KR101850180B1 - Secondary Battery Comprising Current Collector with Through Hole - Google Patents

Abstract

The present invention relates to a positive electrode current collector comprising a positive electrode coated with a positive electrode mixture layer on one surface or both surfaces thereof, a negative electrode coated with a negative electrode mixture layer on one or both surfaces of the negative electrode collector, and a separator interposed between the positive and negative electrodes (Ii) an electrode active material, and (ii) an electrode active material and a binder, wherein the electrode active material and the electrode active material are mixed with each other. Or (iii) a mixture of an electrode active material and a conductive material is filled.

Description

[0001] The present invention relates to a secondary battery including a current collector having through holes,

The present invention relates to a secondary battery comprising a current collector in which a through hole is perforated, the secondary battery comprising: a plurality of through holes formed in an electrode current collector coated with an electrode active material; and an electrode active material or a mixture of an electrode active material and a binder This is a technique for providing a secondary battery with increased capacity by filling a mixture of an electrode active material and a conductive material.

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, Batteries have been commercialized and widely used.

On the other hand, as time passes, consumers require a larger amount of energy. In order to make a battery having a high energy density, electrodes must be made thicker, more specifically, the thickness of the mixture layer applied to the current collector . However, if the thickness of the electrode assembly layer is increased as described above, there arises a problem that electrolyte wetting of the electrode is not sufficiently performed.

Specifically, the electrolyte does not have a high affinity for the electrode material mixture components, and when the volume of the mixture layer is increased, the flow path of the electrolytic solution becomes longer, so that the penetration of the electrolyte solution is not easy, It is difficult to do. Further, if the electrolyte does not sufficiently penetrate into the electrode, the movement of the ions is slowed down, and the electrode reaction can not be smoothly performed, resulting in a deterioration of the efficiency of the battery.

Generally, an electrode of a secondary battery is composed of a current collector and an electrode mixture coated on the surface thereof. In order to obtain the performance of a desired battery, a method of changing the shape of the electrode or adjusting the composition of the active material has been actively studied .

As a method of changing the shape of an electrode in the past, there has been known a method of forming a pattern on a current collector by forming an opening hole by applying and etching a pattern forming ink or the like on a current collector. However, these methods are applied selectively to the collector surface by spraying, pressing, or the like in the application of the active material, and are divided into a coated portion and a non-coated portion according to a certain pattern Thereby exposing a part of the current collector. Such an active material patterning method effectively buffers the volume change during charging and discharging, but the loading amount of the active material is greatly reduced due to the presence of the non-coated portion, which leads to a problem that the efficiency of the battery is inevitably reduced.

Therefore, there is a high demand for the development of a secondary battery which can increase the energy density and attain sufficient wetting characteristics due to easy penetration of the electrolyte solution, so that the electrode reaction can be actively performed.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments. As described later, a through hole is formed in the electrode current collector, and the electrode active material, a mixture of the electrode active material and the binder or the electrode active material, When the electrode mixture is applied after filling the ash mixture, the amount of the active material to be applied is increased, so that the capacity of the secondary battery can be increased.

Since the lithium ion of the positive electrode active material can move through the through hole, not only the utilization ratio of the positive electrode active material is increased but also the movement of the electrolyte through the through hole is possible, so that the wettability to the electrolyte is improved have.

Therefore, in the secondary battery according to the present invention,

A positive electrode coated with a positive electrode mixture layer on one surface or both surfaces of a positive electrode collector, a negative electrode coated with a negative electrode mixture layer on one or both surfaces of a negative electrode collector, and a separator interposed between the positive and negative electrodes, Include;

At least one through-hole communicating with the upper surface and the lower surface of the current collector is formed in the current collectors;

(Ii) an electrode active material and a binder; or (iii) a mixture of an electrode active material and a conductive material is filled in the inner hollow of the through-hole.

Therefore, the secondary battery according to the present invention has a through-hole formed in the electrode current collector. In order to increase the loading amount of the electrode active material, which is a component capable of increasing the capacity of the battery, the electrode active material, A mixture of an active material and a binder, or a mixture of an electrode active material and a conductive material, and then applying an electrode mixture. Specifically, a mixture of an electrode active material, a mixture of an electrode active material and a binder, or a mixture of an electrode active material and a conductive material is placed on the electrode current collector, and then the electrode active material or the like is swept and moved in a predetermined direction, The electrode active material and the like are not located. However, the inner pores of the through holes are filled with the electrode active material, and the electrode mixture is coated on the electrode current collector having the above-described structure to complete the electrode.

Since the amount of the active material applied to the electrode current collector increases due to the amount of the active material interposed in the through hole, it is possible to solve the problems caused by the capacity reduction in the related art, The bonding force between the active materials applied to both surfaces of the current collector is improved.

