KR100384384B1 - Lithium ion polymer battery having superior temperatrure property and process for preparing the same - Google Patents

Abstract

The present invention relates to a lithium ion polymer battery having excellent temperature characteristics, and more particularly, to a lithium ion polymer battery including an electrolyte and an electrode binder made of polyvinylidene fluoride homopolymer.

The present invention provides a negative electrode comprising a negative electrode binder based on a polyvinylidene fluoride homopolymer (PVdF homopolymer) at the center, and a polyvinylidene fluoride homopolymer (PVdF homopolymer) based electrolyte on the outer both sides of the negative electrode and the outer both sides of the electrolyte. A laminate including a cathode including an anode binder based on a polyvinylidene fluoride homopolymer (PVdF homopolymer) and thermally bonded in a structure of a cathode-electrolyte-cathode-electrolyte-anode and an electrolyte solution filled in the battery substrate A lithium ion polymer battery and its manufacturing method are provided.

The lithium ion polymer battery produced by the present invention is an electrolyte and an electrode binder based on an excellent polyvinylidene fluoride homopolymer (PVdF homopolymer) which is stable even when impregnated with an electrolyte solution and is not dissolved even when impregnated with an electrolyte solution containing dimethyl carbonate. Because it is manufactured to include the excellent temperature characteristics at low and high temperatures, especially the high temperature characteristics exhibited excellent characteristics that the capacity after 50 charge-discharge at C rate rate at 60 ℃ maintains 92% of the initial room temperature capacity .

Description

Lithium ion polymer battery having excellent temperature characteristics and its manufacturing method {LITHIUM ION POLYMER BATTERY HAVING SUPERIOR TEMPERATRURE PROPERTY AND PROCESS FOR PREPARING THE SAME}

[Industrial use]

The present invention relates to a lithium ion polymer battery having excellent temperature characteristics, and more particularly, to a lithium ion polymer battery comprising an electrolyte and an electrode binder made of polyvinylidene fluoride homopolymer, and a method of manufacturing the same.

[Prior art]

In general, a battery used in a portable electronic device should have excellent characteristics at high and low temperatures depending on the use conditions as well as the room temperature characteristics. In portable electronic devices, batteries are mostly contained inside or attached to electronic devices. Electronic devices inevitably generate heat during operation, resulting in an increase in temperature.

This increase in temperature inside the electronic device has a great effect on the battery. In particular, in the case of the equipment with a large amount of current, a large amount of heat is generated by the current flowing not only in the electronic device but also in the battery itself. Currently, notebook computers have a limited amount of current because they use a lot of current and increase their temperature. Therefore, the development of a battery having excellent characteristics at high temperatures is urgently required.

Batteries that meet these demands have a higher voltage than lithium batteries and nickel-metal hydride batteries that can reduce the amount of current. Among the lithium batteries, polymer batteries with relatively low electrolyte content are safe at high temperatures. It is also excellent in high temperature characteristics.

The present invention provides a lithium ion polymer battery having excellent temperature characteristics in accordance with such a demand.

A lithium ion polymer battery consists of a positive electrode, a negative electrode, a polymer electrolyte, and electrolyte solution. The electrode consists of a current collector and an electrode film, the electrode film consists of an electrode active material, a conductive agent and an electrode binder, and the electrolyte consists of a polyvinylidene fluoride homopolymer (PVdF homopolymer) and an inert filler. Impregnated

Since polyvinylidene fluoride (PVdF) is chemically and electrochemically stable, it is used as an electrode binder of a lithium ion battery, an electrode binder of an lithium ion polymer battery, and an electrolyte. Polyvinylidene fluoride (hereinafter referred to as PVdF) can be classified into copolymers and homopolymers. PVdF copolymers are vinylidene fluoride (PVdF) and haxa fluoro propylene (HFP). This copolymer is used as an electrode binder in electrolytes and lithium ion batteries in lithium ion polymer batteries, and PVdF homopolymers are used as electrode binders in lithium ion batteries.

In order to have excellent temperature characteristics of the battery, it is necessary to use a stable electrolyte solution having high ionic conductivity regardless of temperature. Since the electrolyte used in the lithium ion battery does not have such characteristics alone, a mixed solvent is used.

The electrolyte solution has a high viscosity at low temperatures, resulting in a decrease in ionic conductivity. An electrolyte solution containing dimethyl carbonate has a low viscosity, and thus has excellent ion conductivity at low temperatures.

However, dimethyl carbonate (DMC), which has excellent temperature characteristics, has problems in use in lithium ion polymer batteries. This is because the lithium ion polymer battery uses PVdF copolymer, because when it is impregnated with an electrolyte containing dimethyl carbonate, the electrolyte absorbs excessively and swells. In particular, when the temperature of the battery rises above 40 ° C., the amount of absorbing electrolyte increases further, which causes the battery to expand and eventually causes the electrode and the structure of the battery to be broken. For this reason, in lithium ion polymer batteries, greater restrictions are imposed on the selection of the electrolyte solution.

On the other hand, the electrode is composed of an active material, a conductive agent, and a polymer that is a support thereof. When the electrolyte enters the electrode, the electrode absorbs and swells. When the binder of the electrode swells, the binding force between the active material, the conductive agent, and the polymer becomes weak, and the distance increases. This not only increases the volume of the electrode but also dramatically decreases the electronic conductivity of the electrode, thereby deteriorating the battery performance.

Since the degree of impregnation swelling of the binder in the electrolyte solution is larger than that of the homopolymer, the homopolymer is advantageous as the binder of the electrode. Especially at high temperatures, copolymers are difficult to use because of their great swelling.

The problem is solved by replacing the PVdF copolymer substrate with a PVdF homopolymer substrate. This is because the PVdF homopolymer is stable to most electrolytes containing dimethyl carbonate, and especially the binder of the electrode is safe even at high temperatures.

