KR101519587B1 - Electrode for secondary battery and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an electrode body for a secondary battery, comprising a current collector and an active material coated on at least one surface of the current collector, wherein at least one surface of the current collector includes an uneven layer formed by sandblasting.

Sand blasting, collector, active material, electrode body, secondary battery

Description

TECHNICAL FIELD [0001] The present invention relates to an electrode body for a secondary battery, and a secondary battery including the same. BACKGROUND ART [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode body for a secondary battery and a secondary battery using the same. More particularly, the present invention relates to an electrode body for a secondary battery in which a surface of the current collector is subjected to a sandblasting treatment.

Typically, a secondary battery such as a lithium polymer / ion secondary battery includes a positive electrode plate having a positive electrode active material layer coated on a predetermined region on at least one side thereof, a negative electrode plate having a negative electrode active material layer coated on a predetermined region of at least one surface thereof, and a negative electrode plate interposed between the positive electrode plate and the negative electrode plate An electrode assembly including a separator for preventing short-circuiting between the positive electrode plate and the negative electrode plate and allowing movement of lithium ions, and a case for housing the electrolyte solution together with the electrode assembly.

The positive electrode plate and the negative electrode plate each include an electrode current collector and an electrode active material layer, and the electrode active material layer is prepared in a slurry state in which a conductive material and a binder are mixed with an organic solvent and coated on the electrode current collector. Therefore, the positive electrode active material and the negative electrode active material are attached to the current collector of the electrode by the binder contained therein to form the electrode active material layer.

On the other hand, as the electronic devices in which the secondary batteries are used have become more sophisticated and higher in performance, measures for improving the performance of the secondary battery itself have been proposed. In the case of a lithium ion secondary battery, in general, in order to improve the performance of a battery, it is possible to increase the amount of the cathode material of the cobalt series or to increase the surface area of the foil portion in contact with the active material. However, in the case of the former, there is a limit in increasing the amount of the cathode material, and in the latter case, the mechanical strength of the electrode body may be reduced.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an electrode body for a secondary battery which can increase the surface area of the current collector, And to provide a secondary battery using the same.

In order to attain the above object, according to a preferred embodiment of the present invention, there is provided an electrode body for a secondary battery comprising a current collector and an active material coated on at least one surface of the current collector, And an uneven layer formed by sandblasting.

Preferably, the current collector is a bipolar foil made of aluminum having a thickness of about 20 micrometers.

Preferably, the current collector is a cathode foil consisting of copper with a thickness of about 10 micrometers.

Preferably, the current collector is reduced in thickness by about 2 micrometers by the sandblasting. Preferably, the current collector has a tab to which no active material is applied, and the uneven layer is not formed in the tab.

According to another aspect of the present invention, there is provided a method of manufacturing an electrode body for a secondary battery, comprising the steps of: (a) preparing a current collector; (b) (C) coating the active material on the uneven layer.

According to the present invention, there is an effect that the surface area of the electrode current collector can be increased by forming an uneven layer by sand blasting on the surface of the collector of the electrode body and coating the active material on the uneven layer. In addition, since the surface of the current collector is pressed by the sandblaster using sand, the strength of the current collector can be increased.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

Hereinafter, an electrode body for a secondary battery according to a preferred embodiment of the present invention, a manufacturing method thereof, and a secondary battery using such an electrode body will be described with reference to the accompanying drawings.

1 is a cross-sectional view schematically showing an electrode body for a secondary battery according to a preferred embodiment of the present invention.

1, the electrode assembly 10 for a secondary battery according to the present invention includes a current collector 12 and an active material 14 applied to one surface of the current collector 12, And an uneven layer 16 formed by a sandblasting method. The contact area between the active material 14 and the current collector 12 increases and the active material 14 is inserted into the groove between the concavo-convex layer 16 and the active material 14 is excessively bulged, 12 from being removed from the surface.

In a preferred embodiment of the present invention, the electrode body 10 is a concept including a cathode electrode body or a cathode electrode body. The current collector 12 and the active material 14 used in accordance with the positive electrode and the negative electrode may be selected, respectively. That is, various metals may be used for the current collector 12, and the uneven layer 16 of the current collector 12 is formed by a sand blasting technique known in the art. The uneven layer 16 refers to a portion of the current collector 12 sandblasted on the current collector 12.

In a preferred embodiment, the sandblasting process is performed by spraying sand having a diameter of about 50 탆 into the collector 12 region of 10 x 10 cm ² for about 1 to 5 minutes at an injection pressure of about 6 kgf / cm ² The surface of the current collector 12 is lightly washed with washing water such as distilled water, and the water on the surface of the current collector 12 is removed with compressed air, followed by drying in an oven for about 1 hour.

As described above, the current collector 12 may include a positive electrode collector and a negative electrode collector, and the positive electrode collector is made of aluminum (Al) and the negative collector is made of copper (Cu). Therefore, the process of sandblasting the current collector 12 can be applied differently depending on the metal material used.

