Surface treatment agent, surface treatment method of copper foil and copper foil negative electrode current collector

Abstract

The invention provides a surface treatment agent, a surface treatment method of a copper foil and a copper foil negative electrode current collector, and belongs to the technical field of energy materials. The copper salt is used as a copper source, the N-alkyl pyridine halogen salt ionic liquid is used as a halogen source, the copper salt and the N-alkyl pyridine halogen salt ionic liquid react in the solution to form cuprous halide particles on the surface of the copper foil in situ, the specific surface area and the roughness of the surface of the copper foil negative electrode current collector are increased, the copper foil negative electrode current collector is firmly combined with an active substance, and therefore the specific capacity and the rate of the lithium ion battery are improved; cu < + > in the cuprous halide particles formed on the surface of the copper foil also participates in electrochemical reaction, so that the specific capacity of the lithium ion battery is further improved. The result of the embodiment shows that the capacity of the lithium ion battery prepared from the copper foil negative current collector obtained by carrying out surface treatment on the copper foil by the surface treating agent provided by the invention can reach 825mAh g <-1 >; 100 times of charge-discharge cycles are carried out under the large current density of 1Ag <-1 >, and the retention rate can reach 95%.

Description

Technical Field

[0001] The present invention relates to the field of energy materials, and in particular to a surface treatment agent, a surface treatment method for copper foil, and a copper foil negative electrode current collector. Background Art

[0002] In recent years, lithium-ion batteries have gained widespread application in consumer electronics, new energy vehicles, and energy storage power stations due to their high energy density, long cycle life, and excellent safety performance. They are primarily composed of positive electrode materials, negative electrode materials, electrolytes, and current collectors. Because the active substances in the electrode materials are directly coated onto the current collector surface and in direct contact with it, the surface structure and material composition of the current collector significantly affect battery performance.

[0003] Copper foil, as a new type of negative electrode current collector material for lithium-ion batteries, has the characteristics of good electrical and thermal conductivity, high stability, small size, light weight and low cost. However, since the active material is simply coated on the surface of the copper foil, the binding force is weak and the interface impedance is high. During the charge and discharge cycle, the Li + The continuous insertion and extraction between the positive and negative electrodes will cause the volume change of the active material and significant electrode stress, making the active material easy to fall off from the copper foil surface, resulting in reduced battery capacity and poor rate performance. Currently, in the existing technology, copper foil is treated by immersion to obtain copper foil coated with cuprous chloride, which is used for lithium-ion batteries with a discharge capacity of 390 to 440 mAh g -1 , which effectively improves the discharge capacity of lithium-ion batteries, but it is still relatively low. Summary of the Invention

[0004] The purpose of the present invention is to provide a surface treatment agent, a surface treatment method for copper foil and a copper foil negative electrode current collector. The copper foil negative electrode current collector obtained by surface treating the copper foil with the surface treatment agent provided by the present invention has a strong binding force with the active material, and the lithium ion battery prepared has high capacity and good rate performance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The invention provides a surface treatment agent, comprising independently packaged copper salt solution and N-alkylpyridinium halide ionic liquid; the N-alkylpyridinium halide ionic liquid comprises N-ethylpyridinium halide ionic liquid or N-butylpyridinium halide ionic liquid.

[0007] Preferably, the molar ratio of copper ions in the copper salt solution to the N-alkylpyridinium halide ionic liquid is 1:(0.02-1).

[0008] Preferably, the copper salt in the copper salt solution includes copper sulfate.

[0009] Preferably, the concentration of the copper salt solution is 0.6-1.2 mol / L.

[0010] Preferably, the N-ethylpyridinium halide ionic liquid includes N-ethylpyridinium chloride ionic liquid, N-ethylpyridinium bromide ionic liquid or N-ethylpyridinium iodide ionic liquid.

[0011] Preferably, the N-butylpyridinium halide ionic liquid includes N-butylpyridinium chloride ionic liquid, N-butylpyridinium bromide ionic liquid or N-butylpyridinium iodide ionic liquid.

[0012] The present invention also provides a surface treatment method for copper foil, which uses the surface treatment agent described in the above technical solution, comprising the following steps:

[0013] A copper foil is impregnated with a copper salt solution and an N-alkylpyridinium halide ionic liquid to obtain a copper foil negative electrode current collector.