Prior art on this is published by Tsuchida et al. (Electrochemica Acta, Vol. 28, No. 5, pp 591-599, 1983 and No. 6, 833-837, 1983). Low molecular weight PVdF homopolymers were used, but it was considered impossible to apply PVdF homopolymers to polymer electrolytes because the manufacturing process was difficult, the films were very uneven and the physical strength was too weak.

Since then, Chushida et al. Prepared a polymer electrolyte using PVdF-PTFE copolymer instead of a PVdF homopolymer, but the electrolyte film was also crystallized and nonuniform, and its physical strength was inadequate for application to a battery.

Subsequently, a hybrid polymeric electrolyte using PVdF as described in Bellcore, U.S. Patent No. 5,296,318 was known. They experimented with PVdF homopolymers and PVdF copolymers, but the results were poor.

U.S. Pat. No. 5,418,091 also describes a battery manufacturing method of better performance, wherein the polymer uses PVdF copolymer. In this case, an electrode and an electrolyte film are prepared using a plasticizer, and a battery is manufactured by thermal bonding. Then, a plasticizer is extracted with an extraction solvent to form micropores, and the micropores are impregnated with an electrolyte solution to fabricate a battery. That is, the polymer used PVdF copolymer, dibutyl phthalate (DBP) as a plasticizer, and an inert filler, fumed silica, was added to increase the mechanical strength of the film. It is explained that the uniformity and mechanical strength are excellent at, and the ionic conductivity is superior to 10 ^-3 S / cm at room temperature.

Since then, Belcoa has applied for a number of patents, such as US Patent No. 5,470,357, in conjunction with this patent, and the contents of the present invention describe the application of polymer electrolytes using this type of electrolyte.

As described above, it can be seen that the above-mentioned prior arts are unable to manufacture electrolytes having excellent performance with PVdF homopolymers themselves, so that the polymers are replaced with PVdF copolymers to prepare electrolytes and batteries with excellent characteristics. However, PVdF copolymers are not only able to use an electrolyte solution containing dimethyl carbonate exhibiting excellent ionic conductivity at low temperatures, but also have various problems at high temperatures.

In the example of the prior art, when the mixed solution is prepared using the PVdF homopolymer, it is hard to prepare a film by gelling when the temperature is lowered in the coating process, and even though the film is prepared before the temperature is lowered, crystallization occurs in the electrolyte, whereby lithium salt is separated and uniform. I could not make a film. In order to manufacture a lithium ion polymer battery having excellent temperature characteristics, a PVdF homopolymer should be used. In this case, a method of manufacturing a film having a uniform composition and an easy manufacturing process is required.

The present invention solves the problems and requirements of the prior art, a lithium ion polymer secondary battery comprising an electrode binder of an electrolyte, a negative electrode, a positive electrode based on PVdF homopolymer having excellent high temperature characteristics and free electrolyte selection, and a method of manufacturing the same. The purpose is to provide.

1 is a diagram illustrating a process of manufacturing an electrode by thermally bonding a current collector and an electrode film of the present invention in a laminate bonding machine provided with heating rolls up and down.

2 schematically illustrates the structure of the cathode electrode of the present invention.

3 schematically illustrates the structure of the anode electrode of the present invention.

4 schematically illustrates the structure of a lithium ion polymer battery of the present invention.

5 is a diagram illustrating battery characteristics of the lithium ion polymer battery of the present invention charged and discharged at 60 ° C. at a C rate.

Reference numeral 1 is an electrode film; 2 is the first applied current collector; 3 is a heating roll; 4 is heat bonding progress direction; 5 is a thermally bonded electrode; 6 is a primary coated copper current collector; 7 is a negative electrode film; 8 is a primary coated aluminum current collector; 9 is a positive electrode film; 10 is an electrolyte; 11 is a thermally bonded cathode; 12 is a thermally bonded anode.

[Means for solving the problem]

The present invention provides a method for producing a lithium ion polymer secondary battery comprising an electrode binder of an electrolyte, a negative electrode, and a positive electrode based on a PVdF homopolymer.

In detail, the present invention is a cathode, a lamination assembly of the negative electrode film-copper current collector-cathode film shown in FIG. 2, a positive electrode, an electrolyte film, and an electrolyte which is a lamination assembly of the positive electrode film-aluminum current collector-anode film shown in FIG. The manufacturing method of the lithium ion polymer battery comprised is provided.

The present invention also provides a method for producing a lithium ion polymer battery in which an electrolyte solution is impregnated into a lamination assembly having a form of an anode-electrolyte-cathode-electrolyte-anode as shown in FIG. 4.

In addition, the present invention uses the solubility characteristics of the PVdF homopolymer to prepare a stable coating mixture solution, which does not solidify in a gel state even at room temperature, to prepare a film from the mixed solution, to prepare a battery from the film to include an electrolyte solution therefrom A method of manufacturing a lithium ion polymer battery is provided.

The present invention also provides a lithium ion polymer secondary battery comprising a PVdF homopolymer based electrolyte, a PVdF homopolymer based negative electrode, and a positive electrode binder.

In the method of the present invention, a solvent having high solubility is selected by reflecting the solubility of the solvent in the PVdF homopolymer in preparing a mixed solution, and a solvent having a low boiling point is selected by mixing the two solvents. By dissolving the polymer in a mixed solvent by using the synergistic effect of utilizing the properties of each solvent to produce the required electrolyte film and electrode film.

The mixed solution prepared by this method is stable because of its high solubility at room temperature, and the drying temperature of the film after coating is easy to manufacture the film, and also prevented plasticizer in the film from evaporating during the drying process. In addition, the polymer electrolyte and electrode binder are amorphous, very uniform film, excellent mechanical strength and excellent ion conductivity.

In addition, lithium ion polymer batteries prepared by including these electrolytes, electrode binders, and electrolytes have excellent low and high temperature characteristics.

