FI122947B - Anode and method of making the anode - Google Patents

Description

ANODE AND METHOD FOR PREPARING ANODE

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The invention relates to an anode for a thin battery and a method of making such an anode.

10 BACKGROUND

The main components of the battery are electrodes equipped with terminals (electrical connectors) for connection to an external circuit, a separator to keep the electrodes separate and prevent short circuits, an electrolyte that carries charged ions from chemical reactions in the electrodes, and a cover to cover the active chemicals. to hold it in place.

"Wet" cells refer to galvanic cells in which the electrolyte is in liquid form and is allowed to flow freely inside the cell housing. "Dry-20" cells are cells that use solid or powdered electrolyte. Cells having a liquid electrolyte can be classified as "dry" if the electrolyte is fixed in place by some mechanism, such as fixing it with jelly or holding it in place with an absorbent material such as paper.

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δ, 25 The most commonly used type of battery at present is the "dry cell" battery used in, for example, relatively large batteries, such as "flashlight" batteries and compact models used for watches or calculators.

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§ Batteries are often classified according to the type of electrolyte used in their manufacture. There are three main categories; acidic, mildly acidic and alkaline. o

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All batteries utilize the same functions to generate electricity; but modifications in materials and manufacturing have produced different types of batteries.

One type of battery consists of a sandwich structure, so-called thin-film batteries. 5 Thin-film batteries, referred to herein as "layered batteries" of any size, can be used directly for membrane applications of any shape or size, and flexible batteries can be made by printing on paper, plastics, or other types of thin film.

10 Thin-film batteries have a wide range of applications, eg as power supplies for consumer products and micro-sized applications. Thin-film batteries are also suitable for powering smart cards and RFID (Radio Frequency Identification).

Methods of making such a thin battery can be, for example, according to Applicant's Finnish Patent Application 20070584, which involves wetting the separator paper with an electrolyte solution and pasting the anode material and cathode material as pastes on the separator paper (s) and on the opposite side of the anode paste. The anode and cathode materials can be applied to separator-20 papers by various methods, such as coating or printing. Coating and printing processes generally involve applying a thin film of functional material to a substrate such as a paper roll, fabric, film, or other textile.

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The term "paste" as used herein refers only to a viscous aqueous dispersion of materials.

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But also the outer separator layers always contain the electrolyte, since they absorb the H electrolyte from the wetted layer, and in addition, the electrolyte solution containing the additives could also be mixed with the anode active material and the cathode

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3 to form so-called anode and cathode pastes.

The electrodes of the thin battery are formed of an anode and cathode. The anode material is a paste or ink containing an anode-active material and usually an electrolyte solution with additives, and the cathode material is a paste or ink containing a cathode-active material and usually an electrolyte solution with additives. The paste is quite viscous so that the electrolyte cannot escape. The ano-inactive material is often zinc (Zn) and the cathode-active material is man-10 (MnO2). The electrolyte solution may contain, for example, ZnO 2 as the main ingredient, as well as additives, such as binder (s). The additive (s) in the electrolyte comprises a binder (s) for imparting other properties to the electrolyte solution, such as, for example, to bind the particles of the electrolyte material to form a paste. The binder is, for example, polyvinylalcohol-15 (PVA).

Conductive material is added to the anode and cathode pastes. The conductive material may be carbon powder such as graphite powder, carbon black, carbon black, carbon nanotubes, conductive ink, or combinations thereof. The electrodes (consisting of anode and cathode pastes including conductive material) are joined to the collector material and the entire product is covered with membranes of the sealing material. The sealing material may be e.g. polypropylene, polyethylene, polyester or other known film materials. The collector material is formed with terminals intended for connection to an external circuit. The collector material may be conductive carbon ink, carbon film or other material which is chemically inert but sufficiently conductive for this purpose.

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The combined layers are cut to the desired size to form the products, and various anode materials have been tested to facilitate the manufacture of the thin battery.

4 US Patent Application 2006/0216586 is disclosed in the prior art. It shows a thin electrochemical cell. The anode of the cell may be a zinc strip. The problem with this solution, however, is that the connection of the zinc strip to the collector is problematic and that the zinc self-discharge is largely due to the lack of coverage.

5 U.S. Patent 6,379,835 relates to a thin film battery. The anode is hydrophilic because it is an aqueous zinc ink or zinc ink in a mixture of an organic solvent and a water swellable polymer and therefore has a high self-discharge rate in the battery. Because of the low conductivity of the anode, 10 additional collectors are required at the anode.

