JP2004071577A - Non-aqueous electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte for a high-capacity non-aqueous electrolyte secondary battery having high capacity and good charge / discharge cycle characteristics.
A non-aqueous electrolyte containing a solvent and a lithium salt, wherein the electrolyte contains 0.0001 to 0.1 mol / L of an N-containing polycyclic condensed compound with respect to the solvent. Non-aqueous electrolyte.
[Selection diagram] None

Description

The present invention relates to a non-aqueous electrolyte for a high-capacity non-aqueous electrolyte secondary battery having excellent charge-discharge cycle characteristics, and a discharge capacity in which a negative electrode material is mainly an amorphous chalcogen compound and / or an amorphous oxide. The present invention relates to improvement of charge / discharge characteristics such as charge / discharge cycle life of a nonaqueous electrolyte secondary battery having a large value.

Lithium metals and lithium alloys are typical examples of negative electrode materials for nonaqueous electrolyte secondary batteries, but when they are used, so-called dendrites in which lithium metal grows in dendrites during charge and discharge occur, causing internal short circuit. Alternatively, the high activity of the dendrite itself caused a danger such as ignition. On the other hand, fired carbonaceous materials capable of reversibly inserting and releasing lithium have come into practical use. The drawback of this carbonaceous material is that it has conductivity in itself, so lithium metal can be deposited on the carbonaceous material during overcharging or rapid charging, resulting in the precipitation of dendrites. . To avoid this, the charger is devised, or a method of preventing overcharging by reducing the amount of the positive electrode active material is adopted.However, in the latter method, the amount per active material is limited. Therefore, the discharge capacity is also limited. Further, since the density of the carbonaceous material is relatively small, the discharge capacity is limited in the double sense that the capacity per volume is low. Patent Literatures 1 to 9 disclose that a lithium foil is pressure-bonded or laminated on a carbon material, but uses a carbon material as a negative electrode active material and essentially solves the above problem. Was not something to do.

On the other hand, as negative electrode materials other than lithium metal, lithium alloy, and carbonaceous material, lithium compounds such as TiS ₂ , LiTiS ₂ (see Patent Document 10), WO ₂ , and FeO ₃ which can occlude and release lithium ions (Patent Document 10) Reference 11), Nb ₂ O ₅ (Patent Documents 12 and 13), iron oxide, FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , cobalt oxide, CoO, Co ₂ O ₃ , Co ₃ O ₄ (Patent Document 14) are known. Each of these compounds has a low oxidation-reduction potential and cannot realize a nonaqueous electrolyte secondary battery having a high discharge potential of 3V class. In addition, no satisfactory discharge capacity was obtained.

In order to improve the above drawbacks, a non-aqueous electrolyte secondary battery having a high discharge potential with an average discharge voltage of 3 to 3.6 V class has been achieved by oxidizing Sn, V, Si, B, Zr and the like to the negative electrode material. It has been proposed to use compounds and their composite oxides (see Patent Documents 15 to 20). These oxides such as Sn, V, Si, B, and Zr, and their composite oxides are combined with a positive electrode of a transition metal compound containing a certain kind of lithium, so that the average discharge voltage is 3 to 3.6 V class. Thus, a non-aqueous electrolyte secondary battery having a large discharge capacity, a very small amount of generation of dendrites in a practical area, and a very high safety is provided. In order to improve the cyclability, it has been proposed that Na phenanthroline sulfonate or the like be present in the battery (see Patent Document 21). However, since these additives have low solubility, a method of adding them to the electrolyte solution is proposed. However, there are problems such as the necessity of re-applying only the additive to the formed electrode, and the difficulty in distributing the additive uniformly in the battery, which tends to cause variations in characteristics.

JP-A-61-54165 JP-A-2-82447 Japanese Patent Application Laid-Open No. H2-215062 JP-A-3-122974 JP-A-3-272571 JP-A-5-144471 JP-A-5-144472 JP-A-5-144473 JP-A-5-151995 U.S. Patent No. 983476 JP-A-3-111070 JP-B-62-59412 JP-A-2-82447 JP-A-3-291962 JP-A-5-174818 JP-A-6-60867 JP-A-6-275267 JP-A-6-325765 JP-A-6-338324 European Patent No. 615296 JP-A-7-65863

課題 An object of the present invention is to improve charge / discharge cycle characteristics of a nonaqueous electrolyte secondary battery having a large discharge capacity.

An object of the present invention is a non-aqueous electrolyte containing a solvent and a lithium salt, characterized in that the electrolyte contains 0.0001 to 0.1 mol / L of an N-containing polycyclic fused compound with respect to the solvent. Was achieved by a non-aqueous electrolyte.

非 By using an electrolyte containing an N-containing polycyclic fused compound as in the present invention, a non-aqueous electrolyte secondary battery having excellent charge / discharge characteristics and having a small discharge capacity due to repeated charge / discharge can be obtained.

Preferred embodiments of the present invention are described below, but the present invention is not limited thereto.
(1) A positive electrode containing a material capable of reversibly inserting and extracting lithium, and mainly containing an amorphous chalcogen compound and / or a non-crystalline chalcogen compound containing three or more kinds of atoms selected from atoms of groups 1, 2, 13, 14, and 15 of the periodic table. A negative electrode comprising a crystalline oxide, a non-aqueous electrolyte containing a lithium salt, and a non-aqueous electrolyte secondary battery comprising a separator, wherein the non-aqueous electrolyte contains at least one N-containing polycyclic fused compound. Non-aqueous electrolyte secondary battery.
(2) The nonaqueous electrolyte secondary battery according to item 1, wherein at least one of the negative electrode materials is represented by the general formula (1).
M ₁ M _2p M _4q M _6r General formula (1)
(Where M ₁ and M ₂ are different from each other and are at least one selected from Si, Ge, Sn, Pb, P, B, Al and Sb, and M ₄ is Li, K, Na, Cs, Mg, Ca, Sr, at least one at least one, M ₆ is O, S, selected from Te selected from Ba, p, q are each 0.001 to 10, r represents a number of from 1.00 to 50.)
(3) The nonaqueous electrolyte secondary battery according to item 2, wherein at least one of the negative electrode materials is represented by the general formula (2).
SnM _3p M _5q M _7r General formula (2)
(Wherein, M ₃ is at least one selected from Si, Ge, Pb, P, B, and Al; M ₅ is at least one selected from Li, K, Na, Cs, Mg, Ca, Sr, and Ba; ₇ is at least one selected from O and S, p and q each represent a number of 0.001 to 10, and r represents a number of 1.00 to 50.)
(4) at least one positive electrode _{material, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x Co a Ni (1-a) O 2, Li x Co b V (1-b) _{O z, Li x Co b Fe} (1-b) O 2, Li x Mn 2 O 4, Li x Mn c Co (2-c) O 4, Li x Mn c Ni (2-c) O 4, Li _{x Mn c V (2-c} ) O 4, Li x Mn c Fe (2-c) O 4 ( where, x = 0.2~1.2, a = 0.1~0.9 , b = 0.8 to 0.98, c = 1.6 to 1.96, z = 2.01 to 2.3), wherein the nonaqueous electrolyte according to any one of Items 1 to 3, Secondary battery.

