JP2010251288A - Nonaqueous electrolyte primary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte primary battery capable of tremendously decreasing increase in inner resistance during storage while suppressing drop in high rate discharge characteristics. <P>SOLUTION: In the nonaqueous electrolyte primary battery including a positive electrode 1 using manganese dioxide as a main active material, a negative electrode 2 containing lithium or a lithium alloy, and a nonaqueous electrolyte containing a solvent and an electrolyte salt, 2-vinyl pyridine is contained in the nonaqueous electrolyte. The ratio of 2-vinyl pyridine to the total amount of the solvent is 0.01-1.5 volume%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte primary battery, and more particularly to a non-aqueous electrolyte primary battery that can improve storage characteristics.

  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, as described above, in the nonaqueous electrolyte primary battery 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 lithium as the negative electrode material. Deposit on the metal. For this reason, there has been a problem that the internal resistance after storage increases and discharge becomes impossible. This problem is particularly prominent when exposed to a 40 ° C. to 80 ° C. environment during discharge.
Therefore, proposals have been made to improve the storage characteristics by adding boron to manganese dioxide, which is a positive electrode active material. (See Patent Document 1 below)

JP 2007-134270 A

  However, in the proposal disclosed in Patent Document 1, since the entire surface of manganese dioxide cannot be covered with boron oxide, elution of manganese ions cannot be sufficiently suppressed. On the other hand, when the surface of manganese dioxide is uniformly or thickly coated with boron oxide, the battery reaction is remarkably inhibited, and there is a problem that particularly high load characteristics are lowered.

  Therefore, an object of the present invention is to provide a non-aqueous electrolyte primary battery that can drastically reduce an increase in internal resistance during storage while suppressing a decrease in high load characteristics.

  In order to achieve the above object, the present invention provides a non-aqueous solution comprising a positive electrode containing manganese dioxide as a main active material, a negative electrode containing lithium or a lithium alloy, and a non-aqueous electrolyte solution containing a solvent and an electrolyte salt. In the electrolyte primary battery, the non-aqueous electrolyte contains vinyl pyridine.

  In batteries using a positive electrode with manganese dioxide as the main active material, manganese ions are dissolved from the manganese dioxide in the electrolyte during storage, and the dissolved manganese ions are deposited on the lithium negative electrode, increasing the internal resistance of the battery. By doing so, the battery characteristics deteriorate. Therefore, as a result of various investigations on methods for suppressing the dissolution of manganese dioxide, the nonaqueous electrolyte primary battery in which vinylpyridine is added to the nonaqueous electrolyte solution has storage characteristics compared to the battery in which vinylpyridine is not added to the nonaqueous electrolyte solution. Has been found to be greatly improved. This improvement in storage characteristics is considered to be due to the fact that after the added vinylpyridine is decomposed on the lithium negative electrode, the decomposition product forms a film on the positive electrode.

  Specifically, when vinylpyridine is added to the nonaqueous electrolyte, first, a decomposition reaction occurs in which the vinyl group of vinylpyridine is cleaved on the negative electrode surface containing lithium, and the decomposition product remains in the nonaqueous electrolyte. However, when this decomposition product reaches the positive electrode, it reacts on the surface of manganese dioxide, and a high-quality film is formed on the positive electrode. That is, in the present invention, a good-quality film is specifically produced on the positive electrode, and it improves the storage characteristics by functioning stably. The decomposition product of vinylpyridine and manganese dioxide produced on the negative electrode containing lithium It can be seen that this is caused by a combination of a specific voltage band and oxidizing power.

As described above, the electrolytic solution in contact with the entire surface of manganese dioxide is used, and thereby a film is formed on the surface of the positive electrode, thereby suppressing manganese ions from eluting into the electrolytic solution (additives such as boron oxide are added). Since the manganese dioxide surface is physically and uniformly or thickly coated, the elution of manganese ions is not suppressed), so that the battery reaction can be prevented from being significantly inhibited. Further, when vinylpyridine reacts with lithium, it does not cause problems such as gas generation due to decomposition of vinylpyridine and corrosion of lithium.
For these reasons, in the non-aqueous electrolyte primary battery having the above-described configuration, it is possible to drastically reduce an increase in internal resistance during storage while suppressing a decrease in high load characteristics.

