JP4257192B2 - Non-aqueous electrolyte battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte battery, and more particularly to a wound non-aqueous electrolyte battery suitable for light load to medium load applications.

In a wound non-aqueous electrolyte battery using metallic lithium or a lithium alloy as the negative electrode active material, manganese dioxide or graphite fluoride is generally used as the positive electrode active material. For the positive electrode, paints are prepared by mixing these active materials with carbon and binder, which are conductive assistants, and applied to both sides of expanded metal and punching metal, which are positive electrode current collectors, or a positive electrode mixture sheet is produced. Then, it is obtained by pressure-bonding to both surfaces of the positive electrode current collector. Then, since the positive electrode plate is obtained by cutting into predetermined dimensions, the widths of the positive electrode mixture portion and the positive electrode current collector are the same.

For this reason, when the positive electrode width is the same as or smaller than the negative electrode width, the edge of the positive electrode faces the negative electrode. If the positive electrode edge mix is dropped or chipped, the positive electrode current collector is exposed and breaks through the separator, causing contact with the negative electrode and causing an internal short circuit, resulting in an increase in battery temperature and risk of ignition, rupture, etc. There is.

In order to avoid such a risk, the positive electrode width is generally wider than the negative electrode width. For this reason, at the end of discharge, the portion where the positive and negative electrode tensions are the highest, such as where the discharge reaction is concentrated, is likely to occur. The problem is that the designed battery capacity cannot be obtained. The problem that the metallic lithium is cut off becomes more prominent as the discharge current value becomes smaller.

It has been proposed to prevent the problem of breakage in the width direction of metallic lithium by making the negative electrode width wider than the positive electrode plate (see Patent Document 1). However, since the widths of the positive electrode mixture and the positive electrode current collector are the same, there is a risk of an internal short circuit due to the positive electrode current collector being exposed and breaking through the separator due to the mixture dropping or chipping at the positive electrode edge portion. In addition, even if the mixture does not fall off or chipped, there is a concern that the cathode current collector may break through the separator due to the cathode cutting surface stepping on the top or can bottom side of the wound body, causing an internal short circuit. The
JP-A-1-264176

In light of such circumstances, the present invention prevents non-short-circuiting due to a positive electrode current collector, is safe and reliable, and has a high capacity, such as a high-capacity lithium-manganese dioxide battery excellent in medium load to light load characteristics. The object is to provide a water electrolyte battery.

As a result of intensive studies to achieve the above object, the present inventors have determined that when the width of the negative electrode is larger than the width of the positive electrode, the portion of the negative electrode that does not face the positive electrode remains until the end of the discharge and does not break. Since the whole remains connected, the entire negative electrode facing the positive electrode can be consumed, and the capacity as designed can be obtained. At that time, the width of the positive electrode mixture sheet is larger than the width of the positive electrode current collector. Then, since the positive electrode current collector is wrapped in two positive electrode mixture sheets in the width direction, even if the negative electrode width is larger than the positive electrode width as described above, the positive electrode current collector at the positive electrode edge portion It was also found that a short circuit caused by body exposure can be prevented.

The present invention has been completed based on such knowledge.

That is, the present invention relates to two positive electrode composites produced by pressure-molding a long negative electrode using metallic lithium or lithium alloy as an active material and a positive electrode mixture containing an active material, a conductive additive and a binder. In a non-aqueous electrolyte battery having an electrode group in which an agent sheet and a long positive electrode made of a positive electrode current collector sandwiched between both sheets are wound through a separator, the width of the negative electrode is larger than the width of the positive electrode The non-aqueous electrolyte battery is characterized in that it is designed to be large and the width of the two positive electrode mixture sheets is designed to be larger than the width of the positive electrode current collector.

Thus, since the non-aqueous electrolyte battery of the present invention is designed so that the width of the negative electrode is larger than the width of the positive electrode, only the portion of lithium that does not face the positive electrode remains without being discharged. Since the remaining portions are connected without being disconnected, the entire lithium facing the positive electrode can be consumed, and a high capacity can be obtained. Moreover, since the width | variety of two positive mix sheets is designed larger than the width | variety of a positive electrode electrical power collector, a short circuit defect does not occur.

