KR101442856B1 - Large-scale secondary battery characterized by wettability of electrolyte - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a secondary battery having a high energy density and an improved electrolyte wettability of a large-area secondary battery. More particularly, the present invention relates to an electrode comprising an electrode slurry layer formed by applying an electrode slurry to a current collector; And stacked / folded cells comprising an electrode assembly in which a separator and a separator are alternately laminated, wherein the electrode comprises an electrolyte flow path. Since the secondary battery according to the present invention has the electrolyte flow path formed therein, unlike the conventional battery, penetration of the electrolyte solution proceeds smoothly, and thus it can be widely applied to the development of a secondary battery having a large-area high-density energy.

Collector, electrode slurry, separator, electrode assembly, stack / folding cell, electrolyte, oil, large area battery

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a secondary battery having improved electrolyte wettability,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery having a high energy density and, more particularly, to a secondary battery having improved electrolyte wettability of a large-area secondary battery.

Recently, a mobile energy source is required for various mobile and multi-contents use. Lithium rechargeable batteries have been used to meet these demands, and over time, consumers require a greater amount of energy.

However, at present, the energy density of the battery is limited. In order to increase the energy density of the battery, it is necessary to increase the loading amount of the electrode while reducing the volume and weight of other other parts.

Therefore, in order to make a battery having a high energy density, the electrode must be made thicker, more specifically, the thickness of the mixture layer applied to the current collector of the electrode must be increased. Further, in order to prevent an increase in the volume of the battery due to an increase in the thickness of the electrode, there is a need for a technique for further increasing the energy density of the final cell while reducing the number of stacks. However, when the thickness of the electrode is increased, various problems occur.

One of the biggest problems is that the electrode is not sufficiently wetted with electrolyte. In general, the electrolyte does not have high affinity for the electrode material mixture components, and when the volume of the mixture layer is increased, the flow path of the electrolyte solution becomes longer, so that the penetration of the electrolyte solution is not easy. it's difficult. 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.

On the other hand, the electrode has a problem that the volume of the electrode is changed by inserting / desorbing ions during charging / discharging, thereby deteriorating the performance of the battery.

Various studies have been carried out to solve these problems, but more effective measures have been demanded.

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, a method of forming a pattern on a current collector is known (refer to Korean Patent No. 0359615, No. 0359613, No. 0343793, No. 2001-0110524). This method is a method of forming an opening hole by applying a pattern forming ink or the like to a current collector using a roller and etching. However, since the above method forms fine grooves in the current collector and does not form a flow path for penetration of the electrolyte solution, a great effect can not be expected to improve the wettability of the electrolyte solution to the electrode.

In addition, a method of forming a through-hole having a predetermined pattern in the current collector is disclosed (see Japanese Patent Application Laid-Open Nos. 2000-294249 and 2002-184411). In this case, In other words, since a large hole is formed through both sides of the collector, the ion conductivity of the active material is good, but a large portion of the collector is lost, so that it is difficult to apply to a high density energy cell.

There is known a technique in which an active material is applied and patterned on a current collector without patterning the current collector (see Japanese Patent Application Nos. 3590220, 3528855, 2005-190787, 2005-011657 , 2004-127561, 2004-103474, 2001-257001). These methods are a method of selectively applying the active material on the current collector surface by spraying, pressing, or the like, and a part of the current collector is exposed by dividing the coated part and the non-coated part according to a certain pattern. 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.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art and the technical problems required from the past.

That is, it is an object of the present invention to provide a method of manufacturing a secondary battery, in which the state of an electrode slurry layer containing an electrode active material is changed during manufacture of an electrode of a secondary battery, Which can effectively solve the problems of the secondary battery.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art,

An electrode slurry layer formed by applying an electrode slurry to the current collector; And an electrode assembly formed by alternately stacking separators, wherein the stack /

Wherein the electrode includes an electrolyte flow path. The present invention also provides a large area stack / folding type battery.

Also, the present invention provides a large area stack / folding type battery, wherein the electrolyte flow path is formed in the electrode slurry layer.

The present invention also provides a large area stack / folding type battery, wherein the electrolyte flow path is formed in an arcuate shape.

Also, the present invention provides a large area stack / folding type battery wherein the thickness of the electrolyte flow path is within a range of 50-100% of the thickness of the electrode slurry layer.

Also, the present invention provides a large-area stack / folding type battery in which the electrolyte flow path has a cross-sectional area of 0.05 to 2% based on the cross-sectional area of the electrode slurry layer.

Also, the present invention provides a large-area stack / folding type battery in which the electrolyte flow path has one per 225 cm 2 of the electrode slurry layer.

Also, the present invention provides a large area stack / folding type cell wherein the area of the electrode slurry layer is at least 225 cm 2.

In the present invention, the electrode includes an electrode tab on the current collector, and each of the electrode tabs is provided for each region divided by the electrolyte flow paths.

Also, in the present invention, the electrode includes an electrode tab on the current collector, and the electrode tab includes two or more regions divided by the electrolyte flow paths, thereby providing a large area stack / folding type battery .