To this end, the present invention

a) preparing a negative electrode comprising a negative electrode binder based on PVdF homopolymer;

b) preparing a positive electrode comprising a positive electrode binder based on PVdF homopolymer;

c) preparing an electrolyte film based on PVdF homopolymer;

d) Place the electrolyte film on the outer both sides of the negative electrode and the heating roll is installed up and down

Heat bonding at the temperature of 135 ~ 140 ℃ in laminate jointer

Preparing a conjugate of the film;

e) Position the anode on both sides of the assembly of anode and electrolyte film and heating roll up and down

Thermal bonding at 135-150 ° C

Preparing a battery substrate;

f) solvent extraction of the plasticizer contained in the thermally bonded battery-based film

A thermal junction battery in which micropores are formed by forming micropores in a film of a paper substrate

Preparing a substrate;

g) heat in which micropores are formed in a glove box filled with argon gas

A battery is prepared by impregnating and injecting a bonded battery base material into an electrolyte solution.

system; And

h) packaging and sealing the battery impregnated with the electrolyte in a packing pack;

It provides a method for producing a lithium ion polymer battery comprising a.

The cathode of step a) is

Iv) dissolving the PVdF homopolymer in a mixed solvent followed by plasticizer, conductive carbon and

Mixing the active material with the solution and stirring to prepare a mixed solution;

Ii) apply the mixed solution onto a release paper, and apply the applied film

Drying to a temperature of 80 to 95 ° C. to produce a coating film; And

코팅) Place the coating film on the outer both sides of the pretreated current collector and heat up and down

Laminator splicer with roll is installed at 140 ~ 160 ℃

Step of preparing a cathode by thermal bonding

It is prepared by a method comprising a.

In step iii) of the anode production method, the molecular weight of the PVdF homopolymer is 100,000 to 1,000,000; The mixed solvent is selected from the group consisting of a mixed solvent of dimethylformamide and acetone, and a mixed solvent of dimethylacetamide and acetone; The mixing ratio of the dimethylformamide and the acetone mixed solvent is preferably 5: 95-50: 50 in volume% ratio, more preferably 15: 85-40: 60 in volume% ratio; The mixing ratio of the acetone mixed solvent of dimethylacetamide is preferably 5:95 to 40:60 in volume% ratio, more preferably 15:85 to 40:60 in volume% ratio; The plasticizer is selected from the group consisting of dibutylthyl phthalate, dimethyl adipate, ethylene carbonate and propylene carbonate; The active material is selected from the group consisting of graphite and coke, which is a hard carbon; The mixed solution composition ratio is 8-18 wt% of PVdF homopolymer, 10-26 wt% of plasticizer, 3-7 wt% of conductive carbon, 52-79 wt% of active material, and the solid content concentration of the mixed solution is preferably 35-65 wt%. .

In step ii) of the manufacturing method of the negative electrode, the thickness of the coating film is preferably 100 to 160 μm.

The current collector pretreated in step iii) of the cathode manufacturing method is a copper expanded mesh, and the pretreatment is performed by washing the copper mesh with acetone and then immersing the surface in an etching solution of strong acid to oxidize the surface. After washing with distilled water and drying, the solid content concentration of composition comprising 40 to 75% by weight of PVdF homopolymer, 10 to 30% by weight of plasticizer, 5 to 30% by weight of conductive carbon, 0.5 to 3% by weight of oxalic acid is 0.5 to 5 It is preferable to carry out the primer coating which spray-mixes the mixed solution of the weight% to 10 micrometers or less, more preferably 5 micrometers or less, and hot-air-drys it at the temperature of 100-250 degreeC.

The anode of step b) is

Iv) dissolving the PVdF homopolymer in a mixed solvent followed by plasticizer, conductive carbon and

Mixing the active material with the solution and stirring to prepare a mixed solution;

Ii) apply the mixed solution onto a release paper, and apply the applied film

Drying to a temperature of 85 to 95 ° C. to produce a coating film; And

코팅) Place the coating film on the outer both sides of the pretreated current collector and heat up and down

Laminator splicer with roll is installed at 140 ~ 160 ℃

Step of preparing a cathode by thermal bonding

It is prepared by a method comprising a.

In step iii) of the positive electrode production method, the molecular weight of the PVdF homopolymer is 100,000 to 1,000,000; The mixed solvent is selected from the group consisting of a mixed solvent of dimethylformamide and acetone, and a mixed solvent of dimethylacetamide and acetone; The dimethylformamide and the acetone mixed solvent is preferably 5: 95 to 50: 50 in a volume% ratio, more preferably 15: 85 to 40: 60 in a volume% ratio; The mixing ratio of the acetone mixed solvent of dimethylacetamide is preferably from 5:95 to 40:60 in volume% ratio, more preferably from 15:85 to 40:60 in volume% ratio; The plasticizer is selected from the group consisting of dibutylthyl phthalate, dimethyl adipate, ethylene carbonate and propylene carbonate; The active material is selected from the group consisting of lithium cobalt oxide (LiCoO ₂ ) and lithium manganese oxide (LiMn ₂ O ₄ ); The mixed solution composition ratio is 8 to 17 parts by weight of the PVdF homopolymer, 10 to 25 parts by weight of the plasticizer, 5 to 12 parts by weight of the conductive carbon, and 51 to 78 parts by weight of the active material, and the solid content concentration of the mixed solution is preferably 35 to 65% by weight. .

In step ii) of the manufacturing method of the positive electrode, the thickness of the coating film is preferably 80 to 140 μm.

The pre-treated current collector in step iii) of the method of manufacturing the positive electrode is an aluminum expanded mesh, and the pre-treatment is performed by washing the aluminum mesh with acetone and then supporting the oxide on the surface by supporting it in an etching solution of strong acid. After the removal, the mixture was washed with distilled water, dried, and mixed with 40 to 75 wt% of PVdF homopolymer, 10 to 30 wt% of plasticizer, and 5 to 30 wt% of conductive carbon, and having a solid content of 0.5 to 5 wt%. It is preferable to carry out primer coating which spray-coating to thickness of 10 micrometers or less, More preferably, 5 micrometers or less and carrying out hot air drying at the temperature of 100-250 degreeC.