[0014] Preferably, the immersion time is 5 to 50 minutes.

[0015] The present invention also provides a copper foil negative electrode current collector obtained by the surface treatment method described in the above technical solution, comprising copper foil and cuprous halide particles in-situ coated on the surface of the copper foil.

[0016] The present invention also provides a lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises a copper foil negative electrode current collector and a negative electrode material coated on the surface of the copper foil negative electrode current collector, and the copper foil negative electrode current collector is the copper foil negative electrode current collector described in the above technical solution.

[0017] The present invention provides a surface treatment agent, comprising independently packaged copper salt solution and N-alkylpyridinium halide ionic liquid; the N-alkylpyridinium halide ionic liquid comprises N-ethylpyridinium halide ionic liquid or N-butylpyridinium halide ionic liquid. The present invention uses copper salt as a copper source and N-alkylpyridinium halide ionic liquid as a halogen source. The two react in solution to form cuprous halide particles in situ on the surface of copper foil, thereby increasing the specific surface area and roughness of the surface of the copper foil negative electrode current collector, making it firmly bonded with the active material, thereby improving the specific capacity and rate of the lithium ion battery; and the cuprous halide particles formed on the surface of the copper foil have Cu + It can also participate in electrochemical reactions, further increasing the specific capacity of lithium-ion batteries. The results of the examples show that the capacity of lithium-ion batteries made from copper foil negative electrode current collectors obtained by surface treating copper foil with the surface treatment agent provided by the present invention can reach 825 mAh g -1 ; in 1Ag -1 After 100 charge and discharge cycles at a high current density, the retention rate can reach 95%, and the rate performance is good. DETAILED DESCRIPTION

[0018] The invention provides a surface treatment agent, which comprises independently packaged copper salt solution and N-alkyl pyridinium halide ionic liquid.

[0019] In the present invention, the N-alkylpyridinium halide ionic liquid includes N-ethylpyridinium halide ionic liquid or N-butylpyridinium halide ionic liquid. The present invention limits the type of N-alkylpyridinium halide ionic liquid so that the subsequent surface treatment of the copper foil is more sufficient.

[0020] In the present invention, the N-ethylpyridinium halide ionic liquid preferably includes an N-ethylpyridinium chloride ionic liquid, an N-ethylpyridinium bromide ionic liquid, or an N-ethylpyridinium iodide ionic liquid. In the present invention, the N-butylpyridinium halide ionic liquid preferably includes an N-butylpyridinium chloride ionic liquid, an N-butylpyridinium bromide ionic liquid, or an N-butylpyridinium iodide ionic liquid. The present invention further provides a more comprehensive treatment of the copper foil surface by limiting the type of the N-ethylpyridinium halide ionic liquid or the N-butylpyridinium halide ionic liquid.

[0021] In the present invention, the copper salt solution is preferably a copper sulfate solution. The present invention provides a copper source by limiting the type of copper salt solution, so as to facilitate the subsequent more sufficient formation of cuprous halide particles on the surface of the copper foil, increase the specific surface area and roughness of the copper foil negative electrode current collector surface, and more firmly combine with the active material, thereby improving the specific capacity and rate of the lithium ion battery; and the copper halide particles formed on the surface of the copper foil have a Cu content of 0.0447777. + It also participates in electrochemical reactions, further improving the specific capacity of lithium-ion batteries.

[0022] In the present invention, the concentration of the copper salt solution is preferably 0.6 to 1.2 mol / L. In embodiments of the present invention, the concentration of the copper salt solution can be specifically 0.6 mol / L, 0.8 mol / L, 1 mol / L, or 1.2 mol / L. The present invention limits the concentration of the copper salt to ensure sufficient copper source, thereby allowing for a more complete reaction with the halogen source in the N-alkylpyridinium halide ionic liquid during subsequent surface treatment of the copper foil.

[0023] In the present invention, the molar ratio of copper ions in the copper salt solution to the N-alkylpyridinium halide ionic liquid is preferably 1:(0.02-1). In embodiments of the present invention, the molar ratio of copper in the copper salt solution to the N-alkylpyridinium halide ionic liquid can be specifically 1:0.02, 1:0.04, 1:0.06, 1:0.08, 1:0.1, 1:0.3, 1:0.5, 1:0.7, 1:0.9, or 1:1. The present invention limits the molar ratio of copper in the copper salt solution to the N-alkylpyridinium halide ionic liquid to ensure a more complete reaction on the copper foil surface to form cuprous halide particles, thereby providing the negative electrode current collector with a greater roughness and specific surface area.