In the present invention, the charge-discharge cycle characteristics can be improved without impairing the high capacity of the nonaqueous electrolyte secondary battery by including at least one N-containing organic compound in the electrolyte. Examples of the N-containing organic compound that can be used in the present invention include N-containing chain compounds, N-containing cyclic compounds, N-containing aromatic compounds, and N-containing polycyclic condensed compounds. Examples of the N-containing organic compound of the present invention are shown below, but the present invention is not limited thereto. Examples of the N-containing chain compound and the N-containing aromatic compound include a compound represented by the general formula: R ₁ R ₂ R ₃ N (R ₁ , R ₂ , and R ₃ are each H, or a saturated hydrocarbon group having 1 to 20 carbon atoms; R ₁ , R ₂ , and R ₃ may be the same or different.) Specific examples thereof include ethylamine, propylamine, butylamine, and hexyl. Amine, cyclohexylamine, ethylenediamine, diethylamine, dipropylamine, triethylamine, tributylamine, tripropylamine, diisopropylethylamine, aniline, N-methylaniline, N, N-dimethylaniline, naphthylamine, N, N-dimethylnaphthylamine, diphenylamine, etc. Can be mentioned. Examples of the N-containing cyclic compound include pyridine, pyrimidine, pyrrole, 3-pyrroline, quinoline, quinazoline, quinoxaline, phthalazine, piperidine, dipiperazinomethane, piperazine, 1,10-phenanthroline, 4,7-diphenyl-1,10 -Phenanthroline, 1,4-diazabicyclo [2.2.2] octane, morpholine, indole, imidazole, benzimidazole, 1-methylbenzimidazole, 4,4'-dipyridyl, 2,2'-dipyridyl, 2,2 ' -Dipyridylamine and the like. Examples of the N-containing polycyclic fused compound include 1,5-diazabicyclo [4.3.0] -5-nonene and 1,8-diazabicyclo [5.4.0] -7-undecene.

(4) The content of the N-containing organic compound contained in the electrolyte is preferably from 0.0001 to 0.1 mol / l, more preferably from 0.001 to 0.1 mol / l, based on the electrolyte solution solvent.

The electrolyte is generally composed of a solvent and a supporting salt dissolved in the solvent, and the supporting salt is preferably a lithium salt (anion and lithium cation). Solvents for the electrolyte that can be used in the present invention include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl formate, methyl acetate, 1,2-dimethoxyethane, tetrahydrofuran, -Methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, dioxane, acetonitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2- Non-produced products such as oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethyl ether, 1,3-propanesultone, etc. Can be exemplified ton organic solvent, mixed and used alone or in combination. Among them, a carbonate-based solvent is preferable, and a solvent containing a cyclic carbonate and / or a non-cyclic carbonate is preferable. As the cyclic carbonate, ethylene carbonate and propylene carbonate are preferable. Further, as the acyclic carbonate, it is preferable to include diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. As the supporting salt dissolved in those solvents that can be used in the present invention, for _{example, LiClO 4, LiBF 4, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, lithium lower aliphatic carboxylic acids, Li salts such as LiAlCl ₄ , LiCl, LiBr, LiI, lithium chloroborane and lithium tetraphenylborate can be used, and one or more of these can be used in combination. Among them, those in which LiBF ₄ and / or LiPF ₆ are dissolved are preferred. The concentration of the supporting salt is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolyte solution. Examples of the combination of the electrolytes that can be used in the present invention include LiCF ₃ SO ₃ , LiClO ₄ , LiBF _4, and / or LiPF ₄ in an electrolyte solution obtained by appropriately mixing ethylene carbonate, propylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, or diethyl carbonate. _An electrolyte containing ₆ is preferred. In particular, an electrolyte containing LiCF ₃ SO ₃ , LiClO ₄ , LiBF ₄ and / or LiPF ₆ in a mixed solvent of propylene carbonate or ethylene carbonate with 1,2-dimethoxyethane and / or diethyl carbonate is preferable. Those containing LiPF ₆ are preferred. The amount of these electrolytes to be added to the battery is not particularly limited, but a required amount can be used depending on the amounts of the positive electrode active material and the negative electrode material and the size of the battery.

Hereinafter, other materials and a method for manufacturing the nonaqueous electrolyte secondary battery of the present invention will be described in detail. The positive and negative electrodes used in the non-aqueous electrolyte secondary battery of the present invention can be prepared by applying a positive electrode mixture or a negative electrode mixture on a current collector. The positive electrode or negative electrode mixture can contain a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and various additives, respectively, in addition to the positive electrode active material or the negative electrode material, respectively.

It is preferable that the negative electrode material used in the present invention is mainly amorphous when the battery is incorporated. Here, the term “amorphous” mainly refers to a substance having a broad scattering band having a peak at 20 ° to 40 ° in 2θ value by X-ray diffraction using CuKα ray, and having a crystalline diffraction line. Is also good. Preferably, the strongest intensity of the crystalline diffraction lines observed at a 2θ value of 40 ° or more and 70 ° or less has a diffraction line intensity of 500 at the apex of a broad scattering band observed at a 2θ value of 20 ° or more and 40 ° or less. It is preferably not more than 100 times, more preferably not more than 100 times, particularly preferably not more than 5 times, and most preferably not having a crystalline diffraction line.