The electrolyte of step c) is

Viii) plasticizer and inert filler after dissolving PVdF homopolymer in mixed solvent

Mixing the mixture with the solution and stirring to prepare a mixed solution; And

Ii) apply the mixed solution onto a release paper, and apply the applied film

Drying to prepare a coating film;

It is prepared by a method comprising a.

In step iii) of the electrolyte preparation method, the molecular weight of the PVdF homopolymer is 100,000 to 1,000,000; The mixed solvent is selected from the group consisting of a mixed solvent of dimethylformamide and acetone, and a mixed solvent of dimethylacetamide and acetone; The dimethylformamide and the acetone mixed solvent is preferably 5: 95 to 50: 50 in a volume% ratio, more preferably 15: 85 to 40: 60 in a volume% ratio; The mixing ratio of the acetone mixed solvent of dimethylacetamide is preferably from 5:95 to 40:60 in volume% ratio, more preferably from 15:85 to 40:60 in volume% ratio; The plasticizer is selected from the group consisting of dibutyl phthalate, dimethyl adipate, ethylene carbonate, and propylene carbonate; The mixing amount is 75 to 120 parts by weight based on 100 parts by weight of the PVdF homopolymer; The inert filler is selected from the group consisting of fumed silica, alumina and zeolite, and the mixing amount is 3 to 30 parts by weight based on 100 parts by weight of PVdF homopolymer, and the surface of the inert filler is substituted with a hydrophobic group. desirable.

In step ii) of the electrolyte manufacturing method, the thickness of the coating film is preferably 20 to 50 μm.

The solvent extraction of step f) uses diethyl ether as a solvent, and the prepared battery substrate is put into a solvent and extracted for 30 minutes, and then extracted with a new solvent for 30 minutes and then dried.

The electrolyte of step g) is selected from the group consisting of a mixture of ethylene carbonate and diethyl carbonate, a mixture of ethylene carbonate and dimethyl carbonate, a mixture of ethylene carbonate and ethyl methyl carbonate, a mixture of ethylene carbonate and dimethyl carbonate and ethyl methyl carbonate. And 0.5 to 2 moles of lithium hexafluoride (LiPF ₆ ) salt.

In the present invention, a laminate negative electrode including a PVdF homopolymer-based negative electrode binder is positioned at the center thereof, and an electrolyte film based on the PVdF homopolymer is positioned on both outer surfaces of the negative electrode, and a positive electrode binder based on the PVdF homopolymer is disposed on the outer both sides of the electrolyte. A mixed liquid of ethylene carbonate and diethyl carbonate, a mixed liquid of ethylene carbonate and dimethyl carbonate, a mixed liquid of ethylene carbonate and ethyl methyl carbonate, a mixed liquid of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate Provided is a lithium ion polymer battery selected from the group consisting of an electrolyte solution containing 0.5 to 2 moles of lithium hexafluoride (LiPF ₆ ) salt.

In the negative electrode, a copper current collector is disposed inside, and a negative electrode including 68 to 88 parts by weight of an active material of graphite or hard carbon, 5 to 12 parts by weight of conductive carbon, and 8 to 21 parts by weight of PVdF homopolymer is located on both sides thereof. The positive electrode is an active material selected from the group consisting of lithium cobalt oxide (LiCoO ₂ ) or lithium manganese oxide (LiMn ₂ O ₄ ) on the both sides of the aluminum current collector inside the positive electrode, conductive carbon 6 A positive electrode comprising ˜14 wt% and 7 to 21 wt% of PVdF homopolymer is positioned and thermally bonded.

The above object of the present invention and the characteristics and advantages of the present invention will become apparent from the following detailed description.

The present invention seeks to solve the problems of the prior art in the production of lithium ion polymer batteries comprising an electrolyte and an electrode binder based on PVdF homopolymer.

As a result of understanding the characteristics of the lithium ion polymer battery manufactured by the manufacturing method of the present invention, lithium cobalt oxide is used as the active material in the positive electrode and graphite is used as the active material in the negative electrode, and the internal resistance of the battery is about 30 to 45 mA / cm 2, The cycle characteristics maintained 92% of the initial capacity after 100 charge / discharge cycles in the range of 4.2-3.0 V at a C / 5 rate. The use of hard carbon (coke) as the active material in the negative electrode and lithium manganese oxide as the active material in the positive electrode increased the internal resistance to 35 to 55 kW / cm 2.

The use of hard carbon as the active material in the negative electrode and lithium manganese oxide as the active material in the positive electrode maintains 84% of the initial capacity after 100 cycles of charging and discharging at a C / 5 rate of 4.5 to 2.5 V. It was.

In addition, the temperature characteristics of the battery were excellent in both low temperature and high temperature characteristics, and particularly in the high temperature characteristics. That is, it showed excellent characteristics of maintaining 92% of the initial room temperature capacity after charging and discharging 50 times at 60 ° C. at a C rate rate.

The present invention will be described in more detail with reference to the following Examples, Preparation Examples and Comparative Examples, which are intended to illustrate the present invention, but the present invention is not limited thereto.

EXAMPLE

In the embodiment of the present invention, the PVdF homopolymer was selected by using a relatively high molecular weight PVdF homopolymer (Solef Solef 1015 or Elf Auto chem 301F), and the plasticizer used a general dibutyl butyrate (DBP), electrolyte As an example of filler, only examples using fumed silica (TS-530 manufactured by Cabot or Aerosil R202 manufactured by Degusa) whose surface is substituted with a hydrophobic group are described. In addition, both the inert filer and the raw material for electrode production were dried in a vacuum drying furnace for at least 24 hours before use to completely remove the contained moisture.

