JP2010232039A - Nonaqueous electrolyte primary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress rising of internal resistance during storage while keeping excellent low temperature discharge characteristics in a nonaqueous electrolyte primary battery composed of a positive electrode using manganese dioxide as the main active material, a negative electrode comprising lithium or a lithium alloy, and an electrolyte. <P>SOLUTION: In the nonaqueous electrolyte primary battery containing a positive electrode 1 using manganese dioxide as the main active material, a negative electrode 2 containing metallic lithium or a lithium alloy, and a nonaqueous electrolyte containing a solvent and an electrolyte salt, divinyl sulfone and dimethyl phthalate are added to the nonaqueous electrolyte. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improvement of an electrolyte solution in a non-aqueous electrolyte primary battery using manganese dioxide as a positive electrode active material.

  Non-aqueous electrolyte primary batteries have been used for digital cameras, memory backup power supplies, fire alarm power supplies, etc., because of their large battery capacity and excellent high-rate discharge characteristics. Along with the expansion, there has been a demand for a product with little deterioration even under severe conditions such as storage for 10 years.

Here, manganese dioxide is mainly used as the positive electrode active material of the non-aqueous electrolyte primary battery, particularly in consideration of improvement of discharge characteristics at a low temperature, and as the negative electrode active material, lithium metal or lithium alloy is used. Further, as an electrolyte, a solute such as LiClO ₄ or LiCF ₃ SO ₃ was dissolved in a mixed solvent of carbonates such as propylene carbonate and a low boiling point solvent such as 1,2-dimethoxyethane. Things are used.

  However, in non-aqueous electrolyte primary batteries using manganese dioxide as the positive electrode active material, manganese dioxide elutes into the electrolyte as manganese ions due to long-term storage, and the eluted manganese ions are deposited on the lithium metal that is the negative electrode material. For this reason, there is a problem that the internal resistance after storage rises and discharge becomes impossible. This problem is particularly prominent when exposed to an environment of 40 ° C. to 80 ° C. during discharge.

  In view of the above, a lithium battery using a non-aqueous electrolyte containing a compound having a sulfone group has been proposed. And, when such a non-aqueous electrolyte is used, the coating component produced by the decomposition of the compound having a sulfone group is stably present on lithium and the positive electrode even during storage, so that long-term storage characteristics can be improved. (See Patent Document 1 below).

  Moreover, a lithium battery using a nonaqueous electrolytic solution containing an aromatic dicarboxylic acid ester has been proposed. Further, it is described that the use of such a non-aqueous electrolyte suppresses the generation of decomposition products of low boiling point solvents on discharged manganese dioxide, and suppresses the increase in internal resistance during long-term storage at room temperature. (See Patent Document 2 below).

JP 2008-300313 A JP-A-7-22069

  However, a battery using a non-aqueous electrolyte containing only a compound having a sulfone group or a non-aqueous electrolyte containing only an aromatic dicarboxylic acid ester has a problem that a sufficient internal resistance increase suppressing effect cannot be obtained.

  In view of the above problems, the present invention maintains excellent low-temperature discharge characteristics in a non-aqueous electrolyte primary battery composed of a positive electrode mainly composed of manganese dioxide, a negative electrode made of lithium or a lithium alloy, and a non-aqueous electrolyte. The purpose is to suppress an increase in internal resistance during storage.

  In a battery using manganese dioxide as a positive electrode active material, manganese dioxide is dissolved in the electrolyte during storage, and the dissolved manganese is deposited on the lithium negative electrode. For this reason, the internal resistance of the battery increases, and the battery characteristics deteriorate. Therefore, as a result of various studies on means for suppressing an increase in internal resistance during storage, the present inventors have found that the increase in internal resistance can be achieved by using a non-aqueous electrolyte containing vinyl sulfone and aromatic dicarboxylic acid ester. It was found that it was greatly suppressed.

