KR20090111327A - Nonaqueous electrolyte solution and nonaqueous electrolyte secondary battery - Google Patents

Abstract

Disclosed is a nonaqueous electrolyte secondary battery which is good in high temperature storage characteristics even when it is charged to a high voltage. Also disclosed is a nonaqueous electrolyte solution which enables to obtain such a nonaqueous electrolyte secondary battery. Specifically disclosed is a nonaqueous electrolyte solution containing a nonaqueous solvent, an electrolyte salt and a sulfonate salt. The sulfonate salt is a compound having a branched ether skeleton in a molecule. Also specifically disclosed is a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator and the nonaqueous electrolyte solution. This nonaqueous electrolyte secondary battery is good in high temperature storage characteristics even when it is charged to a high voltage.

Description

Non-aqueous electrolyte and non-aqueous electrolyte secondary battery {NONAQUEOUS ELECTROLYTE SOLUTION AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY}

The present invention relates to a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery. More specifically, the present invention relates to a nonaqueous electrolyte solution containing a branched compound having an ether skeleton and a sulfonic acid metal base, and a nonaqueous electrolyte secondary battery which is excellent in high temperature storage even under high voltage. .

Lithium ion secondary batteries have characteristics such as high voltage (operating voltage 4.2V) and high energy density, and thus are widely used in the field of portable information equipment, and the demand is rapidly expanding. It is widely used as a standard battery for mobile information equipment including personal computers. Therefore, with high performance and multifunction of portable devices, higher performance (for example, higher capacity and higher energy density) is required for a lithium ion secondary battery as its power source. In order to meet this demand, various measures, for example, the densification by the improvement of the filling rate of an electrode, the expansion of the depth of charge of the active material (especially a negative electrode) of the present, the development of a high capacity new active material, etc. are examined. And in reality, the capacity of a lithium ion secondary battery is reliably increased by these measures.

Generally, this lithium ion secondary battery uses the nonaqueous electrolyte which melt | dissolved electrolyte salt in the non-aqueous solvent (organic solvent) as electrolyte solution (electrolyte). As a non-aqueous solvent, cyclic esters, such as ethylene carbonate, and chain esters, such as dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, and methyl propionate, have been mixed and used until now.

However, since an ester solvent (particularly, a chain carbonate ester) generates gas by oxidation or reduction with an electrode, in a lithium ion secondary battery having an electrolyte solution using an ester solvent, a high temperature (particularly 60 ° C or more) In storage at), battery expansion is likely to occur. In a lithium ion secondary battery having an operating voltage of about 4.2 V, the gas generation is not a problem, but it has room for improvement.

On the other hand, in order to further increase the capacity, it is required to improve the utilization rate of the positive electrode active material and to develop a high voltage material. Among them, the expansion of the depth of charge of the positive electrode active material due to the increase of the charge voltage is drawing attention. For example, cobalt composite oxide (LiCoO ₂ ), which is an active material of a lithium ion secondary battery of 4.2 V class, has a charging capacity of about 155 mAh / when it is charged to 4.3 V based on Li, which is a charging condition currently employed. g, when charged to 4.50V, it is about 190 mAh / g or more. Thus, the utilization rate of a positive electrode active material becomes large by the improvement of a charging voltage.

However, with increasing voltage of the battery, the capacity and energy density of the battery are improved, while the problem of deterioration of the safety and charge / discharge cycle characteristics of the battery, and gas generation at high temperature storage is about 4.2 V. It becomes remarkable compared with the case.

By the way, conventionally, the technique which solves the problem of the safety of a battery, the fall of a charge / discharge cycle, expansion of a battery, etc. is also proposed. For example, a non-aqueous electrolyte having a mixed solvent of a cyclic ester and a chain ester is used for a lithium ion secondary battery that has already been put into practical use. However, by adding an additive such as a specific cyclic sulfuric acid ester, Techniques for solving the above problems have been proposed (for example, JP-A-3760540, JP-A-2003-151623, JP-A-2003-308875, JP-A-2004-22523 and JP3658506). , Patent No. 3213459, Patent No. 3438636, and Japanese Patent Application Laid-Open No. 9-245834. When a lithium ion secondary battery having a nonaqueous electrolyte solution containing such an additive is charged, a dense film derived from the additive is formed on the surface of the negative electrode, and the coating continuously suppresses the reaction between the nonaqueous solvent and the negative electrode in the nonaqueous electrolyte solution. . Therefore, it is thought that the fall of the battery capacity and the expansion of a battery by gas generation which can be followed by the progress of a subsequent charge / discharge cycle can be suppressed, and the charge / discharge cycle characteristic of a battery can be improved.

By the way, in the technique disclosed in the said patent application, since the ion conductivity of the formed film is inadequate, the characteristic of a battery falls. Since the film is structurally unstable and repeats dissolution and growth of the film, the effect of suppressing expansion during high temperature storage is not necessarily sufficient. Moreover, when the potential of the positive electrode at the time of completion of charging of a battery turns into high voltage, such as 4.35V or more on Li reference | standard, only formation of the film | membrane derived from the said additive suppresses the fall of charge / discharge cycle characteristics, or high temperature. The expansion inhibition at the time of storage cannot be fully achieved.

An object of the present invention is to provide a nonaqueous electrolyte secondary battery having good high temperature storage characteristics even in a high voltage state of charge and a nonaqueous electrolyte that can be used in the nonaqueous electrolyte secondary battery.

In order to achieve the above object, the present invention provides a non-aqueous electrolyte which is a compound having a branched ether skeleton in a molecule in a non-aqueous electrolyte containing a non-aqueous solvent, an electrolyte salt, and a sulfonate.

Moreover, this invention provides the nonaqueous electrolyte secondary battery which has a positive electrode, a negative electrode, a separator, and the said nonaqueous electrolyte solution of this invention.

Generally, in a charged nonaqueous electrolyte secondary battery, since the metal oxide which is a positive electrode active material shows very strong oxidizing property in a high potential state, it reacts with the nonaqueous solvent used as a solvent of a nonaqueous electrolyte at the surface of a positive electrode, and decomposes it. Especially when charged at high voltage, this decomposition reaction is intensified. The decomposition reaction of such a non-aqueous solvent causes expansion when the non-aqueous electrolyte secondary battery filled with a high voltage is stored at high temperature.

MEANS TO SOLVE THE PROBLEM The present inventors paid attention to the branched compound which has an ether bond of a specific structure among various compounds, and examined in detail, The branched compound which introduce | transduced the short segment which has an ether bond into one molecule with the sulfonic acid metal base group was carried out. In a battery constructed using a non-aqueous electrolyte containing (sulfonic acid salt), it has been found that the above-mentioned branched compound reacts with the positive electrode to form a film on the surface of the positive electrode when charged, especially when charged at high voltage, thereby completing the present invention. It came to the following.

1 is a perspective view schematically showing an example of a nonaqueous electrolyte secondary battery of the present invention;

FIG. 2 is a schematic cross-sectional view taken along the line I-I of FIG. 1. FIG.

In the nonaqueous electrolyte of the present invention, sulfonates having a branched ether skeleton in the molecule are used. The compound having such a structure has a high oxidation potential, and since the protective film formed on the surface of the positive electrode by reacting the sulfonate with the positive electrode active material is structurally stable, the reaction between the positive electrode and the nonaqueous electrolyte can be prevented. .

According to another aspect, by introducing a segment having an ether bond into a branch of a molecule having a branched structure, the cation constituting the sulfonic acid metal base is easily ionized, and the ion conductivity of the protective film formed on the surface of the anode is improved. do. Therefore, the bad influence on the load characteristic of a battery, etc. can be suppressed. The sulfonate also reacts at the negative electrode.

According to another aspect, the viscosity of the branched compound itself and the like can be controlled by controlling the molecular structure of the sulfonate.

The branched ether skeleton of the sulfonate preferably contains an ether bond represented by the following general formula (1).

