JP4560056B2 - Non-aqueous electrolyte battery - Google Patents

Description

  The present invention relates to a primary battery and a secondary battery provided with a nonaqueous electrolyte containing a room temperature molten salt.

  At present, lithium primary batteries and lithium ion secondary batteries using an organic electrolytic solution in which a lithium salt is dissolved in an organic solvent as a non-aqueous electrolyte are frequently used as a memory backup or driving power source for portable devices. In these batteries, since the organic solvent is contained in the organic electrolyte, the vapor pressure tends to increase at high temperatures, and many of the organic solvents are flammable, so consideration must be given to increase safety. .

  In addition, in electric vehicles (EV), hybrid vehicles (HEV), large power storage batteries, and power tool batteries that require high output, even higher safety and high reliability at high temperatures. Therefore, it is necessary to further improve the safety of the nonaqueous electrolyte. On the other hand, high safety and long life capacitors are similarly required to have high safety electrolytes.

  Therefore, solid electrolytes made of inorganic solids and room temperature molten salts that are ionic melts that are liquid at room temperature have attracted attention as nonflammable nonaqueous electrolytes. For example, JP-A-4-349365 discloses a lithium battery using a room temperature molten salt.

However, a non-aqueous electrolyte containing a room temperature molten salt has a problem that a high current performance cannot be obtained because it has higher viscosity and lower conductivity than a non-aqueous electrolyte made of an organic electrolyte.
JP-A-4-349365 (Claims)

  An object of the present invention is to provide a nonaqueous electrolyte battery having improved high-temperature storage characteristics.

A nonaqueous electrolyte battery according to the present invention comprises a positive electrode,
A negative electrode,
It is characterized in that it comprises a non-aqueous electrolyte containing an ambient temperature molten salt containing an anion represented by ^- lithium ion and _{B [(OCO) 2] 2} .

  As described above in detail, according to the present invention, a nonaqueous electrolyte battery having improved high-temperature storage characteristics can be provided.

  First, a first embodiment of a nonaqueous electrolyte battery according to the present invention will be described.

The nonaqueous electrolyte battery according to the first embodiment is housed in a container, a positive electrode containing a positive electrode active material, a negative electrode contained in the container and containing a negative electrode active material, and housed in the container. And a non-aqueous electrolyte containing a room temperature molten salt containing lithium ions. Further, at least one of the positive electrode and the negative electrode has an average primary particle size of at least one selected from the group consisting of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles and SiO ₂ -containing particles. Includes metal oxide particles in the range of 100 nm.

  Furthermore, in the nonaqueous electrolyte battery of the first embodiment, a separator can be interposed between the positive electrode and the negative electrode.

  Hereinafter, the metal oxide particles, the positive electrode, the negative electrode, the nonaqueous electrolyte, the separator, and the container will be described.

1) Metal oxide particles The metal oxide particles comprise at least one selected from the group consisting of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles, and SiO ₂ -containing particles.

  The metal oxide particles are contained in at least one of the positive electrode and the negative electrode, and the average primary particle diameter of the metal oxide particles may be in the range of 1 to 100 nm for the reason described below. desirable. If the average primary particle diameter exceeds 100 nm, the active material particles will not be uniformly dispersed on the surface, so that the wettability of the active material particles to room temperature molten salt may be reduced, and high current performance may not be obtained. The smaller the average primary particle diameter, the easier it is to uniformly disperse on the surface of the active material particles. However, when the average primary particle diameter is less than 1 nm, the affinity of the metal oxide particles to the room temperature molten salt decreases. There is a possibility that the wettability to room temperature molten salt may not be improved. A more preferable range of the average primary particle diameter is 1 to 50 nm, and a more preferable range is 1 to 20 nm.

When a functional group having polarity such as hexamethyldisilazane is bonded to the surfaces of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles and SiO ₂ -containing particles, the wettability of the electrode to room temperature molten salt is further increased. Therefore, it is preferable.

2) Positive electrode Examples of the positive electrode active material include various oxides, sulfides, conductive polymer materials such as polyaniline and polypyrrole, disulfide polymer materials, inorganic materials such as sulfur (S), and carbon fluoride. Organic materials etc. are mentioned. As the positive electrode active material, one type of material may be used alone, or two or more types of materials may be mixed and used.

Specific examples of the oxide include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ , Li _x MnO ₂ ), lithium nickel composite oxide ( For example, Li _x NiO ₂ ), lithium cobalt composite oxide (eg, Li _x CoO ₂ ), lithium nickel cobalt composite oxide (eg, LiNi _1-y Co _y O ₂ ), lithium manganese cobalt composite oxide (eg, LiMn _y Co _{1). -y} O _2), spinel type lithium-manganese-nickel composite oxide (e.g., _{Li x Mn 2-y Ni y} O 4), lithium phosphates having an olivine structure (e.g., _{Li x FePO 4, Li x Fe} 1-y Mn _y PO ₄ , Li _x CoPO _4, etc.), vanadium oxide (eg, V ₂ O ₅ ) And the like. On the other hand, specific examples of sulfides include iron sulfate (for example, Fe ₂ (SO ₄ ) ₃ ).

