JP2007052935A - Nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery in which elevation of an open circuit voltage in storing can be suppressed. <P>SOLUTION: The nonaqueous electrolyte battery 1 has a positive electrode 2 having a positive electrode active material containing iron disulfide, a negative electrode 4, a negative electrode cap 5 to house the negative electrode 5, a separator 6 interposed between the positive electrode 2 and the negative electrode 4, a gasket 7, and an unillustrated nonaqueous electrolytic solution. A surface layer of the average thickness of less than 1,000 nm is provided on the positive electrode 2. By this, the elevation of the open circuit voltage in the storing can be suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolyte battery, for example, a positive electrode having a positive electrode active material containing iron disulfide, a negative electrode having lithium as a negative electrode active material, and an electrolytic solution obtained by dissolving an electrolyte in an organic solvent. For example, the present invention relates to a lithium / iron disulfide primary battery used at a discharge voltage of 1.9 V or less.

  In recent years, along with the development of small electronic devices, development of non-aqueous electrolyte batteries having light weight and high energy density as power sources has been promoted. Examples of the non-aqueous electrolyte battery include a lithium primary battery using a non-aqueous electrolyte solution obtained by dissolving an electrolyte in an organic solvent.

As a lithium primary battery, for example, as a positive electrode active material, a metal sulfide such as iron disulfide (FeS ₂ ), a metal oxide such as manganese dioxide (MnO ₂ ), or a negative electrode active material using lithium is proposed. Yes. (See Patent Document 1)

Japanese Patent No. 3060109

  Among them, the lithium / iron disulfide primary battery contains iron disulfide as a positive electrode active material, uses lithium as a negative electrode active material, can realize a high battery capacity, and further has a load characteristic, a low temperature characteristic, and the like. It is a battery with excellent characteristics.

  Since iron disulfide in the positive electrode active material shows higher theoretical capacity than manganese oxide, zinc, etc., which are the positive electrode active materials of other primary batteries, the lithium / iron disulfide primary battery can realize a high battery capacity.

  The lithium / iron disulfide primary battery has an initial circuit voltage of 1.7V to 1.8V and an average discharge voltage of about 1.3V to 1.6V. Therefore, the lithium / iron disulfide primary battery can be used as an alternative to the battery in a device using a primary battery of about 1.5V as a power source. For example, a voltage of about 1.5V such as a copper oxide / lithium primary battery Compatible with primary batteries.

  However, in a lithium / iron disulfide primary battery, for example, when the device is not used without being turned on for a long time in a state where it is attached to the device, the open circuit voltage may increase and exceed 2V. .

  If the device is turned on when the open circuit voltage is raised, the device is discharged at a high voltage state, so that the protection circuit on the device side is activated and the device cannot be used without turning on the power. That is, there is a problem that compatibility with other 1.5V class primary batteries is lost.

  Accordingly, an object of the present invention is to provide a nonaqueous electrolyte battery that can suppress an increase in open circuit voltage during storage.

  The inventors of the present application have made extensive studies for many years in order to suppress an increase in the open circuit voltage of a nonaqueous electrolyte battery. As a result, it has been found that an increase in open circuit voltage during storage can be suppressed by having a surface layer made of iron disulfide oxide having an average thickness of less than 1000 nm on the positive electrode, and the present invention has been completed.

That is, in order to solve the above-described problem, the present invention
A positive electrode having a positive electrode active material comprising iron disulfide;
A negative electrode having a negative electrode active material;
A non-aqueous electrolyte having an electrolyte salt,
A nonaqueous electrolyte battery having a surface layer having an average thickness of less than 1000 nm made of iron disulfide oxide on a positive electrode.

In this invention, the iron disulfide oxide is typically ferric trioxide (Fe ₂ O ₃ ). The iron disulfide oxide is typically triiron tetroxide (Fe ₃ O ₄ ). The iron disulfide oxide is typically iron oxide (FeO). The iron disulfide oxide is typically ferrous hydroxide (Fe (OH) ₂ ). The iron disulfide oxide is ferric hydroxide (Fe (OH) ₃ ).

