JP2015022985A - Non-aqueous organic electrolyte and lithium primary battery - Google Patents

Abstract

An organic electrolyte for achieving a lithium primary battery that can be stored for a long period of time even at the end of discharge. A non-aqueous organic electrolyte solution 20 for a lithium primary battery 1 using manganese dioxide as a positive electrode active material 3 and lithium metal or a lithium alloy as a negative electrode active material 4, and including LiCF3SO3 as a supporting salt. In addition, LiB (C 2 O 4) 2 is added to form a non-aqueous organic electrolyte. Preferably, a non-aqueous organic electrolytic solution to which LiB (C 2 O 4) 2 is added at a concentration of 0.1 mol / l or more is used. It is good also as a non-aqueous organic electrolyte solution to which LiB (C2O4) 2 is added at a concentration of 0.5 mol / l or less. [Selection] Figure 1

Description

  The present invention relates to a technique for improving a non-aqueous organic electrolyte constituting a lithium primary battery.

  Lithium primary batteries use lithium metal or a lithium alloy as a negative electrode active material, and manganese dioxide or copper oxide as a positive electrode active material. A lithium primary battery has a structure in which a positive electrode material containing a positive electrode active material and a negative electrode material containing a negative electrode active material are placed in a battery can via a separator and filled with a nonaqueous organic electrolyte solution and sealed. ing.

  The non-aqueous organic electrolytic solution that is the subject of the present invention is a non-aqueous solution serving as a solvent containing a lithium salt as a supporting salt (solute). In addition, about the kind of solvent and support salt which are used for the organic electrolyte solution of a lithium primary battery, it describes in detail in the following patent document 1, for example.

  Lithium primary batteries, especially those with manganese dioxide as the positive electrode active material, have a high energy density, can be discharged over a long period of time, and have a low voltage drop until the end of discharge. It is widely used in applications that continue to supply power to equipment over a long period of time, such as power supplies for water meters. Moreover, it has the characteristic that it can preserve | save for a long time in an unused state. There are several types of lithium primary batteries that differ in the shape of the battery can and the positional relationship between the positive electrode material and the negative electrode material inside the battery can, and the following Non-Patent Document 1 describes the structure of various lithium primary batteries. Etc. are described.

International Publication No. 2013/065290

Ina Denki Co., Ltd., “Manufacturer List, Sanyo Electric, Lithium Batteries”, [online], [Search July 2, 2013], Internet <URL: http://www.inedenki.co.jp/pdf/ sanyo_lit.pdf>

  By the way, in a device (such as a gas meter or a water meter) that operates over a long period of time using a lithium primary battery, the capacity of the lithium primary battery gradually disappears with long-term use, but the voltage drop is small until the end of discharge. Because of this characteristic, the device operates almost without problems until the capacity of the lithium primary battery built into the device is exhausted. That is, the device suddenly stops operating when the battery capacity is used up. For this reason, in a device that operates over a long period of time using a lithium primary battery as a power source, it is necessary to replace it with a sufficient margin before using up the battery capacity. In general, the battery is periodically replaced before the device stops due to a battery exhaustion.

  However, for some reason (moving, long absence, etc.), the device may be stopped before the battery replacement time, and the device may be left in the stopped state for a long time. In such a case, there may be an inconvenience that the device cannot be restarted after a long pause. Lithium primary batteries are excellent in long-term storage stability in an unused state, but there is a problem that internal resistance increases if they are stored for a long period after being discharged once. If the device is suspended at a time close to the end of the period, an electromotive force for restarting the device cannot be generated, and the device does not operate.

  Therefore, the main object of the present invention is to provide an organic electrolyte for achieving a lithium primary battery that can be stored for a long period of time even in the final stage of discharge, and a lithium primary battery using the organic electrolyte. .

To achieve the above object, the present invention provides 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, wherein LiCF ₃ SO is used as a supporting salt. ₃ is contained, and LiB (C ₂ O ₄ ) ₂ is added to form a non-aqueous organic electrolyte.

Preferably, the non-aqueous organic electrolytic solution to which the LiB (C ₂ O ₄ ) ₂ is added at a concentration of 0.1 mol / l or more is used. It is good also as a non-aqueous organic electrolyte solution to which the LiB (C ₂ O ₄ ) ₂ is added at a concentration of 0.5 mol / l or less.

  Furthermore, the present invention 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 includes the non-aqueous organic electrolysis according to any one of the above. It is characterized by having a liquid.

