3D printing copper current collector-metal lithium composite negative electrode and preparation method thereof

Abstract

The invention belongs to the technical field of lithium secondary batteries, and particularly relates to a 3D printing copper current collector-metal lithium composite negative electrode and a preparation method thereof, zinc oxide and metal lithium are deposited in a 3D printing copper skeleton, and compared with a lithium sheet negative electrode, the metal lithium negative electrode of a three-dimensional structure has a large specific surface area and can effectively reduce the current density in the charging and discharging process. Meanwhile, the internal porous structure can well limit lithium in the internal space, so that the volume expansion of the lithium negative electrode in the charging and discharging process is reduced, and the growth of dendritic crystals is effectively inhibited.

Description

Technical Field

[0001] This invention belongs to the field of lithium secondary battery technology, specifically relating to a 3D-printed copper current collector-lithium metal composite anode and its preparation method. Background Technology

[0002] The successful commercialization of lithium-ion batteries has led to the rapid development of mobile electronic devices and electric vehicles. Currently, most commercially available lithium-ion rechargeable batteries use graphite anode materials, which are low-cost, have a long cycle life, and can be mass-produced. However, the theoretical capacity of graphite anode materials is relatively low, only 372 kJ / m³. mAh / g Such low battery capacity makes improving the energy density of lithium-ion batteries an urgent priority.

[0003] Lithium metal has a very high theoretical capacity (3860). mAh / g ), low density (0.534) g / cm 3) and a low voltage window (-3.04) V vs Lithium metal has attracted researchers' attention due to its use as a standard hydrogen electrode. When used as the negative electrode material in lithium secondary batteries, it can significantly improve the energy density of the battery and is known as the "holy grail" of energy storage.

[0004] However, lithium metal as a negative electrode material will encounter many problems during cycling, mainly: (1) Lithium metal is very reactive, and a layer will be formed on the surface of lithium metal immediately upon contact with the electrolyte. SEI (Solid electrolyte) membranes, during charge-discharge cycles, can lead to uneven lithium deposition, resulting in… SEI (1) The rupture and regeneration of the lithium metal leads to the continuous consumption of electrolyte, resulting in a decrease in battery efficiency; (2) During the charge and discharge cycle, dendrites will be generated on the surface of lithium metal. The continuous growth of dendrites will pierce the separator and come into contact with the positive electrode, causing a short circuit inside the battery, or even fire and explosion, which poses a great safety hazard; (3) During the cycle, the breakage of dendrites causes "dead lithium", which further reduces the coulombic efficiency and cycle life of the battery.

[0005] Therefore, based on the above technical problems, it is necessary to design a new 3D printed copper current collector-lithium metal composite anode and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a 3D-printed copper current collector-lithium metal composite anode and its preparation method.

[0007] To address the aforementioned technical problems, this invention provides a 3D-printed copper current collector-lithium metal composite anode, comprising: 3D printed copper current collector, with zinc oxide and lithium metal deposited in the 3D printed copper current collector skeleton.

[0008] The 3D printed copper current collector is prepared by metal 3D printing, and the raw material is copper powder.

[0009] The copper powder, after grinding, has a particle size range of 20~75. μm .

[0010] The printing ink preparation involves adding ground copper powder to deionized water and stirring; the amount of copper powder added is 2-30g. vol. %.

[0011] The preparation of the printing ink includes adding a nonionic surfactant to a suspension. The surfactant includes, but is not limited to, alkylolamides, alkylamine oxides, N-alkylpyrrolidones, Pluronic@F-127, etc. The amount of surfactant added is 3-30g. wt .%.

[0012] The printing method is uniaxial extrusion, with an injection cylinder pressure of 20-45 psi and a printing speed of 10-25 mm / s. -1 .

[0013] The lithium metal content is 8-99.99%. wt .%.

[0014] After slicing the 3D-printed copper current collector, it was sequentially immersed in acetone, ethanol, and deionized water for ultrasonic cleaning.

[0015] The ultrasonically cleaned 3D-printed copper current collector is placed in a vacuum drying oven for drying.

