KR19990000578A - Manufacturing method of negative electrode for nickel hydride battery using new binder - Google Patents

Abstract

Ethyl silicate represented by the following formula (1) is used as a binder in the preparation of a negative electrode of a nickel-metal hydride battery, and the ethyl silicate is used as a component of the negative electrode active material slurry, or is used by coating the surface alone.

[Formula 1]

N is an integer of 1-8.

Description

Manufacturing method of negative electrode for nickel hydride battery using new binder

[Industrial use]

The present invention relates to a method for manufacturing a negative electrode, and more particularly, to a method for manufacturing a negative electrode of a nickel-metal hydride battery which is a kind of alkaline secondary battery used as a power source of various devices.

[Prior art]

As the popularity of various portable electronic devices such as cameras, camcorders, portable CD players, portable radio / recorders, laptops, computers, pagers or portable telephones is increasing, there is a need for high capacity and long life batteries. In particular, in terms of economics, the focus is on technologies for reducing the manufacturing cost of batteries.

Generally, a battery converts chemical energy into electrical energy by using a difference of contact potentials between suitable materials. When the batteries are technically classified, only a discharge for converting chemical energy into electrical energy such as a manganese battery, an alkaline battery, a mercury battery, and a silver oxide battery is performed. Secondary battery that can be repeatedly discharged and recharged such as low pressure type Ni / MH battery, sealed nickel cadmium battery, nickel hydrogen battery, lithium metal battery, lithium ion battery, lithium polymer battery such as lithium polymer battery, etc. It can be classified into a battery, a fuel cell that converts combustion heat of hydrocarbons into electrical energy as it is, and a solar cell that converts light energy into electrical energy. Primary batteries have a small capacity, short lifespan, and cannot be recycled to cause environmental pollution. On the other hand, secondary batteries can be recharged and used for a long time, and the average voltage is much higher than that of primary batteries. It has excellent advantages in terms of environmental protection as it generates less waste.

As another classification, it may be classified into an alkaline battery, a solid electrolyte battery, a non-aqueous battery, and the like according to the composition of the electrolyte, and may be classified into a cylindrical battery, a button battery, and a coin battery according to the appearance of the battery.

Here, the cylindrical (Jelly-Roll type) battery is a battery that emits a current consisting of a positive electrode and a negative electrode, and a separator, an electrolyte, and a positive terminal and a negative terminal to prevent a short circuit between the poles.

The structure of a cylindrical battery is demonstrated in detail taking an nickel hydrogen battery as an example. Cylindrical nickel-metal hydride battery is a positive electrode plate coated with a positive electrode active material Ni (OH) ₂ and a negative electrode plate is a hydrogen storage alloy coated with a negative electrode active material mainly composed of LaNi ₅ , MmNi ₅ , Ti-Fe or Ti-Ni alloy, and the The separator consists of a nonwoven fabric or cellophane tape to prevent short circuits between the positive and negative plates of the anode, and the terminals thereof include a cap, a cathode terminal, and a case serving as a storage device, as well as a safety valve, sealing plate, and insulation. It consists of a ring and an insulating plate.

The manufacturing method of such a cylindrical nickel-metal hydride battery is as follows.

First, the positive electrode active material slurry is coated, dried, and rolled on a metal support to prepare a positive electrode plate, and the negative electrode active material slurry is coated, dried, and rolled onto a metal support to prepare a negative electrode plate, and then a separator is interposed between the positive electrode plate and the negative electrode plate. After winding, the electrode plate and the separator assembly assembled in the wound state are inserted into the can, and the electrolyte is injected and manufactured by attaching the cap assembly to the upper opening.

As a binder used when manufacturing the conventional negative electrode, ion permeable resins, such as polyvinyl alcohol and carboxymethyl cellulose, polyethylene, a fluororesin, etc. are mentioned. When the binder is used in a small amount, the charge and discharge of the battery is repeated and micronized by expansion of the hydrogen storage alloy electrode, resulting in deterioration of performance. When used in a large amount, the stability is improved during long-term use, but the battery reaction is inhibited. Is lowered.

Looking at the deterioration mechanism of the hydrogen storage alloy electrode, the hydrogen storage alloy occludes hydrogen in the alloy by charging and releases hydrogen in the alloy by discharging. Such occlusion and release typically results in a change in volume of the alloy. That is, when occluding hydrogen, volume expansion of about 10 to 20% of the original volume occurs, and upon release, the phenomenon of returning to the original state is repeated. As a result, cracking of the alloy and continuous hydrogen occlusion and release proceed, resulting in the fine grinding of the alloy into fine powder.

Thus, the binder until now has a weak binding force and cannot solve deterioration of an electrode.