U.S. Patent Application 2006/0115717 discloses a flexible, thin printed battery. The conductive aqueous zinc material for forming the anode is pressed directly onto the non-conductive substrate and made sufficiently conductive to avoid the need for a separate anode current collector. The required conductivity is achieved with an additional zinc + 2 cation (from zinc acetate) and a polymeric binder (polyvinylpyrrolidone) to improve particle contact. Here, too, the hydrophilic zinc anode causes a high level of self-discharge and unstable conductivity of the zinc during the discharge process.

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Other prior art solutions are disclosed e.g. in WO 03/100893 and US 006045942.

^ Intensive efforts are now being made to produce continuously improved batteries by solving some of the identified problems associated with said self-discharge.

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Another problem that can be eliminated in conventional manufacturing processes is that the paper strips become quite wet when impregnated with <S 30 electrolyte and the paste also remains wet after application. This situation affects the surface properties of the layer layers so that the following manufacturing steps are difficult to complete and this makes the overall battery manufacturing process difficult.

Anode and cathode pastes also contain electrolyte. As is well known, zinc ha-5 is quite easily frustrated in a wet environment containing electrolyte salt, and self-discharge is a problem. In addition, printing or coating of the anode paste in particular is also difficult due to rapid changes in the paste properties.

The object of the invention is to solve the problems discussed above.

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SUMMARY OF THE INVENTION

The anode material of the invention for use in a printed battery is essentially characterized in that the anode material is dry and hydrophobic and comprises a substrate, a binder, a conductive material and an anodic material.

The method of the invention for producing anode material for use in a printed battery method comprises the steps of providing a substrate, providing an anode-active material, a conductive material, a solvent, and providing a binder. Said solvent, said binder, said anode-active material and said conductive material are mixed to form an anode ink. Said anode ink is applied and dried on said substrate. In reaction to said drying, said solvent evaporates and said anode ink forms a film o, 25 on said substrate,

The invention is according to the appended main claims and the preferred features are set forth in the dependent claims.

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The present invention may be applicable to alternative anodic active components, such as magnesium, cadmium and copper, combined with a conductive material such as carbon black. Preferably, the anodic material is zinc (Zn). Water or electrolyte is required for any electrolyte reaction and ion transfer between the battery electrodes.

Zinc oxidizes more readily in water or electrolyte environments than in dry environments. For this reason, many of the prior art thin and flexible batteries have a zinc anode made from an aqueous zinc paste or a hydrophilic mate-10. However, such prior art has the disadvantage that self-discharge is rapid. Self-discharge will shorten the battery's life and reduce its capacity.

In the invention, the anode is hydrophobic and dry, which impedes direct penetration of water or electrolyte into the deep layer of the zinc anode. The hydrophobic layer at the dry anode of the invention functions like a wall that maintains the moisture level of the battery stable.

Of course, a suitable level of humidity in a battery is important for good performance, and when an anode of the invention is used in a battery, water can move from the cathode to the surface of the anode after the various layers have been combined. The oxidation reaction takes place at the anode surface between the anode-active metal, the electrolyte and water.

The basic idea of the invention is that it uses dry anode ink instead of ™ 25 instead of using a wet / damp anode paste and a separate anode collector, as in the prior art. In the invention, dry anode ink can (after drying) also cause electrons to be transferred from the anode material to the (-) terminal on the surface of the battery.

o 00 <8 30 In prior art batteries, the anode collector was required to function as a (-) terminal. Or-

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a separate anode collector was used with the wet anode paste because 7 otherwise 1) the wet anode paste would leak out of the battery through the hole in the (-) terminal in the sealing material and because 2) ambient humidity could affect the wet anode paste and impair its performance. Both of these problems are avoided by the anode-5 material of the invention, which eliminates the use of the anode collector.

With the anode collector removed, it is now possible to place the terminals on the same side of the strip as the battery. This allows for a variety of applications that use battery power to connect more easily to the battery. In contrast, harvesting applications are easier to design and manufacture if the dedicated power supply terminals are on the same side of the strip as the application, such as a printed RFID tag or chip.

The anode of the invention is flexible, stable, and mass-produced, and is usable in batteries that are used as a power supply for a number of applications requiring a thin flexible power supply.

Commercially available conductive carbon inks and commercially available zinc powders can be used to make the anode without the need for an additional collector in the battery. The anode electrode consists of an anode material which is a homogeneous mixture of zinc powder and conductive carbon ink.

