JP2009123526A - Nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte containing an ambient temperature molten salt, wherein the electrolyte battery can prevent dissolution of a cationic component of the ambient temperature molten salt by reacting to the negative electrode during charging and can obtain sufficient charge/discharge characteristics. <P>SOLUTION: The nonaqueous electrolyte battery comprises the positive electrode, the negative electrode, and the nonaqueous electrolyte containing the ambient temperature molten salt, and carbon dioxide is dissolved in the nonaqueous electrolyte. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte containing a room temperature molten salt, and in particular, a room temperature molten salt at the time of charging without reducing the safety of the nonaqueous electrolyte battery. This is characterized in that the cation component is prevented from reacting and decomposing in the negative electrode, and sufficient charge / discharge characteristics can be obtained.

  In recent years, high-electromotive force non-aqueous electrolyte batteries using non-aqueous electrolytes and utilizing oxidation and reduction of lithium have come into use as new batteries with high output and high energy density.

  Here, in such a nonaqueous electrolyte battery, a nonaqueous electrolyte is generally used in which a solute composed of a lithium salt such as LiBF4 or LiPF6 is dissolved in an organic solvent such as ethylene carbonate or diethyl carbonate. Yes.

  However, organic solvents such as those used in non-aqueous electrolytes tend to have high vapor pressure at high temperatures, and many of them have flammability. Therefore, a safety circuit is provided to prevent overcharging. For this reason, there is a problem such as a high cost.

  For this reason, recently, in place of the organic solvent as described above, a non-aqueous electrolyte is made of a room temperature molten salt composed of a cation and an anion, which is in a liquid state at room temperature, thereby improving the flame retardancy of the non-aqueous electrolyte battery. Therefore, attention has been focused on methods for improving safety.

  However, even when such a room temperature molten salt is used, the cation component of this room temperature molten salt reacts with the negative electrode active material such as a carbon material that absorbs and releases lithium used in the negative electrode during charging, and decomposes. There was a problem that sufficient charge / discharge characteristics could not be obtained.

  For this reason, as shown in Non-Patent Document 1, an additive such as ethylene carbonate (EC) or vinylene carbonate (VC) is added to a non-aqueous electrolyte using a room temperature molten salt, and these additives are used at the time of initial charge. A method has been proposed in which a film is formed on the negative electrode to suppress decomposition of the cation of the room temperature molten salt.

  However, ethylene carbonate (EC), vinylene carbonate (VC), etc. are organic solvents used for non-aqueous electrolytes. As mentioned above, the vapor pressure at high temperatures tends to be high, and the flammability is high. There has been a problem that the flame retardancy of a non-aqueous electrolyte battery using the battery decreases.

Further, in Patent Document 1, the lithium ion and B a non-aqueous electrolyte (C ₂ O _{4) 2} ^- By using the ambient temperature molten salt containing a bis (oxalato) borate anion represented by the non-aqueous electrolyte It has been shown to improve the high-temperature storage characteristics of the battery, and Non-Patent Document 2 uses a room temperature molten salt containing a bis (fluorosulfonyl) imide anion for the nonaqueous electrolyte and graphite for the negative electrode active material. In this case, it is shown that good charge / discharge cycle characteristics can be obtained.

However, when a non-aqueous electrolyte used is a room temperature molten salt containing lithium ion and a bis (oxalate) borate anion represented by B (C ₂ O ₄ ) ₂ ⁻ , or a bis (fluorosulfonyl) imide anion. Even when using a room temperature molten salt containing hydrogen, the cation component of the room temperature molten salt cannot be sufficiently suppressed and decomposed at the negative electrode during charging, and charge / discharge characteristics in a nonaqueous electrolyte battery Could not be improved sufficiently.
JP 2007-141860 A Takaya Sato, Tatsuya Maruo, Shoko Marukane and Kantaro Takagi, Journal of Power Sources, 138 (2004) 253-261 M.Ishikawa, T.Sugimoto, M.Kikuta, M.Kono, Journal of Power Sources 162 (2006) 658-662

  The present invention aims to solve the above problems in a nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte containing a room temperature molten salt. It is an object of the present invention to prevent the cation component of the room temperature molten salt from reacting and decomposing at the negative electrode during charging and to obtain sufficient charge / discharge characteristics without reducing the properties.

