KR20060027254A - Electrode plate of li secondary battery - Google Patents

Abstract

According to the present invention, the active material layer is formed of at least two layers having different binders, thereby reducing the content of the binder included in the active material layer, thereby improving the battery efficiency and battery capacity of the lithium secondary battery electrode. A plate, comprising: an electrode current collector; A first active material layer formed on at least one surface of the electrode current collector; It includes an electrode plate for a lithium secondary battery comprising a second active material layer formed on the first active material layer.

Lithium secondary battery, electrode plate, active material layer, binder

Description

Electrode plate for lithium secondary battery {Electrode Plate of Li Secondary Battery}

1A, 2A, and 3A are cross-sectional views for illustrating an electrode plate for a rechargeable lithium battery according to an embodiment of the present invention.

1B, 2B and 3B are process plan views for explaining an electrode plate for a lithium secondary battery according to an embodiment of the present invention.

Figure 4 is a perspective view for explaining an electrode assembly having an electrode plate for a lithium secondary battery according to an embodiment of the present invention.

(Explanation of symbols for main parts of drawing)

110; Electrode current collector 115; Ignorance

120; A first active material layer 130; Second active material layer

140; Electrode tab 200; Electrode assembly

210; A first electrode plate 220; Second electrode plate

230, 240; Separator 250; Insulation tape

The present invention relates to an electrode plate for a lithium secondary battery, and more particularly, so that the active material layer is composed of at least two layers having different binders, thereby reducing the content of the binder contained in the active material layer, the battery of the lithium secondary battery The present invention relates to an electrode plate for a lithium secondary battery capable of improving efficiency and battery capacity.

Recently, compact and lightweight electric / electronic devices such as cellular phones, notebook computers, camcorders, etc. have been actively developed and produced. These portable electric / electronic devices have a battery pack that can be operated in a place where no separate power source is provided. The built-in battery pack includes at least one battery therein for outputting a predetermined level of voltage for driving the portable electric / electronic device for a period of time.

In view of economical aspects, the battery pack employs a secondary battery capable of charging and discharging. Representative secondary batteries include lithium secondary batteries such as nickel-cadmium (Ni-Cd) batteries, nickel-hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) batteries.

In particular, the lithium secondary battery has an operating voltage of 3.6 V, which is three times higher than that of a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for portable electronic equipment, and is rapidly expanding in terms of high energy density per unit weight. to be.

Such lithium secondary batteries mainly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. In general, a battery is classified into a liquid electrolyte battery and a polymer electrolyte battery according to the type of electrolyte, and a battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery. Moreover, although a lithium secondary battery is manufactured in various shapes, a typical shape is a cylindrical type, a square type, and a pouch type.

Typically, the lithium secondary battery is positioned between the positive electrode plate coated with a positive electrode active material, the negative electrode plate coated with a negative electrode active material, and between the positive electrode plate and the negative electrode plate to prevent a short and prevent lithium ion (Li-ion). And an electrode assembly in which a separator capable of moving only is wound, a lithium secondary battery case accommodating the electrode assembly, and an electrolyte solution injected into the lithium secondary battery case to enable movement of lithium ions.

Such a lithium secondary battery is manufactured as follows.

First, a cathode electrode plate coated with the positive electrode active material and connected with a positive electrode tab, a negative electrode plate coated with a negative electrode active material and connected with a negative electrode tab, and a separator interposed between the positive electrode plate and the negative electrode plate are laminated, and then It is wound up to manufacture an electrode assembly.

Then, the electrode assembly is accommodated in the lithium secondary battery case to prevent the electrode assembly from being separated, an electrolyte is injected into the lithium secondary battery case, and then sealed to complete the lithium secondary battery.

Meanwhile, the positive electrode and the negative electrode plate of the lithium secondary battery as described above are prepared by mixing an active material, a conductive material, and a binder with an organic solvent to prepare a slurry, and then applying the same on an electrode current collector to form an active material layer. Is formed.

In this case, the binder imparts a bonding force to the active material and the conductive material to bind to the electrode current collector, the binder generally used is about 6% in the active material layer.

However, the electrode plate for a lithium secondary battery as described above has a problem in that the amount of the active material is reduced by the amount of the binder included in the active material layer, thereby reducing the battery capacity of the lithium secondary battery.

An object of the present invention is to solve the above problems of the prior art, the present invention is to make the active material layer is composed of at least two layers having different binders, by reducing the content of the binder contained in the active material layer, The objective is to provide the electrode plate for lithium secondary batteries which can improve the battery efficiency and battery capacity of a secondary battery.

The present invention for achieving the above object is an electrode current collector; A first active material layer formed on at least one surface of the electrode current collector; It includes an electrode plate for a lithium secondary battery comprising a second active material layer formed on the first active material layer.

The first active material layer and the second active material layer include an active material and a binder, and the content of the binder included in the second active material layer is preferably lower than the content of the binder included in the first active material layer.