The anode material for the battery of the invention is prepared by adding zinc powders to the conductive carbon ink and mixing until a homogeneous mixture is obtained.

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The zinc powder used for this purpose may be a commercial battery quality product.

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you with certain particle size and purity characteristics. Less than 50 µm particle size and more than 99% purity have been found to be suitable. Examples of commercially available zinc powders for S 30 include Grillo-Werke Aktiengesell Schaft GZN 3-0 and Xstrata EC-100.

8 The used conductive carbon ink can be a commercial product with certain characteristics. The ink used should have high conductivity, high flexibility, high binding capacity and high hydrophobicity. Examples of commercial conductive carbon inks used are, for example, XZ302-1 HV and XZ302-1 MV Conducti-5 ve Carbon, 26-8203 Conductive Graphite, Creative Material 116-19 Low Temperature Curing Conductive Ink (Low Temperature) hardening conductive ink), DuPont 7105 Carbon (carbon), Asahi FTU-20D3, and Acheon EB-412.

10 The conductive ink and the proportion of zinc and conductive ink selected depend on the properties of the materials, such as the square resistance of the conductive carbon ink, the elasticity of the conductive carbon ink, the binding capacity, the viscosity and the hydrophobic properties of the conductive carbon ink.

From the manufacturing point of view, the anode used in the battery according to the invention has the following advantages for several target applications 1) It is easier to manufacture the anode separately from the manufacture of the battery, since it can be made beforehand and eg stored in rolls after printing on the separator. Because it is not necessary to perform each battery manufacturing step at the same time, the battery manufacturing process is less vulnerable, e.g., when problems occur at a particular process step. This also means that the poor quality of the product at some point does not render the entire production defective, but only the production stage in question.

2) The anode material of the invention is easily printed on the separator during the manufacture of the battery; ^ 3) The anode used in the invention reduces self-discharge because it is made from a hydrophobic ink and does not absorb the electrolyte.

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5) Another consequence of not requiring a separate collector for the anode in the first embodiment of the invention is that the anode comprising the anode of the invention

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g 30 battery becomes thinner o 6) Good stability due to the hydrophobic nature of the ink; 9

In the following, the invention will be described more fully with the aid of some illustrative figures and examples. However, the invention is not limited to the details of the following description.

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DETAILED DESCRIPTION

Commercially available conductive carbon inks and commercially available zinc powders can be used to prepare the anode material, as discussed in more detail above. The anode material is a homogeneous mixture of zinc powder and conductive carbon black.

The anode material is imprinted on a separator prepared in advance as described, e.g., in EXAMPLE 1, using one of the known printing methods on a paper web supported by a press roll.

The web on which the anode material is pressed passes through a nip consisting of a press roll and another press roll on which the anode material is printed. The web is then dried.

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Various known methods can be used in the process, for example, silk-screen printing, gravure printing, offset printing and flexo printing. Drying can also be accomplished by hot curing, infra red curing and ultraviolet curing and by hot air. The anode material could be cut and then the cutting method can be, for example, die cutting, laser cutting, punching, splitting, stamping or other known method.

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° PREPARATION EXAMPLE - 00

S 30 MANUFACTURE OF THE ANODIC MATERIAL OF THE INVENTION

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The anode material (i.e., anode ink) of the invention is prepared by adding zinc powder to the conductive carbon ink and mixing until homogeneous, as mentioned above. The ink and zinc powder used in the test are Ac-heson EB412 and EC-100.

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The conductive carbon ink is stirred at a speed of, for example, 300 rpm, and the zinc powder is gradually added. Once the zinc powder is added, the mixer speed is gradually increased to 2000 rpm and the mixture is stirred for an additional 30 minutes.

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The mixing performed in accordance with the invention gives a good result on the anode performance since it avoids peeling problems, conductivity problems and uneven conductivity. The correct viscosity of the anode material is required. If the viscosity is too low, the zinc particles will accumulate at the bottom. A suitable ink viscosity is: Brookfield 20 ° C 20 RPM 20,000-28,000 mPa.S. The quality of the mix can be controlled by taking samples and checking their density, or it can be measured by an electron microscope.

Because the anode material (i.e., anode ink) is made in this way, it can be pre-printed and dried and e.g. stored in rolls after printing on the separator.