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 pyridine is desirably 2-vinyl pyridine, and the ratio of the vinyl pyridine to the total amount of the solvent is desirably regulated to 0.01 volume% or more and 1.5 volume% or less.
If the ratio of vinylpyridine to the total amount of the solvent is less than 0.01% by volume, the proportion of vinylpyridine is too small to sufficiently improve the storage characteristics. On the other hand, the ratio of vinylpyridine to the total amount of the solvent If the amount exceeds 1.5% by volume, the resulting coating becomes too thick, causing a voltage drop during high load discharge or low temperature discharge, which may reduce the discharge capacity. Furthermore, since vinylpyridine is expensive, increasing the amount of addition causes an increase in battery cost. Therefore, if the addition amount of vinylpyridine is regulated within the above range, the maximum effect can be obtained with the minimum necessary amount (low cost).

The non-aqueous electrolyte preferably contains vinylene carbonate.
As described above, even if a coating film is formed on the positive electrode by adding vinylpyridine to the non-aqueous electrolyte, manganese may be eluted from the positive electrode to some extent during battery storage. For this reason, when sufficient film formation is not performed on the negative electrode, the eluted manganese is reduced and deposited on the negative electrode, and as a result, the electrolytic solution is decomposed, thereby increasing the internal resistance of the battery. is there.
Therefore, if vinylene carbonate is added to the non-aqueous electrolyte as in the above configuration, a film mainly composed of the decomposition products of vinylene carbonate is formed on the negative electrode. For example, when the battery is stored, some manganese is eluted from the positive electrode. Even so, it is possible to suppress decomposition of the electrolytic solution due to reduction and precipitation of the eluted manganese on the negative electrode.

In addition, a film mainly composed of a decomposition product of vinylpyridine is formed in the positive electrode, and a decomposition product of vinylene carbonate is taken into this film. If it is such a structure, although a reason is not certain, it will become a high quality film excellent in lithium ion conductivity.
On the other hand, in the negative electrode, a film mainly composed of a decomposition product of vinylene carbonate is formed, and a decomposition product of vinylpyridine is taken into this film. If it is such a structure, although a reason is not certain, it will become a high quality film excellent in lithium ion conductivity.

As described above, a good quality film is formed in both positive and negative electrodes. As a result, an effect of drastically suppressing an increase in the internal resistance of the battery during battery storage while maintaining excellent low-temperature discharge characteristics can be obtained.
In addition, the effect of the film formation on the negative electrode is the effect of adding cyclic carbonate having a highly reactive substituent such as fluoroethylene carbonate to the non-aqueous electrolyte in addition to the addition of vinylene carbonate to the non-aqueous electrolyte. Even so, it is thought that it can be demonstrated.

It is desirable that the ratio of the vinylene carbonate with respect to the total amount of the solvent is regulated to 0.1 volume% or more and 2.0 volume% or less.
When the addition amount of vinylene carbonate is less than 0.1% by volume, the effect of addition cannot be sufficiently obtained. On the other hand, when the addition amount exceeds 2.0% by volume, the resulting coating becomes too thick, and during discharge. A voltage drop may occur remarkably (particularly during low temperature discharge such as 0 to -20 ° C.), and the discharge capacity may be reduced. Furthermore, since vinylene carbonate is expensive, an increase in the amount added causes an increase in the cost of the battery. Therefore, if the addition amount of vinylene carbonate is regulated within the above range, the maximum effect can be obtained with the minimum necessary amount (low cost).

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

It is desirable that the ratio of boron oxide to the total amount of boron oxide and manganese dioxide is regulated to 0.1% by mass or more and 1.0% by mass or less.
When the proportion of boron oxide is less than 0.1% by mass, the sufficient addition effect cannot be obtained. On the other hand, when the addition amount exceeds 1.0% by mass, the resulting coating becomes too thick, so that the discharge capacity is reduced. This is because it decreases.

  According to the present invention, there is an excellent effect that an increase in internal resistance during storage can be drastically reduced while suppressing a decrease in high load characteristics.