Also, since the electrolyte can easily move into the electrode assembly through the plurality of through-holes formed in the electrode assembly, the impregnability of the electrode with respect to the electrolyte can be enhanced. Therefore, even if the area of the battery is increased, the wetting can be made uniform and the process time can be shortened, so that the safety and life characteristics of the battery can be greatly improved. Moreover, such high impregnation helps to maintain excellent rate characteristics even under high rate charge / discharge conditions.

In the secondary battery according to the present invention, the current collectors in which the through-holes are formed are not particularly limited as long as they have conductivity without causing chemical changes in the battery, and examples thereof include aluminum, aluminum alloy, nickel, , Stainless steel, nickel, titanium, sintered carbon, or a metal or alloy thereof selected from the group consisting of copper and stainless steel, but may preferably be in the form of aluminum foil or copper foil.

In one specific example, the thickness of the current collectors may be 10 micrometers to 30 micrometers, and more specifically 10 micrometers to 20 micrometers.

When the current collectors are thinner than 10 micrometers, it is difficult to increase the amount of the active material as much as desired. When the current collectors are thicker than 30 micrometers, the total thickness of the electrodes increases, Which is undesirable.

In one specific example, the electrode assembly is not particularly limited as long as it has a structure composed of at least one unit composed of an anode, a cathode, and a separator from the battery case without deteriorating the performance of the battery cell. Specifically, A stacked electrode assembly in which at least one positive electrode plate and at least one negative electrode plate are laminated with a separation membrane interposed therebetween or stacked unit cells including a positive electrode plate and a negative electrode plate are stacked on a separating sheet Stacked electrode assembly in which stacked unit cells including a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween.

The secondary battery according to the present invention has a structure in which a mixture of an electrode active material, a mixture of an electrode active material and a binder or an electrode active material and a conductive material is filled in a through hole formed in an electrode current collector, Although it is not particularly limited, it may be in the form of a circle, an ellipse, a polygon, or a slit in a planar shape, and may be slit-shaped, considering the amount of the active material to be interposed and the strength of the current collector.

In one specific example, the current collectors are formed with two or more through-holes, and the through-holes may all have the same shape when designing a manufacturing process for forming a through-hole in the current collector.

In one other specific example, the current collectors may have two or more through-holes, and the through-holes may have two or more different shapes. For example, a circular through-hole, an elliptical through-hole, or a polygonal through-hole is located at a position on a straight line on the top, bottom, right, left, or diagonal of the through-hole of a slit type. Conversely, a straight through- And the slit-shaped through-hole may be located at a position on the diagonal line. With such a shape, it is possible not only to increase the amount of the active material interposed in the through-hole but also to prevent the strength of the current collector from being lowered.

In the secondary battery according to the present invention, in the current collectors in which two or more through-holes are perforated, the total area of the through-holes may be 1% to 30% of the total area of the upper or lower surface of the current collector More specifically from 5% to 30%, and more particularly from 10% to 30%. If the sum of the areas of the through-holes is less than 1% based on the surface area of the upper or lower surface of the collector, it is difficult to achieve the purpose of increasing the loading amount of the active material. It is not preferable because the active material can be easily dropped off.

The diameter of the circular through-hole, the diameter of the elliptical through-hole or the polygonal through-hole may be 0.1 mm to 5 mm, and the diameter of the through- More specifically, from 1 mm to 3 mm, and the length of the slit-shaped through-hole may be from 1 mm to 10 mm, and more specifically, from 2 mm to 8 mm And more specifically from 4 mm to 7 mm.

When the size of the through-holes is too small, the effect of improving the impregnability of the electrode due to the increase of the utilization ratio of the active material due to the movement of lithium ions and the movement of the electrolyte is small, If the size of the through-holes is too large, the strength of the current collector may be weakened.

The secondary battery according to the present invention may have a shape in which a positive electrode material mixture layer or a negative electrode material mixture layer is coated on the current collector in a state where an electrode active material or the like is contained in a current collector having a through- The layer may be composed of an electrode mixture containing the electrode active material as well as a binder and a conductive agent, and if necessary, a filler may be further added to the mixture.

The binder is a component that assists in binding of the active material to the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30 wt% based on the total weight of the electrode material mixture containing the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The filler is optionally used as a component for suppressing the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

In one specific example, the electrode active material, the electrode active material, the binder or the electrode active material and the conductive material may be filled in the inner hollow of the through-hole formed in the current collector. However, in order to increase the capacity of the battery, Since it is necessary to increase the amount, it is preferable that the electrode active material is filled.

