JP5362436B2 - Lithium battery - Google Patents

Description

  The present invention relates to a lithium battery, and more particularly to improvement of storage characteristics, electrical characteristics, and reliability of a lithium battery under a high temperature environment.

  Conventionally, lithium batteries have been widely used as power sources for electronic devices whose operating temperature range is set to about −20 ° C. to 60 ° C. based on the temperature range of the living environment of people. On the other hand, in recent years, the application range of electronic devices using a battery as a power source has been expanded, and accordingly, the operating temperature range of electronic devices tends to be expanded. For example, a battery used in a vehicle-mounted electronic device such as a pressure sensor inside a tire can maintain a function for a certain period even when the environmental temperature is as high as about 125 ° C., and at a low temperature of about −40 ° C. Even if it exists, it is required to operate.

  As a battery suitable for use in such a high temperature environment, a lithium primary battery using manganese-containing oxides such as manganese dioxide or fluorinated graphite for the positive electrode and metallic lithium or lithium alloy for the negative electrode is a promising candidate. It has become. However, in this configuration, the solvent of the electrolytic solution reacts with the positive electrode and decomposes in a high temperature environment to generate gas. In particular, manganese-containing oxides such as manganese dioxide (hereinafter sometimes referred to simply as “manganese oxides”) have a catalytic action on the solvent of the electrolytic solution. The decomposition reaction of the liquid becomes remarkable. In particular, in a high temperature region exceeding 100 ° C., the electrolytic solution is further easily decomposed, and the internal pressure of the battery may be increased by the generated gas.

  In a coin-type battery, the contact between components inside the battery may be impaired due to an increase in the battery internal pressure, resulting in a decrease in pulse discharge characteristics due to an increase in internal resistance. In addition, there is a risk of battery leakage, breakage, and rupture, which may damage electronic equipment. In addition, in a cylindrical battery having a current collecting structure with leads, leakage of liquid or the like may occur due to an increase in battery internal pressure, which may deteriorate battery characteristics.

On the other hand, Patent Documents 1 and 2 propose a method of adding a cyclic sultone derivative, an acid anhydride, or the like to the electrolytic solution in order to suppress gas generation under such a high temperature region.
Patent Document 3 also proposes a method of suppressing gas generation under a high temperature environment by modifying manganese oxide.

JP 2005-216867 A JP 2004-47413 A JP 2006-100247 A

  According to the study by the present inventors, in the inventions described in Patent Documents 1 to 3, gas generation is suppressed in a temperature range of 100 ° C. or lower as compared with the conventional battery, and battery characteristics are improved. However, in the temperature region exceeding 100 ° C., the effect of suppressing gas generation is not sufficient, and it has been confirmed that there are problems such as an increase in internal resistance due to battery swelling, a resulting decrease in pulse discharge characteristics, and a leakage. In particular, since a battery used as a power source for an in-vehicle electronic device needs to withstand use in a high temperature region of about 125 ° C., the inventions described in Patent Documents 1 to 3 do not have a sufficient effect of suppressing gas generation. In addition, in the lithium battery according to the inventions described in Patent Documents 1 to 3, generally, the upper limit of the use environment temperature is about 60 ° C. to 85 ° C., and the use time is considered to be limited to a relatively short time. It is done.

  In order to obtain a further gas generation suppression effect, for example, it is conceivable to increase the amount of cyclic sultone derivatives, acid anhydrides, etc., but in this case, internal resistance increases, resulting in a decrease in pulse discharge characteristics. Becomes even more prominent. Therefore, it is difficult to improve the reliability in a high temperature environment by simply adding an additive to the electrolytic solution.

  An object of the present invention is to provide a lithium battery that suppresses gas generation in a high temperature region without deteriorating pulse discharge properties, and in particular, has improved storage characteristics and pulse discharge properties in a high temperature region of 100 ° C. or higher. .

In order to solve the above-described problems, a lithium battery of the present invention includes a positive electrode containing manganese oxide in a mixed crystal state, a negative electrode that releases lithium ions during discharge, and a nonaqueous electrolytic solution having lithium ion conductivity. The mixed crystal state manganese oxide contains at least λ-type manganese oxide and β-type manganese oxide, and the crystallinity of the β-type manganese oxide is greater than 500 and less than or equal to 800, and the non-aqueous electrolyte is LiClO ₄ , LiR ¹ SO ₃ (R ¹ represents a fluorinated alkyl group having 1 to 4 carbon atoms), and LiN (SO ₂ R ² ) (SO ₂ R ³ ) [R ² and R ³ are the same as or Unlikely, the fluorinated alkyl group having 1 to 4 carbon atoms is included] at least one solute selected from the group of 0.2 to 2 mol / L, and LiBF ₄ as an additive Total amount of water electrolyte Characterized in that it comprises a proportion of 0.1 to 4% by weight.