The positive electrode active material of the secondary battery is preferably a lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ ), a lithium nickel composite oxide (for example, Li _x NiO ₂ ), a lithium cobalt composite oxide ( For example, Li _x CoO ₂ ), lithium nickel cobalt composite oxide (eg, Li _x Ni _1-y Co _y O ₂ ), spinel-type lithium manganese nickel composite oxide (eg, Li _x Mn _2-y Ni _y O ₄ ), lithium Manganese cobalt composite oxide (for example, Li _x Mn _y Co _1-y O ₂ ), lithium iron phosphate (for example, Li _x FePO ₄ ), and the like. X and y are preferably 1 or less (including 0).

  On the other hand, manganese dioxide, iron oxide, copper oxide, iron sulfide, carbon fluoride and the like are preferable as the positive electrode active material of the primary battery.

  The average particle diameter of the positive electrode active material particles is preferably in the range of 1 to 100 μm, and more preferably in the range of 2 to 30 μm.

When the metal oxide particles described above are added to the positive electrode, the particle diameter ratio (d / D ₁ ) of the average primary particle diameter d (nm) of the metal oxide particles to the average particle diameter D ₁ (nm) of the positive electrode active material particles. Is preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻¹ . This is due to the reason explained below. If the particle size ratio (d / D ₁ ) is less than 1 × 10 ⁻⁵ , the dispersibility of the metal oxide particles on the surface of the positive electrode active material particles or the affinity of the metal oxide particles for the room temperature molten salt may be reduced. is there. On the other hand, when the particle size ratio (d / D ₁ ) exceeds 1 × 10 ⁻¹ , the surface of the metal oxide particles rather than the positive electrode active material particles may get wet with the non-aqueous electrolyte, and the active material utilization rate of the positive electrode may decrease. There is. A more preferable range of the particle size ratio (d / D ₁ ) is 1 × 10 ⁻⁴ to 1 × 10 ⁻² .

  When the metal oxide particles described above are added to the positive electrode, the content of the metal oxide particles in the positive electrode is desirably 10% by weight or less, and a more preferable range is 0.1 to 5% by weight. This is because if the content is large, the battery capacity may decrease, whereas if the content is small, the large current performance and the low-temperature discharge performance may be significantly decreased.

  In the positive electrode, for example, in addition to the positive electrode active material, the conductive agent, and the binder, the metal oxide particles are suspended in an appropriate solvent as required, and the resulting suspension is collected into a current collector such as an aluminum foil. It is produced by applying to the body, drying, and pressing.

  Examples of the conductive agent include acetylene black, carbon black, and graphite.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

  The compounding ratio of the positive electrode active material, the metal oxide particles, the conductive agent and the binder is 80 to 95% by weight of the positive electrode active material, 10% by weight or less (including 0% by weight) of the metal oxide particles, and the conductive agent. It is preferable that the content is 3 to 20% by weight and the binder is in the range of 2 to 7% by weight.

3) Negative electrode As the negative electrode active material, a material that absorbs and releases lithium is preferably used. Examples thereof include lithium metal, lithium alloy, carbonaceous material, and metal compound. As the negative electrode, one type of negative electrode active material may be used, or two or more types of negative electrode active materials may be mixed and used.

  Examples of the lithium alloy include a lithium aluminum alloy, a lithium zinc alloy, a lithium magnesium alloy, a lithium silicon alloy, and a lithium lead alloy.

Examples of the carbonaceous material that absorbs and releases lithium include natural graphite, artificial graphite, coke, vapor grown carbon fiber, mesophase pitch carbon fiber, spherical carbon, and resin-fired carbon. Among these, vapor growth carbon fiber, mesophase pitch carbon fiber, and spherical carbon are preferable. The carbonaceous material preferably has a (002) plane spacing d ₀₀₂ of 0.34 nm or less by X-ray diffraction.

Examples of the metal compound include metal oxides, metal sulfides, and metal nitrides. Specific examples of the metal oxide include lithium titanate (Li _{4 + x} Ti ₅ O ₁₂ ), tungsten oxide (WO ₃ ), amorphous tin oxide (eg, SnB _0.4 P _0.6 O _3.1 ), tin silicon Examples thereof include oxide (SnSiO ₃ ) and silicon oxide (SiO). Specific examples of metal sulfides include lithium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), iron sulfide (eg, FeS, FeS ₂ , Li _x FeS ₂ ) and the like. Specific examples of the metal nitride include lithium cobalt nitride (for example, Li _x Co _y N, 0 <x <4, 0 <y <0.5).

  When lithium or lithium alloy is used as the negative electrode active material, lithium foil or lithium alloy foil can be used as an electrode as it is. When lithium foil or lithium alloy foil is used as the negative electrode, the metal oxide particles are contained only in the positive electrode.

  Moreover, when using a lithium alloy, a carbonaceous material, or a metal compound as a negative electrode active material, the thing of a granular form can be used as a negative electrode active material. In this case, it is desirable to add metal oxide particles to the negative electrode.

  The average particle size of the negative electrode active material particles is preferably in the range of 0.1 to 100 μm, and more preferably in the range of 1 to 50 μm.

