KR20100044087A - Electrode composition for inkjet print, electrode and secondary battery prepared using the same - Google Patents

Abstract

PURPOSE: An electrode ink composition for ink-jet printing is provided to manufacture electrode with minute patterns by an ink jet printing method. CONSTITUTION: An electrode ink composition for ink-jet printing comprises: an electrode active material, and a solvent, wherein the solvent further comprises a first solvent having a boiling point in a range of about 150 to about 170deg.C at 1 atm, and a surface tension of 30 dyne/cm or more at 25deg.C. The first solvent is a solvent comprising an amide group. The electrode composition for the inkjet print comprises the electrode active material and solvent.

Description

Electrode composition for inkjet print, electrode and secondary battery prepared using the same {Electrode composition for inkjet print, electrode and secondary battery prepared using the same}

Disclosed are an electrode composition for inkjet printing, an electrode prepared using the same, and a lithium battery. More specifically, an electrode composition for inkjet printing capable of forming a precise electrode pattern, an electrode manufactured using the same, and a lithium battery are disclosed.

Power sources for portable electronic devices such as mobile phones, personal digital assistants (PDAs) and portable multimedia players (PMPs); Motor driving power supplies such as high-power hybrid vehicles and electric vehicles; The use of secondary batteries as a power source for flexible displays such as electronic ink (e-ink), electronic paper (e-paper), flexible liquid crystal display (LCD), and flexible organic diode (OLED) is rapidly increasing. Applicability is also increasing as a power supply for integrated circuit elements on a substrate.

However, when used as a power source for portable electronic devices, packaging for safety imposes restrictions on various product designs, and when used as a motor driving power source, the need for high output, small size, and light weight is increasing, and flexible display is required. When used as a power supply for the power supply, it must be manufactured to be thin, light and bendable, and to be used as a power supply for an integrated circuit device, it must be precisely patterned to a certain form.

As an electrode manufacturing method for meeting various demands of such a secondary battery, an inkjet printing method is drawing attention instead of a conventional slurry coating method. Such an inkjet printing method can produce a thin, uniform and flat electrode for a secondary battery, and has a feature of economically manufacturing a pattern of a desired shape.

Meanwhile, the composition for forming a secondary battery electrode mainly consists of an electrode active material of a lithium transition metal oxide, a solvent used as a medium, and a binder for binding between the electrode and particles after drying the solvent. The solvent may be used in the form of one or more mixtures in consideration of the dispersibility of the particles, the discharge characteristics of the ink composition, the drying characteristics and the like. Typically, N-methyl-2-pyrrolidone (NMP) is included as a main solvent, which has high solubility in polyvinylidene fluoride (PVdF) binder, which is mainly used as a binder, but has a high boiling point and low volatility, so that drying speed is high. It's low.

It is to provide an electrode composition capable of producing an electrode having a precise pattern by an inkjet printing method.

It is to provide an electrode and a secondary battery produced using the electrode composition.

According to an aspect of the present invention, the electrode composition is an electrode composition for inkjet printing comprising an electrode active material and a solvent, the solvent has a boiling point of 150 to 170 ℃ and a surface tension of 30 to 40 dyne / cm at 25 ℃ under 1 atmosphere sign There is provided an electrode composition comprising a first solvent.

The content of the electrode active material may be 1 to 20% by weight based on the electrode composition.

The first solvent may be an amide group-containing solvent.

The amide group-containing solvent may be dimethylacetamide, dimethylformamide or a mixture thereof.

The content of the first solvent may be 80 to 100% by weight based on the total weight of the solvent.

The electrode composition may further include one or more selected from the group consisting of a binder, a conductive agent, a humectant, a dispersant, and a buffer.

The viscosity of the electrode composition may be 100 mPa · sec or less at a temperature of 25 ° C. and a shear rate of 1000 s ⁻¹ .

According to another aspect of the present invention, there is provided a secondary battery electrode produced by printing the above electrode composition in an inkjet method.

According to another aspect of the present invention, a secondary battery including the electrode is provided.

Electrode composition according to an embodiment of the present invention can be printed in an inkjet method to produce an electrode having a precise pattern.

Hereinafter, an electrode composition for inkjet printing according to an embodiment of the present invention will be described in more detail.