This is very advantageous for later battery manufacture. Because each battery manufacturing step does not need to be performed simultaneously, the battery preparation process is less vulnerable, e.g., when problems occur at a particular process step.

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° TEST METHODS

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Some characteristics of the anode material (or anode ink) may indicate the quality of the battery being manufactured:

The value of the internal resistor is used to measure power dissipation in power supplies. This value should be as low as possible.

5 - The value of the square resistor measures the conductivity of the film format material. This value should also be as low as possible.

The percentage elasticity is described as the percentage that is measured as the change in resistance after bending. The lower the percentage of elasticity, the better the elasticity of the conductive ink. Bending fracture means an extremely high degree of elasticity of sound 10.

The bonding capacity indicates the non-peeling property of the material and should be as high as possible.

The viscosity value is an estimate of how difficult the liquid phase mixing is. It should be high enough to prevent the zinc particles from piling up, and low enough to print the anode.

Hydrophobicity indicates the ability to keep the anode dry in accordance with the basic idea of the invention

Here are some principles to measure these characteristics:

Evaluation of hydrophobicity:

Hydrophobicity was assessed by applying water to the anode, and hydrophobicity was considered good if the water did not dissolve and the anode cracked and / or squared resistance changed.

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δ, 25 Internal resistance measurement method: ° If V0 is the open loop voltage of the battery; VL is the load voltage measured 1 min after the discharge has started; RL is the load resistance value, ^ is the internal resistance

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Method of measuring square resistance: 12

The square resistor is measured after the conductive ink or anode ink is printed on the substrate and dried. The value of the square resistor is the average resistance value at six different locations on the strip. Each resistor is measured using two multimeter probes over a distance of 1 cm.

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TEST EXAMPLE 1 - CHARACTERISTICS OF THE ANODE

Anode inks, prepared from different portions of zinc powder and conductive carbon ink 10, were prepared by Method 1.

The zinc powders used in the tests were A: Grillo-Werke Aktiengesellschaft GZN 3-0 (zinc content 99.8%, particle size 15> 25 pm 14%, <25 pm 86%) and B: Xstrata EC-100 (zinc content 99.9%, particle size) > 75 µm 0.1%, <45 µm 96%) 20 The conductive carbon ink used was A: XZ302-1 HV, B: XZ302-1 MV, C: 26-8203 Conductive Graphite, D: Creative Material 116 -19 Low Temperature Curing Conductive Ink, E: DuPont7105 Carbon (Carbon), F: 2 Asahi FTU-20D3, and G: Acheson EB-412.

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The following Table 1 shows some of the properties of these conductive carbon inks.

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g Square-Pack - Viscose - Flexibility Hydrophobicity Weight Stiffness § ___ iPa] ___ ™ Ink A about 40 Ω 20 pm 55-65 * After Folding Dry Ink Film ____ resistance increases approximately insoluble but up to 13 _____65 Ω Resistance increased

Ink B about 40 Ω 20 μ m 30-40 * After Folding Dry Ink Film Resistance Increases Approximately Insoluble But Up to _____65 Ω Resistance Increased

Ink about 35 Ω 20 pm 7-8 * After Folding Dry Ink Film C part of sample did not break but soluble, and internal resistance increased increased approximately 70 Ω _____

Ink approximately 80 Ω 20 pm Not allowed- After folding no Water does not change D resistance change in dry ink resistance _______

Ink E about 20 Ω 20 pm 15-80 * After Folding No change with Dry Ink Resistance _______

Ink F about 20 Ω 20 pm 35-45 * After Folding, No Dry Ink Dissolved in _____the_water

Ink about 15 Ω 20 pm 12-28 After Folding No Water No G change change in dry ink resistance _____

The proportions of conductive carbon black and zinc powder in the tested anodes were 1: 1.

The hydrophobicity of the anode ink was tested from the two above points after adding water to the anode.

The following Table 2 shows the test results for the flexibility, hydrophobicity and square resistance of the anode inks. Table 2 shows that for all the tested i § 10 anode inks, the object of the invention is fulfilled in terms of hydrophobicity up to 80 Ω square resistances.

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The results of Table 2 show that the advantageous properties of the anode ink depend mainly on the conductive ink used. Inks E and G have better properties and the associated zinc anode does not depend on the zinc powder used.

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An anode that uses ink G is best with 250 four resistors. Ink G was used in the following test.