When the above-described metal oxide particles are contained in the negative electrode, the particle diameter ratio (d / D ₂ ) of the average primary particle diameter d (nm) of the metal oxide particles to the average particle diameter D ₂ (nm) of the negative electrode active material particles Is preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻¹ . This is due to the reason explained below. If the particle size ratio (d / D ₂ ) is less than 1 × 10 ⁻⁵ , the dispersibility of the metal oxide particles on the surface of the negative electrode active material particles or the affinity of the metal oxide particles for the room temperature molten salt may be reduced. is there. On the other hand, when the particle size ratio (d / D ₂ ) exceeds 1 × 10 ⁻¹ , the surface of the metal oxide particles rather than the negative electrode active material particles may get wet with the non-aqueous electrolyte, and the active material utilization rate of the negative electrode may decrease. There is. A more preferable range of the particle size ratio (d / D ₂ ) is 1 × 10 ⁻⁴ to 1 × 10 ⁻² .

  When the metal oxide particles described above are contained in the negative electrode, the content of the metal oxide particles in the negative electrode is desirably 10% by weight or less, and a more preferable range is 0.1 to 5% by weight. This is because if the content is large, the battery capacity may decrease, whereas if the content is small, the large current performance and the low-temperature discharge performance may be significantly decreased.

  In the case of using a negative electrode active material in a granular form, for example, the negative electrode is obtained by suspending metal oxide particles in an appropriate solvent, if necessary, in addition to the negative electrode active material particles and the binder. An object is applied to a metal current collector such as a copper foil, dried, and then pressed. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, and styrene butadiene rubber. Further, the negative electrode may further contain a conductive agent such as acetylene black, carbon black, graphite, and metal powder.

  The compounding ratio of the negative electrode active material, the metal oxide particles, the conductive agent and the binder is 80 to 98% by weight of the negative electrode active material, 10% by weight or less (including 0% by weight) of the metal oxide particles, and the conductive agent. It is preferable to be 20% by weight or less (including 0% by weight) and the binder is in the range of 2 to 7% by weight.

4) Non-aqueous electrolyte The non-aqueous electrolyte is desirably a liquid non-aqueous electrolyte substantially formed from a room temperature molten salt containing lithium ions. A non-aqueous electrolyte battery including such a liquid non-aqueous electrolyte can increase safety.

  The term “normal temperature molten salt” as used herein means a salt that is at least partially liquid in the operating temperature range (−40 ° C. to 100 ° C.) of the nonaqueous electrolyte battery. Among them, it is preferable to use a salt that is at least partially liquid around room temperature (preferably -20 ° C to 60 ° C).

  The room temperature molten salt is preferably an ionic melt composed of lithium ions, organic cations, and anions.

The organic cation is preferably an organic cation having a skeleton represented by the following chemical formula 2, and among them, alkyl imidazolium ions and quaternary ammonium ions are preferable.

Examples of the alkyl imidazolium ions include dialkyl imidazolium ions and trialkyl imidazolium ions. As the dialkylimidazolium ion, 1-methyl-3-ethylimidazolium ion (MEI ⁺ ) is preferable. On the other hand, as the trialkylimidazolium ion, 1,2-diethyl-3-propylimidazolium ion (DMPI ⁺ ) is preferable.

  Examples of the quaternary ammonium ions include tetraalkylammonium ions and cyclic ammonium ions. As the tetraalkylammonium ion, dimethylethylmethoxyammonium ion and trimethylpropylammonium ion are preferable.

  The melting point of the room temperature molten salt is preferably 100 ° C. or lower, more preferably 20 ° C. or lower, and still more preferably 0 ° C. or lower. By using at least one of alkyl imidazolium ions and quaternary ammonium ions as the organic cation, the melting point of the room temperature molten salt can be made 100 ° C. or lower or 20 ° C. or lower, and the reactivity between the nonaqueous electrolyte and the negative electrode Can be lowered.

  The concentration of lithium ions in the room temperature molten salt is preferably 20 mol% or less. By setting it in the above range, the molten salt at room temperature can be kept in a stable liquid form at a low temperature of 20 ° C. or lower. Further, since the room temperature molten salt can maintain a low viscosity even at room temperature or lower, the ionic conductivity of the nonaqueous electrolyte can be increased. A more preferable range is 1 to 10 mol%.

Examples of the anion include BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ²⁻ , and N (CF ₃ SO ₂ ) _{2. ^{-, N (C 2 F 5}} SO 2) 2 - and _{(CF 3 SO 2) 3 C} - is preferably used at least one selected from the group consisting of. By allowing a plurality of anions to coexist, a room temperature molten salt having a melting point of 20 ° C. or lower or 0 ° C. or lower can be easily formed. More preferable anions include BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ²⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , and N (C ₂ F ₅ SO ₂ ). ^{_{2 -, (CF 3 SO 2}} ) 3 C - and the like.

5) Separator As the separator, for example, a synthetic resin nonwoven fabric, a polyethylene porous film, a polypropylene porous film, or the like can be used.

6) Container As the container, a metal container or a laminate film container can be used.

  As the metal container, for example, a rectangular or cylindrical metal can can be used. Examples of the material for forming the metal container include aluminum, aluminum alloy, iron, and stainless steel. The wall thickness of the metal container is preferably 0.5 mm or less, and more preferably 0.2 mm or less.

  Examples of the laminate film include a laminated film including a metal foil and a resin film. The resin film can be formed of a polymer such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET), for example. The thickness of the laminate film is desirably 0.2 mm or less.

