KR100659837B1 - Method of coating electrode materials for secondary battery and apparatus for the same - Google Patents

Abstract

Provided are a method for coating an electrode active material of a secondary battery, and its coating apparatus, to allow an active material layer to be formed uniformly, thereby improving charge/discharge efficiency. The method comprises the steps of coating an active material slurry on an electrode current collector with moving an electrode substrate(110); and drying the active material slurry to form an active material layer, wherein a velocity measurement device having a rolling wheel(210) in closely adhered to the electrode substrate to be wound to an electrode roll is installed at the part where the electrode roll is wound or unwound; and the rolling wheel is rolled by winding or unwinding the electrode roll so as to calculate the moving velocity of the rolling wheel by the velocity measurement device and to measure the moving velocity of the electrode substrate.

Description

Method and apparatus for applying electrode active material of secondary battery {Method of coating electrode materials for secondary battery and Apparatus for the same}

1 is a schematic perspective view for explaining a method of applying an electrode active material slurry to an electrode current collector table in the related art.

Fig. 2 is a schematic structural diagram showing a part of the apparatus embodiment of the present invention with the speed measuring system for carrying out the method of the present invention in contact with the electrode roll.

FIG. 3 is a flowchart schematically showing an embodiment of a method of adjusting the rotation speed of the winder roller 140 according to the traveling speed measuring device having the configuration as shown in FIG. 2 through a box.

* Explanation of symbols for the main parts of the drawings

10: electrode current collector 20: slit die

30: slurry layer 40: pulley

50: dryer 110: electrode substrate

140: unwinder roller 220: encoder

210: cloud wheel 230: cylinder gear

The present invention relates to a method for applying an electrode active material of a secondary battery, and more particularly, to a method for measuring and adjusting an electrode active material coating speed of a secondary battery.

Secondary batteries are rechargeable and have a high possibility of being small and large in capacity. Recently, as demand for portable electronic devices such as camcorders, portable computers, and mobile phones is increasing, research and development on secondary batteries has been made with the power of these portable electronic devices. Representative examples of the recent development and use include nickel-hydrogen (Ni-MH) batteries, lithium (Li) ion batteries, and lithium ion (Li-ion) polymer batteries.

Most of the bare cells in these secondary batteries contain an electrode assembly consisting of a positive electrode, a negative electrode and a separator in a can made of aluminum or an aluminum alloy, the can is closed with a cap assembly, and an electrolyte is injected into the can. It is formed by sealing. In the case of a polymer battery in which an electrode or a separator is formed of a polymer, the separator plays a role of an electrolyte solution or impregnates an electrolyte component in the separator, so that leakage of the electrolyte solution is no problem or less, and thus a pouch is used instead of a can.

In lithium secondary batteries, electrodes are often formed by applying a slurry containing an electrode active material to the surface of a current collector made of metal foil or a metal mesh. The slurry is usually formed by mixing a solvent, a plasticizer, an electrode active material, a binder and the like. As the current collector, copper is used for the negative electrode and aluminum is used for the positive electrode. Polyvinylidene fluoride (PVDF) and stylene butadiene rubber (SBR) are used as binders, acetone and NMP (N-methylprolidone) as a solvent. And the like can be used. On the other hand, water may be used as a solvent.

1 is a schematic perspective view for explaining a method of applying a slurry to an electrode current collector in the prior art.

Referring to FIG. 1, the electrode current collector 10, which is wound in a roll shape in a unwinder (not shown) and is supplied with a predetermined width, is unwound in a plane to lower the slit die 20 and the dryer 50. After rewinding in the winder (not shown). The slit die 20 receives a slurry from a slurry tank (not shown) and serves to evenly spray the slurry through a die formed to have a slit shape. Since the electrode current collector 10 constantly passes under the slit die 20, a slurry layer 30 having a predetermined thickness is attached to the surface of the electrode current collector 10.