An electrode composition for inkjet printing according to an embodiment of the present invention includes an electrode active material and a solvent, and the solvent has a boiling point of 150 to 170 ° C. under 1 atmosphere and a first solvent having a surface tension of 30 dyne / cm or more at 25 ° C. It includes. The content of the electrode active material may be 1 to 20% by weight based on the electrode composition.

Usually NMP used for the composition for electrode formation of a secondary battery has a high boiling point, and its drying rate is low. Therefore, when NMP is used as the main solvent, the electrode is formed by inkjet printing. Since the undried droplets move due to the high surface tension, they move out of the impact point or aggregate together with other droplets. It can be difficult to form. Since the first solvent used in the embodiment of the present invention has a relatively high boiling point and thus does not occur the above-mentioned phenomenon due to undried droplets, an electrode composition having a precise surface tension and having a precise pattern may be prepared.

The first solvent used in the electrode composition according to the embodiment of the present invention has a surface tension of 30 to 40 dyne / cm. In general, a solvent having a surface tension of 30 dyne / cm or more is preferable in terms of increasing the contact angle between the nozzle surface of the ink and the nozzle plate during printing and the contact angle between the ink and the current collector after printing, but considering the effect on the boiling point It is preferable that the surface tension is 40 dyne / cm or less.

The first solvent may be an amide group-containing solvent. While not wishing to be bound by theory, such an amide group-containing solvent contributes a non-covalent electron pair of carbonyl oxygen to the metal portion of the electrode active material contained in the electrode composition, thereby lowering the surface energy of the oxide of the electrode active material to disperse the particles well. have. Preferably the first solvent is selected from dimethylacetamide (DMAC), dimethylformamide (DMF) or mixtures thereof.

In the electrode composition for inkjet printing according to an embodiment of the present invention, the first solvent may be used in combination with a second solvent according to the use and purpose. Examples of the specific second solvent include, but are not limited to, saturated hydrocarbons such as hexane; Aromatic hydrocarbons such as toluene and xylene; Alcohols such as methanol (MeOH), ethanol (EtOH), propanol (PrOH) and butanol (BuOH); Ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and diisobutyl ketone; Esters such as ethyl acetate and butyl acetate; Ethers such as tetrahydrofuran (THF), dioxane and diethyl ether; Dimethylsulfoxide (DMSO) or a mixture of two or more thereof. When mixed with the second solvent, the content of the first solvent may be 80 to 100% by weight based on the total weight of the solvents.

In the electrode composition for inkjet printing according to the embodiment of the present invention, the electrode active material is not particularly limited as long as the object of the present invention is not impaired, and any of ordinary oxide particles used as an electrode active material of a secondary battery may be used. Can be used Specific examples of the positive electrode active material that can be used include Li-Co-based composite oxides such as LiCoO ₂ , Li-Ni-based composite oxides such as LiNiO ₂ , Li-Mn-based composite oxides such as LiMn ₂ O ₄ , LiMnO ₂ , and Li ₂ Cr ₂ Li-Cr-based composite oxides such as O ₇ and Li ₂ CrO ₄ , Li-Fe-based composite oxides such as LiFeO ₂ , Li-V-based composite oxides, and the like. Specific examples of the negative electrode active material that can be used include Li-Ti-based composite oxides such as Li ₄ Ti ₅ O ₁₂ , transition metal oxides such as SnO ₂ , In ₂ O ₃ , and Sb ₂ O ₃ , graphite, hard carbon, acetylene black, and carbon. Carbon, such as black, etc. are included.

The content of the electrode active material may be 1 to 20% by weight of the total electrode composition, and more specifically 3 to 7% by weight. In this range, the electrode composition is not high in viscosity, while maintaining the stability and ejection property of the composition, while increasing the printing efficiency.

The electrode active material may have a D ₅₀ of 50-500 nm.

The electrode composition according to the embodiment of the present invention may have a viscosity of 100 mPa · sec or less at a temperature of 25 ° C. and a shear rate of 1000 s ⁻¹ . Preferably the viscosity at a temperature of 25 ° C. and a shear rate of 1000 s ⁻¹ may be 0.5 to 5 mPa · sec.

According to another embodiment of the present invention, a binder, a conductive agent, a moisturizer, a dispersant, and / or a buffer may be additionally included in the electrode composition.