The negative electrode material used in the present invention is preferably represented by the following general formula (1).
M ₁ M _2p M _4q M _6r General formula (1)
In the formula, M ₁ and M ₂ are different from each other and are at least one selected from Si, Ge, Sn, Pb, P, B, Al, and Sb, and are preferably Si, Ge, Sn, P, B, and Al; Particularly preferred are Si, Sn, P, B, and Al. M ₄ is at least one of Li, Na, K, Rb, Cs, Mg, Ca, Sr, selected from Ba, preferably K, Cs, Mg, with Ca, particularly preferably Cs, Mg. M ₆ is at least one selected from O, S, and Te, preferably O and S, and particularly preferably O. p and q are each 0.001 to 10, preferably 0.01 to 5, and particularly preferably 0.01 to 2. r is 1.00 to 50, preferably 1.00 to 26, and particularly preferably 1.02 to 6. The valences of M ₁ and M ₂ are not particularly limited, and may be a single valence or a mixture of each valence. The M _1, M _2, the ratio of M ₄ can be continuously changed in a range M ₂ and M ₄ are from 0.001 to 10 molar equivalents relative to M _1, the amount of M ₆ accordingly (typically In equation (1), the value of r) also changes continuously.

Among the compounds mentioned above, in the present invention, the case where M ₁ is Sn is preferable, and represented by the general formula (2).
SnM _3p M _5q M _7r General formula (2)
In the formula, M ₃ is at least one selected from Si, Ge, Pb, P, B and Al, preferably Si, Ge, P, B and Al, and particularly preferably Si, P, B and Al. is there. M ₅ is at least one of Li, Na, K, Rb, Cs, Mg, Ca, Sr, selected from Ba, preferably Cs, with Mg, particularly preferably Mg. M ₇ is at least one selected from O and S, and is preferably O. p and q are each 0.001 to 10, preferably 0.01 to 5, more preferably 0.01 to 1.5, and particularly preferably 0.7 to 1.5. r is 1.00 to 50, preferably 1.00 to 26, and particularly preferably 1.02 to 6.

Examples of the negative electrode material of the present invention are shown below, but the present invention is not limited thereto. SnAl _0.4 B _0.5 P _0.5 K _0.1 O _3.65 , SnAl _0.4 B _0.5 P _0.5 Na _0.2 O _3.7 , SnAl _0.4 B _0.3 P _0.5 RB _0.2 O _3.4 , SnAl _0.4 B _0.5 P _0.5 Cs _0.1 O _3.65 , SnAl _0.4 B _0.5 P _{0.5 K 0.1 Ge 0.05 O 3.85, SnAl} 0.4 B 0.5 P 0.5 K 0.1 Mg 0.1 Ge 0.02 O 3.83, SnAl 0.4 B 0.4 P 0.4 O 3.2, SnAl 0.3 B 0.5 P 0.2 O 2.7, SnAl 0.3 B 0.5 P 0.2 O 2.7, SnAl _{0.4 B 0.5 P 0.3 Ba 0.08 Mg} 0.08 O 3.26, SnAl 0.4 B 0.4 P 0.4 Ba 0.08 O 3.28, SnAl 0.4 B 0.5 P 0.5 O 3.6, SnAl 0.4 B 0.5 P 0.5 Mg 0.1 O 3.7.

_{SnAl 0.5 B 0.4 P 0.5 Mg 0.1} F 0.2 O 3.65, SnB 0.5 P 0.5 Li 0.1 Mg 0.1 F 0.2 O 3.05, SnB 0.5 P 0.5 K 0.1 Mg 0.1 F 0.2 O 3.05, SnB 0.5 P 0.5 K 0.05 Mg 0.05 F 0.1 O _{3.03, SnB 0.5 P 0.5 K 0.05} Mg 0.1 F 0.2 O 3.03, SnAl 0.4 B 0.5 P 0.5 Cs 0.1 Mg 0.1 F 0.2 O 3.65, SnB 0.5 P 0.5 Cs 0.05 Mg 0.05 F 0.1 O 3.03, SnB 0.5 P 0.5 Mg 0.1 F _0.1 O _3.05 , SnB _0.5 P _0.5 Mg _0.1 F _0.2 O ₃ , SnB _0.5 P _0.5 Mg _0.1 F _0.06 O _3.07 , SnB _0.5 P _0.5 Mg _0.1 F _0.14 O _3.03 , SnPBa _0.08 O _3.58 , SnPK _0.1 O _3.55 , SnPK _0.05 Mg _{0.05 O 3.58, SnPCs 0.1 O 3.55} , SnPBa 0.08 F 0.08 O 3.54, SnPK 0.1 Mg 0.1 F 0.2 O 3.55, SnPK 0.05 Mg 0.05 F 0.1 O 3.53, SnPCs 0.1 Mg 0.1 F 0.2 O 3.55, SnPCs 0.05 M _0.05 F _0.1 O _3.53.

_{Sn 1.1 Al 0.4 B 0.2 P 0.6} Ba 0.08 F 0.08 O 3.54, Sn 1.1 Al 0.4 B 0.2 P 0.6 Li 0.1 K 0.1 Ba 0.1 F 0.1 O 3.65, Sn 1.1 Al 0.4 B 0.4 P 0.4 Ba 0.08 O 3.34, Sn 1.1 Al _0.4 PCs _0.05 O _4.23 , Sn _1.1 Al _0.4 PK _0.04 O _4.23 , Sn _1.2 Al _0.5 B _0.3 P _0.4 Cs _0.2 O _3.5 , Sn _1.2 Al _0.4. B _0.2 P _0.6 Ba _0.08 O _3.68 , Sn _1.2 Al _0.4 B _0.2 P _0.6 Ba _0.08 F _0.08 O _3.64 , Sn _1.2 Al _0.4 B _0.2 P _0.6 Mg _0.04 Ba _0.04 O _3.68 , Sn _1.2 Al _0.4 B _0.3 P _0.5 Ba _0.08 O _3.58 , Sn _1.3 Al _0.3 B _0.3 P _0.4 Na _0.2 O _3.3 , Sn _1.3 Al _0.2 B _0.4 P _0.4 Ca _0.2 O _3.4 , Sn _1.3 Al _0.4 B _0.4 P _0.4 Ba _0.2 O _3.6 , Sn _1.4 Al _0.4 PK _0.2 O _4.6 , Sn _1.4 Al _0.2 Ba _0.1 PK _0.2 O _4.45 , Sn _1.4 Al _0.2 Ba _0.2 PK _0.2 O _4.6 , Sn _1.4 Al _0.4 Ba _0.2 PK _0.2 Ba _{0. 1} F _0.2 O _4.9 , Sn _1.4 Al _0.4 PK _0.3 O _4.65 , Sn _1.5 Al _0.2 PK _0.2 O _4.4 , Sn _1.5 Al _0.4 PK _0.1 O _4.65 , Sn _1.5 Al _0.4 PCs _0.05 O _4.63 , Sn _1.5 Al _0.4 PCs _0.05 Mg _0.1 F _0.2 O _4.63 .

