JP5303857B2 - Nonaqueous electrolyte battery and battery system - Google Patents

Description

  The present invention relates to a nonaqueous electrolyte battery excellent in safety during overcharge.

  In recent years, battery systems with large battery capacity and high output, such as for HEV (hybrid vehicles), have been actively developed. In addition, it has been studied to employ a nonaqueous electrolyte battery such as a lithium battery in such a battery system in place of the conventional nickel metal hydride battery.

  For example, as seen in Patent Documents 1 and 2, a number of technologies corresponding to overcharging of nonaqueous electrolyte batteries are disclosed. However, as can be seen from the descriptions in Patent Documents 1 to 3, the capacity of a small non-aqueous electrolyte battery for consumer use that has been conventionally used is about 1.5 Ah at most, and the level of rapid charging is less than 4 It at most. . However, for applications such as HEV, emergency, and power storage, non-aqueous electrolyte batteries with extremely large capacity and high output are used, so it is necessary to cope with usage conditions that have not been assumed in the past.

  For example, assuming a case where charging current continues to flow even though charging should be terminated due to a failure of the control system, etc., because the absolute amount of electrode material and electrolyte material stored in the unit cell is large, Combined with the heat storage effect, the battery falls into an extreme overcharged state with a sudden rise in battery voltage or battery temperature in a short time, and the safety of the battery system is impaired.

  For example, in HEV applications, if a downhill road continues and regeneration (charging) continues in the hybrid system, or if the battery is overcharged due to a failure in the control circuit of the battery system installed in the passenger car, the passenger car If the battery causes an internal short circuit due to an impact due to a collision accident, etc., when an operator tries to replace the battery that has been overcharged due to a failure in the control circuit of the emergency power system, the control circuit of the power storage system If it is assumed that the battery is overcharged due to a failure and suffers a disaster such as an earthquake, the safety cannot always be kept sufficiently.

  Therefore, there has been a demand for a battery or a battery system that can interrupt the charging current at an early stage so that the battery is not overcharged even if the control system fails.

Patent Document 1 includes a positive electrode in which 0.5 to 20% by weight of lithium carbonate is added to a positive electrode active material (LiCoO ₂ ), and has a diameter of 14 mm including a current interrupting unit that operates in response to an increase in battery internal pressure. , A non-aqueous electrolyte secondary battery having a 50 mm height is described, and “a battery that generates heat or a relatively rapid breakage due to a rapid temperature rise of the battery by being overcharged at a current of 1.5 A” is described. “The rate of occurrence of damaged products was investigated” (see paragraph 0032). “When lithium carbonate was added to the positive electrode mainly composed of lithium composite oxide, the battery internal pressure increased rapidly due to overcharge. Due to the fact that heat generation with temperature rise and relatively rapid damage do not occur and the battery internal pressure rises relatively slowly, the current interrupting means operates reliably and interrupts the charging current. Although it is not clear, since the lithium carbonate at the positive electrode is electrochemically decomposed to generate carbon dioxide, the carbon dioxide suppresses the abnormal reaction during overcharging in some way, and the generated carbon dioxide generates a current. It seems that in order to operate the shut-off means reliably, heat generation accompanied by a rapid temperature rise and comparatively rapid breakage are prevented "(see paragraph 0015).

Patent Document 2 describes a 18650-type non-aqueous rechargeable battery in which LiMn ₂ O ₄ is used as a positive electrode active material, spherical graphite is used as a negative electrode, and 2.5% by weight of biphenyl is added as an additive to an electrolyte. Was described as “overcharge testing was performed at an ambient temperature of 45 ° C. using a power supply capable of 3 amps at 10 volts” (see paragraph 0038). It can be seen that chlorothiophene and furan provide overcharge protection for certain battery systems without adversely affecting their cycle life characteristics "(see paragraph 0046). .