On the other hand, in a lithium secondary battery, in general, the negative electrode active material may have a relatively low efficiency as compared with the positive electrode active material, and even when the theoretical capacity of the negative electrode active material is equal to that of the positive electrode active material, The capacity is lowered than the operating efficiency of the cathode active material. It is preferable that the thickness of the anode mixture layer is formed thicker than the thickness of the anode mixture layer. Since the capacity of the cathode is required to be further increased as compared with that of the anode, the total area of the through-holes formed in the anode current collector can be formed relatively larger than the total area of the through-holes formed in the anode current collector. Specifically, the total area of the through-holes formed in the anode current collector may be from 101% to 200%, more specifically from 110% to 180% of the total area of the through-holes formed in the anode current collector, % To 160%.

When the total area of the through-holes formed in the anode current collector is less than 101% of the total area of the through-holes formed in the anode current collector, the anode may be unnecessarily wasted due to the cathode having a relatively low operating efficiency, The collector of the negative electrode may be relatively weakly manufactured, and the working efficiency of the anode may not be balanced with the efficiency of the anode, which may waste the cathode.

The present invention also provides a secondary battery in which the electrode assembly is sealed inside a battery case together with an electrolytic solution. The secondary battery can be used not only in a battery cell used as a power source of a small device, but also in a high- A battery pack including a plurality of battery cells used as a power source for a medium and large-sized device requiring long cycle characteristics and high rate characteristics, and a unit cell for a middle- or large-sized device including the battery pack as a power source.

Preferred examples of the middle- or large-sized device include a mobile device, a wearable device, a power tool powered by the battery module, An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; But is not limited to, a system for power storage.

As described above, the secondary battery according to the present invention is characterized in that a through hole is formed in the current collector of the electrode, the electrode active material, a mixture of the electrode active material and the binder, or a mixture of the electrode active material and the conductive material is filled in the through hole, The amount of the active material to be applied can be increased, and thus a secondary battery having an increased capacity can be manufactured.

In addition, since the lithium ion of the positive electrode active material can move through the through hole, not only the utilization rate of the electrode active material is increased but also the movement of the electrolyte through the through hole is possible, so that the wettability to the electrolyte is improved have.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of current collectors formed with various types of through-holes as an embodiment of the present invention; FIG.
FIG. 2 is a plan view schematically illustrating a current collector in which two or more through holes having different shapes are formed as another embodiment of the present invention; FIG.
3 is a plan view schematically showing a state in which an active material is contained in a through hole formed in a current collector;
4 is a cross-sectional view taken along line A-A 'of Fig. 3;
5 is a cross-sectional view of B-B 'of Fig. 3; And
Fig. 6 is a schematic view of the current collector of Fig. 4 coated with an electrode mixture.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIG. 1 schematically shows through-holes formed in a current collector according to an embodiment of the present invention.

1, the through-holes 121, 131, 141, and 151 formed in the current collectors 120, 130, 140 and 150 include circular through holes 121, elliptical through holes 131, 141 or slit-shaped through-hole 151. The through-holes formed in any one of the current collectors 120, 130, 140, and 150 have the same shape. On the other hand, the sum of the areas of the through-holes may be selected within a range in which the strength is not too weak depending on the thickness of the current collector or the material of the current collector. The total area of the through- 30%. ≪ / RTI >

The diameter d1 of the circular through hole 121 and the diameter of the elliptical through hole 131 may be selected in consideration of the capacity of the battery. The long diameter d2 of the through hole 141 or the long diameter d3 of the polygonal through hole 141 may be in the range of 0.1 mm to 5 mm and the length d4 of the slit- Lt; / RTI >

Fig. 2 schematically shows a current collector in which two or more through-holes having different shapes are formed as another embodiment of the present invention.

Referring to FIG. 2, through-holes are formed on the current collector 210 in two different shapes, each having a circular through-hole 211 and a polygonal through-hole 212. The circular through holes 211 and the polygonal through holes 212 are formed at equal intervals in the longitudinal direction L of the current collector 210 and are formed on the cross section of the current collector 210 in the width direction W On the cross section in the longitudinal direction, the through holes of different shapes are positioned so as not to overlap each other.

In the current collector 210, a row of circular through holes 211 and a row of polygonal through holes 212 are alternately formed.

In another embodiment, the current collector 310 is formed with two different through-holes, each of which is formed of a slit-shaped through-hole 311 and a circular through-hole 312. The slit-shaped through-holes 311 and the circular through-holes 312 are formed at equal intervals in the longitudinal direction L of the current collector 310, Or on the cross section in the longitudinal direction, the through holes of different shapes are not overlapped. By arranging the through-holes having different shapes in different rows in this way, not only the capacity increase of the battery but also the strength of the current collector can be prevented from being lowered.

3 schematically shows a state in which the active material is contained in the through hole formed in the current collector. Fig. 4 is a sectional view taken along the line A-A 'in Fig. 3, and Fig. 5 is a sectional view taken along the line B- Sectional views schematically.

