JP4553468B2 - Non-aqueous secondary battery and charging method thereof - Google Patents

Description

【００６７】
表１に示すように、実施例１〜４の電池は、比較例１の電池に比べて、貯蔵による劣化率が小さかった。すなわち、６０℃という高温で２０日間貯蔵した場合、比較例１の電池は上記貯蔵による劣化率が４２％であったのに対し、実施例１〜４の電池は貯蔵による劣化率が１９〜２７％と抑制されていた。
【００６８】
【発明の効果】
以上説明したように、本発明では、高容量の非水二次電池において、貯蔵特性が向上させることができ、高容量で、かつ貯蔵特性が優れた非水二次電池を提供することができた。
【図面の簡単な説明】
【図１】本発明に係る非水二次電池の一例を模式的に示す断面図である。
【符号の説明】
１ 正極
２ 負極
３ セパレータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous secondary battery and a charging method thereof, and more particularly to a non-aqueous secondary battery having a high capacity and excellent storage characteristics and a charging method when using the non-aqueous secondary battery.
[0002]
[Prior art]
Non-aqueous secondary batteries typified by lithium ion secondary batteries have a large capacity, high voltage, high energy density, and high output, and therefore there is an increasing demand. However, higher capacity and higher voltage are also demanded for this non-aqueous secondary battery, and in order to meet this demand, it is necessary to increase the amount of charge power when charging the battery.
[0003]
[Problems to be solved by the invention]
Thus, it has been found that if the battery charge power is increased in order to increase the capacity and voltage, the storage characteristics deteriorate. For example, the charge power amount per unit volume of the electrode laminate is 0.59 Wh / cm. ^Three Under the above conditions, it has been found that it is very difficult to ensure storage characteristics. This is because the higher the charging power per unit volume of the electrode stack, the greater the temperature rise of the positive electrode, and the positive electrode is held at a high potential, and part of the electrolyte (liquid electrolyte) is decomposed. This is because the surface of the positive electrode deteriorates. Here, the volume of the electrode laminate is the bulk volume occupied by the laminated or wound positive electrode, negative electrode, and separator in the battery, and the latter is formed based on the winding axis. Holes are not included as a volume. In short, the total volume occupied by the positive electrode, the negative electrode, and the separator in the battery is summed up.
[0004]
Therefore, the present inventors have focused on the surface of the positive electrode and studied a method for eliminating the above-described deterioration in storage characteristics by reducing the reaction with the electrolyte solution on the positive electrode surface. That is, a 4V class active material used for the positive electrode, that is, LiCoO. ₂ , LiNiO ₂ Lithium composite oxide such as 5V grade active material, ie LiMn ₂ O _Four , LiMn _1.5 Ni _0.5 O _Four The lithium composite oxide that can have a potential of approximately 4.5 to 5.5 V is also a kind of catalyst, and in order to suppress the reaction with the electrolyte, it is necessary to reduce its catalytic ability. Therefore, the present inventors formed a protective film with high withstand voltage and high stability on the surface of the positive electrode, and suppressing the reaction between the positive electrode and the electrolytic solution with the protective film suppresses deterioration of storage characteristics. I thought it was effective.
[0005]
Therefore, as a result of various studies based on the above policy, the present inventors can form a film containing either an organic sulfur compound, a compound having a fluoroalkyl group, or an organic nitride as the protective film. It was found to be effective in suppressing the deterioration of storage characteristics.
[0006]
However, since the protective coating as described above becomes a factor that inhibits charge and discharge, in order to achieve both high capacity and excellent storage characteristics, the protective coating is made as thin as possible and has ionic conductivity. It is desirable. That is, if the protective film is made thin and has ionic conductivity, lithium ions can flow in and out smoothly during charge and discharge, and the charge and discharge reaction is not hindered. It is considered that the storage characteristics can be compatible.
[0007]
The present invention is based on the above idea, for example, the charge power amount per unit volume of the electrode laminate is 0.59 Wh / cm. ^Three The purpose of the present invention is to provide a non-aqueous secondary battery that improves storage characteristics even in a high-capacity non-aqueous secondary battery that is used under the above conditions, and has a high capacity and excellent storage characteristics. .
[0008]
[Means for Solving the Problems]
A first aspect of the present invention is a nonaqueous secondary battery having a positive electrode, a negative electrode, and a nonaqueous electrolyte using a lithium composite oxide as a positive electrode active material, wherein the carbon number is 8 in the positive electrode mixture and / or the negative electrode mixture. The concentration of the organic lithium salt containing the ester compound or ether compound having the above hydrocarbon chain and the organic lithium salt and contained in the positive electrode mixture and / or the negative electrode mixture is higher than that in the nonaqueous electrolyte. In the XPS analysis of the positive electrode surface, it has a peak based on sulfur between 168 and 170 eV, a peak based on carbon between 291 and 295 eV, and a peak based on nitrogen between 399 and 401 eV, and The required atomic ratio of each element on the surface of the positive electrode is characterized in that sulfur is 1% or more, carbon is 3% or more, and nitrogen is 0.3% or more. Water is a secondary battery.
[0009]
The second aspect of the present invention is characterized in that the non-aqueous secondary battery having the above-described configuration is charged under the condition that the positive electrode potential is 4.3 V or higher, preferably 4.4 V or higher with respect to lithium. This is a method for charging a non-aqueous secondary battery.
[0010]
In the present invention,% indicating the amount of sulfur, carbon, and nitrogen based on the XPS analysis is based on the atomic ratio, and thus is atomic%.
[0011]
And the peak based on sulfur (sulfur) between 168-170 eV as described above is a peak corresponding to an organic sulfide, and the peak based on carbon between 291-295 eV corresponds to a compound having a fluoroalkyl group. A peak based on nitrogen between 399 and 401 eV is a peak corresponding to organic nitride. When these are contained in the protective film on the surface of the positive electrode, the effect of improving the storage characteristics is exhibited.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, as a means for forming the coating film on the positive electrode surface, for example, the chemical formula LiN (Rf ¹ SO ₂ ) (Rf ² SO ₂ Imide type lithium salt containing a fluoroalkyl group represented by the formula or LiN (Rf ^Three OSO ₂ ) (Rf ^Four OSO ₂ The method of adding the imide ester type lithium salt etc. which are represented to electrolyte solution is mentioned. Where Rf ¹ , Rf ² , Rf ^Three , Rf ^Four Is a substituent containing a fluoroalkyl group, and among them, an imide ester lithium salt is particularly preferable. When a nonaqueous secondary battery containing the imide lithium salt or imide ester lithium salt as described above is charged such that the positive electrode has a high potential, a desired protective film is formed on the surface of the positive electrode. That is, when charging is performed so that the voltage becomes 4.3 V or more on the basis of lithium, a protective film having a good function in improving storage characteristics is formed. Further, as the potential is increased to 4.4 V or higher, and further to 4.5 V or higher, a protective film having a better action for improving the storage characteristics is obtained, and for 4.6 V or higher, the protective characteristics are further improved for improving the storage characteristics. A protective coating is obtained.