In this case, the binder included in the second active material layer is preferably 1/6 to 1/3 of the binder included in the first active material layer, and more preferably, the content of the binder included in the second active material layer is 1 It is preferable that it is% to 3%.                     

The binder is any one of PVDF, SBR, PVC and PE.

The thickness of the second active material layer 130 is preferably 0.1 to 0.9 times the thickness of the first active material layer 120.

In addition, the present invention is an electrode current collector; It is laminated on at least one surface of the electrode current collector, and comprises a plurality of active material layers including an active material and a binder, the highest content of the binder of the active material layer that is bonded to the electrode current collector of the plurality of active material layers An electrode plate for lithium secondary batteries is included.

It is preferable that the ratio of the content of the binder of the remaining active material layer to the content of the binder of the active material layer bonded to the electrode current collector in the active material layer is 1/6 to 1/3.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1A, 2A, and 3A are cross-sectional views illustrating a lithium secondary battery electrode plate according to an embodiment of the present invention, and FIGS. 1B, 2B, and 3B are electrode plates for a lithium secondary battery according to an embodiment of the present invention. It is a process plan view for demonstrating this.

1A and 1B, an electrode current collector 110 is prepared first. In this case, the electrode current collector 110 is formed in a kind of plate-like shape having a predetermined width and a predetermined length.

In addition, when the electrode current collector 110 is a positive electrode current collector, generally made of aluminum (Al) and equivalents thereof, and in the case of the negative electrode current collector, generally made of copper (Cu) and equivalents thereof, the present invention It is not intended to limit the material.

2A and 2B, the first active material layer 120 is formed on at least one surface of the electrode current collector 110 except for portions of both ends in the length direction. Both ends of the electrode current collector 110 serve as the uncoated portion 115 where the active material layer is not formed.

When the electrode current collector 110 is a cathode current collector, the first active material layer 120 may include a cathode active material that generates electrons by participating in a cathode chemical reaction of a lithium secondary battery, and electrons generated from the cathode active material. A positive electrode slurry, in which a conductive agent to be transferred to a current collector, the positive electrode active material and the conductive agent, and a positive electrode binder that maintains the mechanical strength of the positive electrode plate are mixed through a solvent, are formed by coating on the electrode current collector 110. do.

Alternatively, when the electrode current collector 110 is a negative electrode current collector, the first active material layer 120 participates in a negative electrode chemical reaction of a lithium secondary battery, in which electrons are introduced, and the negative electrode active material is used as the electrode current collector. A negative electrode binder, which binds to the whole phase and maintains the mechanical strength of the negative electrode plate, is formed by coating the negative electrode slurry mixed with a solvent on the electrode current collector 110.

A chalcogenide compound is used as the cathode active material, and complex metal oxides such as LiCoO 2, LiMn 2 O 4, LiNiO 2, LiNi 1-x Cox O 2 (0 <x <1), and LiMnO 2 are used. As the negative electrode active material layer material, a carbon (C) -based material, Si, Sn, tin oxide, composite tin alloys, transition metal oxide, lithium metal nitride, or lithium metal oxide is used. It does not limit a positive electrode active material and a negative electrode active material.

As the conductive agent, graphite-based materials such as artificial graphite and natural graphite, carbon black-based materials such as acetylene black, thermal black and channel black, conductive fibers such as carbon fiber and metal fiber, copper nickel, aluminum, Materials such as metal powder such as silver and metal oxide such as titanium oxide may be used, but the material is not limited thereto.

In addition, as the positive electrode binder and the negative electrode binder, polyvinylidene fluoride (hereinafter referred to as "PVDF"), styrene butadiene rubber (hereinafter referred to as "SBR"), polyvinyl chloride (polyvinyl chloride, A material such as "PVC" or polyethylene (hereinafter, referred to as "PE") may be used, and the first active material layer 120 may contain about 6%.

3A and 3B, a second active material layer 130 is formed on the first active material layer 120 to form an electrode plate for a lithium secondary battery.

In this case, since the first active material layer 120 is bound to the electrode current collector 110, the second active material layer 130 is connected to the first active material layer 120. In comparison, a lower binding force may be required. Therefore, the binder of the second active material layer 130 may be contained in the active material layer at a lower ratio than the binder of the first active material layer 120. Preferably, the binder of the second active material layer 130 is contained in the second active material layer 130 at a ratio of 1/6 to 1/3 of the binder of the first active material layer 120, more preferably. The binder of the second active material layer 130 is contained in the second active material layer 130 1% to 3%.

In addition, the thickness of the second active material layer 130 is preferably 0.1 times to 0.9 times the thickness of the first active material layer 120.

After forming the second active material layer 130, the electrode tab 140 may be attached to any one of the plain portions 115 at both ends of the electrode current collector 110 in the longitudinal direction. In this case, the electrode tab 140 is generally made of aluminum (Al) in the case of the positive electrode tab, and is generally made of nickel (Ni) in the case of the negative electrode tab, but the material is not limited thereto.