Therefore, the present invention provides a nonaqueous electrolyte primary battery comprising a positive electrode mainly composed of manganese dioxide, a negative electrode including metallic lithium or a lithium alloy, and a nonaqueous electrolytic solution including a solvent and an electrolyte salt. Vinylsulfone and aromatic dicarboxylic acid ester are added to the non-aqueous electrolyte.
In non-aqueous electrolyte primary batteries using non-aqueous electrolytes containing only vinyl sulfone or non-aqueous electrolytes containing only aromatic dicarboxylic acid esters, the increase in internal resistance cannot be sufficiently suppressed. On the other hand, in the nonaqueous electrolyte primary battery using the nonaqueous electrolyte solution to which vinyl sulfone and aromatic dicarboxylic acid ester are added, the increase in internal resistance can be sufficiently suppressed specifically. This is considered to be due to the following reasons.

  In the case of using a non-aqueous electrolyte to which vinyl sulfone is added, the decomposition product is oxidized and decomposed on the positive electrode after the vinyl group of vinyl sulfone is cleaved by the reducing action of the negative electrode made of lithium or lithium alloy. The decomposition product is considered to form a film on the surface of the positive electrode, and the effect of forming the film is presumed to be an action due to the polarity of the sulfonyl group of the decomposition product. Therefore, it is necessary to add vinyl sulfone having both a vinyl group and a sulfonyl group to the non-aqueous electrolyte. However, when the battery is stored, manganese eluted at the positive electrode is reduced and deposited on the negative electrode, which is accompanied by decomposition of the electrolytic solution. However, in the electrolytic solution to which only vinyl sulfone is added, sufficient film formation is formed on the negative electrode. Since it is not made, decomposition | disassembly of electrolyte solution cannot be suppressed.

  On the other hand, when a nonaqueous electrolytic solution to which an aromatic dicarboxylic acid ester is added is used, the carbonyl group reacts with the negative electrode, and a lithium conductive film is formed on the negative electrode. At this time, it is thought that a film having two carboxylic acid ester decomposition products and an aromatic ring is formed on the negative electrode, but this is a film having a very high steric hindrance, and manganese is reduced and deposited on the negative electrode. It is thought that the decomposition of the electrolytic solution at the time is suppressed. However, on the positive electrode side, it is considered that oxidative decomposition of the ether solvent occurs during storage. However, in the electrolytic solution to which only the aromatic dicarboxylic acid ester is added, a sufficient film is not formed on the positive electrode. Degradation cannot be suppressed.

On the other hand, when a nonaqueous electrolytic solution to which vinyl sulfone and aromatic dicarboxylic acid ester are added is used, a film can be formed on each of the positive and negative electrodes, so that manganese is reduced on the negative electrode. The decomposition of the electrolytic solution at the time and the oxidative decomposition of the ether solvent on the positive electrode side during storage are suppressed. Therefore, the effect of drastically suppressing the increase in the internal resistance of the battery during battery storage can be obtained.
The negative electrode only needs to contain metallic lithium or a lithium alloy. In this case, it is particularly preferable that a lithium alloy containing aluminum is included. This is because metallic lithium is extremely reactive, but a lithium alloy containing aluminum is less reactive than metallic lithium.
Moreover, the positive electrode which uses manganese dioxide as a main active material means the case where the ratio of manganese dioxide with respect to the total amount of the active material in a positive electrode is 50 mass% or more.

The vinyl sulfone is desirably divinyl sulfone.
This is because a denser film can be formed on the surface of the positive electrode by using a short divinyl sulfone having two vinyl groups and a straight chain. However, it is not limited to divinyl sulfone, and may be vinyl sulfonic acid or the like.

The aromatic dicarboxylic acid ester is preferably dimethyl phthalate or diethyl phthalate, and particularly preferably dimethyl phthalate.
This is because a dense film having a high steric hindrance can be formed by having a shorter linear carboxylic acid ester in the ortho position. However, it is not limited to dimethyl phthalate or the like, and may be dibutyl phthalate or the like.