_{SnSi 0.5 Al 0.1 B 0. 2} P 0.1 Ca 0.4 O 3.1, SnSi 0.4 Al 0.2 B 0.4 O 2.7, SnSi 0.5 Al 0.2 B 0.1 P 0.1 Mg 0.1 O 2.8, SnSi 0.6 Al 0.2 B 0.2 O 2.8, SnSi 0.5 Al 0.3 _{B 0.4 P 0.2 O 3.55, SnSi} 0.5 Al 0.3 B 0.4 P 0.5 O 4.30, SnSi 0.6 Al 0.1 B 0.1 P 0.3 O 3.25, SnSi 0.6 Al 0.1 B 0.1 P 0.1 Ba 0.2 O 2.95, SnSi 0.6 Al 0.1 B 0.1 P 0.1 Ca _0.2 O _2.95 , SnSi _0.6 Al _0.4 B _0.2 Mg _0.1 O _3.2 , SnSi _0.6 Al _0.1 B _0.3 P _0.1 O _3.05 , SnSi _0.6 Al _0.2 Mg _0.2 O _2.7 , SnSi _0.6 Al _0.2 Ca _0.2 O _2.7 , SnSi _0.6 Al _0.2 P _0.2 O ₃ , SnSi _0.6 B _0.2 P _0.2 O ₃ , SnSi _0.8 Al _0.2 O _2.9 , SnSi _0.8 Al _0.3 B _0.2 P _0.2 O _3.85 , SnSi _0.8 B _0.2 O _2.9 , SnSi _0.8 Ba _0.2 O _2.8 , SnS i _0.8 Mg _0.2 O _2.8 , SnSi _0.8 Ca _0.2 O _2.8 , SnSi _0.8 P _0.2 O _3.1 .

Sn _0.9 Mn _0.3 B _0.4 P _0.4 Ca _0.1 RB _0.1 O _2.95 , Sn _0.9 Fe _0.3 B _0.4 P _0.4 Ca _0.1 RB _0.1 O _2.95 , Sn _0.8 PB _0.2 Ca _0.1 P _0.9 O _3.35 , Sn _0.3 Ge _0.7 Ba _0.1 P _0.9 O _{3.35, Sn 0.9 Mn 0.1 Mg 0.1} P 0.9 O 3.35, Sn 0.2 Mn 0.8 Mg 0.1 P 0.9 O 3.35, Sn 0.7 PB 0.3 Ca 0.1 P 0.9 O 3.35, Sn 0.2 Ge 0.8 Ba 0.1 P 0.9 O 3.35.

化学 The chemical formula of the compound obtained by calcining can be calculated from inductively coupled plasma (ICP) emission spectroscopy as a measuring method, and from the weight difference of powder before and after calcining as a simple method.

(4) The amount of light metal inserted into the negative electrode material of the present invention may be close to the deposition potential of the light metal. For example, the amount is preferably 50 to 700 mol% per negative electrode material, and particularly preferably 100 to 600 mol%. It is preferable that the release amount is larger than the insertion amount. The method of inserting the light metal is preferably an electrochemical, chemical or thermal method. As the electrochemical method, a method of electrochemically inserting a light metal contained in the positive electrode active material or a method of directly electrochemically inserting a light metal or an alloy thereof from a light metal is preferable. As a chemical method, there is a method of mixing or contacting with a light metal or a method of reacting with an organic metal such as butyllithium. Electrochemical and chemical methods are preferred. The light metal is particularly preferably lithium or lithium ion.

In the present invention, the compounds represented by the general formulas (1) and (2) as described above are mainly used as the negative electrode material, whereby the charge / discharge cycle characteristics are more excellent, the discharge voltage is higher, and the capacity is higher and the safety is higher. It is possible to obtain a non-aqueous electrolyte secondary battery having high performance and high current characteristics. In the present invention, a particularly excellent effect can be obtained by using a compound containing Sn and having a Sn valence of 2 as the negative electrode material. The valence of Sn can be determined by a chemical titration operation. For example, Physics and Chemistry of Glasses Vol. 8 No. 4 (1967), page 165. It can also be determined from the night shift of Sn by solid state nuclear magnetic resonance (NMR) measurement. For example, in the wide measurement, the metal Sn (zero-valent Sn) has a peak in an extremely low magnetic field of about 7000 ppm relative to Sn (CH ₃ ) ₄ , whereas the SnO (= bivalent) has a peak of about 100 ppm and SnO (= bivalent). _{At 2} (= tetravalent), it appears near -600 ppm. As described above, when the same ligand is used, the night shift greatly depends on the valence of Sn as the central metal, so that the valence can be determined based on the peak position obtained by 119Sn-NMR measurement. Various compounds can be included in the negative electrode material of the present invention. For example, transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, lanthanoid metals, Hf , Ta, W, Re, Os, Ir, Pt, Au, Hg) and Group 17 elements of the periodic table (F, Cl). Further, it may contain dopants of various compounds (for example, compounds of Sb, In, and Nb) that increase electron conductivity. The amount of the compound to be added is preferably 0 to 20 mol%.

