes and rich resource reserves. However, during the deposition / stripping process of zinc ions, dendrite structures are easily formed on the surface of the zinc negative electrode, and their sharp morphology may penetrate the separator and cause a short circuit, severely restricting the cycle life and practical application process of the battery.

[0003] The three-dimensional skeleton can significantly reduce the local current density by increasing the effective surface area of the electrode and simultaneously homogenize the interfacial electric field distribution, thereby delaying dendrite formation. However, the existing preparation technologies of three-dimensional skeletons (such as the template method, chemical vapor deposition, powder sintering, etc.) generally have problems such as complex processes (requiring high-temperature treatment or multi-step processing), single structures (such as only cubic pores or honeycomb pores), and insufficient precision (it is difficult to control micron-scale pores). In addition, the three-dimensional skeletons prepared by traditional methods usually have a uniform pore distribution, resulting in zinc ions preferentially depositing on the outer surface and pore entrances of the skeleton, while the internal pores are difficult to be effectively utilized due to the large ion transport resistance. This deposition non-uniformity not only limits the capacity of the electrode but also may cause the collapse of the skeleton structure due to local volume expansion. Therefore, how to precisely control the pore structure and composition distribution of the three-dimensional skeleton to achieve efficient transmission and uniform deposition of zinc ions is the key problem in improving the performance of the zinc negative electrode. Summary of the Invention

[0004] The purpose of the present invention is to provide, in view of the deficiencies of the prior art, a gradient pore structure composite electrode based on 3D printing technology and a preparation method thereof, which can regulate the deposition behavior of zinc ions by controlling the pore structure and distribution of the three-dimensional skeleton, achieve efficient transmission and uniform deposition of zinc ions, and thus improve the performance of the zinc negative electrode.

[0005] The preparation method of the gradient pore structure composite electrode material based on 3D printing technology provided by the present invention includes the following steps: (1) A three-dimensional porous framework is constructed using 3D printing technology. The three-dimensional porous framework is composed of multiple pore layers and support layers located between adjacent pore layers for support. The pores on the pore layers are arranged in an array, and the pores in the upper and lower layers are opposite to each other. The pore sizes vary in a gradient from the bottom layer to the top layer in the material thickness direction. The support layers are a number of vertical columns that connect the pores of the upper and lower pore layers and jointly form a cubic three-dimensional pore structure. The sizes of the three-dimensional pores vary in a gradient in the material thickness direction.

[0006] (2) The three-dimensional porous framework obtained in step (1) is carbonized or coated with a conductive coating to form a conductive matrix. (3) A zinc layer is deposited on the surface of the conductive matrix obtained in step (2) through an electrochemical deposition process to obtain a composite electrode material with a gradient pore structure.

[0007] Further, the 3D printing technology in step (1) includes but is not limited to one of fused deposition modeling (FDM), stereolithography (SLA), digital light processing (DLP), liquid crystal display stereolithography (LCD), and continuous liquid interface production (CLIP).

[0008] Further, when the 3D printing in step (1) uses FDM technology, the printing raw materials include but are not limited to one or several of polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG), nylon, and thermoplastic polyurethane (TPU).

[0009] Further, when the 3D printing in step (1) uses SLA, DLP, LCD, or CLIP technology, the printing raw materials include but are not limited to one or several of polyethylene glycol diacrylate (PEGDA), epoxy acrylate, polyurethane acrylate, polyacrylic acid, polyacrylamide (PAM), sodium alginate, phenolic epoxy acrylate, and polyurethane dimethacrylate.

[0010] Further, when the 3D printing in step (1) uses SLA, DLP, LCD, or CLIP technology, the printing ink is prepared before printing. The preparation method of the printing ink is as follows: First, dissolve the printing raw materials in a solvent, then mix with a dispersion of a light-shielding agent, and then add a solution of a photoinitiator and mix evenly. Among them, the mass ratio of the raw material to the light-shielding agent is (10 - 1000):1; the mass ratio of the raw material to the photoinitiator is (50 - 10000):1.

[0011] Preferably, the light-shielding agent is PEGDA, and the photoinitiator is triethanolamine and eosin Y.

[0012] Further, during the printing in step (1), the pore size of the bottom layer of the three-dimensional porous skeleton pore layer is set to be 5 μm × 5 μm to 50 μm × 50 μm, and the pore size of the top layer is 50 μm × 50 μm to 400 μm × 400 μm; the spacing (layer height) between adjacent two layers is 0.2 to 1 mm.

[0013] Further, during the printing in step (1), the thickness of the composite electrode material is set to be 1 to 4 mm.