That is, it is possible to provide an excellent nonaqueous electrolyte battery that has high yield and capacity. Such an effect is particularly prominent in applications with medium to light loads such as gas meters and electric power meters.

In the present invention, metallic lithium or a lithium alloy (for example, an alloy of lithium and aluminum) is used as the negative electrode active material. In the present invention, a long negative electrode made of these active materials is used, but it is important that the width of the negative electrode is designed to be larger than the width of the positive electrode. Usually, it is designed to be about 0.5 to 5 mm larger than the width of the positive electrode.

In the present invention, manganese dioxide, carbon fluoride, lithium cobalt composite oxide, spinel-type lithium manganese composite oxide, or the like is used as the positive electrode active material. In addition, graphite, carbon black, acetylene black, and the like are used as the conductive aid for the positive electrode, and it is desirable to use carbon black as the main component. Further, PTFE (polytetrafluoroethylene) dispersion, powdered PTFE, rubber binder, or the like is used for the positive electrode binder, but it is preferable to use PTFE dispersion.

In the present invention, a positive electrode mixture composed of the positive electrode active material, a conductive aid, a binder, and the like is pressure-molded to produce a positive electrode mixture sheet having a predetermined thickness. The two positive electrode mixture sheets and the positive electrode current collector sandwiched between the two sheets constitute a long positive electrode. As described above, the width of the positive electrode is designed to be smaller than the width of the negative electrode, but at the same time, it is important that the width of the two positive electrode mixture sheets is designed to be larger than the width of the positive electrode current collector. Usually, it is designed to be about 1 to 5 mm larger than the width of the positive electrode current collector.

The positive electrode current collector is not particularly limited, and a plain woven wire mesh, expanded metal, lath mesh, punching metal, and foil made of stainless steel 316, 430, 444, or the like can be used. In general, a conductive paint is applied to these positive electrode current collectors, and as this conductive paint, a carbon paste, a silver paste, or the like is used.

In this invention, an electrode group is comprised by winding the elongate negative electrode and elongate positive electrode of the said structure through a separator. The separator is not particularly limited, and for example, non-woven cloth such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylsulfone (PPS), and microporous A film or the like is used.

In the present invention, the above-described electrode group is loaded into a battery container, and a nonaqueous electrolyte solution is injected into the battery container and sealed to obtain a nonaqueous electrolyte battery.

As the non-aqueous electrolyte, a mixed solvent obtained by mixing a cyclic carbonate such as propylene carbonate (PC) or ethylene carbonate (EC) with a chain ether such as dimethoxyethane (DME), and LiPF ₆ or LiClO ₄ as a solute. , (CF ₃ SO ₂ ) ₂ NLi or the like is used in an electrolyte solution of about 0.3 to 1.5 mol / liter.

The above battery container is generally a bottomed cylindrical container made of iron or stainless steel, the lid is sealed with laser welding or a crimp seal through packing, and the positive and negative electrodes are insulated with glass or resin. Isolated through the body. Normally, a thin part is provided on the lid or the bottom of the can, and a vent is provided as a countermeasure when the internal pressure suddenly increases.

The non-aqueous electrolyte battery of the present invention configured as described above includes various types of known non-aqueous electrolyte batteries such as a lithium-manganese dioxide battery (CR) and a lithium-fluorinated carbon battery (BR). The Moreover, as long as it has the electrode group of the specific structure mentioned above, there is no limitation in particular regarding the shape etc., A various thing is included.

In the following, regarding a cylindrical lithium-manganese dioxide battery (CR battery), “Example 1” of the present invention and “Comparative Examples 1 to 3” corresponding thereto are described, including a battery manufacturing method (see FIG. A more specific description will be given with reference to FIGS.