It is desirable that the amount of divinyl sulfone added to the solvent is regulated to 0.01% by volume or more and less than 1.00% by volume, and the amount of the dimethyl phthalate or diethyl phthalate added to the solvent is It is desirable to be restricted to 0.01 volume% or more and less than 1.00 volume%.
When the addition amount of dimethyl phthalate, diethyl phthalate, or divinyl sulfone is less than 0.01% by volume, the sufficient addition effect cannot be obtained. On the other hand, when the addition amount is 1.00% by volume or more, it is generated. This is because the film to be formed becomes too thick, and a voltage drop occurs significantly during discharge (especially during discharge at a low temperature such as −20 ° C.), thereby reducing the discharge capacity.

The manganese dioxide contains boron oxide, and the ratio of boron oxide to the total amount of the boron oxide and the manganese dioxide is regulated to be 0.1% by mass or more and 1.0% by mass or less. desirable.
This is because if manganese oxide contains boron oxide, elution of manganese ions can be further suppressed. Moreover, the ratio of boron oxide is regulated as described above. If the ratio of boron oxide is less than 0.1% by mass, the sufficient addition effect cannot be obtained, while the addition amount is 1.0% by mass. This is because if the thickness exceeds the range, the resulting coating becomes too thick and the discharge capacity decreases.

As described above, when manganese dioxide contains boron oxide, vinyl pyridine is preferably added to the non-aqueous electrolyte.
The reason is not clear, but if vinylpyridine is added to the non-aqueous electrolyte, a denser film is formed on the surface of the positive electrode with boron oxide as a nucleus, and the above-described effects are further exhibited. .

  According to the present invention, in a non-aqueous electrolyte primary battery composed of a positive electrode mainly composed of manganese dioxide, a negative electrode made of lithium or a lithium alloy, and a non-aqueous electrolyte, excellent low-temperature discharge characteristics are maintained. In addition, an excellent effect is obtained in that an increase in internal resistance during storage can be suppressed.

It is sectional drawing of the nonaqueous electrolyte primary battery which concerns on the form for implementing this invention.

  Hereinafter, a nonaqueous electrolyte primary battery according to the present invention will be described with reference to FIG. In addition, the nonaqueous electrolyte primary battery in this invention is not limited to what was shown to the following form, In the range which does not change the summary, it can change suitably and can implement.

[Production of positive electrode]
First, manganese dioxide to which boron oxide is added so that the amount of boron with respect to the total amount of boron oxide (B ₂ O ₃ ) and manganese dioxide is 0.5 mass% is heat-treated in air at 375 ° C. for 20 hours ( By firing) and pulverizing, boron-containing manganese dioxide as a positive electrode active material was obtained.
Next, the boron-containing manganese dioxide powder, the carbon black powder as the conductive agent, and the fluororesin powder as the binder are mixed at a mass ratio of 85: 10: 5 to mix the positive electrode mixture. After that, this positive electrode mixture was pressure-bonded to a SUS mesh, and further dried in vacuum at 250 ° C. for 2 hours to produce a positive electrode.

(Production of negative electrode)
A lithium (Li—Al) alloy to which 0.5% by mass of aluminum was added was processed into a sheet shape to produce a negative electrode.

(Preparation of non-aqueous electrolyte)
Trifluoromethane as a supporting electrolyte salt in a mixed solvent in which ethylene carbonate (EC), butylene carbonate (BC), and 1,2-dimethoxyethane (DME) are mixed at a volume ratio of 15:15:70. 0.6 mol / liter of lithium sulfonate (LiCF ₃ SO ₃ ) was dissolved, and divinyl sulfone and dimethyl phthalate were further added as additives to the above mixed solvent in an amount of 0.1% by volume and 0.08%, respectively. % Non-aqueous electrolyte was prepared.