  In the present invention, in order to solve the above-described problems, carbon dioxide is dissolved in the nonaqueous electrolyte in a nonaqueous electrolyte battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte containing a room temperature molten salt. I let you.

When carbon dioxide is dissolved in a non-aqueous electrolyte containing a room temperature molten salt as in the non-aqueous electrolyte battery of the present invention, the presence of carbon dioxide gas stabilizes the Li ₂ CO ₃ origin on the surface of the negative electrode during initial charging. In addition, it is considered that a film having excellent lithium ion permeability is formed, and this film suppresses the cation component of the room temperature molten salt from reacting and decomposing at the negative electrode during charging.

  As a result, in the non-aqueous electrolyte battery according to the present invention, the safety of the non-aqueous electrolyte battery is not lowered as in the case where an organic solvent such as ethylene carbonate or vinylene carbonate is added, and the room temperature molten salt is not charged during charging. The cation component is appropriately prevented from reacting and decomposing at the negative electrode, and the charge / discharge characteristics in the nonaqueous electrolyte battery using the room temperature molten salt as the nonaqueous electrolyte are sufficiently improved.

  Next, an embodiment of the nonaqueous electrolyte battery according to the present invention will be specifically described. In addition, the nonaqueous electrolyte battery in this invention is not limited to what was shown to the following embodiment, In the range which does not change the summary, it can change suitably and can implement.

  In the nonaqueous electrolyte battery according to the present invention, as described above, a nonaqueous electrolyte containing a room temperature molten salt is used, and carbon dioxide is dissolved in the nonaqueous electrolyte containing the room temperature molten salt.

  Here, in dissolving carbon dioxide in the non-aqueous electrolyte containing the room temperature molten salt, carbon dioxide can be dissolved by bringing carbon dioxide into contact with the non-aqueous electrolyte.

  Various methods can be used as such a method. For example, a method in which carbon dioxide gas is cooked in a non-aqueous electrolyte, a method in which the non-aqueous electrolyte is stirred in carbon dioxide, a method in which high-pressure carbon dioxide is brought into contact with the non-aqueous electrolyte, a dioxide such as bicarbonate, carbonate, or dry ice. For example, a method of adding a substance that generates carbon to the non-aqueous electrolyte can be used.

  In addition, when manufacturing a nonaqueous electrolyte battery using a nonaqueous electrolyte in which carbon dioxide is dissolved in this manner, in order to stabilize the amount of carbon dioxide dissolved in the nonaqueous electrolyte, an atmosphere containing carbon dioxide is used. It is preferable to manufacture a nonaqueous electrolyte battery.

  For example, a step of injecting a nonaqueous electrolyte in which carbon dioxide is dissolved into the battery, a subsequent step is performed in an atmosphere of carbon dioxide, or a nonaqueous electrolyte in which carbon dioxide is further dissolved is injected into the battery. After that, it can be allowed to stand in an atmosphere of high-pressure carbon dioxide. Further, in the process of producing a nonaqueous electrolyte battery in this way, carbon dioxide can be dissolved in the nonaqueous electrolyte. Since the saturation dissolution amount of carbon dioxide in the non-aqueous electrolyte varies depending on the temperature of the non-aqueous electrolyte, it is preferable to control the temperature of the non-aqueous electrolyte battery as little as possible in the manufacturing process.

  Moreover, in this nonaqueous electrolyte battery, it is preferable to contain lithium ions and anions composed of an oxalate compound in the nonaqueous electrolyte containing the room temperature molten salt.

  Thus, when a non-aqueous electrolyte containing a room temperature molten salt contains a lithium ion and an anion composed of an oxalate compound, the reduction potential in the oxalate compound is higher than the reductive decomposition potential of the cation component of the room temperature molten salt. During initial charging, before the cation component is decomposed, the oxalate compound is reduced, and a film having excellent lithium ion permeability is formed on the surface of the negative electrode.

Then, when carbon dioxide is dissolved in the non-aqueous electrolyte containing the room temperature molten salt and the oxalate compound is contained as described above, the oxalate compound is reduced and the coating film formed on the surface of the negative electrode A film component derived from Li ₂ CO ₃ based on carbon dioxide is contained, thereby forming a dense and strong film excellent in lithium ion permeability on the surface of the negative electrode. It is considered that the components are further prevented from reacting and decomposing at the negative electrode.