<Preparation of positive electrode mixture>
After mixing for 5 minutes in a dry manner using a planetary mixer at a ratio of 3% by weight of carbon black and 92% by weight of manganese dioxide, 20% by weight of solids were added by weight and mixed for 5 minutes. . Polytetrafluoroethylene (PTFE) disversion was added in the form of 5% by weight diluted to the remaining water as a solid content and mixed for 5 minutes. The water content in the compounding agent was adjusted to 25 to 30 parts by weight with respect to 100 parts by weight of the solid content.

<Preparation of positive electrode mixture sheet>
Using the above-mentioned compounding agent with two rolls having a diameter of 25 mm, adjusting the roll temperature to 130 ± 5 ° C., rolling with a roll at a press pressure of 7 ton / cm, a roll interval of 0.4 mm, and a rotation speed of 10 rpm, and sheeting went. The compounding agent (preliminary sheet) that passed through the roll was dried at 105 ± 5 ° C. until the residual moisture was 2% by weight or less. The dried preliminary sheet was pulverized until it became twice or more the original apparent volume. Most of the pulverized particle diameter was 1 mm or less, and the PTFE fiber added as a binder was cut to a length of 1 mm or less.

Using the pulverized material in this manner, the sheet was formed again by a roll. That is, the interval between the rolls was adjusted to 0.6 ± 0.05 mm, the roll temperature was 120 ± 10 ° C., the press pressure was 7 tons / cm, and the sheet was formed at a rotation speed of 10 rpm. The sheet thus obtained had a thickness of 1.0 mm and a density of 2.6 g / cm ³ .

The above sheet formation is merely an example of preparing a positive electrode mixture sheet, and mixing, preliminary sheet formation, pulverization, and sheet formation may be performed depending on the composition of the compounding agent, the required sheet thickness, density, and the like. Needless to say, the conditions can be appropriately changed.

<Preparation of positive electrode current collector>
As the positive electrode current collector, an expanded metal of stainless steel 316 was used. The expanded metal was cut into a width of 34 mm and a length of 56 mm, and a stainless steel ribbon having a thickness of 0.1 mm and a width of 3 mm was attached thereto as a current collecting lead by resistance welding. The positive electrode current collector was coated with carbon paste so as not to crush the mesh (about 4 to 5 mg / cm ² ). The positive electrode current collector coated with the carbon paste was dried at 105 ± 5 ° C. for 2 hours or more.

<Pressure bonding of positive electrode mixture sheet to positive electrode current collector>
Two sheets of the positive electrode mixture sheet prepared by the above method were prepared on the outer peripheral side and the inner peripheral side. That is, as shown in FIG. 3 (c), the positive electrode mixture sheet 20 located on the inner peripheral side was short, cut to a width of 37 mm and a length of 51 mm. Further, the positive electrode mixture sheet 21 located on the outer peripheral side was cut to a width of 37 mm and a length of 62 mm.

Of these, the two positive electrode mixture sheets 20 and 21 on the outer peripheral side and the positive electrode current collector 22 produced by the above method are aligned at one end, as shown in FIG. The end of the body 22 was set so as not to protrude from the mixture, and 3 to 10 mm (S portion in the figure) was pressed from the end on the core side by pressing so that the three pieces were not separated. Thus, the positive electrode mixture sheets 20 and 21 partially fixed to the positive electrode current collector 22 were dried with hot air at 250 ± 10 ° C. for 6 hours to prepare the positive electrode 3. Note that the partial fixing by the above-mentioned crimping is for improving workability, and there is no problem in characteristics even if it is transferred to the next winding step without performing such partial fixing.

<Production of negative electrode>
As shown in FIGS. 3B and 3C, the negative electrode 4 made of a lithium electrode has 46 mm (4a in the figure) and 82 mm (4b in the figure) foils having a width of 40 mm and a thickness of 0.3 mm. 1) and crimping the negative electrode current collecting lead 24 as shown in FIGS. 1 and 2, excluding 10 mm from one end of the foil of the shorter side 4a, and crimping 36mm on the long foil 4b. .