  Patent Document 3 discloses that for the purpose of “providing a secondary battery capable of obtaining a high energy density and improving charge / discharge cycle characteristics”, 95 parts by weight of lithium cobalt composite oxide powder. A positive electrode mixed with 5 parts by weight of lithium carbonate powder, a negative electrode using artificial graphite, and an electrolytic solution containing 0.1 to 15.8% by weight of 2,4-difluoroanisole (DFA) were used. In addition, a cylindrical secondary battery having a diameter of 14 mm and a height of 65 mm is described, and it is described that a charge / discharge cycle test was performed at a current of 400 mA (see Examples 2-12 to 2-16).

However, none of the documents describes a combination of mixing lithium carbonate with the positive electrode and selecting and adding biphenyl as an electrolytic solution additive.
JP-A-4-328278 JP-A-9-106835 International Publication No. 01/022519 Pamphlet

  It aims at providing the nonaqueous electrolyte battery excellent in the safety | security with respect to an overcharge.

The present invention provides a negative electrode, a positive electrode including a positive electrode mixture containing a compound capable of generating a gas at a positive electrode potential in an overcharged state, and a resistance film formed on the electrode surface in an overcharged state. A nonaqueous electrolyte battery in which a nonaqueous electrolyte containing biphenyl that promotes gas generation by flowing and generating heat is housed in an outer container.

  The nonaqueous electrolyte battery of the present invention is characterized in that it includes a current interrupting means that operates in response to an increase in internal pressure in the outer container.

  In addition, the present invention is a battery system including a battery unit including one or a plurality of the nonaqueous electrolyte batteries and a voltage monitoring and control unit.

  A nonaqueous electrolyte battery excellent in safety against overcharging can be provided.

  In the present invention, the positive electrode mixture contains a compound capable of generating gas at the positive electrode potential in an overcharged state, thereby generating a decomposition gas in response to rapid overcharge and exerting an effect of operating a current interruption mechanism. To do.

  Here, as a compound that can generate gas at the positive electrode potential in an overcharged state, an inorganic carbonate compound, an inorganic oxalate compound, or an inorganic nitrate compound is preferable, and an inorganic carbonate compound is particularly preferable. Examples of the inorganic carbonate compound include lithium carbonate.

  For example, a small amount of lithium carbonate is unavoidably present in the positive electrode active material powder such as lithium cobaltate. In order to achieve the above effect in the present invention, the amount of lithium carbonate in the positive electrode mixture is the unavoidable amount. It is necessary to contain more than. Specifically, the amount of lithium carbonate in the positive electrode mixture is preferably 1% by weight or more, more preferably 2% by weight or more, and most preferably 4% by weight or more. The amount of lithium carbonate contained in the positive electrode mixture is preferably 10% by weight or less because the possibility that the energy density of the battery is lowered can be reduced.

  In addition, the present invention provides a non-aqueous electrolyte containing biphenyls, and when rapid overcharge is initiated, the biphenyls are polymerized to form a resistance film on the electrode surface, thereby increasing the overcharge depth. The heat generated by the charging current flowing through the electrode on which the resistance film is formed promotes the decomposition of the lithium carbonate in the positive electrode mixture and the gas generation accompanying this, and synergistically accelerates the current interruption mechanism. The effect to act on is expressed. In this way, charging can be stopped at a stage where the overcharge depth of the battery is low. The amount of biphenyl contained in the non-aqueous electrolyte is preferably 2% by weight or more, because the above-described effect is surely exhibited. The amount of biphenyls contained in the non-aqueous electrolyte is preferably 10% by weight or less because the risk of increasing the internal resistance of the battery can be reduced, and more preferably 5% by weight or less.

  Here, biphenyls are not limited, and examples thereof include biphenyl or a compound having a structure in which part of hydrogen atoms constituting biphenyl is substituted with a fluorine atom.

  The positive electrode included in the nonaqueous electrolyte battery according to the present invention is not limited as long as the positive electrode mixture contains a compound capable of generating gas at the positive electrode potential in an overcharged state.

