Composite current collector and lithium metal negative plate and battery using same

Abstract

The invention provides a composite current collector as well as a lithium metal negative plate and a battery applying the composite current collector. The composite current collector comprises a base material, and a copper layer and an anti-oxidation layer which are sequentially arranged on at least one surface of the base material, wherein the anti-oxidation layer contains at least one of a porphyrin compound and a porphyrin polymer. When the composite current collector provided by the invention is applied to a lithium metal negative plate and a battery, in the charging process of the battery, the anti-oxidation layer can provide lithium deposition nucleation sites and can promote uniform deposition of lithium ions on the lithium metal negative plate, so that formation of lithium dendrites is effectively reduced, growth of the lithium dendrites is inhibited, the safety performance of the battery is improved, and the service life of the battery is prolonged. The copper layer is compounded on the surface of the base material, the composite copper foil is used as the current collector, the weight of the negative electrode plate can be further reduced, and the service life of the negative electrode plate is prolonged, so that the service life of the negative electrode plate is prolonged, and the service life of the negative electrode plate is prolonged. And the energy density of the lithium metal battery is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a composite current collector and lithium metal anode sheets and batteries using it. Background Technology

[0002] To address range anxiety in electric vehicles, the energy density and rate performance of lithium-ion batteries have been key research areas in the market. Energy density directly affects driving range, while rate performance plays a decisive role in charging time. Lithium metal anodes, as the ultimate means to improve the energy density of lithium-ion batteries, have received widespread attention and research. However, lithium metal anodes are prone to forming lithium dendrites during lithium-ion battery cycling, which can puncture the separator, causing short circuits and safety accidents, ultimately leading to a decline in the safety performance of lithium-ion batteries.

[0003] The formation of lithium dendrites is due to two main factors: uneven thermal / chemical distribution within the battery during cycling, and defects and impurities inherent in lithium metal itself. Lithium metal foil prepared by traditional rolling methods is prone to internal micro-defects during the rolling process, and the rolling process itself easily introduces oil contamination, which is an important inducing factor for the formation of lithium dendrites.

[0004] Extensive research has been conducted in the industry to prevent lithium dendrite formation, ranging from electrolyte chemical composition control and the use of flame-retardant electrolytes to artificial SEI films and 3D lithium metal anodes. Furthermore, to reduce lithium dendrite formation, the industry also employs methods such as surface modification of finished copper foil or lithium metal, including depositing 3D nickel foam, coating with lithium-affinity modified graphite layers, and using polymer compounds. While these methods can inhibit lithium dendrite formation, they are cumbersome to manufacture and increase the thickness and weight of the current collector. Summary of the Invention

[0005] In order to improve the cycle performance and energy density of existing lithium-ion batteries using lithium metal anodes, and to solve the problem of lithium dendrite formation during cycling leading to a decrease in the safety performance of lithium-ion batteries, this invention provides a composite current collector and a lithium metal anode sheet and battery using the same.

[0006] According to a first aspect of the present invention, a composite current collector is provided, the composite current collector comprising a substrate and a copper layer and an antioxidant layer sequentially disposed on at least one surface of the substrate, the antioxidant layer containing at least one of a porphyrin compound and a porphyrin polymer.

[0007] When the composite current collector provided by this invention is applied to lithium metal anode sheets and batteries, on the one hand, due to the highly conjugated structure of the porphyrin compounds and / or porphyrin polymers in the antioxidant layer, the conjugated π bonds contained in the porphyrin compounds and / or porphyrin polymers provide a large number of lithium-affinity nucleation sites. During battery charging, the antioxidant layer can provide lithium deposition nucleation sites, which can promote the uniform deposition of lithium ions on the lithium metal anode sheet, effectively reduce the formation of lithium dendrites and inhibit the growth of lithium dendrites, thereby improving the safety performance of the battery. On the other hand, the antioxidant layer can isolate air, protect the copper layer from oxidation, reduce copper loss, and reduce the risk of increased battery internal resistance due to copper layer oxidation. In addition, this invention composites a copper layer on the surface of the substrate, using composite copper foil as the current collector, which can further reduce the weight of the anode sheet and improve the energy density of the lithium metal battery.

