Anode and a method of manufacturing an anode

Abstract

The printed battery has cathode and anode electrodes with terminals to connect to an external circuit, separator therebetween and electrolyte. An anode electrode material is applied on one side of the separator and a cathode electrode material on the opposite side. The anode material is dry and hydrophobic and is prepared by providing an anode active material, conductive material, solvent and a binder that are mixed to form an anode ink. The anode ink is applied on a substrate and then dried. In response to the drying, the solvent evaporates and the anode ink forms a film on the substrate. The prepared anode material is applied on the separator. An electrolyte solution is printed on the separator that has the anode material thereon. A cathode material is applied between a collector material and separator.

Description

TECHNICAL FIELD[0001]The invention is concerned with an anode for a thin battery and a method for preparing such an anode.BACKGROUND[0002]The basic components of a battery are the electrodes with terminals (electric connections) to connect to an external circuit, a separator to keep the electrodes apart and prevent them from shorting, the electrolyte which carries the charged ions resulting from the chemical reactions taking place at the electrodes and a cover to contain the active chemicals and hold the electrodes in place.[0003]“Wet” cells refer to galvanic cells where the electrolyte is in liquid form and is allowed to flow freely within the cell casing. “Dry” cells are cells that use a solid or powdery electrolyte. Cells with liquid electrolyte can be classified as “dry” if the electrolyte is immobilized by some mechanism, such as by gelling it or by holding it in place with an absorbent substance such as paper.[0004]The most common type of battery used today is the “dry cell” b...

AI Technical Summary

Benefits of technology

[0029]Zinc is more easily oxidized in water or in an electrolyte environment than in a dry environment. In many thin and flexible batteries of prior art, the zinc anode is therefore made of an aqueous paste of zinc or of a hydrophilic material. The disadvantage of such a prior art battery is, however, that the self discharge is fast. As a consequence of the self-discharge, the lifetime of the battery becomes short and its capacity smaller.

[0034]When the anode collector is eliminated it is now possible to place the terminals on the same side of the sheet like battery. This will enable wide range of applications using the power of the battery to be connected more easily to the battery. Namely it is easier to design and produce the applications if the power inlet terminals for them are on a same side of a sheet like application e.g. a printed RFID tag or a chip.

[0035]The anode of the invention is flexible, stable and mass producible and useful in batteries used as a power source for many applications, where a thin flexible disposal power source is needed.

[0039]The conductive carbon ink used can be a commercial product with certain properties. The ink to be used should possess high conductivity, high flexibility, high binding strength and high hydrophobicity. Examples of usable commercial conductive carbon ink are e.g. XZ302-1 HV and XZ302-1 MV Conductive Carbon, 26-8203 Conductive Graphite, Creative Material 116-19 Low Temperature Curing Conductive Ink, DuPont 7105 Carbon, Asahi FTU-20D3, and Acheson EB-412.

[0041]From the production point of view, the anode of the invention to be used in a battery has the following advantages for many applications of interest1) It is easier to produce the anode separately form the battery manufacture, since it can be done in advance and e.g. be stored on rolls after printing on separator. As each step for making the battery does not have to be made simultaneously, the manufacturing process for making the battery is less vulnerable when e.g problems occur in a certain process step. This also means that a bad quality in a product of some step does not render the whole production obsolete, only the product step in question.2) It is easy to print the anode material of the invention on separator in the battery manufacture;3) The anode used in the invention reduces self discharge as it is made of hydrophobic ink and does not absorb electrolyte.5) The second consequence of the fact that no separate collector for the anode is needed in the first embodiment of the invention is that a battery comprising an anode of the invention becomes thinner6) High stability due to the hydrophobic property of the ink;

Problems solved by technology

The paste is quite viscous so that the electrolyte is not capable of flowing out.

The problem with this solution is, however, that the connection of the zinc strip to the collector is problematic and that the zinc self discharge is high because of lacking coverage.

Furthermore because of the low conductivity of the anode, an extra collector at the anode is needed.

However, also here, the hydrophilic zinc anode causes high zinc self discharge and unstable conductivity during the discharging process.

Another problem in traditional manufacturing methods to overcome is that the paper sheets become quite wet when they are impregnated with the electrolyte and also the paste remains wet after it is applied.

This situation influences on the surface properties of the layers so that further manufacturing steps will be difficult to carry out and makes the total manufacturing process of battery difficult.

As is well known, the zinc is quite easily oxidized under wet environment containing electrolyte salt and self-discharge is a problem.

Furthermore, the printing or coating of especially the anode paste is also difficult due to the fast changes of the properties of the paste.

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