Method of preparing electrode using current collector having through-pores or holes

Abstract

A method of preparing an electrode for a secondary battery, including: (i) a process of preparing a current collector in which through-pores or holes are formed and an electrode slurry containing an electrode active material; (ii) a process of bringing a shielding film into close contact with one surface of the current collector to shield pores or holes on the one surface of the current collector; (iii) a process of coating the electrode slurry on the other surface of the current collector to which the shielding film is not attached, and primarily drying to prepare an interim electrode; (iv) a process of removing the shielding film from the interim electrode; and (v) a process of secondarily drying the interim electrode to prepare the electrode.

Claims

1. A method of preparing an electrode for a secondary battery, comprising: (i) preparing a current collector in which through-pores or holes are formed; (ii) roll pressing a shielding film to bring the shielding film into close contact with one surface of the current collector to shield the through-pores or holes on the one surface of the current collector, wherein the shielding film is parafilm; (iii) coating an electrode slurry on the other surface of the current collector to which the shielding film is not attached, and primarily drying in a range of 30° C. to 60° C. for 5 minutes to 15 minutes to prepare an interim electrode; (iv) removing the shielding film from the interim electrode; and (v) secondarily drying the interim electrode in a range of 60° C. to 120° C. for more than 20 hours to prepare the electrode.

2. The method of claim 1, wherein the current collector is a metal foamed body having a porosity of 50% to 98%, a metal fiber body having a porosity of 50% to 95%, or a metal foil having an opening ratio of 15% to 70%.

3. The method of claim 2, wherein the porosity of the metal foamed body is from 70% to 98% or the porosity of the metal fiber body is from 70% to 95%.

4. The method of claim 2, wherein the opening ratio of the metal foamed body is from 50% to 70%.

5. The method of claim 1, wherein the current collector has a thickness of 10 μm to 20 μm.

6. The method of claim 1, wherein an average diameter of the through-pores is 0.1 μm to 10 μm.

7. The method of claim 1, wherein the diameter of the holes is 0.01 mm to 1 mm.

8. The method of claim 1, wherein an average interval between the through-pores is 0.1 μm to 1 μm.

9. The method of claim 1, wherein the average interval between the holes is 0.01 mm to 1 mm.

10. The method of claim 1, wherein the electrode slurry further comprises a binder and/or a conductive material.

11. The method of claim 1, wherein between (iv) the removing the shielding film from the interim electrode and (v) the secondarily drying the interim electrode, further comprising coating the electrode slurry on one surface of the current collector from which the shielding film is removed.

12. The method of claim 1, wherein in (iii) the coating the electrode slurry on the other surface of the current collector to which the shielding film is not attached, the electrode slurry is in all of the through-pores or holes of the current collector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of an electrode for a secondary battery prepared according to the related art.

(2) FIG. 2 is a schematic diagram showing a method of preparing an electrode for a secondary battery according to one embodiment of the present disclosure.

(3) FIG. 3 is a schematic diagram showing a method of preparing an electrode for a secondary battery according to another embodiment of the present disclosure.

(4) FIG. 4 is a photograph of a surface of electrodes according to Experimental Example 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the drawings, which are for easing understanding of the present disclosure, and the scope of the present disclosure is not limited thereto.

(6) FIG. 2 is a schematic diagram showing a method of preparing an electrode for a secondary battery according to one embodiment of the present disclosure.

(7) Referred to FIG. 2, a current collector 110 having a plurality of through-holes 111 is prepared (step (a)). A shielding film 120 is brought into close contact with one surface of the current collector 110 to shield the holes 111 from the one surface (step (b)).

(8) The method of bringing such a shielding film 120 into close contact with the current collector 110 is not limited, but specifically, may be performed by roll pressing.

(9) Thereafter, an electrode slurry 131 including an electrode active material is applied on the other surface of the current collector 110 to which the shielding film 120 is not attached (step (c)).

(10) In a case where the shielding film 120 is attached to shield the holes 111 to the surface opposite to the surface to be coated with the electrode slurry 131 before the electrode slurry 131 is applied, the electrode slurry 131 does not leak to the opposite surface of the coated surface through the holes 111 because the surface is shielded with the shielding film 120 and thus the electrode slurry 131 may be coated so as to have a uniform surface.

(11) After the electrode slurry is completely applied, the electrode slurry is dried at a temperature of about 30 to 60° C. for about 5 to 15 minutes to form an interim electrode 101, and the shielding film 120 is removed from the interim electrode 101 (step (d)).

(12) The drying may be carried out to prevent the hardened electrode slurry 132 from leaking through the holes 111 even after the shielding film 120 is removed by volatilizing a solvent of the electrode slurry 131 to some extent before removing the shielding film 120. However, since a thermoplastic resin may be used as the shielding film 120, in order to prevent deformation due to heat, the electrode slurry 131 is primarily dried at a relatively low temperature for a short time to harden the electrode slurry 131.

