KR20170068064A - An etching method for substarate and a secondary battery comprising substrate ethched by the same - Google Patents

Abstract

The present invention relates to a method of etching an electrode, a secondary battery including the electrode etched by the above method, and a method of manufacturing the same, and the present invention can economically increase the speed of the laser ablation process, The degree of freedom of the shape of the battery can be increased and the energy can be concentrated and the upper layer can be selectively removed, thereby providing a high-quality secondary battery economically.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a secondary battery including an electrode and an electrode etched by the etching method,

The present invention relates to a method of manufacturing a secondary battery, which comprises etching an electrode by an electrode etching method, and etching the electrode by the etching method of the electrode, and a secondary battery including the electrode etched by the etching method.

2. Description of the Related Art As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing, and a lot of research has been conducted on secondary batteries that can meet various demands.

Such a secondary battery is manufactured such that the electrode assembly is embedded in the battery case together with the electrolyte solution. The electrode assembly may be classified into a stack type, a folding type, and a stack-folding type according to a manufacturing method. In the case of the stacked or stacked-folded electrode assembly, the unit assembly has a structure in which an anode and a cathode are sequentially stacked with a separator interposed therebetween. To fabricate such an electrode assembly, it is necessary to first fabricate a positive electrode and a negative electrode having electrode tabs.

That is, in order to manufacture a unit electrode having an electrode tab, a notching process is required to form an electrode tab on a continuous electrode sheet coated with an electrode active material on one or both surfaces. The notching process is generally performed by a process of placing an electrode sheet on a die and pressing a part of the electrode sheet using a press.

JP 5600825 B2

On the other hand, the inventors of the present invention have recognized that when the notching process is performed as described above, the shape of the electrode having the electrode tab is limited and the degree of freedom of the battery shape is lowered. The degree of freedom of the battery shape can be increased. In addition, when such a laser ablation process is introduced into the manufacture of a secondary battery, there is a limit to increase the power of the laser, and it is found that it is difficult to increase the process speed, and by examining a method of economically improving the process speed, The inventors invented the present invention which can economically provide the secondary battery.

That is, an object of the present invention is to solve the above problems of the prior art,

In the etching of the electrode, the laser ablation process is introduced to increase the degree of freedom of the shape of the cell, and energy is transferred by using a hot air fan together with the laser, thereby reducing the amount of energy to be transferred through the laser, And a method of etching an electrode.

It is another object of the present invention to provide a secondary battery comprising an electrode etched by the method of etching the electrode.

In order to solve the above problems,

A method of etching an electrode by a laser ablation process in which a part of an active material film formed on an electrode surface is removed by laser irradiation,

And heating the electrode before the etching.

The present invention also provides a method of manufacturing a secondary battery, which comprises etching the electrode by an etching method of the electrode.

The present invention also provides a secondary battery comprising an electrode etched by the method of etching the electrode.

According to the present invention, it is possible to increase the degree of freedom of the shape of the battery, economically increase the speed of the laser ablation process, effectively etch the electrode, focus the energy and selectively remove the upper layer, As shown in FIG.

1 is a photograph showing the result of etching an electrode according to Example 1. Fig.
Fig. 2 is an enlarged photograph of Fig.
Fig. 3 is a photograph showing the result of etching the electrode according to Comparative Example 1. Fig.
Fig. 4 is an enlarged photograph of Fig.
5 is a photograph showing the result of etching the electrode according to the second embodiment.
Fig. 6 is an enlarged photograph of Fig.
7 is a photograph showing the result of etching the electrode according to Comparative Example 2. Fig.
Fig. 8 is an enlarged photograph of Fig.
9 is a schematic view briefly showing the laser ablation process of the first to fourth embodiments of the present invention.
10 is a schematic view briefly showing the metal notching process of Comparative Examples 1 and 2 of the present invention.

According to the present invention,

A method of etching an electrode by a laser ablation process in which a part of an active material film formed on an electrode surface is removed by laser irradiation,

And heating the electrode before the etching.

The "electrode" in this specification is not particularly limited, but may preferably be an electrolyte battery electrode component.

In the present specification, the term " laser ablation process " means a method of removing a part of a film formed two-dimensionally on an electrode substrate by irradiating a laser.

The etching of the electrode by the laser ablation process in the present invention is intended to increase the degree of freedom of the shape of the battery. Conventionally provided electrode assemblies with tabs have a uniform shape, and the design of parts of devices using such secondary batteries has also been limited, for example, in consideration of the shape of the secondary battery. However, by the etching method of the electrode provided by the present invention, it is possible to improve the degree of freedom of shape of the battery, and it is possible to design the device more variously without depending on the shape of the electrode assembly.

