A super-thin lithium copper foil with high elongation, a preparation method and application thereof

Abstract

The application relates to the technical field of copper foil preparation, in particular to a high-elongation ultra-thin lithium battery copper foil and a preparation method and application thereof, the preparation method comprises the following steps: S1: dissolving copper raw materials, sulfuric acid and deionized water to obtain a copper sulfate solution, then mixing the copper sulfate solution with additives after multi-stage filtration to obtain an electrolyte; S2: heat exchanging the electrolyte through a heat exchanger, then introducing the electrolyte into an electrolytic cell, adjusting the temperature and current density of the electrolyte, and performing electrolytic foil growth; S3: passivating and heat treating the copper foil obtained through the electrolytic foil growth, then performing edge cutting and winding, so that the ultra-thin lithium battery copper foil is obtained; wherein the additive in the step S1 is a mixture of organic sulfides and oxygen-containing polymers. The lithium battery copper foil prepared by the application has good tensile strength and high elongation.

Description

Technical Field

[0001] This invention relates to the field of copper foil preparation technology, specifically to an ultra-thin lithium-ion battery copper foil with high elongation, its preparation method, and its application. Background Technology

[0002] Copper foil is one of the key materials in the production of lithium-ion batteries. The quality of copper foil directly affects the manufacturing process and overall performance of lithium-ion batteries. The tensile strength, elongation, and gloss of electrolytic copper foil directly impact the quality performance of lithium-ion battery anode manufacturing processes and battery stability. Copper foil must possess sufficient tensile strength and elongation; otherwise, during the flattening process of the anode sheet coated with graphite and other active materials, the contact performance between the copper foil and the active materials deteriorates, resulting in poor dimensional stability and flatness of the anode. This also easily leads to electrode breakage, affecting the yield of the anode, battery capacity, internal resistance, and cycle life. Lithium-ion batteries may experience heat generation during production. This heat can cause the anode to expand and break. The high tensile strength of copper foil can restrain the high-heat expansion of the anode, reducing the possibility of breakage. Therefore, improving the tensile strength of copper foil can prevent the anode from easily breaking due to thermal expansion.

[0003] Invention patent CN118621389A discloses a method for preparing high tensile strength lithium-ion battery copper foil. The specific steps of this method are as follows: Step 1: Copper raw material, sulfuric acid, and deionized water are added to a copper dissolving tank in a specific process ratio. Simultaneously, high-temperature air is blown in using a blower to dissolve the copper raw material, preparing a copper sulfate solution. After multi-stage filtration, the copper sulfate solution is mixed with an additive solution to obtain an electrolyte. The electrolyte is then heated by a heat exchanger and introduced into an electrolytic cell for electroplating. Step 2: The electrolyte is electrolyzed to produce copper foil at a specific temperature and current density. Step 3: After electrolysis, the copper foil is passivated with a chromic anhydride passivation solution, and then trimmed and wound to obtain the finished lithium-ion battery copper foil. This preparation method uses a specific additive process ratio to refine the grains, increase crystallinity and density, and can produce copper foil with ultra-high tensile strength. However, the additives used in this invention to improve tensile strength, especially sulfur-containing organic compounds and their proportions, may easily lead to grain boundary brittleness, thus affecting or even sacrificing the elongation of the lithium-ion battery copper foil. Therefore, in applications where higher anti-wrinkle and bending resistance of copper foil is required, there is an urgent need for an ultra-thin lithium-ion battery copper foil with high elongation. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of this invention is to obtain an ultrathin lithium battery copper foil with good tensile strength and high elongation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for preparing ultrathin lithium-ion battery copper foil with high elongation, the method comprising the following steps:

[0007] S1: Dissolve copper raw materials, sulfuric acid, and deionized water to obtain copper sulfate solution. Then, after multi-stage filtration, the copper sulfate solution is mixed with additives to obtain electrolyte.

[0008] S2: The electrolyte is heated by passing it through a heat exchanger and then introduced into an electrolytic cell. The temperature and current density of the electrolyte are adjusted to electrolyze the foil.

[0009] S3: Passivate and heat-treat the copper foil obtained by electrolytic green foil, and then cut and roll it up to obtain the ultra-thin lithium battery copper foil;

[0010] In step S1, the additive is a mixture of organic sulfides and oxygen-containing polymers.