[0024] The present invention adopts a copper salt solution to provide a copper source and an N-alkylpyridine halide ionic liquid to provide a halogen source. After the two are mixed, the copper foil is surface treated to form cuprous halide particles on the surface of the copper foil, thereby increasing the specific surface area and roughness of the copper foil negative electrode current collector surface, and firmly combining with the active material, thereby improving the specific capacity and rate of the lithium ion battery; and the cuprous halide particles formed on the surface of the copper foil have Cu + It can also participate in electrochemical reactions to further increase the specific capacity of lithium-ion batteries.

[0025] The present invention also provides a surface treatment method for copper foil, which uses the surface treatment agent described in the above technical solution to perform surface treatment, preferably comprising the following steps:

[0026] A copper foil is impregnated with a copper salt solution and an N-alkylpyridinium halide ionic liquid to obtain a copper foil negative electrode current collector.

[0027] In the present invention, the copper foil is preferably a composite copper foil. In the present invention, the composite copper foil preferably includes a copper / polyimide composite copper foil, a copper / polyester composite copper foil, or a copper / polyamide composite copper foil. By limiting the type of copper foil, the present invention further improves the specific capacity of the resulting lithium-ion battery.

[0028] In the present invention, the immersion time is preferably 5 to 50 minutes. In embodiments of the present invention, the immersion time can be specifically 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, or 50 minutes. The present invention limits the immersion time to ensure that the surface treatment agent treats the copper foil more thoroughly.

[0029] The copper foil negative electrode current collector prepared by the present invention has a greater roughness and specific surface area, so that it is more firmly combined with the active material, thereby improving the specific capacity and rate of the lithium ion battery; and the copper halide particles formed on the surface of the copper foil have a larger surface roughness and specific surface area, so that it is more firmly combined with the active material, thereby improving the specific capacity and rate of the lithium ion battery; + It can also participate in electrochemical reactions to further increase the specific capacity of lithium-ion batteries.

[0030] The present invention also provides a copper foil negative electrode current collector obtained by the surface treatment method described in the above technical solution, preferably comprising copper foil and cuprous halide particles coated on the surface of the copper foil.

[0031] In the present invention, the particle size of the cuprous halide particles is preferably 70 to 200 nm. In specific embodiments of the present invention, the particle size of the cuprous halide particles can be specifically 70 to 200 nm, 80 to 200 nm, 90 to 200 nm, 100 to 180 nm, 120 to 180 nm, or 150 to 160 nm. By limiting the particle size of the cuprous halide particles, the present invention ensures a rougher copper foil surface and a larger specific surface area.

[0032] In the present invention, cuprous halide particles are coated on the surface of the copper foil to make the copper foil negative electrode current collector have a greater roughness and specific surface area, thereby combining with the active material more firmly, thereby improving the specific capacity and rate of the lithium ion battery.

[0033] The present invention also provides a lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode comprises a copper foil negative electrode current collector and a negative electrode material coated on the surface of the copper foil negative electrode current collector. The copper foil negative electrode current collector is the copper foil negative electrode current collector described in the above technical solution.

[0034] The present invention does not specifically limit the materials for the positive electrode and electrolyte; any positive electrode, negative electrode, and electrolyte materials known in the art may be used. In the present invention, the positive electrode material is preferably LiFePO4. In the present invention, the negative electrode material is preferably a graphite electrode. In the present invention, the electrolyte is preferably a 1M LiPF6 solution of dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, and vinylene carbonate.

[0035] The present invention has no particular limitation on the preparation method of the lithium-ion battery, and any preparation method well known in the art may be used.

[0036] The lithium ion battery prepared by the invention has high specific capacity and good rate performance.

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. 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.

