JPH04322065A - Manufacture of alkaline secondary battery - Google Patents

Abstract

PURPOSE:To improve charging characteristic at high temperature and to improve discharging characteristic at low temperature by individually injecting at least two kinds of alkalline electrolytes of different lithium ion concentrations into battery cans stored in an electrode group. CONSTITUTION:Alkaline electrodes of different lithium ion concentrations are injected into an electrode group of battery cans, and are infiltrated gradually downward as in a layered manner in the order they are injected, until the electrolyte comes into electrode and is thus fixed. A layer portion of high lithium ion concentration and a layer portion of low lithium ion concentration are created in the battery can. In the portion where the concentration is high, charging characteristic at high temperature including in a case of oxygen excessive voltage at the time of charging at high temperature is improved. In the portion of low concentration, generation of NiOOH under excessive charging is suppressed, and discharging characteristic, in particular the discharging characteristic at low temperature is improved. As a result, an alkaline battery excellent in charging/discharging characteristics and in large current discharging characteristics in a wide temperature range is manufactured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an alkaline secondary battery.

0002

BACKGROUND OF THE INVENTION In recent years, electronic devices have become more portable and cordless due to higher integration of electronic components and advances in packaging technology. Along with this, the number of electronic devices used outdoors is increasing. For this reason, alkaline secondary batteries for driving such electronic devices are required to have a high capacity and to be usable over a wide temperature range.

In order to meet the above-mentioned demand for higher capacity, nickel-cadmium secondary batteries have been developed by improving the battery structure, increasing the utilization rate of the nickel electrode, which is a capacity-limiting electrode, or changing from a sintered electrode to a paste type. By using it as an electrode, battery capacity has been improved by about 40%. Furthermore, nickel-metal hydride secondary batteries using a hydrogen storage alloy for the negative electrode have been developed with battery capacity approximately twice that of nickel-cadmium secondary batteries.

On the other hand, in response to the requirement for use in a wide temperature range, battery characteristics in a specific temperature range can be improved by adding cadmium to the nickel electrode or adding lithium ions or sodium ions to the alkaline electrolyte. known to improve. However, it is difficult to obtain good battery characteristics over a wide temperature range. Further, the improvement by adding cadmium is not preferable from the viewpoint of environmental problems. Furthermore, as the capacity increases, the usable temperature range tends to become narrower. For this reason, it has been necessary to prepare many types of conventional alkaline secondary batteries, such as those for high temperatures, those for low temperatures, and those for large current discharge, depending on the application.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and it is an object of the present invention to provide a method for manufacturing an alkaline secondary battery that has good battery characteristics over a wide temperature range. It is something to do.

[0006]

[Means for Solving the Problems] The present invention is characterized by comprising the step of separately injecting at least two types of alkaline electrolytes having different lithium ion concentrations into a battery can housing an electrode group. This is a method for manufacturing an alkaline secondary battery.

[0007] The at least two types of alkaline electrolytes having different lithium ion concentrations are, for example, a combination of aqueous solutions in which different amounts of lithium hydroxide are dissolved in potassium hydroxide or sodium hydroxide, or a combination of the above aqueous solution and a solution containing no lithium ions. Combinations with potassium hydroxide aqueous solution and sodium hydroxide aqueous solution can be mentioned. It is desirable to use such a combination of alkaline electrolytes prepared so that the difference in normality of lithium hydroxide is 0.5N or more.

[0008] The alkaline electrolyte is preferably injected in order of increasing lithium ion concentration from the viewpoint of further improving battery characteristics. Further, from the viewpoint of further improving battery characteristics, it is desirable that the interval (standing time) when switching to a different type of alkaline electrolyte to be injected is 30 seconds or more.

Examples of the positive electrode constituting the electrode group include a nickel electrode, and examples of the negative electrode constituting the electrode group include a hydrogen storage alloy electrode, a cadmium electrode, and the like. For example, in the case of an electrode group in which a separator is interposed between a non-sintered nickel positive electrode and a hydrogen storage alloy negative electrode, the configuration will be described below.

[0010] The above-mentioned non-sintered nickel positive electrode uses a mixture of nickel hydroxide as an active material, a binder, and cobalt oxide as necessary, on a conductive core as a current collector. Examples include those that have been formed.

[0011] Examples of the binder to be incorporated into the positive electrode mixture include polyacrylates such as sodium polyacrylate and potassium polyacrylate, and carboxymethyl cellulose (CMC). The blending ratio of such a binder is preferably in the range of 0.1 to 2 parts by weight per 100 parts by weight of nickel hydroxide.

The conductive core of the positive electrode may have a two-dimensional structure such as punched metal, expanded metal, or wire mesh, or a three-dimensional structure such as foamed metal, a sintered substrate of metal fibers, or a felt-like metal porous body. Examples include things such as.