  In the present invention, the thickness of the surface layer made of iron disulfide oxide typically has an average thickness of preferably less than 100 nm. The thickness of the surface layer made of iron disulfide oxide is typically more preferably an average thickness of less than 10 nm.

  In the present invention, it is preferable that the thickness of the surface layer made of iron disulfide oxide is typically within a range of ± 50% of the average thickness.

This invention
A positive electrode having a positive electrode active material comprising iron disulfide;
A negative electrode having a negative electrode active material;
A non-aqueous electrolyte having an electrolyte salt,
The nonaqueous electrolyte battery is characterized in that the coverage of the iron sulfate layer on the surface of the positive electrode active material is 50% or less.

In this invention, the iron sulfate layer is typically iron (III) sulfate (Fe ₂ (SO ₄ ) ₃ ). The iron sulfate is typically iron (II) sulfate (FeSO ₄ ).

This invention
A positive electrode having a positive electrode active material comprising iron disulfide;
A negative electrode having a negative electrode active material;
A non-aqueous electrolyte having an electrolyte salt,
The nonaqueous electrolyte battery is characterized in that the coverage of the iron sulfate layer on the surface of the positive electrode active material is 50% or less, and the surface layer made of iron disulfide oxide has an average thickness of 1000 nm on the positive electrode.

  According to the present invention, there is an effect that an increase in open circuit voltage during storage can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a nonaqueous electrolyte battery according to an embodiment of the present invention. This battery is, for example, a coin-shaped lithium / iron disulfide primary battery, and is used, for example, as a power source for small devices.

  As shown in FIG. 1, the nonaqueous electrolyte battery 1 includes a positive electrode 2, a positive electrode can 3 that accommodates the positive electrode 2, a negative electrode 4, a negative electrode lid 5 that accommodates the negative electrode 4, a positive electrode 2, and a negative electrode 4. A separator 6 interposed therebetween, a gasket 7, and a non-aqueous electrolyte (not shown) are included.

  In the nonaqueous electrolyte battery 1, the positive electrode can 3, the negative electrode 4, the separator 6, and the nonaqueous electrolyte solution are positive electrode 2 by caulking the positive electrode can 3 with a gasket 7 between the positive electrode can 3 and the negative electrode lid 5. The structure is enclosed by the can 3 and the negative electrode lid 5.

[Positive electrode 2]
The positive electrode 2 is formed by forming a positive electrode mixture layer containing a positive electrode active material on a positive electrode current collector 2a. As the positive electrode current collector 2a, for example, a thin metal such as aluminum (Al), a net-like metal, or the like can be used.

The positive electrode mixture layer includes, for example, a positive electrode active material, a conductive agent, a binder, and potassium carbonate (K ₂ CO ₃ ). As the conductive agent, for example, graphite, carbon black or the like can be used. As the binder, for example, polyvinylidene fluoride (PVdF) can be used.

As iron disulfide which is a positive electrode active material, for example, a material obtained by pulverizing pyrite mainly existing in nature can be used. Furthermore, for example, those generated by chemical synthesis can be used. Examples of the method for producing iron disulfide by chemical synthesis include a method of firing ferrous chloride (FeCl ₂ ) in hydrogen sulfide (H ₂ S).

  On the positive electrode 2, for example, a surface layer made of iron disulfide oxide and having an average thickness of less than 1000 nm is provided. Thereby, the raise of the open circuit voltage at the time of long-term storage can be suppressed. If the average thickness of the surface layer is less than 1000 nm, the mixed potential with iron disulfide can be suppressed, and thus an increase in open circuit voltage can be suppressed.

Examples of the iron disulfide oxide forming the surface layer include, for example, ferric trioxide (Fe ₂ O ₃ ), triiron tetroxide (Fe ₃ O ₄ ), iron oxide (FeO), and ferrous hydroxide (Fe (OH) ₂ ), ferric hydroxide (Fe (OH) ₃ ) and the like.

  Further, the average thickness of the surface layer is preferably less than 100 nm from the viewpoint that the increase in open circuit voltage during long-term storage can be further suppressed. Furthermore, the average thickness of the surface layer is preferably less than 10 nm from the viewpoint that the potential of only iron disulfide can be obtained and an increase in open circuit voltage during long-term storage can be remarkably suppressed.