Here, the oxalate compound is a compound in which a C ₂ O ₄ group is coordinated, and has a chemical formula M (C ₂ O ₄ ) _x R _y (wherein R is a halogen, an alkyl group having 1 or more carbon atoms). , A group selected from halogen-substituted alkyl groups, M is a transition metal, Group III, Group IV, or Group V element, x is an integer of 1 or more, and y is 0 or a positive integer. ) Is preferably used.

Further, as the oxalate compound, it is more preferable to use an oxalate compound in which M is boron or phosphorus. Examples of the anion of the oxalate compound include [B (C ₂ O ₄ ) ₂ ] ⁻ , [B ( _{C 2 O 4) F 2]} -, [P (C 2 O 4) F 4] -, [P (C 2 O 4) 2 F 2] - or the like can be used, in particular, [B (C ₂ More preferably, a bis (oxalate) borate anion represented by O ₄ ) ₂ ] ^— is used.

  In addition, when the lithium ion and the anion composed of the oxalate compound are contained in the non-aqueous electrolyte containing the room temperature molten salt, the lithium salt of the anion composed of the oxalate compound is dissolved in the non-aqueous electrolyte. Can be.

Here, as the lithium salt of the anion comprising the above oxalate compound, for example, Li [B (C ₂ O ₄ ) ₂ ], Li [B (C ₂ O ₄ ) F ₂ ], Li [P (C ₂ O) ₄ ) F ₄ ], Li [P (C ₂ O ₄ ) ₂ F ₂ ] and the like can be used, preferably lithium bis (oxalate) borate represented by Li [B (C ₂ O ₄ ) ₂ ] Can be used.

Moreover, it is preferable to contain the bis (fluorosulfonyl) imide anion N (FSO ₂ ) ₂ ⁻ in the nonaqueous electrolyte.

When the bis (fluorosulfonyl) imide anion N (FSO ₂ ) ₂ ⁻ is contained in the non-aqueous electrolyte, the bis (fluorosulfonyl) imide anion N (FSO ₂ ) is used as a room temperature molten salt used in the non-aqueous electrolyte. Besides using a room temperature molten salt containing ₂ ⁻ , bis (fluorosulfonyl) imide lithium LiN (FSO ₂ ) ₂ which is a lithium salt thereof can be dissolved in a non-aqueous electrolyte.

  Moreover, in the nonaqueous electrolyte battery of the present invention, in addition to the lithium salt of the anion of the oxalate compound and the lithium salt of bis (fluorosulfonyl) imide, a lithium salt used for the nonaqueous electrolyte in the nonaqueous electrolyte battery is used. Can be used.

Such lithium salts include, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (C _l F _{2l + 1} SO ₂ ) (C _m F _{2m + 1} SO ₂ ). (Wherein l and m are integers of 1 or more), LiC (C _p F _{2p + 1} SO ₂ ) (C _q F _{2q + 1} SO ₂ ) (C _r F _{2r + 1} SO ₂ ) (where p , Q, and r are integers of 1 or more) and the like, or a combination of two or more.

  The amount of these lithium salts is dissolved in the nonaqueous electrolyte so as to have a concentration of 0.1 to 2.0 mol / liter, preferably 0.2 to 1.0 mol / liter. .

In the non-aqueous electrolyte battery of the present invention, it is preferable to use the above bis (fluorosulfonyl) imide anion N (FSO ₂ ) ₂ ⁻ as the anion component in the room temperature molten salt contained in the non-aqueous electrolyte. In addition to this, for example, BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , CF ₃ SO ₃ ⁻ , [N (C _l F _{2l + 1} SO ₂ ) (C _m F _{2m + 1} SO ₂ )] ⁻ (wherein l and m are integers of 1 or more), [C (C _p F _{2p + 1} SO ₂ ) (C _q F _{2q + 1} SO ₂ ) (C _r F _{2r +1} SO _2)] ^- (wherein, p, q, r is an integer of 1 or ^{_{more), CF 3 CO 2 -,}} CH 3 CO 2 - 1 or the anion of such or be used to include two or more Is possible.

  On the other hand, the cation component in the room temperature molten salt includes, for example, one or more elements selected from N, P, S, O, C, and Si, and has a chain structure or a five-membered or six-membered ring. A compound having a cyclic structure such as the above in the skeleton can be used. In particular, it is preferable to use a compound having a chain structure or a cyclic structure containing N from the viewpoint of being chemically and electrochemically stable.