On the other hand, when the charge is less than 4.3 V, the protective film on the surface of the positive electrode is formed, but it is too thin or non-uniform, and it is difficult to obtain the effect of improving the storage characteristics. Here, for a battery using a carbon material such as graphite for the negative electrode, charging with a positive electrode potential of 4.3 V or higher on the basis of lithium means approximately 4.2 V or higher when converted to a voltage applied to the battery. The charge at which the positive electrode potential is 4.4 V or higher with respect to lithium corresponds to approximately 4.3 V or higher when converted to the voltage applied to the battery.
[0013]
Moreover, the thickness and composition of the protective film formed also change with the electric energy to charge. 0.59 Wh / cm per unit volume of electrode laminate ^Three When charging with the above charging power amount, a good protective film is easily formed. Furthermore, 0.6 Wh / cm per electrode laminate unit volume ^Three When charging with the above charging power amount, a better protective film is easily formed, and the electrode laminate unit volume is 0.63 Wh / cm. ^Three When the battery is charged with the above charging power amount, a better protective film is likely to be formed. In addition, this charging electric energy per unit volume of electrode laminated body is calculated | required by calculating from the integrated value of the voltage and the electric quantity at the time of charging to 0.1V to 3V and discharging to 0.1C to full charge.
[0014]
In the present invention, when the peak obtained by XPS analysis is divided into peaks and the atomic ratio of each element present on the positive electrode surface is calculated, sulfur is 1% or more, carbon is 3% or more, and nitrogen is 0.3%. Any one of the above values is required. Sulfur is preferably 2% or more, carbon is 5% or more, and nitrogen is more preferably 1% or more. However, if the ratio of each element becomes too high, there is a tendency to suppress migration of lithium ions, so sulfur is preferably 10% or less, more preferably 5% or less, and carbon is preferably 20% or less, preferably 10% or less. More preferably, nitrogen is preferably 10% or less, more preferably 2.5% or less. Moreover, it is preferable to have two or more peaks, a peak based on sulfur, a peak based on carbon, and a peak based on nitrogen, and more preferably all three peaks. In the XPS analysis, the battery was discharged at a temperature equivalent to 0.1 C, then the battery was disassembled in an inert atmosphere, the positive electrode was taken out, washed with methyl ethyl carbonate, vacuum dried for 24 hours, and a sample for XPS analysis. And The XPS analysis is performed by using an Esca lab mark2 (trade name) manufactured by VG at 12 kV-10 mA using Mg-kα rays, and performing peak division to calculate an atomic ratio of each peak. In addition, when the above analytical instruments disappear due to changes in the times, the corresponding analytical instruments and conditions may be used.
[0015]
In addition, when the protective coating formed on the positive electrode surface contains a compound having a fluoroalkyl group, the peak intensity based on the carbon after the peak splitting is defined as Ia, and other carbons (other than the fluoroalkyl group) When the sum of peak intensities based on carbon is Ic, storage characteristics can be further improved if Ia / Ic ≧ 0.2.
[0016]
Furthermore, it is preferable that the thickness of the protective film is thin enough not to inhibit charging / discharging. Further, argon sputter etching (acceleration voltage: 3 kV, ion current: 30 μA) of the positive electrode surface is performed for 2 minutes, and a slight amount enters the inside from the positive electrode surface. When the XPS analysis is performed on the portion, the peak intensity is preferably smaller than the peak intensity on the positive electrode surface before the argon sputter etching. For example, when the peak intensity on the positive electrode surface is 100, the peak intensity after the argon sputter etching is preferably 90 or less, more preferably 80 or less, and still more preferably 76 or less. However, when the film is too thin, it is difficult to obtain the effect of improving the storage characteristics. Therefore, the peak intensity is preferably 1 or more, and more preferably 10 or more.
[0017]
Further, as described above, it is more preferable that the protective film on the positive electrode surface has ionic conductivity. For that purpose, LiPF is used together with an imide lithium salt or imide ester lithium salt containing a fluoroalkyl group as an electrolyte salt. ₆ Are preferably present together. Conventionally, LiPF ₆ It is reported that the system electrolyte generates LiF, and there is a report that the surface of the positive electrode is also covered with LiF. However, such LiF cannot improve ion conductivity. In order to improve the ion conductivity of the protective coating on the positive electrode surface, LiPF is included in the protective coating on the positive electrode surface. ₆ Or it is preferable that the fluoride containing phosphorus exists. That is, it is preferable that a peak based on phosphorus exists between 135 and 138 eV in the XPS analysis, and a peak based on fluorine exists between 685 and 689 eV. And the peak based on phosphorus between 135-138 eV which exists in the surface of a positive electrode is 1.0% or more in conversion of atomic ratio, and 2% or more is more preferable. Moreover, 5% or less is preferable and 3% or less is more preferable.
[0018]
In the present invention, as an ester compound having a hydrocarbon chain having 8 or more carbon atoms to be contained in the positive electrode mixture and / or the negative electrode mixture, for example, CH _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC _Four H ₉ , CH _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC ₂ H _Five , CH _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOCH _Three An oleate having a C = C unsaturated bond, such as C ₁₇ H ₃₅ COOC ₂ H _Five Stearates such as CH _Three (CH ₂ ) ₁₄ COOC ₂ H _Five Palmitic acid esters such as CH _Three (CH ₂ ) ₁₂ COOC ₂ H _Five Myristic acid ester, C ₁₁ H _{twenty three} COOC ₂ H _Five Lauric acid esters such as C ₁₁ H _{twenty three} COO (CH ₂ CH ₂ O) _n An ester compound such as H may be mentioned. In addition, the COO portion of the carbon-based ester is replaced with SO. ₂ And SO _Three Or (RO) (R′O) (R ″ O) P═O, where (R, R ′, R ″) is a hydrocarbon chain of 1 or more carbon atoms and at least 1 One or more may include those having 8 or more carbon atoms.