TABLE 2 - TEST RESULTS

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Zinc Square resilience Flexibility Hydrophobicity

Ink A A about 65 Ω Broken after fold Dry ink film is not ___ soluble, but resistor B about 65 Ω Broke after fold Dry ink film is not ____ soluble, but resistance

Ink B A about 65 Ω Broken after fold Dry ink film is not ___ soluble, but resistor B about 65 Ω Broke after fold Dry ink film is not ____ soluble, but resistance

Ink C A about 40 Ω Broken after fold Dry ink film not ___ soluble, but resistor B about 40 Ω Broke after fold Dry ink film is not ____ soluble, but resistance

Ink D A Approx. 150 it After Folding Do Not Change With Water With Dry Ink_ B Approx. 150 Ω After Folding Do Not Change With Dry With Water With ___

Ink E A about 25 Ω After folding with water, there was no change in dry ink ___resistance_ B about 25 Ω After folding with water, there was no change in dry ink _____

Ink FA about 25 Ω After Folding Over - Water Damages Dry Worked Up To 30 Membranes, Ink___Membrane Burst_ ^ B About 25 Ω After Folding - Water Damaged Dry Up To 30 Membranes, Ink Film Breaked ----- 9 Ink GA about 25 Ω After folding, the water hardly affects the ink film up to about 30 X ---- £ B about 25 Ω After the folding, the water hardly affects the ink film up to 30 s 00 _____ tn oo oo

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Claims (18)

1. A flexible anode material for use in a printed thin battery used as a power source for applications requiring a thin 5 flexible power source, characterized in that the anode material is dry and hydrophobic and comprises: a paper insulating substrate, a binder, a conductive material, and and wherein the conductive material, the anodic material and the binder are selected to form a dry hydrophobic film on the substrate after drying said materials and binder with a solvent. Anode material according to claim 1, characterized in that the conductive material is integrated with the anode active material. Anode material according to claim 1, characterized in that the anode active material contains a metal powder. 20 Anode material according to Claim 3, characterized in that said metal powder contains metal selected from the following list: zinc, nickel, magnesium, copper, iron and aluminum. The anode material according to claim 1, characterized in that the conductive material is selected from the following list: carbon, carbon black, carbon nanotube, carbon film, graphite film and silver. ί CL ° 6. Anode material according to claim 1, characterized in that the 00 g binder is a thermoplastic resin or epoxy resin and the solvent is an organic solvent containing organic acetate or alcohol. Anode material according to Claim 1, characterized in that the dry anode film having a thickness of 20 microns has a square resistance less than 80 Ω. Anode material according to claim 7, characterized in that 5 dry anode films having a thickness of 20 microns have a square resistance less than 25 Ω. Anode material according to claim 8, characterized in that the dry anode film having a thickness of 20 microns has a square resistance less than 15 Ω. 10. A method of making a flexible anode material for use in a printed thin battery used as a power source for applications requiring a thin flexible power source, characterized in that the method comprises: providing a paper tray, providing an anode active material, providing a solvent, providing a binder said solvent, said binder, said anode-active mate-20, and said conductive material for forming an anod ink, applying said anode ink to said paper tray, drying said anode ink on said paper tray, reacting said drying, evaporating said solvent, and drying said anode ink. . The method of claim 10, wherein the process comprises pre-mixing the conductive material, solvent and binder to form a conductive ink. o si- 00 LO 00 o o CM A method for producing an anode for use in a printed thin battery as claimed in claim 10, characterized in that the anode-active material contains metal powder. A method for producing an anode for use in a printed thin battery 5 according to claim 10, characterized in that, when applying said anode ink on said substrate, the amount of anodic material in the applied ink is 4-20 mg / cm 2. The method of producing an anode for use in a printed battery as claimed in claim 18, characterized in that, when applying said anode ink on said substrate, the amount of anodic material in the applied ink is from 8 to 12 mg / cm 2. The method of producing an anode for use in a printed battery as claimed in claim 14, characterized in that when applying said anode ink to said substrate, the amount of anodic material in the applied ink is about 10 mg / cm 2 of said substrate. A method for manufacturing an anode used in a printed battery according to claim 10, characterized in that said anode active material is zinc. A method for producing an anode for use in a printed battery as claimed in claim 10, characterized in that said drying is carried out at a temperature of 110 to 140 ° C for 2 to 20 minutes. o i r- · The method of producing an anode for use in a printed battery as claimed in claim 10, characterized in that said drying is carried out at about 130 ° C for about 10 minutes. 00 J S 30 o o {M