Since the secondary battery according to the present invention has the electrolyte flow path formed therein, unlike the conventional battery, penetration of the electrolyte solution proceeds smoothly, and thus it can be widely applied to the development of a secondary battery having a large-area high-density energy.

Hereinafter, the present invention will be described in detail.

According to the present invention,

An electrode slurry layer formed by applying an electrode slurry to the current collector; And an electrode assembly formed by alternately stacking separators, wherein the stack /

Wherein the electrode comprises an electrolyte flow path. The present invention also relates to a large area stack / folding type battery.

And the electrolyte flow path is formed in the electrode slurry layer. The secondary battery is completed by sealing the battery case after the electrode assembly is housed in the battery case and the electrolyte is injected. The electrolyte flow path serves as a passage for the electrolyte to distribute the electrolyte evenly on the electrode surface when the electrolyte is injected. Particularly, in the case of a large-area secondary battery, when the electrolyte flow path is not formed, a portion sufficiently wetted with the electrolytic solution and a portion not sufficiently wetted may appear, which causes deterioration of battery performance. Therefore, the battery of the present invention is provided with an electrolyte flow path to improve the electrolyte wettability of the electrode assembly when the electrolyte solution is injected.

The electrolyte flow path can be formed when the electrode slurry is applied to the current collector. That is, the electrode is usually prepared by coating an electrode slurry obtained by kneading an electrode active material, a binder, a conductive material, etc. on a metal current collector and drying the electrode slurry. When the electrode slurry is coated and dried, the electrode slurry is uniformly spread So that the electrolyte flow path can be formed.

The electrolyte flow path is preferably formed when the slurry has a suitable viscosity in the process of drying the slurry. At this time, a method of scraping the flat electrode slurry layer with a blade or the like, or a method of forming by stamping with a recessed groove .

The electrolyte flow path is preferably formed in an arcuate shape. The electrode assembly is a laminate of a plurality of anodes, cathodes, and separators. In this case, since the load is applied to each of the electrodes, the grooves of the electrode slurry layer (that is, the electrolyte channels) may be broken. Therefore, it is preferable that the groove is formed in an arcuate shape which is geometrically advantageous for dispersing the load.

It is preferable that the thickness of the electrolyte flow path is formed within a range of 50 to 100% of the thickness of the electrode slurry layer. If it is less than 50%, there is a fear that the electrolytic solution is insufficient to pass through, and if it exceeds 100%, the current collector can not be etched.

For the same reason, it is preferable that the electrolyte flow path has a cross-sectional area of 0.05 to 2% based on the cross-sectional area of the electrode slurry layer. If it is less than 0.05%, there is a fear that the electrolytic solution is insufficient to pass through, and when it exceeds 2%, there is a problem in the strength of the electrode slurry layer against the load.

The present invention is particularly useful in a large area stack / folding type cell in which the area of the electrode slurry layer is at least 225 cm 2. As the area of the battery is large, the electrolyte may not be evenly distributed as described above, which may cause deterioration of the solar cell performance.

Particularly, in the present invention, it is appropriate that the electrolyte flow path is formed at a rate of about one per 225 cm 2 of the electrode slurry layer. The amount of the electrode active material may be excessively decreased and the wetting property may be inefficient (i.e., the wettability is higher than the number of the electrolyte flow channels formed, The degree of improvement may be insignificant).

The thickness of the electrode slurry layer is preferably 50 占 퐉 or more.

Further, in the present invention, the electrode has an electrode tab on the current collector. Wherein the electrode tabs are provided for each of the regions divided by the electrolyte flow paths; Or two or more regions divided by electrolytic solution flow paths.

When the battery is made large, the electrode slurry layer can also be large-sized. In such a large-sized electrode slurry layer, the active material may be unevenly distributed. That is, even if all of the active material is electrically connected to the current collector, the active material in the region close to the tab can easily and frequently be charged and discharged, but the non-active region may form a dead zone in which the active material is not used properly will be. Therefore, in order to improve the characteristics of the battery, it is preferable to provide a plurality of electrode tabs or to extend over a wide area.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 and FIG. 2 illustrate an embodiment embodying the present invention, and the scope of the present invention is not limited thereto.

Fig. 1 shows an electrode embodying the present invention by way of example. 1, an electrode slurry layer 100 is provided on a current collector 200, and a longitudinal electrolyte flow path 110 is formed on a surface of the electrode slurry layer 100. An electrode tab 300 is provided on the current collector 200. Each of the electrode tabs 300 is provided for each region divided by the electrolyte flow path 110. The electrode tabs 300 include a positive electrode tab 310 and a negative electrode tab 320, The positive electrode tab 300 is referred to as a positive electrode tab 310 and the electrode tab 300 provided on a negative electrode is referred to as a negative electrode tab 310).

2 is a perspective view of an electrode assembly embodying the present invention. The electrode in which the electrolyte flow path 110 of FIG. 1 was formed was alternately laminated with the separation membrane 400 in order to form an electrode assembly.