Since the slurry is a fluid state containing a large amount of solvent, the dryer 50 sends hot air to volatilize and remove the solvent of the slurry, and the slurry is attached to the electrode current collector with considerable strength by the action of a binder. Reference numeral 40 denotes a pulley for moving the electrode current collector.

Slurry is applied to the electrode collector or electrode collector. The substrate is dried in rolls by winding and unwinding rollers at the beginning and end, and then unrolled for slurry application, and then rolled again after slurry application. It is wound up. In order to uniformly charge and discharge the entire electrode assembly of the secondary battery, and to include more active material in a small volume, it is necessary to maintain the electrode assembly in a uniformly wound form. In order to form an evenly wound electrode assembly, it is necessary that the thickness of the slurry applied to the electrode current collector is constant.

In order to apply the slurry to the surface of the electrode current collector with a constant thickness and a constant length, the running speed of the electrode current collector itself must be kept constant. The running speed of the substrate on the roller in which the electrode substrate forming the roll is wound and unrolled is not constant as the radius of the roll is changed as the roll is wound and unrolled, even if the speed of the motor winding the roll is constant. That is, assuming that the outer periphery of the roll is a circle, if the roll is rolled or unwound at a constant angular velocity, the linear running speed of the substrate is increased by the radius since the radius of the roll is multiplied by the angular velocity. In order to keep the line running speed constant, the angular velocity of rolling is increased in inverse proportion to the radius of the roll.

Therefore, the measurement of the substrate speed in the conventional unwinding / winding section was made through the following equation calculation considering the motor speed of the unwinding / winding machine and the thickness of the substrate.

Travel speed of substrate (v) = 2π * radius (R) * angular speed (ω)

Radius (R) = (substrate thickness (T) * revolutions) + roller radius

In consideration of the angular velocity of the motor and the radius of the electrode roll, the substrate traveling distance when the motor rotates once is calculated to calculate the substrate traveling distance per hour, that is, the traveling speed. In addition, as the running continued, it was assumed that the radius of the electrode roll was increased in consideration of the thickness of the substrate, and the substrate running speed was calculated in consideration of the radius. This method is not a direct measurement method and cannot be regarded as an accurate speed since motor speed change and substrate thickness unevenness are not considered.

In the conventional method, even if the traveling speed is recognized as a constant, the traveling speed of the actual substrate may be changed. As the traveling speed of the substrate at the roller position changes, the tension of the substrate changes, and conversely, when the tension applied to the substrate changes, the traveling speed of the substrate changes. In such a situation, even application of the slurry is difficult to consider, and forming the jelly roll of the electrode assembly using the electrode thus formed may lower the battery capacity and reduce the charge and discharge efficiency.

That is, if the substrate traveling speed can be accurately measured, it is possible to accurately measure the thickness and length of the slurry by controlling the speed of the motor winding the electrode roll according to the measurement by determining the proper driving speed. It is therefore difficult to apply the slurry to the correct thickness and length. Accordingly, there is a problem in that the uniformity and quality of the complete electrode plate and the electrode assembly are inferior.

The present invention is to solve the problem of the electrode slurry coating method of the conventional secondary battery described above, and to provide a method and apparatus that can measure the traveling speed of the electrode substrate at the position where the electrode roll is unwinded or wound by a more direct method For the purpose of

An object of the present invention is to provide a method and apparatus capable of precisely measuring the traveling speed of the electrode substrate at the position at which the electrode roll is unrolled or wound and thereby adjusting the traveling speed of the electrode substrate.

As a result, an object of the present invention is to provide a method and apparatus that can form the thickness of the active material layer of the electrode assembly to increase the electrode capacity and increase the charge and discharge efficiency.

In order to achieve the above object, the present invention provides a speed measuring system having a rolling wheel to contact the electrode substrate at a portion where the electrode roll is wound or unrolled, so that the rolling wheel touching the electrode substrate is turned while winding or unwinding the electrode roll. The speed measuring system is characterized by calculating the traveling speed of the rolling wheel.