After inkjet printing, a binder may be used to give adhesion between the electrode active material and the electrode plate. Non-limiting examples of specific binders include polyvinyl alcohol, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene- Hexafluoropropylene copolymer, carboxymethylcellulose, or a mixture of one or two of them, and polyvinylidene fluoride (PVdF) is particularly preferred.

The content of the binder is 0.01 to 10% by weight based on the weight of the electrode composition, more specifically 0.05 to 5% by weight, but is not necessarily limited to this range.

A conductive agent may be used to improve conductivity of the electrode active material particles. The conductive agent to be used is not particularly limited as long as it is within the range of achieving the object of the present invention. Non-limiting examples of specific conductive agents include acetylene black, carbon black, graphite, carbon fibers, carbon nanotubes and the like. The content of the conductive agent may be, for example, 1 to 20% by weight based on the electrode active material particles, but is not limited thereto.

A humectant may be used to serve to prevent drying of the electrode composition at the nozzle to prevent nozzle clogging. For example, glycols, glycerol, pyrrolidone and the like can be used. The amount used may be used in an amount of 5 to 40% by weight based on the total weight of the composition. However, the drying inhibitory effect of the electrode composition may be sufficiently obtained according to the content of the first solvent, and thus may not be used.

A dispersant may be used to disperse the electrode active material and the conductive agent. The dispersant used is not particularly limited as long as the object of the present invention is not impaired. Specifically, fatty acid salt, alkyl dicarboxylate, alkyl sulfate ester salt, polysulfate ester alcohol salt, alkyl naphthalene sulfate, alkylbenzene sulfate, alkyl naphthalene sulfate ester salt, alkyl sulfone succinate salt, naphthenate salt, alkyl ether carboxylate salt , Acylate peptide, alpha olefin sulfate, N-acyl methyl taurine salt, alkyl ether sulfate, secondary polyalcohol ethoxy sulfate, polyoxyethylene alkyl permil ether sulfate, monogly sulfate, alkyl ether phosphate ester salt, alkyl phosphate ester Salts, alkylamine salts, alkylpyridium salts, alkylimidazolium salts, fluorine- or silicone-acrylic acid polymers, polyoxyethylene alkyl ethers, polyoxyethylene sterol ethers, lanolin derivatives of polyoxyethylene, polyoxyethylene / polyoxy Propylene copolymer, polyoxyethylene sorbitan fatty acid ester, monoglyceride fatty acid ester, water LOS fatty acid ester, alkanolamide fatty acid, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, polyvinyl alcohol, polyvinylpyridone, polyacrylamide, carboxyl group-containing water-soluble polyester, hydroxyl group-containing cellulose resin, acrylic resin Any one or two or more of conventional dispersants such as butadiene resin, acrylic acid, styrene acrylic, polyester, polyamide, polyurethane, alkylbetamin, alkylamine oxide, phosphatidylcholine can be used. Do.

The content of the dispersant may be 1 to 20% by weight based on the weight of the electrode active material, but may not be added in consideration of the properties or dispersibility of the electrode.

In addition, the electrode composition for inkjet printing may further include a buffer to maintain stability and adjust the appropriate pH. As such a buffer, amines, such as trimethylamine, triethanolamine, diethanolamine, and ethanolamine, or any one of sodium hydroxide and ammonium hydroxide can be selected and used. Such a buffer may be used in an amount of 0.1 to 5% by weight based on the content of the electrode active material, but may not be used depending on the electrode composition.

The electrode composition for inkjet printing including each component as described above is configured in ink form and used for inkjet printing. To this end, a ball mill and a bead mill are sequentially performed by mixing an appropriate amount of each component such as the oxide active material, a solvent, a binder, a humectant, a conductive agent, a dispersant, a buffer, and the like, and sequentially performing a 1 μm and 0.45 μm PTFE syringe filter. Pass through to complete the electrode composition.

The electrode composition for inkjet printing thus obtained preferably uses an inkjet printer to form an electrode by printing on a current collector in the form of a predetermined pattern.

The inkjet method is a method in which electrode ink is printed onto a current collector as droplets from a nozzle of an inkjet print. Although the inkjet method includes a thermal drive method, a piezoelectric element method, and the like, it is preferable to use a piezoelectric element method from the viewpoint of thermal stability of the battery material. The positive electrode is manufactured when the positive electrode composition including the positive electrode active material is printed by the inkjet method, and the negative electrode is manufactured when the negative electrode composition including the negative electrode active material is printed by the inkjet method.