[0008] Traditional composite current collectors are made by laminating an antioxidant layer onto the surface of copper foil. The antioxidant layer on the copper foil surface is mainly divided into two types: organic antioxidant layer and inorganic antioxidant layer. Inorganic antioxidant layers often use chromium, molybdenum, and silicate-based materials, while organic antioxidant layers often use silane coupling agents. In batteries using the above-mentioned traditional composite current collectors, lithium ions will randomly deposit on the surface of such traditional composite current collectors during charging and discharging. Due to the small number of deposition points, lithium dendrites will grow rapidly at the deposition points, causing the deposited lithium layer to thicken rapidly. In addition, the continuous growth of lithium dendrites can easily penetrate the positive and negative electrodes, causing a short circuit in the battery.

[0009] Compared to traditional composite current collectors, the composite current collector provided by this invention uses porphyrin compounds and / or porphyrin polymers in the antioxidant layer. The addition of porphyrin groups in the antioxidant layer significantly increases the number of lithium-ion deposition sites, resulting in more uniform and denser lithium-ion deposition on the surface of the composite current collector provided by this invention. The lithium dendrites are smaller and denser, which helps to reduce the thickness of the deposited lithium layer and reduces the risk of battery short circuit caused by the continuous growth of lithium dendrites, thereby improving the safety performance of the battery.

[0010] Preferably, the porphyrin compound includes at least one of tetraphenylporphyrin, tetracarboxyphenylporphyrin, and tetraaminophenylporphyrin.

[0011] Preferably, the porphyrin polymer includes at least one of porphyrin-modified benzoic acid polymers, porphyrin-modified polylactic acid-polyethylene glycol block copolymers, and porphyrin-modified polyaryl ether nitrile polymers.

[0012] Preferably, the porphyrin compound includes tetrakis(4-hydroxy-3-sulfonate sodium phenyl)porphyrin.

[0013] Preferably, the porphyrin polymer includes at least one of the following: a polymer generated by copolymerization of tetra(4-hydroxyphenyl)porphyrin and hexachlorocyclotriphosphazene, a porphyrin-modified polylactic acid-polyethylene glycol (PLA-PEG) block copolymer, and a porphyrin-modified polyethylene glycol-polycaprolactone (PEG-PCL) block copolymer.

[0014] Preferably, the thickness of the copper layer is 0.5 to 2 μm.

[0015] By controlling the thickness of the copper layer in the composite current collector within the aforementioned range, the copper layer can possess good current-carrying capacity, reducing the internal resistance of the battery using this composite current collector. If the thickness of the copper layer in the composite current collector is too thin, the current-carrying capacity of the copper layer will be poor, increasing the battery's internal resistance; if the thickness of the copper layer in the composite current collector is too thick, applying this composite current collector to the battery will occupy too much battery space and increase the manufacturing cost of the composite current collector.

[0016] Preferably, the thickness of the antioxidant layer is 5–100 nm.

[0017] By controlling the thickness of the antioxidant layer in the composite current collector within the aforementioned range to maintain its optimal antioxidant function, applying this composite current collector to a battery can improve its resistance to electrolyte corrosion, thereby ensuring the bonding strength between the substrate, copper layer, and antioxidant layer in the composite current collector and extending battery life. If the thickness of the antioxidant layer in the composite current collector is too thin, the antioxidant function will be poor, and the electrolyte will easily corrode the antioxidant layer, leading to a decrease in the bonding strength between the substrate, copper layer, and antioxidant layer in the composite current collector and shortening battery life. If the thickness of the antioxidant layer in the composite current collector is too thick, the excessively thick antioxidant layer will occupy too much internal space in the battery and may increase the internal resistance of the composite current collector.