In the method of applying the secondary battery electrode active material of the present invention, a speed measuring system having a rolling wheel is installed on a portion of the electrode roll wound or unrolled so as to contact the electrode substrate, and the rolling wheel touching the electrode plate is turned while winding or unwinding the electrode roll. The speed measuring system may then include a process of comparing the calculated value with a reference value, and a process of adjusting the speed of the motor winding the electrode roll according to the result of the comparing process. . These processes can be done continuously and cyclically while driving the electrode substrate.

The apparatus of the present invention for achieving the above object is an electrode active material comprising an unwinder for winding or unwinding the electrode roll, a winder, a roller of the substrate traveling path, a coating device such as a slit die for slurry application, and a slurry drying device. In the coating device,

A speed measuring system having a rolling wheel in contact with the electrode substrate is provided at a position where the electrode roll is wound or unwound.

In the present invention, the electrode base wound or unrolled on the electrode roll and the rolling wheels of the speed measuring system are considered to be in close contact with each other and do not slide. When measured, the linear running speed of the substrate undergoing the slurry coating process may be calculated by multiplying the radius of the wheel by the angular speed of the wheel. In this case, the angular velocity measuring device may be formed in various forms well known. For example, a type of generator may be coupled to the wheel shaft to measure power, voltage, and current value calculated by the generator. It is also possible to install a signal generator for generating an optical signal in a certain part of the rolling wheels, barcodes arranged at regular intervals, and to install an optical signal sensor, a decoder, etc. fixed around the rolling wheels, to measure the angular velocity.

In the present invention, the cylinder wheel device is coupled to one end of the shaft of the rolling wheel so that the rolling wheel is kept in contact with the electrode substrate on the surface of the electrode roll with a predetermined pressure irrespective of the change in the radius of the electrode roll on which the electrode substrate is wound It can be combined with the other end of the. The cylinder may be actuated by pneumatic or hydraulic pressure, or may contact the rolling wheel with the electrode plate by an elastic material such as a spring, such as a shock absorber.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Fig. 2 is a schematic structural diagram showing a part of the apparatus embodiment of the present invention with the speed measuring system for carrying out the method of the present invention in contact with the electrode roll.

Although not shown, similar to a conventional electrode active material applying apparatus, the apparatus of the present invention may be provided with a winding machine, a winding machine, a transfer roller, a slurry coating apparatus, a drying apparatus, and the like. Inside the winder electrode roll, the winder roller 140 connected to the motor M is positioned to wind the electrode substrate 110 on which the slurry is applied. For slurry application or drying, the substrate unwound in the unwinder is moved linearly, and rollers for conveying, supporting and turning can be installed in the process. The electrode substrate 110 is wound in a circle along the outer circumference of the electrode roll in the winder roller 140. The speed measuring system of the present invention is installed at a position where the outer periphery of the electrode roll and the linear running section of the electrode substrate 110 are in contact, that is, the position at which the electrode substrate 110 starts to be wound on the electrode roll. The speed measuring system includes a rolling wheel 210 and an encoder 220 installed around an axis of the rolling wheel 210, and the shaft of the rolling wheel 210 is coupled to a portion of the active material applying equipment through the cylinder device 230. .

The surface of the rolling wheel 210 may be formed of a frictional material such as a rubber such that the surface of the rolling wheel 210 comes into contact with the electrode substrate 110 to move together without slipping when the electrode substrate is wound around the electrode roll. The cylinder device 230 may be applied with pneumatic, hydraulic or built-in elastic body pressure so that the rolling wheel 210 and the electrode substrate 110 is in contact with a certain pressure.

The rolling wheel 210 is installed on a free rotation shaft that is not connected to an external power such as a motor shaft, and rotates by friction with the electrode substrate as the electrode substrate 110 travels. The traveling speed of the electrode substrate becomes the speed of the rolling wheel 210 at the point of contact with the electrode substrate. Of course, don't put too much force on the wheels.

The encoder 220 is directly connected to the axis of the rolling wheel 210 or is installed to detect a signal of a barcode or signal generator (not shown) around the axis. In another embodiment, other types of signal generators and sensors for measuring the angular velocity or the traveling speed of the rolling wheel 210 may be installed in addition to the encoder 220.

