Preparation method of electrolyte and electrolytic copper foil for lithium batteries

Abstract

This invention relates to the field of lithium battery technology, specifically to an electrolyte and a method for preparing electrolytic copper foil for lithium batteries. The electrolyte comprises the following components at the following concentrations: sulfuric acid 105-120 g / L, brightener 15-120 mg / L, gelatin 10-60 mg / L, high-resistance agent 3-50 mg / L, stabilizer 5-55 mg / L, wetting agent 1-15 mg / L, Cl- 10-30 mg / L, and water to make up the balance. This invention can significantly improve the tensile strength of the copper foil while reducing its thickness, achieving a tensile strength greater than 700 MPa and an elongation greater than 5.0%.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to an electrolyte and a method for preparing electrolytic copper foil for lithium batteries. Background Technology

[0002] As a core component of electric vehicles, consumer electronics, and energy storage systems, the performance and safety of lithium batteries highly depend on technological breakthroughs in key materials. Among these, electrolytic copper foil, as a core material for the negative electrode current collector, plays a dual role in the battery due to its excellent conductivity, corrosion resistance, and mechanical stability: it serves as both a carrier of the negative electrode active material and a crucial channel for electron transport. With the market's increasing demand for high energy density and high safety, electrolytic copper foil is evolving towards a synergistic development of ultra-thinness and high tensile strength. However, existing electrolytic copper foil manufacturing technologies struggle to improve tensile strength while maintaining thinness, thus limiting the application performance of lithium batteries.

[0003] Chinese invention patent CN118292056 B discloses an electrolytic copper foil for lithium batteries, its preparation method, and its application. This electrolytic copper foil, through the coordinated control of the additive ratio and various parameters in the process steps, can remove internal stress in advance, resulting in a uniform and dense grain distribution. This avoids high warpage and breakage of the electrolytic copper foil caused by subsequent heat sources or deformation, and exhibits high thermal stability. However, its tensile strength and elongation are still not high enough. Summary of the Invention

[0004] The first aspect of this invention provides an electrolyte comprising the following components at the following concentrations: sulfuric acid 105-120 g / L, brightener 15-120 mg / L, gelatin 10-60 mg / L, high-resistance agent 3-50 mg / L, stabilizer 3-55 mg / L, wetting agent 1-15 mg / L, Cl... - 10-30 mg / L, add water to make up the difference.

[0005] Optionally, the Cl - Provided by hydrochloric acid.

[0006] The brightener comprises sodium thiazolinyl dithiopropane sulfonate, sodium polydithiopropane sulfonate, and sodium 3-mercapto-1-propane sulfonate, wherein the weight ratio of sodium thiazolinyl dithiopropane sulfonate, sodium polydithiopropane sulfonate, and sodium 3-mercapto-1-propane sulfonate is 1:(0.8-1.2):(1.2-2).

[0007] Optionally, the weight ratio of sodium thiazolinyl dithiopropane sulfonate, sodium polydithiopropane sulfonate, and sodium 3-mercapto-1-propane sulfonate is 1:(0.8-1.2):(1.4-2).

[0008] By selecting specific brighteners and their proportions, the tensile strength of copper foil can be improved. Sodium thiazolinyl dithiopropane sulfonate promotes grain refinement, sodium polydithiopropane sulfonate inhibits the copper deposition rate, and sodium 3-mercapto-1-propane sulfonate enhances surface smoothness. Through synergistic effects, they regulate the electrodeposition behavior of copper ions, avoiding coarse grains. In particular, a specific proportion of mercapto compounds promotes uniform nucleation by adsorbing onto the cathode surface, balancing the deposition rate and grain refinement effect, reducing defects, forming a dense structure, and enhancing surface smoothness, thereby improving tensile strength.

[0009] The high-resistance agent includes Janus Green B, polyethyleneimine alkyl salt, hexylbenzylamine salt and thiourea, wherein the weight ratio of Janus Green B, polyethyleneimine alkyl salt, hexylbenzylamine salt and thiourea is 1:(0.8-1.2):(1-2):(1.8-3).

[0010] Optionally, the weight ratio of Janus Green B, polyethyleneimine alkyl salt, hexylbenzylamine salt and thiourea is 1:(0.8-1.2):(1-2):(1.8-2.5).

[0011] By selecting specific high-resistance agents and their ratios, the tensile strength of copper foil can be further improved to greater than 700 MPa. This may be a combination of Janus Green B, polyethyleneimine alkyl salt, hexylbenzylamine salt, and thiourea, which work together to balance charge distribution and adsorption passivation, and form complexes with copper ions to inhibit dendrite growth. Polyquaternary ammonium salt and polyethyleneimine adsorb onto the cathode surface, avoiding disordered deposition of copper ions. At the same time, they work synergistically with the grain refinement effect of brighteners to avoid excessive inhibition leading to a low deposition rate, thereby forming a fine and uniform grain structure and further improving tensile strength.