[0019]
Examples of the ether compound having a hydrocarbon chain having 8 or more carbon atoms to be contained in the positive electrode mixture and / or the negative electrode mixture include, for example, C ₁₁ H _{twenty three} O (CH ₂ CH ₂ O) _n Ether such as C _n H _{2n + 1} -C ₆ H _Four -O (CH ₂ CH ₂ O) _m And ethers containing an aromatic ring such as H.
[0020]
Each of the above ester compounds and ether compounds may be used alone, or two or more of them may be used in combination in the ester compound or in the ether compound. May be. The ester compound or ether compound having a hydrocarbon chain having 8 or more carbon atoms may be contained only in either the positive electrode mixture or the negative electrode mixture, or in both the positive electrode mixture and the negative electrode mixture. You may make it contain.
[0021]
In the present invention, the ester compound or ether compound contained in the positive electrode mixture and / or the negative electrode mixture is required to have a hydrocarbon chain having 8 or more carbon atoms. This is because a certain length of the hydrocarbon chain is necessary to increase the cell reaction and facilitate the battery reaction uniformly, and a necessary degree of wettability can be ensured if it has 8 or more carbon atoms. The hydrocarbon chain preferably has 12 or more carbon atoms, more preferably has 15 or more carbon atoms, and still more preferably has 17 carbon atoms. However, when the carbon number becomes too large, it tends to be difficult to ensure the uniformity of the electrode. In addition, it is preferable to have a C═C unsaturated bond in the hydrocarbon chain because the uniformity of the electrode reaction is further improved. Particularly preferred is a case having a non-resonant type C═C unsaturated bond. Of these ester compounds or ether compounds, the preferred ones are represented by the structural formula: C _n H _m XR, wherein n is 8 or more, m is 15 or more, X is COO, SO _Three Or SO _Four And R is a fluorine-containing alkyl group or polyethylene oxide group.
[0022]
The content of the ester compound or ether compound having a hydrocarbon chain of 8 or more carbon atoms in the positive electrode mixture is 0.001% by weight with respect to the positive electrode active material (the above ester with respect to 100 parts by weight of the positive electrode active material). Compound or ether compound is preferably 0.001 part by weight) or more, more preferably 0.05% by weight or more, further preferably 0.01% by weight or more, and preferably 3% by weight or less, 0.5% by weight or less. Is more preferable, and 0.2% by weight or less is more preferable. That is, by making the content of the ester compound or ether compound having a hydrocarbon chain of 8 or more carbon atoms in the positive electrode mixture 0.001% by weight or more with respect to the positive electrode active material, the positive electrode is easily wetted with the electrolytic solution. And uniform reaction is likely to occur. Further, by setting the content of the ester compound or ether compound having a hydrocarbon chain of 8 or more carbon atoms in the positive electrode mixture to 2% by weight or less with respect to the positive electrode active material, an increase in battery impedance can be allowed. It can be suppressed within the range.
[0023]
When the ester compound or ether compound having a hydrocarbon chain having 8 or more carbon atoms is contained in the negative electrode mixture, 0.001% by weight with respect to the negative electrode active material (based on 100 parts by weight of the negative electrode active material) The above ester compound or ether compound is preferably 0.001 part by weight or more, more preferably 0.1% by weight or more, further preferably 0.4% by weight or more, and preferably 5% by weight or less, and 3% by weight or less. Is more preferable, and 1% by weight or less is more preferable. That is, by making the content of the ester compound or ether compound having a hydrocarbon chain of 8 or more carbon atoms in the negative electrode mixture 0.001% by weight or more with respect to the negative electrode active material, the negative electrode is easily wetted with the electrolytic solution. And uniform reaction is likely to occur. Further, by setting the content of the ester compound or ether compound having a hydrocarbon chain of 8 or more carbon atoms in the negative electrode mixture to 5% by weight or less with respect to the negative electrode active material, an increase in battery impedance can be allowed. It can be suppressed within the range.
[0024]
In addition, an organic lithium salt is present in advance in the positive electrode mixture or the negative electrode mixture. When the ester compound or the ether compound coexists with the organic lithium salt, it has ionic conductivity, the uniformity of the electrode reaction is further improved, and the storage characteristics are further improved. Examples of the organic lithium salt include C ₄ F ₉ SO ₃ Li, C ₈ F ₁₇ SO ₃ Li, (C ₂ F ₅ SO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) NLi, (CF ₃ SO ₂ ) ₃ CLi, C ₆ H ₅ SO ₃ Li, C ₁₇ H ₃₅ COOLi and the like are preferable because of their high thermal stability and safety, and in view of ion dissociation properties, fluorine-containing organic lithium salts are particularly preferable.
[0025]
When the organic lithium salt is contained in the positive electrode mixture, the content of the organic lithium salt is 0.01% by weight with respect to the positive electrode active material (the organic lithium salt is 0.1% with respect to 100 parts by weight of the positive electrode active material). 01% by weight) or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, more preferably 5% by weight or less, more preferably 3% by weight or less, and more preferably 1% by weight or less. Further preferred. When the organic lithium salt is contained in the negative electrode mixture, the content of the organic lithium salt is 0.01% by weight with respect to the negative electrode active material (the organic lithium salt is 100% by weight of the negative electrode active material). 0.01% by weight) or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, further preferably 5% by weight or less, more preferably 3% by weight or less, and 1% by weight. The following is more preferable.
[0026]
The content of the organic lithium salt in the positive electrode mixture or the negative electrode mixture is higher than that in the nonaqueous electrolyte. This is because ion movement in the electrode is facilitated, which is preferable in terms of battery characteristics.
[0027]
In the present invention, a non-aqueous secondary battery is configured by combining the positive electrode, the negative electrode, and the non-aqueous electrolyte (this electrolyte includes an electrolytic solution that is a liquid electrolyte).