  Furthermore, the thickness of the surface layer is preferably less than 50% of the average thickness of the surface layer from the viewpoint of suppressing a local potential increase. The average thickness of the surface layer can be defined by X-ray photoelectron spectroscopy (XPS).

  For example, the average thickness of the surface layer on the positive electrode is obtained by, for example, firing iron disulfide, which is a positive electrode active material, under predetermined conditions, and suppressing the coverage of the iron sulfate layer coated on the positive electrode active material surface, It can be suppressed to less than 1000 nm. For example, the average thickness of the surface layer can be suppressed to 1000 nm by using an electrolyte system that is not easily decomposed.

  For example, when suppressing the coverage of the iron sulfate layer coated with the positive electrode active material, the thickness of the positive electrode surface layer is obtained by having an iron sulfate layer with a coverage of 50% or less on the surface of iron disulfide that is the positive electrode active material. Therefore, the increase in the open circuit voltage of the nonaqueous electrolyte battery 1 can be suppressed.

When the surface of the positive electrode active material layer has an iron sulfate layer with a coverage of 50% or less, during storage, the iron sulfate can be dissolved in the electrolyte and the amount of oxygen source can be suppressed. Again, side reactions that produce iron disulfide oxides such as iron oxide can be suppressed. Examples of iron sulfate include iron (III) sulfate (Fe ₂ (SO ₄ ) ₃ ) and iron (II) sulfate (FeSO ₄ ).

  On the other hand, for example, when the coverage of the iron sulfate layer exceeds 50%, during storage, the iron sulfate dissolves in the electrolyte, and the amount of oxygen source increases, so that iron oxide and the like again with iron disulfide. The side reaction that produces the iron disulfide oxide proceeds. When this iron disulfide oxide layer becomes thick, a mixed potential with iron disulfide is generated, and the open circuit voltage rises.

  The coverage of the iron sulfate layer is preferably 15% or less from the viewpoint that the amount of an oxygen source dissolved in the electrolytic solution can be reduced and the increase in open circuit voltage during long-term storage can be further suppressed. .

  Note that the coverage of the iron sulfate layer is determined by the peak I (A) in the 161 eV to 164 eV region and the peak I in the 167 eV to 170 eV region in the S2p spectrum measured on the positive electrode active material surface by X-ray photoelectron spectroscopy (XPS). It can be defined by calculating from the ratio I (B) / I (A) × 100 with (B).

  The positive electrode can 3 is formed in a shallow dish shape that accommodates the positive electrode 2. For example, aluminum (Al), stainless steel (SUS), nickel (Ni), and the like from the inner side where the positive electrode 2 is accommodated in the thickness direction. Are sequentially stacked, and serve as the external positive electrode of the nonaqueous electrolyte secondary battery.

[Negative electrode 4]
In the negative electrode 4, a negative electrode active material layer 4b containing a negative electrode active material is formed on a negative electrode current collector 4a. The negative electrode current collector 4a uses, for example, a thin metal such as copper or a net-like metal as a current collector. For the negative electrode active material layer 4b, for example, a light metal such as lithium (Li), sodium (Na), or potassium (K), a light metal alloy, or the like is used.

  Examples of metals that can form alloys with light metals such as lithium include Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, and Cd, including semiconductors such as B, Si, and As. , Ag, Zn, Hf, Zr, Y, or the like can be used.

In addition, an alloy compound of a metal capable of forming an alloy with lithium is represented by the chemical formula M _s M ′ _t Li _u (M ′ is Li or M, where M is a metal element capable of forming an alloy with lithium described above). And s is a numerical value greater than 0. t and u are numerical values greater than or equal to 0.)

  Examples of the alloy compound include Li-Al, Li-Al-M1 (M1 is formed from one or more of 2A group, 3B group, 4B group, and transition metal element). Examples of M1 include AlSb and CuMgSb.

  The negative electrode lid 5 is formed in a shallow dish shape that accommodates the negative electrode 4, and is made of, for example, a plate material in which a surface of a conductive metal such as stainless steel or iron is plated with nickel, and the like. External negative electrode.