As a method for synthesizing the composite oxide mainly composed of the oxides represented by the general formulas (1) and (2) in the present invention, any of a firing method and a solution method can be adopted. For example, the firing method will be described in detail. M ₁ compound, M ₂ compound and M ₄ compound (M ₁ and M ₂ are different from each other, Si, Ge, Sn, Pb, P, B, Al, Sb and M ₄ are Mg, Ca , Sr, Ba) may be mixed and fired. Examples of the Sn compound include SnO, SnO ₂ , Sn ₂ O ₃ , Sn ₃ O ₄ , Sn ₇ O ₁₃ .H ₂ O, Sn ₈ O ₁₅ , stannous hydroxide, stannic oxyhydroxide, and stannic acid. , Stannous oxalate, stannous phosphate, orthostannic acid, metastannic acid, parastannic acid, stannous fluoride, stannic fluoride, stannous chloride, stannic chloride, stannous pyrophosphate , Tin phosphide, stannous sulfide, stannic sulfide, and the like. Examples of the Si compound include organic silicon compounds such as SiO ₂ , SiO, tetramethylsilane and tetraethylsilane, alkoxysilane compounds such as tetramethoxysilane and tetraethoxysilane, and hydrosilane compounds such as trichlorohydrosilane. Examples of the Ge compound include GeO ₂ , GeO, alkoxy germanium compounds such as germanium tetramethoxide, and germanium tetraethoxide. Examples of the Pb compound include PbO ₂ , PbO, Pb ₂ O ₃ , Pb ₃ O ₄ , lead nitrate, lead carbonate, lead formate, lead acetate, lead tetraacetate, lead tartrate, lead diethoxide, lead di (isopropoxide) and the like. Can be mentioned. Examples of the P compound include phosphorus pentoxide, phosphorus oxychloride, phosphorus pentachloride, phosphorus trichloride, phosphorus tribromide, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, stannous pyrophosphate, boron phosphate and the like. Can be mentioned. Examples of the B compound include boron trioxide, boron trichloride, boron tribromide, boron carbide, boric acid, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, boron phosphide, boron phosphate and the like. Examples of the Al compound include aluminum oxide (α-alumina, β-alumina), aluminum silicate, aluminum tri-iso-propoxide, aluminum tellurite, aluminum chloride, aluminum boride, aluminum phosphide, aluminum phosphate, and lactic acid. Examples thereof include aluminum, aluminum borate, aluminum sulfide, aluminum sulfate, and aluminum boride. Examples of the Sb compound include diantimony trioxide, triphenylantimony and the like.

(4) Examples of Mg, Ca, Sr, and Ba compounds include oxides, hydroxides, carbonates, phosphates, sulfates, nitrates, and aluminum compounds.

(4) The firing condition is preferably a heating rate of 4 ° C to 2000 ° C per minute, more preferably 6 ° C to 2000 ° C. The temperature is particularly preferably 10 ° C or more and 2000 ° C or less, and the firing temperature is preferably 250 ° C or more and 1500 ° C or less, more preferably 350 ° C or more and 1500 ° C or less, and particularly preferably 500 ° C or more and 1500 ° C or less. And the calcination time is preferably from 0.01 hour to 100 hours, more preferably from 0.5 hour to 70 hours, particularly preferably from 1 hour to 20 hours, and The speed is preferably from 2 ° C. to 107 ° C. per minute, more preferably from 4 ° C. to 107 ° C., particularly preferably from 6 ° C. to 107 ° C., particularly preferably from 10 ° C. to 107 ° C. It is. The rate of temperature rise in the present invention is an average rate of temperature rise from “50% of firing temperature (displayed in ° C.)” to “80% of firing temperature (displayed in ° C.)”. This is the average rate of temperature decrease from "80% of firing temperature (expressed in ° C)" to "50% of firing temperature (expressed in ° C)". The temperature may be cooled in a baking furnace, or may be taken out of the baking furnace and put into, for example, water to cool. Also, a super-quenching method such as a gun method, a Hammer-Anvil method, a slap method, a gas atomizing method, a plasma spray method, a centrifugal quenching method, and a melt @ drag method described in page 217 of Ceramics Processing (Gihodo Publishing Co., Ltd. 1987) can be used. Alternatively, cooling may be performed using a single roller method or a twin roller method described in page 172 of the New Glass Handbook (Maruzen 1991). In the case of a material that melts during firing, a fired product may be continuously taken out while supplying raw materials during firing. In the case of a material that melts during firing, it is preferable to stir the melt.

The firing gas atmosphere is preferably an atmosphere having an oxygen content of 5% by volume or less, and more preferably an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, helium, krypton, xenon, and the like.

{The average particle size of the compounds represented by formulas (1) and (2) used in the present invention is preferably from 0.1 to 60 μm}, particularly preferably from 1.0 to 30 μm, and further preferably from 2.0 to 20 μm. In order to obtain a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling air jet mill, a sieve, and the like are used. At the time of pulverization, wet pulverization in the presence of water or an organic solvent such as methanol can also be performed if necessary. Classification is preferably performed to obtain a desired particle size. The classification method is not particularly limited, and a sieve, an air classifier, a drainage or the like can be used as necessary. Classification can be performed both in a dry type and a wet type.

More preferred lithium-containing transition metal oxide cathode materials used in the present invention include lithium compounds / transition metal compounds (where transition metals are Ti, V, Cr, Mn, Fe, Co, Ni, Mo, W It is preferable to mix and synthesize so that the total molar ratio of at least one selected) is 0.3 to 2.2. Particularly preferred lithium-containing transition metal oxide cathode materials used in the present invention include lithium compounds / transition metal compounds (where the transition metal is at least one selected from V, Cr, Mn, Fe, Co, and Ni). It is preferable to synthesize them by mixing them so that the total molar ratio becomes 0.3 to 2.2. Particularly preferred lithium-containing transition metal oxide cathode material used in the present invention is Lix QOy (where Q is mainly a transition metal containing at least one of Co, Mn, Ni, V and Fe, x = 0.2 ~ 1.2, y = 1.4 ~ 3). As Q, other than transition metals, Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, etc. may be mixed. The mixing amount is preferably 0 to 30 mol% based on the transition metal.