As the positive electrode active material, a known material can be used in a known formulation. For example, LiCoO ₂ , a lithium-containing transition metal oxide having a α-NaFeO ₂ structure in which a part of Co is substituted with Ni, Mn, or other transition metals or boron, and a spinel crystal structure represented by LiMn ₂ O ₄ compounds _with, can be used LiFePO _4, LiFeSO 4 or a part of the Fe is Co, Mn polyanionic compound substituted with the like or the like. The positive electrode further includes a group I metal compound such as CuO, Cu ₂ O, Ag ₂ O, CuS, and CuSO ₄ , a group IV metal compound such as TiS ₂ , SiO ₂ , and SnO, V ₂ O ₅ , V ₆ O ₁₂ , Group V metal compounds such as VOx, Nb ₂ O ₅ , Bi ₂ O ₃ , Sb ₂ O ₃ , Group VI metal compounds such as CrO ₃ , Cr ₂ O ₃ , MoO ₃ , MoS ₂ , WO ₃ , SeO ₂ , MnO ₂ , Group VII metal compounds such as Mn ₂ O ₃ , Group VIII metal compounds such as Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , FePO ₄ , Ni ₂ O ₃ , NiO, CoO ₃ , and CoO are added. May be. Furthermore, conductive polymer compounds such as disulfide, polypyrrole, polyaniline, polyparaphenylene, polyacetylene, and polyacene materials, pseudographite-structured carbonaceous materials, and the like may be used.

The negative electrode provided in the nonaqueous electrolyte battery according to the present invention is not limited in any way, and examples of the negative electrode active material include lithium titanate having a spinel crystal structure, lithium metal, lithium-aluminum, lithium-lead, lithium- Examples include lithium-containing alloys such as tin, lithium-aluminum-tin, lithium-gallium, and wood alloys, and the following carbon materials. For example, natural graphite, artificial graphite, amorphous carbon, fibrous carbon, powdered carbon, petroleum pitch-based carbon, and coal coke-based carbon. These carbon materials are preferably particles or fibers having a diameter or fiber diameter of 0.01 to 10 microns and a fiber length of several μm to several mm. In particular, the above carbon material is analyzed by X-ray diffraction or the like; lattice spacing (d002) 0.33 to 0.35 nm, crystallite size La20 nm or more in the a-axis direction, crystallite size Lc20 nm in the c-axis direction As described above, graphite having a true density of 2.00 to 2.25 g / cm ³ is preferable because it exhibits a high capacity. However, of course, it is not limited to these ranges.

  Further, it is possible to modify the carbon material by adding a metal oxide such as tin oxide or silicon oxide, or by adding phosphorus or boron. Moreover, it is also possible to insert lithium in advance into the carbonaceous material used in the present invention by using graphite and lithium metal, a lithium-containing alloy or the like in combination or by electrochemical reduction in advance.

  A conductive agent, a binder, a filler, and the like can be added to the positive electrode and the negative electrode as necessary in the electrode mixture. As the conductive agent, any electronic conductive material that does not adversely affect battery performance may be used. Usually, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber and metal (copper, nickel, aluminum, silver, gold, etc.) Conductive materials such as powders, metal fibers, and conductive ceramic materials can be included as one type or a mixture thereof. Among these, acetylene black is desirable from the viewpoints of conductivity and coatability. The addition amount is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, powder mixers such as V-type mixers, S-type mixers, crackers, ball mills, and planetary ball mills can be mixed dry or wet.

  As the binder, heat such as tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, carboxymethyl cellulose, etc. A plastic resin, a polymer having rubber elasticity, a polysaccharide, or the like can be used as one kind or a mixture of two or more kinds. In addition, it is desirable that a binder having a functional group that reacts with lithium, such as a polysaccharide, be deactivated by, for example, methylation. The addition amount is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight.

  As the filler, any material that does not adversely affect the battery performance may be used. Usually, olefin polymers such as polypropylene and polyethylene, aerosil, zeolite, glass, carbon and the like are used. The amount of filler added is preferably 0 to 30% by weight.

  Furthermore, chalcogen elements such as sulfur, selenium, and tellurium can be added for the purpose of increasing the capacity. The added chalcogen element is added to the S—S bond of the disulfide group of the electrode material, and gives further charge / discharge capacity. The amount of chalcogen element added is preferably 0 to 30% by weight.