That is, when the laser ablation process is applied during the electrode etching, the tab can be cut so that the electrode active material is etched so that the shape of the tab can be obtained in a desired shape. For example, a structure having a tab inside the electrode, an electrode higher than the tab, and a tab shape other than a rectangular shape can be obtained, but the present invention is not limited thereto.

The reason for including the step of heating the electrode before the etching in the present invention is to heat the electrode and transfer the energy with the laser, thereby reducing the amount of energy to be transferred through the laser, thereby increasing the process speed economically .

The etch rate is determined by the pulse energy and the peak power of the laser. However, there is a limit to increase the power of the laser, which makes it difficult to increase the processing speed. In order to increase the laser ablation process speed, a method of using a plurality of scanners of the optical system However, the method has disadvantages in terms of cost, and the present invention solves such disadvantages.

In one embodiment of the present invention,

The active material layer may be a positive active material layer or a negative active material layer.

In another embodiment of the present invention,

The cathode active material film may be a lithium-containing metal oxide or a sulfur compound as a substance capable of causing an electrochemical reaction,

Particularly, lithium-containing metal oxides include LiCoO ₂ , LiMn _x O _2x (x = 1 or 2), LiFePO ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O _2, and LiNi _{1 - x} Co _x M _y O ₂ at least one element selected from the group consisting of Mg, Ca, Sr, Ba and La, and y = 0.001 to 0.02) But is not limited thereto.

In another embodiment of the present invention,

The negative electrode active material layer is preferably composed of at least one selected from the group consisting of graphite, a silicon compound, a germanium-containing material, and a tin-containing material, but is not limited thereto.

In another embodiment of the present invention,

The heating may be performed by at least one selected from the group consisting of a heat gun, a RF induction unit, an induction infrared (IR) lamp, and a hot plate. It is desirable because of the availability of equipment installation, but there is no limitation to the kind of heat irradiation means that can achieve the same effect.

In one embodiment of the present invention,

The laser may be a pulsed laser, but is not limited thereto.

Hereinafter, the apparatus and process conditions used in the laser ablation process will be described in detail.

The apparatus used in the laser ablation process includes a laser oscillator for emitting a laser beam, and a focusing lens for focusing the laser beam emitted from the laser oscillator and irradiating the laser beam onto the electrode. It is preferable that the focal spot of the laser beam passing through the focusing lens touches the surface of the electrode. Here, the focus spot refers to a laser beam within a focus depth described later.

The depth of focus means the distance between two points where the radius of the focused laser spot is Wo when the minimum radius of the focused laser spot is Wo and the focusing distance of the focusing lens is f. Sufficient laser ablation is performed so that the electrode is positioned within the focus spot, which is the laser beam within the depth of focus, and the laser ablation process is incompletely performed because the amount of energy of the laser beam significantly drops when the focus spot is deviated.

The size Wo of the focus spot can be expressed by the following equation (1).

[Formula 1]

In the formula 1, λ is the laser wavelength, M ² denotes a laser-quality as a variable called beam mode parameter (Beam Mode Parameter), f is the focal length of the focusing lens, D is the laser beam entering the condenser lens .

The depth of focus can be expressed by the following equation (2), where L denotes the depth of focus.

[Formula 2]

From the relations of the above-mentioned expressions 1 and 2, the following expression 3 is derived.

[Formula 3]

If the size Wo of the focus spot is small, the energy of the laser beam is concentrated in a narrow region to facilitate the laser ablation process. If the depth of focus is long, the position of the electrode with respect to the laser beam changes, Ideally, the size Wo of the focus spot is small and the depth of focus is long, because laser ablation can be performed smoothly.

However, referring to Equation 3, the depth of focus is proportional to the size of the laser spot.

Therefore, if the size of the focal spot is small, the energy density per unit area of the laser beam can be increased. However, since the focal depth is also reduced together with the laser spot, the position of the cutting object with respect to the laser beam is changed or the surface of the cutting object is uneven The cutting object is not cut smoothly.

On the contrary, if the depth of focus is long, it becomes less sensitive when the position of the electrode to be laser ablation process is changed with respect to the laser beam or when the surface of the electrode is uneven, so that it is easy to set the position of the electrode or the focus, There is a problem that the energy density per unit area of the laser beam becomes lower than a level at which the laser ablation process can be performed because the spot size also increases with the depth of focus.

Thus, it is very important to balance the depth of focus and the size of the focus spot in the laser ablation process of the electrode, since it is impossible to make the depth of focus very long and at the same time make the size of the focus spot very small. It is also necessary to grasp what variables are important variables in ablation of the electrodes using a laser.

In another embodiment of the present invention,

The focal length of the converging lens of the laser may be 100 mm to 300 mm, but is not limited thereto.

In another embodiment of the present invention,

The pulse width of the laser is preferably from 1 ns to 300 ns, more preferably from 5 ns to 30 ns, but is not limited thereto.