In addition, the reaction vessel was sealed with nitrogen gas and an oil bath was used to keep the reaction temperature constant. When the experiment volume was more than 500 ml, an stirrer was used, and it was completely sealed and the temperature was kept constant. A reaction vessel was used, and a coater was a lab dryer of Matis.

As a device for measuring the characteristics of the electrolyte film, a ruler capable of accurately measuring the change in the size of the electrolyte film up to 0.1 mm was used, and a thickness meter capable of measuring the thickness of the film up to 1 μm was used. In addition, the ion conductivity was measured using a potentiometer (potentiomer Model 273 from EG G) and an impedance analyzer (Solartron SI 1260 Impedance Analyzer).

The characteristics of the electrode were confirmed by the evaluation of the half cell and the charge / discharge test. The characteristics of the battery were the charge / discharge test, and a cyclic voltameter, an impedance analyzer, and a charge / discharge tester were used.

Example 1

Preparation of Electrolyte Film

In a closed reaction vessel, 9 g of PVdF homopolymer (solvey 1015) was added to 100 ml of a mixed solvent having a mixing ratio of dimethylacetamide and acetone in a volume ratio of 25: 75. After dissolving in to prepare a transparent solution, 10 g of dibutylphthalate as a plasticizer and 1 g of fumed silica as an inert filler were added thereto, and further stirred for 30 to 60 minutes while maintaining the temperature to obtain a uniformly dispersed transparent solution. , While maintaining the temperature as it is to open the lid of the reaction vessel to completely remove the bubbles remaining in the solution to prepare a mixed solution.

The bubble-free solution was coated and applied onto a release paper surface-treated with silicon using a coater, and dried in a drying furnace to remove the release paper to prepare a film. Here, the applicator (mathis lab dryer) was adjusted to have a constant thickness by using a micro thickness meter (micro thickness meter) on the left and right sides of the applicator, the coating is 0.5 while preventing the pin hole (pin hole) is generated in the film The coating film thickness after drying was apply | coated so that it might become 40 micrometers at the application | coating speed of -1 m / min.

Preparation of Cathode Film

In a closed reaction vessel, 10 g of PVdF homopolymer (solef 1015 from Soldy) was added to 100 ml of a mixed solvent having a mixing ratio of dimethylacetamide and acetone in a volume ratio of 25: 75, and the temperature was kept at 60 ° C while stirring to obtain a polymer. After dissolving in, to prepare a transparent solution, 16 g of plasticizer dibutyl phthalate and 2.5 g of conductive carbon (super-P) were added and dispersed therein, followed by 40 g of graphite (MCMB 10-28 manufactured by Osaka Gas Co., Ltd.) as an active material. 5 g was added at 5 minute intervals and stirred for 30 to 60 minutes while maintaining the temperature to prepare a uniformly dispersed mixed solution.

The bubble-free solution was coated on a release paper surface-treated with silicon using a coater, dried in a drying furnace, and then removed from the release paper to prepare a film. Here, the applicator (mathis lab dryer) was adjusted to have a constant thickness by using a micro thickness meter (micro thickness meter) on the left and right sides of the applicator, the coating is 0.5 while preventing the pin hole (pin hole) is generated in the film The coating film thickness after drying was apply | coated so that it might become 120 micrometers at the application rate of -1 m / min.

In order to evaluate the prepared negative electrode film, the plasticizer was extracted with solvent diethyl ether as in the electrolyte film, and impregnated into the electrolyte solution to measure the amount of electrolyte impregnation and the size of the film after impregnation. As a result of the test, the amount of electrolyte impregnation was 150-180%, and the size of the film after impregnation, which is the size restoring force of the film, was 99-100%.

Fabrication of Anode Film

In a closed reaction vessel, 10 g of PVdF homopolymer (solef 1015 from Soldy) was added to 100 ml of a mixed solvent having a mixing ratio of dimethylacetamide and acetone in a volume ratio of 25: 75, and the temperature was kept at 60 ° C while stirring to obtain a polymer. After dissolving in, to prepare a transparent solution, 14 g of plasticizer dibutyl phthalate and 5.5 g of conductive carbon (super-P) were added and dispersed therein, followed by lithium cobalt oxide (LiCoO ₂₎ having an average particle size of 10 μm as an active material. ) 40 g was added in 5 g portions at 5 minute intervals and further stirred for 30 to 60 minutes while maintaining the temperature to prepare a uniformly dispersed mixed solution.

The bubble-free solution was coated and applied onto a release paper surface-treated with silicon using a coater, and dried in a drying furnace to remove the release paper to prepare a film. Here, the applicator (mathis lab dryer) was adjusted to have a constant thickness by using a micro thickness meter (micro thickness meter) on the left and right sides of the applicator, the coating is 0.5 while preventing the pin hole (pin hole) is generated in the film The coating film thickness after drying was apply | coated so that it might become 85-90 micrometers at the application rate of -1 m / min.

In order to evaluate the produced positive electrode film, the plasticizer was extracted with solvent diethyl ether as in the electrolyte film, and impregnated into the electrolyte solution to measure the amount of electrolyte solution impregnation and the size of the film after impregnation. As a result of the test, the amount of electrolyte impregnation was 130 to 160%, and the size of the film after impregnation, which is the size restoring force, was 100%.

Current collector pretreatment

For the negative electrode current collector, a copper expanded mesh is used, and for the positive electrode current collector, an aluminum expanded mesh is used to clean and apply the primary coating (Al Expended Mesh). primer coating).

In the washing, each current collector is washed with acetone to remove organic substances adsorbed on the surface, and then immersed in an etching solution of strong acid to oxidize the surface and immediately washed several times with pure water to completely remove and dry the acid.