More preferred lithium-containing metal oxide cathode materials used in the present invention include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _a Ni _1-a O ₂ , and Li _x Co _b V _{1- b O z, Li x Co b} Fe 1-b O 2, Li x Mn 2 O 4, Li x Mn c Co 2-c O 4, Li x Mn c Ni 2-c O 4, Li x Mn c V 2 _{-c O 4, Li x Mn c} Fe 2-c O 4 ( wherein x = 0.7~1.2, a = 0.1~0.9, b = 0.8~0.98, c = 1.6 to 1.96, z = 2.01 to 2.3). The most preferred lithium-containing transition metal oxide cathode materials used in the present invention include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _a Ni _1-a O ₂ , and Li _x Mn ₂ O ₄ , Li _x Co _b V _1-b O _z (where x = 0.7 to 1.2, a = 0.1 to 0.9, b = 0.9 to 0.98, z = 2.01 to 2.3). The most preferred lithium-containing transition metal oxide cathode materials used in the present invention include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _a Ni _1-a O ₂ , and Li _x Mn ₂ O ₄ , Li _x Co _b V _1-b O _z (where x = 0.7-1.2, a = 0.1-0.9, b = 0.9-0.98, z = 2.02- 2.3). Here, the above-mentioned x value is a value before the start of charging and discharging, and increases or decreases due to charging and discharging.

導電 As the conductive carbon compound that can be used in the present invention, any electronic conductive material that does not cause a chemical change in the configured battery may be used. Specific examples include flake graphite, flake graphite, natural graphite such as earth graphite, petroleum coke, coal coke, celluloses, saccharides, high-temperature fired bodies such as mesophase pitch, and graphite such as artificial graphite such as vapor-grown graphite. Carbon blacks such as acetylene black, furnace black, ketjen black, channel black, lamp black and thermal black, asphalt pitch, coal tar, activated carbon, meso fuse pitch, polyacene and the like. Among these, graphite and carbon black are preferred. Non-carbon conductive agents include conductive fibers such as metal fibers, metal powders such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; and conductive metals such as titanium oxide. An oxide or the like may be included alone or a mixture thereof as necessary.

量 The amount of the conductive agent added to the mixture layer is preferably 6 to 50% by weight, and more preferably 6 to 30% by weight, based on the negative electrode material or the positive electrode material. In the case of carbon and graphite, the content is particularly preferably 6 to 20% by weight.

多 As the binder for holding the electrode mixture used in the present invention, a polysaccharide, a thermoplastic resin and a polymer having rubber elasticity or a mixture thereof can be used. Preferred binders include starch, carboxymethylcellulose, cellulose, diacetylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium alginate, polyacrylic acid, sodium polyacrylate, polyvinylphenol, polyvinylmethylether, polyvinyl alcohol, polyvinylpyrrolidone Water-soluble polymers such as polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene flow Ride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene (Meth) acrylic ester copolymers containing (meth) acrylic esters such as styrene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, and 2-ethylhexyl acrylate, and (meth) acrylic Acid ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene butadiene copolymer, acrylonitrile butadiene copolymer, polybutadiene, neoprene rubber, fluorine rubber, polyethylene oxide, polyester polyurethane Emulsion (latex) or suspension of resin, polyether polyurethane resin, polycarbonate polyurethane resin, polyester resin, phenol resin, epoxy resin, etc. It can be cited. In particular, polyacrylate latex, carboxymethyl cellulose, polytetrafluoroethylene, and polyvinylidene fluoride are preferred. These binders can be used alone or in combination. If the amount of the binder added is small, the holding power and cohesion of the electrode mixture is weak and the cyclability is poor, and if too large, the electrode volume increases and the volume per electrode unit volume or unit weight decreases, and further, The conductivity decreases and the capacity decreases. The amount of the binder added is not particularly limited, but is preferably 1 to 30% by weight, and particularly preferably 2 to 10% by weight.

調整 The adjustment of the negative electrode mixture or the positive electrode mixture paste of the present invention is preferably performed in an aqueous system. The mixture paste is prepared by first mixing the active material and the conductive agent, adding a binder (a suspension of resin powder or an emulsion (latex)) and water, and kneading and mixing. The dispersion can be carried out by a homogenizer, a dissolver, a planetary mixer, a paint shaker, a stirring mixer such as a sand mill, or a disperser. The prepared mixture paste of the positive electrode active material and the negative electrode active material is mainly used after being applied (coated) on a current collector, dried, and compressed. Coating can be performed by various methods, for example, a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method. I can do it. The blade method, the knife method and the extrusion method are preferred. The application is preferably performed at a speed of 0.1 to 100 m / min. At this time, by selecting the above-mentioned coating method in accordance with the liquid physical properties and drying properties of the mixture paste, a good surface state of the coating layer can be obtained. The thickness, length and width of the coating layer are determined according to the size of the battery, and the thickness of the coating layer is particularly preferably 1 to 2000 μm in a compressed state after drying.

As a drying or dehydrating method for removing moisture from the pellets and sheets, a generally employed method can be used, and hot air, vacuum, infrared rays, far infrared rays, electron beams, and low-humidity air can be used alone or in combination. Can be done. The temperature is preferably in the range of 80 to 350C, particularly preferably in the range of 100 to 250C. The water content is preferably 2,000 ppm or less in the whole battery, and is preferably 500 ppm or less in each of the positive electrode mixture, the negative electrode mixture and the electrolyte from the viewpoint of charge / discharge cycleability.

The compression of the sheet-like electrode mixture can be performed by a commonly used pressing method, but a die pressing method and a calendar pressing method are particularly preferable. The pressing pressure is not particularly limited, but is preferably from 10 kg / cm ^{2 to 3} t / cm ² . The press speed of the calender press method is preferably 0.1 to 50 m / min. The pressing temperature is preferably from room temperature to 200 ° C.

The support or current collector for the positive electrode and the negative electrode that can be used in the present invention is, as a material, the positive electrode is aluminum, stainless steel, nickel, titanium, or an alloy thereof, and the negative electrode is copper, stainless steel, nickel, titanium. Or alloys thereof, in the form of foil, expanded metal, punched metal, or wire mesh. In particular, an aluminum foil is preferable for the positive electrode, and a copper foil is preferable for the negative electrode.