[0018] Preferably, the thickness of the substrate is 3 to 10 μm.

[0019] Controlling the thickness of the substrate in the composite current collector within the aforementioned range ensures good tensile and heat resistance properties, reducing the risk of band breakage during the fabrication process of the composite current collector and electrode. If the substrate thickness is too thin, the tensile and heat resistance properties of the composite current collector will easily decrease, increasing the risk of band breakage during the fabrication process of the composite current collector and electrode, and posing a higher safety risk during the use of batteries employing this composite current collector. If the substrate thickness is too thick, the resistance of the composite current collector will increase, and an excessively thick substrate will occupy too much space within the battery.

[0020] Preferably, the substrate is selected from at least one of polyethylene terephthalate (PET) film, polypropylene (PP) film, and polyimide (PI) film.

[0021] According to a second aspect of the present invention, a lithium metal anode sheet is provided, the lithium metal anode sheet comprising the aforementioned composite current collector.

[0022] Using the composite current collector provided by this invention as the current collector for lithium metal anode sheets, and applying the lithium metal anode sheet to batteries, can reduce the formation of lithium dendrites during battery charging and discharging, reduce the weight of lithium metal anode sheets, and improve the energy density of batteries using lithium metal anode sheets.

[0023] Preferably, the lithium metal anode sheet further includes a lithium metal layer disposed on at least one surface of the composite current collector.

[0024] A lithium metal anode is obtained by laminating a lithium metal layer on at least one surface of a composite current collector. When this lithium metal anode is applied to a battery, the lithium metal layer can compensate for the lithium loss during the SEI film formation process during the first charge and discharge of the battery, and can also serve as a lithium source in the battery using this lithium metal anode to support lithium loss during battery cycling.

[0025] Preferably, the thickness of the lithium metal layer is 3–20 μm.

[0026] According to a third aspect of the present invention, a method for preparing the above-mentioned lithium metal anode sheet is provided, comprising the following steps:

[0027] S1. Deposit a copper layer on at least one surface of a substrate, and thicken the copper layer to a thickness of 0.5–2 μm to obtain a semi-finished product;

[0028] S2. An antioxidant solution is prepared using porphyrin compounds and / or porphyrin polymers;

[0029] S3. Immerse the semi-finished product in an antioxidant solution to deposit an antioxidant layer on both surfaces of the semi-finished product, thus obtaining a composite current collector;

[0030] S4. A lithium metal layer is deposited on at least one surface of the composite current collector to obtain a lithium metal anode sheet.

[0031] The lithium metal anode sheet provided by this solution obtains an antioxidant layer with lithiophilic sites through a one-step deposition process. The lithiophilic sites are combined with the antioxidant on the copper surface, making the preparation method simple and reducing the number of steps. Without adding any steps, the deposited antioxidant layer can not only ensure that the copper layer is not oxidized, but also induce uniform lithium ion nucleation and inhibit lithium dendrite growth. At the same time, it reduces the thickness of the lithium metal anode sheet and improves the battery energy density.

[0032] Preferably, in S1, the copper layer is deposited on at least one surface of the substrate by vacuum evaporation or magnetron sputtering.

[0033] Preferably, the specific operation of S1 is as follows: a nanoscale copper layer is deposited on at least one surface of the substrate by magnetron sputtering or vapor deposition, and then the copper layer is thickened to 0.5-2 μm by water plating.

[0034] Depositing a copper layer on at least one surface of a substrate using physical deposition methods (vacuum evaporation or magnetron sputtering) to make the substrate conductive can improve the bonding strength between the copper layer and the substrate.

[0035] Preferably, in S1, the copper layer is thickened by a water plating process.

