A lithium negative electrode material with no surface dendrites, a battery and a preparation method

Abstract

The present invention provides a dendrite-free lithium negative electrode material, a battery, and a preparation method. The preparation method comprises: S1, preparing a porous copper foil; S2, performing surface pretreatment on the porous copper foil prepared in S1 to remove zinc deposits on the surface; S3, annealing the porous copper foil; S4, impregnating the annealed porous copper foil with molten metal lithium; cooling to room temperature and removing the porous copper foil to obtain a lithium negative electrode material; S5, punching the lithium-impregnated porous copper foil in S4 into electrode sheets; and forming a battery with lithium iron phosphate, a carbonate electrolyte, a separator, and other materials. The present invention utilizes porous copper foil to anneal in oxygen or air to grow lithium-philic CuO on the surface of the porous copper foil, which can significantly improve the affinity of lithium metal, facilitate the uniform deposition of lithium metal, and significantly inhibit the growth of lithium dendrites. At the same time, the porous structure shortens the transmission distance of lithium ions, increases the specific surface area of ​​the material, and provides nucleation sites for the loading of lithium metal.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a method for preparing a lithium negative electrode material with no dendrites on the surface. Background Art

[0002] High-energy-density batteries play a key role in applications such as electric vehicles, portable electronic devices, and smart grids. They are a major strategic requirement for ensuring energy security, implementing energy conservation and emission reduction, and promoting green and low-carbon development in society as a whole. They play an irreplaceable role in effectively promoting a sustainable energy revolution. Lithium (Li)-ion batteries dominate the battery market due to their low cost, long life, excellent electrochemical reversibility, and low pollution. However, the large-scale commercialization of lithium metal anodes is still plagued by numerous technical challenges. These include: first, lithium dendrite growth leading to energy loss and serious safety issues; second, the repeated formation of solid electrolyte interphase (SEI), which exacerbates electrolyte consumption and shortens battery cycle life; and third, the internal stress and volume expansion generated during cycling cannot be effectively released, which seriously undermines the stability of the electrode structure.

[0003] To overcome these challenges and achieve the commercialization of lithium metal batteries (LMBs), porous current collectors with high surface area and cross-linked structures have attracted widespread attention. Three-dimensional porous current collectors offer the following advantages: First, the through-pore structure can be used to store lithium and alleviate volume expansion during cycling; second, the lithium-philic functionalized framework can induce uniform lithium nucleation and optimize the lithium deposition morphology; third, the high specific surface area can uniformly distribute the electrode charge, and the highly tough framework can eliminate stress and inhibit the formation of lithium dendrites. Patent publication number CN111600036A reports a method for preparing a three-dimensional porous copper oxide-modified copper foil for lithium metal battery current collectors. The method involves mixing sodium hydroxide and ammonium thiosulfate solutions in a certain proportion to form an etching solution. The clean copper foil is then immersed in the etching solution to react, resulting in a copper oxide nanowire-modified copper foil. The copper oxide nanowire layer on the surface of the copper foil enables uniform lithium metal deposition, inhibiting side reactions and dendrite growth. However, this method uses chemical etching reagents, requires a large amount of acid and base intervention, is prone to contamination, and the overall process is cumbersome and time-consuming. Summary of the Invention

[0004] The purpose of the embodiment of the present invention is to provide a method for preparing a lithium negative electrode material with no dendrites on the surface, growing lithium-philic CuO on the surface of a porous copper foil, achieving uniform deposition of lithium metal and inhibiting the growth of lithium dendrites; the method is low-cost and pollution-free.

[0005] The second object of the present invention is to provide a lithium negative electrode material with no surface dendrites.

[0006] A third object of the present invention is to provide a battery.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is a method for preparing a lithium negative electrode material with no surface dendrites, comprising the following steps:

[0008] S1. Preparation of porous copper foil;

[0009] S2. Pre-treating the porous copper foil prepared in S1 to remove the zinc deposit on the surface;

[0010] S3, annealing the porous copper foil;

[0011] S4, immersing the annealed porous copper foil in molten metallic lithium; and taking it out after cooling to room temperature to obtain a lithium negative electrode material.

