JPS6394559A - Spiral electrode for cylinder type nonaqueous electrolyte cell - Google Patents

Abstract

PURPOSE:To improve the reaction utilization factor of MnO2 by specifying average grain sizes of MnO2 powder used as a positive electrode active material constituting a positive electrode black mix and two kinds of graphite powder used as a conductive agent. CONSTITUTION:Graphite powder consists of two kinds having different average grain sizes, the average grain size of one graphite powder is larger than that of the other graphite powder but smaller than that of manganese dioxide powder. The graphite powder having a smaller average grain size exists on the surface of MnO2 powder and forms electrochemical reaction type reaction sites on the surface of MnO2 powder. On the other hand, the graphite powder having a larger average grain size exists among the MnO2 powder holding the graphite powder having a smaller average grain size and forms a conductive passage. Accordingly, many reaction sites are formed, the electric conductivity of the whole positive electrode is increased, and the reaction utilization factor of MnO2 can be improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a spiral electrode for a cylindrical non-aqueous electrolyte battery.
More specifically, the present invention relates to a spiral electrode for a cylindrical non-aqueous electrolyte battery that is free from internal short circuits, has a high reaction utilization rate of manganese dioxide (Mn02) as a positive electrode active material, and therefore has a large discharge capacity.

(Prior Art) In recent years, demand for cylindrical non-aqueous electrolyte batteries has been rapidly increasing as an alternative to conventionally used cylindrical dry batteries and cylindrical alkaline batteries.

An example of the structure of such a cylindrical non-aqueous electrolyte battery will be described with reference to a partially cutaway longitudinal sectional view shown in FIG.

In FIG. 1, 1 is a positive electrode, and M is a positive electrode active material.
A sheet of a positive electrode mixture consisting of nO2 powder, graphite powder as a conductive agent, and a binder such as polytetrafluoroethylene is supported on a current collector such as punched metal. 2 is a negative electrode made of, for example, a sheet of metal lithium.

3 is a separator made of a nonwoven fabric such as polypropylene, which includes, for example, propylene carbonate and 1.
It is impregnated with an electrolyte solution in which an electrolyte such as lithium perchlorate is dissolved at a predetermined concentration in a mixed solvent of 2-dimethoxyethane. 4 is each negative electrode made of, for example, nickel-plated iron. Each negative electrode 4 houses a spiral electrode in which a laminated sheet in which a positive electrode 1 and a negative electrode 2 are stacked with a separator 3 interposed therebetween is spirally wound around a positive current collector rod 5 . In addition, in this spiral electrode, the outermost periphery of the negative electrode 2 is in contact with the inner wall surface of each negative electrode 4. 6 is, for example,
It is an insulating plate made of polypropylene, and is interposed between the inner bottom surface of each negative electrode 4, the positive electrode current collector rod 5, and the spiral electrode.

6' is an insulator made of, for example, polypropylene, and there is a gap between the positive electrode current collector rod 5, a sealing plate 7 made of, for example, 5US304, which also serves as the spiral electrode and the positive terminal, and an insulating ring 8 made of, for example, polypropylene. Intervening.

(Problems to be Solved by the Invention) As described above, in the cylindrical non-aqueous electrolyte battery, the spiral electrode is housed within the battery container.

By the way, in the case of this spiral electrode, as mentioned above, it is formed by winding a laminated sheet consisting of a sheet of positive electrode mixture, a separator, and a negative electrode sheet, but at this time, the separator and negative electrode each have their own strength. However, the positive electrode mixture sheet is
Since it is a molded sheet made of powder bound together, it often peels off from the current collector during winding, which can lead to internal short circuits.

Therefore, the positive electrode mixture is required to not peel off from the current collector during winding. This requires that the positive electrode mixture has appropriate flexibility and at the same time has high mechanical strength.

On the other hand, in the positive electrode mixture, the active material M n O2
It is desirable that the reaction utilization rate of the powder be as high as possible, and this is regulated by the existing forms of the active material and the conductive agent. In other words, the reaction utilization rate of the active material is
It is regulated by the number of electrochemical reaction sites formed on the surface of the nO2 powder and the conductive path formed by the presence of a conductive agent between the MnO□ powders.

Therefore, from the viewpoint of increasing the reaction utilization rate of M n O2, it is important that there are a large number of conductive agents present on the surface of M n O2 powder, and that M n O2 generated as the discharge reaction progresses.
It is required that the expansion of nO2 does not cause the conductive agents forming the conductive path between Mn02 to separate from each other and cause the conductive path to collapse.

Therefore, in order to give the positive electrode mixture appropriate flexibility and increase mechanical strength, 100 parts by weight of MnO2 powder, 7 to 12 parts by weight of graphite powder, and 0.5 parts by weight of carbon black were added.
It has been disclosed that a positive electrode mixture of ~1.5 parts by weight is kneaded with a binder (Japanese Patent Application Laid-Open No. 59-230257
(see publication).