  The current collector of the electrochemically active substance may be any electronic conductor that does not adversely affect the battery constructed. For example, as a positive electrode current collector, aluminum, titanium, stainless steel, nickel, calcined carbon, conductive polymer, conductive glass, etc., in addition to aluminum for the purpose of improving adhesiveness, conductivity, and oxidation resistance. A material obtained by treating the surface of copper or copper with carbon, nickel, titanium, silver or the like can be used. In addition to copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., the negative electrode current collector is adhesive, conductive, and oxidation resistant. For the purpose of improving the property, a material obtained by treating the surface of copper or the like with carbon, nickel, titanium, silver or the like can be used. The surface of these materials can be oxidized. As for these shapes, in addition to the foil shape, a film shape, a sheet shape, a net shape, a punched or expanded product, a lath body, a porous body, a foamed body, a formed body of a fiber group, and the like are used. The thickness is not particularly limited, but a thickness of 1 to 500 μm is used. Among these current collectors, an aluminum foil excellent in oxidation resistance is used for the positive electrode, and a copper foil, nickel foil, iron foil, which is inexpensive and stable in a reduction field and has excellent electrical conductivity, And the alloy foil containing those parts is preferable. Furthermore, it is desirable that the surface roughness of the rough surface with excellent adhesion between the electrochemically active material layer and the current collector is 0.2 μmRa or more. The electrolytic foil is excellent for the purpose of obtaining such a rough surface.

  As a battery exterior material using the electrode material of the present invention, a metal can such as iron, stainless steel, and aluminum can be used. From the viewpoint of weight energy density, a metal-resin composite of a metal foil and a resin film. Agents are preferred. As an example of the metal foil, any foil such as aluminum, iron, nickel, copper, SUS, titanium, gold, silver and the like having no pinhole may be used, but a lightweight and inexpensive aluminum foil is preferable. The resin film is preferably a resin film having excellent piercing strength such as a polyethylene terephthalate film or nylon film on the outer surface, and a thermoplastic and fusible film such as a polyethylene film or nylon film on the inner surface. From the viewpoint of solvent resistance, it is desirable to seal the opening of such a resin film with a thermoplastic resin.

  As separators for batteries using the electrode material of the present invention, polyolefin-based, polyester-based, polyacrylonitrile-based, polyphenylene sulfide-based, polyimide-based, and fluororesin-based microporous membranes and nonwoven fabrics can be used. Among them, it is necessary to treat the microporous film with poor wettability with a surfactant or the like.

  The porosity of the separator is preferably 98% by volume or less from the viewpoint of strength. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge / discharge characteristics.

The nonaqueous electrolyte used for the nonaqueous electrolyte battery according to the present invention is not limited as long as it contains biphenyls. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, chloroethylene carbonate and vinylene carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain carbonates such as dimethyl carbonate, ethylmethyl carbonate and diethyl carbonate Esters; chain esters such as methyl acetate and methyl butyrate; ethers such as tetrahydrofuran or derivatives thereof, 1,3-dioxane, 1,2-dimethoxyethane, and methyldiglyme; nitriles such as acetonitrile and benzonitrile; dioxalane or derivatives thereof; sulfolane, alone or their mixture of two or more solvents such as sultone or a derivative _{thereof, LiClO 4, LiBF 4, LiAsF} 6, LiPF _{, LiCF 3 SO 3, LiCF 3} CO 2, LiSCN, LiBr, LiI, Li 2 SO 4, Li 2 B 10 Cl 10, NaClO 4, NaI, NaSCN, NaBr, KClO 4, KSCN , etc. Li, Na or K, Inorganic ion salts containing one of LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NClO ₄ , (n-C ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, (C ₂ H ₅ ) ₄ N-benzoate, (C ₂ H ₅ ) Quaternary ammonium salt such as ₄ N-phthalate, lithium stearyl sulfonate, oct What mixed 1 type (s) or 2 or more types of organic ion salts, such as lithium tilsulfonate and lithium dodecylbenzenesulfonate, etc. can be used.