[0012] Furthermore, the S1 is specifically:

[0013] S11, placing the copper foil in a 6-8% by mass sulfuric acid solution and ultrasonically cleaning it for 30-50 seconds, and then placing the cleaned copper foil in an electric constant temperature drying oven at 70-110° C. and drying it for 35-45 minutes;

[0014] S12, placing the dried copper foil on a pure copper drying rack and vertically placing it in a transparent quartz tube, connecting an inert gas to maintain an inert gas atmosphere in the quartz tube to prevent oxidation of the sample during the heat treatment process, then always maintaining the inert gas flow rate at 100-200 ml / min, and simultaneously starting the metal recovery device at the other end of the quartz tube furnace, heating the quartz tube temperature to 150-450° C. at a heating rate of 10-30° C. / min and keeping it warm for 40-60 min, then raising the temperature to 700-900° C. at a heating rate of 10-30° C. / min and keeping it warm for 1-6 h, and then taking it out to obtain a porous copper foil;

[0015] S13. Stop introducing inert gas and close the metal recovery device; take out after cooling to room temperature with the furnace.

[0016] Furthermore, the inert gas includes any one of nitrogen, argon or a mixture of the two gases.

[0017] Furthermore, the specific process of S2 is: first, the porous copper foil is ultrasonically cleaned in anhydrous ethanol for 5 to 15 seconds to remove the zinc layer on the surface of the sample; then the porous copper foil is placed in a 6 to 8% sulfuric acid solution for cleaning for 5 to 15 seconds; then, the porous copper foil is ultrasonically cleaned in anhydrous ethanol for 5 to 15 seconds to remove the residual sulfuric acid solution; finally, the porous copper foil is dried at a constant temperature of 65 to 75°C in an electric constant temperature drying oven for 30 to 40 minutes and then taken out.

[0018] Furthermore, the specific step of S3 is: placing the dried porous copper foil in an oxygen-containing atmosphere for annealing heat treatment, the annealing temperature is 350-500° C., and the annealing time is 30-40 minutes.

[0019] Furthermore, the specific step of S4 is: immersing the annealed porous copper foil in molten metallic lithium at a temperature of 300-350° C. for 55-65 seconds in an argon atmosphere, and then taking it out after cooling to room temperature to obtain a lithium negative electrode material.

[0020] A lithium negative electrode material with no surface dendrites is prepared by the above method.

[0021] A battery comprises lithium iron phosphate, a carbonate electrolyte, a diaphragm and the above-mentioned lithium negative electrode material with no dendrites on the surface.

[0022] The beneficial effects of the present invention are:

[0023] The present invention utilizes porous copper foil annealed in oxygen or air to grow lithium-philic CuO on the surface of the porous copper foil. This not only significantly improves the affinity of lithium metal, facilitates the uniform deposition of lithium metal, and significantly inhibits the growth of lithium dendrites, but also the porous structure shortens the transmission distance of lithium ions, increases the specific surface area of ​​the material, and provides nucleation sites for lithium metal loading. The porous copper foil can stabilize the material, preventing the collapse of the material structure during the lithium metal insertion and deinsertion process, thereby improving the cycle performance of lithium-ion batteries. The present invention has a simple preparation process, is easy to operate, and has the potential for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 1 is a battery impedance diagram of the porous current collector prepared in Example 1 of the invention and a common current collector;

[0026] Figure 2 1 is a full-cell Coulombic efficiency diagram of the porous current collector prepared in Inventive Example 1 and a common current collector;

[0027] Figure 3 1 is a full battery cycle performance diagram of the porous current collector prepared in Example 1 of the invention and a conventional current collector;

[0028] Figure 4 This is the SEM image of ordinary copper foil after cycling;

[0029] Figure 5 This is an SEM image of the porous copper foil of the present invention after recycling. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] This invention proposes a method for preparing a highly efficient and safe dendrite-free lithium metal negative electrode material. By annealing a porous copper foil in oxygen or air, the surface of the porous copper foil grows lithium-philic CuO, which promotes uniform deposition of lithium metal and significantly improves lithium-ion battery performance. The CuO-distributed porous copper foil, obtained by direct oxidation of the porous copper foil in oxygen or air, promotes uniform deposition of lithium metal and significantly inhibits the growth of lithium dendrites.