The bar code is displayed at regular intervals while rolling around the axis at the rolling wheel 210, and the encoder 220 measures the number of pulse signals represented by the bars passed per hour during the process driving. Since the radius of the rolling wheel is constant and the number of displayed barcodes is constant while making one rotation around the axis, the traveling speed of the substrate can be calculated by the following equation.

Travel speed (V) = 2π * Rolling wheel radius (r) * {Number of pulses per hour ÷ Number of bars displayed per revolution of rolling wheels}

3 is a flow chart schematically showing an embodiment of a method of adjusting the rotational speed (angular speed) of the winder roller 140 according to the traveling speed measuring device having the configuration as shown in FIG. 2 through a box.

At the beginning of the process, the roller starts driving while the winder roller 140 motor M rotates at a predetermined speed (310). The pulse value measured by the encoder during the process is input to a separate equipment controller (C) (320). The controller C compares the numerical signal with a predetermined numerical value, and sends a fine control signal corresponding to the difference value to the roller motor M (330). As the current of the roller motor M is added or subtracted according to the fine control signal of the controller C, the rotational angular velocity of the roller motor M is changed (340). Thus, the roller is driven 310 in a changed state. The driving of the roller is finished through the step 350 of determining termination by a separate end signal. At this time, when the roller driving state is changed, the tension in which the roller pulls the substrate is changed. The change in tension pulling the substrate changes the running speed of the linear section of the substrate. This feedback system regulates roller drive so that the substrate travels at a constant speed during the process.

According to the present invention, since the traveling speed of the electrode substrate can be measured at the position where the electrode roll is unrolled or wound by a direct method, the traveling speed of the electrode substrate in the process can be accurately measured, and based on the measurement result, the electrode substrate The running speed of the can be adjusted constantly.

Therefore, the thickness of the active material layer of the electrode assembly is evenly formed to increase the electrode capacity and increase the charge and discharge efficiency.

Claims (8)

A method of applying an electrode active material of a secondary battery, comprising: applying a slurry to an electrode current collector while driving an electrode substrate of a secondary battery; and drying the slurry to form an active material layer. On the part where the electrode roll is wound or unwound, a speed measuring system having a rolling wheel in contact with the electrode substrate wound on the electrode roll is installed. The rolling wheel is rotated while the electrode roll is wound or unrolled, so that the speed measuring system calculates the traveling speed of the rolling wheel to measure the traveling speed of the electrode base material. . The method of claim 1, A comparison process of comparing the measured reference speed with a predetermined reference value following the process of measuring the traveling speed of the substrate; The electrode active material coating method of the secondary battery, characterized in that the speed adjustment process for adjusting the speed of the motor winding the electrode roll according to the comparison result of the comparison process is provided. The method of claim 2, The method of measuring the traveling speed, the comparing process, and the speed adjusting process are performed cyclically and continuously while the electrode substrate is traveling. In the electrode active material coating device comprising a winding machine for winding or unwinding an electrode roll, a coating device for slurry application, and a slurry drying device, Electrode active material coating device, characterized in that the speed measuring device having a rolling wheel in contact with the electrode substrate at the position where the electrode roll is wound or unwinded. The method of claim 4, wherein The radius of the rolling wheel is constant, the electrode active material coating device, characterized in that the angular velocity measuring device for measuring the rotational angular velocity of the rolling wheel is installed around the rolling wheel. The method of claim 5, The angular velocity measuring device is an electrode active material coating device comprising a bar code display installed on the rolling wheel and an encoder installed around the rolling wheel. The method of claim 4, wherein The speed measuring system is an electrode active material coating device, characterized in that installed through the cylinder to apply a predetermined pressure or more between the substrate and the rolling wheel. The method of claim 4, wherein And a controller configured to receive a signal of the speed measuring system and perform a comparison operation with a reference value, and to transmit an electrical signal reflecting the result of the comparison operation to a drive motor of a roller on which the electrode roll is wound.

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