[0028]
As the active material of the positive electrode, for example, LiCoO whose open circuit voltage during charging is 4 V or more on the basis of Li ₂ , LiMn ₂ O _Four , LiNiO ₂ Lithium composite oxide such as is used. When the active material composed of these lithium composite oxides has a potential of 4.4 V or higher on the basis of Li at the time of charging at least once, the coating film is formed and the storage characteristics of the battery are improved. In the active material, a part or most of Co, Mn, and Ni may be substituted with different elements, respectively. Al, Fe, Ge, Ti, Ta, Mg, Nb, Cr, Y By containing at least one element selected from the group consisting of Zr, Yr, and Mo, more preferable results can be obtained in improving storage characteristics. Among these elements, Ge, Ti, Ta, Nb, Yb are particularly preferable. Is preferred. Examples of such lithium composite oxides include, for example, LiCo _0.97 Al _0.03 O ₂ LiCo _0.97 Al _0.025 Ge _0.005 O ₂ , LiNi _0.7 Co _0.2 Al _0.1 O ₂ Etc. In addition, LiCoO by X-ray diffraction ₂ LiCoO showing the structure ₂ When using a system compound, the density of the positive electrode mixture layer is usually 3.2 g / cm. ^Three However, when the ester compound or ether compound having a hydrocarbon chain of 8 or more carbon atoms of the present invention is contained in the positive electrode mixture, the density of the positive electrode mixture layer is 3.3 to 3.5 g / cm. ^Three Even when the density is as high as possible, good wettability of the electrolyte can be secured, and higher capacity and improved storage characteristics can be achieved.
[0029]
The positive electrode is, for example, a positive electrode active material composed of the above lithium composite oxide or the like, and, if necessary, a conductive additive such as graphite, acetylene black, or carbon black, such as polyvinylidene fluoride, polytetrafluoroethylene, or ethylene. A binder such as propylene rubber, an ester compound or an ether compound having a hydrocarbon chain of 8 or more carbon atoms, an organic lithium salt, etc. are added as appropriate and made into a paste with a solvent (the binder is dissolved in the solvent in advance and then the positive electrode The positive electrode mixture-containing paste obtained may be applied to a positive electrode current collector made of a metal foil or the like, dried to form a positive electrode mixture layer, and pressed as necessary It is produced by adjusting the thickness. However, the method for manufacturing the positive electrode is not limited to the above-described examples, and other methods may be used.
[0030]
As the positive electrode current collector, for example, a foil containing aluminum as a main component is preferably used, and its purity is preferably 98% by weight or more and 99.9% by weight or less. In conventional lithium ion secondary batteries, an aluminum foil having a purity of 99.9% by weight or more is usually used. However, in the present invention, a metal foil of 15 μm or less is frequently used as a positive electrode current collector, so that a certain degree of strength is ensured. Therefore, the purity is preferably less than 99.9% by weight. Particularly preferred as contained elements are iron and silicon.
The iron content is preferably 0.5% by weight or more, more preferably 0.7% by weight or more, and preferably 2% by weight or less, more preferably 1.3% by weight or less. The silicon content is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and preferably 1.0% by weight or less, more preferably 0.3% by weight or less. The tensile strength of the positive electrode current collector is 150 N / mm ² Or more, preferably 180 N / mm ² The above is more preferable. Further, the breaking elongation of the positive electrode current collector is preferably 2% or more, and more preferably 3% or more.
[0031]
It is preferable that the positive electrode current collector has a larger tensile strength and elongation at break. The larger the charging power per unit volume of the electrode laminate, the larger the expansion during charging of the positive electrode. This is based on the tendency to become easy, and in order to suppress the cutting, it is appropriate that the positive electrode current collector has a higher tensile strength and elongation at break.
[0032]
The main material in the negative electrode mixture in the negative electrode may be any material that can be doped and dedoped with lithium ions. In the present invention, this is called a negative electrode active material. Examples of the negative electrode active material include natural graphite. And carbonaceous materials such as pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers and activated carbon. In addition, an alloy such as Si, Sn, or In or a compound such as an oxide or nitride that can be charged and discharged at a low voltage close to Li can be used as the negative electrode active material.
[0033]
When using a carbonaceous material for a negative electrode, what has the following characteristic is preferable. That is, the distance between the (002) planes (d ₀₀₂ ) Is preferably 0.35 nm or less, more preferably 0.345 nm or less, and still more preferably 0.34 nm or less. The crystallite size (Lc) in the c-axis direction is preferably 3 nm or more, more preferably 8 nm or more, and further preferably 25 nm or more. The average particle size is preferably 8 to 20 μm, particularly preferably 10 to 15 μm, and the purity is preferably 99.9% by weight or more. When the carbonaceous material is used, the negative electrode density is 1.45 g / cm. ^Three The above is preferable for increasing the capacity, and more preferably 1.5 g / cm. ^Three That's it. Usually, when the negative electrode mixture layer has a high density, a high capacity is easily obtained, but the negative electrode is difficult to react uniformly, and the storage characteristics tend to deteriorate. However, in the present invention, the negative electrode mixture layer is reduced to 1.5 g / cm by including an ester compound or an ether compound having a hydrocarbon chain having 8 or more carbon atoms in the negative electrode mixture. ^Three Even when the density is increased as described above, good storage characteristics can be obtained, and higher capacity and improved storage characteristics can be achieved.
[0034]
For example, a negative electrode is appropriately added with a binder, an ester compound or an ether compound having a hydrocarbon chain having 8 or more carbon atoms, a lithium salt, or the like, if necessary, into a paste using a solvent ( The binder may be dissolved in a solvent in advance and then mixed with the negative electrode active material, etc.), and the obtained negative electrode mixture-containing paste is applied to the negative electrode current collector and dried to form a negative electrode mixture layer. It is manufactured by pressing and adjusting the thickness as necessary. However, the manufacturing method of the negative electrode is not limited to the above-described examples, and other methods may be used.
[0035]
As the binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluorine rubber, styrene butadiene rubber, cellulose resin, polyacrylic acid, or the like can be used alone or as a mixture of two or more. As the negative electrode current collector, a metal foil such as a copper foil is generally used, and in particular, an electrolytic copper foil having a roughened surface is preferably used.
[0036]
As the non-aqueous electrolyte, any of a non-aqueous liquid electrolyte, a gel polymer electrolyte, and a solid electrolyte can be used. In the present invention, a liquid electrolyte called an electrolytic solution is usually used. The electrolyte is prepared by dissolving an electrolyte salt such as a lithium salt in a non-aqueous solvent mainly composed of an organic solvent. Examples of the solvent include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and propionic acid. Chain alkyl ester having chain COO- bond such as methyl, chain phosphate triester such as trimethyl phosphate, 1,2-dimethoxyethane, 1,3-dioxolane, tetrahydrofuran, 2-methyl-tetrahydrofuran, diethyl Ether or the like can be used. In addition, amine organic solvents, sulfur organic solvents such as sulfolane, and the like can also be used.