[0032] The present invention proposes a method for preparing a high-efficiency and safe lithium metal negative electrode material with no dendrites on the surface, comprising the following steps:

[0033] S1. preparing porous copper foil;

[0034] S11, pickling and drying the commercial copper foil;

[0035] S12, placing the dried copper foil on a pure copper drying rack and vertically placing it in a transparent quartz tube, connecting an inert gas at one end of the quartz tube to maintain an inert gas atmosphere in the quartz tube to prevent oxidation of the sample during the heat treatment; using a metal recovery device at the other end, and then heating and keeping the copper foil warm;

[0036] S13, closing the valve to prevent air from entering, closing the metal recovery device, allowing the sample to cool to room temperature with the furnace, and then taking out the sample. The surface of the sample changes from yellow before physical dealloying to purple-red after treatment; obtaining a porous copper foil;

[0037] S2, pretreatment of porous copper foil;

[0038] The porous copper foil obtained in S1 is ultrasonically cleaned to remove the zinc deposit on the surface; the zinc deposit will cover the porous structure on the surface of the porous copper foil; the porous copper foil is then pickled to remove the zinc deposit on the surface of the sample; finally, the sulfuric acid residue on the surface is removed and the sample is dried.

[0039] S3. Annealing the dried porous copper foil. The annealing time and temperature need to be accurately controlled to avoid the CuO layer formed on the surface of the porous copper foil being too thick or too thin, resulting in unevenness. The thickness of the CuO layer can be guaranteed by regulating the annealing process of the porous copper foil.

[0040] S4, immersing the annealed porous copper foil in molten lithium metal; then cooling it to room temperature and taking it out for later use;

[0041] S5. The porous copper foil impregnated with lithium in S4 is punched into an electrode sheet; and a battery is formed with lithium iron phosphate, carbonate electrolyte, diaphragm and other materials.

[0042] Example 1

[0043] S11. Ultrasonic cleaning of H65 copper foil in 6% sulfuric acid solution for 30 seconds to remove surface stains. The cleaned H65 copper foil is placed in an electric constant temperature drying oven at 70°C for 35 minutes;

[0044] S12. Place the dried H65 copper foil on a pure copper drying rack and vertically place it in a transparent quartz tube. Connect nitrogen to maintain an inert gas atmosphere in the quartz tube to prevent oxidation of the sample during the heat treatment process. Then maintain the nitrogen gas flow rate at 200 ml / min. At the same time, start the metal recovery device at the other end of the quartz tube furnace, heat the quartz tube temperature to 350°C at a heating rate of 30°C / min and keep it warm for 40 minutes, then increase the temperature to 800°C at a heating rate of 20°C / min and keep it warm for 3 hours.

[0045] S13. Close the valve to prevent air from entering, turn off the metal recovery device, let the sample cool to room temperature with the furnace, and then take out the sample. The surface of the sample changes from yellow before physical dealloying to purple-red after treatment.

[0046] S2. First, ultrasonically clean the porous copper foil in anhydrous ethanol for 5 seconds to remove the zinc deposit on the sample surface; then, place the porous copper foil in 8% sulfuric acid solution for 5 seconds to remove the zinc deposit tightly attached to the sample surface; then, ultrasonically clean it in anhydrous ethanol for 5 seconds to remove the residual sulfuric acid solution; finally, dry it in an electric constant temperature drying oven at 65°C for 30 minutes and take it out.

[0047] S3. The dried porous copper foil is placed in an oxygen-containing atmosphere for annealing heat treatment. The annealing temperature is 350° C. and the annealing time is 40 minutes. The annealing time and temperature need to be accurately controlled to avoid the CuO layer generated on the copper foil being too thick or too little and uneven.

[0048] S4. Immerse the annealed porous copper foil in molten lithium at 300° C. for 55 seconds in a glove box filled with argon gas, and then take it out for later use after cooling to room temperature.

[0049] S5. The porous copper foil impregnated with lithium obtained in S4 is punched into electrode sheets with a diameter of 16 mm and combined with lithium iron phosphate, carbonate electrolyte, separator and other materials to form a battery.