However, since carbon black has elasticity due to its structure, when carbon black is added, the thickness of the positive electrode plate increases over time after forming the positive electrode plate. Therefore, even if the strength of the positive electrode plate is increased, there is a problem in controlling its thickness.

Furthermore, in order to increase the reaction utilization rate of M n O2, which is the positive electrode active material, regarding coin-shaped nonaqueous electrolyte batteries, (1)
It is possible to use M n O2 powder with an average particle size of 104 or less (see Japanese Patent Application Laid-open No. 57-05964), and (2) to use M n O2 powder with an average particle size of 0.1 to 30 and It is possible to mix carbon powder of .05 to 5 μm (Japanese Patent Application Laid-Open No. 55-49862 and Japanese Patent Application Laid-open No. 59-59 μm, 60).
962, respectively), and (3) the use of two types of M n O2 powders with average particle diameters of 50 μm and 10 μm (Japanese Patent Application Laid-open No. 57 μm, 05
(See Publication No. 963).

However, even if methods (1), (2), and (3) described above are applied to the spiral electrode of a cylindrical nonaqueous electrolyte battery, it is not possible to increase the density of the positive electrode mixture as in a coin-shaped battery. Therefore, it is not possible to expect much improvement in the reaction utilization rate of M n O2, and the peeling of the positive electrode mixture from the current collector during winding will further worsen.

The present invention solves the above-mentioned problems, has no internal short circuit, and
It is an object of the present invention to provide a spiral electrode for a cylindrical non-aqueous electrolyte battery that has a high reaction utilization rate of MnO2, which is a positive electrode active material, and therefore has a large discharge capacity.

[Structure of the Invention] (Means for Solving the Problems) As a result of extensive research to achieve the above object, the present inventors have found that graphite powder, which is a conductive agent, has two different average particle sizes.
It was discovered that by using different types of graphite powder and M n O2 powder with a larger average particle size than the graphite powder, the reaction utilization rate of M n O2 was improved and the flaking of the positive electrode mixture was also suppressed. I was able to complete it.

That is, the spiral electrode of the cylindrical non-aqueous electrolyte battery of the present invention is a positive electrode in which a positive electrode mixture consisting of manganese dioxide powder as a positive electrode active material, graphite powder as a conductive agent, and a binder is supported on a current collector. In a spiral electrode of a cylindrical non-aqueous electrolyte battery formed by winding a laminated sheet of; a negative electrode having a light metal as the negative electrode active material; a separator interposed between the positive electrode and the negative electrode, the graphite powder has an average particle size. Consisting of two types of graphite powders with different diameters, the average particle size of one graphite powder (A) is larger than the average particle size of the other graphite powder (B), and smaller than the average particle size of the manganese dioxide powder. It is characterized by

The spiral electrode of the cylindrical non-aqueous electrolyte battery of the present invention is based on the fact that the average particle size of the MnO2 powder, which is the positive electrode active material, and the two types of graphite powder, which is the conductive agent, constituting the positive electrode mixture is defined. Other elements are the same as those of the conventional battery shown in FIG.

The M n O2 powder which is the positive electrode active material according to the present invention is
The average particle size is preferably in the range of 15-40. When the average particle size exceeds 40fi1M, Mn
Since the electrochemical reaction does not proceed to the inside of O2, the reaction utilization rate becomes low, and therefore the discharge capacity becomes small.

This is because if the number of units is less than 15, the reaction utilization rate cannot be increased any further, the mechanical strength of the positive electrode mixture tends to decrease, and furthermore, the cost during production of fine powder increases. More preferably, it is 20 to 35 units.

As the graphite powder, two types of graphite powder having different average particle sizes are used in order to increase the reaction utilization rate of the MnO2 powder. The graphite powder (B) having a small average particle size forms an electrochemical reaction site on the surface of the MnO2 powder by being present on the surface of the MnO□ grain powder. On the other hand, the graphite powder (A) with a large average particle size exists between the M n 02 powders holding the graphite powder (B) with a small average particle size on the surface to form a conductive path. Therefore, together with the formation of a large number of reaction sites, the electrical conductivity of the entire positive electrode increases, and as a result, the reaction utilization rate of M n O2 can be increased.

The average particle size of the graphite powder (B) with a small average particle size is 0.1~
A range of 2 μm is preferable, and if the average particle size exceeds 2 μm, M
As the number of graphite powders present on the n 02 surface decreases, the number of electrochemical reaction sites on the M n 02 surface decreases, and as a result, the reaction utilization rate of M n O2 does not become very large.

This is because if the particle size is less than 0.1 μm, the particle size is too small and the mechanical strength of the positive electrode becomes low. More preferably, 0.5
~1.5μ clear.