[Battery assembly]
First, a separator 3 made of a polyethylene microporous film is disposed between the positive electrode 1 and the negative electrode 2, and then wound into a spiral shape to produce a wound electrode body 5, as shown in FIG. In addition, the wound electrode body 5 was disposed in a storage space of a bottomed cylindrical negative electrode can 4 having an open portion at the top. Next, the negative electrode current collecting tab 6 was welded to the bottom of the negative electrode can 4, and the positive electrode current collecting tab 7 was welded to the positive electrode terminal 10. Thereby, chemical energy generated inside the battery can be taken out from both terminals of the positive electrode terminal 10 and the negative electrode can 4 as electric energy. Thereafter, an electrolytic solution was injected into the negative electrode can 4 and the sealing portion was caulked to produce a cylindrical nonaqueous electrolyte primary battery (rated discharge capacity: 2500 mAh) having a diameter of 17.0 mm and a height of 45.0 mm. In FIG. 1, 9 is an insulating plate covering the lower surface of the winding electrode body 5, and 8 is interposed between the positive electrode terminal 10 and the negative electrode can 4 to insulate the positive electrode terminal 10 from the negative electrode can 4. Insulation packing 11 is a PTC element.

Example 1
A battery was produced in the same manner as in the embodiment for carrying out the invention.
The battery thus produced is hereinafter referred to as the present invention battery A1.

(Example 2)
Except that divinyl sulfone and dimethyl phthalate were added in an amount of 0.1% by volume and 0.04% by volume, respectively, as additives for the non-aqueous electrolyte, based on the mixed solvent. A battery was produced.
The battery thus produced is hereinafter referred to as the present invention battery A2.

(Comparative Example 1)
A battery was fabricated in the same manner as in Example 1 except that divinyl sulfone and dimethyl phthalate were not added to the non-aqueous electrolyte.
The battery thus produced is hereinafter referred to as comparative battery X1.

(Comparative Example 2)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by volume of divinyl sulfone was added to the mixed solvent as an additive for the nonaqueous electrolytic solution (dimethyl phthalate was not added).
The battery thus produced is hereinafter referred to as comparative battery X2.

(Comparative Example 3)
A battery was fabricated in the same manner as in Example 1 except that 0.08% by volume of dimethyl phthalate was added as a non-aqueous electrolyte additive to the mixed solvent (no divinyl sulfone was added).
The battery thus produced is hereinafter referred to as comparative battery X3.

(Comparative Example 4)
A battery was fabricated in the same manner as in Example 1 except that 0.04% by volume of dimethyl phthalate was added to the mixed solvent as an additive for the non-aqueous electrolyte (no divinyl sulfone was added).
The battery thus produced is hereinafter referred to as comparative battery X4.

(Comparative Example 5)
A battery was prepared in the same manner as in Example 1 except that 0.1% by volume of isopropyl methyl sulfone was added to the mixed solvent as an additive for the nonaqueous electrolytic solution (dimethyl phthalate and divinyl sulfone were not added). Was made.
The battery thus produced is hereinafter referred to as comparative battery X5.

(Experiment)
The amount of increase in internal resistance of the present invention batteries A1 and A2 and the comparative batteries X1 to X5 was examined by the following method, and the results are shown in Table 1. In the experiment, for each battery immediately after fabrication, the impedance at 1 kHz was measured by the AC four-terminal method, and this was used as the internal resistance before storage. Next, considering that the elution of manganese appears more remarkably at a deep discharge depth, constant current discharge was performed at 3 mA for 667 hours, and then stored for 20 days in an 80 ° C. environment. Next, impedance was measured in the same manner as the internal resistance before storage, and this was used as the internal resistance after storage. And the internal resistance raise amount was computed by the following (1) formula.
Internal resistance increase (mΩ) = Internal resistance after storage-Internal resistance before storage (1)

  In addition, the inventive batteries A1 and A2 and the comparative batteries X1 to X5 immediately after production were discharged to 2 V at a current value of 500 mA under the condition of −20 ° C., and the discharge capacity at that time was measured. Also shown in FIG.

  As apparent from Table 1 above, the increase in internal resistance of the comparative battery X1 that does not contain both divinylsulfone and dimethyl phthalate in the non-aqueous electrolyte is 99.6 mΩ, and the following is based on this comparative battery X1. The experimental results will be described in detail.