In the general formula (1), R is an alkylene group having 2 to 4 carbon atoms, a part or all of the hydrogen atoms of these groups being optionally substituted with a fluorine atom, in particular an ethylene group (-CH ₂ CH ₂ -) is preferred Do. When the sulfonate dissolved in the nonaqueous electrolyte solvent forms a film, but the carbon number of R is 5 or more, the solubility of the sulfonate in the nonaqueous electrolyte solvent may decrease, and the film may be difficult to be formed. Since it affects the ionic conductivity of the film formed, it is preferable that carbon number is four or less.

In said general formula (1), R 'is a C1-C6 alkyl group; An alkylene group having 1 to 6 carbon atoms bonded to -SO ₃ M '(M' is an alkali metal) or a crown ring; Or a crown ring, and part or all of hydrogen atoms may be substituted with fluorine atoms, and methyl group (-CH ₃ ), ethyl group (-CH ₂ CH ₃ ), or propyl group (-CH ₂ CH ₂ CH ₃ ) is particularly preferable. Do.

R 'is an alkyl group; Or in the case of the alkylene group couple | bonded with a functional group, when carbon number of an alkyl group or an alkylene group becomes too large, the solubility of a sulfonate in the nonaqueous electrolyte solvent may fall, and a film may become difficult to form. Moreover, since carbon number of an alkyl group affects the ionic conductivity of the film formed, it is preferable that the carbon number is 6 or less.

When R 'includes a crown ring, the crown ring may be a 12-membered ring, a 15-membered ring, an 18-membered ring, or the like. In the case where the nonaqueous electrolyte contains lithium salt as the electrolyte salt, if the crown ring is a 12-membered ring, lithium ions are easily replenished with the ring, and if the crown ring is a large crown ring of 15 or more members, lithium ions pass through the ring. Easier The crown ring may have a cyclic structure in which part or all of its oxygen atoms are substituted with sulfur atoms or nitrogen atoms.

In the general formula (1), m represents the length of the ether skeleton. When m is larger than 10, since sulfonate becomes easy to precipitate as crystal | crystallization, or solubility to a solvent may fall, it is preferable that the value of m is an integer of 1-10.

Moreover, the structure of the part related to the sulfonic acid metal base in the said sulfonate, Preferably, it is a structure shown by following General formula (2).

In the general formula (2), M represents an alkali metal (for example, Li, Na, K, and the like), preferably Li, and R ¹ has 1 to 8 carbon atoms and an alkylene group or aromatic group. A substituent having a ring, and some or all of the hydrogen atoms of these groups may be substituted with fluorine atoms.

In addition, in said General formula (2), when R <^1> is a C1-C6 alkylene group, the structure represented by the said General formula (2) is -O-R 'in the said General formula (1). It can also be introduced as.

Moreover, it is preferable that the said sulfonate has an ether bond represented by following General formula (3), and it is more preferable that it is a dendron specifically, shown by following General formula (4). Here, a dendron means the branched compound of the form extended in only one direction, or the branched compound of the fan shape.

In said general formula (3) and (4), R <^2> is a C1-C3 saturated hydrocarbon group, R <^3> and R <^4> is the same or different, and is a C2-C4 alkylene group. In addition, R <^5> and R <^6> is the same or different, and is a C1-C6 alkyl group; An alkylene group having 1 to 6 carbon atoms bonded to -SO ₃ M '(M' is an alkali metal) or a crown ring; Or a crown ring. Moreover, n is an integer of 1-4, o and p are the same or different, and are an integer of 0-10. However, since it is preferable that at least one of the structures represented by -R <^3> -O- and -R <^4> -O- is contained in the said General formula (3) and (4), at least one of o and p is 1 It is preferable to make it the above.

R ² , R ³ , R ⁴ , R ⁵ and R ⁶ may be substituted with some or all of the hydrogen atoms by fluorine atoms, and in the crown ring, some or all of the oxygen atoms are sulfur or nitrogen atoms. A substituted cyclic structure may be sufficient. In addition, in the said General formula (4), M and R <^1> have the same meaning as the case of the said General formula (2).

In the general formulas (3) and (4), n represents a repeated number of branched structures in parentheses. For example, in the case of n = 2 in the general formula (3), the general formula (3) This structure is represented by the following structural formula.

In said structural formula, R <^2a> , R <^2b> and R <^2C> is the same or different, and is a C1-C3 saturated hydrocarbon group. R <^3a> , R <^3b> , R <^4a> and R <^4b> is the same or different, and is a C2-C4 alkylene group, and some or all of the hydrogen atoms of these groups may be substituted by the fluorine atom.

R <^5a> , R <^5b> , R <^6a> and R <^6b> are the same or different, and are a C1-C6 alkyl group; An alkylene group having 1 to 6 carbon atoms bonded to -SO ₃ M '(M' is an alkali metal) or a crown ring; Or a crown ring, and part or all of the hydrogen atoms of these groups may be substituted with fluorine atoms.

o ¹ , o ² , p ¹ and p ² are the same or different and represent an integer of 0 to 10.

In the ether bond represented by the general formula (3) and the sulfonate salt represented by the general formula (4), the case where n is 3 or 4 may be considered the same as above, and the ether bond in the molecule The number of branches in the structure increases.

In the ether bond represented by the general formula (3) and the sulfonate represented by the general formula (4), when n is greater than 4, the synthesis of the sulfonate becomes difficult, so that n is preferably 4 or less. Moreover, it is especially preferable that n is 1 or 2 from affinity with respect to a non-aqueous solvent and electrolyte salt, or an ionic conductivity.

Moreover, in the said General formula (3), an example of the structure in the case where R <^5> and R <^6> is an alkylene group couple | bonded with a crown ring is shown below.

In the sulfonate salt of the present invention, the structure of the branched ether skeleton portion is preferably a structure represented by the following general formula (5), and more specifically, a sulfonate salt having a structure represented by the following general formula (6) Particularly preferred.

In the general formulas (5) and (6), q is 1 or 2, and r represents an integer of 1 to 10. In General Formula (6), M and R ¹ have the same meaning as in the case of General Formula (2).

In addition, q in the said General formula (5) and (6) is also a numerical value which shows the number of iterations of the branch structure in parentheses similarly to n in the said General formula (3) and (4).

The content of the sulfonate in the nonaqueous electrolyte of the present invention is preferably 0.05% by mass or more and more preferably 0.1% by mass or more in the total amount of the nonaqueous electrolyte from the viewpoint of more effectively exerting the action of the sulfonate. In addition, when the content of the sulfonate in the nonaqueous electrolyte is too high, the viscosity of the nonaqueous electrolyte may be too high, so that the load characteristics of the battery may decrease, and the cost of the nonaqueous electrolyte is also high. It is mass% or less, More preferably, it is 3 mass% or less.

Since the sulfonate salt of the present invention having both an ether skeleton and a sulfonic acid metal base in a molecule has a short ether segment and a branched structure, it is possible to use a compound which is a liquid at room temperature despite the high molecular weight by controlling the molecular structure. It is possible to make an ionic liquid. Moreover, this sulfonate has high affinity with a non-aqueous solvent and electrolyte salt, and can form a protective film of high ionic conductivity on the surface of the positive electrode.

That is, in the battery using the nonaqueous electrolyte of the present invention containing the sulfonate, the sulfonate metal base of the sulfonate first reacts with the positive electrode active material, whereby a protective film including a branched structure composed of ether bonds is formed on the surface of the positive electrode. . Since this protective film has high ion conductivity and is structurally stable, it is possible to prevent the reaction between the positive electrode and the non-aqueous electrolyte and to suppress the expansion of the battery. As a result, the high temperature storage characteristics of the battery (particularly in a high voltage state of charge) Can be effectively improved.

The method for synthesizing the sulfonate is not particularly limited and may be any method capable of synthesizing a compound having a branched ether bond and a sulfonic acid metal base in one molecule. For example, an aliphatic oligoether dendron having a sulfonic acid metal base is first synthesized in two steps using an aliphatic oligoether dendron having a hydroxyl group as a starting material of a corresponding alcohol and epichlorohydrin. The aliphatic oligoether dendron having a hydroxyl group of can be synthesized by alkoxylation and reacting with sultone.