As described above, the electrode plate for a lithium secondary battery of the present invention includes an electrode current collector 110, a first active material layer 120 formed on at least one surface of the electrode current collector 110, and a first active material layer 120. It consists of the second active material layer 130 formed on. In this case, since the first active material layer 120 is bound to the electrode current collector 110, the second active material layer 130 may reduce the content of the binder relatively to the first active material layer 120. Can be. Therefore, as the content of the binder decreases, the content of the active material participating in the battery reaction of the lithium secondary battery may be improved.

On the other hand, Figure 4 is a perspective view for explaining an electrode assembly having an electrode plate for a lithium secondary battery according to an embodiment of the present invention.

As shown in FIG. 4, the electrode assembly 200 may include any one of a positive electrode active material and a negative electrode active material, for example, a first electrode plate 210 coated with a positive electrode active material, and another one of a positive electrode active material and a negative electrode active material. For example, the first electrode plate 210 and the second electrode plate may be disposed between the second electrode plate 220 coated with the negative electrode active material, the first electrode plate 210, and the second electrode plate 220. The separators 230 and 240 are formed in a wound form to prevent short of 220 and to allow only lithium ions to move. At this time, the first electrode plate 210 and the second electrode plate 220 is made of the electrode plate for the lithium secondary battery shown in Figures 3a and 3b, it is possible to improve the battery capacity of the lithium secondary battery. That is, the battery capacity of the lithium secondary battery is increased by using an electrode plate for a lithium secondary battery having an active material layer having an improved active material content by reducing the content of a binder to the first electrode plate 210 and the second electrode plate 220. To improve.

In addition, a first electrode tab 215 protruding a predetermined length upwardly is bonded to the first electrode plate 210, and a second protruding downward predetermined length of the second electrode plate 220 acts as a negative electrode tab. Although the two electrode tabs 225 are bonded to each other, the protrusion direction of the tabs of the first electrode 215 and the second electrode tab 225 is not limited in the present invention.

In order to prevent a short circuit between the first electrode plate 210 and the second electrode plate 220 at the boundary portion at which the first electrode tab 215 and the second electrode tab 225 are drawn out from the electrode assembly 200. Insulated by the insulating tape 250, respectively.

Meanwhile, in the exemplary embodiment of the present invention, the first active material layer 120 and the second active material layer 130 are sequentially formed on the electrode current collector 110, and the binder of the first active material layer 120 is provided. For example, the electrode plate for a lithium secondary battery having a higher content than the content of the binder of the second active material layer 130 has been described by way of example. The electrode plate for the lithium secondary battery may include a plurality of active materials on at least one surface of the electrode current collector 110. The layer may include a structure having a highest content of a binder of the active material layer bonded to the electrode current collector 110 among the plurality of active material layers.                     

That is, by increasing the content of the binder of the active material layer directly bonded to the electrode current collector 110, the binding force between the active material layer and the electrode current collector 110 can be enhanced, and the other active material layer lowers the content of the binder. As a result, the battery capacity of the lithium secondary battery may be improved by increasing the content of the active material included in the entire active material layer formed on the electrode current collector 110.

As described above, according to the present invention, the present invention is made so that the active material layer is composed of at least two layers having different binders, by reducing the content of the binder contained in the active material layer, the battery efficiency and battery capacity of the lithium secondary battery The electrode plate for lithium secondary batteries which can improve this can be provided.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (8)

An electrode current collector; A first active material layer formed on at least one surface of the electrode current collector; And a second active material layer formed on the first active material layer. The method of claim 1, The first active material layer and the second active material layer is made of an active material and a binder, The amount of the binder included in the second active material layer is lower than the content of the binder contained in the first active material layer, the electrode plate for a lithium secondary battery. The method of claim 2, The binder included in the second active material layer is 1/6 to 1/3 of the binder included in the first active material layer, characterized in that the lithium secondary battery electrode plate. The method of claim 2, The amount of the binder included in the second active material layer is an electrode plate for a lithium secondary battery, characterized in that 1% to 3%. The method of claim 2, The binder is a lithium secondary battery electrode plate, characterized in that any one of PVDF, SBR, PVC and PE. The method of claim 1, The thickness of the second active material layer is 0.1 to 0.9 times the thickness of the first active material layer, the electrode plate for a lithium secondary battery. An electrode current collector; It is laminated on at least one surface of the electrode current collector, and comprises a plurality of active material layers having an active material and a binder, The electrode plate for a lithium secondary battery, characterized in that the content of the binder of the active material layer that is bonded to the electrode current collector among the plurality of active material layer is the highest. The method of claim 7, wherein The ratio of the content of the binder of the remaining active material layer to the content of the binder of the active material layer to be bonded to the electrode current collector of the active material layer is 1/6 to 1/3, characterized in that the lithium secondary battery electrode plate.

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