  According to the lithium battery, it is possible to suppress the decomposition of the non-aqueous electrolyte and the accompanying gas generation without deteriorating the pulse discharge characteristics. And since such an effect is fully exhibited not only in the living temperature range (-20 to 60 ° C.) but also in a high temperature range of 100 ° C. or higher (particularly about 125 ° C.), for example, the above high temperature Storage characteristics and pulse discharge characteristics can be improved in a wide temperature range including the range.

In the lithium battery, it is preferable that the content ratio of LiBF ₄ with respect to the total amount of the non-aqueous electrolyte is 1 to 3% by weight from the viewpoint of achieving both storage characteristics and pulse discharge characteristics.
In the lithium battery, the LiBF ₄ content is 100 parts by weight of the total amount of LiClO ₄ , LiR ¹ SO ₃ , and LiN (SO ₂ R ² ) (SO ₂ R ³ ) in the non-aqueous electrolyte. The amount is preferably 1 to 90 parts by weight.

  In the lithium battery, the crystallinity of β-type manganese oxide is more preferably 550 or more and 800 or less from the viewpoint of achieving both storage characteristics and pulse discharge characteristics.

In the lithium battery, the specific surface area of the mixed crystal manganese oxide is 0.5 m ² / g or more and 7.0 m ² / g or less from the viewpoint of achieving both storage characteristics and pulse discharge characteristics. preferable.

  The lithium battery is particularly suitable for application to a coin-type battery.

  According to the lithium battery of the present invention, gas generation can be suppressed in a high temperature environment of 100 ° C. or higher (particularly about 125 ° C.) without deteriorating pulse discharge characteristics. For this reason, storage characteristics and reliability at high temperatures can be remarkably improved. Further, according to the present invention, by suppressing gas generation, it is possible to further improve the reliability of the battery not only in the high temperature region but also in the living temperature region, for example. For this reason, a lithium battery suitable for an electronic device requiring long-term reliability can be obtained.

It is sectional drawing which shows an example of the coin-type lithium battery which concerns on embodiment of this invention.

  Next, the present invention will be described in detail by taking a coin-type lithium battery which is an embodiment of the present invention as an example.

  Referring to FIG. 1, a coin-type lithium battery 10 includes a positive electrode 3, a negative electrode 4, and a separator 5 interposed between the positive electrode 3 and the negative electrode 4. These are housed in a battery case 1 that also serves as a positive electrode terminal, and in contact with a non-aqueous electrolyte (not shown) in the battery case 1.

  A sealing plate 2 that is also used as a negative electrode terminal is disposed in the opening of the battery case 1. The sealing plate 2 is provided with a gasket 6 that is injection-molded in an annular shape. The open end of the battery case 1 is bent inward, and the gasket 6 is tightened between the sealing plate 2 and a coin-type lithium battery. Is sealed.

In the coin-type lithium battery 10 of FIG. 1, the positive electrode 3 contains mixed oxide manganese oxide as an active material.
The mixed crystal state manganese oxide includes at least λ-type manganese oxide (manganese oxide having a λ-type crystal structure) and β-type manganese oxide (manganese oxide having a β-type crystal structure). In this mixed crystal state manganese oxide, the oxidation number of manganese is typically tetravalent. However, it is not limited to this value, and a slight increase / decrease is allowed.

  The λ-type manganese oxide can be prepared, for example, by using spinel-type lithium manganese oxide as a raw material and contacting this with a sulfuric acid solution to remove lithium. The lithium content in manganese oxide can be arbitrarily controlled by adjusting the contact time between the spinel type lithium manganese oxide and the sulfuric acid solution. Further, the λ-type manganese oxide is not limited to the one obtained by the above preparation method, and any preparation method may be used.