[0011] In some embodiments of the present invention, the concentration of copper ions in the electrolyte in step S1 is 70-100 g / L, the concentration of sulfuric acid is 85-120 g / L, and the concentration of chloride ions is 25-30 mg / L.

[0012] In some embodiments of the present invention, the temperature of the electrolyte in step S2 is 50-60°C.

[0013] In some embodiments of the present invention, the current density in step S2 is 40–60 A / dm. 2 .

[0014] In some embodiments of the present invention, the flow rate of the electrolytic cell in step S2 is 40-50 m³ / h. 3 / h.

[0015] This invention controls the electrolyte temperature at 50–60°C and adjusts the current density to 40–60 A / dm³. 2 The electrolyte flow rate is maintained at 40-50 m³ / h. 3 / h, the performance of lithium-ion battery copper foil was synergistically optimized from the preparation conditions. This temperature range can promote crystal growth and improve Cu 2 The diffusion rate of + makes the copper foil thickness uniform and the elongation greatly improved; while the specific current density ensures deposition efficiency and avoids dendrite formation, thus ensuring tensile strength; the specific electrolyte flow rate effectively reduces concentration polarization, further reduces internal stress, and makes the grain size distribution more uniform, thus achieving a comprehensive balance between tensile strength and high elongation.

[0016] In some embodiments of the present invention, the organosulfur compound is at least one of sodium 3-mercaptopropanesulfonate, sodium dimethylformamidopropanesulfonate, and sodium polydisulfidedipropanesulfonate.

[0017] In some embodiments of the present invention, the concentration of the organosulfur compound is 6 to 15 mg / L.

[0018] This invention optimizes the type and concentration of organic sulfur compounds. Their unique sulfur-containing functional groups regulate the deposition behavior of copper, inhibiting excessively rapid local grain growth, making the copper grains finer and more uniform, effectively improving the tensile strength of the copper foil. The presence of sulfonic acid groups further improves the thickness uniformity of the copper foil, achieving high performance in the tensile strength of lithium battery copper foil.

[0019] In some embodiments of the present invention, the preparation steps of the oxygen-containing polymer are as follows:

[0020] (1) 5-methoxy-2-mercaptobenzimidazole, allyl chloride and catalyst were added to DMF and reacted at 80-85℃ for 5-7 h. After purification, the intermediate product was obtained.

[0021] (2) Mix isopentenyl alcohol polyoxyethylene ether and deionized water, heat to 80-85℃, add initiator, and simultaneously add a mixed solution of acrylic acid, intermediate product of step (1), sodium methallyl sulfonate, chain transfer agent and deionized water at a uniform rate. After the addition is complete, continue to keep the reaction at the temperature for 3-4 hours, and then add alkali solution to adjust to neutrality to obtain oxygen-containing polymer.

[0022] In some embodiments of the present invention, the mass ratio of 5-methoxy-2-mercaptobenzimidazole and allyl chloride in step (1) is 1:(0.6-0.8).

[0023] In some embodiments of the present invention, the mass ratio of acrylic acid in step (2), the intermediate product in step (1), sodium methallyl sulfonate and isopentenyl alcohol polyoxyethylene ether is 1:(1-2):(1-2):(10-20).

[0024] In some embodiments of the present invention, the molecular weight of the isopentenyl alcohol polyoxyethylene ether in step (2) is 2000 to 4000.

[0025] In some embodiments of the present invention, the concentration of the oxygen-containing polymer is 3 to 12 mg / L.

[0026] This invention also obtains an intermediate product through the reaction of 5-methoxy-2-mercaptobenzimidazole and allyl chloride, and then uses polyoxyethylene ether with a specific branched structure as a solvation segment, preferably acrylic acid and sodium methallyl sulfonate monomers, to participate in polymerization to prepare an oxygen-containing polymer. When this polymer is mixed with a specific organic sulfur compound as an additive in the electrolyte, it effectively compensates for the shortcomings in the performance balance of the organic sulfur compound. On the one hand, it may form a flexible buffer through the adsorption of polyether segments, thereby inhibiting the lattice stress concentration during the electrolytic foil formation process; on the other hand, its active groups further coordinate with copper ions, thereby regulating the electrodeposition rate and promoting uniform grain growth. The synergistic effect of the two greatly improves the ductility of lithium battery copper foil.

[0027] The applicant also found that the lithium-ion battery copper foil has good tensile strength, which is speculated to be due to the presence of benzimidazole rings synergistically strengthening the adhesion of the copper foil surface through π-π stacking and sulfur-copper bonding, filling the active sites not covered by organic sulfur compounds, reducing defects in the lithium-ion battery copper foil, and achieving a balance between tensile strength and high elongation.