The concavo-convex layer 16 formed on the surface of the current collector 12 by the sand blasting process is sandwiched by sandblasting to the surface of the current collector 12 at a high pressure, The surface of the current collector 12 is pressed by the sand and the surface of the current collector 12 is pressed. For example, when the total thickness of the cathode current collector 12 made of the anode foil is about 20 占 퐉, it is preferable to reduce it by about 2 占 퐉. Also, if the injection time is kept long or the injection pressure is increased in the sandblasting process, the decrease in thickness will increase. If the thickness of the unevenness layer 16 is larger than 2 탆, the mechanical strength of the current collector 12 becomes weak, and the current collector 12 may be torn during the production of the lithium secondary battery.

On the other hand, when the negative electrode current collector is sandblasted, it is possible to form the uneven layer on the surface of the negative electrode collector of the copper foil by using the negative electrode foil composed of copper having a thickness of about 10 mu m, Will understand.

In a preferred embodiment, the positive electrode collector or the negative electrode collector is generally manufactured to a thickness of 3 to 500 mu m. It is also preferable that the current collector 12 has a capacity of 120 cd / cm 2 or less. The surface area of the current collector 12 on which the uneven layer 16 is formed by the sand blasting is increased due to the irregular bending of the surface thereof and therefore can be expressed by using the capacity per unit area in order to indicate the degree of unevenness of the current collector 12 . If the degree of irregularity exceeds the above-mentioned range, the mechanical strength of the current collector 12 becomes weak, and the current collector may be broken during manufacturing of the lithium secondary battery.

2, the electrode body 10 generally includes a tab 18 to which no active material is applied. Therefore, in the sandblasting step, the electrode body 10 is formed in the current collector 12 The uneven layer 16 is not formed on the tab 18.

The average particle diameter of the active material is 3 mu m or less, more preferably 1 mu m or less. The active material includes a cathode active material or an anode active material. In particular, since lithium iron phosphate has characteristics of low electrical conductivity, it is possible to increase the contact area between the current collector and the active material by making the particle size of the active material small, and improve the output and high temperature storage performance / cycle characteristics by securing the binding power.

In addition, when the particle size of the active material is reduced, sufficient output characteristics are obtained without coating the conductive material on the current collector. Therefore, there is a process advantage that the step of coating the active material on the current collector can be omitted.

The cathode active material is a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound represented by the formula Li _{1 + x} Mn _{2 -x} O ₄ (where x = 0 To 0.33), lithium manganese oxide lithium copper oxide (Li ₂ CuO ₂ ) such as LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; _{LiV 3 O 8, LiFe 3 O} 4, V 2 O 5, Cu 2 V 2 O 7 , such as vanadium oxide formula LiNi _1-x MxO ₂ (wherein, in the M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and, x = 0.01 ~ 0.3 Im) Ni site type lithium nickel oxide formula LiMn _2-x M _x O _2, which is represented by (wherein, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, Ni, Cu or Zn) LiMn ₂ O ₄ disulfide substituted with alkaline earth metal ions And a compound Fe ₂ (MoO ₄ ) ₃ , but the present invention is not limited to these.

Particularly, the positive electrode active material is preferably an active material having lithium metal phosphate (LiMPO ₄ , where M = Co, Ni, Fe, Cr, Zn, Cu or Ta) and an olivine structure, more preferably lithium iron phosphate. Lithium iron phosphate has an excellent thermal stability as compared with other cathode active materials, and thus has an advantage of improving the safety of a lithium ion battery.

However, in the case of lithium iron phosphate, there is a fear that the output characteristic and the rate characteristic may be deteriorated due to the characteristic having low electric conductivity. In order to solve this problem, it is necessary to manufacture a small particle size of the active material. In addition, according to the conventional technique, the contact area between the collector and the active material is widened by coating the carbon material on the current collector first and then coating the active material thereon. To improve output and high temperature storage performance / cycle characteristics.

However, according to the present embodiment, as described above, the use of the current collector 12 in which the concavo-convex layer 16 is formed without the carbon coating reduces the complication and cost of performing the coating two times, Storage performance / cycle characteristics can be ensured.

Examples of the negative electrode active material include natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, and the like. Examples of the negative electrode active material used in the conventional lithium secondary battery include, A metal such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt and Ti which can be alloyed with lithium such as carbon and graphite material such as fullerene and activated carbon, Metals and their compounds and complex compound lithium-containing nitrides of carbon and graphite materials, and the like.

In the preferred embodiment, the electrode body 10 may use a conductive material to improve the conductivity. Such a conductive material is a material having electrical conductivity without causing chemical changes in the battery, and is preferably made of graphite carbon black such as natural graphite or artificial graphite, carbon black such as acetylene black, ketjen black, channel black, funnel black, lamp black, Conductive fibers such as carbon fibers and metal fibers, metal powders such as aluminum and nickel powders, conductive metal oxides such as conductive whiskey titanium oxide such as zinc oxide and potassium titanate, and conductive polymers such as polyphenylene derivatives.