  β-type manganese oxide can be prepared using λ-type manganese oxide obtained from spinel type lithium manganese oxide by the above preparation method. Specifically, first, sulfuric acid remaining in the λ-type manganese oxide is removed by washing and drying, and then the obtained λ-type manganese oxide is fired at 100 ° C. or more and 300 ° C. or less. Thereby, a part of λ-type manganese oxide is converted into β-type manganese oxide.

  As for the mixed crystal state manganese oxide used in the present invention, for example, the λ-type manganese oxide obtained by the above preparation method does not cause oxygen deficiency at 100 ° C. or more and 300 ° C. or less for about 1 to 6 hours. It is prepared by firing while supplying air.

In mixed-crystal manganese oxide, the crystallinity of β-type manganese oxide is set in the range of more than 500 and 800 or less. By setting the crystallinity of β-type manganese oxide in the above range, both high temperature storage characteristics and pulse discharge characteristics can be achieved.
The crystallinity is a parameter for evaluating the crystal state. The crystal state of β-type manganese oxide partially formed in λ-type manganese oxide by heat treatment can be evaluated by the crystallinity.

  When the crystallinity of β-type manganese oxide is set within the above range, the penetration of lithium ions into the lattice of manganese oxide (surface reactivity), the diffusibility of lithium ions inside manganese oxide, The balance such as the stability of lithium ions in the lattice is optimized. For this reason, electrical characteristics, particularly large current discharge characteristics and pulse discharge characteristics are improved.

  On the other hand, if the crystallinity of β-type manganese oxide exceeds the above range, lithium will not easily enter the lattice of manganese oxide, or the amount of manganese oxide available for discharge will be reduced. For this reason, the discharge characteristics deteriorate. Conversely, if the crystallinity of β-type manganese oxide is below the above range, the activity of manganese oxide becomes too high, and the solvent in the non-aqueous electrolyte is decomposed by the catalytic action of manganese oxide. Insufficient suppression is possible, or the internal resistance of the battery increases.

  The crystallinity of β-type manganese oxide is preferably 550 to 800, more preferably 600 to 700, particularly in the above range.

  For the crystallinity of β-type manganese oxide, the peak attributed to the (110) plane of β-type manganese oxide was selected from the X-ray diffraction pattern measured for the mixed crystal state manganese oxide, and the peak height ( (Strength) is divided by its half width.

About the manganese oxide of a mixed crystal state, it is preferable that the specific surface area is 0.5-7 m < ² > / g. By setting the specific surface area of the mixed crystal manganese oxide within the above range, both the storage characteristics and the pulse discharge characteristics can be further improved.
On the other hand, if the specific surface area of the mixed crystal manganese oxide is less than the above range, the discharge reaction field where the non-aqueous electrolyte and manganese oxide come into contact decreases, and the continuous discharge performance and pulse discharge characteristics at a large current decrease. There is a risk. On the other hand, if the specific surface area of the mixed crystal manganese oxide exceeds the above range, the effect of suppressing the decomposition reaction of the non-aqueous electrolyte by manganese oxide may be reduced, and gas generation may not be sufficiently suppressed.

The specific surface area of the mixed crystalline manganese oxide is, among the above range is preferably 0.5~6m ² / g, more preferably from 3 to 6 m ² / g.

  The positive electrode 3 is, for example, mixed manganese oxide in a mixed crystal state as a positive electrode active material and, if necessary, components such as a conductive agent and a binder, and the positive electrode mixture thus obtained is used as the shape of the positive electrode 3. According to the above, it is manufactured by molding into a disk shape, a flat plate shape or the like.

  Examples of the conductive agent include various conductive agents known in this field. Specific examples include graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, carbon fiber, and various metal fibers. These may be used alone or in combination of two or more.

  Examples of the binder include various binders known in this field. Specific examples include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer. These may be used alone or in combination of two or more.

  The positive electrode may be formed, for example, by forming a layer made of a positive electrode mixture on the surface of the positive electrode current collector. In this case, as the positive electrode current collector, for example, stainless steel, aluminum, titanium, or the like can be used. The positive electrode mixture layer includes, for example, mixed crystal manganese oxide as a positive electrode active material, a liquid component for dispersing the manganese oxide, and components such as a conductive agent and a binder as necessary. The positive electrode mixture slurry thus obtained can be applied to the surface of the positive electrode current collector and dried. When the lithium battery of the present invention is not a coin-type battery shown in FIG. 1 but a so-called cylindrical or square battery, the positive electrode produced as described above is suitable.