The initial coating was 15 wt% of conductive carbon (Super-P), 60 wt% of PVdF homopolymer (Kynar 761 manufactured by Autochem) as a binder polymer, 25 wt% of dibutyl phthalate (DBP) as a plasticizer, and a solid concentration of 0.1 The mixed solution of ˜5% by weight was spray-coated to the washed current collector to a thickness of 5 μm or less and dried at a drying temperature of 240 to 250 ° C. in a hot air dryer.

The negative electrode current collector was spray-coated by adding 1 to 3% of an organic weak acid, oxalic acid, to the mixed solution.

Cathode manufacturing

The negative electrode film prepared above was thermally bonded in the form of a laminate of a negative electrode film-copper current collector-negative film to a current collector that was washed and primed coated on the copper expanded mesh. The thermal bonding device is a laminator in which temperature and pressure are constantly adjustable and heating rolls are installed up and down. Cathode bonding A cathode film was placed on both sides with a current collector interposed therebetween to simultaneously bond. The junction temperature was adjusted to constant temperature at 145 ~ 155 ℃. When the temperature is higher or the pressure at the time of bonding, the electrode shape is distorted, so that the bonding while controlling constantly.

The cathode, thus formed as a junction electrode, had excellent bonding and low resistivity of the electrode. The junction negative electrode was evaluated by the half cell experiment to evaluate the electrochemical properties of the negative electrode.

Anode manufacturing

The positive electrode film prepared above was heat-bonded in the form of a laminate of a positive electrode film-aluminum current collector-anode film to a current collector pre-treated with the aluminum expanded mesh and washed with a primer coating. The thermal bonding device is a laminator in which temperature and pressure, such as cathode production, are constantly adjustable and heating rolls are installed up and down. At the time of positive electrode bonding, the positive electrode film was placed on both sides with the pretreated current collector in between to be simultaneously bonded at the same time. The junction temperature was adjusted to constant temperature at 145 ~ 155 ℃. When the temperature is higher or the pressure at the time of bonding, the electrode shape is distorted, so that the bonding while controlling constantly.

The positive electrode, thus formed as a bonding electrode, was excellent in bonding and had low resistivity. The positive electrode of the junction was evaluated by the half cell experiment to evaluate the electrochemical properties of the positive electrode.

Bonding Cathode and Electrolyte Film

The negative electrode prepared above and the 40 μm electrolyte film were thermally bonded in the form of a laminate of an electrolyte film-cathode-electrolyte film.

The thermal bonding apparatus is a laminator in which temperature and pressure can be adjusted uniformly and a heating roll is installed up and down like the cathode manufacturing.

The electrolyte film was placed on both sides with the negative electrode interposed therebetween to simultaneously bond them together. If the bonding is good, the electrolyte film will be dissolved and transparent, and if the temperature is raised above the proper value or the pressure is increased, the film will weaken and cause an internal short circuit. Therefore, the bonding temperature is controlled to 130 ~ 140 ℃ and the pressure is kept constant. It was.

Battery junction

The battery substrate was manufactured by thermally bonding a cathode, an electrolyte film assembly, and the cathode prepared above to a laminate of a cathode, an anode, and an electrolyte assembly.

The thermal bonding device is a laminator in which temperature and pressure, such as cathode production, are constantly adjustable and heating rolls are installed up and down.

The positive electrode was placed on both sides with the negative electrode and the electrolyte film assembly therebetween to be simultaneously bonded at the same time. The junction temperature was controlled to be constant at 135-150 ° C. and the pressure was constant.

Solvent extraction

Using a diethyl ether as a solvent to the battery substrate prepared above, the plasticizer contained in the film of the battery substrate was extracted so that micropores were formed on the film. This extraction was carried out for 30 minutes in the battery substrate in the extraction solvent, and then extracted again for 30 minutes in a fresh extraction solvent and dried for 15 minutes under conditions of room temperature vacuum.

Electrolyte Impregnation

A mixed electrolyte solution of ethylene carbonate and ethyl methyl carbonate containing 1 mole of lithium hexafluoride (LiPF ₆ ) salt in a glove box filled with argon gas in a battery substrate in which micropores are formed by the plasticizer extraction, and ethylene carbonate and The battery was prepared by impregnating the mixture of ethylmethyl carbonate and dimethyl carbonate for 1 hour.

Packing

The battery prepared above was sealed with a battery pack to prepare a battery that can finally be used.

The performance of the battery thus prepared was measured by measuring the internal resistance of the battery using an impedance analyzer, and the temperature characteristics, speed characteristics and life characteristics of the battery using a charge and discharge tester.

The internal resistance of the battery was measured after sealing for 2 hours after the battery was manufactured, and the life characteristics were 50 times by charging and discharging at room temperature to 4.2 to 3.0 V at a C / 5 rate using a standard method of battery evaluation. The dose at was compared to the initial dose. The rate characteristic was discharged while converting the C rate to compare the capacity with the capacity at the C / 5 rate.

The temperature characteristics are charged at room temperature at C / 5 rate for high temperature characteristics and discharged at 60 ° C. to compare the capacity with the capacity at room temperature C / 5 rate, and at room temperature at C / 5 rate for low temperature characteristics and at low temperature. Discharge at a rate of 1 / 10C to compare the capacity with the capacity at room temperature C / 5 rate. The results are shown in Table 1.

In addition, the high temperature characteristics were excellent, but even after charging and discharging at 60 ° C. at a rate of 50 C, the capacity maintained 92% of the initial capacity after 50 cycles. The results are shown in FIG.

Example 2

A battery was manufactured in the same manner as in Example 1 except that the active material was changed to lithium manganese oxide in the production of the positive electrode film.

As described in Example 1, the performance of the battery thus prepared was measured using an impedance analyzer, and the temperature, speed, and life characteristics of the battery were measured using a charge / discharge tester. The results are shown in Table 1.