As the non-aqueous solvent (organic solvent) used in the nonaqueous electrolyte of the present invention, a high dielectric constant is preferable, and esters containing carbonates are more preferable. Especially, it is especially preferable to use the ester whose dielectric constant is 30 or more. Examples of such high dielectric constant esters include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and sulfur esters (such as ethylene glycol sulfite). Among these, cyclic esters are preferable, and cyclic carbonates such as ethylene carbonate, vinylene carbonate, propylene carbonate and butylene carbonate are particularly preferable. In addition to the foregoing, low viscosity polar chain carbonates and branched aliphatic carbonate compounds such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate can be used. Particular preference is given to a mixed solvent of ethylene carbonate and chain carbonate of the cyclic carbonate.

Moreover, in addition to said non-aqueous solvent, Chain alkyl esters, such as methyl propionate; Chain-like phosphoric acid triesters such as trimethyl phosphate; Nitrile solvents such as 3-methoxy propionitrile; Branched compounds which have an ether bond represented by a dendrimer and a dendron; Non-aqueous solvents (organic solvent), such as these, can be used.

Fluorine-containing solvents can also be used. Examples of the fluorine-containing solvent include the following compounds. H (CF ₂ ) ₂ OCH ₃ , C ₄ F ₉ OCH ₃ , H (CF ₂ ) ₂ OCH ₂ CH ₃ , H (CF ₂ ) ₂ OCH ₂ CF ₃ , H (CF ₂ ) ₂ CH ₂ O (CF ₂ ) ₂ H or the like, or a straight chain (perfluoroalkyl) alkyl ether such as CF ₃ CHFCF ₂ OCH ₃ , CF ₃ CHFCF ₂ OCH ₂ CH ₃ , or iso (perfluoroalkyl) alkyl ether, that is, 2- Trifluoromethyl hexafluoropropyl methyl ether, 2-trifluoromethyl hexafluoropropyl ethyl ether, 2-trifluoromethyl hexafluoropropyl propyl ether, 3-trifluoro octafluoro butylmethyl ether, 3 Trifluoro octafluoro butylethyl ether, 3-trifluoro octafluoro butylpropyl ether, 4-trifluoro decafluoro pentylmethyl ether, 4-trifluoro decafluoro pentylethyl ether, 4-triple Loro decafluoro pentylpropyl ether, 5-trifluororod decafluoro hexylmethyl ether, 5-trifluororod decafluoro hexylethyl ether, 5-trifluororod decafluoro hexylpropyl Ether, 6-trifluoro tetradecalofluoro heptylmethyl ether, 6-trifluoro tetradecafluoro heptylethyl ether, 6-trifluoro tetradecafluoro heptylpropyl ether, 7-trifluoro hexadecafluoro Octylmethyl ether, 7-trifluoro hexadecafluoro octylethyl ether, 7-trifluoro hexadecafluoro hexyl octyl ether and the like. Moreover, said iso (perfluoro alkyl) alkyl ether and said linear (perfluoro alkyl) alkyl ether can also be used together.

Electrolyte salt used for the nonaqueous electrolyte of this invention, Preferably, alkali metal salts (for example, lithium salt), such as an alkali metal perchlorate, an organoboron alkali metal salt, the alkali metal salt of a fluorine-containing compound, an alkali metal imide salt, etc. to be. Specific examples of such electrolyte salts include MClO ₄ (M represents an alkali metal element such as Li, Na, K, and the like below), MPF ₆ , MBF ₄ , MAsF ₆ , MSbF ₆ , MCF ₃ SO ₃ , MCF ₃ CO ₂ , M ₂ C ₂ F ₄ (SO ₃ ) ₂ , MN (CF ₃ SO ₂ ) ₂ , MN (C ₂ F ₅ SO ₂ ) ₂ , MC (CF ₃ SO ₂ ) 3, MCnF _{2n +1} SO ₃ n ≧ 2), MN (RfOS0 ₂ ) ₂ , wherein Rf is a fluoroalkyl group, and the like. The compound whose M in these compounds is a lithium element is more preferable, and a fluorine-containing organic lithium salt is especially preferable. This is because the fluorine-containing organic lithium salt is easy to dissolve in the nonaqueous electrolyte because of its high anionicity and easy ion separation.

The concentration of the electrolyte salt in the nonaqueous electrolyte is usually 0.3 mol / l or more, more preferably 0.7 mol / l or more, 1.7 mol / l or less, and more preferably 1.2 mol / l or less. If the electrolyte salt concentration is too low, the ionic conductivity may be reduced. If the electrolyte salt concentration is too high, the electrolyte salt that is not completely dissolved may precipitate.

Moreover, you may add the various additive which can improve the performance of the battery using this to the nonaqueous electrolyte of this invention.

For example, in the nonaqueous electrolyte solution to which the compound which has a C = C unsaturated bond in the molecule was added, the fall of the charge / discharge cycle characteristic of the battery using this may be suppressed. Such examples of the compound having a C = C unsaturated bond in the molecule, an aromatic compound such as _{C 6 H 5 C 6 H 11} ( cyclohexyl benzene); Fluorinated aliphatic compounds such as H (CF ₂ ) ₄ CH ₂ OOCCH = CH ₂ , F (CF ₂ ) ₈ CH ₂ CH ₂ OOCCH = CH ₂ ; Fluorine-containing aromatic compounds; Etc. can be mentioned. In addition, compounds having sulfur elements such as 1,3-propanesultone, 1,2-propanediol sulfate esters (for example, chain or cyclic sulfonic acid esters, chain or cyclic sulfuric acid esters, etc.) or vinyl Lencarbonate etc. can also be used. In particular, when a high crystalline carbon material is used for the negative electrode active material, vinylene carbonate is preferably used. As for the addition amount of these various additives, 0.05-5 mass% is preferable in the nonaqueous electrolyte whole quantity.

In addition, in order to improve the high temperature characteristic of a nonaqueous electrolyte secondary battery, you may add an acid anhydride to the nonaqueous electrolyte of this invention. The acid anhydride contributes to the formation of the composite film on the surface of the negative electrode as a surface modifier of the negative electrode, and further has a function of further improving the storage characteristics of the battery at high temperatures. In addition, since the amount of water in the nonaqueous electrolyte can be reduced by adding an acid anhydride to the nonaqueous electrolyte, the amount of gas generated in the battery using the nonaqueous electrolyte can also be reduced. The kind of acid anhydride added to the non-aqueous electrolyte is not particularly limited, and may be a compound having at least one acid anhydride structure in the molecule, or a compound having a plurality of acid anhydrides. Specific examples of the acid anhydride include, for example, methalic anhydride, malonic anhydride, maleic anhydride, butyric anhydride, propionic anhydride, fruconic anhydride, phthalic anhydride, phthalic anhydride, pyromellitic anhydride, anhydrous acid, and anhydride. Phthalic anhydride, toluic anhydride, thiobenzoic anhydride, diphenic anhydride, citraconic anhydride, diglycolic anhydride, acetic anhydride, amber anhydride, cinnamic anhydride, glutaric anhydride, glutaconic anhydride, anhydrous acetic anhydride Phenolic acid, isobutyric anhydride, isogilonic anhydride, benzoic anhydride, etc. can be mentioned, and these 1 type, or 2 or more types can be used. Moreover, as for the addition amount of the acid anhydride in the nonaqueous electrolyte solution of this invention, 0.05-1 mass% is preferable in the nonaqueous electrolyte whole quantity.

The nonaqueous electrolyte secondary battery of this invention should just have the nonaqueous electrolyte liquid of this invention, and there is no restriction | limiting in particular about other components, The same thing as a conventionally well-known nonaqueous electrolyte secondary battery can be employ | adopted.