  In the coin-type lithium battery of FIG. 1, the negative electrode 4 is formed of a material that releases lithium ions during discharge. Specific examples include, but are not limited to, lithium metal and lithium alloys. These may be used alone or in combination of two or more.

  The negative electrode 4 is produced, for example, by forming a metallic lithium or lithium alloy hoop material into a disk shape, a flat plate shape, or the like according to the shape of the negative electrode 4.

  The negative electrode may be formed, for example, by forming a layer made of a negative electrode mixture on the surface of the negative electrode current collector. In this case, as the negative electrode current collector, for example, copper, nickel, stainless steel, or the like can be used. In addition, the negative electrode mixture layer is, for example, a carbon material preliminarily provided with lithium, a negative electrode active material such as a compound containing lithium, a liquid component for dispersing the negative electrode active material, and, if necessary, It can be formed by mixing components such as a conductive agent and a binder, applying the negative electrode mixture slurry thus obtained to the surface of the negative electrode current collector, and drying. When the lithium battery of the present invention is not a coin-type battery shown in FIG. 1 but a so-called cylindrical or square battery, the negative electrode produced as described above is suitable.

  In the coin-type lithium battery of FIG. 1, various materials known in the field of the present invention can be used for the separator 5. Specifically, for example, a resin nonwoven fabric or a microporous film can be used, and these are used, for example, by punching into a circle. Examples of the material for forming the separator 5 include polyphenylene sulfide (PPS), polyethylene, polypropylene, a mixture of polyethylene and polypropylene, and a copolymer of ethylene and propylene.

In the coin-type lithium battery of FIG. 1, the non-aqueous electrolyte contains a specific solvent and a solute (lithium salt) described later, has lithium ion conductivity, and further contains LiBF ₄ as an additive. doing. This non-aqueous electrolyte penetrates into the positive electrode 3 and the separator 5.

  Examples of the solvent for the non-aqueous electrolyte include chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), such as ethylene carbonate (EC), propylene carbonate (PC), Cyclic carbonates such as butylene carbonate, for example, chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEC), ethoxymethoxyethane (EMC), such as tetrahydrofuran, 2-methyl Examples include cyclic ethers such as tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, and cyclic carboxylic acid esters such as γ-butyrolactone. These may be used alone or in combination of two or more.

  Among the above solvents, cyclic carbonates have high boiling points and viscosities, so that when these are used, battery characteristics at low temperatures deteriorate. For this reason, when the non-aqueous electrolyte contains a cyclic carbonate, it is preferable that the non-aqueous electrolyte further contains a low boiling point and low viscosity cyclic ether.

  The coin-type lithium battery uses manganese oxide for the positive electrode. For this reason, a mixed solvent of a carbonate ester solvent PC and an ether solvent DME is particularly suitable as the solvent of the non-aqueous electrolyte. The mixing ratio of PC and DME is preferably 20:80 to 80:20, and more preferably 40:60 to 60:40, by volume.

  When the solvent of the non-aqueous electrolyte contains PC and DME, the ratio of the total amount of PC and DME to the total amount of the non-aqueous electrolyte is not limited to this, but preferably 40 to 98% by weight More preferably, it is 70 to 97% by weight.

Examples of the solute (lithium salt) contained in the non-aqueous electrolyte include LiClO ₄ , LiR ¹ SO ₃ (R ¹ is the same as above), and LiN (SO ₂ R ² ) (SO ₂ R ³ ) [ R ² and R ³ are the same as described above]. These lithium salts may be used alone or in combination of two or more.

In the lithium salt (sulfonate) represented by LiR ¹ SO ₃ , the fluorinated alkyl group having 1 to 4 carbon atoms represented by R ¹ is preferably a perfluoroalkyl group having 1 to 4 carbon atoms. More specifically, perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl and the like can be mentioned.

In the lithium salt (imide salt) represented by LiN (SO ₂ R ² ) (SO ₂ R ³ ), the fluorinated alkyl group having 1 to 4 carbon atoms represented by R ² and R ³ is preferably carbon. Examples of the perfluoroalkyl of formulas 1 to 4 include perfluoromethyl, perfluoroethyl, perfluoropropyl, and perfluorobutyl.

In the present invention, since the positive electrode active material is manganese oxide, LiClO ₄ is particularly suitable as the lithium salt.