[0028] A second aspect of the present invention also provides an ultrathin lithium-ion battery copper foil with high elongation obtained by the above preparation method, wherein the ultrathin lithium-ion battery copper foil has the following characteristics: tensile strength ≥490.1MPa and elongation ≥6.9%.

[0029] A third aspect of the present invention also provides the application of ultra-thin lithium-ion battery copper foil with high elongation in the negative electrode current collector of lithium-ion batteries.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The lithium battery copper foil prepared by the method of the present invention has good tensile strength and high elongation.

[0032] (2) This invention controls the electrolyte temperature at 50-60℃ and adjusts the current density to 40-60A / dm². 2 The electrolyte flow rate is maintained at 40-50 m³ / h. 3 / h, by synergistically optimizing the preparation conditions, the performance of lithium battery copper foil was improved, and a balance between tensile strength and high elongation was achieved.

[0033] (3) By selecting the type and concentration of organic sulfur compounds, the present invention can regulate the deposition behavior of copper, inhibit the excessively rapid growth of grains in a local area, make the copper grains more refined and uniform, and effectively improve the tensile strength of copper foil.

[0034] (4) The present invention also obtains an intermediate product by reacting 5-methoxy-2-mercaptobenzimidazole and allyl chloride, and then uses polyoxyethylene ether with a specific branched structure as a solvation segment, preferably acrylic acid and sodium methallyl sulfonate monomers to participate in polymerization to prepare an oxygen-containing polymer. When it is mixed with a specific organic sulfur compound as an additive and added to the electrolyte, a balance between tensile strength and high elongation is achieved. Detailed Implementation

[0035] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the invention, but rather as a more detailed description of certain aspects, features, and embodiments of the invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Other combinations and various modifications within the scope of the invention can be made without departing from the spirit or scope of the invention.

[0036] Unless otherwise specified, the compounds and related reagents used in the following specific embodiments are commercially available.

[0037] Unless otherwise specified, the post-processing steps such as "purification", "coarse filtration", "fine filtration", "passivation", "heat treatment", "edge trimming", and "winding" used in the following specific embodiments are routine operations for those skilled in the art, and can be selected according to actual operation.

[0038] Preparation Example 1

[0039] The preparation steps of oxygen-containing polymers are as follows:

[0040] (1) Add 5g of 5-methoxy-2-mercaptobenzimidazole, 3.5g of allyl chloride and 2g of pyridine to 50mL of DMF and react at 82℃ for 6h. After purification, the intermediate product is obtained.

[0041] (2) Mix 15g of isopentenyl alcohol polyoxyethylene ether (molecular weight 3000) and 35mL of deionized water, heat to 82℃, add 0.1g of ammonium persulfate, and simultaneously add a mixed solution of 1g acrylic acid, 1.5g of the intermediate product of step (1), 1.5g of sodium methyl allyl sulfonate, 0.012g of dodecanethiol and 15mL of deionized water at a uniform rate. After the addition is complete, add 0.05g of ammonium persulfate, continue to keep warm for 3.5h, and then add 30wt% sodium hydroxide solution to adjust the pH to 7 to obtain the oxygen-containing polymer.

[0042] Preparation Example 2

[0043] The specific preparation steps of the oxygen-containing polymer are the same as those in Preparation Example 1, except that the amount of allyl chloride added in step (1) is 4.5g.

[0044] Preparation Example 3

[0045] The specific preparation steps of the oxygen-containing polymer are the same as those in Preparation Example 1, except that the amount of intermediate product added in step (2) is 2.5g.

[0046] Preparation Example 4

[0047] The specific preparation steps of the oxygen-containing polymer are the same as those in Preparation Example 1, except that the amount of sodium methallyl sulfonate added in step (2) is 2.5g.

[0048] Preparation Example 5

[0049] The specific preparation steps of the oxygen-containing polymer are the same as those in Preparation Example 1, except that the amount of isopentenyl alcohol polyoxyethylene ether (molecular weight 3000) added in step (2) is 22g.