  According to the organic electrolytic solution of the present invention, it is possible to achieve a lithium primary battery in which the internal resistance does not easily increase even when stored for a long period in the final stage of discharge. Other effects will be clarified in the following description.

It is a figure which shows the structure of the lithium primary battery which concerns on one Embodiment of this invention. It is a figure which shows an internal resistance characteristic when the lithium primary battery using various organic electrolyte solution from which a composition differs is set | placed on 80 degreeC environment in the state discharged 80% of capacity | capacitance. It is a figure which shows an internal resistance characteristic when the lithium primary battery using the various organic electrolyte solution from which a composition differs is set | placed on 80 degreeC environment in the state discharged 90% of capacity | capacitance. It is a figure which shows an internal resistance characteristic when the lithium primary battery using the various organic electrolyte solution from which a composition differs is set | placed on the environment of -40 degreeC.

=== The process of conceiving the present invention ===
As described above, the lithium primary battery has a problem that the internal resistance increases when the lithium primary battery is stored once for a long period of time. And when this inventor considered the cause of this problem, he thought that it could explain by the following mechanisms. First, when a lithium primary battery using manganese dioxide as a positive electrode active material is incorporated and used in a device, manganese (Mn) ions contained in the composition of the positive electrode active material are eluted. When the use of the lithium primary battery is suspended and left for a long period of time, the eluted Mn ions are gradually reduced on the negative electrode surface, and Mn as a metal is deposited. The deposited metal Mn increases the interfacial resistance of the negative electrode and consequently increases the internal resistance of the battery.

  Next, assuming the above mechanism, the present inventor forms a film having ion conductivity on the positive electrode active material and the negative electrode active material, and forms a film that selectively allows Li ions to pass. It was thought that ion elution and precipitation of Mn in the negative electrode can be prevented. And if the property for forming the film mentioned above is given to electrolyte solution by modifying the non-aqueous organic electrolyte solution (henceforth, electrolyte solution) which touches both active materials of a positive electrode and a negative electrode, the film will be made quickly. We thought that it could be formed on the active material of both electrodes.

  Of course, if the basic ionic conductivity of the electrolytic solution is greatly deteriorated by modifying the electrolytic solution, it is a tip-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, it is practical to modify the electrolyte by adding a substance (additive) that is the origin of the coating to a general or representative conventional electrolyte. It is.

However, the prior art found in the research and development process by the present inventor has no precedent for an additive capable of forming an electrically conductive coating for an electrolyte of a lithium primary battery. Therefore, as a result of intensive research while verifying various experimental results obtained in the above discussion and research and development process, among the electrolytes for general lithium primary batteries, the supporting salt in the electrolyte is LiCF _3. When the basic electrolyte is SO ₃ , the basic electrolyte is LiB (C ₂ O ₄ ) ₂ (lithium bisoxalate borate: hereinafter referred to as LiBOB), which has never been used in conventional lithium primary batteries. It was found that long-term storage stability at the end of discharge in a lithium primary battery can be improved.

=== Embodiment of the Invention ===
The electrolytic solution according to the example of the present invention includes LiCF ₃ SO ₃ as a supporting salt and LiBOB. And in order to evaluate the characteristic of the electrolyte solution which concerns on a present Example, several types of lithium primary batteries from which the kind of additive contained in electrolyte solution, its density | concentration, etc. differed were produced as a sample.

<Sample structure>
A cylindrical spiral lithium primary battery was produced as a sample. FIG. 1 shows a schematic structure of the spiral lithium primary battery 1. This figure shows a longitudinal sectional view when the extending direction of the cylindrical shaft 100 is the vertical (vertical) direction. The lithium primary battery 1 includes a bottomed cylindrical metal battery can 2, a positive electrode 3, a negative electrode 4, a separator 5, a sealing body 6, and the like.

  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, a mixture of electrolytic manganese dioxide (EMD) as a positive electrode active material, a carbon material as a conductive material, and a fluorine-based binder at a ratio of 93%, 3%, and 4%, respectively, is used. The positive electrode material is slurried with pure water and applied to a stainless steel lath plate. The negative electrode 4 is made of a plate-like lithium metal or lithium alloy, and the negative electrode 4 and the positive electrode 3 are inserted into the battery can 2 in a state of being wound through a separator 5 made of a polyethylene microporous film.