[0050] Example 2

[0051] S11. Place 20 μm thick H62 copper foil in 7% sulfuric acid solution and ultrasonically clean it for 40 seconds to remove surface stains. Place the cleaned H62 copper foil in an electric constant temperature drying oven at 90° C. and dry it for 40 minutes.

[0052] S12. Place the dried H62 copper foil on a pure copper drying rack and vertically place it in a transparent quartz tube. Connect nitrogen to maintain an inert gas atmosphere in the quartz tube to prevent oxidation of the sample during the heat treatment process. Then maintain the nitrogen gas flow rate at 150 ml / min. At the same time, start the metal recovery device at the other end of the quartz tube furnace, heat the quartz tube temperature to 150°C at a heating rate of 20°C / min and keep it warm for 50 minutes, then increase the temperature to 700°C at a heating rate of 10°C / min and keep it warm for 6 hours.

[0053] S13. Close the valve to prevent air from entering, turn off the metal recovery device, let the sample cool to room temperature with the furnace, and then take out the sample. The surface of the sample changes from yellow before physical dealloying to purple-red after treatment.

[0054] S2. First, ultrasonically clean the porous copper foil in anhydrous ethanol for 10 seconds to remove the zinc deposit on the sample surface; then, place the porous copper foil in 7% sulfuric acid solution for 10 seconds to remove the zinc deposit tightly attached to the sample surface; then, ultrasonically clean it in anhydrous ethanol for 10 seconds to remove the residual sulfuric acid solution; finally, dry it in an electric constant temperature drying oven at 70°C for 35 minutes and take it out.

[0055] S3. The dried porous copper foil is placed in an oxygen-containing atmosphere for annealing heat treatment. The annealing temperature is 450° C. and the annealing time is 30 minutes. The annealing time and temperature need to be accurately controlled to avoid the CuO layer generated on the copper foil being too thick or too little and uneven.

[0056] S4. Immerse the annealed porous copper foil in molten lithium at 320° C. for 60 seconds in a glove box filled with argon gas, and then take it out for later use after cooling to room temperature.

[0057] S5. The porous copper foil impregnated with lithium obtained in S4 is punched into electrode sheets with a diameter of 16 mm and combined with lithium iron phosphate, carbonate electrolyte, separator and other materials to form a battery.

[0058] Example 3

[0059] S11. Ultrasonic cleaning of H68 copper foil in 8% sulfuric acid solution for 50 seconds was performed to remove surface stains. The cleaned H63 copper foil was placed in an electric constant temperature drying oven at 110°C and dried for 45 minutes.

[0060] S12. Place the dried H68 copper foil on a pure copper drying rack and vertically place it in a transparent quartz tube. Connect a nitrogen and argon mixed gas to maintain an inert gas atmosphere in the quartz tube to prevent oxidation of the sample during the heat treatment process. Then maintain the nitrogen gas flow rate at 100 ml / min. At the same time, start the metal recovery device at the other end of the quartz tube furnace, heat the quartz tube temperature to 450°C at a heating rate of 10°C / min and keep it warm for 60 minutes, then increase the temperature to 900°C at a heating rate of 30°C / min and keep it warm for 1 hour.

[0061] S13. Close the valve to prevent air from entering, turn off the metal recovery device, let the sample cool to room temperature with the furnace, and then take out the sample. The surface of the sample changes from yellow before physical dealloying to purple-red after treatment.

[0062] S2. First, ultrasonically clean the porous copper foil in anhydrous ethanol for 15 seconds to remove the zinc deposit on the sample surface; then, place the porous copper foil in a 6% sulfuric acid solution and clean it for 15 seconds to remove the zinc deposit tightly attached to the sample surface; then, ultrasonically clean it in anhydrous ethanol for 15 seconds to remove the residual sulfuric acid solution; finally, dry it in an electric constant temperature drying oven at 75°C for 40 minutes and take it out.

[0063] S3. The dried porous copper foil is placed in an oxygen-containing atmosphere for annealing heat treatment. The annealing temperature is 500° C. and the annealing time is 30 min. The annealing time and temperature need to be accurately controlled to avoid the CuO layer generated on the copper foil being too thick or too little and uneven.