[0036] Physical deposition has low production efficiency and takes a long time to deposit a copper layer at the micron level. First, a nano-scale copper layer is deposited on at least one surface of the substrate using physical deposition, and then a water plating process is used to thicken the copper layer, which can ensure the efficiency of the coating and copper layer thickening.

[0037] Preferably, in S2, the concentration of the antioxidant solution is 10–25 g / L.

[0038] Preferably, in step S3, the soaking time of the semi-finished product in the antioxidant solution is 8 to 10 seconds.

[0039] Preferably, in S4, the lithium metal layer is deposited on the surface of the antioxidant layer by vacuum evaporation or magnetron sputtering.

[0040] The lithium metal layer is deposited on the surface of the composite current collector by vacuum evaporation. The lithium deposition thickness can be controlled to obtain a thin lithium layer, which reduces internal defects and surface oil and other impurities caused by traditional lithium metal foil production processes. It also reduces internal and surface defects of lithium metal and improves the uniformity of lithium deposition on the lithium metal anode surface during battery charging and discharging, further reducing the probability of lithium dendrite formation.

[0041] According to a third aspect of the present invention, a battery is provided, the battery comprising the lithium metal anode sheet described above or the lithium metal anode sheet prepared by the method described above.

[0042] Applying the composite current collector and lithium metal anode sheet provided by this invention to batteries reduces copper and lithium losses, increases battery energy density, and effectively suppresses lithium dendrite growth during battery charging and discharging, thereby improving the safety performance of lithium metal batteries. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of the lithium metal anode sheet provided by the present invention.

[0044] The attached figures are labeled as follows: 1 composite current collector, 2 substrate, 3 copper layer, 4 anti-oxidation layer, and 5 lithium metal layer. Detailed Implementation

[0045] The technical features of the technical solution provided by the present invention will be further clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0046] Example 1

[0047] A lithium metal anode sheet, the structure of which is as follows: Figure 1 As shown, it includes a composite current collector 1 and lithium metal layers 5 disposed on two surfaces of the composite current collector. The composite current collector 1 includes a substrate 2 and a copper layer 3 and an anti-oxidation layer 4 disposed sequentially on the two surfaces of the substrate 2.

[0048] The lithium metal anode sheet provided in this embodiment is prepared through the following steps:

[0049] S1. Using a polyethylene terephthalate (PET) film with a thickness of 4.5 μm as substrate 2, a nanoscale copper layer 3 is deposited on both sides of substrate 2 by physical deposition (magnetron sputtering or vacuum evaporation), and the thickness of copper layer 3 is increased to 1 μm by water plating process to obtain a semi-finished product.

[0050] S2. An antioxidant solution with a concentration of 10 g / L was prepared by using tetrakis(4-hydroxy-3-sulfonate sodium phenyl)porphyrin and the solvent N-methyl-2-pyrrolidone.

[0051] S3. Pass the above semi-finished product through an antioxidant solution, remove it after 9 seconds in the solution, and dry it so that an antioxidant layer 4 with a thickness of 50 nm is deposited on each of the two surfaces of the semi-finished product to obtain a composite current collector 1.

[0052] S4. A 5μm thick lithium metal layer 5 is deposited on both surfaces of the composite current collector 1 by vacuum evaporation to obtain a lithium metal anode sheet.

[0053] Example 2

[0054] A lithium metal anode sheet, the structure of which is as follows: Figure 1 As shown, it includes a composite current collector 1 and lithium metal layers 5 disposed on two surfaces of the composite current collector, wherein the composite current collector 1 includes a substrate 2 and a copper layer 3 and an anti-oxidation layer 4 disposed sequentially on the two surfaces of the substrate 2.

[0055] The lithium metal anode sheet provided in this embodiment is prepared through the following steps:

[0056] S1. Using a polyethylene terephthalate (PET) film with a thickness of 3 μm as substrate 2, a nanoscale copper layer 3 is deposited on both sides of substrate 2 by physical deposition (magnetron sputtering or vacuum evaporation), and the thickness of copper layer 3 is increased to 0.2 μm by water plating process to obtain a semi-finished product.

