JP6431724B2 - Non-aqueous organic electrolyte for lithium primary battery and lithium primary battery - Google Patents

Description

  The present invention relates to a non-aqueous organic electrolyte for a lithium primary battery, and a lithium primary battery. Specifically, improved technology for non-aqueous organic electrolyte constituting a lithium primary battery using manganese dioxide as a positive electrode active material and lithium metal or lithium alloy as a negative electrode active material, and a lithium primary battery provided with an improved electrolyte solution About.

  A lithium primary battery having a negative electrode containing a negative electrode active material made of lithium metal or a lithium alloy has a positive electrode and a negative electrode arranged together with a non-aqueous organic electrolyte in a sealed battery can. Become. Lithium primary batteries, especially those using manganese dioxide as the positive electrode active material, have a high energy density and can be discharged over a long period of time, and maintain a substantially constant output voltage until the end of discharge. . Therefore, it is widely used as a power source for devices that continue to operate in a maintenance-free state for a long time, such as fire and gas leak alarms, stationary gas meters, and water meters. The lithium primary battery also has a characteristic that the internal resistance does not increase greatly even when stored for a long period of time without being used, and the discharge performance is hardly deteriorated.

  In connection with the present invention, for example, the following Patent Document 1 describes in detail the types of solvents and supporting salts used in the non-aqueous organic electrolyte solution of a lithium primary battery. Patent Document 2 below describes additives to be added to the non-aqueous organic electrolyte solution. Non-Patent Document 1 describes various lithium primary batteries having different structures and appearances.

International Publication No. 2013/065290 JP 2007-258103 A

FDK Corporation, “Lithium Battery”, [online], [Search August 4, 2014], Internet <URL: http://www.fdk.co.jp/battery/lithium/index.html>

  Lithium primary batteries have a problem that the internal resistance increases and the output voltage value itself decreases when used in a low temperature environment such as below freezing point. For this reason, if devices such as fire alarms and gas leak alarms powered by lithium primary batteries are installed in extremely cold regions or cold storage facilities, voltage values for operating these devices cannot be secured. In an emergency, those devices may not work. Therefore, it is difficult to use a lithium primary battery in a low temperature environment. Although it is conceivable to use a battery other than the lithium primary battery, a fire alarm or the like is a device that continues to operate in a maintenance-free state for a long period of time. In other batteries, the voltage gradually drops as the battery discharges. It's hard to use because it goes. Therefore, a lithium primary battery that is unlikely to drop voltage even in a low temperature environment is required. Of course, it is also important that other characteristics of the lithium primary battery are not deteriorated by suppressing the voltage drop in a low temperature environment. In general, when characteristics in a low temperature environment are improved, characteristics in a high temperature environment, for example, storage characteristics in a high temperature environment, which are at the opposite electrode, are likely to deteriorate.

  Therefore, the present invention provides a non-aqueous organic electrolytic solution capable of suppressing a voltage drop in a low temperature environment while maintaining the storage characteristics of the lithium primary battery in a high temperature environment, and a lithium primary battery including the electrolyte. The purpose is that.

The present invention for achieving the above object is a non-aqueous organic electrolyte for a lithium primary battery using manganese dioxide as a positive electrode active material and lithium metal or a lithium alloy as a negative electrode active material, comprising an organic solvent and a supporting salt. 1 or more organic compounds selected from dimethyl glutarate and diethyl pimelate, which are dicarboxylic acid esters having a chain structure, are added as additives to the basic electrolyte solution. A water-based organic electrolyte is used. More preferably, the additive is added in an amount of 0.001 wt% to 5.0 wt% with respect to the basic electrolyte.

  The present invention also extends to a lithium primary battery using manganese dioxide as a positive electrode active material and lithium metal or a lithium alloy as a negative electrode active material, and the lithium primary battery is a non-lithium primary battery according to any one of the above. It features an aqueous organic electrolyte.

  According to the non-aqueous organic electrolytic solution of the present invention, it is possible to provide a lithium primary battery that has the same storage characteristics under a high temperature environment as that of the prior art, and that does not easily drop the voltage even under a low temperature environment.

It is a figure which shows the structure of a spiral type lithium primary battery. It is a figure which shows the voltage drop rate when the spiral type lithium primary battery using the various non-aqueous organic electrolyte solution from which the kind and addition amount of an additive differ is set | placed in -40 degreeC environment. Spiral type lithium primary batteries using various non-aqueous organic electrolytes with different types and amounts of additives were discharged at 80% of the design capacity and the internal resistance when placed in an environment of 80 ° C. It is a figure which shows a change.