  The concentration of the lithium salt in the non-aqueous electrolyte is 0.2 to 2.0 mol / L, preferably 0.3 to 1.5 mol / L, and more preferably 0.4 to 1. 2 mol / L.

The nonaqueous electrolytic solution further contains LiBF ₄ as an additive. This LiBF ₄ is considered to form a film on the surface of the positive electrode 3 particularly in a high temperature environment and reduce decomposition of the non-aqueous electrolyte. Therefore, the larger the amount of LiBF ₄ added, the less likely gas is generated in a high temperature environment, and the swelling of the battery is suppressed. However, on the other hand, an increase in the internal resistance of the battery, a resulting decrease in discharge capacity, and a decrease in pulse discharge characteristics are caused.
For this reason, the addition amount of LiBF ₄ is set to 0.1 to 4% by weight, preferably 1 to 3% by weight, particularly preferably 2 to 3% by weight, based on the total amount of the non-aqueous electrolyte. Is set. With such an addition amount in the range, all of LiBF ₄ added to the non-aqueous electrolyte is not consumed for film formation, and an increase in the internal resistance of the battery can be prevented.

The content of LiBF ₄ is preferably ^{1 to} 90 with respect to 100 parts by weight of the total amount of LiClO ₄ , LiR ¹ SO ₃ and LiN (SO ₂ R ² ) (SO ₂ R ³ ) in the non-aqueous electrolyte. Parts by weight, more preferably 15 to 90 parts by weight, particularly preferably 35 to 70 parts by weight.

As a general composition of the non-aqueous electrolyte, for example, the solvent of the non-aqueous electrolyte is a mixed solvent containing PC and DME at a volume ratio of 1: 1, the solute is LiClO ₄ , and the concentration of the solute is An example is 0.5 mol / L. In such a case, the content of LiBF ₄ is preferably 1 to 40 parts by weight with respect to 100 parts by weight of LiClO ₄ .

In the present invention, mixed oxide manganese oxide containing γ-type manganese oxide and β-type manganese oxide and having a crystallinity of β-type manganese oxide in the above range is used as the positive electrode active material. The non-aqueous electrolyte containing the above solute in the above proportion and containing LiBF ₄ in the above proportion as an additive is used. Thereby, according to this invention, a storage characteristic and a pulse discharge characteristic can be made compatible, and the reliability of a battery can be improved further. The above synergistic effect obtained by using the above-described positive electrode active material and the above-described non-aqueous electrolyte is, as shown in Examples described later, in a high temperature environment of 100 ° C. or higher (particularly about 125 ° C.). Appears prominently.

  In the above description, the embodiment of the present invention has been described by taking a coin-type lithium battery as an example. However, the shape of the lithium battery of the present invention is not limited to this, and depending on its use and the like. For example, various shapes such as a cylindrical shape, a square shape, a sheet shape, a flat shape, a laminated shape, and a button shape can be appropriately selected.

  Next, the present invention will be described in detail based on specific examples.

(1) Preparation of mixed crystal state manganese oxide First, manganese dioxide, lithium hydroxide, and lithium carbonate were mixed at a predetermined ratio, and this was fired at 800 ° C. to prepare a spinel type lithium manganese oxide. . The obtained spinel type lithium manganese oxide was immersed in a sulfuric acid solution to remove lithium from the lithium manganese oxide, and then washed and dried to prepare λ-type manganese oxide.

Next, the obtained λ-type manganese oxide was heat-treated in air at 200 ° C. for 2 hours. Thus, a mixed crystal state manganese oxide containing β-type manganese oxide and λ-type manganese oxide, having a specific surface area of 4.0 m ² / g and a β-type manganese oxide crystallinity of 600 was obtained.

  The crystallinity and specific surface area of manganese oxide were measured or determined by the following methods, respectively.

<Crystallinity>
The crystallinity is a peak attributed to the (110) plane of β-type manganese oxide by measuring the diffraction pattern of manganese oxide in a mixed crystal state using an X-ray diffractometer (manufactured by Philips, “X'Pert”). The height (strength) was divided by its half width.

<Specific surface area>
The specific surface area was measured by the BET specific surface area analysis method (multipoint method). As the measuring instrument, “ASAP2010” manufactured by Shimadzu Corporation (manufactured by Micromeritex Corporation) was used, and nitrogen was used as the adsorption gas.