If the size of the laser pulse width is larger than the numerical range, the heat transfer time of the laser to the electrode is long and the thermal effect on the periphery is large. If the laser pulse width is smaller than the numerical range, sufficient energy transfer is not performed, But it is not limited thereto.

In one embodiment of the present invention,

M ² is a variable called a beam mode parameter, which indicates the quality of the laser, with a theoretical value of 1 and a value of about 1.3. The M ² value of the laser used in the present invention is preferably as close as 1, but may be varied depending on the laser output and oscillation method. In order to reduce the size of the focal spot when the M ² value is 2 or more, the depth of focus becomes large, so that it is preferable to have a value of 1.0 to 2.0, but the present invention is not limited thereto.

In another embodiment of the present invention,

The frequency of the laser is preferably 20 kHz to 1000 kHz, more preferably 70 kHz to 500 kHz, but is not limited thereto.

If the frequency of the laser is larger than the numerical range, there is a disadvantage in that the interval between the beams is narrow and the thermal effect by the laser is large. Due to the superposition ratio between the laser beams, And the active material grains are not removed. Therefore, the frequency of the laser is preferably within the above range, but is not limited thereto.

In another embodiment of the present invention,

The speed of the laser is preferably 0.5 m / s to 5 m / s, more preferably 3 m / s to 5 m / s, but is not limited thereto.

In one embodiment of the present invention,

The size of the laser spot is preferably 18 탆 to 86 탆, more preferably 25 탆 to 60 탆, but is not limited thereto.

The size of the laser spot greatly affects the machining result on the electrode surface during laser ablation,

If the size of the laser spot is larger than the numerical range, the energy intensity of the laser is too low to perform sufficient etching. If the laser spot is smaller than the numerical range, the etching efficiency is lowered.

In another embodiment of the present invention,

The size of the laser pulse energy is preferably from 0.1 μJ to 1000 μJ, but is not limited thereto.

When the pulse energy of the laser exceeds 1000 μJ, not only the active material but also the electrode under the active material is also etched by the laser ablation process of the present invention. It is difficult to selectively etch the active material, and if the pulse energy of the laser is less than 0.1 μJ, sufficient etching is not performed and the etching efficiency is lowered.

The present invention also relates to a method of manufacturing a secondary battery, which comprises etching the electrode by the etching method.

The present invention also relates to a secondary battery comprising the electrode etched by the etching method.

Hereinafter, the present invention will be described in more detail by way of non-limiting examples. The embodiments of the present invention described below are by way of example only and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated in the claims, and moreover, includes all changes within the meaning and range of equivalency of the claims. In the following Examples and Comparative Examples, "%" and "part" representing the content are on a mass basis unless otherwise specified.

Example

Example  1. A positive electrode active material film Etching

(1) An aluminum foil was cut to form an electrode tab on one side to prepare a positive electrode plate. A positive electrode mixture was prepared by adding LiCoO ₂ as a positive electrode active material, carbon black and graphite as a conductive material, and polyvinylidene fluoride (PVdF) as a binder to a solvent N-methylpyrrolidone to prepare a positive electrode mixture. Respectively. The thus-prepared electrode coated with a cathode active material film (manufactured by LG Chemical Co., Ltd.) was heated with a hot air heater (H1600, manufactured by metabo) while maintaining a distance of 30 cm from the electrode.

 (2) A laser ablation process was performed on the cathode active material film on the surface of the heated electrode by irradiating laser (SP4 manufactured by G4) under the conditions shown in Table 1 below. And the number of times that the etching degree of the electrode was optimized was ascertained while the number of irradiation was increased under the same conditions.

The results are shown in FIG. 1 and FIG. 2, and were optimized when the laser was irradiated five times.

Example 1 Diameter of F-Setter Lens (mm) 167 Collimator (focal length = mm) 50 Pulse width (ns) 15 Power (%) 70 Frequency (kHz) 450 Laser speed (m / s) 5 Laser spot size (탆) 60 Pulse energy (μJ) 63

Example  2. Negative electrode active material membrane on the electrode surface Etching

(1) A copper foil was cut to form an electrode tab on one side to prepare a negative electrode plate. A negative electrode mixture slurry was prepared by adding artificial graphite as a negative electrode active material, carbon black as a conductive material, styrene-butadiene rubber (SBR) as a binder and carboxymethylcellulose (CMC) as an additive to distilled water as a solvent. Respectively. The electrode (LG Chemical Co., Ltd.) coated with the negative electrode active material film thus prepared was heated with a hot air (H1600, manufactured by metabo) at a distance of 30 cm from the electrode.