[0016] The dried 3D printed copper current collector was placed in a zinc nitrate solution, and after the addition of ammonia solution, zinc hydroxide was deposited on the surface of the 3D printed copper current collector after a hydrothermal reaction.

[0017] The 3D printed copper current collector with zinc hydroxide deposited on it is placed in a vacuum drying oven and dried at a preset temperature for a preset time to obtain a 3D printed copper current collector with zinc oxide deposited on its surface.

[0018] After mixing 3D-printed copper current collectors with deposited zinc oxide with molten liquid lithium metal, the mixture is removed after a second preset time and naturally cooled to obtain a composite negative electrode with 3D-printed copper current collectors and lithium metal.

[0019] The concentration of the zinc nitrate solution is 0.02~0.05%. mol / L .

[0020] The temperature of the hydrothermal reaction is 75~110 ℃.

[0021] The hydrothermal reaction time is 4~10 minutes. h .

[0022] The zinc nitrate solution and ammonia solution account for 50-90% of the volume of the vessel used in the hydrothermal reaction.

[0023] The method for preparing the molten liquid lithium metal includes: In a confined space under a protective atmosphere, heating yields molten liquid lithium metal.

[0024] The protective atmosphere is Ar gas.

[0025] The temperature used to obtain molten liquid lithium metal after heating is 200-400℃.

[0026] The method of mixing a 3D-printed copper current collector with deposited zinc oxide with molten liquid lithium metal, removing it after a second preset time, and allowing it to cool naturally to obtain a 3D-printed copper current collector-lithium metal composite negative electrode includes: The 3D-printed copper current collector with zinc oxide deposited is brought into contact with molten liquid lithium metal, or immersed in molten liquid lithium metal, until the molten liquid lithium metal is uniformly attached to the 3D-printed copper current collector with zinc oxide deposited. After being removed and allowed to cool naturally, a 3D-printed copper current collector-lithium metal composite negative electrode is obtained.

[0027] The beneficial effects of this invention are that zinc oxide and metallic lithium are deposited in the 3D-printed copper current collector framework. Compared with lithium sheet anodes, the three-dimensional metallic lithium anode has a large specific surface area, which can effectively reduce the current density during charging and discharging. At the same time, the porous internal structure can effectively confine lithium within the internal space, reduce the volume expansion of the lithium anode during charging and discharging, and effectively suppress dendrite growth.

[0028] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a flowchart of a method for preparing a 3D-printed copper current collector-lithium metal composite anode according to the present invention; Figure 2 This is a scanning electron microscope image of a 3D-printed copper current collector-lithium metal composite negative electrode prepared according to the present invention; Figure 3 Voltage-time curve of the symmetrical cell prepared in Example 2 of the present invention; Figure 4 The surface of a pure lithium anode after 100 constant current cycles SEM picture; Figure 5 The surface of the 3D-printed copper current collector-lithium metal composite negative electrode after 100 constant current cycles. SEM picture; Figure 6 Voltage-time curves of the symmetrical battery prepared in Example 3 of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1 like Figures 1 to 6 As shown, this embodiment 1 provides a 3D-printed copper current collector-lithium metal composite anode, comprising: a 3D-printed copper current collector framework, wherein zinc oxide and lithium metal are deposited in the 3D-printed copper current collector framework; the three-dimensional lithium metal anode has a large specific surface area compared to a lithium sheet anode, which can effectively reduce the current density during charging and discharging. At the same time, the internal porous structure can effectively confine lithium in the internal space, reduce the volume expansion of the lithium anode during charging and discharging, and effectively suppress dendrite growth.

[0034] In this embodiment, the lithium metal content is 8-99.99%. wt .%.

[0035] In this embodiment, the thickness of the 3D-printed copper current collector is 0.1~40 mm. mm The 3D-printed copper current collector skeleton has 13 to 1300 holes. PPI The pore size of the 3D-printed copper current collector skeleton is 0.1~10 mm. mm .