[Separator 6]
The separator 6 separates the positive electrode 2 and the negative electrode 4, prevents a short circuit of current due to contact between both electrodes, and allows lithium ions or the like in the nonaqueous electrolytic solution to pass therethrough. The separator 6 is a microporous film made of a resin having a large number of minute holes having an average particle diameter of holes of about 5 μm or less.

  As the resin, for example, olefin polymer, propylene polymer, cellulose polymer, polyimide, nylon, glass fiber, alumina fiber and the like can be used. In particular, for example, polypropylene or polyolefin is preferable as the separator 6 because it has an excellent short-circuit prevention effect and can improve battery safety due to a shutdown effect.

  The gasket 7 is made of, for example, an insulating resin such as polypropylene. The gasket 7 insulates the positive electrode can 3 and the negative electrode lid 5 and seals the airtightness inside the battery that is sealed by applying asphalt or the like to the surface. To prevent leakage of non-aqueous electrolyte.

[Electrolyte]
The nonaqueous electrolytic solution is prepared by appropriately combining an organic solvent and an electrolyte salt. Any organic solvent may be used as long as it is used in a non-aqueous electrolyte battery. For example, propylene carbonate, ethylene carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethyl. Examples include ethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, dipropyl carbonate, and the like.

Any electrolyte salt can be used as long as it is used for a non-aqueous electrolyte battery. Specifically, for example, lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), Any one or a mixture of lithium iodide (LiI) and the like can be used. In particular, for example, LiPF ₆ is preferable in that high ionic conductivity is obtained and charge / discharge cycle characteristics can be improved.

  Next, a method for manufacturing the nonaqueous electrolyte battery 1 according to one embodiment of the present invention will be described. For example, the nonaqueous electrolyte battery 1 according to one embodiment of the present invention can be manufactured as follows.

  First, the positive electrode 2 is produced. A positive electrode mixture coating solution containing a positive electrode active material made of iron disulfide, a conductive material, and a binder is prepared. Next, the positive electrode mixture coating solution 2b is formed by uniformly applying this positive electrode mixture coating solution onto a metal foil such as an aluminum foil that becomes the positive electrode current collector 2a and drying it. Next, the positive electrode current collector 2a and the positive electrode mixture layer 2b are collectively cut into a predetermined shape. The positive electrode 2 is produced by the above.

  Next, the negative electrode 4 is produced. A negative electrode active material layer 4b is formed by uniformly applying a negative electrode active material made of lithium onto a metal foil such as a copper foil to be the negative electrode current collector 4a. Next, the negative electrode current collector 4a and the negative electrode active material layer 4b are collectively cut out. In this way, the negative electrode 4 is produced. The negative electrode 4 may be manufactured by punching lithium into a predetermined shape and pressing the negative electrode lid 5 without using the negative electrode current collector 4a described above.

  Next, the positive electrode 2 is accommodated in the positive electrode can 3. The negative electrode 4 is accommodated in the negative electrode lid 5. At this time, the positive electrode 2 and the negative electrode 4 are arranged to face each other with a separator 6 made of a porous film between the positive electrode 2 and the negative electrode 4. Thereafter, the prepared nonaqueous electrolytic solution is poured into the positive electrode can 3 and the negative electrode lid 5.

  Next, a gasket 7 having a surface coated with asphalt or the like is provided between the positive electrode can 3 and the negative electrode lid 5, and the positive electrode can 3 is caulked and sealed. Thus, the coin-type non-aqueous electrolyte battery 1 having a structure in which the positive electrode 2, the separator 6, and the negative electrode 4 are sequentially stacked is manufactured.

  According to the nonaqueous electrolyte battery 1 according to the embodiment of the present invention, the layer of less than 1000 nm made of iron disulfide oxide is present on the surface of the positive electrode 2, so that the power source can be turned on for a long time in a state of being attached to the device. Even when it is not used without being inserted, the increase in the open circuit voltage can be suppressed.

  Furthermore, since an increase in open circuit voltage during long-term storage can be suppressed, good electrical connection can be maintained even when the device is turned on after long-term storage. Furthermore, since an increase in open circuit voltage during long-term storage can be suppressed, a decrease in discharge capacity can be suppressed.