It is sectional drawing of the test battery which concerns on the form for implementing this invention. It is a graph which shows the relationship between 2-VP (2-vinyl pyridine) addition amount and the resistance value after a 45-day preservation | save.

  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 ratio of the amount of boron to the total amount of boron oxide (B ₂ O ₃ ) and manganese dioxide is 0.5% by mass is heat-treated in air at 375 ° C. for 20 hours. (Baking) and pulverization gave boron-containing manganese dioxide as a positive electrode active material.
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 alloy (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 2-vinylpyridine (hereinafter sometimes referred to as 2-VP) as an additive was added to the above mixed solvent in an amount of 0. A non-aqueous electrolyte was prepared by adding 1% by volume.

[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 placed in a storage space of a bottomed cylindrical negative electrode can 4 having an opening 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 poured into the negative electrode can 4 and the sealing portion was caulked to produce a cylindrical lithium primary battery (rated discharge capacity: 2500 mAh) having a diameter of 17.0 mm and a height of 45.0 mm. In FIG. 1, 8 is an insulating packing that 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, and 9 is an insulating plate that covers the lower surface of the winding electrode body 5. , 11 are PTC elements.

[First embodiment]
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)
A battery was fabricated in the same manner as in Example 1 except that the amount of 2-VP added to the mixed solvent (hereinafter simply referred to as the amount of 2-VP added) was 1.0% by volume.
The battery thus produced is hereinafter referred to as the present invention battery A2.

(Comparative example)
A battery was fabricated in the same manner as in Example 1 except that 2-VP was not added to the mixed solvent.
The battery thus produced is hereinafter referred to as comparative battery X.

(Experiment 1)
After discharging and storing the present invention batteries A1 and A2 and the comparative battery X under the following conditions, the resistance values after storage were examined by the following measurement method, and the results are shown in Table 1 and FIG. .
-Discharge conditions and storage conditions Considering that manganese elution appears more prominently at deeper discharge depths, constant current discharge was performed at a current of 3 mA for 667 hours, and then stored at 40 ° C for 45 days.
-Measuring method of resistance value after storage The impedance at 1 kHz was measured by the AC four-terminal method, and the value was used as the internal resistance.

  As is apparent from Table 1 and FIG. 2, the batteries A1 and A2 of the present invention using the non-aqueous electrolyte added with 2-VP had resistance values of 0.687Ω and 0.536Ω after 45 days storage, respectively. On the other hand, in the comparative battery X to which 2-VP is not added, the resistance value after storage for 45 days is 1.074Ω, so that the batteries A1 and A2 of the present invention are compared with the comparative battery X. It can be seen that the increase in resistance is suppressed.

  However, although not shown in Table 1, if the amount of 2-VP added is too small (specifically, less than 0.01% by volume), the internal resistance after storage may increase. Therefore, from the viewpoint of sufficiently suppressing an increase in internal resistance after storage, the amount of 2-VP added is desirably 0.01% by volume or more.

(Experiment 2)
The invention batteries A1 and A2 and the comparative battery X were discharged under the following conditions, and the discharge capacity during high load discharge was examined. Table 2 shows the results.
-Discharge condition It is the conditions that each battery immediately after battery preparation is discharged to a battery voltage of 2 V at a current value of 500 mA under a condition of 25 ° C.

  As is clear from Table 2, the discharge capacity of the comparative battery X in which 2-VP is not added to the non-aqueous electrolyte is 1379 mAh, whereas in the present invention batteries A1 and A2 to which 2-VP is added, the discharge capacity is 1379 mAh. 1384 mAh and 1348 mAh, respectively, and the discharge capacities of the three batteries are considered to be substantially the same. Therefore, it can be seen that the discharge capacity does not decrease even when 2-VP is added.

  However, as shown in FIG. 2, even if the addition amount of 2-VP is increased too much, the resistance value does not decrease, and when the addition amount of 2-VP becomes too large (specifically, 1.5 When the volume% is exceeded, the resulting coating may be too thick, causing a voltage drop during high-load discharge and reducing the discharge capacity. Therefore, from the viewpoint of suppressing a decrease in discharge capacity, the amount of 2-VP added is preferably 1.5% by volume or less.