[0014] Further, in step (2), the carbonization treatment is carried out in an inert atmosphere at a carbonization temperature of 400 to 1000 °C for a carbonization time of 2 to 24 h.

[0015] Further, the method for coating the conductive coating in step (2) includes but is not limited to one of spraying, dip coating, and in-situ growth.

[0016] Further, the conductive coating material in step (2) includes but is not limited to one or more of carbon nanotubes (CNT), graphene, silver nanoparticles, MXene, nickel, and copper.

[0017] Further, in step (3), the electrochemical deposition process is constant voltage deposition, the deposition voltage is -0.9 to -2 V, and the time is 0.05 to 2 h.

[0018] Further, the deposition solution for the electrochemical deposition process in step (3) includes but is not limited to one or more of ZnSO4 solution, ZnCl2 solution, Zn(NO3)2 solution, Zn(Ac)2 solution, and Zn(OTf)2 solution.

[0019] Further, one or more of Na2SO4 solution, NaCl solution, and NaNO3 solution are added to the deposition solution for the electrochemical deposition process in step (3) to regulate the deposition behavior of zinc ions.

[0020] The present invention also provides a composite electrode material with a gradient pore structure prepared by the above method.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The gradient pore structure composite electrode constructed by the 3D printing technology in the present invention, when assembling the battery, the gradient pore structure of the electrode shows a decreasing distribution of pore size along the direction from the separator to the current collector, which not only ensures the efficient transmission of the electrolyte but also can homogenize the electric field distribution, thereby effectively regulating the deposition behavior of zinc ions and realizing the 2+ efficient transmission and uniform deposition of Zn, inhibiting dendrite growth, and at the same time improving the utilization rate of the electrode active material. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the sample of the embodiment. a is the schematic structural diagram of the whole, and b and c are the schematic structural diagrams of each layer after being split.

[0023] Figure 2 It is an SEM image of the side of the CCP conductive skeleton.

[0024] Figure 3 It is an SEM image of the side of the Zn@CCP electrode.

[0025] Figure 4 It is a schematic assembly diagram of the Zn@CCP electrode and the battery separator.

[0026] Figure 5 It is the cyclic charge-discharge voltage curves of zinc symmetric batteries assembled using zinc foil (a), electrode with uniform pores (b), and Zn@CCP electrode (c) respectively under the test conditions of 1 mA / cm 2 , 1 mAh / cm 2 . Specific Embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Example 1 A preparation method of a Zn / CNT / PEGDA composite electrode with a gradient pore structure is as Figure 1 shown, and specifically includes: (1) Preparation of the CNT / PEGDA porous skeleton with a gradient structure: First, a 33.3 wt% PEGDA solution and a 0.5 wt% CNT dispersion liquid are stirred and mixed at a mass ratio of 1:2. Then, a photoinitiator (0.1 wt% triethanolamine and 0.007 wt% eosin Y) is added and stirred for 30 min to obtain the CNT / PEGDA printing ink. The gradient structure of CNT / PEGDA is printed using a CLIP three-dimensional printer. During the CLIP printing process, the slice thickness and exposure time of each layer are set to 5 μm and 0.1 s respectively, and a sample with a gradient pore structure is printed (the pore size of the bottom layer is 10 μm × 10 μm, the pore size of the top layer is 400 μm × 400 μm, the height of the sample is 2.8 mm, and the height of each layer is 0.4 mm). During the CLIP process, the projection is repeated first, and then the platform is raised. The printed object is thoroughly washed with water to remove the unreacted ink, and then dried under ambient conditions to obtain the CNT / PEGDA porous skeleton.

[0028] (2)Carbonization to prepare the conductive framework: Transfer the CNT / PEGDA porous framework into a quartz tube and heat it to 800 °C at a rate of 10 °C / min under a flowing argon atmosphere. Keep the sample at this temperature for 4 h, and then cool it naturally to room temperature to obtain the conductive CNT / PEGDA porous framework, named CCP.

[0029] (3)Electrodeposition to prepare the zinc composite electrode: Use the CCP conductive framework as the working electrode, a platinum electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. A 0.2 mol / L ZnSO4 + 0.1 mol / L Na2SO4 aqueous solution is used as the electrodeposition solution. Electrodeposit for 30 min at a deposition voltage of -1.5 V. Finally, rinse with deionized water and dry in an oven at 60 °C for 6 h to obtain the zinc composite electrode with a gradient pore structure, named (Zn@CCP). Material morphology characterization: The morphology of the prepared CCP side was characterized using SEM. As Figure 2 shown, the CCP presents an obvious three-dimensional porous structure, and the pore size of the framework gradually increases from top to bottom, indicating that a three-dimensional conductive framework with a gradient pore structure was successfully prepared by combining the CLIP 3D printing technology and the carbonization process.