  Furthermore, in the positive electrode used for the nonaqueous electrolyte battery 1, the thickness of the iron disulfide oxide layer on the surface of the positive electrode 2 can be suppressed by setting the coverage of the iron sulfate layer of the positive electrode active material to 50% or less. Therefore, an increase in open circuit voltage during long-term storage can be suppressed.

  That is, by using a positive electrode active material having a coverage of an iron sulfate layer of 50% or less, a high-quality non-aqueous electrolyte battery 1 having superior characteristics is produced in producing a battery that can be stored for a long period of time. can do.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples.

  First, iron disulfide as a positive electrode active material was sufficiently pulverized and mixed in a vibration mill, and fired in a gas atmosphere shown in Table 1 below. Table 1 shows the treatment conditions for iron disulfide used in the lithium / iron disulfide primary batteries of Examples 1 to 6 and Comparative Examples 1 to 3.

  Next, the coverage of Examples 1 to 6 and Comparative Examples 1 to 3 produced as described above was measured. The procedure is as follows.

  The positive electrode active material powder sample was fixed on an indium (In) foil. This sample is analyzed by X-ray photoelectron spectroscopy (XPS). The C1s peak is used for spectrum energy correction. Usually, the positive electrode active material has high conductivity, and charging by X-ray irradiation hardly occurs. The C1s spectrum of the sample is measured, waveform analysis is performed, and the position of the main peak existing on the lowest binding energy side is set to 284.5 eV. Commercially available software may be used for waveform analysis.

  In order to calculate the coverage of the iron sulfate layer, the S2p peak was analyzed. Analysis of the S2p peak was performed as follows. The S2p peak can be separated into a peak derived from the active material iron disulfide appearing in the 161 eV to 164 eV region and a peak derived from iron sulfate existing in the 167 eV to 170 eV region. However, since peak heights need only be compared here, it is not necessary to accurately perform peak separation. The background is preferably drawn using the Shirley method. After subtracting the background, the peak maximums in the 161 eV to 164 eV region and the 167 eV to 170 eV region were determined and compared. The peak intensity in the 161 eV to 164 eV region was I (A), the peak intensity in the 167 eV to 170 eV region was I (B), and a value of I (B) / I (A) × 100 was calculated. This value was defined as the coverage of the iron sulfate layer of the positive electrode active material.

  Table 2 below shows the coverage of the iron sulfate layers of Examples 1 to 6 and Comparative Examples 1 to 3 measured as described above.

  Next, lithium / iron disulfide primary batteries of Examples 1 to 6 and Comparative Examples 1 to 3 using iron disulfide having the coverage shown in Table 2 as the positive electrode active material were prepared.

<Example 1>
First, 95% by weight of iron disulfide having a coverage of 50% of the iron sulfate layer fired under the conditions shown in Table 1, 1% by weight of carbon powder (Ketjen Black) as a conductive agent, and as a binder A positive electrode mixture coating solution prepared by mixing 4% by weight of PVdF (polyvinylidene fluoride) and dispersing in N-methyl-pyrrolidone (NMP) was prepared.

  Next, the positive electrode mixture coating solution was dried at a temperature of 120 ° C. for 2 hours to volatilize N-methyl-pyrrolidone, and then pulverized using a mortar to produce a positive electrode mixture.

  Next, the positive electrode mixture is uniformly coated on an aluminum foil having a thickness of 30 μm serving as a positive electrode current collector and dried to form a positive electrode mixture layer. Thereafter, the positive electrode current collector and the positive electrode mixture are formed. The layers were collectively punched into a disk shape having a diameter of 15.5 mm and a thickness of 250 μm.

  Next, the punched positive electrode current collector and positive electrode mixture layer were accommodated in a positive electrode can formed by laminating aluminum, stainless steel, and nickel in this order from the inside of the container.

  Next, Li metal was punched into a disk shape having a diameter of 15.5 mm and a thickness of 800 μm, and the Li metal punched out from the inner side of the container to a negative electrode lid formed by laminating stainless steel and nickel in this order was pressed to produce a negative electrode.

  Next, in a solvent prepared by mixing 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) at a volume ratio of 2: 1, lithium iodide is adjusted to a concentration of 1 mol / l. The nonaqueous electrolyte solution was prepared by adding.