[0013] The non-sintered nickel positive electrode is prepared by, for example, kneading the nickel hydroxide, a binder, cobalt oxide, etc. in the presence of water to prepare a paste, and applying this paste to the conductive core. After drying, it is manufactured by roller pressing. Examples of the hydrogen storage alloy negative electrode include those in which a mixture of a hydrogen storage alloy powder, a conductive material powder, and a binder is formed on a conductive core serving as a current collector.

The hydrogen storage alloy to be mixed in the negative electrode mixture is not particularly limited, and is capable of storing hydrogen electrochemically generated in the electrolyte and capable of absorbing the stored hydrogen during discharge. Any material that can be easily released may be used. For example, the general formula XY5-a Za (where X is a rare earth element including La, Y is Ni, Z is Co, Mn, Al, Fe
, Ti, Cu, Zn, Zr, Cr, V, and B (a represents 0≦a<2.0). Specifically, LaNi5,
Co, M
n, Al, Fe, Ti, Cu, Zn, Zr, Cr, V,
Examples include multi-element compounds substituted with elements such as B.

[0015] Examples of the conductive material powder blended in the negative electrode mixture include carbon black, graphite, and acetylene black. The blending ratio of the conductive material powder is 0 to 100 parts by weight of the hydrogen storage alloy powder.
．． The amount is preferably in the range of 1 to 4 parts by weight. A more preferable blending ratio of the conductive powder is hydrogen storage alloy powder 100%
It ranges from 0.1 to 2 parts by weight.

[0016] Examples of the binder blended in the negative electrode mixture include polyacrylates such as sodium polyacrylate and potassium polyacrylate, fluororesins such as polytetrafluoroethylene (PTFE), and Examples include carboxymethylcellulose (CMC). The blending ratio of such a binder is 100% hydrogen storage alloy powder
It is desirable that the amount is in the range of 0.1 to 5 parts by weight.

The conductive core of the negative electrode may be, for example, a two-dimensional structure such as punched metal, expanded metal, or wire mesh, or a three-dimensional structure such as a foamed metal, a sintered substrate of metal fibers, or a felt-like metal porous body. Examples include things such as.

The hydrogen storage alloy negative electrode is prepared by, for example, preparing a paste by kneading the hydrogen storage alloy powder, conductive material powder, binder, etc. in the presence of water, and applying this paste to the conductive core. After drying, it is manufactured by roller pressing.

The separator interposed between the non-sintered nickel positive electrode and the hydrogen storage alloy negative electrode may be a nonwoven fabric made of synthetic resin such as nylon or polypropylene.

[0020]

[Function] Regarding the temperature characteristics of alkaline secondary batteries, at high temperatures, the discharge characteristics improve, but the charging characteristics, especially the charging efficiency related to charge acceptance, decrease, and at low temperatures, although the charging characteristics are good, the discharge characteristics deteriorate. Therefore, by improving the charging characteristics at high temperatures and the discharging characteristics at low temperatures, good battery characteristics can be obtained over a wide temperature range.

In the manufacturing method of the present invention, at least two types of alkaline electrolytes having different lithium ion concentrations are separately injected into a battery can housing an electrode group. As a result, alkaline electrolytes with different lithium ion concentrations permeate downward into the electrode group in the battery can in the order in which they were injected, forming layers. The lithium ions in the alkaline electrolyte that have permeated in this way, unlike potassium ions, sodium ions, etc., enter the electrode (for example, a nickel electrode) and are fixed. Therefore, a layered portion with a high lithium ion concentration and a layered portion with a low lithium ion concentration (or a layered portion with only potassium ions or sodium ions) are created in the battery can. The portions with high lithium ion concentration increase oxygen overvoltage during high temperature charging and improve charging characteristics at high temperatures. In addition, the region with a low lithium ion concentration suppresses the formation of γ-NiOOH during overcharging and improves discharge characteristics, particularly discharge characteristics at low temperatures. As a result, an alkaline secondary battery with excellent charge/discharge characteristics and large current discharge characteristics over a wide temperature range can be manufactured.

[0022] By changing the ratio of the injection amount of alkaline electrolyte with high lithium ion concentration and alkaline electrolyte with low lithium ion concentration, it is possible to control the balance of battery characteristics at high temperature and low temperature. can.

[0023]

EXAMPLES Examples of the present invention will be described in detail below. Examples 1-4 and Comparative Examples 1-3

First, 90 parts by weight of nickel hydroxide, 10 parts by weight of cobalt oxide as an additive, 0.3 parts by weight of CMC as a binder, and 0.3 parts by weight of sodium polyacrylate were mixed and then stirred. A positive electrode active material paste was prepared by adding water until it became paste-like. Continuing,
This positive electrode active material paste was filled into a felt-like porous metal body, dried, and pressed to produce a paste-type nickel electrode.