[0064] S4. Immerse the annealed porous copper foil in molten lithium at 350° C. for 65 seconds in a glove box filled with argon gas, and then take it out for later use after cooling to room temperature.

[0065] S5. The porous copper foil impregnated with lithium obtained in S4 is punched into electrode sheets with a diameter of 16 mm and combined with lithium iron phosphate, carbonate electrolyte, separator and other materials to form a battery.

[0066] Example 4

[0067] The quartz tube temperature in the S12 tube furnace was heated to 350°C at a heating rate of 30°C / min and kept at that temperature for 40 minutes, and then the temperature was raised to 800°C at a heating rate of 20°C / min and kept at that temperature for 2 hours. The rest was the same as in Example 1.

[0068] Example 5

[0069] The quartz tube temperature in the S12 tube furnace was heated to 350°C at a heating rate of 30°C / min and kept at that temperature for 40 minutes, and then the temperature was raised to 800°C at a heating rate of 20°C / min and kept at that temperature for 4 hours. The rest was the same as in Example 1.

[0070] Example 6

[0071] The quartz tube temperature in the tube furnace S12 was heated to 450°C at a heating rate of 30°C / min and kept at that temperature for 40 minutes, and then the temperature was raised to 800°C at a heating rate of 20°C / min and kept at that temperature for 3 hours. The rest was the same as in Example 1.

[0072] Comparative Example 1

[0073] In S2, pickling is not performed to remove the zinc deposit on the surface; the remaining steps are the same as those in Example 1.

[0074] Comparative Example 2

[0075] In S12, the tube furnace is continuously heated at a heating rate of 30°C / min to 700°C and kept at this temperature for 3 hours without performing intermediate graded heating. The rest is the same as in Example 1.

[0076] Comparative Example 3

[0077] In S12, the tube furnace is continuously heated at a heating rate of 30°C / min to 800°C and kept at this temperature for 3 hours without performing intermediate graded heating. The rest is the same as in Example 1.

[0078] Comparative Example 4

[0079] In S12, the tube furnace is continuously heated at a heating rate of 30°C / min to 900°C and kept at this temperature for 3 hours without performing intermediate graded heating. The rest is the same as in Example 1.

[0080] Comparative Example 5

[0081] The S3 process is not performed, and the remaining steps are the same as those in Example 1.

[0082] Comparative Example 6

[0083] The immersion time in S4 is 10 s, and the remaining steps are the same as those in Example 1.

[0084] Comparative Example 7

[0085] The immersion time in S4 is 60 s, and the remaining steps are the same as those in Example 1.

[0086] Average pore size / um Average pore size / um Porosity / % Weight loss rate / % Example 1 8.5 15.6 72.4％ 29.8％ Example 2 7.6 15.3 70.3％ 35.8％ Example 3 7.2 14.8 69.5％ 29.8％ Example 4 6.8 15.4 68.4％ 28.4％ Example 5 5.4 14.8 69.3％ 30.6％ Example 6 4.3 15.1 70.5％ 29.7％ Comparative Example 1 5.6 14.2 57.4％ 28.7％ Comparative Example 2 8.3 4.1 38.9％ 10.3％ Comparative Example 3 7.9 14.7 50.8％ 29.9％ Comparative Example 4 3.5 12.1 20.4％ 31.2％ Comparative Example 5 8.1 15.3 67.1％ 29.7％ Comparative Example 6 8.3 15.1 66.5％ 29.1％ Comparative Example 7 8.2 14.9 68.1％ 29.4％

[0087] The principle of vapor-phase dealloying is to exploit the differences in vapor pressures of various metallic elements in the alloy at high temperatures. Under a high vacuum, the high-vapor-pressure zinc in the copper-zinc alloy is effectively removed, while the lower-vapor-pressure copper is retained, leaving behind a copper skeleton and forming a porous copper. Within a certain temperature range, the higher the temperature, the greater the diffusion rate of copper and zinc. Due to unbalanced diffusion, numerous pores are formed within the material, where vacancies aggregate to form pores, forming Kirkendall pores. Over time, these pores will continue to increase. After a period of treatment, the diffusion rate of the high-vapor-pressure element decreases, and the pores on the surface gradually decrease until they disappear due to the thermal motion of other elements.