The present invention has been made to solve the above problems of the prior art, it is difficult to prevent the deterioration of the electrode basically due to the weak binding force and eliminate the defects of the conventional binder that inhibits the battery performance when a large amount of input and put a small amount It is also to provide a binder having new physical properties capable of producing a long life battery by having a strong binding force.

The present invention has the following configuration to achieve the above object of the present invention.

The present invention provides a binder for nickel-metal hydride batteries containing ethyl silicate represented by the following formula (1).

[Formula 1]

N is an integer of 1-8.

The present invention also provides an active material slurry for nickel hydrogen battery negative electrode comprising a hydrogen storage alloy, a conductive agent, a thickener and ethyl silicate.

The hydrogen storage alloy is 90 to 100% by weight, the conductive agent is 0.1 to 10% by weight, the thickener is 0.1 to 4% by weight and the ethyl silicate is preferably 0.1 to 10% by weight.

In addition, the present invention includes a process for preparing an active material slurry for the nickel-metal hydride battery negative electrode comprising a hydrogen storage alloy, a conductive agent, a thickener and ethyl silicate, applying the active material slurry to a support and drying by hot air at 120 ℃ 20 minutes Provided is a method for manufacturing a negative electrode plate for a nickel hydrogen battery.

The hydrogen storage alloy is 90 to 100% by weight, the conductive agent is 0.1 to 10% by weight, the thickener is 0.1 to 4% by weight and the ethyl silicate is preferably 0.1 to 10% by weight.

Then, a hydrogen storage alloy and a conductive agent are mixed and a thickener is added and stirred to prepare a slurry. The slurry is applied to an active material support, dried by hot air at 120 ° C. for 20 minutes, and the thickness of the coating film is 0.1 to 10 μm on the dried active material support. It provides a negative electrode plate manufacturing method for a nickel-hydrogen battery comprising the step of coating the ethyl silicate to be.

In order to solve the problems of the prior art, by producing a hydrogen storage alloy electrode using ethyl silicate as a binder has excellent performance as follows.

Ethyl silicate exhibits excellent performance as a liquid binder of a colorless and transparent battery that forms a transparent silica film when coated on the surface of the electrode plate. In particular, it has a good condition for producing a long-life battery because it has a high permeability and penetrates well between particles forming the electrode plate to coat the particles individually to suppress the dropping and expansion of the particles.

Ni-MH, which is a type of alkaline secondary battery, is in the spotlight due to the development of portable devices and is used as a power source for various devices.

Referring to the charging and discharging reaction of the nickel hydride battery prepared as described above in detail as follows.

The negative electrode active material is a hydrogen storage alloy capable of absorbing and releasing hydrogen according to the change of the surrounding hydrogen pressure or the temperature. The positive electrode active material is nickel hydroxide, and an aqueous potassium hydroxide (KOH) solution is used as an electrolyte solution. When charging, the hydrogen storage alloy formed by decomposition of water in the electrolyte is stored, and when discharged, the required hydrogen is discharged into the electrolyte to be discharged. Electrical shorts of positive and negative electrodes and electrolytes of aqueous potassium hydroxide solution are absorbed, and the separators, which are polypropylene or polyamide-based non-woven fabrics, act as a channel through which ionic reactions occur. After that, the electrolyte is injected and sealed.

The charge and discharge reaction formula of the nickel metal hydride battery is as follows.

charge

Anode: Ni (OH) ₂ + OH ^- ⇔ NiOOH + H ₂ O

Discharge

charge

Negative _{electrode: M + H 2 O ⇔ MH} + OH -

Discharge

charge

M + Ni (OH) ₂ ⇔ MH + NiOOH

Discharge

In the above reaction formula, M represents a hydrogen storage alloy capable of absorbing and releasing hydrogen ions, and there are AB ₅ system using rare earth elements and AB ₂ system using Ti, Zr, V and the like. In the above formula, the positive electrode and the negative electrode of the nickel-metal hydride battery can be charged and discharged hundreds of times or more according to the above reaction formula.

When overcharging occurs during the reaction, oxygen is generated at the anode to oxidize the hydrogen storage alloy to shorten the battery life.

A binder that exhibits the ability to minimize deterioration by considering the volume change during the reaction and the stability in the strong alkaline liquid while maintaining a constant shape by binding the active material reactant and the conductive agent of the hydrogen storage alloy constituting the electrode plate. The application of is very important in battery development. There are several binders mentioned above, each of which has advantages and disadvantages, but excellent performance can be obtained by applying the contents of the present invention to the manufacture of the electrode plate used in the case of a square battery among the battery types.

Ethyl silicate applied to the present invention is a colorless transparent or pale yellow liquid having the structure of Formula 1, the viscosity is 3cps and the specific gravity is 1.05.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

EXAMPLE

Example 1

The positive electrode plate and the negative electrode plate inserted into the can in the wound state are manufactured by the same method as the conventional method.