[0057] S2. An antioxidant solution with a concentration of 20 g / L was prepared by using tetrakis(4-hydroxy-3-sulfonate sodium phenyl)porphyrin and the solvent N-methyl-2-pyrrolidone.

[0058] S3. Pass the above semi-finished product through an antioxidant solution, remove it after 8 seconds in the solution, and dry it so that an antioxidant layer 4 with a thickness of 5nm is deposited on each of the two surfaces of the semi-finished product to obtain a composite current collector 1.

[0059] S4. A 3μm thick lithium metal layer 5 is deposited on both surfaces of the composite current collector 1 by vacuum evaporation to obtain a lithium metal anode sheet.

[0060] Example 3

[0061] A lithium metal anode sheet, the structure of which is as follows: Figure 1 As shown, it includes a composite current collector 1 and lithium metal layers 5 disposed on two surfaces of the composite current collector, wherein the composite current collector 1 includes a substrate 2 and a copper layer 3 and an anti-oxidation layer 4 disposed sequentially on the two surfaces of the substrate 2.

[0062] The lithium metal anode sheet provided in this embodiment is prepared through the following steps:

[0063] S1. Using a 10μm thick polyethylene terephthalate (PET) film as substrate 2, a nanoscale copper layer 3 is deposited on both sides of substrate 2 by physical deposition (magnetron sputtering or vacuum evaporation), and the thickness of copper layer 3 is increased to 5μm by water plating process to obtain a semi-finished product.

[0064] S2. An antioxidant solution with a concentration of 25 g / L was prepared by using tetrakis(4-hydroxy-3-sulfonate sodium phenyl)porphyrin and the solvent N-methyl-2-pyrrolidone.

[0065] S3. Pass the above semi-finished product through an antioxidant solution, remove it after 10 seconds in the solution, and dry it so that an antioxidant layer 4 with a thickness of 100nm is deposited on each of the two surfaces of the semi-finished product to obtain a composite current collector 1.

[0066] S4. A lithium metal layer 5 with a thickness of 20 μm is deposited on both surfaces of the composite current collector 1 by vacuum evaporation to obtain a lithium metal anode sheet.

[0067] Example 4

[0068] This embodiment provides a lithium metal anode sheet. Compared with Embodiment 1, the difference in structure is that the preparation step S2 of the lithium metal anode sheet is different, as detailed below:

[0069] S2. An antioxidant solution with a concentration of 25 g / L was prepared by using a water-soluble porphyrinized polymer with a three-dimensional network structure and the solvent N-methyl-2-pyrrolidone. The porphyrinized polymer was generated by copolymerization of tetrakis(4-hydroxyphenyl)porphyrin and hexachlorocyclotriphosphazene and was purchased from Xi'an Qiyue Biotechnology Co., Ltd., with product brand number Q-0336163.

[0070] Apart from the differences mentioned above, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0071] Example 5

[0072] This embodiment provides a lithium metal anode sheet. Compared with Embodiment 1, the difference in structure is that the preparation step S2 of the lithium metal anode sheet is different, as detailed below:

[0073] S2. An antioxidant solution with a concentration of 20 g / L was prepared by using porphyrin-modified PEG-PCL (polyethylene glycol-polycaprolactone) block copolymer and solvent N-methyl-2-pyrrolidone. The porphyrin-modified PEG-PCL (polyethylene glycol-polycaprolactone) block copolymer was purchased from Xi'an Qiyue Biotechnology Co., Ltd., product brand number Q-0339477.