  The electrolytic solution can be injected after the separator of the present invention is sandwiched between electrodes and stacked or wound. As an injection method, it is possible to inject at normal pressure, but a vacuum impregnation method and a pressure impregnation method are also possible.

  As the non-aqueous electrolyte of the battery of the present invention, an ionic liquid or a lithium conductive solid electrolyte (at 20 to 60 ° C., which is solid or solid) can also be used. This solid electrolyte is composed of a polymer containing the salt. Examples of the polymer electrolyte containing these include a polyethylene oxide derivative in which the lithium salt is dissolved or a polymer containing at least the derivative, a polypropylene oxide derivative or a polymer containing at least the derivative, polyphosphazene or the derivative, and an ion dissociation group. Polymer matrix materials (gel electrolytes) and inorganic solid electrolytes containing non-aqueous electrolytes in polymers, phosphate ester polymer derivatives, polyvinyl pyridine derivatives, bisphenol A derivatives, polyacrylonitrile, polyvinylidene fluoride, fluororubber, etc. Those composed of an ion conductive compound are used.

Example 1
A positive electrode paste using N-methylpyrrolidone as a solvent was applied to both sides of a strip-shaped aluminum current collector, dried and pressed to prepare a positive electrode. Here, the positive electrode paste includes, in addition to the solvent, LiCo _0.33 Ni _0.33 Mn _0.33 O ₂ as a positive electrode active material, acetylene black as a conductive material, polyvinylidene fluoride as a binder, and carbonic acid. It contains lithium, and the mass ratio of the positive electrode active material, the conductive material, and the binder in terms of solid matter is 91: 5: 4, and the mass of lithium carbonate in the total solid matter to which lithium carbonate is added The ratio is 4%.

  A negative electrode paste containing N-methylpyrrolidone containing hard carbon as a negative electrode active material as a carbon material and polyvinylidene fluoride as a binder in a solid-converted mass ratio of 92: 8 as a solvent is made of a strip-like copper. It apply | coated on both surfaces of the electrical power collector, and after drying, it pressed and produced the negative electrode.

LiPF ₆ as an electrolyte salt was mixed at a concentration of 1 mol / liter in a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) were mixed at an equal volume ratio. As an additive, 2% by weight of biphenyl was added to prepare a nonaqueous electrolyte.

  As a separator, the strip positive electrode and the strip negative electrode are wound flatly through a strip-shaped polyethylene microporous membrane, and a pole group is prepared, accommodated in a rectangular battery case which is an exterior container, and the non-aqueous electrolyte is injected. The nonaqueous electrolyte battery having a design capacity of 6 Ah was manufactured through impregnation and an initial charge / discharge cycle process.

  In addition to the positive electrode terminal and the negative electrode terminal, the rectangular battery case cuts off the electrical connection between the electrode terminal provided in the battery case and the power generation element in the battery case when the internal pressure is in the range of 300 to 900 kPa. A current release means is provided, and further, a pressure release valve is provided that can exhaust the gas in the battery case to the outside when the internal pressure exceeds 900 kPa. The positive terminal is electrically connected to the positive electrode via the current interrupting means, and the negative terminal is electrically connected to the negative electrode without passing through the current interrupting means. The current interrupting means is formed by spot welding a member electrically connected to the positive electrode and a metal thin film installed thereabove, and the metal thin film swells upward due to an increase in internal pressure. Is interrupted, and thereby the conduction between the positive electrode and the positive electrode terminal is interrupted.

(Example 2)
A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1 except that the amount of biphenyl added to the nonaqueous electrolyte was 4% by weight.