(Experiment 3)
In order to confirm that the 2-VP decomposition product forms a film on the surface of the positive electrode active material, the following experiment was performed.
First, with respect to the battery A1 of the present invention, a part of the negative electrode can was cut, and the battery A1 of the present invention was immersed in a beaker filled with an electrolytic solution having the same composition as the electrolytic solution used in the battery A1 of the present invention. did. Next, after immersing lithium metal in the same beaker, current was passed through the positive and negative electrode cans of the present invention battery A1, voltage measurement was performed between the positive electrode and lithium metal, and the impedance of the positive electrode at 1 kHz was measured by the AC four-terminal method. It was measured. Furthermore, current was passed through the positive and negative electrode cans of the battery A1 of the present invention, voltage measurement was performed between the negative electrode and lithium metal, and the impedance of the negative electrode at 1 kHz was measured by the AC four-terminal method.
As a result, the ratio of the resistance component of the positive electrode and the negative electrode of the present battery A1 was 69:31.

Further, the ratio of the resistance component of the positive electrode and the resistance component of the negative electrode of the comparative battery X was also measured for the comparative battery X in the same manner as the battery A1 of the present invention, and the ratio was 41:58.
From the experimental results of the present invention battery A1 and the comparative battery X, the ratio of the impedance on the positive electrode side is increased in the present invention battery A1 to which 2-VP is added. Therefore, it was revealed that the 2-VP decomposition product is highly likely to form a film on the surface of the positive electrode active material.

[Second Embodiment]
Example 1
In the preparation of the non-aqueous electrolyte, in addition to the above-mentioned 2-VP, 0.10% by volume of vinylene carbonate (VC) was added to the above mixed solvent. A battery was produced in the same manner.
The battery thus produced is hereinafter referred to as the present invention battery B1.

(Examples 2 and 3)
A battery was fabricated in the same manner as in Example 1 except that the amount of VC added to the mixed solvent (hereinafter simply referred to as the amount of VC added) was 0.5% by volume and 1.0% by volume, respectively. did.
The batteries thus produced are hereinafter referred to as invention batteries B2 and B3, respectively.

(Examples 4 and 5)
A battery was fabricated in the same manner as in Example 1 of the first example except that the amount of 2-VP added was 0.05% by volume and 0.30% by volume, respectively.
The batteries thus produced are hereinafter referred to as invention batteries B4 and B5, respectively.

(Examples 6 and 7)
A battery was fabricated in the same manner as in Example 3 except that the addition amount of 2-VP was 0.05% by volume and 0.30% by volume, respectively.
The batteries thus produced are hereinafter referred to as present invention batteries B6 and B7, respectively.

(Comparative example)
A battery was fabricated in the same manner as in the comparative example of the first example except that 0.1% by volume of VC was added to the mixed solvent.
The battery thus produced is hereinafter referred to as comparative battery Y.

(Experiment 1)
Since the resistance values after storage in the present invention batteries A1, B1 to B7 and the comparative batteries X and Y were examined, the results are shown in Table 3. The experimental conditions and measurement method were the same as those in Example 1 of the first example except that the storage period was 50 days. The parentheses in Table 3 indicate the amount of increase in internal resistance of each battery as an index when the amount of increase in internal resistance of the comparative battery X is 100.

  As is apparent from Table 3, in the comparative battery X in which neither 2-VP nor VC is added, the increase in internal resistance is 1.64Ω. Further, in the comparative battery Y to which only 0.1% by volume of VC is added, the increase in internal resistance is 1.64Ω, which is equivalent to the comparative battery X. On the other hand, in the battery A1 of the present invention to which only 2-VP is added at 0.10 volume%, the increase in internal resistance is 0.90Ω, and the increase in internal resistance is drastically reduced compared to the comparative battery X. (The index when the comparative battery X is 100 (hereinafter simply referred to as the index) is 54.9). Furthermore, in the battery B1 of the present invention to which 0.10% by volume of 2-VP was added and 0.1% by volume of VC was added, the increase in internal resistance was 0.75Ω, which was an increase in internal resistance compared to the comparative battery X. The amount has decreased dramatically (index is 45.7). Therefore, it is indispensable to add 2-VP in order to suppress the increase in internal resistance, and it is particularly preferable to add VC in addition to 2-VP. Thus, it is more preferable to add 2-VP and VC because, when both are added, a high-quality film excellent in lithium ion conductivity is formed on the surfaces of both positive and negative electrodes. .