  The sealing body 6 has a disk shape with 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, and the edge of the sealing body 6 and the upper portion of the battery can 2 are The edge is laser welded (at 90 in the figure). Further, a metal positive terminal 7 and a metal washer 8 are caulked through a gasket 9 in the central opening of the sealing body 6. Thereby, the opening of the battery can 2 is sealed, and the inside of the battery can 2 is sealed. The sealed battery can 2 is filled with an electrolytic solution 20 having a different composition depending on the sample. The positive electrode 3 (the lath plate) 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 (10, 11), respectively.

The electrolytic solution 20 is obtained by adding a kind and amount of additives according to a sample to an electrolytic solution (basic electrolytic solution) having a general composition for a lithium primary battery. Here, 1,2-dimethoxyethane (DME), propylene carbonate (PC), and ethylene carbonate (EC) are supported on a well-known three-component non-aqueous solution in proportions of 40 wt%, 30 wt%, and 30 wt%, respectively. A basic electrolyte is prepared by dissolving LiCF ₃ SO ₄ as a salt to a concentration of 0.5 mol / l (hereinafter referred to as M).

  Table 1 below shows the additives in the electrolyte solution used for each sample and the amount of addition.

表１に示したように、サンプル１では電解液に添加剤としてＮ−メチル-２-ピロリドン（ＮＭＰ）が０．１Ｍ添加されている。周知のごとく、ＮＭＰはラクタム構造を含む５員環の構造を持つ有機化合物である。また、サンプル２の電解液には添加剤が添加されていない基本電解液である。そして、サンプル３、４、５の電解液に添加剤としてＬｉＢＯＢがそれぞれ０．０５Ｍ、０．１Ｍ、０．５Ｍの濃度で添加されている。

As shown in Table 1, in sample 1, 0.1 M of N-methyl-2-pyrrolidone (NMP) is added to the electrolyte as an additive. As is well known, NMP is an organic compound having a 5-membered ring structure including a lactam structure. Further, the electrolyte solution of Sample 2 is a basic electrolyte solution in which no additive is added. Then, LiBOB is added as an additive to the electrolyte solutions of Samples 3, 4, and 5 at concentrations of 0.05M, 0.1M, and 0.5M, respectively.

=== Long-term storage performance ===
<Primary test>
Samples 1 to 5 shown in Table 1 were first subjected to a long-term storage performance test in a state where 80% of the capacity was discharged with respect to the nominal capacity. Specifically, a plurality of (for example, 100) individuals are prepared for each type of sample, and an accelerated deterioration test (hereinafter referred to as a primary test) is first placed on a high temperature environment of 80 ° C. for all individuals. went. And the relationship between the elapsed days from the start of a test and internal resistance was investigated. FIG. 2 shows the results of the primary test. In this figure, a graph is shown with the number of days elapsed from the start of the test as the horizontal axis and the relative value when the internal resistance (initial value) of each sample at the start is 1 as the vertical axis. The internal resistance of each sample is an average value of individuals belonging to the same type of sample.

As shown in FIG. 2, in sample 1 in which the additive in the electrolyte is NMP and sample 2 in which the basic electrolyte to which no additive is added is added, the internal resistance decreases after a large increase after the start of the test. It has increased again. In addition, the increase rate of the internal resistance with respect to the initial value is very large. On the other hand, in samples 3 to 5 in which LiBOB is added to the electrolytic solution, the internal resistance does not increase significantly from the initial value. In particular, in Samples 4 and 5 using an electrolytic solution to which LiBOB was added in an amount of 0.1 M or more, the internal resistance equivalent to the initial value was maintained for 150 days or more. Compared to samples 4 and 5, sample 3 has an internal resistance that increases with the number of days elapsed, but the rate of increase relative to samples 1 and 2 is about 1/2 to 1/3. Also, after 100 days, the internal resistance tended to saturate (become flat). From the above, it is confirmed that in an electrolytic solution containing LiCF ₃ SO ₃ as a supporting salt, if a small amount of LiBOB is added, the long-term storage performance from the end of discharge of a lithium primary battery using the electrolytic solution is improved. did it.