Lithium ions may be introduced and released into the positive electrode active material relating to the positive electrode, for example, Li _x M0 ₂ or Li _y M ₂ 0 ₄ (wherein M is a transition metal and 0 ≦ x And lithium-containing composite oxides represented by ≦ 1, 0 ≦ y ≦ 2), spinel oxides, and metal chalcogenides having a layered structure. Specific examples thereof include lithium cobalt oxide such as LiCoO ₂ , lithium manganese oxide such as LiMn ₂ O ₄ , lithium nickel oxide such as LiNiO ₂ , lithium titanium oxide such as Li _4/3 Ti _5/3 O ₄ , lithium manganese Metal oxides such as nickel composite oxide, lithium manganese, nickel cobalt composite oxide, manganese dioxide, vanadium pentoxide, and chromium oxide; Metal sulfides such as titanium disulfide and molybdenum disulfide; Etc. can be mentioned.

Specifically, layer-structured or lithium-containing complex oxide of the spinel structure are preferably _{used, LiCoO 2, LiMn 2 O 4} , LiNiO 2, LiNi 1/2 Mn 1/2 O 2 Li-Mn, represented by such as, nickel composite oxide, _{LiNi 1/3 Mn 1/3} Co 1/3 O 2 , or _{LiNi 0 .6 Mn 0 .2 Co 0} .2 O 2 , represented by a lithium nickel-manganese-cobalt composite oxide, or LiNi _{1 -xy- z} Co Some of the constituent elements, such as _x Al _y Mg _z 0 ₂ (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, 0 ≤ z ≤ 0.1, 0 ≤ 1-xyz ≤ 1) are Ge, Ti, Zr, Mg More preferably, a lithium composite oxide having an opening voltage at charge of 4 V or more on a Li basis, such as a lithium-containing composite oxide substituted with an additive element selected from Al, Mo, Sn, and the like, is charged. When using a lithium composite oxide having an open circuit voltage of 4 V or more on a Li basis as a positive electrode active material, the characteristics of the nonaqueous electrolyte of the present invention in which oxidation under high voltage is suppressed can be utilized, and the nonaqueous electrolyte 2 of high energy density can be utilized. A car battery can be obtained.

These positive electrode active materials may be used independently and may use 2 or more types together. For example, by using a lithium-containing composite oxide having a layered structure and a lithium-containing composite oxide having a spinel structure together, it is possible to simultaneously achieve high capacity and safety.

The positive electrode for constituting the nonaqueous electrolyte secondary battery may be, for example, a conductive assistant such as carbon black or acetylene black, or a binder of polyvinylidene fluoride, polyethylene oxide, or the like. A positive electrode mixture is prepared by appropriately adding the agent and the like, which is obtained by using a current collector made of aluminum foil or the like as a core material to form a strip-shaped molded body. However, the manufacturing method of a positive electrode is not limited only to the thing of the said illustration.

As a negative electrode active material in the negative electrode for configuring the organic electrolyte secondary battery of the present invention, for example, a lithium metal or a compound capable of occluding and discharging lithium can be used. For example, alloys such as Al, Si, Sn, In, or various materials such as oxides and carbon materials capable of charging and discharging at low potentials close to lithium (Li) can also be used as the negative electrode active material. In the nonaqueous electrolyte secondary battery of the present invention, as the negative electrode active material, a carbon material capable of electrochemically introducing lithium ions is particularly preferable. Examples of such carbon materials include graphite, pyrolytic carbons, cokes, glassy carbons, sintered bodies of organic polymer compounds, meso carbon microbeads, carbon fibers, activated carbon, and the like.

When using a carbon material for the negative electrode active material, the interlayer distance d ₀₀₂ of the (002) plane of the carbon material is preferably 0.37 nm or less. In order to realize high capacity of the battery, d ₀₀₂ is more preferably 0.35 nm or less, and more preferably 0.34 nm or less. The lower limit of d ₀₀₂ is not particularly limited, but is theoretically about 0.335 nm.

Moreover, the magnitude | size Lc of the crystallite of c-axis direction of a carbon material becomes like this. Preferably it is 3 nm or more, More preferably, it is 8 nm or more, More preferably, it is 25 nm or more. Although the upper limit of Lc is not specifically limited, Usually, it is about 200 nm. And the average particle diameter of a carbon material becomes like this. Preferably it is 3 micrometers or more, More preferably, it is 5 micrometers or more, Preferably it is 15 micrometers or less, More preferably, it is 13 micrometers or less. Moreover, the purity becomes like this. Preferably it is 99.9% or more.

The negative electrode is, for example, a negative electrode prepared by appropriately adding a conductive aid (carbon black, acetylene black, etc.) or a binder (polyvinylidene fluoride, styrene butadiene rubber, etc.) to the negative electrode active material or the negative electrode active material, as necessary. The mixture is produced by completing a molded body using a current collector material such as copper foil as a core material. However, the manufacturing method of a negative electrode is not limited only to what was illustrated above.

In the nonaqueous electrolyte secondary battery of the present invention, the separator for separating the positive electrode and the negative electrode is also not particularly limited, and various separators employed in conventionally known nonaqueous electrolyte secondary batteries can be used. For example, microporous separators composed of polyolefin resins such as polyethylene and polypropylene and microporous separators composed of polyester resins such as polybutylene terephthalate are suitably used. The thickness of the separator is not particularly limited, but is preferably 5 µm or more and 30 µm or less in consideration of both battery safety and high capacity.

In the nonaqueous electrolyte secondary battery of the present invention, for example, the positive electrode and the negative electrode are overlapped with each other via the separator to form a laminated electrode body, or the wound electrode body is rolled up to be a wound electrode body, and then charged in an external body. The cathode and the anode / cathode terminals of the exterior body are connected via a lead body or the like, and the nonaqueous electrolyte solution of the present invention is injected into the exterior body, and then the exterior body is sealed.

As a battery exterior body, the exterior body made of metal squares, cylinders, etc., the laminated exterior body which consists of metal (aluminum etc.) laminated films, etc. can be used.

In addition, the manufacturing method of the nonaqueous electrolyte secondary battery and the structure of the battery are not particularly limited, but when a carbon material having a d ₀₀₂ of 0.34 nm or less is used as the negative electrode active material, the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte are accommodated in the exterior. It is preferable to set an open chemical conversion process for charging after the battery is completely sealed afterwards. Thereby, the gas which generate | occur | produces in the initial stage of charge, and the residual moisture in a battery can be removed out of a battery. After the chemical conversion, the method of removing the gas in the battery is not particularly limited, and may be either natural removal or vacuum removal. In addition, before the battery is completely sealed, the battery may be appropriately molded by pressurization or the like.

Since the nonaqueous electrolyte secondary battery of the present invention has excellent safety and good battery characteristics, the nonaqueous electrolyte secondary battery can be utilized not only as a secondary battery for driving power sources for mobile information devices such as mobile phones and notebook computers, but also with various characteristics. It can be widely used as a power supply for equipment.

EXAMPLE

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on an Example. However, the following Examples do not limit the present invention, and all modifications and changes without departing from the spirit and scope of the present invention are included in the technical scope of the present invention.

<Synthesis of sulfonates A, B and C>

Sulfonates A, B and C, which are dendrons having a branched ether skeleton and sulfonic acid metal bases, were synthesized. The structures of sulfonates A, B and C are shown in the following formula (7). In formula (7), sulfonate A is n = 0, sulfonate B is n = 1, and sulfonate C is n = 2.

Sulfonate A:

First, by the following process 1 and 2, the compound of the structure shown by following formula (8) [n = 0 in following formula (8)] is synthesize | combined, and it uses following compound 3 by following process 3 Sulfonate A was synthesized.