=== The process of conceiving the present invention ===
A lithium primary battery using a nonaqueous organic electrolyte solution according to an embodiment of the present invention uses a mixture prepared by kneading a powdered positive electrode active material together with a conductive material and a binder in a positive electrode, and lithium in a negative electrode. A metal or a lithium alloy (generally referred to as “negative electrode lithium” for convenience) itself is used. In this type of lithium primary battery, the positive electrode active material is in the form of powder, whereas the negative electrode lithium itself, which is the negative electrode active material, has a relatively small surface area relative to the positive electrode active material.

  Here, the present inventor considered the cause of the problem that the voltage of the lithium primary battery drops in a low temperature environment, and the negative electrode lithium has a smaller surface area than the positive electrode active material, so that the slight amount generated during discharge and storage is small. It was thought that the influence of the by-product was easily exerted on the whole negative electrode, and that the influence increased the resistance of the negative electrode itself, and thus increased the internal resistance of the battery, and became apparent as a voltage drop in a low temperature environment. And I thought that the voltage drop in a low-temperature environment could be effectively suppressed by forming an ion conductive film that inhibits the formation and adhesion of by-products on the surface of the negative electrode active material. . More specifically, it was thought that the non-aqueous organic electrolyte solution (hereinafter also referred to as electrolyte solution) in contact with the negative electrode lithium may be modified to impart the above-described properties for forming the coating film.

  Of course, if the ionic conductivity of the electrolytic solution itself is greatly deteriorated by modifying the electrolytic solution, or if the storage characteristics in a high temperature environment are deteriorated instead of suppressing the voltage drop at a low temperature, the tipping is over. It is also an important condition that the modified electrolyte can be manufactured stably without increasing the cost. If the above conditions are taken into consideration, the electrolyte solution is modified by adding the above-mentioned substances (additives) that are the origin of the coating to the electrolyte solution for general or typical conventional lithium primary batteries. It is realistic to do. The present invention has been conceived as a result of intensive research while verifying various experimental results obtained in the course of the above discussion and research and development.

=== Example ===

<Additives>
As described in Patent Document 2, a wide variety of organic compounds exist in the additive of the electrolytic solution. And as a result of examining the optimal additive for suppressing the voltage drop in a low temperature environment, while this inventor maintained the storage characteristic in the high temperature environment in a lithium primary battery, it describes also in patent document 2 Attention was paid to organic compounds belonging to dicarboxylic acid esters that were not present. Therefore, in order to evaluate the electrolytic solution according to the example of the present invention, various organic compounds belonging to dicarboxylic acid esters were used as additives, and various types of electrolytic agents were added to general electrolytic solutions by changing the types and amounts of the additives. The liquid was prepared. Then, lithium primary batteries using various electrolytic solutions were produced as samples, and the discharge characteristics under low temperature environment and the storage characteristics under high temperature environment in each sample were examined.

<Sample>
FIG. 1 shows a schematic structure of a lithium primary battery 1 manufactured as a sample. The illustrated lithium primary battery 1 is a spiral lithium primary battery (hereinafter also referred to as battery 1). The produced battery 1 has a cylindrical shape with an outer diameter of 17 mm and a height of 45 mm, and FIG. 1 shows a longitudinal sectional view of the battery 1 when the extending direction of the cylindrical shaft 50 is the vertical (vertical) direction. In the battery 1, a positive electrode 3, a negative electrode 4, a separator 5, and an electrolytic solution 20 are housed as power generation elements in a bottomed cylindrical metal battery can (hereinafter also referred to as a battery can 2) serving as a negative electrode can. In addition, the battery can 2 has a basic structure in which the opening of the battery can 2 is sealed by a sealing body 10 including a sealing plate 6, a positive electrode terminal 7, a metal washer 8, and a sealing gasket 9.

  The positive electrode 3 is obtained by cutting a slurry-like positive electrode material applied to a stainless lath plate into a predetermined size and then drying it. Here, as a positive electrode material, electrolytic manganese dioxide (EMD) serving as a positive electrode active material and graphite serving as a conductive material together with a binder (fluorine binder, etc.) and a predetermined ratio (for example, EMD: graphite: binder = 93 wt%: 3 wt%: 4 wt%) can be used. The positive electrode material is made into a slurry form with pure water and applied to a stainless steel lath plate. The negative electrode 4 is a plate-shaped negative electrode lithium, and here, lithium metal is used. The negative electrode 4 and the positive electrode 3 are wound with the separator 5 made of a polyolefin microporous film facing each other and wound, and the positive electrode 3 and the negative electrode 4 in the wound state are inserted into the battery can 2. ing.