  Next, a separator made of polyethylene having a thickness of 25 μm is laminated between the positive electrode and the negative electrode, a nonaqueous electrolyte is injected into the positive electrode can and the negative electrode lid, and a gasket made of polypropylene is attached to the positive electrode can and the negative electrode lid. The positive electrode can was caulked and sealed between. As described above, the coin-type lithium / iron disulfide primary battery of Example 1 having a diameter of 20 mm and a thickness of 1.6 mm was produced.

<Example 2 to Example 6, Comparative Example 1 to Comparative Example 3>
Except that iron disulfide as the positive electrode active material was baked under the conditions shown in Table 1 and iron disulfide having the coverage shown in Table 2 was used as the positive electrode active material, everything was the same as in Example 1. Thus, lithium / iron disulfide primary batteries of Examples 2 to 6 and Comparative Examples 1 to 3 were produced.

  Next, the lithium / iron disulfide primary batteries of Examples 1 to 6 and Comparative Examples 1 to 3 manufactured as described above are two surface layers made of iron disulfide oxide on the positive electrode. The average thickness of the iron sulfide oxide layer was measured. The procedure is as follows.

  The positive electrode sample is washed with dimethyl carbonate after disassembling the battery. This is to remove the low-volatile solvent component and electrolyte salt present on the surface. It is desirable to perform sampling in an inert atmosphere as much as possible. This positive electrode sample is analyzed by X-ray photoelectron spectroscopy (XPS). The C1s peak is used for spectrum energy correction. Usually, this positive electrode sample has high conductivity, and charging due to X-ray irradiation hardly occurs.

  In order to qualify the iron disulfide oxide, the Fe2p peak was analyzed. The Fe2p peak was analyzed as follows. The Fe2p peak can be separated into a peak derived from iron disulfide, which is a positive electrode active material appearing in the 705 eV to 708 eV region, and a peak derived from iron disulfide oxide existing in the 709 eV to 712 eV region. However, since peak heights need only be compared here, it is not necessary to accurately perform peak separation. The background is preferably drawn using the Shirley method. After subtracting the background, the peak maximums in the 705 eV to 708 eV region and the 709 eV to 712 eV region are obtained and compared. The peak intensity in the 705 eV to 708 eV region is I (A), the peak intensity in the 709 eV to 712 eV region is I (B), and the value of I (A) / I (B) is calculated.

The thickness of the iron disulfide oxide layer was measured as follows. Conditions of accelerating voltage 1 kV, angle (photoelectron extraction angle, measured from the sample surface) 45 degrees, analyzer solid angle of capture ± 20 degrees, etching rate about 7.7 nm / min (SiO ₂ conversion) Etching with argon ions was used. At this time, the etching depth from the outermost surface when the value of I (A) / I (B) was 0.9 or more was defined as the thickness of the iron disulfide oxide layer. And the average value of the value obtained by measuring arbitrary five places on a positive electrode was made into average thickness.

  Table 3 below shows the average thicknesses of the iron disulfide oxide layers of Examples 1 to 6 and Comparative Examples 1 to 3 measured as described above.

  Next, the lithium / iron disulfide primary batteries of Examples 1 to 6 and Comparative Examples 1 to 3 were stored at 60 ° C. for 300 hours, and then the open circuit voltage was measured. As for the open circuit voltage, each battery was stored at 60 ° C., and the voltage during the storage was measured.

  Further, the lithium / iron disulfide primary batteries of Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to preliminary discharge for 10 hours (10 mAh) at a constant current of 1 mA, and about 10% of the battery capacity. Was discharged to lower the potential and then stored at 60 ° C. for 300 hours, and then the open circuit voltage was measured. As for the open circuit voltage, each battery was stored at 60 ° C., and the voltage during the storage was measured. The measurement results are shown in Table 4 below.

Examination of Coverage of Positive Electrode Active Material Based on the above measurement results, first, a preferred range of the coverage of the iron sulfate layer of the positive electrode active material was examined. As shown in Table 2, in Examples 1 to 6, the coverage of the iron sulfate layer of the positive electrode active material is 50% or less. On the other hand, in Comparative Examples 1 to 3, the coverage of the iron sulfate layer of the positive electrode active material exceeds 50%.