Further, regarding the amount of VC added, it is recognized that the amount of increase in internal resistance decreases as the amount of VC added increases (although the amount of 2-VP added is the same at 0.10% by volume). Inventive batteries A1 and B1 to B3 with different amounts of VC.
Furthermore, with respect to the addition amount of 2-VP, it is recognized that the amount of increase in internal resistance decreases as the addition amount of 2-VP increases (VC is not added, but the addition amount of 2-VP is different. The addition amounts of the present invention batteries A1, B4, B5, and VC are all the same at 1.0% by volume, but the addition amount of 2-VP is different (see the present invention batteries B3, B6, and B7).

(Experiment 2)
The invention batteries A1, B3, B6, B7 and the comparative battery X were discharged under the following conditions, and the discharge capacity at low temperature discharge was examined. The results are shown in Table 4.
-Discharge condition It is the conditions that each battery immediately after battery preparation is discharged to 0V at a current value of 300 mA to a battery voltage of 2V.

  As is apparent from Table 4 above, the discharge capacity of the present invention battery B3 added with 0.10 vol% of 2-VP is lower than that of the present invention battery B6 added with 0.05 vol% of 2-VP. Furthermore, it can be seen that the discharge capacity of the present invention battery B7 to which 0.30% by volume of 2-VP is added is lower than that of the present invention battery B3. Moreover, it is recognized that the discharge capacity of the battery A1 of the present invention to which 0.10% by volume of 2-VP is added is lower than that of the comparative battery X to which 2-VP is not added. This is considered to be due to the fact that when the amount of 2-VP added increases, the resulting coating becomes too thick.

  Moreover, it is recognized that the discharge capacity of the present invention battery B3 having 1.0% by volume VC is lower than that of the present invention battery A1 to which VC is not added. This is considered to be due to the fact that when the amount of VC added increases, the resulting coating becomes too thick.

  When the present inventors diligently studied in consideration of the results of Experiment 1 and Experiment 2 of the first embodiment and the results of Experiment 1 and Experiment 2 of the first embodiment, the amount of VC added was 0. It is desirable to regulate to 1 volume% or more and 2.0 volume% or less, especially 0.5 volume% or more and 1.0 volume% or less, and the addition amount of 2-VP is 0.01 volume% or more. It has been found that it is desirable to regulate the amount to 1.5% by volume or less, particularly 0.05% by volume or more and 0.10% by volume or less. The amount of VC or 2-VP added is regulated in consideration of the usage environment (whether the battery is used under low temperature or high load conditions, and the frequency when used). Is preferred.

  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 (7)

In a non-aqueous electrolyte primary battery comprising a positive electrode comprising manganese dioxide as a main active material, a negative electrode containing lithium or a lithium alloy, and a non-aqueous electrolyte solution containing a solvent and an electrolyte salt,
A non-aqueous electrolyte primary battery, wherein the non-aqueous electrolyte contains vinylpyridine.   The non-aqueous electrolyte primary battery according to claim 1, wherein the vinyl pyridine is 2-vinyl pyridine.   The nonaqueous electrolyte primary battery according to claim 1 or 2, wherein a ratio of the vinyl pyridine to a total amount of the solvent is regulated to 0.01 volume% or more and 1.5 volume% or less.   The nonaqueous electrolyte primary battery according to any one of claims 1 to 3, wherein the nonaqueous electrolyte contains vinylene carbonate.   The non-aqueous electrolyte primary battery according to claim 4, wherein a ratio of the vinylene carbonate to the total amount of the solvent is regulated to 0.1 volume% or more and 2.0 volume% or less.   The nonaqueous electrolyte primary battery according to any one of claims 1 to 5, wherein the manganese dioxide contains boron oxide.   The nonaqueous electrolyte primary battery according to claim 6, wherein a ratio of boron oxide to a 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.

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