[0074] Apart from the differences mentioned above, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0075] Comparative Example 1

[0076] This comparative example provides a lithium metal anode sheet. Compared with Example 1, the difference in composition is that in step S2 of the lithium metal anode sheet preparation, the traditional chromium-containing antioxidant OY-8 type copper antioxidant (purchased from Wenzhou Aoyang Metal Surface Treatment Co., Ltd.) is used instead of tetrakis(4-hydroxy-3-sulfonate sodium phenyl)porphyrin. Apart from the above difference, the materials, formulation ratios, and preparation operations used in this comparative example are strictly consistent with those in Example 1.

[0077] Comparative Example 2

[0078] This comparative example provides a lithium metal anode sheet. Compared with Example 1, the difference lies in the structure of the lithium metal anode sheet, as detailed below:

[0079] The lithium metal anode sheet provided in this comparative example includes a composite current collector and lithium metal layers disposed on two surfaces of the composite current collector. The composite current collector includes a pure copper foil with a thickness of 6 μm and an antioxidant layer disposed on two surfaces of the pure copper foil. The antioxidant layer contains a conventional organic antioxidant silane coupling agent (CAS No. 211519-85-6) and does not contain porphyrin compounds and / or porphyrin polymers.

[0080] Apart from the differences mentioned above, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0081] Comparative Example 3

[0082] This comparative example provides a lithium metal anode sheet. Compared with Example 1, the difference in composition is that in step S2 of the lithium metal anode sheet preparation, a PLA-PEG (polylactic acid-polyethylene glycol) block copolymer with a number average molecular weight of 1000-3000 is used instead of tetrakis(4-hydroxy-3-sulfonate phenyl)porphyrin. Apart from the above difference, the materials, formulation ratios, and preparation operations used in this comparative example are strictly consistent with those in Example 1.

[0083] The thickness of the “substrate,” “copper layer,” “antioxidant layer,” and “lithium metal layer” in the aforementioned lithium metal anode sheet can be observed and measured by cutting the lithium metal anode sheet using argon ion cutting technology (ion polishing CP) and then using scanning electron microscopy (SEM).

[0084] Test case

[0085] 1. Participants

[0086] This test example uses the composite current collector and lithium metal anode sheet prepared in Examples 1-5 and Comparative Examples 1-3 as test objects, and will conduct relevant performance tests.

[0087] 2. Test Content

[0088] (1) Antioxidant effect

[0089] The composite current collectors prepared in Examples 1-5 and Comparative Examples 1-3 were placed in an oven at 150°C and baked for 30 minutes. The oxidation effect on the surface of the copper layer in the composite current collector was observed.

[0090] (2) Expansion rate of lithium metal anode sheet

[0091] The lithium metal anode sheets prepared in Examples 1-5 and Comparative Examples 1-3 were used to prepare coin cells with lithium iron phosphate cathode sheets. The coin cells were tested at room temperature (25°C). The coin cells were charged at a constant current and constant voltage of 1C to 3.65V with a cutoff current of 0.05C. Then, the coin cells were discharged at a constant current of 1C to 2.0V. This constituted one charge-discharge cycle. After 100 charge-discharge cycles of the coin cells in the above manner, the lithium metal anode sheets were removed from the batteries, and the thickness of the lithium metal anode sheets before and after the cycles was tested. The expansion rate of the lithium metal anode sheets after 100 charge-discharge cycles was calculated according to the following formula: Expansion rate of lithium metal anode sheets (%) = (Thickness of lithium metal anode sheets after 100 charge-discharge cycles - Thickness of lithium metal anode sheets before cycles) / Thickness of lithium metal anode sheets before cycles × 100%.

[0092] (3) Average Coulomb efficiency

[0093] The lithium metal anode sheets prepared in Examples 1-5 and Comparative Examples 1-3 were used to prepare coin cells with lithium iron phosphate cathode sheets. The coin cells were charged at a constant current and constant voltage of 1C to 3.65V at room temperature (25°C) and allowed to stand for 10 minutes. Then, the coin cells were discharged at a constant current of 1C to 2.0V and allowed to stand for 10 minutes. The charge and discharge were recorded respectively. The average coulombic efficiency of the coin cells was calculated according to the following formula: Average coulombic efficiency (%) = Discharged charge / Charged charge × 100%.