[0037]
Furthermore, as other solvent components, esters having a high dielectric constant (dielectric constant of 30 or more) are preferably used. Specific examples of such high dielectric constant esters include, for example, ethylene carbonate, propylene carbonate, butylene carbonate, gamma Examples include butyrolactone, and sulfur-based esters such as ethylene glycol sulfite can also be used. Furthermore, cyclic structure esters are preferred, and cyclic carbonates such as ethylene carbonate are particularly preferred.
[0038]
From the viewpoint of safety, the ester having a high dielectric constant is preferably less than 80% by volume, more preferably 50% by volume or less, and further preferably 30% by volume or less, in terms of discharge characteristics. 1 volume% or more is preferable.
[0039]
In preparing the electrolytic solution, examples of the electrolyte salt dissolved in the solvent include LiClO. _Four , LiPF ₆ , LiBF _Four , LiAsF ₆ , LiSbF ₆ , LiCF _Three SO _Three , LiC _Four F ₉ SO _Three , LiCF _Three CO ₂ , Li ₂ C ₂ F _Four (SO _Three ) ₂ , LiN (Rf ₁ SO ₂ ) (Rf ₂ SO ₂ [Where Rf ₁ , Rf ₂ Is a substituent containing a fluoroalkyl group], LiN (Rf _Three OSO ₂ ) (Rf _Four OSO ₂ [Where Rf _Three , Rf _Four Is a fluoroalkyl group], LiC _n F _{2n + 1} SO _Three (N ≧ 2), LiC (Rf _Five SO ₂ ) _Three , LiN (Rf ₆ OSO ₂ ) ₂ [Where Rf _Five , Rf ₆ Are fluoroalkyl groups], polymer type imidolithium salts and the like are used alone or in admixture of two or more. When these are incorporated into the protective coating on the positive electrode surface, ion conductivity can be imparted to the protective coating, particularly LiPF. ₆ Is preferable because of its great effect. The concentration of the electrolyte salt in the electrolytic solution is not particularly limited, but the concentration is preferably 0.3 mol / l or more, particularly preferably 0.4 mol / l or more, and 1.7 mol / l or less, In particular, it is preferably 1.5 mol / l or less.
[0040]
The gel polymer electrolyte corresponds to an electrolyte solution gelled by a gelling agent. For the gelation, for example, a linear polymer such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or a copolymer thereof, Polyfunctional monomers that polymerize upon irradiation with actinic rays such as ultraviolet rays and electron beams (for example, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hydroxypentaacrylate, dipentaerythritol hexaacrylate Tetrafunctional or higher acrylates and the like, and tetrafunctional or higher acrylates similar to the above acrylates). However, in the case of a monomer, the monomer itself does not gel the electrolyte solution, but a polymer obtained by polymerizing the monomer acts as a gelling agent.
[0041]
When gelling an electrolyte solution using a polyfunctional monomer as described above, if necessary, as a polymerization initiator, for example, benzoyls, benzoin alkyl ethers, benzophenones, benzoylphenylphosphine oxides, acetophenones Further, thioxanthones, anthraquinones, and the like can be used, and alkylamines, aminoesters, and the like can also be used as a sensitizer for the polymerization initiator.
[0042]
As the separator, a microporous film made of polyethylene, polypropylene, or a copolymer of ethylene and propylene is usually used. The thickness of this separator is preferably 30 μm or less, and particularly preferably 20 μm or less.
Although a thin separator contributes to an improvement in energy density, there is a situation where deterioration is likely to occur with the decomposition of the electrolytic solution at a high voltage. Decomposition is unlikely to occur, and even when a thin separator is used, deterioration is unlikely to occur, and an electrolyte shortage associated therewith is unlikely to occur. The separator preferably has an air permeability of 100 sec to 800 sec, more preferably 200 sec to 700 sec. The puncture strength is a weight until a pin having a diameter of 1 mm penetrates. The puncture strength of this separator is preferably 200 g or more, more preferably 300 g or more, and further preferably 500 g or more. Further, the thermal shrinkage of the separator at 105 ° C. is preferably small, and the thermal shrinkage rate in the width direction is preferably 5% or less, more preferably 3% or less, and further preferably 1% or less.
[0043]
For example, a battery is a nickel-plated iron laminate having a spiral structure such as a spiral electrode body manufactured by winding a separator between a positive electrode and a negative electrode as described above. It is manufactured through a process of inserting and sealing in a battery case made of stainless steel. The battery is usually provided with an explosion-proof mechanism for discharging gas generated inside the battery to a certain pressure and discharging it to the outside of the battery to prevent the battery from bursting under high pressure.
[0044]
【Example】
Next, the present invention will be described more specifically with reference to examples. However, this invention is not limited only to those Examples. In the present invention, the measuring instrument used for XPS analysis was ESCA lab mark2 (trade name) manufactured by VG, the X-ray output was 12 kV-10 mA, and the measurement was performed using Mg-Kα rays.
[0045]
Example 1
Ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 33:67, and this mixed solvent was mixed with LiPF. ₆ 1.2 mol / l and [(CF _Three ) ₂ CHOSO ₂ ] ₂ NLi is dissolved at 0.1 mol / l, and the composition is 1.2 mol / l LiPF. ₆ +0.1 mol / l [(CF _Three ) ₂ CHOSO ₂ ] ₂ An electrolyte solution represented by NLi / EC: MEC (33:67 volume ratio) was prepared. EC in the electrolytic solution is an abbreviation for ethylene carbonate, and MEC is an abbreviation for methyl ethyl carbonate.