Example 3

A battery was manufactured in the same manner as in Example 1 except that the active material was changed to hard carbon in the production of the negative electrode film.

As described in Example 1, the performance of the battery thus prepared was measured using an impedance analyzer, and the temperature, speed, and life characteristics of the battery were measured using a charge / discharge tester. The results are shown in Table 1.

Example 4

A battery was manufactured in the same manner as in Example 1 except that the active material was changed to hard carbon in the production of the negative electrode film, and the active material was changed to lithium manganese oxide in the production of the positive electrode film.

As described in Example 1, the performance of the battery thus prepared was measured using an impedance analyzer, and the temperature, speed, and life characteristics of the battery were measured using a charge / discharge tester.

The results are shown in Table 1.

TABLE 1

division Example 1 Example 2 Example 3 Example 4 Active material type cathode Graphite Graphite Hard carbon Hard carbon anode Lithium cobalt oxide Lithium manganese oxide Lithium cobalt oxide Lithium manganese oxide Internal resistance (Ω / ㎠) 30 to 45 40-55 35-50 40-55 Life Characteristics (%) 92 87 91 86 Speed characteristic (%) 88 84 90 86 High temperature characteristics (%) 92 86 91 87 Low temperature characteristics (%) 83 84 85 86

The lithium ion polymer battery produced by the present invention is characterized by an electrolyte and an electrode based on an excellent polyvinylidene fluoride homopolymer (PVdF homopolymer) which is stable even when impregnated with an electrolyte and insoluble even when impregnated with an electrolyte containing dimethyl carbonate. The battery containing was produced, and the temperature characteristic in low temperature and high temperature is excellent.

In particular, the high temperature characteristics were excellent, and the capacity after 50 charge-discharge cycles at 60 ° C. at a C rate showed an excellent characteristic of maintaining 92% of the initial room temperature capacity.

Claims (26)