[0012] The stabilizer comprises 3-methyltetrahydrothiazol-2-thione and 2-mercaptothiazoline, wherein the weight ratio of 3-methyltetrahydrothiazol-2-thione to 2-mercaptothiazoline is (0.5-1.8):1.

[0013] Optionally, the weight ratio of 3-methyltetrahydrothiazol-2-thione to 2-mercaptothiazoline is (0.8-1.5):1.

[0014] The wetting agent includes polyethylene glycol with a number average molecular weight of 600-2000 Da and polyethylene glycol with a number average molecular weight of 4000-8000 Da.

[0015] The weight ratio of polyethylene glycol with a number average molecular weight of 600-2000 Da to polyethylene glycol with a number average molecular weight of 4000-8000 Da is 1:(0.6-1.5).

[0016] Optionally, the weight ratio of polyethylene glycol with a number average molecular weight of 600-2000 Da to polyethylene glycol with a number average molecular weight of 4000-8000 Da is 1:(0.6-1.2).

[0017] By selecting specific stabilizers, wetting agents, and their proportions, elongation can be further improved under high tensile strength. Specific stabilizers and their proportions balance pH stability and antioxidant requirements, meeting stability needs in high-acidity environments. Specific wetting agents and their proportions synergistically reduce the contact angle between the electrolyte and the cathode roller, ensuring uniform copper ion deposition, reducing bubbles and porosity, and matching high-current-density electrolysis processes, avoiding uneven deposition caused by insufficient local wetting. Specific stabilizers maintain the stability of the electrolyte composition, while wetting agents ensure uniform deposition; together, they reduce microscopic defects, thereby improving elongation.

[0018] The gelatin has a weight-average molecular weight of 10,000-20,000 Da.

[0019] The second aspect of the present invention provides a method for preparing electrolytic copper foil for lithium batteries, comprising the following steps: dissolving copper wire in the electrolyte and conveying it to a foil-making machine for electrolytic foil production.

[0020] Cu in the electrolyte during electrolysis 2+ The content is 80-110g / L.

[0021] Optionally, Cu in the electrolyte 2+ The content is 80-100g / L.

[0022] The temperature of the electrolyte is 50-65℃.

[0023] Optionally, the temperature of the electrolyte is 50-60°C.

[0024] The flow rate of the conveyed volume is 50-70 m³ / h. 3 / h.

[0025] Optionally, the flow rate of the conveyed material is 50-60 m³ / h. 3 / h.

[0026] The current density of the electrolysis is 3600-6000 A / m. 2 .

[0027] Optionally, the current density of the electrolysis is 4000-6000 A / m. 2 .

[0028] Beneficial effects

[0029] 1. The tensile strength of copper foil can be improved by selecting specific brighteners and their proportions.

[0030] 2. By selecting specific high-resistance agents and their proportions, the tensile strength of copper foil can be further increased to greater than 700 MPa.

[0031] 3. By selecting specific stabilizers, wetting agents, and their ratios, the elongation can be further improved under high tensile strength.

[0032] 4. Through the synergistic effect of various additives, copper foil can simultaneously possess excellent tensile strength and elongation.

[0033] 5. This invention solves the problems of easy breakage and poor durability of copper foil in the prior art, thereby improving the charge and discharge life and safety performance of lithium batteries. Detailed Implementation

[0034] The raw materials used in the following examples and comparative examples are shown in Table 1. Components not listed are not limited to specific manufacturers:

[0035] Table 1

[0036]

[0037]

[0038] Example 1

[0039] An electrolyte comprises the following components at the following concentrations: sulfuric acid 110 g / L, brightener 68 mg / L, gelatin 35 mg / L, high-resistance agent 27 mg / L, stabilizer 30 mg / L, wetting agent 7 mg / L, Cl... - 20 mg / L, water to make up the balance; the Cl - Provided by hydrochloric acid.

[0040] The brightener is sodium thiazolinyl dithiopropane sulfonate, sodium polydithiopropane sulfonate, and sodium 3-mercapto-1-propane sulfonate, wherein the weight ratio of sodium thiazolinyl dithiopropane sulfonate, sodium polydithiopropane sulfonate, and sodium 3-mercapto-1-propane sulfonate is 1:1:1.5.