CeCm-rich hydrogen storage alloy CeMmNi _3.55 Mn _0.4 Al _0.3 Co _0.75 containing a large amount of cesium was mixed with Ketjen Black in a weight ratio of 200: 1 using a conductive agent, and carboxymethyl cellulose (CMC) aqueous solution 1 After adding the weight% to make the viscosity 20,000cps, the mixture was stirred for 60 minutes, applied to a porosity 49% active material support called NPPS (Nickel Perforate Plate Steel), dried by hot air at 120 ° C. for 20 minutes, and the thickness of the coating film was 1 Ethyl silicate was coated to be within μm and then cut into a predetermined size to prepare a negative electrode. Then, NiOOH was used as an active material, and a conductive agent and an additive were added thereto, and a paste-type anode was prepared by filling a porous support called Ni-foam.

The positive and negative electrode plates prepared as described above were cut to a predetermined size through a cutting process, and the positive electrode was wrapped in a nonwoven fabric made of polypropylene so as not to come into contact with the negative electrode, and then inserted into the can having a predetermined size. In addition, 1.25 g of 31 wt% potassium hydroxide electrolyte was injected into the can, and a cap assembly was sealed in the upper opening thereof to prepare a 600 mAh square nickel-metal hydride battery and then tested for performance.

Example 2

CeMmNi _3.55 Mn _0.4 Al _0.3 Co _0.75 , which is a hydrogen storage alloy containing a large amount of cesium, was mixed with Ketjen Black at a weight ratio of 200: 1, and 1% by weight of an aqueous carboxymethyl cellulose solution and ethyl silicate were added to give a viscosity of 20,000 cps. After the preparation, the mixture was stirred for 60 minutes, applied to a porosity 49% active material support called NPPS, and dried at 120 ° C. for 20 minutes, and then cut to prepare a negative electrode. Then, NiOOH was used as an active material, and a conductive agent and an additive were added thereto to prepare a paste-type anode filled with a porous support called Ni-foam.

The positive and negative electrode plates prepared as described above were cut to a predetermined size through a cutting process, and the positive electrode was wrapped in a nonwoven fabric made of polypropylene so as not to come into contact with the negative electrode, and then inserted into the can having a predetermined size. In addition, 1.25 g of 31 wt% potassium hydroxide electrolyte was injected into the can, and a cap assembly was sealed in the upper opening thereof to prepare a 600 mAh square nickel-metal hydride battery and then tested for performance.

Comparative example

It was prepared in the same manner as in the above example, but the binder was used SBR (Stylene Butadiene Rubber), and the method of incorporation thereof was mixed and stirred with the input materials as in Example 2, and the conditions of assembly were carried out in the same manner. A square nickel-metal hydride battery was produced.

The nickel-hydrogen batteries prepared in Examples 1 and 2 and Comparative Examples were charged for 72 minutes with a current of 600 mAh, rested for 60 minutes, and then repeatedly discharged to 0.9 V with a current of 600 mAh.

Ethyl silicate used in the production of hydrogen storage alloy electrode forms a transparent silica film when coated on the surface of the electrode plate, shows excellent performance as a battery binder, and penetrates well between particles forming the electrode plate due to its high permeability. By coating with a large effect of inhibiting the falling off and expansion of particles can be produced a battery of long life.

Claims (6)

A binder for nickel hydride batteries containing ethyl silicate represented by the following formula (1). [Formula 1] N is an integer of 1-8. Hydrogen storage alloys; A conductive agent; Thickeners; Ethyl silicate; Active material slurry for the nickel hydrogen battery negative electrode containing. The active material for a nickel hydrogen battery negative electrode of claim 2, wherein the hydrogen storage alloy is 90 to 100% by weight, the conductive agent is 0.1 to 10% by weight, the thickener is 0.1 to 4% by weight, and the ethyl silicate is 0.1 to 10% by weight. Slurry. Preparing an active material slurry for nickel-hydrogen battery negative electrode including a hydrogen storage alloy, a conductive agent, a thickener, and ethyl silicate; Applying the active material slurry to a support and drying with hot air at 120 ° C. for 20 minutes; A method for manufacturing a negative electrode plate for a nickel hydride battery comprising a step. The negative electrode plate of claim 4, wherein the hydrogen storage alloy is 90 to 100% by weight, the conductive agent is 0.1 to 10% by weight, the thickener is 0.1 to 4% by weight, and the ethyl silicate is 0.1 to 10% by weight. Way. Preparing a slurry by mixing the hydrogen storage alloy and the conductive agent and adding and stirring the thickener; The slurry is applied to an active material support and dried with hot air at 120 ° C. for 20 minutes; Coating ethyl silicate on the dry active material support such that the thickness of the coating film is 0.1 to 10 μm; A method for manufacturing a negative electrode plate for a nickel hydride battery comprising a step.