  In Comparative Battery X2 containing only 0.1% by volume of divinylsulfone, the increase in internal resistance was 81.8 mΩ, an improvement of 17.8 mΩ compared to Comparative Battery X1, and further, only dimethyl phthalate was added to 0.08. In the comparative battery X3 containing volume%, the increase in internal resistance was 48.8 mΩ, which was an improvement of 50.8 mΩ compared to the comparative battery X1.

In contrast, in the battery A1 of the present invention containing 0.1% by volume of divinylsulfone and 0.08% by volume of dimethyl phthalate, the increase in internal resistance is 8.4 mΩ, which is 91.2 mΩ compared to the comparative battery X1. An improvement was seen. This is a significant improvement over the results expected from batteries with either divinyl sulfone or dimethyl phthalate added. Simply, the addition effect of divinyl sulfone and the addition of dimethyl phthalate It is not a sum of effects.
Specifically, the improvement effect of the comparison battery X2 and the comparison battery X3 with respect to the comparison battery X1 is 17.8 mΩ and 50.8 mΩ, respectively. Therefore, the improvement effect of the battery A1 of the present invention with respect to the comparison battery X1 is usually (17.8 mΩ + 50). .8 mΩ = 68.6 mΩ). However, in practice, the improvement effect of the battery A1 of the present invention with respect to the comparative battery X1 is 91.2 mΩ, which is clear from the fact that the improvement effect far beyond expectations is seen.

The same improvement was also observed in the present invention battery A2. This is apparent when the battery A2 of the present invention is compared with the comparative battery X2 and the comparative battery X4 in the same manner as described above.
Therefore, it can be seen that vinylsulfone and aromatic dicarboxylic acid ester need to be added to the non-aqueous electrolyte in order to reliably reduce the increase in internal resistance.

In Comparative Battery X5 containing isopropyl methyl sulfone, which is a sulfone compound containing no vinyl group, no effect of improving storage characteristics was observed. From this, it can be seen that the presence of a vinyl group is important for forming a film on the positive electrode.
The discharge capacity of the comparative batteries X2 to X4 to which either one of divinyl sulfone or dimethyl phthalate was added was 66.1 to 79.8 mAh, while that of the batteries A1 and A2 of the present invention was 66. 9 mAh and 69.8 mAh, and it is considered that there is almost no difference between the two.

  The present invention can be applied to, for example, a digital camera, a memory backup power source, a fire alarm power source, and the like.

1: Positive electrode 2: Negative electrode 3: Separator 4: Negative electrode can 5: Winding electrode body 10: Positive electrode terminal

Claims (6)

In a non-aqueous electrolyte primary battery comprising a positive electrode comprising manganese dioxide as a main active material, a negative electrode containing lithium metal or a lithium alloy, and a non-aqueous electrolyte solution containing a solvent and an electrolyte salt,
A nonaqueous electrolyte primary battery comprising vinylsulfone and an aromatic dicarboxylic acid ester added to the nonaqueous electrolyte solution.   The non-aqueous electrolyte primary battery according to claim 1, wherein the vinyl sulfone is divinyl sulfone.   The nonaqueous electrolyte primary battery according to claim 1 or 2, wherein the aromatic dicarboxylic acid ester is dimethyl phthalate or diethyl phthalate.   4. The nonaqueous electrolyte primary battery according to claim 2, wherein an amount of the divinyl sulfone added to the solvent is regulated to 0.01 volume% or more and less than 1.00 volume%.   The nonaqueous electrolyte primary battery according to claim 3 or 4, wherein an addition amount of the dimethyl phthalate or the diethyl phthalate to the solvent is regulated to 0.01 volume% or more and less than 1.00 volume%.   The manganese dioxide contains boron oxide, and the ratio of boron oxide to the total amount of the boron oxide and the manganese dioxide is regulated to 0.1% by mass or more and 1.0% by mass or less. Item 6. The nonaqueous electrolyte primary battery according to any one of Items 1 to 5.

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