The nonaqueous electrolyte battery according to the present invention described above includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a nonaqueous electrolyte containing a room temperature molten salt containing lithium ions. Because
At least one of the positive electrode and the negative electrode has an average primary particle diameter of 1 to 100 nm made of at least one selected from the group consisting of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles and SiO ₂ -containing particles. It is characterized by including metal oxide particles within the range.

  In such a configuration, at least one of the positive electrode and the negative electrode can uniformly disperse the metal oxide particles having a high affinity for the room temperature molten salt on the surface of the active material particles, so that the wetness to the non-aqueous electrolyte is increased. Can be improved. As a result, in at least one of the positive electrode and the negative electrode, the amount of nonaqueous electrolyte retained can be increased, and the active material utilization rate can be improved. Therefore, the high current performance and low temperature performance of the nonaqueous electrolyte can be improved. Can be improved. As a result, it is possible to realize a nonaqueous electrolyte battery that includes a nonaqueous electrolyte containing a room temperature molten salt, has high safety, and is excellent in large current performance and low temperature performance.

  In particular, by including the metal oxide particles described above in both the positive electrode and the negative electrode, it is possible to improve the active material utilization rate of both the positive electrode and the negative electrode. The large current performance and low temperature performance of the electrolyte battery can be further improved.

In the electrode containing metal oxide particles, the particle size ratio (d / D) of the average primary particle diameter d (nm) to the average particle diameter D (nm) of the active material particles is 1 × 10 ⁻⁵ to 1 Since the dispersibility of the metal oxide particles and the affinity of the metal oxide particles with respect to the room temperature molten salt can be further improved by being within the range of × 10 ⁻¹ , the large current performance and low temperature of the nonaqueous electrolyte battery can be improved. The performance can be further improved.

  Next, a second embodiment of the nonaqueous electrolyte battery according to the present invention will be described.

The nonaqueous electrolyte battery according to the second embodiment includes a container, a positive electrode housed in the container, a negative electrode housed in the container, a lithium ion and B [(OCO) contained in the container. _{2] 2} ^- and a non-aqueous electrolyte containing an ambient temperature molten salt containing an anion represented by.

  In the nonaqueous electrolyte battery of the second embodiment, a separator can be interposed between the positive electrode and the negative electrode. As this separator, the thing similar to what was demonstrated in 1st Embodiment mentioned above can be mentioned.

  Hereinafter, the positive electrode, the negative electrode, and the nonaqueous electrolyte will be described. In addition, the thing similar to what was demonstrated in 1st Embodiment mentioned above can be used for a container.

A) Positive electrode Examples of the positive electrode active material include various oxides, sulfides, conductive polymer materials such as polyaniline and polypyrrole, disulfide polymer materials, inorganic materials such as sulfur (S), and carbon fluoride. Organic materials etc. are mentioned. As the positive electrode active material, one type of material may be used alone, or two or more types of materials may be mixed and used.

  Specific examples of the oxide and sulfide include the same as those described in the first embodiment.

  Examples of the preferable positive electrode active material for secondary battery and the preferable positive electrode active material for primary battery include the same materials as those described in the first embodiment.

  For example, the positive electrode is obtained by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, applying the obtained suspension to a current collector such as an aluminum foil, drying, and then pressing. Produced.

  Examples of the conductive agent and the binder include the same as those described in the first embodiment.

  The compounding ratio of the positive electrode active material, the conductive agent and the binder is preferably 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder. .

This positive electrode contains metal oxide particles having an average primary particle diameter of 1 to 100 nm consisting of at least one selected from the group consisting of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles and SiO ₂ -containing particles. You may let them. Thereby, a nonaqueous electrolyte battery excellent in high temperature storage characteristics, large current characteristics and low temperature characteristics can be realized.

B) Negative electrode As the negative electrode active material, a material that absorbs and releases lithium is preferably used, and examples thereof include lithium metal, lithium alloy, carbonaceous material, and metal compound. As the negative electrode, one type of negative electrode active material may be used, or two or more types of negative electrode active materials may be mixed and used.

  Examples of the lithium alloy, the carbonaceous material that absorbs and releases lithium, and the metal compound include the same materials as those described in the first embodiment.

  When lithium or lithium alloy is used as the negative electrode active material, lithium foil or lithium alloy foil can be used as an electrode as it is. Moreover, when using a lithium alloy, a carbonaceous material, or a metal compound as a negative electrode active material, a powdery active material can be used.

  The negative electrode containing a powdered active material is prepared by, for example, suspending the negative electrode active material powder and a binder in an appropriate solvent, and applying the obtained suspension to a metal current collector such as a copper foil, followed by drying. Thereafter, it is manufactured by pressing. Examples of the binder include those similar to those described in the first embodiment. Further, the negative electrode may further contain a conductive agent such as acetylene black, carbon black, graphite, and metal powder.

  The compounding ratio of the negative electrode active material, the conductive agent and the binder is 80 to 98% by weight of the negative electrode active material, 20% by weight or less (including 0% by weight) of the conductive agent, and 2 to 7% by weight of the binder. It is preferable to make it into a range.