The separator that can be used in the present invention has a high ion permeability, a predetermined mechanical strength, and may be any insulating thin film. As the material, olefin-based polymers, fluorine-based polymers, cellulose-based polymers, polyimides, nylons, Glass fiber and alumina fiber are used, and as a form, a nonwoven fabric, a woven fabric, or a microporous film is used. In particular, the material is preferably polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polypropylene and Teflon, and a mixture of polyethylene and Teflon, and the form is preferably a microporous film. In particular, a microporous film having a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferable.

The shape of the battery can be applied to any of buttons, coins, sheets, cylinders, corners, etc. A battery is formed by inserting an electrode wound with a pellet, a sheet, or a separator into a battery can, electrically connecting the can and the electrode, injecting an electrolyte, and sealing the battery. At this time, a safety valve can be used as a sealing plate. Further, it is preferable to use a PTC element in order to guarantee the safety of the battery.

Nickel-plated iron steel sheet, stainless steel sheet (SUS304, SUS304L, SUS304N, SUS316, SUS316L, SUS430, SUS444, etc.), and nickel-plated stainless steel sheet (same as above) can be used for the bottomed battery outer can that can be used in the present invention. , Aluminum or its alloys, nickel, titanium, and copper, and have a shape of a perfect circular cylinder, an elliptical cylinder, a square cylinder, or a rectangular cylinder. In particular, when the outer can also serves as the negative electrode terminal, a stainless steel sheet or a nickel-plated iron steel sheet is preferable, and when the outer can also serves as the positive electrode terminal, a stainless steel sheet, aluminum, or an alloy thereof is preferable.

シ ー ト The sheet-shaped mixture electrode is wound or folded and inserted into a can, the can and the sheet are electrically connected, an electrolyte is injected, and a battery can is formed using a sealing plate. At this time, a safety valve can be used as a sealing plate. In addition to the safety valve, various conventionally known safety elements may be provided. For example, a fuse, a bimetal, a PTC element, or the like is used as the overcurrent prevention element. In addition to the safety valve, as a countermeasure against the rise in the internal pressure of the battery can, a method of making a cut in the battery can, a gasket cracking method or a sealing plate cracking method can be used. Further, the charger may be provided with a circuit incorporating measures for overcharging and overdischarging.

The entire amount of the electrolyte may be injected at one time, but it is preferable to perform the injection in two or more steps. When the injection is performed in two or more steps, each liquid may have the same composition but different compositions (for example, after injecting a non-aqueous solvent or a solution in which a lithium salt is dissolved in a non-aqueous solvent, a non-aqueous solution having a higher viscosity than the solvent). A solution in which a lithium salt is dissolved in a solvent or a non-aqueous solvent is injected). Further, in order to reduce the electrolyte injection time, the pressure of the battery can may be reduced (preferably 500 to 1 torr, more preferably 400 to 10 torr), or centrifugal force or ultrasonic waves may be applied to the battery can. .

Electric conductive metals and alloys can be used for the can and the lead plate. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum or alloys thereof are used. Known methods (eg, DC or AC electric welding, laser welding, ultrasonic welding) can be used for welding the cap, can, sheet, and lead plate. A conventionally known compound or mixture such as asphalt can be used as the sealing agent for sealing.

The gasket that can be used in the present invention is, as a material, an olefin-based polymer, a fluorine-based polymer, a cellulose-based polymer, a polyimide, or a polyamide.From the viewpoint of organic solvent resistance and low moisture permeability, an olefin-based polymer is preferable. Polymers are preferred. Further, it is preferably a block copolymer of propylene and ethylene.

(4) The battery of the present invention is covered with an exterior material as necessary. Examples of the exterior material include a heat-shrinkable tube, an adhesive tape, a metal film, paper, cloth, paint, a plastic case, and the like. Further, at least a part of the exterior may be provided with a portion that changes color by heat so that the heat history during use can be recognized. The battery of the present invention is assembled in a battery pack in a plural number in series and / or parallel as required. In addition to safety elements such as positive temperature coefficient resistors, temperature fuses, fuses and / or current interrupting elements, battery packs have safety circuits (monitoring the voltage, temperature, current, etc. of each battery and / or assembled battery as a whole, Then, a circuit having a function of interrupting the current may be provided. In addition to the positive and negative terminals of each battery, the battery pack should have external terminals such as the positive and negative terminals of each battery, the temperature detection terminals of the entire battery and each battery, and the current detection terminals of the entire battery. You can also. The battery pack may include a voltage conversion circuit (such as a DC-DC converter). The connection of each battery may be fixed by welding a lead plate, or may be fixed by a socket or the like so that it can be easily detached. Further, the battery pack may be provided with a display function such as a remaining battery capacity, whether or not charging is performed, and the number of times of use.

電池 The battery of the present invention is used for various devices. In particular, video movies, portable VCRs with built-in monitors, movie cameras with built-in monitors, compact cameras, single-lens reflex cameras, film with lenses, notebook computers, notebook word processors, electronic organizers, mobile phones, cordless phones, hairdressers, electric tools, It is preferably used for electric mixers, automobiles and the like.

The present invention will be described in more detail with reference to specific examples below, but the present invention is not limited to the examples unless it exceeds the gist of the invention.