  As shown in Table 4, in Examples 1 to 6, the open circuit voltage is lower than that of Comparative Examples 1 to 3, and the increase in the open circuit voltage during long-term storage is suppressed. . Therefore, it was found that an increase in open circuit voltage during storage can be suppressed by setting the coverage of the iron sulfate layer of the positive electrode active material to 50% or less.

  When the coverage of the iron sulfate layer of the positive electrode active material is 50% or less, the increase in the open circuit voltage can be suppressed, during storage, the iron sulfate can be dissolved in the electrolyte and the amount of oxygen source can be suppressed. This is because side reactions that generate iron disulfide oxide such as iron oxide again with iron disulfide can be suppressed, and the thickness of the surface layer made of iron disulfide oxide formed on the positive electrode can be suppressed. is there.

  Furthermore, as shown in Tables 2 and 4, even in the battery after the preliminary discharge, the increase in the open circuit voltage of the battery can be suppressed by setting the coverage of the iron sulfate layer of the positive electrode active material to 50% or less. Recognize.

  Further, as shown in Table 4, the battery of Example 5 has an open circuit voltage without preliminary discharge of 1.79 V, an open circuit voltage with preliminary discharge of 1.81 V, and in Comparative Examples 1 to 3. In comparison, the increase in open circuit voltage is significantly suppressed. From Table 2, the coverage of the iron sulfate layer of the positive electrode active material of the battery of Example 5 is 13%.

  Further, as shown in Table 4, the battery of Example 6 has an open circuit voltage without preliminary discharge of 1.73 V, an open circuit voltage with preliminary discharge of 1.72 V, and in Comparative Examples 1 to 3. In comparison, the increase in the open circuit voltage is more significantly suppressed. From Table 2, the coverage of the iron sulfate layer of the positive electrode active material of the battery of Example 6 is 5%.

  Therefore, it was found that the coverage of the iron sulfate layer of the positive electrode active material is more preferably 15% or less from the viewpoint that the open circuit voltage can be remarkably suppressed.

Study of thickness of the surface layer was then examined in the thickness of the preferred range of the positive electrode of iron disulfide oxide layer. As shown in Table 3, in Examples 1 to 6, the average thickness of the iron disulfide oxide layer on the positive electrode is less than 1000 nm. On the other hand, in Comparative Examples 1 to 3, the average thickness of the iron disulfide oxide layer on the positive electrode is 1000 nm or more.

  As shown in Table 4, it can be seen that in Examples 1 to 6, the open circuit voltage is lower than in Comparative Examples 1 to 3, and the increase in the open circuit voltage during storage is suppressed. Therefore, it was found that an increase in open circuit voltage during long-term storage can be suppressed by having an iron disulfide oxide layer having an average thickness of less than 1000 nm on the positive electrode.

  By having an iron disulfide oxide layer having an average thickness of less than 1000 nm on the positive electrode, the increase in the open circuit voltage can be suppressed because the decomposition reaction of the electrolyte is further suppressed and the mixed potential with iron disulfide is remarkably generated. This is because there is not.

  Furthermore, as shown in Tables 3 and 4, even in the battery after the preliminary discharge, the mixed potential with iron disulfide remarkably occurs by having the iron disulfide oxide layer having an average thickness of less than 1000 nm on the positive electrode. Therefore, it can be seen that an increase in the open circuit voltage of the battery can be suppressed.

  Further, as shown in Table 4, the battery of Example 5 has an open circuit voltage without preliminary discharge of 1.79 V, an open circuit voltage with preliminary discharge of 1.81 V, and in Comparative Examples 1 to 3. In comparison, the increase in open circuit voltage is significantly suppressed. From Table 3, the average thickness of the iron disulfide oxide layer of the battery of Example 5 is 94 nm.

  Further, as shown in Table 4, the battery of Example 6 has an open circuit voltage without preliminary discharge of 1.73 V, an open circuit voltage with preliminary discharge of 1.72 V, and in Comparative Examples 1 to 3. In comparison, the increase in the open circuit voltage is more significantly suppressed. From Table 3, the average thickness of the iron disulfide oxide layer of the battery of Example 6 is 8 nm.