3 to 5, a slit-shaped through hole 411 and a circular through hole 412 are formed in the current collector 410 having a thickness D of 10 to 30 μm, and the through holes 411 And 412, electrode active materials 421 and 422 are included. Specifically, by positioning the electrode active material on the electrode current collector, and by sweeping and moving the electrode active material in a predetermined direction, the electrode active material or the like is not positioned in the current collector portion where the through hole is not formed. However, The electrode active material or the like is filled.

As described above, in one specific example, the effect of increasing the capacity of the battery can be exhibited by using the current collector having the electrode active material interposed in the pores of the through-holes.

In another specific example, when the mixture of the electrode active material and the binder is interposed in the through-holes 411 and 412, the effect of increasing the bonding force between the electrode mixture material applied to the upper surface and the lower surface of the current collector .

In another specific example, when the mixture of the electrode active material and the conductive material is interposed in the through-holes 411 and 412, the utilization ratio of the active material can be increased by increasing the ionic conductivity through the through-hole.

5, which is a cut surface on the slit-shaped through-holes 411 and FIG. 5, which is a cut surface on the circular through holes 412, only the through-holes having the same shape are arranged on the same row, And the through holes having the same shape as shown in FIG. 5 are spaced apart from each other by a diameter, a long diameter, or a length of the through holes having different shapes. Therefore, the gap between the through-holes is not formed too narrowly, and only a single size and kind of through-holes are formed on the cut surface.

6 is a schematic view showing a state in which the electrode mixture is applied to the current collector of FIG.

6, a through hole 411 is formed in the electrode current collector 410 and a mixture 421 of the electrode active material, a mixture of the electrode active material and the binder or the electrode active material and the conductive material is formed in the through holes 411, Respectively. The electrode assembly layer 430 is applied to the top and bottom surfaces of the electrode current collector 410 having such a structure, thereby increasing the capacity of the battery or increasing the bonding strength between the compound layers. The total area of the through holes formed in the anode current collector is relatively larger than the total area of the through holes formed in the anode current collector in relation to the total area of the through holes formed in the current collector, Specifically, the total area of the through-holes formed in the anode current collector may be set to 101% to 200% of the total area of the through-holes formed in the anode current collector.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims (16)

A positive electrode coated with a positive electrode mixture layer on one surface or both surfaces of a positive electrode collector, a negative electrode coated with a negative electrode mixture layer on one or both surfaces of a negative electrode collector, and a separator interposed between the positive and negative electrodes, Include;
At least one through-hole communicating with the upper surface and the lower surface of the current collector is formed in the current collectors;
(Ii) a mixture of an electrode active material and a binder, or (iii) a mixture of an electrode active material and a conductive material, the inner hollow of the through-hole being filled with (i) an electrode active material,
Wherein the shape of the through-hole is a plane, circular, elliptical, polygonal or slit shape,
Wherein the diameter of the circular through-hole in the through-hole, the diameter of the elliptical through-hole or polygonal through-hole is 0.1 mm to 5 mm, and the length of the slit-shaped through-hole is 1 mm to 10 mm. The secondary battery according to claim 1, wherein the current collectors are in the form of aluminum foil or copper foil. The secondary battery according to claim 1, wherein the current collectors have a thickness of 10 micrometers to 30 micrometers. The secondary battery according to claim 1, wherein the electrode assembly is of a jelly-roll type, a stack type, a stack-folding type, or a lamination-stack type. delete The secondary battery according to claim 1, wherein the current collectors are formed with at least two through-holes, and the through-holes are formed in the same shape. The secondary battery according to claim 1, wherein the current collectors are formed with at least two through-holes, and the through-holes are at least two different shapes. [Claim 2] The method according to claim 1, wherein the current collectors are formed with at least two through holes, and the total area of the through holes is 1% to 30% based on the surface area of the top or bottom surface of the current collector. Secondary battery. delete The secondary battery according to claim 1, wherein the positive electrode material mixture layer and the negative electrode material mixture layer are made of an electrode material mixture comprising an electrode active material, a binder and a conductive agent. The secondary battery according to claim 1, wherein an electrode active material is filled in the inner hollow of the through-hole. The secondary battery according to claim 1, wherein the total area of the through-holes formed in the negative electrode collector is relatively larger than the total area of the through-holes formed in the positive electrode collector. 13. The secondary battery according to claim 12, wherein the total area of the through-holes formed in the negative electrode current collector is from 101% to 200% of the total area of the through-holes formed in the positive electrode collector. A battery pack comprising a secondary battery according to claim 1 as a unit cell. A device comprising the battery pack according to claim 14 as a power source. 16. The apparatus of claim 15, wherein the device comprises a mobile device, a wearable device, a power tool powered by the battery module, An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart, or a system for power storage.

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