This negative electrode contains metal oxide particles having an average primary particle diameter of 1 to 100 nm consisting of at least one selected from the group consisting of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles and SiO ₂ -containing particles. You may let them. Thereby, a nonaqueous electrolyte battery excellent in high temperature storage characteristics, large current characteristics and low temperature characteristics can be realized.

C) a non-aqueous electrolyte The non-aqueous electrolyte lithium ions and _{B [(OCO) 2] 2} - It is desirable that a liquid nonaqueous electrolyte is substantially formed from a room temperature molten salt containing the anion represented . The structural formula of an anion represented by B [(OCO) ₂ ] ₂ ^— is shown in the following chemical formula 3.

  The term “normal temperature molten salt” as used herein means a salt that is at least partially liquid in the operating temperature range (−40 ° C. to 100 ° C.) of the nonaqueous electrolyte battery. Among them, it is preferable to use a salt that is at least partially liquid around room temperature (preferably -20 ° C to 60 ° C).

  The melting point of the room temperature molten salt is preferably 100 ° C. or lower, more preferably 20 ° C. or lower, and still more preferably 0 ° C. or lower.

  The room temperature molten salt preferably further contains an organic cation. As this organic cation, the same thing as what was demonstrated in 1st Embodiment mentioned above can be mentioned.

The concentration of B [(OCO) ₂ ] ₂ ^{− in} the room temperature molten salt is preferably 50 mol% or less. _{This, B [(OCO) 2]} 2 - concentration is more than 50 mol%, there is a fear of causing the ionic conductivity decreases the melting point raised or non-aqueous electrolyte of the ionic liquid. A more preferable concentration range is 5 to 25 mol%. By setting it within this range, the molten salt at room temperature can be kept stable at a low temperature of 20 ° C. or lower. Moreover, since the normal temperature molten salt can maintain a low viscosity in an atmosphere at or below normal temperature, the ionic conductivity of the nonaqueous electrolyte can be increased.

The room temperature molten salt may contain an anion other than the anion represented by B [(OCO) ₂ ] ₂ ^— (hereinafter referred to as a second anion). Examples of the second anion include BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ²⁻ , N (CF _{3 ^{SO 2) 2 -, N (}} C 2 F 5 SO 2) 2 - and _{(CF 3 SO 2) 3 C} - is at least a kind of anion selected from the group consisting preferred. By including this second anion in the room temperature molten salt, the melting point of the room temperature molten salt can be lowered, so that a room temperature molten salt having a melting point of 20 ° C. or lower or 0 ° C. or lower can be easily obtained. In addition, since the second anion has a smaller ionic radius than the anion represented by B [(OCO) ₂ ] ₂ ^— , the ionic conductivity of the nonaqueous electrolyte can be increased. Among the second anions, more preferred anions include BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ²⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , N (C ^{_{2 F 5 SO 2) 2 -}} , (CF 3 SO 2) 3 C - and the like.

Only the anion represented by B [(OCO) ₂ ] ₂ ^— may be used as the anion component of the room temperature molten salt, but when the second anion is used in combination, the second anion in the anion component The ratio is desirably 80 mol% or less.

As described in the second embodiment above, another nonaqueous electrolyte battery according to the present invention includes a positive electrode, a negative electrode, lithium ions, and an anion represented by B [(OCO) ₂ ] ₂ ^−. And a nonaqueous electrolyte containing a room temperature molten salt. According to the present invention, it is possible to suppress a decrease in discharge capacity during high-temperature storage.

  That is, various negative electrode materials such as lithium metal, lithium alloy, carbon material, metal compound, etc. are easily subjected to electrochemical reduction and decomposition of organic cations contained in the non-aqueous electrolyte room temperature molten salt, which is provided with the room temperature molten salt. This is one of the factors that hinder the practical application of non-aqueous electrolyte batteries.

The present inventors have results of extensive studies, the lithium _{ion, B [(OCO) 2]} 2 - and an anion represented by the room temperature molten salt containing a organic cation liquid in the battery operating temperature range When this non-aqueous electrolyte containing a room temperature molten salt is used for a primary battery or a secondary battery, reductive decomposition of the non-aqueous electrolyte by the negative electrode can be suppressed, and a decrease in capacity during high-temperature storage can be suppressed. I found it. Furthermore, in the case of the secondary battery, it was also found that the charge / discharge cycle life can be improved. _{They, B [(OCO) 2]} 2 - anions represented by is partially reductive decomposition on the negative electrode, the negative electrode surface, Li permeable good quality coatings to suppress reductive decomposition of the nonaqueous electrolyte is formed This is considered to be because of this.

Moreover, since the anion represented by B [(OCO) ₂ ] ₂ ^— does not contain a fluorine atom, the thermal stability of the non-aqueous electrolyte is increased to improve the safety of the non-aqueous electrolyte battery. In addition, it is possible to realize a lithium battery with a low environmental impact.

At least one of the positive electrode and the negative electrode has an average primary particle diameter of at least one selected from the group consisting of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles and SiO ₂ -containing particles in the range of 1 to 100 nm. Since the active material utilization rate of the electrode can be improved by including the metal oxide particles, a nonaqueous electrolyte battery excellent in high-temperature storage characteristics, large current characteristics, and low-temperature discharge characteristics can be realized.