[0041] The high-resistance agent is Janus Green B, polyethyleneimine alkyl salt, hexylbenzylamine salt, and thiourea, and the weight ratio of Janus Green B, polyethyleneimine alkyl salt, hexylbenzylamine salt, and thiourea is 1:1:1.5:2.

[0042] The stabilizer is 3-methyltetrahydrothiazol-2-thione and 2-mercaptothiazoline, wherein the weight ratio of 3-methyltetrahydrothiazol-2-thione and 2-mercaptothiazoline is 1:1.

[0043] The wetting agent comprises polyethylene glycol with a number average molecular weight of 1000 Da and polyethylene glycol with a number average molecular weight of 4000 Da, wherein the weight ratio of the polyethylene glycol with a number average molecular weight of 1000 Da to the polyethylene glycol with a number average molecular weight of 4000 Da is 1:0.9.

[0044] A method for preparing electrolytic copper foil for lithium batteries includes the following steps: dissolving copper wire in the electrolyte and conveying it to a foil-making machine for electrolytic foil production.

[0045] Cu in the electrolyte during electrolysis 2+ The content is 90 g / L; the temperature of the electrolyte is 56°C; the delivery flow rate is 55 m³ / L. 3 / h; the current density of the electrolysis is 5000 A / m 2 .

[0046] Example 2

[0047] The specific implementation method is the same as in Example 1; the difference is that the temperature of the electrolyte is 50°C.

[0048] Example 3

[0049] The specific implementation method is the same as in Example 1; the difference is that the flow rate of the conveyed volume is 50m³. 3 / h.

[0050] Example 4

[0051] The specific implementation method is the same as in Example 1; the difference is that the temperature of the electrolyte is 60°C and the current density of the electrolysis is 4000 A / m. 2 .

[0052] Example 5

[0053] The specific implementation method is the same as in Example 1; the difference is that the flow rate of the conveyed volume is 60m³. 3 / h.

[0054] Example 6

[0055] The specific implementation method is the same as in Example 1; the difference is that the current density of the electrolysis is 6000 A / m. 2 Sulfuric acid 110g / L.

[0056] Example 7

[0057] The specific implementation method is the same as in Example 1; the difference is that the Cu in the electrolyte during electrolysis... 2+ The content is 100g / L; gelatin 10mg / L.

[0058] Example 8

[0059] The specific implementation method is the same as in Example 1; the difference is that the sulfuric acid is 120g / L.

[0060] Example 9

[0061] The specific implementation method is the same as in Example 1; the difference is that the gelatin is 60 mg / L and Cl- is 10 mg / L.

[0062] Example 10

[0063] The specific implementation method is the same as in Example 1; the difference is that the brightening agent is 15 mg / L.

[0064] Example 11

[0065] The specific implementation method is the same as in Example 1; the difference is that the Cl- is 30 mg / L and the high resistance agent is 3 mg / L.

[0066] Example 12

[0067] The specific implementation method is the same as in Example 1; the difference is that the brightener is 120 mg / L and the stabilizer is 3 mg / L.

[0068] Example 13

[0069] The specific implementation method is the same as in Example 1; the difference is that the high resistance agent is 50 mg / L and the wetting agent is 1 mg / L.

[0070] Example 14

[0071] The specific implementation method is the same as in Example 1; the difference is that the stabilizer is 55 mg / L.

[0072] Example 15

[0073] The specific implementation method is the same as in Example 1; the difference is that the wetting agent is 15 mg / L.

[0074] Comparative Example 1

[0075] The specific implementation method is the same as in Example 1; the difference is that no brightener is added.

[0076] Comparative Example 2

[0077] The specific implementation method is the same as in Example 1; the difference is that no high-resistance agent is added.

[0078] Comparative Example 3

[0079] The specific implementation method is the same as in Example 1; the difference is that no stabilizer is added.

[0080] Comparative Example 4

[0081] The specific implementation method is the same as in Example 1; the difference is that no wetting agent is added.

[0082] Comparative Example 5

[0083] The specific implementation method is the same as in Example 1; the difference is that gelatin is not added.

[0084] Comparative Example 6

[0085] The specific implementation method is the same as in Example 1; the difference is that the Cl- is 40 mg / L.

[0086] Comparative Example 7

[0087] The specific implementation method is the same as in Example 1; the difference is that the temperature of the electrolyte is 48°C.

[0088] Comparative Example 8

[0089] The specific implementation method is the same as in Example 1; the difference is that the flow rate of the conveyed volume is 40m³. 3 / h.

[0090] Comparative Example 9

[0091] The specific implementation method is the same as in Example 1; the difference is that the current density of the electrolysis is 3500 A / m. 2 .