[0030] The morphology of the further prepared Zn@CCP electrode side was characterized using SEM. As Figure 3 shown, the Zn@CCP electrode still retains an obvious gradient pore structure, and Zn nanosheets are uniformly loaded on the surface of the conductive framework.

[0031] Cyclic stability of the Zn@CCP electrode: A zinc symmetric battery was assembled using the Zn@CCP electrode, and the cyclic stability of the composite electrode was tested under the test conditions of 1 mA / cm 2 , 1 mAh / cm 2 . As Figure 4 shown, when assembling the battery, the gradient pore structure of the electrode shows a characteristic of decreasing pore size along the direction from the separator to the current collector.

[0032] The results are as Figure 5As shown, the zinc symmetric battery assembled with a pure zinc foil electrode showed obvious voltage fluctuation failure after about 260 h of cycling, which may be due to dendrite growth leading to internal soft short circuit of the battery. Thanks to the three-dimensional conductive skeleton structure, the zinc symmetric batteries assembled with composite electrodes based on the three-dimensional conductive skeleton all have longer cycle service lives. And thanks to the gradient pore structure design, the zinc symmetric battery based on the Zn@CCP electrode exhibited stable cycling for more than 1500 h, indicating that the electrode structure design of the present invention can effectively reduce dendrite growth and improve the stability of the anode material of zinc ion batteries.

[0033] Example 2 A preparation method of a Zn / Ag / PEGDA / PAM composite electrode with a gradient pore structure specifically includes: (1) Preparation of the PEGDA porous skeleton with a gradient structure: First, a 30 wt% PEGDA solution and 10 wt% acrylamide are stirred and mixed at a mass ratio of 1:2, and then a photoinitiator (0.1 wt% triethanolamine) is added and stirred for 30 min to obtain the PEGDA / PAM printing ink. The PEGDA / PAM is printed using a DLP 3D printer. During the DLP printing process, the slice thickness and exposure time of each layer are set to 10 μm and 0.1 s respectively, and a sample with a gradient pore structure is printed (the pore size of the bottom layer is 20 μm × 20 μm, the pore size of the top layer is 200 μm × 200 μm, the height of the sample is 1.5 mm, and the height of each layer is 0.3 mm). The printed object is thoroughly washed with water to remove the unreacted ink, and then dried under ambient conditions to obtain the PEGDA / PAM porous skeleton.

[0034] (2) In-situ loading of Ag to prepare the conductive skeleton: The PEGDA / PAM porous skeleton is placed in a 0.1 M AgNO3 solution, and a sufficient amount of glucose solution is slowly added, and stirring is continued for 4 h. Finally, it is rinsed with deionized water and dried in an oven at 60°C for 6 h to obtain an Ag / PEGDA / PAM conductive skeleton with Ag nanoparticles loaded on the surface.

[0035] (3) Electro-deposition to prepare the zinc composite electrode: Using the Ag / PEGDA / PAM conductive skeleton as the working electrode, a platinum electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode, an aqueous solution of 0.2M ZnSO4 + 0.1 M Na2SO4 is used as the electro-deposition solution. At a deposition voltage of -1.4V, electro-deposition is carried out for 20 min. Finally, it is rinsed with deionized water and dried in an oven at 60°C for 6 h to obtain the Zn / Ag / PEGDA / PAM composite electrode.

[0036] Example 3 A preparation method of a Zn / CNT / MXene / PEGDA composite electrode with a gradient pore structure, specifically including: (1) Preparation of a gradient-structured MXene / PEGDA porous skeleton: First, a 33.3 wt% PEGDA solution and a 0.5 wt% MXene dispersion are stirred and mixed at a mass ratio of 1:1. Then, a photoinitiator (0.1 wt% triethanolamine and 0.007 wt% eosin Y) is added and stirred for 30 min to obtain MXene / PEGDA printing ink. A gradient structure of MXene / PEGDA is printed using a CLIP 3D printer. During the CLIP printing process, the slice thickness and exposure time of each layer are set to 5 μm and 0.1 s, respectively, to print a gradient pore structure sample (the pore size of the bottom layer is 5 μm × 5 μm, the pore size of the top layer is 50 μm × 50 μm, the height of the sample is 1.4 mm, and the height of each layer is 0.2 mm). During the CLIP process, the projection is repeated first, and then the platform is raised. The printed object is thoroughly washed with water to remove the unreacted ink, and then dried under ambient conditions to obtain the MXene / PEGDA porous skeleton.