[Example]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1
<Preparation of positive electrode>
Lithium cobalt oxide (LiCoO ₂ ) particles having an average particle diameter D ₁ of 3 μm (3000 nm) are used as the positive electrode active material, and 1 wt% of Al ₂ O ₃ particles having an average primary particle diameter d of 20 nm with respect to the entire positive electrode. %, 8% by weight graphite powder with respect to the whole positive electrode as a conductive material, and 5% by weight PVdF with respect to the whole positive electrode as a binder, respectively, and dispersed in an n-methylpyrrolidone (NMP) solvent. A slurry was prepared. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and a positive electrode having an electrode density of 3.3 g / cm ³ was obtained through a pressing process.

<Production of negative electrode>
Lithium titanate (Li ₄ Ti ₅ O ₁₂ ) particles having an average particle diameter D ₂ of 1 μm (1000 nm), Al ₂ O ₃ particles having an average primary particle diameter d of 20 nm, acetylene black as a conductive material, and a binder N-methylpyrrolidone (NMP) solvent by blending PVdF as a weight ratio (Li ₄ Ti ₅ O ₁₂ : Al ₂ O ₃ particles: conductive material: binder) to be 88: 1: 5: 6 To prepare a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and a negative electrode having an electrode density of 2 g / cm ³ was obtained through a pressing process.

  In addition, the measurement of a positive electrode active material particle, a negative electrode active material particle, and a metal oxide particle was performed by the method demonstrated below.

  Using a laser diffraction particle size distribution analyzer (Shimadzu SALD-300), first add about 0.1 g of a sample, a surfactant, and 1 to 2 mL of distilled water to a beaker and stir well. The light intensity distribution was measured 64 times at intervals of 2 seconds, and the particle size distribution data was analyzed.

Further, the particle diameter ratio (d / D ₁ ) of the average primary particle diameter d (nm) to the average particle diameter D ₁ (nm) of the positive electrode active material particles and the average particle diameter D ₂ (nm) of the negative electrode active material particles The particle size ratio (d / D ₂ ) of the average primary particle size d (nm) is shown in Table 1 below.

<Preparation of non-aqueous electrolyte>
The molar ratio of 1-methyl-3-ethylimidazolium ion (MEI ⁺ ), Li ⁺ , CF ₃ SO ₃ ⁻ and BF ₄ ⁻ is MEI ⁺ : Li ⁺ : CF ₃ SO ₃ ⁻ : BF ₄ ^−. = 45: 5: 20: 30 was mixed, and a liquid room temperature molten salt was obtained at 20 ° C.

  After impregnating the polyethylene porous film of the separator with this room temperature molten salt, the surface of the positive electrode was covered with this separator. The negative electrode was stacked so as to face the positive electrode with a separator interposed therebetween, and these were wound in a spiral shape, and then pressed into a flat shape to obtain a flat electrode group. An electrode group is housed in a container made of an aluminum layer-containing laminate film having a wall thickness of 0.1 mm, and has the structure shown in FIG. 1 and is a thin non-water having a thickness of 3 mm, a width of 35 mm, and a height of 62 mm. An electrolyte secondary battery was produced.

  As shown in FIG. 1, the flat electrode group 1 has a structure in which a positive electrode 2 and a negative electrode 3 are flattened with a separator 4 interposed therebetween. The strip-like positive electrode terminal 5 is electrically connected to the positive electrode 2. On the other hand, the strip-like negative electrode terminal 6 is electrically connected to the negative electrode 3. The electrode group 1 is housed in a laminate film container 7 with the ends of the positive electrode terminal 5 and the negative electrode terminal 6 extended from the container 7. The laminated film container 7 is sealed by heat sealing.

(Examples 2-9)
Table 1 below shows the types, average primary particle size, blending amount, particle size ratio (d / D ₁ ) and particle size ratio (d / D ₂ ) of the metal oxide particles added to both the positive electrode and the negative electrode. A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 1 was assembled except that the setting was set to.

(Comparative Example 1)
A thin nonaqueous electrolyte secondary battery having the same configuration as described in Example 1 was assembled except that the metal oxide particles were not added to both the positive electrode and the negative electrode.

(Comparative Example 2)
Table 1 below shows the types, average primary particle size, blending amount, particle size ratio (d / D ₁ ) and particle size ratio (d / D ₂ ) of the metal oxide particles added to both the positive electrode and the negative electrode. A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 1 was assembled except that the setting was set to.

About the obtained non-aqueous electrolyte secondary battery of Examples 1-9 and Comparative Examples 1-2, after charging to 3V with a constant current of 100 mA, a charge / discharge cycle for carrying out a constant current discharge of 100 mA to 1.5V was performed. Repeated at ° C. Table 1 below shows the initial discharge capacity and the capacity retention ratio during 1 A discharge (capacity retention ratio when 100 mA discharge is 100).

As is clear from Table 1, metal oxide particles having an average primary particle diameter of 1 to 100 nm consisting of at least one selected from the group consisting of Al ₂ O ₃ -containing particles, ZrO ₂ -containing particles and SiO ₂ -containing particles. The secondary batteries of Examples 1 to 9 including the positive electrode and the negative electrode included were compared with the secondary battery of Comparative Example 1 with no metal oxide added and the secondary battery of Comparative Example 2 with an average primary particle diameter exceeding 100 nm. Thus, it can be understood that the discharge capacity is high and the large current discharge characteristics are excellent.