[0094] (4) Cyclic performance

[0095] The lithium metal anode sheets prepared in Examples 1-5 and Comparative Examples 1-3 were used to prepare coin cells with lithium iron phosphate cathode sheets. The coin cells were tested at room temperature (25°C). They were charged at a constant current and constant voltage of 1C to 3.65V with a cutoff current of 0.05C. Then, they were discharged at a constant current of 1C to 2.0V. This constituted one charge-discharge cycle. The coin cells were charged and discharged for 100 cycles in the same manner. The discharge capacity of the coin cells before and after the cycles was tested. The capacity retention rate of the coin cells after 100 cycles was calculated using the following formula: Capacity retention rate of the coin cells after 100 cycles (%) = (Discharge capacity of the 100th cycle / First discharge capacity) × 100%.

[0096] The coin cell used in the tests of the expansion rate, average coulombic efficiency, and cycle performance of the lithium metal anode sheet was prepared according to the following steps:

[0097] ① Preparation of positive electrode sheet

[0098] Lithium iron phosphate positive electrode active material, conductive carbon black (SP), and binder polyvinylidene fluoride (PVDF) were mixed uniformly at a mass ratio of 94:3:3 and dispersed in the solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector coated with carbon aluminum foil to form a positive electrode active coating. The coating was dried at 85°C under vacuum for 24 hours, and then cold-pressed and slit to obtain a surface capacity of 4mAh / 100cm³. 2 The positive electrode plate.

[0099] ② Preparation of negative electrode sheet

[0100] The lithium metal anode sheets prepared in Examples 1-5 and Comparative Examples 1-3 were used as anode sheets.

[0101] ③ Preparation of the diaphragm

[0102] A PP membrane with a thickness of 15μm and a ceramic layer coated on one side was used as the separator.

[0103] ④ Preparation of electrolyte

[0104] A solvent was prepared by mixing ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1. LiPF6 was then dissolved in the solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0105] ⑤ Assembly of button-type symmetrical batteries

[0106] The positive electrode, separator, and negative electrode are stacked in sequence and injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a coin cell is obtained.

[0107] 3. Experimental Results

[0108] Table 1. Performance test results of composite current collector, lithium metal anode sheet and battery

[0109]

[0110] The performance test results of the composite current collectors, lithium metal anode sheets, and batteries using them prepared in Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0111] The composite current collector prepared in Comparative Example 1 includes a pure copper foil and an antioxidant layer disposed on two surfaces of the pure copper foil. The antioxidant layer contains a conventional chromium-containing antioxidant, OY-8 type copper antioxidant. The composite current collectors prepared in Examples 1-5 include a substrate and a copper layer and an antioxidant layer disposed sequentially on two surfaces of the substrate. The antioxidant layer contains a lithiophilic porphyrin compound and / or a porphyrin polymer. After baking the composite current collectors provided in Comparative Example 1 and Examples 1-5 in an oven at 150°C for 30 minutes, no obvious color change was observed on the surface of the composite current collectors. The above results indicate that the antioxidant effect of the antioxidant layer containing porphyrin compound and / or porphyrin polymer is comparable to that of the antioxidant layer containing a conventional chromium-containing antioxidant, OY-8 type copper antioxidant.