[0036] This embodiment also provides a method for preparing a 3D-printed copper current collector-lithium metal composite negative electrode, including: grinding and stirring copper powder, adding surfactant, 3D printing copper current collector, and slicing the 3D-printed copper current collector (forming a 3D-printed copper current collector skeleton) and then immersing it in acetone, ethanol and deionized water in sequence for ultrasonic cleaning, with the ultrasonic cleaning time not less than 30 minutes. min The ultrasonically cleaned 3D-printed copper current collector was placed in a vacuum drying oven for drying. The dried 3D-printed copper current collector was placed in a zinc nitrate solution, and after the addition of ammonia solution, zinc hydroxide was deposited on the surface of the 3D-printed copper current collector after a hydrothermal reaction. The 3D-printed copper current collector with zinc hydroxide deposited was placed in a vacuum drying oven and dried at a preset temperature for a preset time to obtain a 3D-printed copper current collector with zinc oxide deposited on its surface. The 3D-printed copper current collector with zinc oxide deposited was mixed with molten liquid lithium metal, and after a second preset time, it was taken out and naturally cooled to obtain a 3D-printed copper current collector-lithium metal composite negative electrode.

[0037] In this embodiment, the concentration of the zinc nitrate solution is 0.02~0.05%. mol / L The hydrothermal reaction temperature is 75~110℃; the hydrothermal reaction time is 4~10 minutes. h The zinc nitrate solution and ammonia solution account for 50-90% of the volume of the vessel in the hydrothermal reaction.

[0038] In this embodiment, the 3D-printed copper current collector deposited with zinc hydroxide is placed in a vacuum drying oven and dried at a preset temperature for a preset time. The drying temperature is 120~200℃, and the drying time is 1.5~3 minutes. h .

[0039] In this embodiment, the method for preparing the molten liquid lithium metal includes: heating in a closed space under a protective atmosphere to obtain molten liquid lithium metal.

[0040] In this embodiment, the protective atmosphere is Ar The temperature used to obtain molten liquid lithium metal after heating is 200-400℃.

[0041] In this embodiment, the method of mixing the 3D-printed copper current collector with deposited zinc oxide with molten liquid lithium metal, removing it after a second preset time, and naturally cooling it to obtain a 3D-printed copper current collector-lithium metal composite negative electrode includes: contacting the 3D-printed copper current collector with deposited zinc oxide with molten liquid lithium metal, or immersing it in molten liquid lithium metal, until the molten liquid lithium metal is uniformly attached to the 3D-printed copper current collector with deposited zinc oxide, and then removing it and naturally cooling it to obtain a 3D-printed copper current collector-lithium metal composite negative electrode.

[0042] This embodiment also provides a lithium metal secondary battery, which uses the above-mentioned 3D printed copper current collector-lithium metal composite negative electrode.

[0043] Example 2 This Example 2 is a specific example of the 3D-printed copper current collector-lithium metal composite anode in Example 1: After slicing the 3D-printed copper current collector, it is sequentially immersed in acetone, ethanol, and deionized water, and ultrasonically cleaned for 10 minutes each. min The ultrasonically cleaned copper foam was placed in a vacuum drying oven for drying; the dried 3D-printed copper current collector was then placed in a 0.03% concentration... mol / L In a zinc nitrate solution, 7 drops were then slowly added. mL After applying concentrated ammonia, a hydrothermal reaction is performed at 100°C to deposit zinc hydroxide on the copper surface of the 3D-printed copper current collector. The 3D-printed copper current collector with deposited zinc hydroxide is then rinsed with plenty of deionized water and finally dried in a vacuum drying oven for 1.5 days. h The drying temperature is 150℃, and after cooling, it is taken out as foam copper with zinc oxide nanolayer deposited on it.

[0044] from Figure 2 a (Surface of foamed copper with deposited zinc oxide nanolayer) SEM The image shows SEM The photo shows a dense layer of zinc oxide deposited on the surface of the 3D-printed copper current collector.

[0045] Solid lithium metal was melted at 300°C, and then the 3D-printed copper current collector prepared above was placed into the liquid lithium metal to form a three-dimensional 3D-printed copper current collector-lithium metal composite electrode (lithium metal content is 50%). wt . %).