The method of printing the electrode composition by an inkjet method is not particularly limited. For example, an inkjet printer using an inkjet head can be connected to a commercially available computer, and predetermined patterns can be created on the current collector by legitimate software. The means for drying the electrode composition printed on the current collector may be, for example, 1 minute to 8 hours in a vacuum atmosphere of 20 to 200 ℃, but is not necessarily limited to this range. The current collector may be a known material. For example, it is an aluminum thin film, a stainless thin film, a copper thin film, a nickel thin film, etc.

As described above, the electrode composition containing the first solvent has a high contact angle between the nozzle surface and the nozzle plate and a current collector after printing, and a high drying speed. This may be provided. In addition, by using an electrode having such a high resolution and high precision pattern, a thin micro secondary battery usable as a power source for an integrated circuit device can be manufactured, and a secondary battery having a three-dimensional electrode pattern can be manufactured.

In the secondary battery according to the exemplary embodiment of the present invention, an electrode manufactured by printing the electrode composition described above by an inkjet method is adopted. Although the form of a battery is not specifically limited, A laminated type is preferable, A lithium primary battery, a lithium secondary battery, as well as a fuel cell are also possible.

The method for manufacturing a secondary battery according to an embodiment of the present invention is not particularly limited except for employing an electrode in which an electrode composition is printed and manufactured by an inkjet method. For example, a positive electrode composition according to an embodiment of the present invention is printed on a predetermined current collector by an inkjet method, and dried to form a positive electrode. The negative electrode composition according to the embodiment of the present invention is printed and dried in an inkjet manner on a surface opposite to the surface where the positive electrode of the current collector is formed to form a negative electrode. Therefore, a bipolar electrode is produced.

An electrolyte layer having a predetermined thickness is formed on the layer of the anode and / or the cathode of the bipolar electrode and dried. In an inert atmosphere, a bipolar electrode having the electrolyte layer formed thereon is stacked to manufacture a battery laminate. An insulating sealing layer is formed on the battery stack and packed to complete a secondary battery.

Hereinafter, the present invention will be described in more detail with reference to preferred examples, but the present invention is not limited thereto.

<Example>

Example 1

After adding 5 parts by weight of diethylene glycol (DEG) to a mixed solvent of 70 parts by weight of dimethylacetamide (DMA _C ) and 20 parts by weight of ethanol (EtOH), 4.65 parts by weight of LiCoO ₂ and 0.15 parts by weight of acetylene black (AB) After adding 0.2 parts by weight of polyvinylidene fluoride (PVdF) and dispersing with a paint shaker using zirconia beads having a 0.3 mm particle diameter for 2 hours, a 1 μm and 0.45 μm polytetrafluoroethylene (PTFE) syringe filter was used. Passed sequentially to complete the electrode composition.

The electrode composition was printed on an aluminum foil using a inkjet printer (Fuji Dimatix DMP-2800). The inkjet ejection results are shown in FIG. 1, and the pattern precision of the ejection results is visually observed and shown in Table 3. In addition, the contact angle with the aluminum foil of the electrode composition was measured using a contact angle meter (DSA-100), and the results are shown in Table 3 together.

Example 2

90 parts by weight of dimethyl acetamide (DMA _C ), 5 parts by weight of diethylene glycol (DEG), 4.65 parts by weight of LiCoO ₂ , 0.15 parts by weight of acetylene black (AB), and 0.2 parts by weight of polyvinylidene fluoride (PVdF) were mixed. After dispersion for 2 hours with a paint shaker using 0.3 mm particle size zirconia beads, the electrode composition was completed by sequentially passing 1 μm and 0.45 μm polytetrafluoroethylene (PTFE) syringe filters.

The electrode composition was printed on an aluminum foil using a inkjet printer (Fuji Dimatix DMP-2800). The physical properties such as the pattern accuracy of the discharge result evaluated visually and the contact angle with the aluminum foil of the electrode composition were evaluated, and the results are shown in Table 3.

Example 3

95 parts by weight of dimethyl acetamide (DMA _C ), 4.65 parts by weight of LiCoO ₂ , 0.15 parts by weight of acetylene black (AB), and 0.2 parts by weight of polyvinylidene fluoride (PVdF) were mixed. After dispersion for a period of time, the electrode composition was completed by sequentially passing 1 μm and 0.45 μm polytetrafluoroethylene (PTFE) syringe filters.