[0046]
Apart from this, LiCo as positive electrode active material _0.97 Al _0.025 Ge _0.005 O ₂ In addition, carbon as a conductive aid, (C as an organic lithium salt ₂ F _Five SO ₂ ) ₂ NLi was added at a weight ratio of 100: 3: 0.1 and mixed, and this mixture was mixed with a solution in which polyvinylidene fluoride was previously dissolved in N-methyl-2-pyrrolidone. _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC ₂ H _Five LiCo _0.97 Al _0.025 Ge _0.005 O ₂ A positive electrode mixture-containing paste was prepared by adding 0.1% by weight to the mixture. The obtained positive electrode mixture-containing paste was passed through a 70-mesh net to remove a large one, and then the coating amount was 24.6 mg / cm on both surfaces of a positive electrode current collector made of 15 μm thick aluminum foil. ² (Partial weight of the positive electrode mixture after drying) is uniformly applied except for a part and dried to form a positive electrode mixture layer, then pressed by a roller press machine, cut, and the lead body is positive electrode current collector A belt-like positive electrode was produced by welding to the exposed portion of the film. The density of the positive electrode mixture layer of this positive electrode is 3.3 g / cm. ^Three Met. The positive electrode current collector made of aluminum foil used here contains 1% of iron and 0.15% of silicon, and the purity is 98% or more. The tensile strength of the positive electrode current collector is 185 N / mm. ² The wettability was 38 dyne / cm, and the elongation at break was 3%.
[0047]
Next, a graphite-based carbonaceous material coated with coke-based graphite at a pitch and fired at 3000 ° C. [however, the distance d between (002) planes d ₀₀₂ = 0.336 nm, C-axis direction crystallite size Lc = 100 nm or more, average particle diameter 16 μm, purity 99.5 wt% or more of carbonaceous material] and (C ₂ F _Five SO ₂ ) ₂ NLi and CH _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC ₂ H _Five Was mixed with a solution in which polyvinylidene fluoride was previously dissolved in N-methyl-2-pyrrolidone to prepare a negative electrode mixture-containing paste. Above (C ₂ F _Five SO ₂ ) ₂ The content of NLi in the negative electrode mixture is 0.1% by weight with respect to the graphite-based carbonaceous material of the negative electrode active material, and CH _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC ₂ H _Five The content of in the negative electrode mixture was 1% by weight with respect to the graphite-based carbonaceous material of the negative electrode active material. The negative electrode mixture-containing paste was passed through a 70-mesh net to remove a large one, and then the coating amount was 12.0 mg / cm on both sides of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 10 μm. ² (Partial weight of the negative electrode mixture after drying) was applied uniformly except for a part, dried to form a negative electrode mixture layer, then pressed with a roller press, and after cutting, the lead body was collected into the negative electrode A strip-shaped negative electrode was prepared by welding to the exposed portion of the electric material. The density of the negative electrode mixture part of this negative electrode is 1.5 g / cm. ^Three Met.
[0048]
The belt-like positive electrode was stacked on the belt-like negative electrode through a separator made of a microporous polyethylene film having a thickness of 20 μm and wound in a spiral shape to obtain an electrode laminate having a spiral winding structure. The separator had an air permeability of 600 sec, a puncture strength of 570 g, a porosity of 38%, a thermal shrinkage in the length direction measured at 105 ° C. of 3%, and a thermal shrinkage in the width direction of 1%. It was. The volume of this electrode laminate is 11.4 cm ^Three Met. Thereafter, the electrode laminate was filled in a bottomed cylindrical battery case having an outer diameter of 18 mm, and the positive and negative lead bodies were welded.
[0049]
Next, the electrolytic solution is poured into the battery case, and after the electrolytic solution has sufficiently penetrated into the separator and the like, sealing is performed, precharging and aging are performed, and the cylindrical non-aqueous water having a structure as shown in the schematic diagram of FIG. A secondary battery was produced.
[0050]
Here, the battery shown in FIG. 1 will be described. 1 is the positive electrode and 2 is the negative electrode. However, in FIG. 1, in order to avoid complication, the current collector used for manufacturing the positive electrode 1 and the negative electrode 2 is not illustrated. Then, the positive electrode 1 and the negative electrode 2 are spirally wound through the separator 3, and the electrode stack having a spirally wound structure is put into the battery case 5 together with the nonaqueous electrolyte 4 from the specific nonaqueous electrolyte solution. Contained.
[0051]
The battery case 5 is made of stainless steel, and an insulator 6 made of polypropylene is disposed at the bottom of the battery case 5 prior to the insertion of the electrode laminate. The sealing plate 7 is made of aluminum and has a disk shape. The sealing plate 7 is provided with a thin portion 7a at the center thereof, and serves as a pressure inlet 7b for allowing the battery internal pressure to act on the explosion-proof valve 9 around the thin portion 7a. Holes are provided. And the protrusion part 9a of the explosion-proof valve 9 is welded to the upper surface of this thin part 7a, and the welding part 11 is comprised. It should be noted that the thin-walled portion 7a provided on the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 are shown only on the cut surface for easy understanding on the drawing, and the contour behind the cut surface is The illustration is omitted. In addition, the welded portion 11 of the thin-walled portion 7a of the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 is also illustrated in an exaggerated state so as to facilitate understanding on the drawing.
[0052]
The terminal plate 8 is made of rolled steel, has a nickel plating on the surface, and has a hat shape with a peripheral edge portion having a hook shape. The terminal plate 8 is provided with a gas discharge port 8a. The explosion-proof valve 9 is made of aluminum and has a disk shape, and a central portion is provided with a protruding portion 9a having a tip portion on the power generation element side (lower side in FIG. 1) and a thin portion 9b. As described above, the lower surface of the protruding portion 9a is welded to the upper surface of the thin portion 7a of the sealing plate 7 to constitute the welded portion 11. The insulating packing 10 is made of polypropylene and has an annular shape. The insulating packing 10 is arranged at the upper part of the peripheral edge of the sealing plate 7. The explosion-proof valve 9 is arranged on the upper part, and the sealing plate 7 and the explosion-proof valve 9 are insulated. The gap between the two is sealed so that the liquid electrolyte does not leak between the two. The annular gasket 12 is made of polypropylene, the lead body 13 is made of aluminum, connects the sealing plate 7 and the positive electrode 1, an insulator 14 is disposed on the upper part of the electrode laminate, and the bottom of the negative electrode 2 and the battery case 5. Are connected by a lead body 15 made of nickel.
[0053]
In this battery, the thin-walled portion 7a of the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 are in contact with each other at the welded portion 11, the peripheral portion of the explosion-proof valve 9 and the peripheral portion of the terminal plate 8 are in contact with each other. Since the positive electrode 1 and the terminal plate 8 are connected to the sealing plate 7 by the positive lead 13, the positive electrode 1 and the terminal plate 8 are electrically connected by the lead 13, the sealing plate 7, the explosion-proof valve 9, and their welded portions 11. Connection is obtained and functions normally as an electrical circuit.