[0046] from Figure 2 b (Surface of 3D printed copper current collector-lithium metal composite anode) SEM The image shows SEMThe photo shows that lithium metal has been filled into the 3D printed copper current collector, forming a three-dimensional 3D printed copper current collector-lithium metal composite electrode.

[0047] Assembly of lithium metal secondary batteries: The prepared 3D-printed copper current collector-lithium metal composite negative electrode is assembled according to the positive electrode shell, electrode sheet, and electrolyte (30g) is added. μL ), diaphragm, (add electrolyte 30) μL The electrode sheet, gasket, spring sheet, and negative electrode shell are assembled in sequence to form a symmetrical battery. The battery model is button cell 2032.

[0048] Electrochemical performance testing of symmetric cells: (1) mAh / cm 2 The capacity is 3 mA / cm 2 The current density is used for charge-discharge cycles.

[0049] like Figure 3 As shown, the negative potential represents the deposition potential, and the positive potential represents the detachment potential. Figure 3 It can be seen that the present invention prepares Li - Cu @ ZnO || Li - Cu @ ZnO The symmetrical battery exhibits significantly better cycle performance than conventional batteries. Li || Li The performance can be seen from the graph. Li - Cu @ ZnO || Li - Cu @ ZnO In symmetrical cells, the deposition and removal potentials of lithium are both relatively high. Li || Li The battery life should be low, and the curve should be smooth. Li || Li The erratic curves in the battery indicate internal instability and significant changes in the electrodes. From... Figure 4 It can be seen that ordinary Li || Li Dendrites have appeared on the electrode surface of the battery, and Li - Cu @ ZnO || Li - Cu @ ZnO The electrode surfaces of the battery are very smooth (e.g.) Figure 5 (As shown).

[0050] Example 3 Example 3 is another specific example of the 3D-printed copper current collector-lithium metal composite negative electrode in Example 1: After slicing the 3D-printed copper current collector, the copper slices were sequentially immersed in acetone, ethanol, and deionized water, and ultrasonically cleaned for 10 minutes each. min The ultrasonically cleaned 3D-printed copper current collector was placed in a vacuum drying oven for drying; the dried 3D-printed copper current collector was then placed in a 0.03% concentration... mol / L In a zinc nitrate solution, 7 drops were then slowly added. mL After applying concentrated ammonia, a hydrothermal reaction is performed at 100°C to deposit zinc hydroxide on the copper surface of the 3D-printed copper current collector. The copper current collector with zinc hydroxide deposition is then rinsed with copious amounts of deionized water and finally dried in a vacuum drying oven for 1.5 hours. h The drying temperature is 150℃, and after cooling, it is taken out as 3D printed copper current collector with zinc oxide nanolayer deposited on it.

[0051] Solid lithium metal was melted at 300°C, and then the 3D-printed copper current collector prepared above was placed into the liquid lithium metal to form a three-dimensional 3D-printed copper current collector-lithium metal composite electrode (lithium metal content is 80%). wt . %).

[0052] The assembly of the lithium metal secondary battery is the same as in Example 2: Electrochemical performance testing of symmetric cells: (1) mAh / cm 2 The capacity is 5 mA / cm 2 The current density is used for charge-discharge cycles. Figure 6 It can be seen that the present invention prepares Li - Cu @ ZnO || Li - Cu @ ZnO The symmetrical battery exhibits significantly better cycle performance than conventional batteries. Li || Li The performance can be seen from the graph. Li - Cu @ ZnO || Li - Cu @ ZnO In symmetrical cells, the deposition and removal potentials of lithium are both relatively high. Li || Li The battery life should be low, and the curve should be smooth. Li || Li Disordered curves in the battery indicate internal instability and significant changes in the electrodes.

[0053] In summary, this invention deposits zinc oxide and metallic lithium in a 3D-printed copper current collector framework. Compared to lithium sheet anodes, the three-dimensional metallic lithium anode has a much larger specific surface area, effectively reducing the current density during charging and discharging. Simultaneously, the porous internal structure effectively confines lithium within the internal space, reducing the volume expansion of the lithium anode during charging and discharging and effectively suppressing dendrite growth.