[0088] Temperature and holding time cause the pore size, pore band size, and porosity of the copper core alloy to first increase and then decrease. The gas flow rate influences the resulting porous structure after dealloying, making the pore size more uniform and making the material less prone to wrinkling and curling. Kirkendall describes four stages of pore growth: formation of an atomic mismatch zone at the interface; fusion of atomic mismatch zones at the interface to form a void; rapid growth of the void; merging and growth of adjacent voids; and a decrease in the atomic diffusion rate, which gradually leads to the disappearance of the void. Temperature has a dual effect on pore formation. At lower temperatures, the sublimation rate of high-vapor-pressure elements on the material's surface exceeds the diffusion rate, forcing the remaining high-vapor-pressure elements within the material to slowly diffuse to the surface and then sublime. At higher temperatures, the diffusion rate exceeds the surface sublimation rate. After a period of treatment, the diffusion rate of the internal high-vapor-pressure elements decreases, and the surface pores gradually shrink and disappear due to the thermal motion of other elements.

[0089] Experimental example:

[0090] The porous copper current collector prepared in Example 1 and Comparative Example 5 of the present application was combined with molten lithium to form a composite electrode, which was then assembled into a battery for constant current charge and discharge testing. Then, batteries assembled with pure copper as the current collector and pure copper and molten lithium as the current collector were subjected to constant current charge and discharge testing.

[0091] In order to investigate the surface contact between the electrode and the electrolyte, electrochemical impedance spectroscopy (EIS) was used for testing. Figure 1 The EIS diagrams of pure copper, pure copper composite lithium, and porous copper composite lithium electrodes are shown in Figure 2. The concave semicircle represents the charge transfer resistance between the interface and the electrolyte. Figure 1It can be seen that the interface resistance of the porous copper composite lithium electrode is the smallest. This shows that the porous copper composite lithium electrode is not only conducive to the formation of a more stable SEI film, but also can increase the wettability of the electrode and the electrolyte. Compared with the Cu@Li electrode, the porous copper composite lithium electrode has superior charge transfer characteristics. Since there are too few holes and no through holes in Comparative Examples 1, 2, 3, and 4, only a small amount of lithium can be adsorbed on the surface in the step of composite molten lithium. In Comparative Example 5, since no copper oxide film is formed, the porous copper foil not only fails to adsorb lithium metal but is dissolved by the molten lithium metal. Comparative Example 6 cannot complete the adsorption of molten lithium, resulting in uneven current density and uneven SEI film formed, resulting in poor electrochemical performance. The adsorption time of Comparative Example 7 is too long, and the molten lithium easily melts the internal structure of the copper foil, causing the electrode to break.

[0092] To verify the importance of porous morphology on the electrochemical performance of the electrode, we used pure copper, pure copper composite lithium, and the porous copper composite lithium from Example 1 to prepare the electrode, assembled the full battery, and conducted constant current charge and discharge tests. Finally, we used SEM to characterize and compare the differences in their surface morphology. The lithium sheet was used as the positive electrode to prepare a CR2032 battery. The coulombic efficiency curve obtained by testing at room temperature in the voltage range of 0-4V and the current of 0.1C is as follows: Figure 2 .from Figure 2 It can be seen from the figure that under the same other conditions, the coulombic efficiency of pure copper composite lithium and porous copper composite lithium is basically the same. Figure 2 It can be seen that the coulomb efficiency of the full battery with pure copper as the pole piece quickly dropped to about 80% from the beginning and then fluctuated, while the coulomb efficiency of the full battery with pure copper composite lithium and porous copper composite lithium as the pole piece remained at 99.6%. The full battery material with pure copper composite lithium as the pole piece was stably cycled to 238 cycles until the lithium dendrites pierced the diaphragm and caused the battery to short circuit. The half-battery material with porous copper composite lithium as the pole piece was stably cycled to 500 cycles and still operated smoothly. Figure 5 It can be seen that porous copper can significantly improve the stability and cycle efficiency of the negative electrode and reduce polarization. Figure 4 、 Figure 5 Scanning electron microscopy results show that honeycomb-shaped porous copper can suppress the formation of dead lithium and dendrites, producing a more uniform and smooth surface structure. The three-dimensional porous structure of porous copper provides more space for lithium deposition, effectively preventing the formation of lithium dendrites and dead lithium. Lithium deposited on ordinary copper foil has a very uneven surface with disordered growth of lithium dendrites, and the surface deposited lithium breaks up to form agglomerated lithium dendrites that continue to grow upward. However, lithium deposited on honeycomb-shaped porous copper still maintains a uniform and smooth shape and can still maintain its porous structure.