In the manufacturing method of a lithium ion polymer battery, a) a negative electrode based on a polyvinylidene fluoride homopolymer (PVdF homopolymer) Preparing a negative electrode including a binder; b) Anode based on polyvinylidene fluoride homopolymer (PVdF homopolymer) Preparing a positive electrode including a binder; c) Electrolysis based on polyvinylidene fluoride homopolymer (PVdF homopolymer) Preparing a quality film; d) Place the electrolyte film on the outer both sides of the negative electrode and the heating roll is installed above and below Heat bonding at the temperature of 135 ~ 140 ℃ in laminate jointer Preparing a conjugate of the film; e) Place the positive electrode on both sides of the assembly of negative electrode and electrolyte film and heating roll up and down Heat bond at the junction temperature of 135 ~ 150 ℃ Preparing a base material; f) solvent extraction of the plasticizer contained in the thermally bonded battery-based film Before thermal bonding in which micropores are formed by forming micropores in the films of the substrate. Preparing a base material; g) The micropores are formed in a glove box filled with argon gas. The thermally bonded battery substrate by impregnating the electrolyte solution and injecting the electrolyte solution Preparing a; And h) packing and sealing the battery in which the electrolyte is injected into a packing pack system How to include. The method of claim 1 The cathode of step a) is Iii) for mixing polyvinylidene fluoride homopolymer (PVdF homopolymer) After dissolving in a medium, the plasticizer, the conductive carbon and the active material are mixed in a solution and Preparing a mixed solution; Ii) apply the mixed solution onto a release paper, and apply the applied film Drying to a temperature of 80 to 95 ° C. to produce a coating film; And 코팅) Place the coating film on the outer both sides of the pretreated current collector and heat up and down Thermal bonding at a bonding temperature of 140 to 160 ° C in a laminator adapter equipped with rolls To prepare a negative electrode Method which is an electrode manufactured by a method comprising a. The method of claim 2, The polyvinylidene fluoride homopolymer (PVdF homopolymer) of step iii) has a molecular weight of 100,000 to 1,000,000. The method of claim 2, The mixed solvent of step iii) is selected from the group consisting of a mixed solvent of dimethylformamide and acetone or a mixed solvent of dimethylacetamide and acetone in a volume ratio of 15:85 to 40:60. How to be. The method of claim 2, The plasticizer of step iii) is selected from the group consisting of dibutyl phthalate, dimethyl adipate, ethylene carbonate or propylene carbonate. The method of claim 2, The active material of step iii) is selected from the group consisting of coke, which is graphite or hard carbon. The method of claim 2, The mixed solution of step iii) is 8-18 wt% of polyvinylidene homopolymer (PVdF homopolymer), 10-26 wt% of plasticizer, 3-7 wt% of conductive carbon, 52-79 wt% of active material, mixed solvent Solid content concentration of the mixed solution, including 35 to 65% by weight method. The method of claim 2, The pre-treated current collector of step iii) is a copper expanded mesh (Cu expended mesh), the pretreatment is washed with acetone, and then immersed in an etching solution of strong acid to oxidize the surface, washed with distilled water and dried And a composition comprising 40 to 75% by weight of polyvinylidene fluoride homopolymer (PVdF homopolymer), 10 to 30% by weight of plasticizer, 5 to 30% by weight of conductive carbon and 0.5 to 3% by weight of oxalic acid. A method of spray coating a 0.5-5% by weight mixed solution to a thickness of 10 µm or less, and performing primer coating for hot air drying at a temperature of 100 to 250 ° C. The method of claim 1, The anode of step b) is Iii) for mixing polyvinylidene fluoride homopolymer (PVdF homopolymer) After dissolving in a medium, the plasticizer, the conductive carbon and the active material are mixed in a solution and Preparing a mixed solution; Ii) apply the mixed solution onto a release paper, and apply the applied film Drying to a temperature of 85 to 95 ° C. to produce a coating film; And 코팅) Place the coating film on the outer both sides of the pretreated current collector and heat up and down Laminator splicer with roll is installed at 140 ~ 160 ℃ Step of manufacturing a positive electrode by thermal bonding Method which is an electrode manufactured by a method comprising a. The method of claim 9, The polyvinylidene fluoride homopolymer (PVdF homopolymer) of the step iii) is 100,000 to 1,000,000. The method of claim 9, The mixed solvent of step iii) is selected from the group consisting of a mixed solvent of dimethylformamide and acetone or a mixed solvent of dimethylacetamide and acetone in a volume ratio of 15:85 to 40:60. How to be. The method of claim 9, The plasticizer of step iii) is selected from the group consisting of dibutyl phthalate, dimethyl adipate, ethylene carbonate or propylene carbonate. The method of claim 9, The active material of step iii) is selected from the group consisting of lithium cobalt oxide (LiCoO ₂ ) or lithium manganese oxide (LiMn ₂ O ₄ ). The method of claim 9, The mixed solution of step iii) is 8 to 17 parts by weight of polyvinylidene fluoride homopolymer (PVdF homopolymer), 10 to 25 parts by weight of plasticizer, 5 to 12 parts by weight of conductive carbon, 51 to 78 parts by weight of active material, Solid content concentration of the mixed solution containing a mixed solvent is 35 to 65 weight%. The method of claim 9, The pre-treated current collector of step iii) is a copper expanded mesh (Cu expended mesh), the pretreatment is washed with acetone, immersed in an etching solution of strong acid to oxidize the surface, washed with distilled water and dried And a composition comprising 40 to 75% by weight of polyvinylidene fluoride homopolymer (PVdF homopolymer), 10 to 30% by weight of plasticizer, and 5 to 30% by weight of conductive carbon and having a solid content concentration of 0.5 to 5% by weight. A method of spray coating the solution to a thickness of 10 µm or less, and performing a primer coating for hot air drying at a temperature of 100 to 250 ° C. The method of claim 1, The electrolyte film of step c) Iii) for mixing polyvinylidene fluoride homopolymer (PVdF homopolymer) After dissolving in a medium, the plasticizer and the inert filler are mixed with the solution and stirred. To prepare a mixed solution; And Ii) apply the mixed solution onto a release paper, and apply the applied film Drying to prepare a coating film Method which is a film produced by a method comprising a. The method of claim 16, The polyvinylidene fluoride homopolymer (PVdF homopolymer) of the step iii) is 100,000 to 1,000,000. The method of claim 16, The mixed solvent of step iii) is selected from the group consisting of a mixed solvent of dimethylformamide and acetone or a mixed solvent of dimethylacetamide and acetone in a volume ratio of 15:85 to 40:60. How to be. The method of claim 16, The plasticizer of step iii) is selected from the group consisting of dibutyl phthalate, dimethyl adipate, ethylene carbonate or propylene carbonate, and the mixed amount of the mixed solution is polyvinylidene fluoride. 75 to 120 parts by weight, based on 100 parts by weight of the ride homopolymer (PVdF homopolymer). The method of claim 16, The inert filler of step iii) is selected from the group consisting of fumed silica, alumina and zeolite with or without a hydrophobic group, and the mixed amount of the mixed solution is polyvinylidene fluoride homopolymer ( PVdF homopolymer) 3 to 30 parts by weight based on 100 parts by weight. The method of claim 1, The solvent extraction of step f) is a battery substrate prepared in step e) is put into a diethylether solvent and extracted for 30 minutes and then re-extracted with fresh solvent for 30 minutes and then dried. The method of claim 1, The electrolytic solution of step g) comprises 0.5 to 2 mol of lithium hexafluoride (LiPF ₆ ) salt, a mixed liquid of ethylene carbonate and diethyl carbonate, a mixed liquid of ethylene carbonate and dimethyl carbonate, a mixed liquid of ethylene carbonate and ethyl methyl carbonate or ethylene Method selected from the group consisting of a mixture of carbonate, dimethyl carbonate and ethyl methyl carbonate. In a lithium ion polymer battery, a) based on polyvinylidene fluoride homopolymer (PVdF homopolymer) A negative electrode comprising a negative electrode binder; b) polyvinylidene fluoride homopolymer (PVdF homo) polymer) electrolytes; And c) polyvinylidene fluoride homopolymer (PVdF homo) positive electrode comprising a positive electrode binder based on a polymer) A battery comprising a thermally bonded laminate cell substrate positioned in the structure of a cathode-electrolyte-cathode-electrolyte-anode and an electrolyte solution filled in the battery substrate. The method of claim 23, The negative electrode has a copper current collector inside, 68 to 88 parts by weight of an active material of graphite or hard carbon, 5 to 12 parts by weight of conductive carbon and 8 to 21 weight of polyvinylidene fluoride homopolymer (PVdF homopolymer) Lithium ion polymer battery which is a laminate electrode in which the negative electrode of the polyvinylidene fluoride homopolymer (PVdF homopolymer) base material containing a part is located and thermally bonded. The method of claim 23, The positive electrode is an active material selected from the group consisting of lithium cobalt oxide (LiCoO ₂ ) or lithium manganese oxide (LiMn ₂ O ₄ ) on the outer surface of the aluminum current collector is located inside and 6 to 14 weight of conductive carbon A lithium ion polymer battery, wherein the laminate electrode is a thermally bonded laminate electrode having a positive electrode based on a polyvinylidene fluoride homopolymer (PVdF homopolymer) comprising 7% to 21% by weight of polyvinylidene fluoride homopolymer (PVdF homopolymer). The method of claim 23, The electrolyte solution contains 0.5 to 2 moles of lithium hexafluoride (LiPF ₆ ) salt, a mixed liquid of ethylene carbonate and diethyl carbonate, a mixed liquid of ethylene carbonate and dimethyl carbonate, a mixed liquid of ethylene carbonate and ethyl methyl carbonate, or an ethylene carbonate and dimethyl carbonate And a mixture of ethyl methyl carbonate.