[0054] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0055] The purity of all raw materials used in this invention is not particularly limited; however, analytical grade or conventional purity levels suitable for lithium metal secondary batteries are preferred. Based on the above-described preferred embodiments of this invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A 3D-printed copper current collector-lithium metal composite anode, characterized in that, include: 3D printed copper current collector, with zinc oxide and lithium metal deposited in the 3D printed copper current collector skeleton.

2. The 3D-printed copper current collector-lithium metal composite anode as described in claim 1, characterized in that, The 3D printed copper current collector is prepared by metal 3D printing, and the raw material is copper powder.

3. The 3D-printed copper current collector-lithium metal composite negative electrode as described in claim 2, characterized in that, The copper powder, after grinding, has a particle size range of 20~75. μm .

4. The 3D-printed copper current collector-lithium metal composite negative electrode as described in claim 2, characterized in that, The printing ink preparation involves adding ground copper powder to deionized water and stirring; the amount of copper powder added is 2-30g. vol. %.

5. The 3D-printed copper current collector-lithium metal composite negative electrode as described in claim 2, characterized in that, The preparation of the printing ink includes adding a nonionic surfactant to a suspension. The surfactant includes, but is not limited to, alkylolamides, alkylamine oxides, N-alkylpyrrolidones, Pluronic@F-127, etc. The amount of surfactant added is 3-30g. wt .%.

6. The 3D-printed copper current collector-lithium metal composite anode as described in claim 2, characterized in that, The printing method is uniaxial extrusion, with an injection cylinder pressure of 20-45 psi and a printing speed of 10-25 mm / s. -1 .

7. The 3D-printed copper current collector-lithium metal composite negative electrode as described in claim 1, characterized in that, The lithium metal content is 8-99.99%. wt .%.

8. A method for preparing a 3D-printed copper current collector-lithium metal composite negative electrode as described in any one of claims 1-7, characterized in that, include: After the 3D printed copper current collector was sliced, it was sequentially immersed in acetone, ethanol and deionized water for ultrasonic cleaning. The ultrasonically cleaned 3D-printed copper current collector is placed in a vacuum drying oven to dry; The dried 3D printed copper current collector was placed in a zinc nitrate solution, and after the addition of ammonia solution, zinc hydroxide was deposited on the surface of the 3D printed copper current collector after a hydrothermal reaction. The 3D printed copper current collector with zinc hydroxide deposited on it was placed in a vacuum drying oven and dried at a preset temperature for a preset time to obtain a 3D printed copper current collector with zinc oxide deposited on its surface. After mixing 3D-printed copper current collectors with deposited zinc oxide with molten liquid lithium metal, the mixture is removed after a second preset time and naturally cooled to obtain a composite negative electrode with 3D-printed copper current collectors and lithium metal.

9. The preparation method according to claim 8, characterized in that, The concentration of the zinc nitrate solution is 0.02~0.05%. mol / L ; The temperature of the hydrothermal reaction is 75~110 ℃; The hydrothermal reaction time is 4~10 minutes. h ; The zinc nitrate solution and ammonia solution account for 50-90% of the volume of the vessel used in the hydrothermal reaction.

10. The preparation method according to claim 8, characterized in that, The method for preparing molten liquid lithium metal includes: heating in a closed space under a protective atmosphere to obtain molten liquid lithium metal.

11. The preparation method according to claim 10, characterized in that, The protective atmosphere is Ar gas; The temperature used to obtain molten liquid lithium metal after heating is 200-400℃.

12. The preparation method according to claim 8, characterized in that, The method of mixing a 3D-printed copper current collector with deposited zinc oxide with molten liquid lithium metal, removing it after a second preset time, and allowing it to cool naturally to obtain a 3D-printed copper current collector-lithium metal composite negative electrode includes: The 3D-printed copper current collector with zinc oxide deposited is brought into contact with molten liquid lithium metal, or immersed in molten liquid lithium metal, until the molten liquid lithium metal is uniformly attached to the 3D-printed copper current collector with zinc oxide deposited. After being removed and allowed to cool naturally, a 3D-printed copper current collector-lithium metal composite negative electrode is obtained.

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