  Examples of the cyclic structure such as the 5-membered ring and 6-membered ring include furan, thiophene, pyrrole, pyridine, oxazole, isoxazole, thiazole, isothiazole, furazane, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, Examples include heterocyclic monocyclic compounds such as pyrrolidine and piperidine, and condensed heterocyclic compounds such as benzofuran, isobenzofuran, indole, isoindole, indolizine, and carbazole.

  Examples of the cation containing N include alkylammonium cations such as triethylammonium, imidazolium cations such as ethylmethylimidazolium and butylmethylimidazolium, and pyrrolium such as 1-methyl-1-propylpyrrolidinium. A cation or a piperidinium cation such as methylpropylpiperidinium can be used.

  In addition, it is preferable that melting | fusing point of said normal temperature molten salt is 20 degrees C or less, and it is more preferable that melting | fusing point is 0 degrees C or less.

  Moreover, in order to improve the wettability with respect to the separator of said nonaqueous electrolyte, it is also possible to add surfactant, such as a trioctyl phosphate, to a nonaqueous electrolyte.

  In the non-aqueous electrolyte battery of the present invention, as the negative electrode active material in the negative electrode, a material that can occlude and release lithium generally used in non-aqueous electrolyte batteries can be used, for example, lithium metal, lithium An alloy, a carbon material, a metal compound, or the like can be used, and these negative electrode active materials can be used alone or in combination of two or more.

  Here, as said lithium alloy, a lithium-aluminum alloy, a lithium-silicon alloy, a lithium-tin alloy, a lithium-magnesium alloy etc. can be used, for example.

  Examples of the carbon material include natural graphite, artificial graphite, coke, vapor grown carbon fiber, mesophase pitch carbon fiber, spherical carbon, and resin-fired carbon.

  Further, as the carbon material, a covering structure in which a part or all of the surface of the first carbon material having high crystallinity as the core material is covered with the second carbon material having lower crystallinity than the first carbon material. It is preferable to use a carbon material having such a coating structure, and when the carbon material having such a coating structure is used, the cation component of the room temperature molten salt reacts and decomposes in the negative electrode during charging, and is further suppressed.

  Here, a carbon material having a covering structure in which a part or all of the surface of the first carbon material having high crystallinity as the core material is coated with the second carbon material having lower crystallinity than the first carbon material as described above. As a method of manufacturing, for example, a method in which the first carbon material as a core material is mixed with a carbonizable organic compound and baked, a CVD method, or the like can be used.

  And in the method of mixing and firing the first carbon material as a core material with a carbonizable organic compound, in pitch, tar, etc., or phenol formaldehyde resin, furfuryl alcohol resin, carbon black, vinylidene chloride, Cellulose or the like is dissolved in an organic solvent such as methanol, ethanol, benzene, acetone, toluene, etc., and the first carbon material as a core material is immersed in the solution, and then this is heated to 500 to 1800 ° C. in an inert atmosphere. The carbonization is preferably performed by baking at a temperature of 700 to 1400 ° C.

  Further, in the CVD method, the vapor of an organic compound is introduced into the first carbon material as a core material for a certain period of time under high temperature conditions, and the organic compound used in the CVD method is as follows. For example, hydrocarbons such as methane, ethane, propane, butane, ethylene, propylene, butene, benzene, toluene, ethylbenzene, cyclohexane, cyclopentene, or derivatives thereof can be used. Then, after these organic compounds are heated and vaporized, they are fed into a reaction vessel containing a carbon material as a core material using nitrogen or an inert gas as a carrier. In addition, the processing temperature of the carbon material used as the core material at this time is set to a range of 500 to 1800 ° C, preferably 700 to 1400 ° C.

In order to obtain a non-aqueous electrolyte battery having a high discharge capacity, it is preferable to use a graphite-based material for the first carbon material as the core material, and it is preferably obtained by X-ray diffraction (002). ) Surface spacing d ₀₀₂ is in the range of 0.335 to 0.338 nm, and the crystallite size Lc in the c-axis direction is 30 nm or more, more preferably d ₀₀₂ is 0. A carbon material having a range of 335 to 0.336 nm and Lc of 100 nm or more is used.