The average particle size of graphite powder (A) with a large average particle size is 5 to 2J.
The range of zm is preferable; if the average particle size exceeds 20 -, the number of filled graphite powders (A) decreases, so the number of conductive paths formed decreases. Therefore, the electrical conductivity of the positive electrode decreases, and as a result, the reaction utilization rate of M n O2 cannot be increased. In addition, the mechanical strength of the positive electrode is also reduced.Even if the number of particles is less than 5, the particle size becomes small, so the mechanical strength of the positive electrode is reduced.More preferably, the number is 6 to 10.

Graphite powder (A) and graphite powder (B) according to the present invention are:
By using @-shaped graphite powder, which is preferably ring-shaped graphite powder, flexibility can be imparted to the entire positive electrode, so that the positive electrode mixture does not peel off from the current collector when it is spirally wound. is suppressed. In addition, annular graphite powder with a large particle size retains MnO2 powder, so MnO2 powder is retained during discharge.
Even when n O2 expands, the graphite does not separate from each other, so the electrical conductivity of the entire positive electrode does not decrease, and as a result, the reaction utilization rate of M n O2 can be increased.

As the binder according to the present invention, polytetrafluoroethylene, polyacrylic acid, styrene-butadiene rubbertex, methyl cellulose, carboxymethyl cellulose, etc. can be used, and polytetrafluoroethylene and polyacrylic acid are particularly preferred. be.

In the positive electrode mixture according to the present invention, the blending ratio of M n O2 powder, graphite powder (A), graphite powder (B), and binder is such that M n O2 powder is 85 to 95 parts by weight, graphite powder (A) is
) is 2 to 12 parts by weight, graphite powder (B) is 3 to 10 parts by weight, and the binder is 3 parts by weight or less per 100 parts by weight of MnO2 powder, graphite powder (A), and graphite powder (B). It is preferable that

If the amount of M n O2 powder is less than 85 parts by weight, the amount of active material in the obtained positive electrode mixture will be reduced, which will reduce the discharge capacity of the battery, which is undesirable.On the contrary, if it exceeds 95 parts by weight, Since the blending ratio of graphite powder, binder, etc. is reduced, the reaction utilization rate of M n 02 is reduced, and above all, the mechanical strength of the positive electrode mixture is reduced, resulting in a peeling phenomenon during winding. occurs frequently.

More preferably, it is 87 to 92 parts by weight.

On the other hand, when the graphite powder (A) is less than 2 parts by weight, M n
02 powder cannot be held sufficiently, the formation of conductive paths becomes insufficient, and at the same time, the mechanical strength of the entire positive electrode mixture decreases,
If it exceeds 12 parts by weight, the reaction utilization rate of MnO□ cannot be increased any further, and the mechanical strength of the entire positive electrode mixture decreases. More preferably, it is 4 to 9 parts by weight. Moreover, when the graphite powder (B) is less than 3 parts by weight, the amount that adheres to the surface of the M n O2 powder is reduced. In other words, since the number of electrochemical reaction sites is reduced, M
It becomes insufficient to increase the reaction utilization rate of n O2, and 1
If it exceeds 0 parts by weight, the reaction utilization rate of MnO2 cannot be increased any further, and the amount of graphite powder with a fine particle size increases, resulting in a decrease in the mechanical strength of the entire positive electrode mixture. This is because it will be put away. More preferably, it is 4 to 9 parts by weight.

Furthermore, if the blending ratio of the binder exceeds 3 parts by weight per 100 parts by weight of M n 02 powder, graphite powder (A), and graphite powder (B), the binder may not be present in the positive electrode mixture. Moreover, since the binder itself is an electrical insulator, the contact between M n 02 and the conductive agent becomes poor, and the utilization rate of M n 02 decreases. More preferably, it is 1.5 to 3 parts by weight.

Next, the positive electrode according to the present invention can be manufactured, for example, as follows. First, M with a predetermined average particle size
n A predetermined amount of a binder is mixed with a predetermined amount of O2 powder, graphite powder (A), and graphite powder (B) and then kneaded. Next, the obtained positive electrode mixture is applied to a current collector and dried, and further For example, it may be rolled into a sheet.

(Example) Example M n O2 powder with an average particle size of 25 units and an average particle size of 10μ
A graphite powder obtained by mixing annular graphite powder (A) with an average particle size of m and a scale graphite powder (B) with an average particle size of 1:1 (weight ratio) within the range shown in Figures 2 and 3. Further, 3 parts by weight of polytetrafluoroethylene was mixed with 100 parts by weight of M n O2 powder, scaly graphite powder (A), and scaly graphite powder (B), and then kneaded. The obtained positive electrode mixture was applied to a current collector, dried, and then roll-formed to a length of 26 mm.
A long positive electrode mixture sheet with a width of 230 mm and a thickness of 0.5 cm was prepared. Next, a sheet of metallic lithium was prepared as a negative electrode, and a nonwoven fabric made of polypropylene was prepared as a separator, and the sheets were wound together with the above-mentioned positive electrode mixture sheet. It was made into a spiral electrode.