  The sealing plate 6 constituting the sealing body 10 has a disk shape having an opening in the center. When the opening end side of the battery can 2 is set upward, the edge of the disk is bent upward. A metal positive terminal 7 and a metal washer 8 are caulked through a resin sealing gasket 9 in the central opening of the sealing plate 6. The edge of the sealing plate 6 and the upper edge of the battery can 2 are laser welded (at the position indicated by reference numeral 30 in the figure). Further, the positive electrode 3 (the lath plate thereof) and the lower surface of the positive electrode terminal 7, and the negative electrode 4 and the two inner surfaces of the battery can are connected via lead tabs (11, 12), respectively. The sealed battery can 2 is filled with an electrolytic solution 20 having different types and amounts of additives depending on the sample.

The electrolytic solution 20 is obtained by adding a general electrolytic solution used in a lithium primary battery as a basic electrolytic solution and adding an additive to the basic electrolytic solution. Here, propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DME) are ternary non-aqueous solutions having a volume ratio of 20 vol%, 20 vol%, and 60 vol%, respectively. A basic electrolyte is used as a solvent, and lithium triflate (LiCF ₃ SO ₃ ) dissolved as a supporting salt in the solvent so as to have a concentration of 0.8 mol / l.

  The additive is a dicarboxylic acid ester of any of dimethyl glutarate, diethyl pimelate, dimethyl phthalate, and dimethyl terephthalate. Further, the additive amount is 0.001 wt%, 0.01 wt%, 0.1 wt%, 1.0 wt%, 2.5 wt%, 5.0 wt%, and 6 depending on the sample. 0.0 wt%. As a sample according to the comparative example, a battery 1 using only a basic electrolyte as an electrolyte was also produced.

<Discharge performance under low temperature environment>
First, various samples with different types and amounts of additives contained in the electrolyte solution and samples according to comparative examples were subjected to a discharge test in which a pulse discharge was performed under a low temperature environment, and the effect of suppressing the voltage drop in each sample was evaluated. . Specifically, each sample was placed under a temperature of −40 ° C. and a load was applied, and a current of 100 mA was applied for 1 second to discharge, and the voltage (closed circuit voltage V1) at this time and before the load was applied The open circuit voltage V2 was measured. Then, a voltage drop rate ΔVr (= ΔV / V2) that is a ratio between the voltage difference ΔV (= V2−V1) between the closed circuit voltage V1 and the open circuit voltage V2 and the open circuit voltage V2 was obtained.

  FIG. 2 shows the results of a discharge test under a low temperature environment. FIG. 2 shows the relationship between the amount of additive added and the voltage drop rate for various samples using the electrolytic solution to which the additive was added. The voltage drop rate ΔVr is a relative value when the voltage drop rate in the sample according to the comparative example is 100%. As shown in FIG. 2, the voltage drop rate of all samples was 100% or less. That is, it was confirmed that a voltage drop under a low temperature environment can be suppressed by adding a compound belonging to the dicarboxylic acid ester to the basic electrolyte. Moreover, even with the same dicarboxylic acid ester, dimethyl glutarate and diethyl pimelate having a chain structure had a more remarkable effect of suppressing voltage drop than dimethyl phthalate and dimethyl terephthalate having a cyclic structure. In addition, in the case of a dicarboxylic acid ester having a chain structure, the voltage drop rate ΔVr is about 5% lower than that of the comparative example and can be reduced by about 10% at the maximum even with a very small addition amount of 0.001 wt%. did it. It was confirmed that the voltage drop rate can be reduced by at least about 5% with respect to the comparative example if the addition amount is 5.0 wt% or less.

<Storage performance in high temperature environment>
From the results of the discharge test under a low temperature environment shown in FIG. 2, the sample using the electrolytic solution added at a ratio of 1.0 wt% to the basic electrolytic solution had the lowest voltage drop rate in any additive. Therefore, in order to evaluate the storage characteristics in a high temperature environment opposite to that in a low temperature environment, one of dimethyl glutarate, diethyl pimelate, dimethyl phthalate, and dimethyl terephthalate is 1. Four types of samples were prepared using four types of electrolytes added with 0 wt%. And the preservation | save characteristic in a high temperature environment was evaluated with respect to the said 4 types of sample and the sample concerning a comparative example.

  Specifically, a 200Ω load is applied to each sample and pre-discharged until the remaining capacity reaches 20% of the design capacity (discharge depth 80%), and the end-of-discharge state where the storage characteristics under the high temperature environment are most likely to deteriorate. Was reproduced. Then, a storage test was performed in which the sample after discharge was stored in an environment at 80 ° C., and the relationship between the storage days and the internal resistance was examined.

  FIG. 3 shows the results of the storage test. In FIG. 3, the internal resistance at the start of storage is 100%. As shown in FIG. 3, the internal resistance of the sample to which the additive was added and the sample according to the comparative example changed in a similar manner. That is, the storage characteristics under a high temperature environment were not deteriorated by adding the additive.