As the first carbon material as the above-mentioned core material, and the peak intensity I _G of around 1580 cm ^-1 as determined by laser Raman spectroscopy using an argon ion laser having a wavelength of 514.5 nm, a peak around 1360 cm ^-1 It is preferable to use one having an R value (I _D / I _G ) calculated from the intensity I _{D in} the range of 0.05 to 0.8.

Moreover, in the nonaqueous electrolyte battery of the present invention, as the positive electrode active material in the positive electrode, those commonly used in nonaqueous electrolyte batteries can be used, for example, lithium-cobalt oxide Li _x CoO ₂ , Lithium-nickel oxide Li _x NiO ₂ , lithium-nickel-cobalt-manganese composite oxide Li _x Ni _a Co _b Mn _c O ₂ , lithium-manganese oxide Li _x Mn ₂ O ₄ , lithium-iron phosphate Li _x FePO ₄ or the like can be used.

  Next, the nonaqueous electrolyte battery according to the present invention will be specifically described with reference to examples, and in the nonaqueous electrolyte battery according to this example, the charge / discharge characteristics are improved with reference to a comparative example. To clarify. The nonaqueous electrolyte battery of the present invention is not limited to those shown in the following examples, and can be implemented with appropriate modifications within a range not changing the gist thereof.

Example 1
In Example 1, in preparing the working electrode, graphite powder having the d ₀₀₂ of 0.336 nm, the Lc of 100 nm or more, and the R value of 0.08 was used as the negative electrode active material. Then, 97.5 parts by weight of this graphite powder, 1 part by weight of styrene-butadiene rubber, and 1.5 parts by weight of carboxymethylcellulose were mixed, and water was added to this mixture to form a slurry. Was applied to one side of a current collector made of copper foil, dried and rolled, and then cut into a disk shape having a diameter of 20 mm to produce a working electrode.

  As the counter electrode, a lithium rolled plate having a predetermined thickness was punched into a disk shape having a diameter of 20 mm.

  In preparing a non-aqueous electrolyte, bis (oxalate) borane is added to a room temperature molten salt (EMI-FSI) containing ethylmethylimidazolium (EMI) as a cation and bis (fluorosulfonyl) imide (FSI) as an anion. After dissolving lithium acid (LiBOB) at a rate of 0.2 mol / liter, carbon dioxide gas was blown into the carbon dioxide atmosphere at a flow rate of 300 ml / min for about 30 minutes to prepare a nonaqueous electrolyte.

  As shown in FIG. 1, a separator 3 made of a polyethylene microporous film is interposed between the counter electrode 1 and the working electrode 2, and the separator 3 is impregnated with the nonaqueous electrolyte. These are accommodated in a battery can 4 comprising a stainless steel counter electrode side battery can 4a and a working electrode side battery can 4b, and the counter electrode 1 is connected to the counter electrode side battery can 4a while the working electrode 2 is Connected to the working electrode side battery can 4b, the insulating packing 5 is arranged between the counter electrode side battery can 4a and the working electrode side battery can 4b to caulk the battery can 4, and the counter electrode side battery can 4a and the working electrode side battery The test battery of Example 1 having a coin shape having a diameter of 24.0 mm and a thickness of 3.0 mm was manufactured by insulating and sealing the can 4b.

  Here, this test battery is configured to evaluate the charge / discharge characteristics of the negative electrode when each non-aqueous electrolyte is used. In this test battery, when a current in a direction in which the potential of the working electrode becomes low is passed, lithium ions are occluded and charged in the negative electrode that is the working electrode. Further, when a current in a direction in which the potential of the working electrode becomes noble is passed, lithium ions are discharged from the negative electrode that is the working electrode and discharged. This test battery is configured with a large excess of metallic lithium in terms of electric capacity, and the characteristics of the negative electrode and the non-aqueous electrolyte can be evaluated with this test battery.

(Comparative Example 1)
In Comparative Example 1, a non-aqueous electrolyte was prepared in the same manner as in Example 1 above, and a room temperature molten salt containing ethylmethylimidazolium (EMI) as a cation and bis (fluorosulfonyl) imide (FSI) as an anion. In (EMI-FSI), bis (oxalate) lithium borate (LiBOB) was dissolved at a rate of 0.2 mol / liter, while carbon dioxide gas was not blown into this to produce a non-aqueous electrolyte, A test battery of Comparative Example 1 was produced in the same manner as in Example 1 except for the above.