[0054]
When the battery is exposed to a high temperature and an abnormal situation occurs, gas is generated inside the battery and the internal pressure of the battery rises, the internal pressure increases, so that the central portion of the explosion-proof valve 9 moves in the internal pressure direction ( In FIG. 1, the thin-walled portion 7 a is deformed in the upper direction), and the thin-walled portion 7 a of the sealing plate integrated with the welded portion 11 is broken accordingly, or the thin-walled portion 7 a is broken, or the explosion-proof valve 9 After the welded portion 11 between the protruding portion 9a and the thin portion 7a of the sealing plate 7 is peeled off, the thin portion 9b provided on the explosion-proof valve 9 is cleaved, and gas is discharged from the gas discharge port 8a of the terminal plate 8 to the outside of the battery. The battery is designed to be discharged to prevent battery explosion.
[0055]
This battery was charged with a constant current at a current value of 0.2 A until the battery voltage reached 4.4 V, and further charged with 4.4 V at a constant voltage, and charging was terminated when 12 hours had elapsed from the start of charging. Next, the battery was discharged at 0.2 A to 3 V, and the surface state of the positive electrode of the battery after discharge was subjected to XPS analysis under the above conditions. As a result, a peak based on sulfur between 168 and 170 eV, And a nitrogen-based peak between 399 and 401 eV were detected, the atomic ratio of sulfur determined by peak splitting was 2.1%, the atomic ratio of carbon was 5.0%, and the atomic ratio of nitrogen was 1.0%. Further, when the argon sputter etching was performed, the peak intensity of sulfur decreased to 69% before the argon sputter etching, the peak intensity of carbon decreased to 71% before the argon sputter etching, and the peak intensity of nitrogen decreased to argon. It decreased to 69% before the sputter etching. Further, a peak of 137 eV based on phosphorus and a peak of 688 eV based on fluorine were detected by XPS analysis, and the atomic ratio of phosphorus determined by peak splitting was 2.0%, and the atomic ratio of fluorine was 33%. Further, the positive electrode potential during charging was approximately 4.5 V on the basis of lithium. Furthermore, when the peak intensity based on carbon after peak splitting is Ia, and the total peak intensity based on other carbons (carbons based on other than the fluoroalkyl group) is Ic, Ia / Ic = 0. 23.
[0056]
Example 2
Used in the preparation of the electrolytic solution in Example 1 [(CF _Three ) ₂ CHOSO ₂ ] ₂ NLi (CF _Three CF ₂ SO ₂ ) ₂ A non-aqueous secondary battery was produced in the same manner as in Example 1 except that it was changed to NLi.
[0057]
This battery was charged with a constant current at a current value of 0.2 A until the battery voltage reached 4.4 V, and further charged with a constant voltage of 4.4 V, and charging was terminated when 12 hours had elapsed after the start of charging. Next, the battery was discharged at 0.2 A to 3 V, and the surface state of the positive electrode of the battery after discharge was subjected to XPS analysis under the above-mentioned conditions. A peak based on nitrogen was detected at a peak and a position of 399 to 401 eV, the atomic ratio of sulfur determined by peak splitting was 1.3%, the atomic ratio of carbon was 3.1%, and the atomic ratio of nitrogen was 0.7 %Met. Furthermore, when the above argon sputter etching was performed, the peak intensity of sulfur decreased to 70% before argon sputter etching, the peak intensity of carbon decreased to 75% before argon sputter etching, and the peak intensity of nitrogen decreased to argon. It decreased to 72% before sputter etching. In addition, a XPS analysis also detected a phosphorus-based peak of 137 eV and a fluorine-based peak of 688 eV. The phosphorus atomic ratio determined by peak splitting was 2.0%, and the fluorine atomic ratio was 32%. Further, the positive electrode potential during charging was approximately 4.5 V based on lithium.
[0058]
Example 3
CH used for inclusion in the positive electrode mixture and the negative electrode mixture in Example 2 _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC ₂ H _Five C ₁₇ H ₃₅ COOC ₂ H _Five A non-aqueous secondary battery was produced in the same manner as in Example 2 except that the change was made.
[0059]
This battery was charged with a constant current at a current value of 0.2 A until the battery voltage reached 4.4 V, and further charged with 4.4 V at a constant voltage, and charging was terminated when 12 hours had elapsed from the start of charging. Next, the battery was discharged at 0.2 A to 3 V, and the surface state of the positive electrode of the battery after discharge was subjected to XPS analysis under the above conditions. As a result, a peak based on sulfur between 168 and 170 eV, And a nitrogen-based peak between 399 and 401 eV were detected, the atomic ratio of sulfur determined by peak splitting was 1.4%, the atomic ratio of carbon was 3.0%, and the atomic ratio of nitrogen was It was 0.8%. Further, when the argon sputter etching was performed, the peak intensity of sulfur decreased to 72% before the argon sputter etching, the peak intensity of carbon decreased to 77% before the argon sputter etching, and the peak intensity of nitrogen decreased to argon. It decreased to 74% before sputter etching. Further, a peak of 137 eV based on phosphorus and a peak of 688 eV based on fluorine were detected by XPS analysis, and the atomic ratio of phosphorus determined by peak splitting was 2.0%, and the atomic ratio of fluorine was 33%. Further, the positive electrode potential during charging was approximately 4.5 V on the basis of lithium.
[0060]
Example 4
CH used for inclusion in the positive electrode mixture and the negative electrode mixture in Example 2 _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC ₂ H _Five C ₁₁ H _{twenty three} COOC ₂ H _Five A non-aqueous secondary battery was produced in the same manner as in Example 2 except that the change was made.
[0061]
This battery was charged with a constant current at a current value of 0.2 A until the battery voltage reached 4.4 V, and further charged with 4.4 V at a constant voltage, and charging was terminated when 12 hours had elapsed from the start of charging. Next, the battery was discharged at 0.2 A to 3 V, and the surface state of the positive electrode of the battery after discharge was subjected to XPS analysis under the above conditions. As a result, a peak based on sulfur between 168 and 170 eV, And a nitrogen-based peak between 399 and 401 eV were detected, the atomic ratio of sulfur determined by peak splitting was 1.1%, the atomic ratio of carbon was 3.0%, and the atomic ratio of nitrogen was It was 0.8%. Furthermore, when the argon sputter etching was performed, the peak intensity of sulfur decreased to 71% before the argon sputter etching, the peak intensity of carbon decreased to 76% before the argon sputter etching, and the peak intensity of nitrogen decreased to argon. It decreased to 71% before the sputter etching. Further, a peak of 137 eV based on phosphorus and a peak of 688 eV based on fluorine were detected by XPS analysis, and the atomic ratio of phosphorus determined by peak splitting was 2.0%, and the atomic ratio of fluorine was 33%. Further, the positive electrode potential during charging was approximately 4.5 V on the basis of lithium.