(Comparative Examples 1-16)
A nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the amount of lithium carbonate in the positive electrode and the type and amount of additives in the nonaqueous electrolyte were set as shown in Table 1. In addition, the column shown with the horizontal line in Table 1 shows that lithium carbonate or an additive is not contained. The meanings of the symbols used in Table 1 are as follows.
BP: biphenyl TOL: toluene DFA: 2,4-difluoroanisole

(Overcharge test 1)
An overcharge test was performed on the nonaqueous electrolyte batteries according to Examples 1 and 2 and Comparative Examples 1 to 16. All the batteries were put into the end-of-charge state by constant current and constant voltage charging for 0.2 hours, 4.2 V, and 10 hours before the test. At a temperature of 20 ° C., a direct current of 15 V and 6 A was applied to each battery using a direct current power source capable of knowing the accumulated amount of electricity supplied. For batteries whose battery temperature exceeded 150 ° C. or whose battery temperature did not exceed 150 ° C., the test was terminated when the current interrupting means was activated.

(Overcharge test 2)
An overcharge test was performed on the nonaqueous electrolyte batteries according to Examples 1 and 2 and Comparative Examples 1 to 16 that were separately prepared. All the batteries were put into the end-of-charge state by constant current and constant voltage charging for 0.2 hours, 4.2 V, and 10 hours before the test. At a temperature of 20 ° C., a direct current of 15 V and 200 A was applied to each battery using a direct current power source capable of knowing the accumulated amount of electricity supplied. For batteries whose battery temperature exceeded 150 ° C. or whose battery temperature did not exceed 150 ° C., the test was terminated when the current interrupting means was activated.

In Table 1, the evaluation results of the overcharge test 1 and the overcharge test 2 are indicated by symbols A, B, and C. The meanings of symbols A, B, and C are as follows.
A: The current interrupting means was activated and the pressure release valve was not activated. B: The current interrupting means was activated, but the pressure release valve was activated. C: The battery temperature exceeded 150 ° C.

  In addition, as a result of each overcharge test, the battery temperature rise did not exceed 150 ° C., and the battery with an evaluation result of A or B is based on the value of the accumulated electric quantity energized. The charge depth of the battery is indicated by SOC%. Note that SOC 100% corresponds to the state before the overcharge test.

  From the results of Comparative Examples 11 to 16, when a non-aqueous electrolyte that does not contain an additive is used, if the lithium carbonate content in the positive electrode mixture is 1% by weight or less, the result of the overcharge test is that the battery temperature is It reached 150 ° C. By setting the content of lithium carbonate in the positive electrode mixture to 2% by weight or more, in the result of the overcharge test 1, the current interruption means is activated and the pressure release valve is not activated. Although it was possible, in the result of the overcharge test 2 in which 15V200A was applied, the current interrupting means could be operated, but the internal pressure increased too much, leading to the operation of the pressure release valve.

  In the batteries of Comparative Examples 5 to 10 using the positive electrode not containing lithium carbonate, while using a non-aqueous electrolyte to which biphenyl, toluene or 2,4-difluoroanisole was added as an additive, the amount of the additive was maximized. Even when the content was 4% by weight, the battery temperature reached 150 ° C. as a result of the overcharge test.

  From the results of Examples 1 and 2 and Comparative Examples 1 to 4 in which the positive electrode mixture contains lithium carbonate and the nonaqueous electrolyte contains an additive, the positive electrode mixture contains lithium carbonate, and the nonaqueous electrolyte As long as the type of additive used for biphenyl is biphenyl, the battery temperature does not exceed 150 ° C. even when the overcharge test 2 is applied with 15V200A, and the internal pressure rises below the state in which the pressure release valve operates. The current interrupting means could be operated safely.

  Here, comparing the SOC% at the end of the overcharge test 2, the SOC% values of the batteries of Examples 1 and 2 are small, and the current interrupting mechanism operates at a shallow depth of charge under the fast charge condition of 15V200A. You can see that Moreover, although the effect as biphenyl is not acquired about what added toluene or 2, 4- difluoroanisole to lithium carbonate, SOC% at the time of current interruption has fallen greatly compared with the thing of lithium carbonate simple substance, and at the time of high rate It can be seen that the current can be interrupted quickly by overcharging, and the safety is improved.

