JP2751389B2 - Method for producing positive electrode mixture for thermal battery and thermal battery using the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium / iron disulfide-based thermal battery, and more particularly, to reducing the internal resistance of a positive electrode during high-rate discharge to improve battery operating voltage and duration. It is a thing.

2. Description of the Related Art A thermal battery is inactive at room temperature, but becomes active when heated to a high temperature, and is a type of storage battery that can supply power to the outside. Therefore, even after storage for 5 to 10 years or more, the battery characteristics are not changed from that immediately after production, so that it is used as an emergency power supply. In addition, since the electrode is operated at a high temperature, the electrode reaction is easy to proceed and the polarization is small, so that it is excellent in large current discharge property, and furthermore, when a use signal is desired, power can be instantaneously taken out by inputting a start signal.

However, in recent years, increasingly large output current values have been desired, and the diffusion rate of lithium ions generated at the negative electrode to the positive electrode during high-rate discharge is rate-limiting, resulting in a shortage of lithium ions consumed in the positive electrode mixture. Becomes As a result, there is a disadvantage that the internal resistance of the unit cell increases and the operating voltage of the cell decreases.

In order to overcome this problem, researches that have been pursued in the past include the following: 1) The composition of the eutectic salt of potassium chloride and lithium chloride contained in the positive electrode mixture was shifted to the lithium chloride side to make it excessive, and A method for increasing lithium ions in an agent.

2) There is a method in which lithium oxide is added to the positive electrode mixture to increase lithium ions in the positive electrode.

Problems 1 to be Solved by the Invention According to the above 1), lithium chloride in the molten salt increases, and thus lithium ions also increase. However, the melting point of the molten salt increases, and it is necessary to increase the operating temperature of the battery when discharging. is there. For this reason, there is a disadvantage that the time required to reach the specified voltage, that is, the rise time is delayed. Further, in the case of a stacked battery, the number of heat generating agents and the number of heat retaining layers need to be increased, so that the size of the battery is increased. In the case of 2), since the solubility of lithium oxide in the molten salt is small, the desired amount of lithium ions is not increased, and thus the effect of addition is small.

The present invention solves the above-mentioned conventional problems,
Focusing on the method of adding lithium chloride, an object of the present invention is to realize a lithium / iron disulfide-based thermal battery in which the internal resistance of the positive electrode during high-rate discharge is reduced and the operating voltage is improved.

Means for Solving the Problems In order to solve this problem, the present invention provides an untreated iron disulfide, a potassium chloride-lithium chloride molten salt electrolyte, and lithium chloride in powder form, respectively. A step of mixing and stirring the added inorganic binder,
The mixture is heated in a high-temperature furnace through which argon, nitrogen, or a mixture of these gases flows, cooled in the furnace, and crushed in a dry atmosphere. This is to produce a mixture powder.

Then, using a lithium or lithium alloy for the negative electrode, a powder molded body of magnesium oxide (MgO) holding a potassium chloride-lithium chloride molten salt electrolyte for the electrolyte layer, and powder molding the positive electrode mixture for the positive electrode layer Layer 3
A unit cell having a layer, constituting the combined Li / FeS ₂ system thermal battery and a heating agent utilizing thermite Han'nai.

Effect By using this manufacturing method and the thermal battery, the increase in the internal resistance of the battery at the time of a high-rate load as in the related art is suppressed, and the operating voltage is also improved. That is, a large amount of lithium ions are consumed in the positive electrode during high-rate loading. However, according to the present invention, since lithium chloride is added in the positive electrode mixture, the amount of lithium ions is larger than that of a conventional battery, and Supply of lithium ions is performed smoothly.

As described above, it is possible to provide a thermal battery which is easy to manufacture and has a high operating voltage due to a small internal resistance of the battery.

Embodiment An embodiment of the present invention will be described below with reference to FIGS.
This will be described with reference to the drawings.