(Step 1) In a 2000 ml nas flask, 200 ml of epichlorohydrin and 200 ml of methanol were mixed, and a solution obtained by dissolving 16.85 g of potassium hydroxide in 320 ml of methanol was cooled in an ice bath. Slowly dropping. After stirring for 19 hours at room temperature, the mixture was filtered and distilled off under reduced pressure while heating the low boiling point component in the filtrate at 60 ° C to obtain a yellow liquid. In order to remove the structural isomer of the target product which is a by-product, 5.0 g of epichlorohydrin is added to the said yellow liquid, and it stirred at 60 degreeC for 5 hours, and then distilled under reduced pressure (80.2 degreeC / 28mmHg), and 193.57g 1, 3-dimethoxy-2-propanol was isolated as a colorless liquid.

1, 3-dimethoxy-2-propanol:

¹ H-NMR (CDCl ₃ ): δ 2.89 (dd), 3.39 (s, 6H), 3.41-3.48 (m, 4H), 3.96 (m, 1H);

¹³ C-NMR (CDCl ₃ ): δ 59.2 (s), 69.3 (s), 73.84 (s)

(Step 2) In a 500 ml nas flask, 13.4 ml of epichlorohydrin and tetrahydrofuran (THF) were mixed, and 11.34 g of potassium hydroxide was isolated from Step 1 in 1,3-dimethoxy. The solution dissolved in 210 g of 2-propanol was slowly added dropwise. After stirring at 100 degreeC for 29 hours, it filtered and the low boiling point component in the filtrate was distilled off under reduced pressure, and the pink liquid was obtained. After recovering 1, 3-dimethoxy-2-propanol by distilling this pink liquid under reduced pressure (85.0 degreeC / 39mmHg), and distilling under reduced pressure (101.6 degreeC / 0.08mmHg), 12.9g of compound a [1 , 3-bis (1, 3-dimethoxy-2-propoxy) -2-propanol] was isolated as a colorless liquid.

Compound a:

¹ H-NMR (CDCl ₃ ): δ 3.37 (s, 12H), 3.42-3.49 (m, 8H), 3.59-3.63 (m, 4H), 3.65-3.71 (m, 2H), 3.92-3.96 (m , 1H);

¹³ C-NMR (CDCl ₃ ): δ 59.22 (d), 69.86 (s), 72.00 (s), 72.73 (d), 78-60 (s)

(Step 3) In a 300 ml volume nas flask with nitrogen atmosphere, 6.61 g of compound a was dissolved in 100 ml of dehydrated THF. After 13.5 ml of n-butyl lithium hexane solutions of 1.57 M were dripped here, it stirred by heating at 60 degreeC for 12 hours. Thereafter, the solution in the flask was allowed to cool to room temperature, and 1.95 ml of 1,3-propanesultone was added thereto, followed by heating and stirring at 60 ° C for 4 days. The obtained reaction mixture was filtrated, and the filtrate was concentrated by evaporation to obtain a crude product. This crude product was purified by gel filtration chromatography using methanol as the eluent to obtain 6.30 g of sulfonate A as a viscous yellow liquid.

 Sulfonate A:

¹ H-NMR (CDCl ₃ ): δ2.08 (m, 2H), 3.02 (t, 2H), 3.37 (s, 6H), 3.39 (s, 6H), 3.44-3.50 (m, 8H), 3.61- 3.79 (m, 9 H);

¹³ C-NMR (CDCl ₃ ): δ 25.03 (s), 47.84 (s), 59.27 (d), 68.77 (s), 69.14 (s), 72.11 (s), 77.56 (s), 77.82 (s)

Sulfonate B:

First, by the following process 1 and 2, the compound b [n = 1 in the said Formula (8)] of the structure shown by the said Formula (8) is synthesize | combined, and it uses the compound b by the following process 3 Sulfonate B was synthesized.

(Step 1) In a 2000 ml nas flask, 120 ml of epichlorohydrin and 300 ml of THF were mixed, and the mixture of 90.78 g of potassium hydroxide dissolved in 725 ml of 2-methoxyethanol was cooled by an ice bath. Slowly dropping. After stirring for 15 hours at room temperature and 32 hours at 90 ° C, 8.05 g of potassium hydroxide was added and heated at 90 ° C for 19 hours. The obtained reaction mixture was filtered, and the low boiling point component in the filtrate was distilled off under reduced pressure. 7.42 g of potassium hydroxide was dissolved in the obtained liquid, 10.64 g of epichlorohydrin was added, and the mixture was heated at 140 ° C for 29 hours. The reaction mixture was filtered, and the filtrate was distilled under reduced pressure (109.3 ° C / 0.8 mmHg) to isolate 1,3-di (2-methoxyethoxy) -2-propanol as a colorless liquid.

1, 3-di (2-methoxyethoxy) -2-propanol:

¹ H-NMR (CDCl ₃ ): δ 2.99 (s, 1H), 3.39 (s, 6H), 3.49-3.60 (m, 8H), 3.65-3.67 (m, 4H), 4.01 (m, 1H);

¹³ C-NMR (CDCl ₃ ): δ 59.02 (s), 69.44 (s), 70.73 (s), 71.90 (s), 72.59 (s)

(Step 2) In a 500 ml nas flask, 8.8 ml of epichlorohydrin and 25 ml of THF were mixed, and 7.47 g of potassium hydroxide was isolated from Step 1 to 3-di (methoxy). The solution dissolved in 228 g of methoxy) -2-propanol was slowly added dropwise. After stirring at 140 ° C. for 29 hours, the mixture was neutralized with hydrochloric acid. The reaction mixture was filtered, and the low boiling point component in the filtrate was distilled off under reduced pressure to obtain an orange liquid. After recovering 1, 3-di (2-methoxyethoxy) -2-propanol by distilling this orange liquid under reduced pressure (142.4 degreeC / 0.1mmHg), and distilling under reduced pressure (275 degreeC / 0.1mmHg) again, 8.85 g of compound b [1, 3-bis [1, 3-di (2-methoxyethoxy) -2-propoxy] -2-propanol] was isolated as a colorless liquid.

Compound b:

¹ H-NMR (CDCl ₃ ): δ 3.38 (s, 12H), 3.46-3.57 (m, 16H), 3.59-3.66 (m, 8H), 3.68 (d, 4H), 3.70-3.76 (m, 2H ), 3.92 (m, 1 H);

¹³ C-NMR (CDCl ₃ ): δ 59.03 (s), 69.76 (s), 70.73 (d), 71.42 (d), 71.88 (d), 72.06 (s), 78.70 (s)

(Step 3) In a 300 ml volume nas flask with nitrogen atmosphere, 7.47 g of compound b was dissolved in 150 ml of dehydrated THF. After 9.6 ml of n-butyl lithium hexane solutions of 1.57 M were dripped here, it stirred by heating at 60 degreeC for 12 hours. Thereafter, the solution in the flask was allowed to cool to room temperature, and 1.95 ml of 1,3-propanesultone was added thereto, followed by heating and stirring at 60 ° C for 4 days. The obtained reaction mixture was filtered, and the filtrate was concentrated by evaporation to give a crude product. This crude product was purified by gel filtration chromatography using methanol as the eluent to obtain 4.68 g of sulfonate B as a viscous yellow liquid.

Sulfonate B:

¹ H-NMR (CDCl ₃ ): δ 2.07 (m, 2H), 3.01 (t, 2H), 3.39 (s, 12H), 3.54-3.82 (m, 33H);

¹³ C-NMR (CDCl ₃ ): δ 25.23 (s), 48.11 (s), 59.03 (s), 68.23 (s), 69.47 (s), 70.49 (s), 70.91 (d), 71.64 (d) , 77.54 (s), 77.94 (s)

Sulfonate C:

First, by the following process 1 and 2, the compound c [n = 2 in the said Formula (8)] of the structure shown by said Formula (8) is synthesize | combined, and it uses following compound 3 by the following process 3 Sulfonate C was synthesized.