(2) Production of positive electrode To 100 parts by weight of the obtained mixed crystal state manganese oxide, 5 parts by weight of ketjen black as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder are added, The mixture was mixed well to prepare a positive electrode mixture. And after shape | molding this positive electrode mixture in the disk shape of diameter 20mm and thickness 3.0mm, it dried at 200 degreeC and produced the positive electrode.

(3) Production of negative electrode A hoop made of metal lithium having a thickness of 1.0 mm was punched into a disk shape having a diameter of 20 mm, and this was used as the negative electrode.

(4) Preparation of non-aqueous electrolyte In the non-aqueous electrolyte, propylene carbonate (PC) and 1,2-dimethoxyethane (DME) are used as a non-aqueous solvent, and these are used in a volume ratio of 50:50. Mixed. Then, LiClO ₄ as a solute was dissolved in this mixed solvent at a concentration of 0.5 mol / L. Further, LiBF ₄ was added so as to be 2.0% by weight with respect to the total amount of the non-aqueous electrolyte, and dissolved to obtain a non-aqueous electrolyte.

In the non-aqueous electrolyte, the content of LiBF ₄ was about 42.0 parts by weight with respect to 100 parts by weight of the solute (LiClO ₄ ) of the non-aqueous electrolyte.

(5) Production of Coin Type Lithium Battery As the separator 5, a polyphenylene sulfide (PPS) nonwoven fabric was used. PPS was also used for the gasket 6.
And the positive electrode 3 and the separator 5 were arrange | positioned in this order to the battery case (positive electrode terminal) 1 made from stainless steel. On the other hand, a negative electrode 4 was disposed on the inner surface of a stainless steel sealing plate (negative electrode terminal) 2, and a gasket 6 was disposed on the periphery thereof. Then, after injecting the non-aqueous electrolyte into the battery case 1 and bringing the positive electrode 3 and the separator 5 into contact with the non-aqueous electrolyte, the battery case 1 is sealed with a sealing plate 2, and FIG. A coin-type lithium battery shown in FIG. This battery was designated as battery A.

In addition, a coin-type lithium battery was produced in the same manner as Battery A except that LiBF ₄ was not added to the nonaqueous electrolytic solution, and this was designated as Battery B.
As the positive electrode active material, in the same manner as the battery A, except that 100 parts by weight of β-type manganese oxide having a specific surface area of 15.0 m ² / g and a crystallinity of 100 was used instead of the mixed crystal manganese oxide. Thus, a coin-type lithium battery was produced and designated as battery C.
Further, a non-aqueous electrolyte to which LiBF ₄ was not added was used, and the positive electrode active material was replaced with manganese oxide in a mixed crystal state with a specific surface area of 15.0 m ² / g and a crystallinity of 100. 100 parts by weight of β-type manganese oxide was used. Otherwise, a coin-type lithium battery was produced in the same manner as battery A, and this was designated as battery D.

Further, a coin-type lithium battery was fabricated in the same manner as the battery A except that the amount of LiBF ₄ added in the non-aqueous electrolyte was changed. The addition amount of LiBF ₄ is as follows, as the content ratio (% by weight) with respect to the total amount of the nonaqueous electrolyte, and as the weight ratio (parts by weight) when the addition amount of LiClO _{4 as} the solute is 100 parts by weight. It is.
Battery E: 0.05% by weight, about 1.03 parts by weight Battery F: 0.1% by weight, about 2.10 parts by weight Battery G: 1.0% by weight, about 20.8 parts by weight (Battery A: 2 0.0 wt%, about 42.0 parts by weight)
Battery H: 3.0% by weight, about 63.8 parts by weight Battery I: 4.0% by weight, about 85.8 parts by weight Battery J: 5.0% by weight, about 108 parts by weight

(6) Evaluation of Physical Properties of Battery The following evaluation was performed on the batteries A to J.

<Battery swelling during high temperature storage>
Each battery was stored in an environment of 125 ° C. for 240 hours, and the change in battery thickness (mm) was measured before and after storage. The amount of increase (mm) in battery thickness was defined as “swell”. Further, before and after storage, the change in the internal resistance (IR) of the battery was measured by an alternating current method (measurement frequency: 1 kHz). The measured increase in internal resistance (Ω) was taken as the IR change amount and indicated by “ΔIR”. The measurement results are shown in Tables 1 and 2.