(2) The negative electrode active material film on the surface of the heated electrode was subjected to a laser ablation process by irradiating a laser (SP4 manufactured by G4) under the conditions shown in Table 2 below. And the number of times that the etching degree of the electrode was optimized was ascertained while the number of irradiation was increased under the same conditions.

The results are shown in Fig. 5 and Fig. 6, and were optimized when the laser was irradiated four times.

Example 2 Diameter of F-Setter Lens (mm) 167 Collimator (focal length = mm) 50 Pulse width (ns) 15 Power (%) 90 Frequency (kHz) 500 Laser speed (m / s) 3 Laser spot size (탆) 60 Pulse energy (μJ) 81

Example  3. The positive electrode active material membrane on the electrode surface Etching

The number of times that the etching degree of the electrode was optimized in the same manner was confirmed except that the step (1) of Example 1 was not performed.

The results are shown in Fig. 3 and Fig. 4, and were optimized when the laser was irradiated seven times.

Example  4. Negative electrode active material film on the electrode surface Etching

The number of times that the etching degree of the electrode was optimized in the same manner was confirmed except that the step (1) of Example 2 was not performed.

The results are shown in FIG. 7 and FIG. 8, and optimized when the laser was irradiated five times.

Comparative Example  1. A positive electrode active material film Etching

The surface of the electrode coated with the negative active material film (manufactured by LG Chemical Co., Ltd.) was notched. The metal notching was carried out by the method disclosed in Korean Patent Registration No. 1370855. [

Comparative Example  2. Negative electrode active material membrane on the electrode surface Etching

The negative active material film on the electrode surface was notched with metal.

As a result of etching the active material film according to the first to fourth embodiments, it was possible to cut the tab to be located at the etched portion of the active material film as shown in FIG. 9, and the tab position and the tab shape could be freely designed. On the other hand, in the case of Comparative Examples 1 and 2, as shown in FIG. 10, since a linear tapped portion is formed during electrode coating, the shape of the tab after the metal notching process is limited.

In addition, according to Examples 1 to 4, the degree of etching of the active material film was compared to determine a tact time (which means the maximum time of each process time, whether or not the active material film was sufficiently etched and visually confirmed and the time was measured) .

In the case of the cathode active material film, the tact time was reduced by about 28% in the case of Example 1 in which etching was performed together with the hot air as compared with Example 3 in which etching was performed in the absence of hot air.

In the case of the anode active material film, the tact time was reduced by about 20% in the case of Example 2 in which etching was performed together with the hot air as compared with Example 4 in which etching was performed in the absence of hot air.

As a result, it was found that the laser ablation process speed was improved in Examples 1 and 2 using the hot air. In other words, when the laser ablation process is performed on the active material film, the energy required for the ablation is determined. At this time, a certain energy is transferred through the heat irradiator instead of the laser, thereby reducing the amount of energy to be transferred through the laser So that the laser ablation process speed can be improved economically.

Claims (14)

A method of etching an electrode by a laser ablation process in which a part of an active material film formed on an electrode surface is removed by laser irradiation,
And heating the electrode prior to the etching. The method according to claim 1,
Wherein the active material layer is made of LiCoO ₂ , LiMn _x O ₂ x (x = 1 or 2), LiFePO ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and LiNi _{1 - x} Co _x M _y O ₂ (x = 0 to 0.2 and M = Mg, Ca, Sr, Ba and La, and y = 0.001 to 0.02) Wherein the electrode is an active material film. The method according to claim 1,
Wherein the active material film is a negative electrode active material film comprising at least one selected from the group consisting of graphite, a silicon-based compound, a germanium-containing material, and a tin-containing material. The method according to claim 1,
Wherein the heating step is performed by at least one selected from the group consisting of a heat gun, a RF induction unit, an induction infrared (IR) lamp, and a hot plate. The method according to claim 1,
Characterized in that the laser is a pulsed laser. The method according to claim 1,
Wherein the focusing distance of the converging lens of the laser is 100 mm to 300 mm. The method according to claim 1,
Wherein the pulse width of the laser is from 1 ns to 300 ns. The method according to claim 1,
Wherein the value of the beam mode parameter (M ² ), which is a variable indicative of the quality of the laser, is 1 to 2.0. The method according to claim 1,
Wherein the frequency of the laser is 20 kHz to 1000 kHz. Electrode etching method. The method according to claim 1,
Wherein the speed of the laser is from 0.5 m / s to 5 m / s. The method according to claim 1,
Characterized in that the size of the laser spot is between 18 [mu] m and 86 [mu] m. The method according to claim 1,
Wherein the laser pulse energy has a magnitude in the range of 0.1 μJ to 1000 μJ. A method of manufacturing a secondary battery, comprising etching the electrode by an etching method of an electrode according to any one of claims 1 to 12. A secondary battery comprising an electrode etched by an electrode etching method according to any one of claims 1 to 12.

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