(Step 1) In a 2000 ml nas flask, 80 ml of epichlorohydrin and 400 ml of THF were mixed, and 66.77 g of potassium hydroxide was dissolved in 725 ml of 2- (2-methoxyethoxy) ethanol in the mixture. The solution was slowly added dropwise. After stirring for 19 hours at room temperature, the mixture was refluxed for 24 hours. The obtained reaction mixture was filtered, and the low boiling point component in the filtrate was distilled off under reduced pressure. 168 g of 1, 3-bis (3,6-dioxa-1-heptoxy) -2-propanol was isolated as a colorless liquid by distillation under reduced pressure (109.3 ° C / 0.8 mmHg).

The NNR data of the obtained 1, 3-bis (3, 6-dioxa-1-heptoxy) -2-propanol are as follows.

¹ H-NMR (CDCl ₃ ): δ 3.19 (s, 1H), 3.38 (s, 6H), 3.49-3.59 (m, 8H), 3.64-3.68 (m, 12H), 3.98 (m, 1H);

¹³ C-NMR (CDCl ₃ ): δ 59.03 (s), 69.36 (s), 70.48 (s), 70.74 (s), 71.91 (s), 72.54 (s)

(Step 2) In a 500 ml nas flask, 7.4 ml of epichlorohydrin and 22 ml of THF were mixed and 6.10 g of potassium hydroxide was isolated from Step 1 in 1, 3-bis (3, 6). The solution dissolved in 168 g of dioxa-1-heptoxy) -2-propanol was slowly added dropwise. After 2 days of stirring at room temperature, the mixture was stirred at 90 ° C for 5 hours and at 140 ° C for 1 hour. The reaction mixture was filtered, and the low boiling point component in the filtrate was distilled off under reduced pressure to obtain a liquid. The liquid was distilled off under reduced pressure (142.4 ° C./0.1 mm Hg) to recover 1, 3-bis (3, 6-dioxa-1-heptoxy) -2-propanol, followed by distillation under reduced pressure (275 ° C./0.1 mm). 2.70 g of compound c [1, 3-bis [1, 3-di (3, 6-dioxa-1-heptoxy) -2-propoxy] -2-propanol] is isolated as a colorless liquid by Hg). It was.

The NMR data of the obtained compound c are as follows.

¹ H-NMR (CDCl ₃ ): δ 3.38 (s, 12H), 3.50-3.61 (m, 24H), 3.64 (s, 16H), 3.69 (m, 6H), 3.84 (m, 1H);

¹³ C-NMR (CDCl ₃ ): δ 69.74 (s), 70.50 (t), 70.79 (d), 71.30 (d), 71.92 (s), 72.05 (s), 78.68 (s)

(Process 3) In a 300 ml volume nas flask in nitrogen atmosphere, 6.30 g of compound c was dissolved in 100 ml of dehydrated THF. 5.9 ml of 1.57 M n-butyl lithium hexane solutions were dripped here, and it stirred by heating at 60 degreeC for 12 hours. Thereafter, the solution in the flask was allowed to cool to room temperature, and 0.85 ml of 1,3-propanesultone was added thereto, followed by heating and stirring at 60 ° C for 4 days. The obtained reaction mixture was filtered, and the filtrate was concentrated by evaporation to give a crude product. This crude product was purified by gel filtration chromatography using methanol as the eluent to obtain 1.25 g of sulfonate C as a viscous yellow liquid.

The structure of the obtained sulfonate C was identified using ¹ H-NMR (CDCl ₃ ) and ¹³ C-NMR (CDCl ₃ ). The result is as follows.

¹ H-NMR (CDCl ₃ ): δ 2.04 (m, 2H), 2.96 (t, 2H), 3.39 (s, 12H), 3.52-3.73 (m, 49H);

¹³ C-NMR (CDCl ₃ ): δ 25.33 (s), 48.05 (s), 58.99 (s), 68.72 (s), 69.62 (s), 70.31 (s), 70.38 (s), 70.69 (s) , 70.84 (s), 71.82 (s), 77.91 (s), 78.25 (s)

Example 1

<Preparation of nonaqueous electrolyte amount>

1.0 mass% of sulfonate A was dissolved in 1.0 mol / L of LiPF ₆ in a mixed solvent of ethylene carbonate (EC), methyl ethyl carbonate (MEC) and diethyl carbonate (DEC) in a volume ratio of 1: 1. It added so that it may prepare the nonaqueous electrolyte solution. In addition, preparation of the nonaqueous electrolyte was performed in argon atmosphere.

<Production of Anode>

Added and mixed portion of 2.5 parts by mass of carbon black as a conductive aid to 95 parts by weight of a layered MnNi material (材) of _{Li x Ni 1/3 Mn 1} /3 Co 1/3 O 2 ( cathode active material), and to this mixture, A solution in which 2.5 parts by mass of polyvinylidene fluoride (PVDF) was dissolved in N-methyl-2-pyrrolidone (NMP) was added and mixed to prepare a positive electrode mixture-containing slurry. The positive electrode mixture-containing slurry was passed through a 70-mesh network to remove particles having large particle diameters, and then the positive electrode mixture-containing slurry was uniformly applied to both surfaces of a positive electrode current collector made of aluminum foil having a thickness of 15 μm and dried. Thereafter, the resultant was press-molded by a roll press machine to make the total thickness 129 µm and then cut, and a lead body made of aluminum was welded to obtain a strip-shaped anode.

<Production of Cathode>

Meso face carbon microbeads (MCMB) were used as the negative electrode active material. To 96 parts by mass of MCMB, a solution in which 4 parts by mass of PVDF was dissolved in NMP was added and mixed, and then NMP was added and mixed to prepare a negative electrode mixture-containing paste. The negative electrode mixture-containing paste was uniformly applied to both surfaces of a negative electrode current collector made of copper foil having a thickness of 8 μm, dried, and then compressed by a roll press to a total thickness of 141 μm, and then cut and nickel The lead body was welded to obtain a strip-shaped cathode.

<Assembly of battery>

The strip-shaped anodes and the strip-shaped cathodes are superimposed on each other via a microporous polyethylene separator (porosity: 41%) having a thickness of 20 µm, wound in a spiral shape, and then pressurized to be flat. The electrode wound body was wound into a wound structure, and the electrode wound body was fixed with an insulating tape made of polypropylene. Next, the electrode winding body is inserted into a rectangular battery case made of an aluminum alloy having an outer dimension of 4.6 mm, a width of 34 mm, and a height of 43 mm, and the lead body is welded and made of aluminum alloy. The cover plate of was welded to the open end of the battery case. Then, the said nonaqueous electrolyte was injected from the electrolyte injection hole provided in the cover plate, and it left still for 1 hour. In addition, the design electric capacity of when charging to 4.35V (4.45V in Li reference | standard) of the nonaqueous electrolyte secondary battery of a present Example was 800 mAh. In addition, the design capacitance of the nonaqueous electrolyte secondary battery of this example when charged to 4.2V (4.3V based on Li) was about 700 mAh.

Next, the battery was charged in a dry room at a dew point of −30 ° C. under the following conditions. Charging was performed for 1 hour at a constant current of 0.25 CmA (200 mA) so that the charge amount was 25% (200 mAh) of the design capacitance of the battery (800 mAh). After the charge was completed, the electrolyte injection port was sealed to keep the inside of the battery sealed. The produced battery was charged at 0.3 CmA (240 mA) until it became 4.1 V, and then stored at 60 ° C. for 12 hours. Subsequently, the battery was charged to 0.35 mA (240 mA) until it reached 4.35 V, and then charged again at a constant voltage of 4.35 V for 3 hours, discharged to 3.8 V at 1 C mA (800 mA) to evaluate the charge voltage as 4.35 V. A battery was used.

In addition, for a battery different from the battery for evaluation at the charge voltage of 4.35V, the constant current of 0.25CmA so as to be 25% of the design capacitance of the battery, except that the maximum charge voltage was changed from 4.35V to 4.2V. The battery was charged for 1 hour and then subjected to a series of operations from 1CmA to discharge to 3.8V to obtain an evaluation battery for evaluating the charge voltage as 4.2V.