<Low-temperature pulse voltage>
Each battery was left in an environment of −40 ° C. for 3 hours, and the temperature of the battery surface was adjusted to −40 ° C. Thereafter, a cycle (intermittent discharge) in which discharge was performed for 0.5 seconds at a current value of 8 mA and then was stopped for 2 minutes was repeated for 50 hours. And the minimum voltage (pulse voltage [V]) of the battery during intermittent discharge was measured. The measurement results are shown in Tables 1 and 2.

  In the table below, the physical property evaluation column has four grades of “A +”, “A”, “B”, and “C”. This evaluation indicates, in order, for each evaluation item, “very good”, “good”, “practically acceptable” and “unsuitable for practical use”.

As shown in Table 1, the battery B using manganese oxide in a mixed crystal state has either a swollen dimension (bulge) after storage or an IR change (ΔIR) as compared with the battery D using β-type manganese dioxide. Is also suppressed, and the characteristics under high temperature environment are improved. In addition, the battery C in which 2.0% by weight of LiBF ₄ was added to the non-aqueous electrolyte has both the swollen dimensions after storage and the IR change amount suppressed as compared with the battery D to which no LiBF ₄ was added. Improved environmental characteristics. In all cases, the value of the pulse voltage was maintained at a practically sufficient value or more.
On the other hand, the battery A using manganese oxide in a mixed crystal state and adding 2.0% by weight of LiBF ₄ to the non-aqueous electrolyte is compared with the battery B in which LiBF ₄ is not added to the non-aqueous electrolyte after storage. Both the swollen dimension and the IR change amount were greatly suppressed, and the characteristics under a high temperature environment were remarkably improved.

That is, a mixed crystal state manganese oxide having a high crystallinity and a small specific surface area is used as compared with the case where general β-type manganese dioxide is used as the positive electrode active material and LiBF ₄ is added to the non-aqueous electrolyte. When used as a positive electrode active material and LiBF ₄ is added to the non-aqueous electrolyte, it is found that the characteristics under high temperature environment with respect to swollen dimensions and IR change after storage are significantly improved due to synergistic effects. It was.

As shown in Table 2, a non-aqueous battery F~I added LiBF ₄ at a range of 0.1 to 4 wt% in the electrolyte, as compared with battery B was not added LiBF ₄ in the non-aqueous electrolyte solution Both the swelling size (bulging) after storage and the IR change amount (ΔIR) were suppressed.
In addition, in the battery E in which the amount of LiBF ₄ added was less than 0.1% by weight, the swelling size after storage was smaller than that in the battery B, but the effect was smaller than those in the batteries F to J. Further, in Battery J in which the amount of LiBF ₄ added was 5.0% by weight, the swollen dimension after storage could be sufficiently suppressed, but the amount of IR change increased.

From these results, when the amount of LiBF ₄ added is small, the effect of suppressing gas generation due to decomposition of the non-aqueous electrolyte is less likely to appear, and conversely, when the amount of LiBF ₄ added is large, it is caused by decomposition of the non-aqueous electrolyte. Although gas generation can be suppressed, the resistance component is considered to increase.

Next, the crystallinity of the β-type manganese oxide in the mixed crystal manganese oxide was examined.
A battery was produced in the same manner as battery A, except that the crystallinity of β-type manganese oxide was changed to the values shown in Table 3, and batteries K to Q were obtained. In these batteries K to Q, the specific surface area of manganese oxide in a mixed crystal state was set to 4.0 m ² / g.

  The crystallinity of β-type manganese oxide was controlled by changing the heat treatment temperature of λ-type manganese oxide in the range of 100 ° C. to 300 ° C. while keeping the average particle size of manganese oxide constant.

In order to evaluate the physical properties of these batteries, in the same manner as battery A, “battery swelling during high temperature storage”, “IR change amount during high temperature storage” and “low temperature pulse voltage” were measured. The results are shown in Table 3.
The “IR change amount at high temperature storage” was measured not only when the temperature of the storage environment of the battery was 125 ° C. but also when it was set to 100 ° C.

  As shown in Table 3, the batteries L to P were able to suppress both the swelling after high temperature storage and the IR change amount as compared with the batteries K and Q. On the other hand, in the battery K having a crystallinity of less than 500, the battery was slightly swollen by gas generation due to decomposition of the non-aqueous electrolyte, and the IR change amount was remarkably increased. On the other hand, in the battery Q having a crystallinity of 900 or more, it was possible to suppress swelling and IR change after storage at high temperature, but since the lithium did not easily enter the manganese oxide lattice, the pulse voltage was slightly higher. Declined.