The electrode composition was printed on an aluminum foil using a inkjet printer (Fuji Dimatix DMP-2800). The physical properties such as the pattern accuracy of the discharge result evaluated visually and the contact angle with the aluminum foil of the electrode composition were evaluated, and the results are shown in Table 3.

Examples 4-6

Except that dimethylformamide (DMF) was added in place of dimethylacetamide in the composition shown in Table 1, the electrode compositions were prepared in the same manner as in Examples 1 to 3, and the results of preparing and evaluating the electrodes using the same are shown in Table 1 below. 3 is shown.

Comparative Examples 1 to 3

Except that N-methylpyrrolidone (NMP) in place of dimethylacetamide in the composition shown in Table 1, the electrode composition was completed in the same manner as in Examples 1 to 3, and the electrode was prepared and evaluated using the same. The results are shown in Table 3. The inkjet discharge result of the comparative example 1 is shown in FIG.

The viscosity of the electrode compositions prepared in Examples and Comparative Examples are shown in Table 1, and the boiling points and surface tensions of the solvents used in Examples and Comparative Examples are shown in Table 2. Viscosity measurements were measured at 25 ° C. and a shear rate of 1000 s ⁻¹ using AR-2000 (TA Instrument).

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 DMAC 70 90 95 - - - - - - DMF - - 70 90 95 - - - NMP - - - - - 70 90 95 EtOH 20 - - 20 - - 20 - -  Moisturizer (DEG) 5 5 - 5 5 - 5 5 - Active Material (LiCoO ₂ ) 4.65 4.65 4.65 4.65 4.65 4.65 4.65 4.65 4.65 Challenger (AB) 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Binder (PVdF) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Viscosity (mPasec) 3.96 4.12 4.21 3.89 4.09 4.08 4.25 4.65 4.66

NMP DMF DMA _C Boiling Point (1 atm) 202 ℃ 153 ~ 155 ℃ 164 ~ 166 ℃ Surface tension 40.79 dyne / cm 36.76 dyne / cm ＠ 20 ℃ 36.42 dyne / cm ＠ 25 ℃ 36.7 dyne / cm ＠ 20 ℃ 32.43 dyne / cm ＠ 20 ℃

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Contact angle 20.8 20.2 21.3 18.5 19.1 19.0 12.2 11.9 12.5 Pattern precision ○, (see Figure 1) ○ ○ △ △ △ × × ×

○: excellent, △: good, ×: poor

Referring to Table 3 and Figures 1 and 2, it can be seen that the electrode composition according to the embodiment of the present invention can provide an electrode having a large contact angle and excellent pattern precision by using the inkjet method.

1 is a photograph showing an inkjet ejection result obtained using the electrode composition according to Example 1. FIG.

FIG. 2 is a photograph showing an inkjet ejection result obtained using an electrode composition according to Comparative Example 1. FIG.

Claims (10)

In the electrode composition for inkjet printing comprising an electrode active material and a solvent, The solvent composition comprises a first solvent having a boiling point of 150 to 170 ℃ and a surface tension of at least 30 dyne / cm at 25 ℃ under 1 atm. The electrode composition of claim 1, wherein the electrode active material content is 1 to 20 wt% based on the electrode composition. The electrode composition of claim 1, wherein the first solvent is an amide group-containing solvent. The electrode composition of claim 3, wherein the amide group-containing solvent is dimethylacetamide, dimethylformamide, or a mixture thereof. The electrode composition of claim 1, wherein the content of the first solvent is 80 to 100 wt% based on the total weight of the solvent. The electrode composition of claim 1, further comprising at least one component selected from the group consisting of a binder, a conductive agent, a humectant, a dispersant, and a buffer. The electrode composition of claim 1, wherein the electrode composition has a viscosity of 100 mPa · sec or less at a temperature of 25 ° C. and a shear rate of 1000 s ⁻¹ . The electrode composition of claim 1, wherein the electrode composition has a viscosity of 0.5 to 5 mPa sec at a temperature of 25 ° C. and a shear rate of 1000 s ⁻¹ . The electrode for secondary batteries manufactured by printing the electrode composition of any one of Claims 1-8 by the inkjet method. A secondary battery comprising the electrode according to claim 9.

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