FIG. 1 shows a manufacturing process diagram of the positive electrode mixture. In the figure, Fe
66% by weight of S ₂ powder (the same applies hereinafter), lithium chloride-potassium chloride (LiCl-KCl) molten salt electrolyte (denoted by E) powder 12
%, A powder in which a LiCl-KCl molten salt electrolyte is held in a silicon dioxide (SiO ₂ ) binder (indicated by EB) 7%, LiCl 10
Weigh out 15% of 0 mesh pass powder. The amount of LiCl added is such that a part of the added LiCl is dissolved in the molten salt and the LiCl solid is present even at a melting point of 600 ° C., and is 5% to 20%.
And In FIG. 1, all these four types are put in a ball mill container, sealed, and rotated to obtain a uniform mixed powder.
This is transferred to a Pyrex glass container and placed in a floating electric furnace through which an inert gas such as an argon gas flows. Argon gas is 5-50 / kg / kg of the aforementioned mixture.
Keep flowing at min gas flow. At 5 / min or less, oxidation occurs due to inflow of air, and at 50 / min or more, it is uneconomical. The temperature of the electric furnace is raised to a temperature equal to or higher than the melting point of the electrolyte. Then, cooling while continuing to flow argon gas, 10
Withdraw the container below 0 ° C and transfer to a dry atmosphere. In this state, the mixture is pulverized in a mortar or the like and sized to 50 to 250 mesh to obtain a positive electrode mixture. Although EB is used here, the binder may be removed by slightly increasing the E ratio, or nitrogen gas (N ₂ ) or a mixed gas of Ar and N ₂ may be flowed instead of argon gas.

FIG. 2 is a cross-sectional view of a unit cell using the positive electrode mixture layer of the present invention.

In the figure, 1 is a positive electrode mixture layer, an appropriate amount is determined according to the relationship between the amount of discharge electricity and the utilization rate, a prescribed amount is weighed and placed in a mold, and after low-pressure preliminary molding, LiCl-KCl50 % Of an electrolyte powder made of a MgO binder impregnated and weighed and stacked, and then subjected to high-pressure molding to form an electrolyte layer 2 and obtain a two-layer integrated pellet. 3 is a negative electrode cup,
Reference numeral 4 denotes a negative active material layer composed of an integral mixed layer of pure lithium and iron powder or a lithium-aluminum alloy and E, which is disposed on the inner surface of the negative electrode cup 3. A unit cell.

FIG. 3 is a longitudinal sectional view of a laminated thermal battery assembled with the unit cells of FIG. 2 constituted by using the positive electrode mixture according to the manufacturing method of FIG.

In the drawing, reference numeral 6 denotes a unit cell shown in FIG. 2 in which a required number is easily laminated in series to easily obtain a desired voltage, and alternately with a heating agent 7 composed of a uniform mixture of potassium perchlorate and iron powder. To be laminated. Reference numerals 8 and 9 denote heat storage agent layers disposed above and below the laminate, for example, a layer composed of a mixed salt of lithium sulfate and sodium chloride and a SiO ₂ binder, which generate latent heat of solidification at 495 ° C. Maintain body temperature for a long time. This is a heat storage agent indispensable for extending the life of the battery. Reference numeral 10 denotes an igniter whose lead wire is connected to a pair of starting terminals 11. When a pulse current is supplied from this terminal, a flame is emitted and the heat pad 12 is burned, and the flame is transmitted to the squib 13. . The positive and negative output terminals 14 and 15 are connected to the internal lead wires 16 and 17 taken out from the top and bottom of the laminate. Numeral 18 denotes a heat insulating layer, which surrounded the stack by using a high-performance inorganic heat insulating material called Min-K. Reference numeral 19 denotes a battery cover, and reference numeral 20 denotes a battery case, both of which are made of stainless steel, and their fitting portions are welded and sealed.