[0038] Example 1

[0039] A surface treatment agent, comprising a copper sulfate solution with a concentration of 0.8 mol / L and an N-butylpyridinium chloride ionic liquid; the molar ratio of copper ions in the copper sulfate solution to the N-butylpyridinium chloride ionic liquid is 1:1;

[0040] A surface treatment method for copper / polyimide composite copper foil, using the above-mentioned surface treatment agent, comprises the following steps:

[0041] A copper / polyimide composite copper foil is impregnated with a mixture of a copper sulfate solution and an N-alkylpyridinium halide ionic liquid for 10 minutes to obtain a copper / polyimide composite copper foil negative electrode current collector; the copper / polyimide composite copper foil negative electrode current collector comprises a copper / polyimide composite copper foil and cuprous chloride particles with a particle size of 150 to 170 nm in situ coated on the surface of the copper foil.

[0042] Example 2

[0043] The difference between this embodiment and Example 1 is that the N-butylpyridinium chloride ionic liquid is replaced with the N-butylpyridinium bromide ionic liquid; the molar ratio of copper ions in the copper sulfate solution to the N-butylpyridinium bromide ionic liquid is 1:0.02; the rest is the same as in Example 1, and a copper / polyimide composite copper foil negative electrode current collector is obtained; the copper / polyimide composite copper foil negative electrode current collector is composed of a copper / polyimide composite copper foil and cuprous bromide particles with a particle size of 150 to 160 nm in situ coated on the surface of the copper foil.

[0044] Example 3

[0045] The difference between this embodiment and Example 1 is that the N-butylpyridinium chloride ionic liquid is replaced with the N-butylpyridinium iodide ionic liquid; the molar ratio of copper ions in the copper sulfate solution to the N-butylpyridinium iodide ionic liquid is 1:0.08; the rest is the same as in Example 1, and a copper / polyimide composite copper foil negative electrode current collector is obtained; the copper / polyimide composite copper foil negative electrode current collector is composed of a copper / polyimide composite copper foil and cuprous iodide particles with a particle size of 120 to 150 nm in situ coated on the surface of the copper foil.

[0046] Example 4

[0047] The difference between this embodiment and Example 1 is that the molar ratio of copper ions in the copper sulfate solution to the N-butylpyridinium bromide ionic liquid is 1:0.8; the rest is the same as Example 1, and a copper / polyimide composite copper foil negative electrode current collector is obtained; the copper / polyimide composite copper foil negative electrode current collector is composed of a copper / polyimide composite copper foil and cuprous chloride particles with a particle size of 120 to 200 nm in situ coated on the surface of the copper foil.

[0048] Example 5

[0049] The difference between this embodiment and Example 1 is that the immersion time is 50 minutes; the rest is the same as Example 1, and a copper / polyimide composite copper foil negative electrode current collector is obtained; the copper / polyimide composite copper foil negative electrode current collector is composed of a copper / polyimide composite copper foil and cuprous chloride particles with a particle size of 90 to 200 nm in situ coated on the surface of the copper foil.

[0050] Example 6

[0051] The difference between this embodiment and Example 1 is that the immersion time is 5 minutes; the rest is the same as Example 1, and a copper / polyimide composite copper foil negative electrode current collector is obtained; the copper / polyimide composite copper foil negative electrode current collector is composed of a copper / polyimide composite copper foil and cuprous chloride particles with a particle size of 100 to 150 nm in situ coated on the surface of the copper foil.

[0052] Comparative Example 1

[0053] The difference between this comparative example 1 and example 1 is that the N-butylpyridinium chloride ionic liquid is replaced with 1-butyl-3-methylimidazolium chloride; a copper / polyimide composite copper foil negative electrode current collector is obtained; the copper / polyimide composite copper foil negative electrode current collector is composed of a copper / polyimide composite copper foil and cuprous chloride particles with a particle size of 90 to 100 nm in situ coated on the surface of the copper foil.

[0054] Application Examples 1 to 6

[0055] A lithium-ion battery comprises a positive electrode, a negative electrode and an electrolyte;

[0056] The preparation method of the above-mentioned lithium-ion battery is as follows: graphite, acetylene black, polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) are mixed together in a mass ratio of 7:1:1:1 to form a slurry, which is respectively coated on the copper / polyimide composite copper foil negative electrode collector prepared in Examples 1 to 6, and heated at 120°C for 6 hours under vacuum conditions to obtain a negative electrode, and then LiFePO4 is used as a positive electrode, and a 1M LiPF6 solution of dimethyl carbonate (DMC), ethylene carbonate (EC), ethyl methyl carbonate (EMC) and vinylene carbonate (VC) is used as an electrolyte to prepare a lithium-ion battery.