<Secondary test>
Next, the samples 2 to 5 were subjected to an accelerated deterioration test (secondary test) under conditions more severe than the primary test. In the secondary test, each sample was stored in an environment at 80 ° C. after discharging 90% capacity. FIG. 3 shows the result of the secondary test. In Sample 2 using an electrolyte solution to which no additive was added, the internal resistance increased rapidly from the time when 10 days passed from the start of the test. After 60 days, the internal resistance increased more than 10 times. In sample 3 using an electrolyte solution to which LiBOB was added to 0.05 M, the increase in internal resistance was more gradual than in sample 2, but the internal resistance increased after 10 days, and then Showed a tendency to increase the internal resistance gradually. In Samples 4 and 5 in which 0.1 M or more of LiBOB was added to the electrolyte, the internal resistance remained substantially unchanged without greatly increasing from the initial value. In particular, Sample 5 maintained the internal resistance almost unchanged from the initial value. From the above, it was confirmed that the longer the amount of LiBOB added, the better the long-term storage performance of the lithium primary battery in the final stage of discharge, and the more the amount added was 0.1 M or more.

=== Low-temperature characteristics ===
From the results of the primary test and the secondary test, if LiBOB is added to an electrolytic solution containing LiCF ₃ SO ₃ as a supporting salt, the lithium primary battery using the electrolytic solution has long-term storage performance in the end-of-discharge state. Will improve. It was confirmed that if the LiBOB concentration was 0.1 M or more, the storage performance was further improved. It was also confirmed that the long-term storage performance in the final stage of discharge tends to improve as the LiBOB concentration increases.

  However, if the concentration of LiBOB in the electrolytic solution is too high, the amount of additive in the electrolytic solution is relatively increased. Certainly, since the amount of the supporting salt responsible for ionic conduction in the electrolytic solution is constant, even if the concentration of LiBOB is somewhat high, it does not pose a big problem as long as the lithium ion battery is used in a general environment. However, there is a relative decrease in the amount of solvent that maintains the electrolyte as a fluid “liquid”, which can be problematic when used at extremely low temperatures, such as in cold regions and freezers. Therefore, an electrolyte solution in which LiBOB was added to the above basic electrolyte solution to a concentration of 0.6 M was prepared, and a lithium primary battery using the electrolyte solution was designated as sample 6. And the internal resistance in -40 degreeC was measured about samples 2-6. FIG. 4 shows the measurement results.

  In FIG. 4, the internal resistance value of sample 2 is 1, and the relative values of the internal resistances of samples 2 to 6 are shown. As shown in this figure, in samples 3 to 5 having a LiBOB concentration of 0.05M to 0.5M, the internal resistance was equivalent to the internal resistance of sample 2 using an electrolyte solution containing no additive. On the other hand, in sample 6 to which LiBOB was added to a concentration of 0.6M, the internal resistance was about 5 times that of sample 2. Therefore, when used at an extremely low temperature, the LiBOB concentration is desirably 0.5 M or less.

=== Other Embodiments ===
As a matter of course, the present invention is not limited to the above-described embodiments as long as the gist thereof is not exceeded. For example, in the composition of the electrolytic solution according to the embodiment of the present invention, the solvent may be any solvent as long as it dissolves the supporting salt LiCF ₃ SO _3, and the ratio of the above three components (DME, PC, EC) is also the above. The ratio is not limited. Of course, the solvent may not be a three-component system, and is generally used for Li primary batteries such as butylene carbonate (BC), dioxolane (DOXL), gamma-butyllactone (γ-BL), and tetrahydrofuran (THF). The electrolyte solution used may be used. The proportion of LiCF ₃ SO ₃ that is the supporting salt in the electrolytic solution can also be changed as appropriate, and it may be contained in a proportion that does not cause a practical problem as a lithium primary battery. The present invention is characterized in that LiBOB is added to an electrolytic solution for a lithium primary battery containing LiCF ₃ SO ₃ as a supporting salt.

1 lithium primary battery, 2 battery can, 3 positive electrode,
4 negative electrode (lithium metal or lithium alloy), 5 separator, 6 sealing body,
7 Positive terminal, 8 washer, 9 gasket, 20 Non-aqueous organic electrolyte

Claims (4)

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, which contains LiCF ₃ SO ₃ as a supporting salt and LiB (C ₂ O ₄ ) ₂ is added to the non-aqueous organic electrolyte. The non-aqueous organic electrolyte solution according to claim 1, wherein the LiB (C ₂ O ₄ ) ₂ is added at a concentration of 0.1 mol / l or more. 3. The non-aqueous organic electrolyte solution according to claim 1, wherein the LiB (C ₂ O ₄ ) ₂ is added at a concentration of 0.5 mol / l or less.   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 solution according to any one of claims 1 to 3 is provided. Primary lithium battery.

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