(Example 10)
A thin nonaqueous electrolyte primary battery was produced in the same manner as described in Example 1 except that manganese dioxide particles having an average particle diameter D ₁ of 5 μm (5000 nm) were used as the positive electrode active material particles.

(Comparative Example 3)
A thin nonaqueous electrolyte primary battery was produced in the same manner as described in Comparative Example 1 except that manganese dioxide particles having an average particle diameter D ₁ of 5 μm (5000 nm) were used as the positive electrode active material particles.

Each of the nonaqueous electrolyte primary batteries of Example 10 and Comparative Example 3 was divided into two, one of which was subjected to a discharge test at 500 mA, and the obtained discharge capacity is shown in Table 2 below. The other was subjected to a discharge test at 1000 mA, and the obtained discharge capacity is shown in Table 2 below, assuming that the discharge capacity at 500 mA is 100%.

  As is clear from Table 2, it can be seen that the primary battery of Example 10 can obtain a higher capacity than Comparative Example 3 during large current discharge.

(Example 11)
<Preparation of positive electrode>
LiFePO ₄ particles are used as a positive electrode active material, and graphite powder is used as a conductive material in a proportion of 8% by weight with respect to the whole positive electrode, and PVdF is used as a binder at 5% by weight with respect to the whole positive electrode. Were blended and dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and a positive electrode having an electrode density of 3.3 g / cm ³ was obtained through a pressing process.

<Production of negative electrode>
A lithium aluminum alloy (aluminum content in the alloy was 3 atomic%) foil was prepared as a negative electrode.

<Preparation of non-aqueous electrolyte>
A molar ratio (MEI ⁺ ) of 1-methyl-3-ethylimidazolium ion (hereinafter referred to as MEI ⁺ ), Li ⁺ , B [(OCO) ₂ ] ₂ ⁻ and BF ₄ ⁻ as the second anion. : Li ⁺ : B [(OCO) ₂ ] ₂ ⁻ : BF ₄ ⁻ ) was mixed at 42: 8: 8: 42 to obtain a room temperature molten salt which was liquid at 20 ° C.

  After impregnating the polyethylene porous film of the separator with this room temperature molten salt, the surface of the positive electrode was covered with this separator. The negative electrode was stacked so as to face the positive electrode with a separator interposed therebetween, and these were wound in a spiral shape, and then pressed into a flat shape to obtain a flat electrode group. The electrode group is housed in a container made of an aluminum layer-containing laminate film having a wall thickness of 0.1 mm, and has the structure shown in FIG. 1 described above, and is thin with a thickness of 3 mm, a width of 35 mm, and a height of 62 mm. A non-aqueous electrolyte secondary battery was produced.

(Examples 12 to 13)
A thin nonaqueous electrolyte secondary battery having the same configuration as described in Example 11 was assembled except that the type of the second anion was changed as shown in Table 3 below.

(Example 14)
MEI ⁺ , Li ⁺ , B [(OCO) ₂ ] ₂ ⁻ and BF ₄ ⁻ as the second anion are in a molar ratio (MEI ⁺ : Li ⁺ : B [(OCO) ₂ ] ₂ ⁻ : BF ₄ ^- ) Was mixed at 42: 8: 20: 30 to obtain a room temperature molten salt that was liquid at 20 ° C.

  A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 11 was assembled except that this room temperature molten salt was used.

(Example 15)
MEI ⁺ , Li ⁺ , B [(OCO) ₂ ] ₂ ⁻ and BF ₄ ⁻ as the second anion are in a molar ratio (MEI ⁺ : Li ⁺ : B [(OCO) ₂ ] ₂ ⁻ : BF ₄ ^- ) Was mixed so as to be 46: 4: 4: 46 to obtain a room temperature molten salt which was liquid at 20 ° C.

  A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 11 was assembled except that this room temperature molten salt was used.

(Example 16)
A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 11 was assembled except that an aluminum metal foil (purity 99.99%) having a thickness of 100 μm was used as the negative electrode.

(Example 17)
85:10: lithium titanate (Li ₄ Ti ₅ O ₁₂ ) particles, acetylene black as a conductive material, and PVdF as a binder in a weight ratio (Li ₄ Ti ₅ O ₁₂ : conductive material: binder) 5 and these were dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and a negative electrode having an electrode density of 2 g / cm ³ was obtained through a pressing process.

  A thin nonaqueous electrolyte secondary battery having the same structure as that described in Example 11 was assembled except that this negative electrode was used.

(Examples 18 to 20)
The type of cation was changed as shown in Table 3 below, and the molar ratio of cation, Li ⁺ , B [(OCO) ₂ ] ₂ ⁻ and BF ₄ ⁻ (cation: Li ⁺ : B [(OCO) ₂ ]) _{2 ^-:} BF 4 ^-) is 42: 8: 20: except that mixed so that 30 were assembled thin nonaqueous electrolyte secondary battery of the same structure as that described in example 11 described above. In Table 3, DMPI ⁺ represents 1,2-diethyl-3-propylimidazolium ion.