  The action of increasing the internal pressure in order to operate the current interrupting means safely is mainly the effect of gas generation by the lithium carbonate contained in the positive electrode mixture, but since the electrolyte contains biphenyl, Polymerization forms a high-resistance film on the electrode surface, which suppresses the progress of the charging reaction, and by forming the high-resistance film, the electrode generates heat due to the charging current, further decomposing lithium carbonate. As a result, the gas generation is promoted and the current interrupting means is easily operated. Among biphenyl, toluene and 2,4-difluoroanisole, which are additives for the non-aqueous electrolyte used in the above test, biphenyl is known to have the highest heat of polymerization, and biphenyl increases with polymerization. It generates gas itself. In this way, by selecting biphenyl having a property that seems to go against safety at a glance that the calorific value is large, and using it in combination with lithium carbonate, the battery temperature rises excessively even during overcharge. As a result, the operation of the current interrupting means, which is a safety mechanism, was promoted.

  In addition, the SOC% value at the end of the overcharge test 1 which is a relatively gradual overcharge condition exceeds 200%, while the overcharge test 2 adopts an extremely severe rapid charge condition of 33 ItA. As can be seen from the fact that the SOC% value at the end of the battery is low particularly in the battery of the example, the application of severe charging conditions is possible according to the present invention using the combination of biphenyl and lithium carbonate. It is very interesting to draw out the effect of.

  A battery system including a battery unit including one or a plurality of nonaqueous electrolyte batteries of the present invention and voltage monitoring and control means can be configured.

  FIG. 1 is a conceptual diagram showing the connection state inside the outer container 5 of the battery of the present invention and the configuration of a battery system using the battery of the present invention. FIG. 1 illustrates a battery system in which the battery unit includes one nonaqueous electrolyte battery. As described above, the positive electrode terminal 1 is electrically connected to the positive electrode constituting the power generation element 6 through the current interrupting means 4 that can detect the state of the battery and interrupt electrical conduction, The positive electrode is electrically connected to the auxiliary terminal 3 without passing through the current interrupting means 4. In the present embodiment, the negative electrode terminal 2 is electrically connected to the negative electrode constituting the power generation element 6 without the current interrupting means 4 interposed therebetween. Since the battery of this example is for HEV, the positive electrode is also electrically connected to the aluminum outer container 5.

  In the battery system of the present invention illustrated in FIG. 1, the voltage monitoring and control means 8 provided between the positive electrode terminal 1 and the negative electrode terminal 2 detects a sudden change in voltage between terminals or a voltage value to detect current. It is determined that the shut-off means 4 has been activated, and the switch 7 is controlled to connect the load resistor 9 between the negative terminal 2 and the auxiliary terminal 3, thereby discharging the power generation element.

  In the voltage monitoring and control means, CS (voltage detection system) detects the voltage signal of the battery unit and transmits it to the battery control unit (BMU = Battery Management Unit). For example, the battery control unit may control the cell balancer to perform forced discharge control of the battery.

  The technology of the present invention that can provide an extremely safe battery should be applied particularly effectively in the technical fields of HEV batteries, emergency power supply systems, power storage systems, etc. where large-sized and high-power batteries are used. Can do.

It is a block diagram which shows an example of the battery system which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive terminal 2 Negative terminal 3 Auxiliary terminal 4 Current interruption means 5 Positive electrode

Claims (3)

In a nonaqueous electrolyte battery in which a negative electrode, a positive electrode with a positive electrode mixture containing lithium carbonate at an overcharged positive electrode potential, and a nonaqueous electrolyte containing biphenyls are housed in an outer container,
The lithium carbonate content is 4% by weight or more,
The biphenyl content is 2% by weight or more,
In the overcharged state, a resistance film generated by polymerization of biphenyls is formed on the electrode surface,
A nonaqueous electrolyte battery characterized in that gas generation is promoted by causing a current to flow through the resistance film to generate heat. The nonaqueous electrolyte battery according to claim 1, further comprising current interrupting means that operates in response to an increase in internal pressure in the outer container. A battery system comprising a battery unit comprising one or a plurality of nonaqueous electrolyte batteries according to claim 2 and voltage monitoring and control means.

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