[0037] (2) Surface loading of CNT: The MXene / PEGDA porous skeleton is immersed in a 0.5 wt% CNT dispersion for 2 h, and then dried in an oven at 60°C for 6 h. This step is repeated 5 times to obtain a conductive CNT / MXene / PEGDA conductive skeleton.

[0038] (3) Preparation of a zinc composite electrode by electrodeposition: Using the CNT / MXene / PEGDA conductive skeleton as the working electrode, a platinum electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode, an aqueous solution of 0.2M ZnSO4 + 0.1 M Na2SO4 is used as the electrodeposition solution. At a deposition voltage of -1.5V, electrodeposition is carried out for 60 min. Finally, it is rinsed with deionized water and dried in an oven at 60°C for 6 h to obtain a Zn / CNT / MXene / PEGDA composite electrode with a gradient structure.

Claims

1. Preparation method of gradient pore structure composite electrode material based on 3D printing technology, characterized in that It includes the following steps: (1) Use 3D printing technology to construct a three-dimensional porous skeleton, which is composed of multiple pore layers and support layers located between adjacent pore layers for support. The pores on the pore layers are arranged in an array, and the pores in the upper and lower layers are opposite to each other. The pore size changes in a gradient from the bottom layer to the top layer in the material thickness direction. The support layer is composed of several vertical columns that connect the pores of the upper and lower pore layers and jointly form a cubic three-dimensional pore structure, and the size of the three-dimensional pores changes in a gradient in the material thickness direction; (2) Carbonize the three-dimensional porous skeleton obtained in step (1) or coat it with a conductive coating to form a conductive matrix; (3) Deposit a zinc layer on the surface of the conductive matrix obtained in step (2) through an electrochemical deposition process to obtain a composite electrode material with a gradient pore structure.

2. The method according to claim 1, characterized in that, The 3D printing technology in step (1) includes but is not limited to one of fused deposition modeling, stereolithography, digital light processing, stereolithography, and continuous liquid interface production.

3. The method according to claim 2, wherein When the 3D printing in step (1) uses FDM technology, the printing raw materials include but are not limited to one or several of polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate-1,4-cyclohexanedimethanol ester, nylon, and thermoplastic polyurethane; When the 3D printing in step (1) uses SLA, DLP, LCD, or CLIP technology, the printing raw materials include but are not limited to one or several of polyethylene glycol acrylate, epoxy acrylate, polyurethane acrylate, polyacrylic acid, polyacrylamide, sodium alginate, phenolic epoxy acrylate, and polyurethane dimethacrylate.

4. The method according to claim 1, wherein When the 3D printing in step (1) uses SLA, DLP, LCD, or CLIP technology, the printing ink is prepared before printing. The preparation method of the printing ink is as follows: First, dissolve the printing raw materials in a solvent, then mix with a dispersion of a light shielding agent, and then add a solution of a photoinitiator and mix evenly. Among them, the mass ratio of the raw material to the light shielding agent is (10 ~ 1000):1; the mass ratio of the raw material to the photoinitiator is (50 ~ 10000):

1.

5. The method according to claim 4, wherein The light shielding agent is PEGDA, and the photoinitiator is triethanolamine and eosin Y.

6. The method according to claim 1, characterized in that Further, when printing in step (1), set the bottom pore size of the pore layer of the three-dimensional porous skeleton to be 5 μm × 5 μm ~ 50 μm × 50 μm, the top pore size to be 50 μm× 50 μm ~ 400 μm × 400 μm; the distance between adjacent layers is 0.2 ~ 1 mm; set the thickness of the composite electrode material to be 1 ~ 4 mm.

7. The method according to claim 1, wherein The carbonization treatment in step (2) is carried out in an inert atmosphere at a carbonization temperature of 400~1000 °C for a carbonization time of 2~24 h.

8. The method according to claim 1, wherein The method of coating the conductive coating in step (2) includes but is not limited to one of spraying, dip coating, and in-situ growth; the conductive coating materials include but are not limited to one or several of carbon nanotubes (CNT), graphene, silver nanoparticles, MXene, nickel, and copper.

9. The method according to claim 1, wherein The electrochemical deposition process described in step (3) is constant voltage deposition, the deposition voltage is -0.9 to -2 V, and the time is 0.05 to 2 h; the deposition solution of the electrochemical deposition process described in step (3) includes, but is not limited to, one or more of ZnSO4 solution, ZnCl2 solution, Zn(NO3)2 solution, Zn(Ac)2 solution, and Zn(OTf)2 solution; one or several of Na2SO4 solution, NaCl solution, and NaNO3 solution are added to the deposition solution of the electrochemical deposition process described in step (3) to adjust the deposition behavior of zinc ions.

10. The composite electrode material with a gradient pore structure prepared by the method according to any one of claims 1 to 9.

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