[0093] from Figure 3 It can be seen that the copper current collector of the present invention can significantly improve the stability and cycle efficiency of the battery negative electrode and reduce polarization. Figure 4 、 5 Scanning electron microscopy results show that honeycomb-shaped porous copper can suppress the formation of dead lithium and dendrites, resulting in a more uniform and smooth surface structure. The three-dimensional porous structure of porous copper provides more space for lithium deposition, effectively preventing the formation of lithium dendrites and dead lithium. Lithium deposited on ordinary copper foil has a very uneven surface and exhibits cracking of the deposited lithium. However, lithium deposited on honeycomb-shaped porous copper maintains a uniform and smooth morphology and retains its porous structure.

[0094] Each embodiment in this specification is described in a related manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiment is generally similar to the method embodiment, so the description is relatively simple. For related parts, refer to the description of the method embodiment.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for preparing a lithium negative electrode material with no surface dendrites, characterized in that: The following steps are involved: S1. Preparation of porous copper foil; specifically: S11. Place the copper foil in a 6-8% sulfuric acid solution and ultrasonically clean it for 30-50 seconds. Place the cleaned copper foil in an electric constant temperature drying oven at 70-110°C and dry it for 35-45 minutes. S12, placing the dried copper foil on a pure copper drying rack and vertically placing it in a transparent quartz tube, connecting an inert gas to maintain an inert gas atmosphere in the quartz tube to prevent oxidation of the sample during the heat treatment process, then always maintaining the inert gas flow rate at 100-200 ml / min, and simultaneously starting the metal recovery device at the other end of the quartz tube furnace, heating the quartz tube temperature to 150-450° C. at a heating rate of 10-30° C. / min and keeping the temperature for 40-60 min, then raising the temperature to 700-900° C. at a heating rate of 10-30° C. / min and keeping the temperature for 1-6 h, and then taking out to obtain a porous copper foil; S13, stop introducing inert gas and close the metal recovery device; take out after cooling to room temperature with the furnace; S2. Pre-treating the porous copper foil prepared in S1 to remove the zinc deposit on the surface; S3, annealing the porous copper foil; specifically: The dried porous copper foil is placed in an oxygen-containing atmosphere for annealing heat treatment at a temperature of 450-500°C for 30-40 minutes. S4. Immerse the annealed porous copper foil in molten metallic lithium at a temperature of 300-350° C. in an argon atmosphere for 65 seconds, and then take it out after cooling to room temperature to obtain a lithium negative electrode material.

2. The method for preparing a surface dendrite-free lithium negative electrode material according to claim 1; characterized in that: The inert gas includes any one of nitrogen, argon or a mixture of the two gases.

3. The method for preparing a surface dendrite-free lithium negative electrode material according to claim 1; characterized in that: The specific process of S2 is as follows: first, the porous copper foil is ultrasonically cleaned in anhydrous ethanol for 5 to 15 seconds to remove the zinc layer on the surface of the sample; then, the porous copper foil is placed in a 6 to 8% sulfuric acid solution for cleaning for 5 to 15 seconds; then, the porous copper foil is ultrasonically cleaned in anhydrous ethanol for 5 to 15 seconds to remove the residual sulfuric acid solution; finally, the porous copper foil is dried at a constant temperature of 65 to 75°C in an electric constant temperature drying oven for 30 to 40 minutes.

4. A lithium negative electrode material with no surface dendrites, characterized in that: Prepared by any one of the methods described in claims 1 to 3.

5. A battery, characterized in that: The invention comprises lithium iron phosphate, a carbonate electrolyte, a diaphragm and a lithium negative electrode material with no surface dendrites as claimed in claim 4.

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