(Example 2)
In Example 2, in preparing a non-aqueous electrolyte, a room temperature molten salt (EMI-FSI) containing ethylmethylimidazolium (EMI) as a cation and bis (fluorosulfonyl) imide (FSI) as an anion is replaced with bis ( After trifluoromethylsulfonyl) imidolithium (LiTFSI) was dissolved at a rate of 0.2 mol / liter, carbon dioxide gas was blown into it at a flow rate of 300 ml / min for about 30 minutes in a carbon dioxide atmosphere. A test battery of Example 2 was produced in the same manner as in Example 1 except that an electrolyte was produced.

(Comparative Example 2)
In Comparative Example 2, when producing a non-aqueous electrolyte, a room temperature molten salt containing ethylmethylimidazolium (EMI) as a cation and bis (fluorosulfonyl) imide (FSI) as an anion as in Example 2 above. In (EMI-FSI), bis (trifluoromethylsulfonyl) imidolithium (LiTFSI) is dissolved at a rate of 0.2 mol / liter, while carbon dioxide gas is not blown into this to produce a non-aqueous electrolyte, Otherwise, the test battery of Comparative Example 2 was produced in the same manner as in Example 1 above.

For each of the test batteries of Examples 1 and 2 and Comparative Examples 1 and 2 manufactured as described above, the voltage of the working electrode with respect to the counter electrode is 0.0 V at a current density of 0.1 mA / cm ^2. Until this time, lithium ions were inserted into the working electrode from the counter electrode, the charge capacity Q1 (mAh / g) of the negative electrode active material in the working electrode of each test battery was determined, and the results are shown in Table 1 below. In the test battery of Comparative Example 2 described above, since charging was not completed, the charge capacity Q1 could not be obtained, and subsequent measurements could not be performed.

Then, for each test cells of Examples 1 and 2 and Comparative Example 1 were charged as described above, each current density 0.1 mA / cm ² constant current, the voltage of the working electrode relative to the counter electrode to 1.0V Until this time, lithium ions are desorbed from the working electrode into which lithium ions have been inserted as described above, and the discharge capacity Q2 (mAh / g) of the negative electrode active material at the working electrode of each test battery is determined. It showed in Table 1.

  And about each test battery of Examples 1, 2 and Comparative Example 1, charge / discharge efficiency (%) is calculated | required by the following formula from the charge capacity Q1 and discharge capacity Q2 which were calculated | required as mentioned above, respectively. The results are shown in Table 1 below.

  Charging / discharging efficiency (%) = (Q2 / Q1) × 100

  As is clear from this result, the test batteries of Examples 1 and 2 in which carbon dioxide was dissolved in a nonaqueous electrolyte using a room temperature molten salt were compared in which carbon dioxide was not dissolved in the corresponding nonaqueous electrolyte. Compared with the test batteries of Examples 1 and 2, the charge / discharge characteristics were greatly improved.

Further, when the test batteries of Examples 1 and 2 were compared, lithium ion and bis (oxalate) borate anion B (C ₂ O ₄ ) were added to the nonaqueous electrolyte by adding bis (oxalate) lithium borate (LiBOB). ) ₂ ^- test cells of example 1 so as to contain the bis (oxalate) borate anion B (C ₂ O _{4) 2} ^- as compared with the test cells of example 2 which does not contain a The charge / discharge characteristics were greatly improved.

It is a schematic sectional drawing of the battery for a test produced in the Example and comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Counter electrode 2 Working electrode 3 Separator 4 Battery can 4a Counter electrode side battery can 4b Working electrode side battery can

Claims (5)

  A nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte containing a room temperature molten salt, wherein carbon dioxide is dissolved in the nonaqueous electrolyte.   The nonaqueous electrolyte battery according to claim 1, wherein the nonaqueous electrolyte contains lithium ions and an anion composed of an oxalate compound.   The nonaqueous electrolyte battery according to claim 2, wherein the anion composed of the oxalate compound is an anion of an oxalate compound of boron or phosphorus. In the nonaqueous electrolyte battery according to claim 3, anions consisting of the oxalate compound, bis (oxalate) borate anion _{B (C 2 O 4) 2} - nonaqueous electrolyte battery which is a.   The nonaqueous electrolyte battery according to any one of claims 1 to 4, wherein the nonaqueous electrolyte contains a bis (fluorosulfonyl) imide anion.

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