(13) After removing the shielding film 120 from the interim electrode 101, the electrode slurry is secondarily dried at a temperature of about 60 to 120° C., which is higher than the above-mentioned drying temperature, for 20 hours or more to volatilize the all of the solvent in the electrode slurry and to prepare an electrode 100 having an electrode mixture layer on the current collector 110 (step (e)).

(14) The electrode 100 thus prepared may have the electrode mixture 133 containing electrode active materials in part or all of the holes 111 of the current collector 110, and a coating height of the electrode mixture 133 applied on the current collector 111 may be uniform.

(15) FIG. 3 is a schematic diagram showing a method of preparing an electrode for a secondary battery according to another embodiment of the present disclosure.

(16) Referred to FIG. 3, as compared with FIG. 2, the processes (a1) to (d1) are the same as the processes from (a) to (d) of FIG. 2.

(17) In particular, the current collector 210 in which a plurality of through-holes 211 are formed is prepared (step (a1)). The shielding film 220 is brought into close contact with one surface of the current collector 210 to shield the holes 211 from one surface (step (b1)).

(18) Of course, the method of bringing such a shielding film 220 into close contact with the current collector 110 is not limited, but specifically, may be performed by roll pressing.

(19) Thereafter, the electrode slurry 231 including the electrode active material is applied to the other surface of the current collector 210 to which the shielding film 220 is not attached (step (c1)), and after the electrode slurry 231 is completely applied, the electrode slurry is dried at a temperature of about 30 to 60° C. for about 5 to 15 minutes to form the interim electrode 201 having electrode slurry 232 in which the solvent is partially volatilized to have a predetermined hardness, and the shielding film 220 is removed from the interim electrode 201 (step (d1)).

(20) The process thereafter differs from that of FIG. 2, in particular, the electrode slurry 231 including the electrode active material is further applied on the surface of the current collector 210 on which the electrode slurry was not formed, that is, the surface of the current collector to which the shielding film 220 was previously attached (step (e1)), and is dried at a temperature of about 60 to 120° C., which is higher than the above-mentioned drying temperature, for 20 hours or more to volatilize the electrode slurry and all of the solvent in the electrode slurry and to prepare the electrode 200 having the electrode mixture layers on both surfaces of the current collector 210 (step (f1)).

(21) In the additional coating process (e1) of the electrode slurry 231, the electrode slurry 231 does not leak to the opposite surface of the coating surface because of the electrode slurry layer 232 of the interim electrode 201 formed on one surface of the current collector 210.

(22) The electrode 200 prepared by the above process has the electrode mixture 233 containing the electrode active material in the all of the holes 211 of the current collector, and also has uniform coated surfaces on both sides of the current collector.

(23) Hereinafter, the present disclosure will be described in detail with reference to examples of the present disclosure, but the scope of the present disclosure is not limited thereto.

Example 1

(24) A parafilm was attached to one surface of a copper foil having an opening ratio of 50%, a hole diameter of 0.05 mm, a hole interval of 1 mm, and a thickness of 20 μm through a roll press method and masked.

(25) Graphite as a negative electrode active material, denka black as a conductive material, and polyvinylidene fluoride as a binder were mixed at a weight ratio of 96:2:2, and the resulting mixture was added to N-methyl pyrrolidone (NMP) to prepare a slurry, and the slurry was then applied at 2.44 mAh/cm.sup.2 to the other surface of the copper foil to which the parafilm was not attached.

(26) Thereafter, an electrode coated with the slurry was placed in an oven, dried at 45° C. for 10 minutes, taken out, and the parafilm was slowly removed.

(27) The electrode from which the parafilm was removed was again placed in the oven and dried at 80° C. for 24 hours.

Comparative Example 1

(28) Graphite as a negative electrode active material, denka black as a conductive material, and polyvinylidene fluoride as a binder were mixed at a weight ratio of 96:2:2, and the resulting mixture was added to N-methyl pyrrolidone (NMP) to prepare a slurry, and then the slurry was applied at 2.44 mAh/cm.sup.2 to one surface of a copper foil having an opening ratio of 50%, a hole diameter of 0.05 mm, and a thickness of 20 μm.

(29) Thereafter, an electrode coated with the slurry was placed in an oven and dried at 80° C. for 24 hours.

Experimental Example 1

(30) Comparison of Electrode Surfaces

(31) Photographs of surfaces of the electrodes prepared in Example 1 and Comparative Example 1 are illustrated in FIG. 4.

(32) As can be seen from FIG. 4, the surface of the electrode according to Example 1 is uniform, but the surface of the electrode according to Comparative Example 1 is non-uniform, and it can be seen that the electrodes may not be capable of controlling the same electrode loading.

(33) It should be understood by those skilled in the art that various changes may be made without departing from the spirit and scope of the present disclosure.