[0092] Comparative Example 10

[0093] The specific implementation method is the same as in Example 1; the difference is that the Cu in the electrolyte during electrolysis... 2+ The content is 75g / L.

[0094] Comparative Example 11

[0095] The specific implementation method is the same as in Example 1; the difference is that the sulfuric acid is 100g / L.

[0096] Comparative Example 12

[0097] The specific implementation method is the same as in Example 1; the difference is that the weight ratio of sodium thiazolinyl dithiopropane sulfonate, sodium polydithiopropane sulfonate and sodium 3-mercapto-1-propane sulfonate is 1:1:1.

[0098] Comparative Example 13

[0099] The specific implementation method is the same as in Example 1; the difference is that sodium 3-(benzoimidazole-2-mercapto)-propanesulfonate is used instead of sodium 3-mercapto-1-propanesulfonate.

[0100] Comparative Example 14

[0101] The specific implementation method is the same as in Example 1; the difference is that the weight ratio of Janus Green B, polyethyleneimine alkyl salt, hexylbenzylamine salt and thiourea is 1:1:1:1.5:.

[0102] Comparative Example 15

[0103] The specific implementation method is the same as in Example 1; the difference is that diethylpropynylamine is used instead of polyethyleneimine alkyl salt.

[0104] Comparative Example 16

[0105] The specific implementation method is the same as in Example 1; the difference is that the weight ratio of 3-methyltetrahydrothiazol-2-thione and 2-mercaptothiazoline is 2:1.

[0106] Comparative Example 17

[0107] The specific implementation method is the same as in Example 1; the difference is that 2-methyl-4-isothiazolin-3-one is used instead of 3-methyltetrahydrothiazolin-2-thionone.

[0108] Comparative Example 18

[0109] The specific implementation method is the same as in Example 1; the difference is that the weight ratio of the polyethylene glycol with a number average molecular weight of 1000 Da and the polyethylene glycol with a number average molecular weight of 4000 Da is 2:1.

[0110] Performance testing methods

[0111] Copper foil of 6 micrometers was prepared according to the methods in the examples and comparative examples. The tensile strength and elongation of the copper foil were tested according to the test methods in GB / T29847-2013. The test data are listed in Table 2.

[0112] Performance test data

[0113] Table 2

[0114]

[0115]

Claims

1. An electrolyte, characterized by, A composition comprising components in the following concentrations: sulfuric acid 105-120 g / L, brightener 15-120 mg / L, gelatin 10-60 mg / L, high resistance agent 3-50 mg / L, stabilizer 3-55 mg / L, wetting agent 1-15 mg / L, Cl - 10-30 mg / L, water to make up the balance; the brightener comprising sodium thiazolinyl dithiopropane sulfonate, sodium polydithiodipropyl sulfonate, and sodium 3-mercapto-1-propane sulfonate, the weight ratio of the sodium thiazolinyl dithiopropane sulfonate, sodium polydithiodipropyl sulfonate, and sodium 3-mercapto-1-propane sulfonate being 1:(0.8-1.2):(1.2-2); the high resistance agent comprising gentian violet B, polyethylene imine alkyl salt, hexyl benzyl amine salt, and thiourea, the weight ratio of the gentian violet B, polyethylene imine alkyl salt, hexyl benzyl amine salt, and thiourea being 1:(0.8-1.2):(1-2):(1.8-3); the stabilizer comprising 3-methyl tetrahydrothiazole-2-thione and 2-mercapto thiazoline, the weight ratio of the 3-methyl tetrahydrothiazole-2-thione and 2-mercapto thiazoline being (0.5-1.8):1; the wetting agent comprising polyethylene glycol having a number average molecular weight of 600-2000 Da and polyethylene glycol having a number average molecular weight of 4000-8000 Da; the weight ratio of the polyethylene glycol having a number average molecular weight of 600-2000 Da and the polyethylene glycol having a number average molecular weight of 4000-8000 Da being 1:(0.6-1.5).

2. A method for producing an electrolytic copper foil for a lithium battery, characterized by, comprising the steps of: Copper wire is dissolved in the electrolyte of claim 1 and delivered to a green foil machine for electrolytic foil production; the Cu 2+ concentration is 80-110 g / L.

3. The method for preparing electrolytic copper foil for lithium batteries according to claim 2, characterized in that, The temperature of the electrolyte is 50-65°C. The temperature of the electrolyte is 50-65°C.

4. The method for preparing electrolytic copper foil for lithium batteries according to claim 2, characterized in that, The flow rate of the delivery is 50-70 m 3 / h.

5. The method for preparing electrolytic copper foil for lithium batteries according to claim 2, characterized in that, The current density of the electrolysis is 3600-6000 A / m 2 .

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