The manufacturing method of the electrode body 10 according to the preferred embodiment of the present invention can be generally manufactured by using techniques known in the art. For example, the material including the active material and the binder may be molded into a predetermined shape, and the surface of the current collector 12 made of aluminum foil, mesh, or the like is sandblasted to form the uneven layer 16 To the surface of the substrate. More specifically, an electrode material composition is prepared and directly coated on the uneven layer 16 of the aluminum foil or the mesh current collector 12, or cast on a separate support, and the positive electrode active material film, Or the uneven layer 16 of the mesh current collector.

In addition, the lithium secondary battery according to the preferred embodiment of the present invention includes the electrode body 10 described above. For example, a lithium secondary battery can be produced by alternately stacking a positive electrode member and a negative electrode member with a polyethylene separator or the like in a battery case together with an electrolyte solution. In addition, the lithium secondary battery according to the preferred embodiment can be manufactured using conventional techniques known in the art, and is not particularly limited.

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of the separator and electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a rectangular coin shape, a pouch type, Depending on the size, it can be divided into bulk type and thin type. The structure and manufacturing method of such a battery are well known in the art, and a detailed description thereof will be omitted.

( Example 1)

Aluminum was used for the positive electrode collector, and copper was used for the negative electrode collector, and each collector was sandblasted to form a concavo-convex layer. The capacity per unit area of the current collector was about 108 ㎌ / cm 2. A cathode active material (lithium nickel phosphate) and an anode active material having an average particle diameter of 1 占 퐉 or less were applied to respective anode and anode current collectors to a thickness of about 15 占 퐉, followed by drying and rolling to prepare anode and cathode electrode bodies, respectively. The drying temperature was 140 占 폚.

(Example 2)

Electrode bodies were prepared in the same manner as in Example 1 except that the cathode active material and the anode active material each having an average particle diameter of 3 μm were used.

(Example 3)

An electrode body was prepared in the same manner as in Example 1 except that lithium iron phosphate (LiFePO ₄ ) having an average particle diameter of 1 탆 was used as the cathode active material.

(Comparative Example 1)

An electrode body was prepared in the same manner as in Example 1, except that a collector not sandblasted was used.

(Comparative Example 2)

An electrode body was manufactured in the same manner as in Example 1, except that an average particle size of 6 mu m was used as an active material.

(Experimental Example)

A lithium rechargeable battery was produced from the electrode bodies of the examples and comparative examples, and the initial output experiment and the capacity measurement experiment were performed as follows.

(1) Method of measuring the capacity

- Charging (CCCV mode): After charging to 4.2V at 1C (4Ah), the voltage was maintained at 4.2V, and when the current dropped to 2% of the 1C capacity, it was considered to be charged.

- Discharge (CC mode): When the voltage drops to 2.5V at 1C, discharge is considered to be completed.

- The rest time between charges / discharges was 20 minutes, and discharge capacity was defined as cell capacity after repeating charge / discharge 3 times.

(2) Method of measuring resistance and output

- The capacity of the cell obtained by the same method as the above capacity measurement method was made SOC50, and a current of about 10C or more was allowed to flow for 10 seconds. The width of the voltage drop was measured to calculate the cell resistance. (R =? V / I)

- When the maximum current value reaching the lower limit of the voltage for 10 seconds is obtained by using the obtained resistance value, the output value is calculated as follows. (P = I _max x V _min or P = I _max x V _max )

The results are shown in Tables 1 and 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Initial output (mAh / g) 155 128 175 100 100

Time (hr) Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2
Percentage of Capacity (%) 0 100 100 100 100 100 One 97 97 98 96 95 2 95 94 97 92 91 3 94 91 97 87 87
Rate of resistance increase (%) 0 100 100 100 100 100 One 102 105 100 109 109 2 103 108 100 118 118 3 105 113 102 130 128

The initial capacities of the examples and comparative examples were 4.2 Ah.

As shown in the above table, the performance of Examples 1 to 3 was superior to that of Comparative Examples in terms of the ratio of capacity and the rate of resistance increase.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited thereto. And various modifications and variations are possible within the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to further the understanding of the technical idea of the invention, Should not be construed to be limited to such matters.

1 is a cross-sectional view schematically showing an electrode body for a secondary battery according to a preferred embodiment of the present invention.

2 is a plan view of an electrode body for a secondary battery according to a preferred embodiment of the present invention.

Claims (8)

1. An electrode body for a secondary battery comprising a current collector made of aluminum foil and an active material coated on at least one side of the current collector, At least one surface of the current collector includes a concavo-convex layer formed by sand blasting and has a capacity of 120 cd / cm 2 or less, Wherein the active material is lithium iron phosphate having an average diameter of not more than 1 mu m and having no carbon coating on its surface. delete delete The method according to claim 1, Wherein the current collector is reduced in thickness by 2 micrometers by the sand blasting. The method according to claim 1, Wherein the current collector has a tab to which no active material is applied, and the uneven layer is not formed in the tab. (a) preparing a current collector made of aluminum foil (b) forming an uneven layer having a capacitance of 120 cd / cm 2 or less on at least one surface of the current collector by sandblasting; And (c) coating an active material composed of lithium iron phosphate on the surface of the concavo-convex layer with an average diameter of not more than 1 mu m and having no carbon coating on the surface thereof. delete A secondary battery comprising an electrode body according to any one of claims 1, 4 and 5.

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