<Battery assembly>
As shown in FIG. 3A, a microporous separator 5 made of polyethylene having a width of 44 mm and a thickness of 0.025 mm is cut into 220 mm and sandwiched between two cores 25 having a diameter of 4 mm, Wound around. Next, as shown in FIG. 3 (b), the negative electrode 4 having a single length of 10 mm was wound around the separator 5 with one turn of the negative electrode 4. Further, as shown in FIG. 3 (c), the positive electrode 3 is placed so that the side (S portion) to which the positive electrode mixture sheets 20, 21 are fixed is on the core side, and the end portion of the positive electrode 3 is It wound so that it might not protrude from the negative electrode 4 (winding direction E). After finishing the winding, the separator completely covered the outermost periphery, and the winding end portion of the separator was fixed with a fixing tape. The separator that protruded on both sides of the positive and negative electrodes was folded so that the positive electrode mixture sheet was covered with the folded separator.

Next, as shown in FIGS. 1 and 2, the electrode group 6 made of the wound body obtained as described above is formed on the bottom 2a of the negative electrode can 2 made of a nickel-plated iron can with a thickness of 0.2 mm. The polypropylene bottom insulating plate 23 was inserted, and each terminal of the wound body was inserted up. The negative electrode current collecting lead 24 was resistance welded to the upper inner surface of the can. Further, the positive electrode current collecting lead 15 was inserted into the upper insulating plate 12 and then resistance welded to the positive electrode lead 10 constituting the battery cover. At this time, it was confirmed that there was no short circuit by measuring the insulation resistance.

Next, as a non-aqueous electrolyte, an electrolyte in which 0.5 mol / liter of LiClO ₄ was dissolved as an electrolyte in a mixed solvent of propylene carbonate (PC) and dimethoxyethane (DME) in a weight ratio of 1: 2 was prepared, 3.3 ± 0.1 ml of this electrolyte was injected into the battery can. The injection was divided into three times, and the whole amount was injected under reduced pressure in the final step.

After the injection of the electrolyte, the battery lid was fitted, and the outer periphery was laser welded and sealed. Thereafter, preliminary discharge was performed at a resistance of 1Ω for 30 seconds, and storage was performed at 45 ° C. for 24 hours, and then secondary preliminary discharge was performed at a constant current of 1 A for 3 minutes. Further, a cylindrical lithium-manganese dioxide battery having an outer diameter of 17.0 mm and a total height of 45.0 mm was produced by aging at room temperature for 7 days.

1 and 2 show a longitudinal sectional view and a transverse sectional view of the lithium-manganese dioxide battery 1 manufactured as described above. In the figure, 11 and 13 are upper insulating plates similar to the upper insulating plate 12 disposed above the electrode group 6, 11 and 12 constitute a horizontal portion, and 13 constitutes a vertical portion. Yes. Reference numeral 14 denotes a vent hole provided in the upper insulating plate. Reference numeral 8 denotes a battery lid, and reference numeral 9 denotes an insulating gasket in which the battery lid 8 and the positive electrode lead 10 are sealed and fixed. Other reference numerals are as described above, and the same components as those shown in FIG. 3 are denoted by the same reference numerals as those in FIG.

Comparative Example 1
A cylindrical lithium-manganese dioxide battery was produced in the same manner as in Example 1 except that the width of the positive electrode current collector was 37 mm, which was the same as that of the positive electrode mixture sheet.

Comparative Example 2
A cylindrical lithium-manganese dioxide battery was produced in the same manner as in Example 1 except that the width of the negative electrode (lithium electrode) was 37 mm, which was the same as that of the positive electrode mixture sheet.

Comparative Example 3
A cylindrical lithium-manganese dioxide battery was produced in the same manner as in Example 1 except that the width of the negative electrode (lithium electrode) was 35 mm.

About each lithium-manganese dioxide battery of said Example 1 and Comparative Examples 1-3, the number of short-circuit defects (pieces / 100 pieces) on the next day when 100 pieces were assembled and 10 pieces were discharged at a constant current of 5 mA. The average value of the discharge capacity was examined. These measurement results were as shown in Table 1. In Table 1, the width (mm) of each of the negative electrode, the positive electrode mixture sheet, and the positive electrode current collector of the battery is shown for reference.