[0050] Example 1

[0051] A method for preparing ultrathin lithium-ion battery copper foil with high elongation, the method comprising the following steps:

[0052] S1: Dissolve copper raw material, sulfuric acid, and deionized water to obtain copper sulfate solution. Then, after coarse filtration and fine filtration, the copper sulfate solution is mixed with sodium 3-mercaptopropanesulfonate and oxygen-containing polymer to obtain electrolyte. The concentration of copper ions in the electrolyte is 85 g / L, the concentration of sulfuric acid is 100 g / L, the concentration of chloride ions is 27 mg / L, the concentration of sodium 3-mercaptopropanesulfonate is 11 mg / L, and the concentration of oxygen-containing polymer is 8 mg / L.

[0053] S2: The electrolyte is heated through a heat exchanger and then introduced into the electrolytic cell (the flow rate of the electrolytic cell is 45 m³ / s). 3 / h), adjust the electrolyte temperature to 55℃ and the current density to 50A / dm³. 2 Electrolytic foil production is carried out;

[0054] S3: Passivate and heat-treat the copper foil obtained by electrolytic green foil, and then cut and roll it up to obtain the ultra-thin lithium battery copper foil;

[0055] The oxygen-containing polymer used in this embodiment was obtained from Preparation Example 1.

[0056] Example 2

[0057] S1: Dissolve copper raw material, sulfuric acid, and deionized water to obtain copper sulfate solution. Then, after coarse filtration and fine filtration, the copper sulfate solution is mixed with sodium 3-mercaptopropanesulfonate and oxygen-containing polymer to obtain electrolyte. The electrolyte has a copper ion concentration of 70 g / L, a sulfuric acid concentration of 85 g / L, a chloride ion concentration of 25 mg / L, a sodium 3-mercaptopropanesulfonate concentration of 6 mg / L, and an oxygen-containing polymer concentration of 3 mg / L.

[0058] S2: The electrolyte is heated through a heat exchanger and then introduced into the electrolytic cell (the flow rate of the electrolytic cell is 40 m³ / s). 3 / h), adjust the electrolyte temperature to 50℃, and the current density to 40A / dm³. 2 Electrolytic foil production is carried out;

[0059] S3: Passivate and heat-treat the copper foil obtained by electrolytic green foil, and then cut and roll it up to obtain the ultra-thin lithium battery copper foil;

[0060] The oxygen-containing polymer used in this embodiment was obtained from Preparation Example 1.

[0061] Example 3

[0062] S1: Copper raw material, sulfuric acid, and deionized water are dissolved to obtain copper sulfate solution. The copper sulfate solution is then coarsely filtered and finely filtered before being mixed with sodium 3-mercaptopropanesulfonate and an oxygen-containing polymer to obtain an electrolyte. The electrolyte contains copper ion concentration of 100 g / L, sulfuric acid concentration of 120 g / L, chloride ion concentration of 30 mg / L, sodium 3-mercaptopropanesulfonate concentration of 15 mg / L, and oxygen-containing polymer concentration of 12 mg / L.

[0063] S2: The electrolyte is heated through a heat exchanger and then introduced into the electrolytic cell (the flow rate of the electrolytic cell is 50 m³ / s). 3 / h), adjust the electrolyte temperature to 60℃ and the current density to 60A / dm³. 2 Electrolytic foil production is carried out;

[0064] S3: Passivate and heat-treat the copper foil obtained by electrolytic green foil, and then cut and roll it up to obtain the ultra-thin lithium battery copper foil;

[0065] The oxygen-containing polymer used in this embodiment was obtained from Preparation Example 1.

[0066] Example 4

[0067] A method for preparing ultrathin lithium-ion battery copper foil with high elongation is described. The specific implementation method is the same as in Example 1, except that the oxygen-containing polymer used in this example is obtained from Preparation Example 2.

[0068] Example 5

[0069] A method for preparing ultrathin lithium-ion battery copper foil with high elongation is described. The specific implementation method is the same as in Example 1, except that the oxygen-containing polymer used in this example is obtained from Preparation Example 3.

[0070] Example 6

[0071] A method for preparing ultrathin lithium-ion battery copper foil with high elongation is described. The specific implementation method is the same as in Example 1, except that the oxygen-containing polymer used in this example is obtained from Preparation Example 4.

[0072] Example 7

[0073] A method for preparing ultrathin lithium-ion battery copper foil with high elongation is described. The specific implementation method is the same as in Example 1, except that the oxygen-containing polymer used in this example is obtained from Preparation Example 5.

[0074] Example 8

[0075] A method for preparing ultrathin lithium-ion battery copper foil with high elongation is described. The specific implementation method is the same as in Example 1, except that the oxygen-containing polymer used in this example is PEG6000.