<Performance evaluation>
In order to suppress the voltage drop in the low temperature environment, the voltage in the low temperature environment is maintained while maintaining the storage characteristics in the high temperature environment by adding a dicarboxylic acid ester having a chain structure to the basic electrolyte. It was confirmed that the descent could be suppressed. If the addition amount of the dicarboxylic acid ester having a chain structure is 5.0 wt% or less with respect to the basic electrolyte, the effect of suppressing the voltage drop becomes more remarkable.

  In addition, it can be considered that the above effect is due to the fact that the dicarboxylic acid ester is more easily reduced and decomposed than the basic electrolytic solution, and that a film is formed at the interface of the negative electrode lithium by the decomposed dicarboxylic acid ester. And the film formed of the dicarboxylic acid ester having a chain structure is excellent in ionic conductivity, and it is considered that the ionic conductivity is sufficiently maintained even in a low temperature environment and the voltage drop is suppressed. Of course, the coating on the negative electrode lithium interface can inhibit manganese eluted from the positive electrode during the power generation reaction from being reduced by the negative electrode lithium and deposited as metallic manganese, resulting in storage of the battery for an extremely long period of time. In particular, it can be expected to contribute to the effect of suppressing the increase in internal resistance when stored in the final discharge state.

  By the way, when improving the performance of the battery by adding an additive to the electrolyte, especially when both the performance in the opposite environment such as low temperature and high temperature is achieved, the characteristics in each environment are individually improved. In general, a plurality of types of additives are added to the electrolytic solution. On the other hand, in the electrolyte solution according to the above example, only one type of ester called a dicarboxylic acid ester having a chain structure is added, and any one of dimethyl glutarate and diethyl pimelate belonging to the ester is added. Only organic compounds were added. Therefore, in the above-described embodiment, even when the electrolyte solution is prepared according to the application, use environment, or target battery performance, the preparation work becomes extremely easy and the manufacturing cost can be reduced. Since one kind of organic compound is used as an additive, raw material costs can be reduced.

=== Other Embodiments ===
The present invention is characterized in that a dicarboxylic acid ester having a chain structure is added to various lithium primary electrolytes that are generally used. Therefore, the battery to which the electrolytic solution according to the present invention is applied is not limited to a spiral type, and may be a known inside-out type (also referred to as a bobbin type) or a coin type. Of course, a laminate type in which the power generation element is housed in the exterior of the laminate film may be used.

  As for dicarboxylic acid ester, which is an additive, a clear difference was observed in the voltage drop suppression effect in a low-temperature environment between the cyclic structure and the chain structure. Therefore, the chain is not limited to dimethyl glutarate and diethyl pimelate. Any organic compound belonging to a dicarboxylic acid ester having a structure is considered. Of course, the organic compound added as an additive to the basic electrolyte may not be one kind. Two or more organic compounds belonging to a dicarboxylic acid ester having a chain structure may be added.

For the basic electrolyte, for example, the ratio of the above three components (DME, PC, EC) in the solvent may be different. Of course, it does not have to be a three-component system. As the component, any electrolyte solution generally used in lithium primary batteries, such as butylene carbonate (BC), dioxolane (DOXL), gamma-butyllactone (γ-BL), tetrahydrofuran (THF), etc. It may be a thing. The same applies to the supporting salt. For example, LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₃ ) is not limited to LiCF ₃ SO ₃ used in the above examples. ₂ ), lithium salts of fluorine-containing acid imides such as (C ₄ F ₉ SO ₂ ), lithium salts of fluorine-containing acids such as LiPF ₆ and LiBF _4, and fluorine-containing acid methides such as LiC (CF ₃ SO ₂ ) ₃ Lithium salts and lithium salts of chlorine-containing acids such as LiClO ₄ can be used.

1 spiral lithium primary battery, 2 battery can, 3 positive electrode, 4 negative electrode,
5 Separator, 6 Sealing plate, 7 Positive terminal, 8 Washer, 9 Sealing gasket,
10 sealing body, 20 non-aqueous organic electrolyte,

Claims (3)

A non-aqueous organic electrolyte for lithium primary batteries using manganese dioxide as the positive electrode active material and lithium metal or lithium alloy as the negative electrode active material, in the form of a chain as an additive to the basic electrolyte consisting of an organic solvent and a supporting salt A non-aqueous organic electrolyte for a lithium primary battery, wherein one or more organic compounds selected from dimethyl glutarate and diethyl pimelate, which are dicarboxylic acid esters having a structure, are added .   The non-aqueous organic electrolyte for a lithium primary battery according to claim 1, wherein the additive is added in an amount of 0.001 wt% or more and 5.0 wt% or less with respect to the basic electrolyte. A lithium primary battery using manganese dioxide as a positive electrode active material and lithium metal or a lithium alloy as a negative electrode active material, wherein the nonaqueous organic electrolyte for a lithium primary battery according to claim 1 or 2 is provided. Lithium primary battery.

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