Next, the specific surface area of the mixed crystal manganese oxide was examined.
A battery was produced in the same manner as the battery A, except that the specific surface area of the mixed crystal manganese oxide was changed as shown in Table 4, and batteries R to X were obtained. In all of these batteries R to X, the crystallinity of manganese oxide was 600.

  In addition, the specific surface area of the mixed crystal state manganese oxide was controlled by changing the heat treatment temperature of the λ-type manganese oxide in the range of 100 ° C. to 300 ° C. while keeping the content of lithium contained in the manganese oxide constant. .

  In order to evaluate the physical properties of these batteries, in the same manner as battery A, “battery swelling during high temperature storage”, “IR variation during high temperature storage” and “low temperature pulse voltage” were measured. The results are shown in Table 4.

As shown in Table 4, the batteries R to X had both small swell dimensions after storage and IR variation, and the pulse voltage was also good. In the battery R having a specific surface area of less than 0.5 m ² / g, the swollen dimensions after storage and the IR change amount were good, but the pulse voltage was slightly lowered. This is thought to be because the discharge reaction field was reduced because the specific surface area of manganese oxide was small. Further, in the battery X having a specific surface area of more than 7.0 m ² / g, the pulse voltage was good, but the swelling size after storage and the IR change amount were slightly increased. This is presumably because the portion of the manganese oxide that is in contact with the non-aqueous electrolyte is increased due to the large specific surface area, and the generation of gas due to the decomposition of the non-aqueous electrolyte is increased.

  In the above description, the embodiment of the coin-type lithium battery (primary battery) has been described as an example, but the present invention is not limited to this embodiment. The present invention can be applied to various forms such as a cylindrical battery and a rectangular battery. In addition, the negative electrode can be applied to a lithium ion battery (secondary battery) by using a highly reversible lithium alloy, a carbon material in which lithium is previously occluded, a lithium-containing compound, or the like.

  The lithium battery of the present invention is particularly suitable for applications in which devices are driven at a wide temperature range of −40 ° C. to 125 ° C. Furthermore, in use in such a temperature range, devices that require long-term reliability It is suitable for a device that requires excellent large current discharge characteristics or pulse discharge characteristics. The lithium battery of the present invention is particularly applicable to high quality tire pressure monitoring (management) systems (TPMS).

1 Battery case (positive terminal)
2 Sealing plate (negative electrode terminal)
3 Positive electrode 4 Negative electrode 5 Separator 6 Gasket 10 Coin-type lithium battery

Claims (6)

A positive electrode containing manganese oxide in a mixed crystal state, a negative electrode that releases lithium ions during discharge, and a nonaqueous electrolytic solution having lithium ion conductivity,
The mixed crystal state manganese oxide includes at least λ-type manganese oxide and β-type manganese oxide,
The crystallinity of the β-type manganese oxide is greater than 500 and less than or equal to 800;
The non-aqueous electrolyte includes LiClO ₄ , LiR ¹ SO ₃ (R ¹ represents a fluorinated alkyl group having 1 to 4 carbon atoms), and LiN (SO ₂ R ² ) (SO ₂ R ³ ) [R ² and R ³ is the same as or different from each other and represents a fluorinated alkyl group having 1 to 4 carbon atoms], and contains at least one solute selected from the group of 0.2 to 2 mol / L, and as an additive A lithium battery containing 0.1 to 4% by weight of LiBF ₄ with respect to the total amount of the non-aqueous electrolyte. The lithium battery according to claim 1, wherein a content ratio of LiBF ₄ with respect to a total amount of the non-aqueous electrolyte is 1 to 3 wt%. The content of LiBF ₄ is ¹ to 90 parts by weight with respect to 100 parts by weight of the total amount of LiClO ₄ , LiR ¹ SO ₃ , and LiN (SO ₂ R ² ) (SO ₂ R ³ ) in the non-aqueous electrolyte. The lithium battery according to claim 1 or 2, wherein   The lithium battery according to claim 1, wherein the β-type manganese oxide has a crystallinity of 550 or more and 800 or less. 5. The lithium battery according to claim 1, wherein the mixed crystal state manganese oxide has a specific surface area of 0.5 m ² / g or more and 7.0 m ² / g or less.   The lithium battery according to any one of claims 1 to 5, which is a coin-type battery.

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