[0112] Compared to Comparative Examples 1-3, the lithium metal anode sheets provided in Examples 1-5 include a composite current collector and lithium metal layers disposed on two surfaces of the composite current collector. The composite current collector includes a substrate and a copper layer and an antioxidant layer disposed sequentially on two surfaces of the substrate. The antioxidant layer contains a lithiophilic porphyrin compound and / or a porphyrin polymer. When the lithium metal anode sheets provided in Examples 1-5 are applied to batteries, the test results show that the average coulombic efficiency and capacity retention rate after 100 cycles of the batteries using the lithium metal anode sheets provided in Examples 1-5 are higher than those of Comparative Examples 1-3, while the expansion rate of the lithium metal anode sheets is lower than that of Comparative Examples 1-3. The above results demonstrate that the oxide layer in the lithium metal anode sheets provided in Examples 1-5, due to the introduction of porphyrin compounds and / or porphyrin polymers with highly conjugated structures, provides a large number of lithium-affinity nucleation sites through the conjugated π bonds contained in the porphyrin compounds and / or porphyrin polymers. During battery charging, the antioxidant layer can provide lithium deposition nucleation sites, which can promote the uniform deposition of lithium ions on the lithium metal anode sheet, effectively reduce the formation of lithium dendrites and inhibit the growth of lithium dendrites, thereby improving the cycle performance and average coulombic efficiency of the battery, while reducing the expansion rate of the lithium metal anode sheet.

[0113] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A composite current collector, characterized in that: It includes a substrate and a copper layer and an antioxidant layer sequentially disposed on at least one surface of the substrate, wherein the antioxidant layer contains at least one of a porphyrin compound and a porphyrin polymer.

2. The composite current collector as described in claim 1, characterized in that: The porphyrin compounds include at least one of tetraphenylporphyrin, tetracarboxyphenylporphyrin, and tetraaminophenylporphyrin; The porphyrin polymers include at least one of porphyrin-modified benzoic acid polymers, porphyrin-modified polylactic acid-polyethylene glycol block copolymers, and porphyrin-modified polyarylene ether nitrile polymers.

3. The composite current collector as described in claim 2, characterized in that: The porphyrin compounds include tetrakis(4-hydroxy-3-sulfonate phenyl)porphyrin, and / or the porphyrin polymers include at least one of the following: a polymer generated by copolymerization of tetrakis(4-hydroxyphenyl)porphyrin and hexachlorocyclotriphosphazene, a porphyrin-modified polylactic acid-polyethylene glycol block copolymer, and a porphyrin-modified polyethylene glycol-polycaprolactone block copolymer.

4. The composite current collector as described in claim 1, characterized in that: The thickness of the copper layer is 0.5–2 μm, and / or the thickness of the antioxidant layer is 5–100 nm, and / or the thickness of the substrate is 3–10 μm.

5. The composite current collector as described in claim 1, characterized in that: The substrate is selected from at least one of polyethylene terephthalate film, polypropylene film, and polyimide film.

6. A lithium metal anode sheet, characterized in that: The lithium metal anode sheet includes the composite current collector as described in any one of claims 1 to 5 and a lithium metal layer disposed on at least one surface of the composite current collector.

7. The lithium metal anode sheet as described in claim 6, characterized in that: The thickness of the lithium metal layer is 3–20 μm.

8. A method for preparing a lithium metal anode sheet, characterized in that, Includes the following steps: S1. Deposit a copper layer on at least one surface of a substrate, and thicken the copper layer to a thickness of 0.5 to 2 μm to obtain a semi-finished product; S2. An antioxidant solution is prepared using porphyrin compounds and / or porphyrin polymers; S3. Immerse the semi-finished product in the antioxidant solution to deposit the antioxidant layer on both surfaces of the semi-finished product, thereby obtaining a composite current collector; S4. A lithium metal layer is deposited on at least one surface of the composite current collector to obtain the lithium metal anode sheet.

9. The method for preparing the lithium metal anode sheet as described in claim 8, characterized in that, The specific operation of S1 is as follows: a nanoscale copper layer is deposited on at least one surface of the substrate by magnetron sputtering or vapor deposition, and then the copper layer is thickened to 0.5-2 μm by water plating.

10. A battery, characterized in that: The battery includes a lithium metal anode sheet as described in any one of claims 6 to 7, or a lithium metal anode sheet prepared using the method described in any one of claims 8 to 9.

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