(Example 21)
LiFePO ₄ particles are used as the positive electrode active material, and SiO ₂ particles having an average primary particle diameter of 20 nm are 1% by weight with respect to the whole positive electrode, and the ratio of 8% by weight as a conductive material with respect to the whole positive electrode. Thus, graphite powder and PVdF were blended so as to be 5% by weight with respect to the whole positive electrode as a binder, and these were dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and a positive electrode having an electrode density of 3.3 g / cm ³ was obtained through a pressing process.

  A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 11 was assembled except that this positive electrode was used.

(Comparative Example 4)
MEI ⁺ , Li ⁺ and BF ₄ ⁻ are mixed so that the molar ratio (MEI ⁺ : Li ⁺ : BF ₄ ⁻ ) is 42: 8: 50, and a room temperature molten salt which is liquid at 20 ° C. is obtained. It was.

  A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 11 was assembled except that this room temperature molten salt was used as a nonaqueous electrolyte.

(Comparative Example 5)
And MEI ^+, and _{^{Li +, N (CF 3 SO}} 2) 2 - and the molar ratio _{^{(MEI +: Li +: N}} (CF 3 SO 2) 2 -) is 42: 8: mixed such that the 50 A room temperature molten salt that is liquid at 20 ° C. was obtained.

  A thin nonaqueous electrolyte secondary battery having the same configuration as that described in Example 11 was assembled except that this room temperature molten salt was used as a nonaqueous electrolyte.

(Comparative Example 6)
A thin non-aqueous electrolyte having the same configuration as described in Example 11 above, except that the same type of nonaqueous electrolyte as used in Comparative Example 4 and the same type of negative electrode as used in Example 17 were used. A water electrolyte secondary battery was assembled.

  About the obtained nonaqueous electrolyte secondary battery of Examples 11-21 and Comparative Examples 4-6, the charging / discharging cycle on the charging / discharging conditions demonstrated below is performed at 20 degreeC, discharge initial capacity, and cycle life (discharge) The number of cycles in which the capacity was 80% of the initial capacity) was measured, and the results are shown in Table 3 below.

<Charging / discharging conditions>
For Examples 11 to 15, 18 to 20 and Comparative Examples 4 and 5 using lithium aluminum alloy foil as the negative electrode, after charging to 4 V with a constant current of 100 mA, a charge / discharge cycle in which constant current discharge of 100 mA to 3 V was performed gave.

  About Example 16 which uses aluminum metal foil as a negative electrode, after charging to 3.8V with a 100 mA constant current, the charging / discharging cycle which performs a 100 mA constant current discharge to 1.5V was given.

  About Example 17 and Comparative Example 6 which use lithium titanate as a negative electrode active material, after charging to 2.5V with a constant current of 100 mA, a charge / discharge cycle for performing a constant current discharge of 100 mA to 1.5V was performed.

Moreover, about the nonaqueous electrolyte secondary battery of Examples 11-21 and Comparative Examples 4-6, after charge, it stores at 85 degreeC for 20 days, and a residual capacity | capacitance is measured (it sets the discharge capacity before storage to 100%). The results are shown in Table 3 below.

As apparent from Table 3, the lithium ions and _{B [(OCO) 2] 2} - the secondary batteries of Examples 11 to 21 having a room temperature molten salt containing an anion represented by, B [(OCO ) _{2] 2} ^- as compared with the comparative example 4-6 with no additive, long cycle life, and it can be seen that high residual capacity at high temperature storage.

(Example 22)
A thin nonaqueous electrolyte primary battery was produced in the same manner as described in Example 11 except that manganese dioxide particles were used as the positive electrode active material particles.

(Comparative Example 7)
A thin nonaqueous electrolyte primary battery was produced in the same manner as described in Comparative Example 4 except that manganese dioxide particles were used as the positive electrode active material particles.

Each of the nonaqueous electrolyte primary batteries of Example 22 and Comparative Example 7 was divided into two parts, one of which was stored at a high temperature of 85 ° C. for 1000 hours and then subjected to a discharge test at 500 mA. For the other, a discharge test was performed at 500 mA without performing high-temperature storage, and the obtained battery capacity is shown in Table 4 below. Table 4 below shows the discharge capacity after high-temperature storage when the battery capacity is 100%, as the remaining rate during high-temperature storage.

  As can be seen from Table 4, it can be understood that the nonaqueous electrolyte primary battery of Example 22 is superior in capacity characteristics and long-term high-temperature storage characteristics as compared with Comparative Example 7.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a partially cutaway perspective view showing a thin non-aqueous electrolyte secondary battery of Example 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrode group, 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Separator, 5 ... Positive electrode terminal, 6 ... Negative electrode terminal, 7 ... Container.

Claims (4)

A positive electrode;
A negative electrode,
Lithium ions and _{B [(OCO) 2] 2} - nonaqueous electrolyte battery characterized by comprising a non-aqueous electrolyte containing an ambient temperature molten salt containing an anion represented by. The non-aqueous electrolyte battery according to claim 1, wherein the room temperature molten salt further contains an organic cation having a skeleton represented by Chemical Formula 1 below.

  3. The nonaqueous electrolyte battery according to claim 1, wherein the negative electrode active material is made of at least one selected from lithium metal, a lithium alloy, a carbonaceous material, and a metal compound.   The nonaqueous electrolyte battery according to claim 1, wherein the negative electrode active material is lithium titanate.

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