FIG. 3 shows an electrolyte flow path portion in a vertical section of an electrode assembly embodying the present invention. 3, since the electrolyte flow path 110 is formed between the separation membrane 400 and the electrode slurry layer, the electrolyte can uniformly penetrate the electrode slurry layer through the electrolyte flow path 110, Can be improved.

Fig. 4 illustrates another electrode embodying the present invention by way of example. 4, an electrode slurry layer 100 is provided on a current collector 200, and a longitudinal electrolyte flow path 110 is formed on a surface of the electrode slurry layer 100. As shown in FIG. 1 is that the electrode tab 300 is provided over a wide area in which the electrode tab 300 is divided into the electrolyte flow path 110.

Hereinafter, the present invention will be described in further detail with reference to examples. The embodiments described herein are for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention.

The electrodes of Examples and Comparative Examples were prepared as follows.

Example

[Production of negative electrode]

N-methyl-2-pyrrolidone (NMP) as a solvent was mixed with carbon powder as a negative electrode active material, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material in an amount of 96 wt%, 3 wt% To prepare a negative electrode mixture slurry. The negative electrode mixture slurry was applied to a copper (Cu) thin film as an anode current collector having an area of about 250 cm 2. After about 30 minutes, a stamp having a concave / convex shape of "∩" shape was formed on the electrode slurry layer to form an electrolyte flow path, and finally dried to prepare a negative electrode.

[Production of anode]

92 wt% of a lithium cobalt composite oxide as a positive electrode active material, 4 wt% of carbon black as a conductive material, and 4 wt% of PVDF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having an area of about 250 cm 2. After about 30 minutes, stamps having "∩" shape irregularities were formed on the electrode slurry layer to form electrolytic flow channels, followed by final drying to prepare the positive electrode.

[Manufacture of electrode assembly]

A polyethylene separator was laminated and assembled on the positive electrode and the negative electrode, followed by roll press to produce an electrode assembly.

Comparative Example

[Production of negative electrode]

A negative electrode was prepared in the same manner as in Example 1 except that a stamp having an unevenness of "∩" shape was printed on the electrode slurry layer to form an electrolyte flow path.

[Production of anode]

A positive electrode was prepared in the same manner as in the Example except that a stamp having an unevenness of "∩" shape was formed on the electrode slurry layer to form an electrolyte flow path.

[Manufacture of electrode assembly]

A polyethylene separator was laminated and assembled on the positive electrode and the negative electrode, followed by roll press to produce an electrode assembly.

Experimental Example  - [electrolyte solution Wetting (Wettability) Experiment]

The electrode assembly of the above Examples and Comparative Examples was impregnated with an electrolytic solution. The amount of electrolytes weighed per hour in the electrode assembly (calculated by subtracting the weight of the initial electrode assembly from the weight of the electrolyte + electrode assembly after impregnating the electrode assembly in the electrolyte) was measured.

The results are shown in Table 1 below.

Electrolyte impregnation time (hr) Example Comparative Example One 1.28 g 0.95 g 24 2.35 g 1.91 g 48 3.5 g 2.85 g

As shown in Table 1, when the electrolytic solution flow path is provided as in the embodiment, the diffusion rate of the electrolytic solution is faster than that of the comparative example, and the amount of the electrolyte impregnated finally is higher.

While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. .

1 is an illustration of an electrode embodying the present invention.

2 is an illustration of an electrode assembly embodying the present invention.

3 is a partial view showing an electrolyte flow path portion in a vertical section of an electrode assembly embodying the present invention.

4 is an illustration of another electrode embodying the present invention.

[Description of Drawings]

100: electrode slurry layer 110: electrolyte flow path

200: Collector 300: Electrode tab

310: positive electrode tab 320: negative electrode tab

400: membrane

Claims (9)

An electrode slurry layer formed by applying an electrode slurry to the current collector; And an electrode assembly formed by alternately stacking separators, wherein the stack / The electrode includes an electrolyte flow path formed in the electrode slurry layer, Wherein the electrolyte flow path is formed at an interface between the electrode slurry layer and the separation membrane. delete The large area stack / folding type battery according to claim 1, wherein the electrolyte flow path is formed in an arcuate shape. The large area stack / folding type battery according to claim 1, wherein the thickness of the electrolyte flow path is within a range of 50 to 100% of the thickness of the electrode slurry layer. The large area stack / folding type battery according to claim 1, wherein the electrolyte flow path has a cross-sectional area of 0.05 to 2% based on a cross-sectional area of the electrode slurry layer. The large area stack / folding type battery according to claim 1, wherein the electrolyte flow path has one per 225 cm 2 of the electrode slurry layer. The large area stack / folding type battery according to claim 1, wherein the electrode slurry layer has an area of 225 cm 2 or more. The large area stack / folding type battery according to claim 1, wherein the electrode comprises an electrode tab on a current collector, and the electrode tab is provided for each region divided by the electrolyte flow path. The large area stack / folding type battery according to claim 1, wherein the electrode comprises an electrode tab on a current collector, and the electrode tab has two or more regions divided by electrolyte flow paths.

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