The structure of the nonaqueous electrolyte secondary battery of the present Example obtained as mentioned above is shown to FIG. 1 and FIG. 1 is a perspective view showing the appearance of a nonaqueous electrolyte secondary battery of this embodiment, and FIG. 2 is a schematic cross-sectional view taken along the line I-I of FIG.

The nonaqueous electrolyte secondary battery 1 of this embodiment is a sealed space formed by a battery case 2 made of aluminum alloy and a cover plate 3 made of aluminum alloy welded to an open end of the battery case 2. The electrode winding body 9 which consists of the positive electrode 6, the negative electrode 7, and the separator 8, and the nonaqueous electrolyte (not shown) are accommodated in the inside. The cover plate 3 is provided with a terminal 5 via an insulating packing 4. The lead plate 14 is provided in the bottom part of the terminal 5, and this lead body 14 and the negative electrode 7 of the electrode winding body 9 are connected via the negative electrode lead body 12. As shown in FIG. In addition, the anode 6 of the electrode winding body 9 is connected to the cover plate 3 via the anode lead body 11. 10 is an insulator for separating the electrode winding body 9 and the battery case 2, and 13 is an insulator for separating the cover plate 3 and the lead plate 14.

Comparative Example 1

A battery for evaluation at a charge voltage of 4.35 V, except that sulfonate A was not added, a nonaqueous electrolyte was prepared in the same manner as in Example 1, and a nonaqueous electrolyte was used in the same manner as in Example 1 except that the nonaqueous electrolyte was used. A battery for evaluation at a charge voltage of 4.2 V was produced.

Comparative Example 2

A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that 1, 3-propanesultone was used instead of the sulfonate A. The procedure was the same as in Example 1 except that the non-aqueous electrolyte was used, at a charge voltage of 4.35 V. The battery for evaluation of and the battery for evaluation in 4.2 V of charging voltages were produced.

Example 2

A nonaqueous electrolyte was prepared in the same manner as in Example 1 except that sulfonate B was used instead of sulfonate A. The evaluation was carried out in the same manner as in Example 1, except that the nonaqueous electrolyte was used. A battery for evaluation at a battery and a charge voltage of 4.2 V was produced.

Example 3

A nonaqueous electrolyte was prepared in the same manner as in Example 1 except that sulfonate C was used instead of sulfonate A. The evaluation was carried out in the same manner as in Example 1 except that the nonaqueous electrolyte was used. A battery for evaluation at a battery and a charge voltage of 4.2 V was produced.

The following high temperature storage characteristic test was done about the nonaqueous electrolyte secondary batteries of Examples 1-3 and Comparative Examples 1-2. The results are shown in Table 1 and Table 2.

<High temperature storage characteristic test>

Of the batteries of Examples 1 to 3 and Comparative Examples 1 to 2, the battery for evaluation at the charge voltage of 4.35 V was charged until it became 4.35 V at 600 mA at 20 ° C., and further 3 hours at a constant voltage of 4.35 V. The battery was charged to full charge, and then discharged to 0.2V at 20 ° C. to 3 V, and then the discharge capacity before storage was measured.

Next, after charging each said battery similarly to the above, it stored in the thermostat at 80 degreeC for 1 day. After naturally cooling each battery after storage to 20 degreeC, the thickness of the battery case was measured and the expansion of the battery was calculated | required from the following formula from the comparison with the thickness of the battery case before storage. After that, all the batteries were discharged to 0.2 V at 20 ° C. up to 3 V, charged and discharged under the same conditions as before storage, and the discharge capacity after storage was measured.

Expansion of the cell (mm) = thickness of the battery after storage-thickness of the battery before storage

Among the batteries of Examples 1 to 3 and Comparative Examples 1 to 2, the battery for evaluation at the charging voltage of 4.2 V was charged until the voltage became 4.2 V at 700 mA at 20 ° C., and 2.5 at the constant voltage of 4.2 V. After further charging, the battery was fully charged and then discharged to 3V at 0.2C at 20 ° C, and the discharge capacity before storage was measured.

Next, after charging each said battery similarly to the above, it stored in the thermostat at 80 degreeC for 1 day. After naturally cooling each battery after storage to 20 degreeC, the thickness of the battery case was measured and the battery expansion was calculated | required from the calculation formula of said battery expansion from the comparison with the thickness of the battery case before storage. After that, all the batteries were discharged to 0.2 V at 20 ° C. up to 3 V, charged and discharged under the same conditions as before storage, and the discharge capacity after storage was measured.

For each of the batteries of Examples 1 to 3 and Comparative Examples 1 and 2, the capacity retention ratio was calculated by the following equation using the discharge capacity before storage and the discharge capacity after storage, and the high temperature storage characteristics were obtained from the expansion and capacity retention ratio of the battery. Was evaluated.

Capacity retention rate (%) = (discharge capacity after storage / discharge capacity before storage) × 100

additive Charge voltage (V) Battery expansion after storage (mm) Capacity retention after storage (%) Example 1 Sulfonate A 4.20 0.12 87 4.35 0.31 83 Comparative Example 1 none 4.20 0.33 81 4.35 0.68 72 Comparative Example 2 1,3-propanesultone 4.20 0.26 83 4.35 0.61 69

As is apparent from Table 1, in the nonaqueous electrolyte secondary battery of Example 1, the expansion of the battery after storage is greatly suppressed as compared with the nonaqueous electrolyte secondary batteries of Comparative Example 1 and Comparative Example 2. In addition, in the nonaqueous electrolyte secondary battery of Example 1, especially when the charging voltage is 4.35 V at high voltage, the capacity is maintained higher even after storage, compared with the nonaqueous electrolyte secondary batteries of Comparative Examples 1 and 2. have. In this respect, it can be seen that the nonaqueous electrolyte secondary battery of Example 1 is excellent in high temperature storage characteristics.

additive Charge voltage (V) Battery expansion after storage (mm) Capacity retention after storage (%) Example 2 Sulfonate B 4.20 0.10 86 4.35 0.29 84 Example 3 Sulfonate C 4.20 0.11 85 4.35 0.28 85

As is apparent from Table 2, the nonaqueous electrolyte secondary batteries of Examples 2 and 3 have the same high-temperature storage characteristics as those of the nonaqueous electrolyte secondary batteries of Example 1, and have sulfonate B and sulfonate C. It can be seen that even when used, the same effects as in the case of using sulfonate A are obtained. In particular, when the charging voltage is 4.35 V, which is a high voltage, by using sulfonate B or sulfonate C, an effect superior to that when sulfonate A is used is expected.

[Examples 4 to 11 and Comparative Example 3]

<Preparation of nonaqueous electrolyte amount>

The amount of sulfonate A was changed as shown in Table 3, and a nonaqueous electrolyte was prepared in the same manner as in Example 1 except that 2.0% by mass of vinylene carbonate was further added.

<Production of battery>

Other than the positive electrode active material was changed to a mixture of 10 parts by weight of _{LiNi 1/3 Mn 1/3} Co 1/3 O 2 , and 85 parts by mass of LiCoAl _0.005 Mg _0.005 Zr _0.002 O ₂ will, in the same manner as in Example 1 A positive electrode was produced.

Moreover, the negative electrode was produced like Example 1 except having changed the negative electrode active material into the high-crystal artificial graphite obtained by the following method.

100 parts by mass of coke powder, 40 parts by mass of tar pitch, 14 parts by mass of silicon carbide, and 20 parts by mass of coal tar are mixed at 200 ° C. in air, and then pulverized, heat treated at 1000 ° C. in a nitrogen atmosphere, and then at 3000 ° C. in a nitrogen atmosphere. Heat treatment was performed to graphitize to give artificial graphite. The surface area (d ₀₀₂ ) of the (002) plane measured by X-ray diffraction method was 0.336 nm, and the crystallite size (Lc) in the c-axis direction was 48. Nm and all pore volumes were 1 × 10 ⁻³ m ³ / kg.