[0057] Comparative Application Example 1

[0058] The difference between this comparative application example and application examples 1 to 6 is that the copper / polyimide composite copper foil negative electrode current collector prepared in examples 1 to 6 is replaced by the copper / polyimide composite copper foil negative electrode current collector of comparative example 1.

[0059] The charge and discharge tests were carried out in the voltage range of 0.01V to 3.00V for the corresponding application examples 1 to 6 and the comparative application example 1. The discharge specific capacities of the lithium-ion batteries prepared in the application examples 1 to 6 were 825mAh g -1 , 800mAh g -1 , 789mAh g -1 , 745mAh g -1 , 759mAh g -1 and 725mAh g -1 The lithium-ion battery discharge capacity obtained in Comparative Application Example 1 is 394 mAh g -1 It can be seen that the lithium ion batteries prepared in Application Examples 1 to 6 of the present invention have high discharge specific capacities.

[0060] In 1Ag -1 The corresponding application examples 1 to 6 and comparative application example 1 were subjected to 100 charge and discharge cycles at the current density. The discharge specific capacities of the lithium-ion batteries prepared in application examples 1 to 6 and comparative application example 1 in the first cycle were 278 mAh g -1 , 256mAh g -1 , 245mAh g -1 , 241mAh g -1 , 228mAh g -1 , 218mAh g -1 , 221mAh g -1 and 98mAh g -1 After 100 cycles, the discharge capacity is still 255mAh g -1 , 230mAh g -1 , 220.5mAh g -1 , 221.7mAh g -1 , 205mAh g -1 , 198mAhg -1 、198.9mAh g -1 , 88mAh g -1 The specific capacity retention rates are 95%, 93%, 90%, 92%, 90%, 91% and 90% respectively. -1 After 100 charge and discharge cycles at the same current density, the discharge specific capacity of the lithium ion batteries prepared in Application Examples 1 to 6 of the present invention is much higher.

[0061] In summary, it can be seen that the negative electrode current collector obtained by surface treating the copper foil with the surface treatment agent provided by the present invention has a strong binding force with the active material, and the lithium ion battery prepared has a high capacity and good rate performance.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A surface treatment agent comprising independently packaged copper salt solution and N-alkylpyridinium halide ionic liquid; the N-alkylpyridinium halide ionic liquid comprises N-ethylpyridinium halide ionic liquid or N-butylpyridinium halide ionic liquid.

2. The surface treatment agent according to claim 1, characterized in that The molar ratio of copper ions in the copper salt solution to the N-alkylpyridinium halide ionic liquid is 1:(0.02-1).

3. The surface treatment agent according to claim 1 or 2, characterized in that The copper salt in the copper salt solution includes copper sulfate.

4. The surface treatment agent according to claim 3, characterized in that The concentration of the copper salt solution is 0.6-1.2 mol / L.

5. The surface treatment agent according to claim 1, characterized in that The N-ethylpyridinium halide ionic liquid includes an N-ethylpyridinium chloride ionic liquid, an N-ethylpyridinium bromide ionic liquid or an N-ethylpyridinium iodide ionic liquid.

6. The surface treatment agent according to claim 1, characterized in that The N-butylpyridinium halide ionic liquid includes N-butylpyridinium chloride ionic liquid, N-butylpyridinium bromide ionic liquid or N-butylpyridinium iodide ionic liquid.

7. A method for surface treatment of copper foil, using the surface treatment agent according to any one of claims 1 to 6, comprising the following steps: A copper foil is impregnated with a copper salt solution and an N-alkylpyridinium halide ionic liquid to obtain a copper foil negative electrode current collector.

8. The surface treatment method according to claim 8, characterized in that: The immersion time is 5 to 50 minutes.

9. A copper foil negative electrode current collector obtained by the surface treatment method according to any one of claims 7 to 8, comprising copper foil and cuprous halide particles in-situ coated on the surface of the copper foil.

10. A lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises a copper foil negative electrode current collector and a negative electrode material coated on the surface of the copper foil negative electrode current collector, characterized in that: The copper foil negative electrode current collector is the copper foil negative electrode current collector according to claim 9.