Table 1
┌────┬────┬──────┬─────┬┬──────┬─────┐
│ │ Negative electrode width │ Positive electrode mixture sheet │ Positive electrode current collector │ Number of short-circuit defects │ 5 mA capacity │
│ │ (mm) │ Groove width (mm) │ Width (mm) │ (pieces / 100 pieces) │ (mAh) │
├────┼────┼──────┼─────┼┼──────┼─────┤
│Example 1│ 40 │ 37 │ 34 │ 0 │2,627│
├────┼────┼──────┼─────┼┼──────┼─────┤
│Comparative Example 1│ 40 │ 37 │ 37 │ 6 │2,635
│ │ │ │ │ │ │
│Comparative Example 2│ 37 │ 37 │ 34 │ 0 │2,453│
│ │ │ │ │ │ │
│Comparative Example 3│ 35 │ 37 │ 34 │ 0 │2,462│
└────┴────┴──────┴─────┴┴──────┴─────┘

From the results shown in Table 1, the battery of Example 1 does not cause short circuit failure and has a high discharge capacity. This is probably because a short-circuit failure did not occur because the positive electrode current collector was wrapped in the positive electrode mixture sheet. Further, when the battery that had been discharged was disassembled, only the portion of lithium that did not face the positive electrode remained without being discharged. Since the remaining portion is connected to the lithium without being cut, the entire lithium facing the positive electrode can be consumed, and a high capacity is considered to be obtained. Also from this result, it can be seen that the present invention can provide an excellent nonaqueous electrolyte battery with high yield and capacity.

On the other hand, in the battery of Comparative Example 1, the capacity was almost the same as in Example 1, but the number of short-circuit defects was as high as 6 and a short circuit occurred. This is because the positive electrode mixture sheet and the positive electrode current collector have the same width and the negative electrode lithium is wider than them, so that the positive electrode current collector steps on the lithium at the top of the wound body or on the bottom of the can. It seems to have done.

Moreover, in both batteries of Comparative Examples 2 and 3, no short-circuit failure occurred, but the discharge capacity was small. When these batteries were disassembled, it was confirmed that the lithium was cut and partially remained without being discharged. In these batteries, the width of lithium is the same as or narrower than that of the positive electrode mixture sheet, so in parts where the discharge reaction is more likely to occur, such as where the positive and negative electrodes are tight, the lithium breaks and the current collector leads It seems that the electrical connection was cut and the discharge capacity was reduced.

It is a longitudinal section showing an example of the nonaqueous electrolysis battery of the present invention. It is a cross-sectional view of said nonaqueous electrolysis battery. It is an assembly process figure of said nonaqueous electrolysis battery, (a) is in the state where the separator was sandwiched between winding cores, (b) is in the state where the negative electrode is wound simultaneously with the above separator, (c) is further in the positive electrode Each of the winding states is shown.

Explanation of symbols

1 Non-aqueous electrolyte battery (lithium-manganese dioxide battery)
2 Negative electrode can 2a Can bottom 3 Positive electrode S Core side end of positive electrode E Winding direction of positive electrode 4 (4a, 4b) Negative electrode (lithium electrode)
5 Separator 6 Electrode group (winding body)
8 Battery cover 9 Insulating gasket 10 Positive electrode lead (battery cover)
11, 12 Upper insulation plate (horizontal part)
13 Upper insulation plate (vertical part)
14 Gas vent hole 15 Positive electrode current collecting lead 20, 21 Positive electrode mixture sheet 22 Positive electrode current collector 23 Bottom insulating plate 24 Negative electrode current collecting lead 25 Core

Claims (1)

Between two sheets of positive electrode mixture sheets prepared by press-molding a long negative electrode using metal lithium or lithium alloy as an active material and a positive electrode mixture containing an active material, a conductive additive and a binder, and both sheets In a non-aqueous electrolyte battery having an electrode group obtained by winding a long positive electrode made of a positive electrode current collector sandwiched between two via a separator, the width of the negative electrode is designed to be larger than the width of the positive electrode A nonaqueous electrolyte battery characterized in that the width of the two positive electrode mixture sheets is designed to be larger than the width of the positive electrode current collector.

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