A nonaqueous electrolyte secondary battery for evaluation at a charge voltage of 4.35 V was produced in the same manner as in Example 1 except that the positive electrode, the negative electrode, and each of the above nonaqueous electrolytes were used. The design capacitance (4.35V) of the nonaqueous electrolyte secondary batteries of Examples 4 to 11 and Comparative Example 3 was also 800 mAh.

The nonaqueous electrolyte secondary batteries of Examples 4 to 11 and Comparative Example 3 were subjected to the high temperature storage characteristic test in the same manner as the battery for evaluation at the charge voltage of 4.35 V of Example 1, and the battery expansion after storage was evaluated. . The results are written together in Table 3.

Amount of sulfonate A (mass%) Battery expansion after storage (mm) Example 4 0.05 0.42 Example 5 0.1 0.33 Example 6 0.5 0.28 Example 7 One 0.26 Example 8 2 0.27 Example 9 5 0.26 Example 10 10 0.25 Example 11 15 0.26 Comparative Example 3 0 0.77

As is apparent from Table 3, the nonaqueous electrolyte secondary batteries of Examples 4 to 11, like the nonaqueous electrolyte secondary batteries of Examples 1 to 3, have significantly suppressed battery expansion after storage, and have excellent high temperature storage characteristics. It can be seen that. In addition, from the result of Example 4, it turns out that the effect is exhibited more effectively by setting the amount of sulfonate in a nonaqueous electrolyte solution to 0.05 mass% or more.

Moreover, the following charge / discharge cycle test was done about the nonaqueous electrolyte secondary batteries of Examples 4-9 and Comparative Example 3. The results are shown in Table 4.

<Charge / Discharge Cycle Test>

Of the batteries of Examples 4 to 9 and Comparative Example 3, the battery other than the one provided for the above-described high temperature storage characteristic test was charged at 45 ° C until 600V became 4.35V, and the battery was charged at a constant voltage of 4.35V for 3 hours. Further, the battery was charged and fully charged, and then, the charge and discharge cycle of discharging to 3 V at 1 C 800 mAh was repeated 300 times, and the discharge capacity at the first cycle and the discharge capacity at the 200th cycle were measured. Subsequently, using the discharge capacity at the 1st cycle and the discharge capacity at the 300th cycle, the capacity retention rate was calculated by the following equation, and the charge and discharge cycle characteristics were evaluated.

Capacity retention rate (%)

= (Discharge capacity at 300th cycle / 1 discharge capacity at cycle 1) × 100

Amount of sulfonate A (mass%) Capacity retention rate (%) at 45 degrees Celsius, 300th cycle Example 4 0.05 67 Example 5 0.1 81 Example 6 0.5 85 Example 7 One 86 Example 8 2 84 Example 9 5 81 Comparative Example 3 0 22

As is apparent from Table 4, in the nonaqueous electrolyte secondary batteries of Examples 4 to 9 using the nonaqueous electrolyte containing sulfonate A, the nonaqueous electrolyte secondary of Comparative Example 3 using the nonaqueous electrolyte containing no sulfonate A Compared with a battery, it turns out that the capacity retention rate at the 300th cycle at 45 degreeC is high, and it also has the outstanding charge / discharge cycle characteristics.

Claims (13)

In a non-aqueous electrolyte containing a non-aqueous solvent, an electrolyte salt and a sulfonate, A nonaqueous electrolyte, wherein the sulfonate is a compound having a branched ether skeleton in a molecule. The method of claim 1, The sulfonate which has a branched ether frame | skeleton in a molecule | numerator has a ether bond represented by following General formula (1) in a molecule | numerator, The nonaqueous electrolyte solution characterized by the above-mentioned. [Formula 1]

[In the general formula (1), R is a C2-C4 alkylene group, R 'is a C1-C6 alkyl group; An alkylene group having 1 to 6 carbon atoms bonded to -SO ₃ M '(M' is an alkali metal) or a crown ring; Or a crown ring, m represents an integer of 1 to 10, R and R 'may each be partially or completely substituted with a fluorine atom. In the crown ring, part or all of the oxygen atoms may be substituted with sulfur atoms or nitrogen atoms.] The method according to claim 1 or 2, The sulfonate which has a branched ether frame | skeleton in a molecule | numerator has a structural part represented by following General formula (2) in a molecule | numerator, The nonaqueous electrolyte solution characterized by the above-mentioned. [Formula 2]

[In the general formula (2), M is an alkali metal, R ¹ represents a substituent having an alkylene group or an aromatic ring having 1 to 8 carbon atoms, and some or all of the hydrogen atoms may be substituted with fluorine atoms.] The method of claim 1, The sulfonate which has a branched ether skeleton in a molecule | numerator has the following general formula (3): [Formula 3]

[In the formula, R ² is a saturated hydrocarbon group having 1 to 3 carbon atoms, R <^3> and R <^4> is the same or different, and is a C2-C4 alkylene group, R <^5> and R <^6> is the same or different, and is a C1-C6 alkyl group; An alkylene group having 1 to 6 carbon atoms bonded to -SO ₃ M '(M' is an alkali metal) or a crown ring; Or a crown ring, n is an integer of 1 to 4, o and p are the same or different and represent an integer of 0 to 10, Some or all of the hydrogen atoms of R ² , R ³ , R ⁴ , R ⁵ and R ⁶ may be substituted with fluorine atoms, Some or all of the oxygen atoms of the crown ring may be substituted with sulfur atoms or nitrogen atoms. ] It is an ether bond containing compound shown by the nonaqueous electrolyte characterized by the above-mentioned. The method of claim 4, wherein The branched ether bond-containing sulfonate is represented by the following general formula (4): [Formula 4]

[In the formula, M is an alkali metal, R ¹ represents a substituent having an alkylene group or an aromatic ring, having 1 to 8 carbon atoms, R ² is a saturated hydrocarbon group having 1 to 3 carbon atoms, R <^3> and R <^4> is the same or different, and is a C2-C4 alkylene group, R <^5> and R <^6> is the same or different, and is a C1-C6 alkyl group; An alkylene group having 1 to 6 carbon atoms bonded to -SO ₃ M '(M' is an alkali metal) or a crown ring; Or a crown ring, n is an integer of 1 to 4, o and p are the same or different and represent an integer of 0 to 10, Some or all of the hydrogen atoms of R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ may be substituted with fluorine atoms,  Some or all of the oxygen atoms of the crown ring may be substituted with sulfur atoms or nitrogen atoms.] A nonaqueous electrolyte, characterized in that the compound represented by. The method of claim 4, wherein The sulfonate is represented by the following general formula (5): [Formula 5]

[Wherein q is 1 or 2 and r represents an integer of 1 to 10.] Non-aqueous electrolyte, characterized in that it has a structure shown in. The method of claim 6, Sulfonates having a branched ether skeleton in the molecule are of the following general formula (6): [Formula 6]

[In the formula, M is an alkali metal, R ¹ represents a substituent having an alkylene group or an aromatic ring having 1 to 8 carbon atoms, and part or all of the hydrogen atoms may be substituted with fluorine atoms, q is 1 or 2, r represents an integer of 1 to 10.] A nonaqueous electrolyte, characterized in that the compound represented by. The method of claim 7, wherein M in General formula (6) is Li, The nonaqueous electrolyte characterized by the above-mentioned. The method according to any one of claims 1 to 8, A content of the sulfonate salt is 0.05 to 10% by mass based on the total amount of the nonaqueous electrolyte. The method according to any one of claims 1 to 9, Electrolytic salt is a lithium salt, The nonaqueous electrolyte characterized by the above-mentioned. The method according to any one of claims 1 to 10, A nonaqueous electrolytic solution containing a cyclic carbonate and a chain carbonate as a non-aqueous solvent. The method according to any one of claims 1 to 10, A non-aqueous electrolyte solution using vinylene carbonate as a non-aqueous solvent. The nonaqueous electrolyte secondary battery which has a positive electrode, a negative electrode, a separator, and the nonaqueous electrolyte solution in any one of Claims 1-12.

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