On the other hand, lanthanum-enriched misch metal (Lm
), nickel, cobalt, manganese, and aluminum with a composition of LmNi4.0 Co0.4 Mn0.3 Al0
．． After weighing and mixing so as to give a hydrogen storage alloy ingot of 3, the mixture was melted and cooled in a high frequency induction furnace to produce a hydrogen storage alloy ingot. Subsequently, this ingot was heat treated in an electric furnace and then ground to obtain a hydrogen storage alloy powder. 1% by weight of carbon black and 0.5% by weight of CMC were added to the obtained hydrogen storage alloy powder.
, and 0.5% by weight of sodium polyacrylate, and then water was added with stirring until it became paste-like to prepare a negative electrode active material paste. Subsequently, this negative electrode active material paste was applied to a punched metal, dried, and pressed to produce a hydrogen storage alloy electrode.

Next, the paste-type nickel electrode and the hydrogen storage alloy electrode were wound together with a nylon separator interposed therebetween to produce an AA-sized electrode group, which was inserted into a battery can. Subsequently, an alkaline electrolyte having the composition and amount shown in Table 1 below was injected into the battery can by the means shown in Table 1, and the can was sealed to produce a nickel-metal hydride secondary battery.

After the batteries of Examples 1 to 4 and Comparative Examples 1 to 3 thus obtained were initially charged at 0.1 CmA for 15 hours,
It was discharged to 0.8V at 1A. Continuing, 1/ at 20℃
After charging at 3CmA for 5 hours, 0.8V at 1A at 20℃
Repeat charging and discharging for 10 cycles under conditions of discharging until 1
The discharge capacity at the 0th cycle was measured as the reference capacity.

Next, the batteries of Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to a high temperature charging test in which they were charged to 150% at 0.1 CmA at 45° C. and then discharged to 0.8 V at 1 A at 20° C. . Also, 150% at 1/3CmA at 20℃
After charging, a low temperature discharge test was conducted in which the battery was discharged to 0.8V at 3A at 0°C. The discharge capacity in these high-temperature charge tests and low-temperature discharge tests was measured, and the ratio to the reference capacity was determined. The results are also listed in Table 1.

[0029]

[Table 1]

As is clear from Table 1, the batteries of Examples 1 to 4 have better charging characteristics at high temperatures than the battery of Comparative Example 1. This is due to the fact that there are areas with high lithium ion concentration inside the battery can. In addition, Examples 1 to 4
The battery also has excellent discharge characteristics at low temperatures compared to the batteries of Comparative Examples 2 and 3. This is because there are areas within the battery can where the concentration of lithium ions is low or where lithium ions are absent.

Further, when comparing Examples 1 and 2, it can be seen that Example 1, in which an electrolytic solution with a high lithium ion concentration was first injected, had better battery characteristics. This is because regions with high lithium ion concentration and regions with low lithium ion concentration are formed uniformly.

Furthermore, when comparing Examples 1, 3, and 4, it was found that Example 3, in which the interval between injections of different types of alkaline electrolytes was less than 30 seconds, had inferior discharge characteristics at low temperatures. I understand. This is because if the interval between injections is less than 30 seconds, an electrolyte with a different concentration will be injected before the injected lithium ions are absorbed by the nickel electrode, resulting in areas with high lithium ion concentrations. This is because the low-temperature and low-temperature regions become unclear, and the effect of improving discharge characteristics at low temperatures becomes small.

Therefore, especially when an alkaline electrolyte with a high lithium ion concentration is first injected, an alkaline electrolyte with a low lithium ion concentration or an alkaline electrolyte containing no lithium ions is injected, and when switching between injections, If the interval is 30 seconds or more, the charging characteristics at high temperatures can be sufficiently improved, and the discharging characteristics at low temperatures can also be sufficiently improved, resulting in a battery with excellent charging and discharging characteristics and large current discharging characteristics over a wide temperature range. You can see what you can get.

[0034] In the above example, an AA size nickel-metal hydride secondary battery was described, but similar effects were obtained with larger A size batteries. Furthermore, similar effects were obtained with nickel-cadmium secondary batteries.

[0035]Also, in the above example, the case where two types of alkaline electrolytes with different lithium ion concentrations were used was explained, but three or more types of alkaline electrolytes with different lithium ion concentrations were prepared, and these were separately used in the battery. By injecting the liquid into the can, it is possible to finely improve battery characteristics in a specific temperature range.

[0036]

Effects of the Invention As detailed above, an alkali which can improve charging characteristics at high temperatures and discharge characteristics at low temperatures, and has excellent battery characteristics such as charging and discharging characteristics and large current discharging characteristics over a wide temperature range. A method for manufacturing a secondary battery can be provided.

Claims (1)

[Claims] 1. A method for manufacturing an alkaline secondary battery, comprising the step of separately injecting at least two types of alkaline electrolytes having different lithium ion concentrations into a battery can housing an electrode group.