[Examples of preparing positive electrode mixture paste; Examples and Comparative Examples]
Positive electrode active material: LiCoO ₂ (a mixture of lithium carbonate and tricobalt tetroxide at a molar ratio of 3: 2 was placed in an alumina crucible, heated to 750 ° C. at 2 ° C./min in air, and calcined for 4 hours. Thereafter, the temperature is further raised to 900 ° C. at a rate of 2 ° C. per minute, and baked at that temperature for 8 hours to be crushed, and the conductivity of the dispersion when 50 g of the washed product is dispersed in 100 ml of water with a central particle size of 5 μm. Is 0.6 mS / m, pH is 10.1, specific surface area by nitrogen adsorption method is 0.42 m ² / g), 200 g of acetylene black is mixed with a homogenizer, and then 2-ethylhexyl is used as a binder. 8 g of an aqueous dispersion of a copolymer of acrylate, acrylic acid and acrylonitrile (solid content concentration: 50% by weight) and 60 g of a 2% by weight aqueous solution of carboxymethylcellulose were added, kneaded and mixed. The addition of 50 g, were agitated and mixed by a homogenizer to prepare a positive electrode mixture paste.
(Example of preparing negative electrode mixture paste)
Negative electrode active material: SnGe _0.1 B _0.5 P _0.58 Mg _0.1 K _0.1 O _3.35 (6.7 g of tin monoxide, 10.3 g of tin pyrophosphate, 1.7 g of diboron trioxide, 0.7 g of potassium carbonate, 0.4 g of magnesium oxide And 1.0 g of germanium dioxide were dry-mixed, placed in an alumina crucible, heated to 1000 ° C. at 15 ° C./min in an argon atmosphere, baked at 1100 ° C. for 12 hours, and then cooled to room temperature at 10 ° C./min. What was taken out of the firing furnace was collected and pulverized by a jet mill, and had an average particle size of 4.5 μm and a broad peak having a peak at around 28 ° in 2θ value by X-ray diffraction using CuKα ray. 200 g and a conductive agent (artificial graphite) 30 g were mixed with a homogenizer, and concentrated as a binder. A mixture of 50 g of a 2% by weight aqueous carboxymethylcellulose solution and 10 g of polyvinylidene fluoride and 30 g of water were further added and kneaded and mixed to prepare a negative electrode mixture paste.
[Preparation of positive and negative electrode sheets]
The above-prepared positive electrode mixture paste was applied on both surfaces of a 30 μm-thick aluminum foil current collector using a blade coater so that the coating amount was 400 g / m ² and the thickness of the compressed sheet was 280 μm, and then dried. Then, it was compression-molded by a roller press machine and cut into a predetermined size to prepare a belt-shaped positive electrode sheet. Further, in a dry box (dew point; dry air having a temperature of -50 ° C. or less), dehydration and drying were sufficiently performed by a far-infrared heater to prepare a positive electrode sheet. Similarly, the negative electrode mixture paste is applied to a 20 μm copper foil current collector, and a negative electrode sheet having a coating amount of 70 g / m ² and a compressed sheet thickness of 90 μm is prepared in the same manner as in the preparation of the positive electrode sheet. did.
[Examples of electrolyte adjustment (Examples 1 to 13)]
In an argon atmosphere, 65.3 g of diethyl carbonate was placed in a 200 cc narrow-neck polypropylene container, and 22.2 g of ethylene carbonate was dissolved therein little by little while taking care that the liquid temperature did not exceed 30 ° C. Next, 0.4 g of LiBF ₄ and 12.1 g of LiPF ₆ were each dissolved little by little in the above-mentioned polypropylene container in order while taking care that the liquid temperature did not exceed 30 ° C. The obtained electrolyte was a colorless and transparent liquid having a specific gravity of 1.135. Moisture is 18 ppm (measured using a Karl Fischer moisture meter, Model MKC-210, manufactured by Kyoto Electronics Co., Ltd.), and free acid content is 24 ppm (measured by neutralization titration using a 0.1 N NaOH aqueous solution using bromthymol blue as an indicator). )Met. Further, the compounds shown in Table 1 were dissolved in this electrolytic solution so as to have a predetermined concentration to prepare electrolytes.
[Example of creating a cylinder battery]
A positive electrode sheet, a separator made of a microporous polypropylene film, a negative electrode sheet and a separator were laminated in this order, and this was spirally wound. This wound body was housed in a nickel-plated iron bottomed cylindrical battery can also serving as a negative electrode terminal. Further, an electrolyte to which the additives described in Table 1 were added was injected into the battery can. A battery lid having a positive electrode terminal was caulked via a gasket to produce a cylindrical battery.

(Comparative Example 1)
In the same manner as in the example, a cylindrical battery was prepared using an electrolyte to which no additive was added.
(Comparative Examples 2-3 and Example 14)
In place of the oxide-based negative electrode active material, a negative electrode sheet was prepared using a carbon-based active material (graphite powder) in the same manner as in the preparation of the negative electrode sheet, and a cylindrical battery was prepared using each of the electrolytes in Table 1. .

The battery prepared by the above method was charged and discharged under the conditions of a current density of 5 mA / cm ² , a charge end voltage of 4.1 V, and a discharge end voltage of 2.8 V, and the discharge capacity and cycle life were determined. Table 1 shows the ratio of the capacity (Wh) of each battery and the cyclability (the ratio of the 300th capacity to the first charge / discharge).

The battery using the oxide-based negative electrode active material of the present invention has a larger capacity than the battery using the carbon-based negative electrode active material, and the battery using the electrolyte containing the N-containing organic compound has improved cycleability. The improvement rate is higher than that using the carbon-based negative electrode active material.

FIG. 1 shows a sectional view of a cylinder-type battery used in Examples.

Explanation of reference numerals

1 Gasket made of polypropylene 2 Negative electrode can (battery can) also serving as negative electrode terminal
DESCRIPTION OF SYMBOLS 3 Separator 4 Negative electrode sheet 5 Positive electrode sheet 6 Nonaqueous electrolyte 7 Explosion-proof valve body 8 Positive electrode cap which also serves as a positive electrode terminal 9 PTC element 10 Inner lid body 11 Ring

Claims (7)

(4) A non-aqueous electrolyte comprising a solvent and a lithium salt, wherein the electrolyte contains 0.0001 to 0.1 mol / l of an N-containing polycyclic fused compound with respect to the solvent. The N-containing polycyclic fused compound is 1,5-diazabicyclo [4.3.0] -5-nonene and / or 1,8-diazabicyclo [5.4.0] -7-undecene. The non-aqueous electrolyte according to claim 1. (3) The non-aqueous electrolyte according to (1) or (2), wherein the solvent contains a cyclic carbonate and / or a non-cyclic carbonate. The non-aqueous electrolyte according to claim 3, wherein the cyclic carbonate is ethylene carbonate and / or propylene carbonate, and the non-cyclic carbonate is at least one selected from diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. . The non-aqueous electrolyte according to claim 3, wherein the solvent contains ethylene carbonate and LiPF ₆ . (6) A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte according to any one of claims 1 to 5, each containing a material capable of reversibly inserting and extracting lithium. The material capable of reversibly storing and releasing lithium is LixQOy (where Q is mainly a transition metal containing at least one of Co, Mn, Ni, V, and Fe; x = 0.2 to 1.2, y = 1.4 to 3). The non-aqueous electrolyte secondary battery according to claim 6, wherein

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