[0062]
Comparative Example 1
CH in the positive electrode mixture and negative electrode mixture _Three (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOC ₂ H _Five And (C ₂ F _Five SO ₂ ) ₂ Without adding NLi, [(CF _Three ) ₂ CHOSO ₂ ] ₂ A non-aqueous secondary battery was produced in the same manner as in Example 1 except that NLi was not added.
[0063]
This battery was charged with a constant current at a current value of 0.2 A until the battery voltage reached 4.4 V, and further charged with 4.4 V at a constant voltage, and charging was terminated when 12 hours had elapsed from the start of charging. Next, the battery was discharged at 0.2 A to 3 V, and the surface state of the positive electrode of the battery after discharge was subjected to XPS analysis under the above-mentioned conditions. No based peak was detected. In addition, only 1.6% of a peak based on carbon between 291 and 295 eV was detected. Furthermore, when the argon sputter etching was performed, the peak intensity did not decrease. XPS also detected a phosphorus-based peak at 137 eV and a peak at 688 eV based on fluorine, the atomic ratio of phosphorus determined by peak splitting was 2.0%, and the atomic ratio of fluorine was 31%. Further, the positive electrode potential during charging was approximately 4.5 V on the basis of lithium. Further, Ia / Ic is 0.05 when the peak intensity based on carbon after peak splitting is Ia and the sum of peak intensities based on other carbons (carbons based on other than fluoroalkyl groups) is Ic. It was only.
[0064]
The batteries of Examples 1 to 4 and Comparative Example 1 were discharged at room temperature at 0.2 A to 3.0 V, charged at 0.2 A to 4.4 VCCCV (0.2 A constant current to 4.4 V, and then The battery was charged for 12 hours at a constant current and a constant voltage charge with a constant voltage charge of 4.4V), and then discharged to 3.0V at 0.2A to measure the discharge capacity. The discharge capacity at this time is defined as the discharge capacity before storage. Thereafter, the battery was stored at 60 ° C. for 20 days. After storage, the battery was charged with 4.4 VCCCV at 0.2 A for 12 hours, and then discharged to 3.0 V at 0.2 A to measure the discharge capacity. The discharge capacity at this time is defined as a discharge capacity after storage.
[0065]
From the pre-storage discharge capacity and the post-storage discharge capacity obtained as described above, the deterioration rate was determined by the following equation. The results are shown in Table 1 together with the amount of charging power per unit volume of the electrode laminate. In addition, the amount of charging electric power is calculated | required from the area of the charging curve when 4.4VCCCV is carried out by said 0.2A.
Degradation rate (%) = [1− (discharge capacity after storage) / (discharge capacity before storage]) × 100
[0066]
[Table 1]

[0067]
As shown in Table 1, the batteries of Examples 1 to 4 had a lower deterioration rate due to storage than the battery of Comparative Example 1. That is, when stored at a high temperature of 60 ° C. for 20 days, the battery of Comparative Example 1 had a deterioration rate of 42% due to the above storage, whereas the batteries of Examples 1 to 4 had a deterioration rate of 19 to 27 by storage. % Was suppressed.
[0068]
【The invention's effect】
As described above, according to the present invention, in a high-capacity non-aqueous secondary battery, storage characteristics can be improved, and a high-capacity non-aqueous secondary battery having excellent storage characteristics can be provided. It was.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an example of a non-aqueous secondary battery according to the present invention.
[Explanation of symbols]
1 Positive electrode
2 Negative electrode
3 Separator

Claims (9)

In a non-aqueous secondary battery having a positive electrode, a negative electrode and a non-aqueous electrolyte using a lithium composite oxide as a positive electrode active material,
During during and / or negative electrode material mixture electrode mixture, an ester compound or an ether compound having 8 or more hydrocarbon chain carbon, containing an organic lithium salt, and the content of positive electrode mixture and / or the negative electrode mixture The concentration of the organic lithium salt is higher than in the non-aqueous electrolyte,
In XPS analysis of the positive electrode surface, a peak based on sulfur during 168～170EV, has a peak based on nitrogen during peak and 399~401eV based on the carbon between the 291～295EV, and determined from the respective peak The non-aqueous secondary battery is characterized in that the atomic ratio of each element on the surface of the positive electrode is any one of sulfur 1% or more, carbon 3% or more, and nitrogen 0.3% or more. The organic lithium salt contained in the positive electrode mixture and / or the negative electrode mixture is C ₄ F ₉ SO ₃ Li, C ₈ F ₁₇ SO ₃ Li, (C ₂ F ₅ SO ₂ ) ₂ NLi, (CF ₃ SO ₂ ). _{(C 4 F 9 SO 2)} NLi, (CF 3 SO 2) 3 CLi, C 6 H 5 SO 3 Li or a non-aqueous secondary battery according to claim 1, characterized in that the _C 17 _H 35 COOLi, . The peak intensity based on the carbon after the peak splitting is Ia, and the total peak intensity based on other carbons is Ic, so that Ia / Ic ≧ 0.2. 2. The non-aqueous secondary battery according to 2. 4. The non-aqueous secondary battery according to claim 1, wherein the peak based on sulfur, carbon, or nitrogen has an intensity inside the positive electrode smaller than an intensity on the surface of the positive electrode. The XPS analysis of the positive electrode surface has a peak based on phosphorus between 135 and 138 eV, and a peak based on fluorine between 685 and 689 eV, according to claim 1. Non-aqueous secondary battery. The nonaqueous secondary battery according to claim 1, wherein the density of the positive electrode mixture layer is 3.3 g / cm ³ or more. The nonaqueous secondary battery according to claim 1, wherein the density of the negative electrode mixture layer is 1.5 g / cm ³ or more. A method for producing a non-aqueous secondary battery, comprising charging the non-aqueous secondary battery according to any one of claims 1 to 7 under a condition that a positive electrode potential is 4.3 V or more based on lithium. A charging method for a non-aqueous secondary battery, wherein the non-aqueous secondary battery according to claim 1 is charged under a condition that a positive electrode potential is 4.4 V or more based on lithium.

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