During this winding, the presence or absence of a peeling phenomenon of the positive electrode mixture sheet from the current collector was observed, and the results are shown in FIG. Furthermore, height 3
After placing an insulating plate made of polypropylene inside a cylindrical negative electrode can made of a nickel-plated iron can with a diameter of 3 mm, an outer diameter of 16 mm, and an inner diameter of 15.5 mm, a 0-order propylene carbonate plate with a spiral electrode inserted therein and 1 After injecting a non-aqueous electrolyte in which lithium perchlorate was dissolved in a mixed solvent with ,2-dimethoxyethane to a concentration of 1 mol/state,
An insulating plate was placed on the spiral electrode, and a sealing plate made of SUS 304 with an insulating ring arranged around the outer periphery was placed on top of the insulating plate, followed by sealing.

Using this battery, constant resistance discharge was performed at 20° C. with an external resistance of 20Ω, and the discharge capacity was measured.

The discharge capacity was calculated using 90 parts by weight of M n 02 powder with an average particle size of 25, 10 parts by weight of scaly graphite powder with an average particle size of 10, and polytetrafluoroethylene (PTFE).
A battery with the same structure as the above battery was manufactured, except that a positive electrode mixture containing 3 parts by weight of n02 powder and 100 parts by weight of scaly graphite powder was used, and the discharge capacity of this battery was used as the standard. This is shown in Figure 3.

Comparative Example 1 An electrode and a battery were manufactured and evaluated in the same manner as in the example except that only scaly graphite powder with an average particle size of 10 μm was used as the conductive agent. The results are shown in Figures 2 and 3.

Comparative Example 2 An electrode and a battery were manufactured and evaluated in the same manner as in the example except that only scaly graphite powder with an average particle size of 1- was used as the conductive agent.

The results are shown in Figures 2 and 3.

[Effects of the Invention] As is clear from the above description, when the spiral electrode of the cylindrical non-aqueous electrolyte battery of the present invention is used, the resulting battery has no internal short circuit and the positive electrode active material M n O2 The reaction utilization rate becomes higher and therefore the discharge capacity becomes larger. Therefore, its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway longitudinal cross-sectional view of a cylindrical lithium manganese dioxide battery, which is an example of a cylindrical non-aqueous electrolyte battery using a spiral electrode according to the present invention, and FIG. Figure 3 is a diagram showing the rate of separation of the positive electrode mixture from the current collector when the positive electrode of a cylindrical non-aqueous electrolyte battery is spirally wound.
FIG. 2 is a diagram showing the discharge capacity of a cylindrical nonaqueous electrolyte battery according to the present invention together with a comparative example. 1...Positive electrode 2...Negative electrode 3.
... Separator 4 ... Negative electrode can 5 ...
...Positive electrode current collector rod 6.6' ...Insulation plate 7
・・・・・・Sealing plate 8・・・・・・Insulation ring 4Electric agent compounding official II meeting Figure 2 Figure 3

Claims (4)

[Claims] (1) A positive electrode in which a positive electrode mixture consisting of manganese dioxide powder as a positive electrode active material, graphite powder as a conductive agent, and a binder is supported on a current collector; A negative electrode in which a light metal is used as a negative electrode active material; Between the positive and negative electrodes In a spiral electrode of a cylindrical non-aqueous electrolyte battery formed by winding a laminated sheet with a separator interposed between A spiral electrode for a cylindrical non-aqueous electrolyte battery, characterized in that the average particle size of (A) is larger than the average particle size of the other graphite powder (B) and smaller than the average particle size of the manganese dioxide powder. (2) The average particle size of the manganese dioxide powder is 15 to 40μ
m, the average particle size of the graphite powder (A) is 5 to 20 μm, and the average particle size of the graphite powder (B) is 0.1 to 2 μm. The spiral electrode of a battery. (3) The mixing ratio of the positive electrode mixture is 85 to 95 parts by weight of the manganese dioxide powder, 2 to 12 parts by weight of the graphite powder (A),
3 to 10 parts by weight of the graphite powder (B), and the binder contains the manganese dioxide powder, the graphite powder (A), and the graphite powder (B).
) The spiral electrode for a cylindrical non-aqueous electrolyte battery according to claim 1, wherein the amount is 3 parts by weight or less per 100 parts by weight. (4) The cylindrical non-aqueous electrolyte battery according to any one of claims 1 to 3, wherein the graphite powder (A) and the graphite powder (B) are flaky graphite powders, respectively. Spiral electrode.