  Therefore, it was found that the average thickness of the iron disulfide oxide layer on the positive electrode is preferably less than 100 nm from the viewpoint that the increase in open circuit voltage can be remarkably suppressed. Further, it was found that the average thickness of the iron disulfide oxide layer on the positive electrode is more preferably less than 10 nm from the viewpoint that the increase in open circuit voltage can be suppressed more remarkably.

  Further, as a result of the examination of the coverage ratio and the thickness of the iron disulfide oxide layer on the positive electrode, the iron disulfide oxide layer on the positive electrode is formed by setting the coverage ratio of the iron sulfate layer of the positive electrode active material to 50% or less. It has been found that the average thickness of the film can be suppressed to less than 1000 nm, thereby suppressing an increase in open circuit voltage.

  The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the coin-type non-aqueous electrolyte battery 1 has been described. However, the present invention is not limited thereto, and the present invention can be applied to various shapes such as a cylindrical battery and a square battery. The present invention can also be applied to non-aqueous electrolyte batteries having a large size.

  The nonaqueous electrolyte battery is a gel electrolyte in which a solid electrolyte containing an electrolyte salt instead of a nonaqueous electrolyte or a matrix made of a nonaqueous solvent and an electrolyte salt is impregnated with an organic polymer. Can be used.

  Furthermore, in the above-described embodiment, the example of the non-aqueous electrolyte battery that is a primary battery has been described. However, the present invention is not limited to this, and any non-aqueous electrolyte battery can be applied to a secondary battery.

It is sectional drawing which shows the internal structure of the coin-type nonaqueous electrolyte battery by one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Nonaqueous electrolyte battery 2 ... Positive electrode 2a ... Positive electrode collector 2b ... Positive electrode mixture layer 3 ... Positive electrode can 4 ... Negative electrode 4a ... Negative electrode collector 4b ..Negative electrode active material layer 5 ... Negative electrode lid 6 ... Separator 7 ... Gasket

Claims (14)

A positive electrode having a positive electrode active material comprising iron disulfide;
A negative electrode having a negative electrode active material;
A non-aqueous electrolyte having an electrolyte salt,
A nonaqueous electrolyte battery comprising a surface layer having an average thickness of less than 1000 nm made of iron disulfide oxide on the positive electrode. In claim 1,
The non-aqueous electrolyte battery, wherein the iron disulfide oxide is ferric trioxide. In claim 1,
The non-aqueous electrolyte battery, wherein the iron disulfide oxide is triiron tetraoxide. In claim 1,
The non-aqueous electrolyte battery, wherein the iron disulfide oxide is iron oxide. In claim 1,
The nonaqueous electrolyte battery, wherein the iron disulfide oxide is ferrous hydroxide. In claim 1,
The non-aqueous electrolyte battery, wherein the iron disulfide oxide is ferric hydroxide. In claim 1,
The non-aqueous electrolyte battery, wherein an average thickness of the surface layer is less than 100 nm. In claim 1,
The nonaqueous electrolyte battery, wherein the surface layer has an average thickness of less than 10 nm. In claim 1,
The nonaqueous electrolyte battery according to claim 1, wherein the thickness of the surface layer is within a range of ± 50% of the average thickness. A positive electrode having a positive electrode active material comprising iron disulfide;
A negative electrode having a negative electrode active material;
A non-aqueous electrolyte having an electrolyte salt,
A nonaqueous electrolyte battery, wherein the coverage of the iron sulfate layer on the surface of the positive electrode active material is 50% or less. In claim 10,
The non-aqueous electrolyte battery, wherein the iron sulfate is iron (III) sulfate. In claim 10,
The non-aqueous electrolyte battery, wherein the iron sulfate is iron (II) sulfate. In claim 10,
The non-aqueous electrolyte battery, wherein the iron sulfate layer has a coverage of 15% or less. A positive electrode having a positive electrode active material comprising iron disulfide;
A negative electrode having a negative electrode active material;
A non-aqueous electrolyte having an electrolyte salt,
A nonaqueous electrolyte battery characterized in that the coverage of the iron sulfate layer on the surface of the positive electrode active material is 50% or less, and a surface layer having an average thickness of 1000 nm made of iron disulfide oxide is formed on the positive electrode.

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