[0076] Example 9

[0077] A method for preparing ultrathin lithium-ion battery copper foil with high elongation is described, with the specific implementation method being the same as in Example 1, except that the concentration of the oxygen-containing polymer used in this example is 13 mg / L.

[0078] Performance testing

[0079] The tensile strength and elongation of the ultrathin lithium-ion battery copper foils obtained in the above embodiments were tested in accordance with Section 2.4.18 of the IPC TM 650 Test Method Manual of the Electronic Circuits and Interconnects Industry Association of the United States. At the same time, the thickness of the ultrathin lithium-ion battery copper foils obtained in Examples 1-3 was measured.

[0080] The test results are shown in Tables 1 and 2:

[0081] Table 1

[0082] Group Example 1 Example 2 Example 3 Thickness (μm) 5 4.5 6

[0083] Table 2

[0084] Group Tensile strength (MPa) Elongation (%) Example 1 503.2 7.2 Example 2 502.9 6.9 Example 3 490.1 7.9 Example 4 489.3 6.0 Example 5 485.5 5.7 Example 6 478.2 6.9 Example 7 481.8 6.5 Example 8 402.4 4.2 Example 9 467.7 6.2

[0085] As can be seen from the data in Tables 1 and 2, the thickness of the ultra-thin lithium battery copper foil in Examples 1-3 of the present invention can reach 4.5-6 μm, and it has good tensile strength and high elongation.

[0086] A comparison of Examples 4, 5, 6, and 7 with Example 1 shows that when the amounts of allyl chloride, intermediate product, sodium methyl allyl sulfonate, and isopentenyl polyoxyethylene ether added during the preparation of the oxygen-containing polymer are changed, Example 4 may lead to the final oxygen-containing polymer having an adverse effect on copper ion deposition, resulting in a significant decrease in elongation; Example 5 may lead to the aggregation of active groups affecting the conductivity of the electrolyte, thereby increasing deposition defects and causing stress concentration; Example 6 may lead to excessive electrostatic repulsion, thus inhibiting copper ion reduction and resulting in poor deposition. A low deposition rate results in a loose structure and a significant decrease in tensile strength. Example 7 may have affected the system viscosity and grain boundary migration, causing local stress concentration, both of which affected the tensile strength and elongation of the lithium-ion battery copper foil to varying degrees. A comparison between Example 8 and Example 1 shows that when the oxygen-containing polymer used is PEG6000, the tensile strength and elongation of the lithium-ion battery copper foil are insufficient and both decrease. A comparison between Example 9 and Example 1 shows that when the concentration of the oxygen-containing polymer in the electrolyte changes, the deposition defects increase significantly, leading to a decrease in the overall performance of the lithium-ion battery copper foil.

[0087] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing ultrathin lithium-ion battery copper foil with high elongation, characterized in that, The preparation method includes the following steps: S1: Dissolve copper raw materials, sulfuric acid, and deionized water to obtain copper sulfate solution. Then, after multi-stage filtration, the copper sulfate solution is mixed with additives to obtain electrolyte. S2: The electrolyte is heated by passing it through a heat exchanger and then introduced into an electrolytic cell. The temperature and current density of the electrolyte are adjusted to electrolyze the foil. S3: Passivate and heat-treat the copper foil obtained by electrolytic green foil, and then cut and roll it up to obtain the ultra-thin lithium battery copper foil; In step S1, the additive is a mixture of organic sulfides and oxygen-containing polymers; The preparation steps of the oxygen-containing polymer are as follows: (1) 5-methoxy-2-mercaptobenzimidazole, allyl chloride and catalyst were added to DMF and reacted at 80-85℃ for 5-7 h. After purification, the intermediate product was obtained. (2) Mix isopentenyl alcohol polyoxyethylene ether and deionized water, heat to 80-85℃, add initiator, and simultaneously add a mixed solution of acrylic acid, intermediate product of step (1), sodium methyl allyl sulfonate, chain transfer agent and deionized water at a uniform rate. After the addition is complete, continue to keep the reaction at the temperature for 3-4 hours, and then add alkali solution to adjust to neutrality to obtain oxygen-containing polymer.

2. The method for preparing the high-elongation ultrathin lithium-ion battery copper foil according to claim 1, characterized in that, The electrolyte in step S1 has a copper ion concentration of 70–100 g / L, a sulfuric acid concentration of 85–120 g / L, and a chloride ion concentration of 25–30 mg / L.