The stacked thermal battery according to the present invention has a pair of starting terminals 11.
When the pulse current is applied from the above, the igniter 10, the heat pad 12, the squib 13, and the exothermic agent 7 are burned in this order, and the unit cell 6 is heated and started. The cell temperature rises to about 500 ° C, and the LiCl-K
When the Cl electrolyte is melted, the positive electrode mixture layer of the present invention starts discharging and supplies an output voltage having a high operating voltage even during high-rate discharging.

Next, the result of examining the effect of the present embodiment will be described. FIG. 4 shows a discharge test result of a current density of 1000 mA / cm ² in a battery shape of a unit cell having a diameter of 45 mm, a battery outer diameter of 49 mm, and a battery height of 35 mm.
The number of unit cells in series is 15, average operating voltage 2V / cell.

A in the figure shows a discharge curve according to the embodiment of the present invention,
The addition ratio of Cl is 15%. B shows Conventional Example 1 and is a battery using a positive electrode mixture without addition of lithium chloride. C shows Conventional Example 2 and is a battery using a positive electrode mixture obtained by adding lithium oxide. Battery B shows an average operating voltage of 27.6 V when compared with the initial battery operating voltage, which is 27.9 V higher than that of Battery A.
0.3V lower. The battery C has a flat operating voltage, but has a voltage level of 26.9 V, which is 1 V lower than that of the battery A.

The present invention A exhibited a battery operating voltage as high as 27.9 V at a discharge current density of 500 mA / cm ² or more, and exhibited an effect that a battery having a small internal resistance was obtained.

Effect of the Invention As is clear from the above description, after mixing lithium chloride with powder, heat treatment is performed in a high-temperature furnace in which argon gas, nitrogen gas, or a mixture of these gases is circulated, and then cooled in the furnace. Then, the positive electrode mixture powder that has passed through each step of pulverizing in a dry atmosphere is molded into a positive electrode mixture layer of a unit cell and used,
The stacked battery of the present invention in which this is combined with an exothermic agent has a high battery operating voltage and a low internal resistance at high rate discharge.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a positive electrode mixture according to an embodiment of the present invention, FIG. 2 is a sectional view of a unit cell in which the mixture is molded to form a positive electrode mixture layer, and FIG. FIG. 4 is a cross-sectional view of a stacked thermal battery in which unit cells are configured in series, and FIG. 4 is a comparison diagram of the discharge curves of the embodiment of the present invention and the conventional example. 1 ... positive electrode mixture layer, 2 ... electrolyte layer, 5 ... negative electrode, 6 ...
... unit cell, 7 ... heating agent.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Maki Fujimoto 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-59-173972 (JP, A)

Claims (5)

(57) [Claims] 1. A thermal battery having a negative electrode made of lithium or a lithium alloy, an electrolyte layer made of a molten salt of potassium chloride and lithium chloride, and a positive electrode made of iron disulfide, wherein the positive electrode contains at least iron disulfide, a molten salt and lithium chloride. After a process of mixing and stirring the mixture homogeneously, a process of performing a heat treatment in a high-temperature furnace through which argon, nitrogen, or a mixed gas is circulated, and a process of cooling in the furnace, pulverization is performed in a dry atmosphere. A method for producing a positive electrode mixture for a thermal battery, comprising the steps of: 2. The amount of lithium chloride added is 5 to iron disulfide.
2. The method for producing a positive electrode mixture for a thermal battery according to claim 1, wherein the amount is in the range of not less than 15% by weight and not more than 15% by weight. 3. The method for producing a positive electrode mixture for a thermal battery according to claim 1, wherein the amount of flowing gas is 5 to 50 / min with respect to 1 kg of the charged amount of the positive electrode mixture. 4. The method of claim 1, wherein the heat treatment temperature is in the range of 370 to 500 ° C. 5. A thermal battery using a positive electrode mixture layer comprising the positive electrode mixture powder for a thermal battery according to claim 1 as a unit cell.