3. The method for preparing the high-elongation ultrathin lithium-ion battery copper foil according to claim 1, characterized in that, The organic sulfide is at least one of sodium 3-mercaptopropane sulfonate, sodium dimethylformamidopropane sulfonate, and sodium polydisulfide dipropane sulfonate.

4. The method for preparing ultrathin lithium-ion battery copper foil with high elongation according to claim 1, characterized in that, The concentration of the organic sulfide is 6–15 mg / L.

5. The method for preparing ultrathin lithium-ion battery copper foil with high elongation according to claim 1, characterized in that, The mass ratio of 5-methoxy-2-mercaptobenzimidazole to allyl chloride in step (1) is 1:(0.6-0.8).

6. The method for preparing ultrathin lithium-ion battery copper foil with high elongation according to claim 1, characterized in that, The mass ratio of acrylic acid, intermediate product of step (1), sodium methyl allyl sulfonate and isopentenyl alcohol polyoxyethylene ether in step (2) is 1:(1-2):(1-2):(10-20).

7. The method for preparing ultrathin lithium-ion battery copper foil with high elongation according to claim 1, characterized in that, The concentration of the oxygen-containing polymer is 3–12 mg / L.

8. A high-elongation ultrathin lithium-ion battery copper foil obtained by the preparation method according to any one of claims 1-7.

9. A method for preparing a high-elongation ultrathin lithium-ion battery copper foil, characterized in that, The preparation method includes the following steps: S1: Dissolve copper raw materials, sulfuric acid, and deionized water to obtain copper sulfate solution. Then, after multi-stage filtration, the copper sulfate solution is mixed with additives to obtain electrolyte. S2: The electrolyte is heated by passing it through a heat exchanger and then introduced into an electrolytic cell. The temperature and current density of the electrolyte are adjusted to electrolyze the foil. S3: Passivate and heat-treat the copper foil obtained by electrolytic green foil, and then cut and roll it up to obtain the ultra-thin lithium battery copper foil; In step S1, the additive is a mixture of organic sulfides and oxygen-containing polymers; The preparation steps of the oxygen-containing polymer are as follows: (1) 5-methoxy-2-mercaptobenzimidazole, allyl chloride and catalyst were added to DMF and reacted at 80-85℃ for 5-7 h. After purification, the intermediate product was obtained. (2) Mix isopentenyl alcohol polyoxyethylene ether and deionized water, heat to 80-85℃, add initiator, and at the same time add a mixed solution of acrylic acid, intermediate product of step (1), sodium methyl allyl sulfonate, chain transfer agent and deionized water at a uniform rate. After the addition is completed, continue to keep the temperature for 3-4 hours, and then add alkali solution to adjust to neutral to obtain oxygen-containing polymer. The mass ratio of 5-methoxy-2-mercaptobenzimidazole to allyl chloride in step (1) is 1:(0.6-0.8); The mass ratio of acrylic acid, intermediate product of step (1), sodium methyl allyl sulfonate and isopentenyl alcohol polyoxyethylene ether in step (2) is 1:(1-2):(1-2):(10-20); The concentration of the oxygen-containing polymer is 3–12 mg / L.

10. The method for preparing the high elongation ultrathin lithium battery copper foil according to claim 9, characterized in that, The electrolyte in step S1 has a copper ion concentration of 70–100 g / L, a sulfuric acid concentration of 85–120 g / L, and a chloride ion concentration of 25–30 mg / L.

11. The method for preparing the high-elongation ultrathin lithium-ion battery copper foil according to claim 9, characterized in that, The organic sulfide is at least one of sodium 3-mercaptopropane sulfonate, sodium dimethylformamidopropane sulfonate, and sodium polydisulfide dipropane sulfonate.

12. The method for preparing the high-elongation ultrathin lithium-ion battery copper foil according to claim 9, characterized in that, The concentration of the organic sulfide is 6–15 mg / L.

13. A high-elongation ultrathin lithium-ion battery copper foil obtained by the preparation method according to any one of claims 9-12, characterized in that, The ultra-thin lithium-ion battery copper foil has the following properties: tensile strength ≥490.1MPa and elongation ≥6.9%.

14. The application of the high elongation ultrathin lithium-ion battery copper foil as described in claim 8 or 13 in the negative electrode current collector of a lithium-ion battery.